Denver Radium Superfund Site Comprehensive Report

DENVER RADIUM SUPERFUND SITE COMPREHENSIVE REPORT

October 2014

Prepared by: City and County of Denver Department of Environmental Health Environmental Quality Division 200 W 14th Avenue, Suite 310 Denver, CO 80204

Authors: Amy Laughlin, Environmental Quality Intern 2014 Ellen Kennedy, Environmental Quality Intern 2014 Lindy Chavez, Environmental Quality Administrative Support Lisa Farrell, Environmental Quality Project Manager

Funded by EPA Grant V96802801

Denver Radium Superfund Site Comprehensive Report

TABLE OF CONTENTS

Table of Contents ______i Abbreviations ______v Introduction ______1 Table of Contents ______1 Introduction ______2 Site Discovery and History ______2 EPA Superfund Process ______7 Five-Year Reviews ______8 De-listing ______9 Bibliography ______9 Endnotes ______10

Operable Unit 1 ______12 Table of Contents ______12 Background Information ______13 Remedial Investigation ______13 Remedial Objectives/Record of Decision ______14 Remedial Action ______14 Institutional Controls ______18 De-listing ______18 Bibliography ______19 Endnotes ______20

Operable Unit 2 ______21 Table of Contents ______21 Background Information ______22 Remedial Investigation ______23 Remedial Objectives/Record of Decision ______24 Explanation of Significant Differences ______25 Remedial Action ______25 Supplemental Standards ______29 Institutional Controls ______30 De-listing ______31 Bibliography ______31 Endnotes ______32

Operable Unit 3 ______35 Table of Contents ______35 Background Information ______36 Remedial Investigation ______37 Remedial Objectives/Record of Decision ______38 Explanation of Significant Differences ______38 Remedial Action ______39 Supplemental Standards ______44 Monitoring ______45 Institutional Controls ______46 De-listing ______47 Bibliography ______48 Endnotes ______49

Operable Unit 4, 5, 9B ______51 Table of Contents ______51 Background Information ______52 Remedial Investigation ______54 Remedial Objectives/Record of Decision ______54 Explanation of Significant Differences ______55 Remedial Action ______55 Supplemental Standards ______60 OU-9B (ROBCO Metals) ______62 Groundwater Monitoring ______64 Institutional Controls ______65 De-listing ______66 Bibliography ______67 Endnotes ______69

Operable Unit 6, 9A, 11 ______71 Table of Contents ______71 Background Information ______72 Remedial Investigation ______75 Remedial Objectives/Record of Decision ______78 Explanation of Significant Differences ______80 Remedial Action ______81 Excavation Activities ______87 Supplemental Standards ______88 Institutional Controls ______90 De-listing ______90 Bibliography ______91 Endnotes ______93

Operable Unit 7 ______95 Table of Contents ______95 Background Information ______96 Remedial Investigation ______97 Remedial Objectives/Record of Decision ______100 Explanation of Significant Differences ______101 Remedial Action ______102 Management Plan ______102 Radioactive Materials License ______103 Quarterly Reports ______103 Deer Trail Regional Facility ______103 Storage and Permanent Off-site Disposal Activities ______104 Denver Radium Streets ______107 2002 Denver Radium Pilot Study ______107 2003 Denver Radium Street Replacement Activity ______108 2004 Denver Radium Street Replacement Activity ______110 2005 Denver Radium Street Replacement Activity ______111 2006 Denver Radium Street Replacement Activity ______111 2007 Denver Radium Street Replacement Activity ______111 De-listing ______115 Bibliography ______116 Endnotes ______120

Operable Unit 8 ______122 Table of Contents ______122 Background Information ______123 Remedial Investigation ______125 Remedial Objectives/Record of Decision ______128 Opposition to ROD ______128 Amended to ROD ______130 Remedial Action: Original ROD ______130 Remedial Action: Amended ROD ______131 Explanation of Significant Differences ______137 Institutional Controls ______138 De-listing ______139 Bibliography ______140 Endnotes ______142

Operable Unit 10 ______143 Table of Contents ______143 Background Information ______144 Remedial Investigation ______145 Remedial Objectives/Record of Decision ______146 Remedial Action ______146 Institutional Controls ______148

iii

De-listing ______149 Bibliography ______150 Endnotes ______150

Appendices ______151 Appendix 1 - Operable Unit Maps ______152 Appendix 2 - Radium Waste Left in Place ______169 Appendix 3 - Maps of Radium Waste Left in Place ______175 Appendix 4 - Operable Unit Land Use Maps ______185 Appendix 5 - Operable Unit Parcel Maps ______198 Appendix 6 - Operable Unit 4, 5, & 9 Groundwater Monitoring Results ______212 Appendix 7 - Regulatory Limits List ______219

Abbreviations and Acronyms

µCi/mL Microcuries per Milliliter

µg/m3 Micrograms per Cubic Meter

µR/hr Microroentgen per Hour

ABHP American Board of Health Physics

AOC Area of Consolidation

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CDH Colorado Department of Health

CDPHE Colorado Department of Public Health and Environment

CDWS Colorado Drinking Water Standards

CHDTF Clean Harbors Deer Trail Facility cm Centimeter cpm Counts per Minute

DADS Denver Arapahoe Disposal Site

DIA Denver International Airport

DOT Department of Transportation dpm/100cm2 Disintegrations per Minute per 100 Square Centimeters

D&RGWRR Denver and Rio Grande Western Railroad

EP Extraction Procedure

EPA Environmental Protection Agency

ESD Explanation of Significant Differences

FS Feasibility Study

FSS Final Status Survey

FSSP Final Status Survey Plan ft2 Square Feet

GWMP Ground Water Monitoring Plan

HMWMD Hazardous Materials and Waste Management Division

HSS Hospital Shared Services

ICs Institutional Controls

IV Independent Verification

K-40 Potassium-40

MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual

MCL Maximum Contaminant Levels mg/kg Milligrams per Kilogram mrem/yr Millirems per Year

NCP National Contingency Plan (National Oil and Hazardous Substances Pollution Contingency Plan)

NPL National Priorities List of Superfund Sites

NRC Nuclear Regulatory Commission

NRI National Radium Institute

O&M Operations and Maintenance

OU Operable Unit

PAHs Polycyclic Aromatic Hydrocarbons

PCB’s Polychlorinated Biphenyls pCi/g Picocuries per Gram pCi/l Picocuries per Liter

Po-210 Polonium-210 ppm Parts per Million

PRC Pittsburgh Radium Company

RA Remedial Action

RAO Remedial Action Objective

Ra-226 Radium 226

RCC Radium Company of Colorado

RD Remedial Design

RDC Radon Decay-product Concentration

RI Remedial Investigation

RCRA Resource Conservation and Recovery Act

ROBCO Robinson Brick and Tile Company

ROC’s Radionuclides of Concern

ROD Record of Decision

ROW Right of Way

RTD Regional Transportation District

SARA Superfund Amendments and Reauthorization Act

SESSC Soils Exceeding Site Screening Criteria

SSC State Superfund Contract

SU Survey Unit

TENORM Technologically Enhanced Naturally Occurring Radioactive Materials

Th-230 Thorium-230

Th-232 Thorium-232

WL Working Level

WRC Western Radiation Consultants, Inc.

UMTRCA Uranium Mill Tailings Radiation Control Act

U-238 Uranium-38

VOCs Volatile Organic Compounds yd3 Cubic Yards (cy)

vii

Denver Radium Superfund Site Comprehensive Report

Introduction

Table of Contents: Introduction 2 Site Discovery and History 2 EPA Superfund Process 7 Five-Year Reviews 8 De-listing 9 Bibliography 9 Endnotes 10

Tables and Figures: Table 1: Uranium-238 Decay Series 4 Table 2: Denver Radium Superfund Site Properties 6 Figure 1: Superfund Remedial Process 8 2

Introduction

This document serves as a comprehensive report detailing the past activities of the Denver Radium Superfund Sites from the discovery of radium contamination in 1979 to the present in 2014. The Denver Radium Superfund Site consisted of 65 properties that were divided into 11 operable units based on location to facilitate remedial action.

In 1980, the United States Congress enacted 42 U.S.C. 9601, the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), which provides funding and enforcement authority for cleanup of inactive hazardous waste disposal sites and for responding to hazardous substance spills.1 Either the Environmental Protection Agency (EPA) or the state conducts a site inspection and uses the Hazard Ranking System to determine placement on the EPA National Priorities List (NPL). In October 1981, Denver Radium Site was placed on the Interim Priorities List, and in September 1983, the EPA placed the Denver Radium Site on the NPL, making the site eligible for cleanup under the EPA Superfund Program.2 Under the provisions of the Superfund Amendments and Reauthorization Act (SARA) of 1986, the U.S. Environmental Protection Agency was authorized to respond to a release of hazardous substance or to a significant threat of such a release into the environment.3 The applicable cleanup standards for the Denver Radium Site are outlined in 40 CFR Part 192 (EPA Standards for Remedial Action at Inactive Uranium Processing Sites). These regulations establish guidelines for the control of uranium tailings piles and the cleanup of residual radioactive materials from buildings and open lands.4

Site Discovery and History

In the early 1900s, Denver was host to the radium processing industry that flourished between 1915 and 1927. Radium was first discovered in the late 1800s and was highly valued for medicinal purposes such as cancer treatments. Other uses for radium included luminous paints, medical equipment, and various industrial purposes. Prior to 1914, radium-bearing ore was shipped from the United States to Europe for refining, but instability in Europe due to World War I prompted the United States to develop a domestic refinement process to secure the radium industry. In 1913, the United States Bureau of Mines entered into a cooperative agreement with a private corporation establishing the National Radium Institute, which successfully developed and operated a radium processing plant in Denver, Colorado. The Colorado Plateau contained rich deposits of the radium-bearing ore, carnotite, and in response, numerous radium, vanadium, and uranium processing operations opened in Denver. However, in the early 1920s, rich deposits of ore were discovered in what was then the Belgian Congo. Denver producers were unable to remain economically competitive, and the industry in Denver collapsed.5

The National Radium Institute treated carnotite ore using a nitric acid leaching process to produce radium chloride, iron vanadate, and sodium urinate. Incidental products were sodium nitrate, barium chloride, and iron-calcium precipitate. The process was thought to recover more than 90 percent of the radium, 85 percent of the uranium, and about 30 percent of vanadium. Although much of the radium, uranium, and vanadium were recovered from ore, process residues containing uranium, radium, thorium, and other radioactive materials were discarded or left on-site when the processing facilities closed.6 Some radioactive waste residues from these industrial sites were alleged to have been used at numerous 3 locations (including street and roadway construction) as fill material or aggregate in asphalt paving surfaces. 7

In 1979, EPA noticed a reference to the National Radium Institute in a 1916 United States Bureau of Mines report and subsequent field research initially revealed the presence of 31 radioactive sites in the Denver metropolitan area. In March 1979, the Radiation Control Division of the Colorado Department of Health (CDH) officially notified the affected property owners of the presence of radiological contamination on their properties and requested that no excavation or soil movement be undertaken without first contacting the Division.8 In 1981, the EPA and CDH signed a Cooperative Agreement for work on the Denver Radium Sites, and CDH was awarded $100,000 to conduct engineering assessments of the properties. In 1983, the Colorado State Legislature did not appropriate funds for the State’s continued participation in the Superfund program, and the direction of the Denver Radium Site was turned over to the EPA. A Remedial Investigation report for all the operable units was released to the public on April 30, 1986.9 Nine Record of Decisions (RODs) were written to document remedial actions at the eleven operable units. These RODs are:10

March 1986 Record of Decision OU 7 September 1986 Record of Decision OU 4 and 5 June 1987 Record of Decision OU 10 September 1987 Record of Decision OU 1 September 1987 Record of Decision OU 3 September 1987 Record of Decision OU 6, 9-A &11 September 1987 Record of Decision OU 2 December 1991 Record of Decision OU 9-B (ROBCO Metals) January 1992 Record of Decision OU 8

On May 1, 1988, the EPA and the State of Colorado entered into a State Superfund Contract (SSC) for remedial implementation at the Denver Radium NPL site.11

The radioactive waste residues contained uranium, radium, and thorium. Of prime concern is Radium- 226 (Ra-226) because of its associated radioactivity (alpha, beta, and gamma emissions of Ra-226 and its daughter isotopes), and its decay product radon gas, which constitutes the primary health risk associated with residues from processing facilities.12 Since radium has a half-life of 1,600 years, there is a long-term potential for increased public health risk from radium and its associated decay products if the contaminated materials and debris were to be misused or inadvertently spread. Also, radium is the source of radon with a half-life of 3.8 days.13 Radiological contaminants are persistent in the environment and can only be depleted through radioactive decay. 14 Table 1 displays the Uranium-238 Decay Series.

Table 1: Uranium-238 Decay Series15

Parent Symbol Half-life Decay Mode Decay Product

Uranium-238 U-238 4.46 billion years Alpha Thorium-234 Thorium-234 Th-234 24.1 days Beta, gamma Protactinium-234 Protactinium-234 Pa-234 1.17 minutes Beta, gamma Uranium-234 Uranium-234 U-234 247 thousand years Alpha Thorium-230 Thorium-230 Th-230 80 thousand years Alpha Radium-226 Radium-226 Ra-226 1,602 years Alpha Radon-222 Radon-222(a) Rn-222 3.82 days Alpha Polonium-218 Polonium-218 (b ,c) Po-218 3.05 minutes Alpha, gamma Lead-214 Lead-214(b, c) Pb-214 27 minutes Beta, gamma Bismuth-214 Bismuth-214(b, c) Bi-214 19.7 minutes Beta, gamma Polonium-214 Polonium-214(b) Po-214 0.0002 second Alpha Lead-210 Lead-210 Pb-210 22.3 years Beta Bismuth-210 Bismuth-210 Bi-210 5.01 days Beta Polonium-210 Polonium-210 Po-210 138.4 days Alpha Lead-206 Lead-206 Pb-206 Stable None None

Notes:

(a) An inert gas which behaves in accordance with kinetic molecular theory (b) Short lived radon decay product (c) These elements emit the major characteristic gamma energies of series with significant abundance and discrete energies of: 0.61, 1.12, 1.76, and 2.70 million electronvolts (MeV).

Potential pathways for exposure include:16

1. Direct gamma radiation exposure from the decay of radium and its progeny, 2. Inhalation of radon gas, the immediate decay product of radium, radon’s own short-lived decay products, and contaminated particulate 3. Ingestion of contaminated materials.

The radiological standard applying to open land, as specified in 40 CFR Part 192 Section 192.12(a), is

(a) The concentration of Radium-226 in land averaged over any area of 100 square meters shall not exceed the background level by more than: (1) 5 picocuries (pCi)/gram (g), averaged over the first 15 centimeters (cm) of soil below the surface, and (2) 15 pCi/g, averaged over 15 cm thick layers of soil more than 15 cm below the surface.

The background level used for the Denver Radium site is 2.0 pCi/g.

The radiological standard applying to occupied or habitable buildings, as specified in 40 CFR 191.12(b), is 5

(b) In any occupied or habitable buildings:

(1) The objective of remedial action shall be, and reasonable effort shall be made to achieve, an annual average radon decay product concentration (including background) not to exceed 0.02 working level (WL). In any case not to exceed 0.03 WL, and (2) The level of gamma radiation shall not exceed the background level by more than 20 micro-roentgens per hour (µR/hr).17

The background gamma radiation levels for Denver are approximately 15 µR/hr.18

The appropriate guidance for equipment and surface decontamination established by DOE Order 5480.11 sets the following limits:

1. Attached alpha particle activity of 300 disintegrations per minute per 100 square centimeters (dpm/100 cm2); and, 2. Removable alpha particle activity of 20 dpm/100cm2.

EPA Region 8 proposed the following limits for Thorium-230 (Th-230):

1. 14 pCi/g in the 0-6-inch (0 - 15cm) soil layer; and,

2. 40 pCi/g in any 6-inch thick layer between 6 inches deep and the maximum probable depth of a foundation, increasing exponentially to 500 pCi/g at a depth of 15 feet below the foundation, provided uncontaminated material overlies any contamination.

In accordance with 40 CFR Section 192.12(a), remedial actions are conducted when the concentration in radium in land, averaged over any area of 100 square meters, exceeds the background level by more than 5 pCi/g in the first 15 centimeters of soil below the surface. For depths greater than 15 centimeters below the surface, remedial actions are conducted when the radium concentration exceeds 15 pCi/g averaged over 15-centimeter-thick layers of soil.

A complete record of regulatory and background limits are listed in Appendix 7 – Regulatory Limits List.

Three properties originally identified within the Denver Radium Site were decontaminated by the owners. No additional studies were required of these properties.19 These properties were:

 Abandoned house, 590-630 South Forest Street,  University Building, 910 16th Street,  Wholesale Office Equipment Company, 1429 18th Street.

The Denver Radium Superfund Site consisted of over 65 properties listed in Table 2.

Table 2: Denver Radium Superfund Site Properties20

Property Name Address Operable Unit OU-1 B&C Metals (now Martin Shea Millworks) 1623–1625 West 12th Ave. OU-1 Erickson Monuments 1241–1245 Quivas St. OU-1 Materials Handling, Inc 1740 West 13th Ave OU-1 Rudd 1223–1229 Quivas St OU-1 City/County of Denver Alley/Driveway East of B & C Metals, between 12th Ave. and Erickson Monuments OU-2 DuWald Steel (now Atlas Metals & Iron) 1100 Umatilla Street OU-2 Rocky Mountain Research Corporation (now A1 1020–1030 Yuma Street Transmission and Nationwide Courier). OU-2 G&K Services 999 Vallejo Street OU-2 Jenkins Property 2191 West 10th Street OU-2 Staab Property 2121 West 10th Street. OU-2 Air Conditioning, Inc 1001 South Tejon Street OU-2 Burlington Northern Railroad Between 10th & 11th Avenues. OU-2 Colorado DOT—Jerome Maintenance Yard 2300 West 11th Avenue OU-2 Flame Spray, Inc 1900 West 12th Avenue OU-2 Alpha Omega Electronics 1010 Yuma Street. OU-2 Capital Management Realty (now Royal Textile) 1050 Yuma Street OU-2 Denver Water Department 1600 West 12th Avenue OU-3 Creative Illumination, Inc 1298 South Kalamath Street OU-3 Packaging Corporation of America (PCA) (now 1377 South Jason Street Caraustar Custom Packaging). OU-3 GT Car Shop/Aspen Design and Manufacturing 1235 South Jason Street OU-3 Denver right-of-way 1377 S. Jason Street OU-3 Kwan Sang Noodle Company, formerly Titan Labels 1140 West Louisiana OU-3 Various tenants 1300 South Jason Street OU-3 Central & Sierra Railroad Between W. Louisiana & W. Florida Streets OU-4 Robinson Brick and Tile Company (ROBCO) (now Home 500 South Santa Fe Drive Depot) OU-5 Denver and Rio Grande Western Railroad ROW Immediately East of OU4 OU-6 Allied Chemical and Dye Corporation (General Chemical) 1271 West Bayaud Avenue OU-6 Brannan Sand and Gravel 61st Avenue and Clear Creek

OU-6 Denver Water Department 1190 Yuma Street

OU-6 Public Service Company of Colorado South Pecos and West Arizona Avenue OU-6 Ruby Hill Park Jewell Street and S. Platte River Drive OU-6 Alley in City and County of Denver right-of-way Between Mariposa and Lipan and extends between 5th and 6th Avenue OU-6 Environmental Materials Incorporated (building has been 1155 West 5th Avenue razed) OU-6 Central and Sierra Railroad right-of-way/Centennial Tire 2301 15th Street

OU-7 9th Ave.: Ogden St. to Cheesman Park n/a 7

OU-7 11th Ave.: Josephine St. to Cheesman Park n/a

OU-7 23rd St.: California St. to Lawrence St n/a

OU-7 Corona St.: 7th Ave. to 10th Ave n/a

OU-7 Downing St.: 7th Ave. to 10th Ave n/a

OU-7 Humboldt St.: 7th Ave. to 9th Ave n/a

OU-7 Lafayette St.: 1st Ave. to 10th Ave n/a

OU-7 Marion St.: 6th Ave. to 10th Ave n/a

OU-7 York St.: 6th Ave. to 13th Ave n/a

OU-8 S.W. Shattuck Chemical Company (soil) 1805 South Bannock Street

OU-8 S.W. Shattuck Chemical Company (groundwater) 1805 South Bannock Street

OU-9A International House of Pancakes and Larry’s Trading Post 2001, 2015, and 2017 East Colfax (now Mama’s Cafe´, Herbs and Art, and Purple Haze) Avenue OU-9B Robinson Brick and Tile Company (ROBCO) Metals 500 South Santa Fe Drive (now Home Depot). OU-10 Card Corporation 1314 West Evans Avenue OU-11 Commercial Investors Realty (formerly owned by Thomas 1285–1295 South Santa Fe Drive Real Estate Corp.) (now Murphy Beds and a Starbucks).

EPA Superfund Process

The term “Superfund” denotes the trust fund created to finance cleanup options under CERCLA, the Comprehensive Environmental Response Compensation and Liability Act, passed in 1980. The Superfund trust is funded through excise taxes on petroleum feedstock chemicals, a tax on certain imported chemical derivatives, an environmental tax on corporations, appropriation from general tax revenues, and any monies recovered or collected from parties responsible for site contamination.21

The initial step of the Superfund process is to identify abandoned or uncontrolled hazardous wastes sites through site investigations. The Denver Radium Site was investigated through an assessment of existing information, data, and site inspections from 1979 to 1982.22

Once sites are identified, the EPA will conduct Preliminary Assessments and Site Inspections. The findings are then scored using a Hazards Ranking System. The sites that are identified as the most threatening to human health and the environment are placed on the National Priorities List (NPL), and long-term clean-up actions with a goal of achieving a permanent remedy are enacted.23 The Denver Radium Site was placed on the NPL in 1983.

The National Oil and Hazardous Substances Pollution Contingency Plan (NCP) contains a set of regulations that govern the procedures to implement the Superfund program. Once a site is placed on the NPL, the EPA conducts a Remedial Investigation (RI) and Feasibility Study (FS) to determine 8 the most appropriate cleanup method. A Master RI was published for the 11 Denver Radium Site Operable Units on April 30, 1986.24

Selecting the remedial action (RA) alternative consists of creating a proposed plan and publishing a Record of Decision (ROD). A remedial design (RD) plan is an engineered plan to guide implementation of the selected RA alternative. If the RA or settlement entered into differs significantly from the ROD, an explanation of significant differences (ESD) must be published, or the ROD must be amended. If RA does not result in fully unrestricted use of the site, operations and maintenance (O&M) activities must continue at the site to ensure effective implementation of the RA.25

Sites can be deleted from the NPL when no further response action is appropriate. Prior to the deletion, the state must be consulted, a notice of intent to delete must be published in the Federal Register, and public comments must be considered.26 Figure 1 illustrates the Superfund remedial process.

Figure 1: Superfund Remedial Process27

Five-Year Reviews

Five-year review reports are a statutory requirement for the Denver Radium site under CERCLA and the NCP. The purpose of the review is to determine whether remedial response actions are protective of human health and the environment and to recommend ways to attain or maintain this protection. The following Five-Year Reports have been completed:

September 1993 Five-Year Report OU4/5 September 1994 Five-Year Report OU2, OU3, OU4/5, OU6/8/11, OU7, OU8, OU9B November 1998* Five-Year Report OU1/10, OU2, OU3, OU4/5, OU6/9/11, OU7, OU8, OU9B December 1999 Five-Year Report OU8 September 2003 Five-Year Report OU1, OU2, OU3, OU4/5, OU6/9a/11, OU7, OU8, OU9B September 2008 Five-Year Report OU2, OU3, OU4/5, OU9B28 September 2013 Five-Year Report OU2, OU3, OU4, OU8 and OU9B

Due to waste left in place, five-year review reports will continue indefinitely with the next report scheduled for completion by September 2018.

*Note: The Five-Year Report for 1998 was submitted as a draft on November 20, 1998. However, due to unresolved comments between Denver and the EPA, the Five-Year Review was never finalized.29

De-Listing

On September 9, 2010, the EPA published a direct final Notice of Partial Deletion of the Denver Radium Superfund Site to delete each 11 operable units of the Denver Radium Site. The direct final Notice of Partial Deletion was published in concurrence with the State of Colorado Department of Public Health and Environment because the EPA determined that all appropriate response actions under CERCLA (excluding operation, maintenance, and five-year reviews) had been completed. On November 8, 2010, each of the 11 operable units of Denver Radium were deleted from the NPL, excluding the groundwater at Operable Unit 8, which remains on the NPL. 30

Bibliography

CH2MHill. August 1987. Feasibility Study Denver Radium Site Open Space Properties (Operable Units 6, 9, 11).

City and County of Denver. May 9, 2002. Management Plan Denver Radium Site/ Operable Unit 7- Denver Radium Streets. 10

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

EPA Region 8. Superfund Information Systems.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

GEI Consultants. March 18, 1999. Management Plan Denver Radium Site Operable Unit 8-South Bannock Street.

Jacobs Engineering Group and CH2MHill. July 1987. Feasibility Study: Denver Radium Site Operable Unit 1.

Morrison Knudsen Corporation. November 20, 1998. Denver Radium Site Five-Year Review. Denver, Colorado.

RUST Geotech, Inc. August 1992. Operable Unit 1 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

RUST Geotech, Inc. July 1994 Operable Unit 2 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

U.S. Environmental Protection Agency. September 29, 1987. Declaration for the Record of Decision: Denver Radium OU-II/11th and Umatilla.

U.S. Environmental Protection Agency. September 29, 1987. Declaration for the Record of Decision: Denver Radium OU-I/12th and Quivas, CO.

U.S. Environmental Protection Agency. February 1998. RCRA, Superfund & EPCRA Hotline Training Module: Introduction to the Superfund Response Process.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets.

CH2M Hill. July 1987. Feasibility Study. Denver Radium Site.

Endnotes

1 RUST Geotech, Inc. August 1992. Operable Unit 1 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 2 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets. 3 RUST Geotech, Inc. July 1994. Operable Unit 2 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 11

4 RUST Geotech, Inc. August 1992. 5 U.S. Environmental Protection Agency. September 29, 1987. Declaration for the Record of Decision: Denver Radium OU-II/11th and Umatilla. 6 CH. July 1987. Feasibility Study. Denver Radium Site OU-III as cited in Parsons, Charles L., R. B. Moore, S.C. Lind, and O.C. Schaefer. Extraction and Recovery of Radium, Uranium, and Vanadium from Carnotite. U.S. Bureau of Mines Bulletin 104, Government Printing Office. Washington, D.C. 1916. 7 City and County of Denver. May 9, 2002. Management Plan Denver Radium Site/ Operable Unit 7- Denver Radium Streets. 8 RUST Geotech, Inc. July 1994. 9 CH2M Hill. July 1987. 10 Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003. 11 Morrison Knudsen Corporation. November 20, 1998. Denver Radium Site Five-Year Review. Denver, Colorado. 12 RUST Geotech, Inc. July 1994. 13 CH2M Hill. July 1987. 14 U.S. Environmental Protection Agency. September 29, 1987. Declaration for the Record of Decision: Denver Radium OU-I/12th and Quivas, CO. 15 GEI Consultants. March 18, 1999. Management Plan Denver Radium Site Operable Unit 8-South Bannock Street. 16 U.S. Environmental Protection Agency. September 29, 1987. 17 RUST Geotech, Inc. July 1994. 18Jacobs Engineering Group and CH2MHill. July 1987. Feasibility Study: Denver Radium Site Operable Unit 1. 19 CH2MHill. August 1987. Feasibility Study Denver Radium Site Open Space Properties (Operable Units 6, 9, 11). 20 Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations. 21 U.S. Environmental Protection Agency. February 1998. RCRA, Superfund & EPCRA Hotline Training Module: Introduction to the Superfund Response Process. 22 CH2MHill. August 1987. 23 United States Environmental Protection Agency. February 1998. 24 CH2MHill. August 1987. 25 U.S. Environmental Protection Agency. February 1998. 26 U.S. Environmental Protection Agency. February 1998. 27 U.S. Environmental Protection Agency. February 1998. 28 EPA Region 8. Superfund Information Systems. 29 Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008. 30 Federal Register. September 9, 2010. 12

Denver Radium Superfund Site

Operable Unit 1

Table of Contents: Background Information 13 Remedial Investigation 13 Remedial Objectives/Record of Decision 14 Remedial Action 14 Institutional Controls 18 De-listing 18 Bibliography 19 Endnotes 20

Tables and Figures: Table 1: Operable Unit 1 Properties 13 Table 2: Remedial Phases of OU-1 15 Table 3: Materials Left in Place as Averaged Areas-OU-1 17 13

Background Information

Denver Radium Operable Unit One (OU-1) consisted of a 7.33 acre block bounded by Quivas Street to the east, Shoshone street to the west, West 12th Avenue to the South, and West 13th Avenue to the North. Depth to bedrock is approximately 16 feet.1

The Pittsburgh Radium Company, a division of the National Vanadium Products Company, refined ore and processed radium, vanadium, and uranium at 1201 Quivas Street until 1926.2 The Radium Ores Company, associated with Pittsburgh Radium Company, operated the facility until 1927. Approximately 120 tons of carnotite and 500 tons of vanadium were expected to be processed monthly at the facility.3 In 1930, Ute Manufacturing Chemical Laboratory occupied the 1623 W. 12th property, and beginning in 1979, B&C Metals occupied the property.4 The responsible party search could not connect the Pittsburgh Radium Company to a viable, present day company and failed to connect that the present owners had any record of being connected with the activities that caused the site to be contaminated with radioactivity.5

Denver Radium OU-1 includes the following properties:

Table 1: Operable Unit 1 Properties6

Operable Unit Property Name at Time of Address ROD OU-1 B&C Metals (now Martin Shea 1623-1625 West 12th Avenue Millworks) OU-1 Erickson Monuments 1241-1245 Quivas Street OU-1 Materials Handling Inc. 1740 West 13th Avenue OU-1 Rudd 1223-1229 Quivas Street OU-1 City and County of Denver East of B&C, between 12th Alley/Driveway Avenue and Erickson Monuments

Remedial Investigation

During the Remedial Investigation, radiological data were collected from a radiation survey conducted in 1985. Twenty areas of surface and subsurface radiological soil contamination were identified covering an area of 95,500 square feet (ft2).7 The approximate volume of contaminated soil was 10,700 cubic yards (yd3).8 The maximum depth of radium contamination was 132 inches. The volume-weighted average radium concentration of contaminated soils was 108 picocuries per gram (pCi/g) with an individual maximum radium concentration of 1,920 pCi/g. Gamma radiation measurements ranged from 2 microroentgen per hour (µR/hr) to 50 µR/hr above background with a maximum gamma radiation reading of 510 µR/hr.9 Gamma radiation readings in excess of background were found over 95,500 ft2 of the properties including areas inside several buildings.10

The estimated tonnage of contaminated material to be removed during each of the phases as stated in the Statement of Work drafted in February 1990 was as follows:

Phase A: 2,400 tons Phase B: 350 tons Phase C: 31,350 tons11

Samples of airborne particulates were taken for radon gas and radon decay products in the occupied buildings. Samples above Federal standards for radon were found in the B&C Metals building, Materials Handling building, and Rudd buildings. During a 1984 investigation, radon decay product concentration of 0.135 working level (WL) was detected in the east end of the B&C Metals building basement. The results prompted the Environmental Protection Agency (EPA) Region VIII to install a vented-plenum wall to intercept and remove radon gas that might otherwise enter the basement via diffusion from surrounding soil.12 After installation, the radon decay product concentration in the B&C Metal Products building dropped to 0.058 WL.13 The maximum radon decay product concentration measured in the Materials Handling building was 0.0512 WL and was 0.180 WL in the Rudd Investments building. Although these levels exceeded the limits allowed by the EPA standards for radon, further emergency response actions were not taken because the patterns of occupancy and the concentrations of the decay products present during periods of occupancy reduced the likelihood of significant long-term exposure.14

A groundwater monitoring well was installed on the northern portion of OU-1 between the Materials Handling Building and the Rudd Investments building to investigate a possible plume in the groundwater that may have been contaminated with organic chemicals associated with the adjacent properties. The results showed that the plume did not extend into OU-1.15

Remedial Objectives/Record of Decision

In the September 29, 1987 Record of Decision (ROD), EPA’s preferred remedial action alternative for OU-1 was off-site permanent excavation and disposal. At the time of the ROD, the State of Colorado did not have a permanent disposal site. Since the remedial action alternative could not be implemented, onsite temporary containment (capping) was selected. However, onsite temporary containment was abandoned when a permanent disposal facility operated by Envirocare in Tooele County, Utah became available before excavation began.16

Remedial Action

Remediation activities were conducted in three phases (A, B, and C) between October 1, 1989 and July 18, 1991. The quantity of material removed was 32,665 tons (approximately 27,220 yd3).17

EPA and the State of Colorado entered into a State Superfund Contract (SSC) on May 1, 1988 and the contract was later amended on August 4, 1989. The following tasks were agreed upon for OU-1: 15

 All site preparation, including provision for access, security, decontamination facilities, utilities, equipment staging areas and other items needed to prepare for and carry out the cleanup for OU- 1.  Excavation of radium-contaminated soils to meet target residual levels established in the EPA standard, 40 CFR 192, and the remediation of contaminated soil buried beneath buildings included in OU-1.  Backfilling and grading of excavated areas, reconstruction of remediated buildings, decontamination and demobilization of equipment and decommissioning facilities used in the cleanup; and  Preparation of all documentation necessary to verify site cleanup, demonstrate compliance with historic preservation requirements, and propose NPL deletion.  Loading and transportation of contaminated material to a suitable permanent off-site disposal facility, decontamination and demobilization of equipment, and decommissioning of facilities used for loading and transportation.

Under the terms of the SSC, the State of Colorado agreed to pay 10 percent of the cost of the response action.

Radiological contamination at OU-1 was excavated in six-inch lifts in order to minimize the amount of clean material that was removed with the waste. After a lift was removed, the excavation was surveyed to determine whether it was necessary to remove another lift.

The design/construction contractor was CN Geotech, and Chem Nuclear Environmental Systems, Inc. was the transportation and disposal contractor. A total of 301 gondolas and 201 truck-mounted, bi-modal containers were loaded and shipped during the period between October 1989 and April 1991.18

Table 2: Remedial Phases of OU-1

Phase A Conducted October 1, 1989 through December 31, 1989 Properties: Materials Handling Building (south and west portion) Phase B Conducted February 1, 1990 through August 31, 1990 Properties: Materials Handling Building (northwest portion) Phase C Conducted June 1, 1990 through May 30, 1991 Properties: B&C Metals Erickson Monuments Rudd Investments

Phase A remediation activities included areas to the south and west of the Materials Handling building. EPA’s contractor excavated 1,950 tons of radium contamination from the exterior area west of the Materials Handling building. The property owner entered into a separate contract with the excavation 16 contractor to decontaminate the area south of the west building in which 565 tons of radium contamination was removed. EPA provided technical oversight.

The radiological contamination was loaded into 20-ton, truck-mounted containers. EPA’s contractor performed a final verification survey to ensure that the clean-up standards had been met. Upon completion of verification, the owner contracted construction for a new warehouse in the area south of the existing building. The owner’s intention was to vacate the existing warehouse upon completion of the new one.

The transportation and disposal contractor installed an in-rail scale to enable rail cars to be loaded near capacity and eliminated the problem of overloading. The contractor placed a gantry immediately outside the controlled area enabling two workers to secure the 10 by 52 ft, 1,200 pound hardcover on the loaded gondolas in less than 10 minutes per container.

Phase B remediation activities included the Materials Handling building in the northwest portion of the unit. Following removal of contaminated soil, a new building was constructed. 19 During the construction of the new Materials and Handling building, remedial action began in the office and showroom. EPA’s contractor then installed airtight barriers to isolate the controlled areas from the rest of the building, removed the office partitions, and jack hammered the floor to expose the contaminated sub grade. A total of 564 tons were removed via small conveyors and skip loaders and put into dump trucks driven to the east side of the building so the waste could be loaded into gondolas.

A total of 2,070 tons of radium contaminated soils and debris had been removed from the warehouse by the time it was ready for the final verification survey.

Phase C remediation activities included the exterior area west of B&C Metals. A septic tank was removed that serviced the B&C metals building. Two highly deteriorated objects, suspected of being transformers, were discovered inside the tank. The transformers were placed in sealed 55-gallon drums and turned over to the property owner for proper disposal.

A total of 20,000 tons of soil and debris were removed from the open area in the center of the site. Two 10,000-gallon underground storage tanks were removed during the remediation of the open area in the center of the site. When the tanks were removed, the exteriors of the tanks were discovered to be radiologically contaminated. A spray curtain was erected so that the tanks could be decontaminated using a high-pressure spray of water mixed with fine sand. A total of 797 tons of contamination were removed from the interior of the east building of Rudd Investment building, and 232 tons were excavated and shipped to the disposal facility during the decontamination of the B&C Metals building.

During the reconstruction of the B&C Metals building, remedial action continued in the area adjacent to the rail spur and on the Erickson Monuments property. Small deposits of radium-contaminated soils were removed from the parking area on the east side of the building. This contamination continued through the landscaped area on the south side of the building. A 20 x 40 ft. addition to the building located directly adjacent to the landscaped area was demolished to remove the last deposit of contaminated soil at OU-1. This addition was later reconstructed, and the landscaped area was replanted. 17

During the final stage of remedial action, the rail spur was pulled up, the area was verified as clean, and the alley was reconstructed.20

Several areas within OU-1 required additional assessment or the use of area averaging calculations because of considerations that precluded cost-effective and safe removal of contaminated material. Table 2 shows the details of the materials left in place as averaged areas.

Table 3: Materials Left in Place as Averaged Areas-OU-121

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-1- Figure 2, Area 60 6.8 pCi/g Adjacent to and Materials A/Phase B beneath the south Handling foundation footer of Building the lower office level

OU-1- Figure 2, Area 27 5.6 pCi/g Adjacent to and Materials B/Phase B beneath the southern Handling foundation in the Building lower office level

OU-1- Figure 2, Area 105 7.7pCi/g West side of the Materials E/Phase B foundation footing Handling under the showroom Building OU-1- Figure 2, Area 193.5 12.0 pCi/g Beneath restrooms Erickson A/Phase C and front office Monuments OU-1- Rudd Figure 2, Area 430.5 15.0 pCi/g Under attached shed Investments B/Phase C north of Rudd Investments

OU-1- B&C Figure 2, Area 305/370 9.3 pCi/g/ 8.0 Underneath B&C Metals D1/D2/Phase C pCi/g building building OU-1- B&C Figure 2, Area 18 10.0 pCi/g Beneath footer in Metals E/Phase C B&C metals building OU-1- B&C Figure 2, Area 119 8.8 pCi/g Beneath the hallway Metals F/Phase C at the north end of building B&C metals

OU-1- Figure 2, Area 462 16.4 pCi/g East side of the Materials G/Phase C Materials Handling Handling Warehouse 18

Excavation of the contaminated material was performed using front-end loaders directed by field personnel. Radiation was measured through hand-held detectors as well as through soil sample analyses.

Contaminated materials were loaded directly onto railcars at the site by a Geotech subcontractor and were transported in covered gondola cars to the disposal facility in Tooele County, Utah. Each gondola was filled with material and then inspected to ensure no spillage of the waste material occurred. The wastes were labeled “Denver Radium Superfund Waste.” Composite samples were taken from each rail car during load-out and were analyzed to ensure that the material was acceptable under the requirements of the disposal facility. Approximately 99 tons of material exempt under the Bevill Exclusion Amendment of the Resource Conservation and Recovery Act (RCRA) was removed from the site and transported to the disposal facility.22

One low-volume air particulate sampler, two atmospheric radon detectors, and one gamma thermoluminescent dosimeter were placed at each measurement location. There was no significant difference between data sets for the baseline period, the construction period, and the post-remedial action period.23 All atmospheric radon concentrations measured during the construction period (July 1991- October 1991) were below the regulatory standard of 3.0 picocuries per liter (pCi/l) above natural background.24

The total cost of remedial action at OU 1 from October 1989 to April 1991 was $9,561,306.00.25

Institutional Controls

OU-1 was fully remediated, and no operation and maintenance was required for this remedy. The properties are available for unlimited use and unrestricted access.26

A site visit was performed in August 2003 as part of the Five-Year review report, and all properties in OU-1 remained designated for commercial and industrial use. EPA will not conduct a further five-year review of the remedial action because the condition of the site allows for unrestricted use and unrestricted exposure.27

While a five-year review is not required at OU-1, the Superfund Final Closeout report requires, the locations of the waste left in place (such as averaged areas), to be tracked with the established GIS database for proper disposal during potential future development.28

De-listing

A Final Close-Out Report was signed on September 27, 2006.29 On November 8, 2010 the direct final partial deletion of the Denver Radium Superfund Site from the National Priorities List of Superfund Sites (NPL) became final, and OU-1 of Denver Radium Superfund Site was deleted from the NPL.

On January 18, 2011, Colorado Department of Public Health and Environment (CDPHE) conducted a review of the environmental data collected at the 1245 Quivas Street property and confirmed that the property was deleted from the NPL on November 5, 2010 allowing for unlimited use and unrestricted 19 exposure at this property. The investigation confirmed one small deposit (193.5 ft2) of residually contaminated soils remaining on the property beneath the restrooms and the front office at the Erickson Monuments property. It was determined under the Uranium Mill Tailings Act (UMTRA) guidelines for area averaging and the limited access that this small deposit did not pose a threat to occupants of this building. All areas in the outer parking lot and associated open grounds are free of any radium contamination and do not require further capping or covering.30

On May 19, 2011, CDPHE conducted a review of the environmental data collected at the 1223-1229 Quivas Street properties and confirmed that the properties were deleted from the NLP on November 5, 2010 allowing for unlimited use and unrestricted exposure at this property. The review of clean-up and remedial work by the EPA indicated that there is no evidence that contamination was released into the environment from residual contamination underneath the attached shed that would pose an unacceptable risk to human health and environment.31

Bibliography

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

Colorado Department of Public Health and Environment. January 18, 2011. RE: 1245 Quivas Street, Formerly Denver Radium OU-1, Denver, Denver County, Colorado.

Colorado Department of Public Health and Environment. May 19, 2011. RE: 1223-1229 Quivas Street, Formerly Denver Radium OU-1, Denver, Denver County, Colorado.

Federal Register. September 9, 2010 . Vol. 75, No. 174/ Rules and Regulations.

Geotech, Inc. April 1992. Environmental Air Sampling at Denver Radium Operable Unit 1: Off-Site Measurements Obtained during the Construction Period from July 1991 to October 1991.

Jacobs Engineering Group and CH2MHill. July 1987. Feasibility Study: Denver Radium Site Operable Unit 1.

RUST Geotech, Inc. August 1992. Operable Unit 1 Closeout Report for the U.S. Environmental Protection Agency.

Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium.

U. S. Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium/12th & Quivas, CO.

U.S. Environmental Protection Agency. December 10, 1991. Remedial Action Completion Report. 20

Endnotes

1 RUST Geotech, Inc. August 1992. Operable Unit 1 Closeout Report for the U.S. Environmental Protection Agency. 2 United States Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium/12th & Quivas, CO 3 RUST Geotech, Inc. August 1992. 4 Jacobs Engineering Group and CH2MHill. July 1987. Feasibility Study: Denver Radium Site Operable Unit 1. 5 United States Environmental Protection Agency. September 29, 1987. 6 United States Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium 7 Jacobs Engineering Group and CH2MHill. July 1987. 8 United States Environmental Protection Agency. September 25, 2006 9 Jacobs Engineering Group and CH2MHill. July 1987. 10 United States Environmental Protection Agency. September 29, 1987. 11 Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988 12 Jacobs Engineering Group and CH2MHill. July 1987. 13 United States Environmental Protection Agency. September 29, 1987. 14 United States Environmental Protection Agency. September 29, 1987. 15 United States Environmental Protection Agency. September 25, 2006 16 United States Environmental Protection Agency. September 25, 2006 17 RUST Geotech, Inc. August 1992. 18 U.S. Environmental Protection Agency. December 10, 1991. Remedial Action Completion Report. 19 Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003. 20 U.S. Environmental Protection Agency. December 10, 1991. 21 RUST Geotech, Inc. August 1992. 22 RUST Geotech, Inc. August 1992. 23 RUST Geotech, Inc. August 1992. 24 Geotech, Inc. April 1992. Environmental Air Sampling at Denver Radium Operable Unit 1: Off-Site Measurements Obtained during the Construction Period from July 1991 to October 1991. 25 U.S. Environmental Protection Agency. December 10, 1991. 26 RUST Geotech, Inc. August 1992. 27 Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008. 28 United States Environmental Protection Agency. September 25, 2006 29 Colorado Department of Public Health and Environment. September 30, 2008. 30 Colorado Department of Public Health and Environment. January 18, 2011. RE: 1245 Quivas Street, Formerly Denver Radium OU-1, Denver, Denver County, Colorado. 31 Colorado Department of Public Health and Environment. May 19, 2011. RE: 1223-1229 Quivas Street, Formerly Denver Radium OU-1, Denver, Denver County, Colorado. 21

Denver Radium Superfund Site

Operable Unit 2

Table of Contents:

Background Information 22 Remedial Investigation 23 Remedial Objectives/Record of Decision 24 Explanation of Significant Differences 25 Remedial Action 25 Supplemental Standards 29 Institutional Controls 30 De-listing 31 Bibliography 31 Endnotes 32

Tables and Figures:

Table 1: Operable Unit 2 Properties 23 Table 2: Remedial Phases of OU-2 25 Table 3: Materials Left in Place as Averaged Areas-OU-2 28

Background Information

Denver Radium Operable Unit Two (OU-2) consisted of a 24 acre area bounded on the east by the Burlington Northern Railroad, on the north by West 11th Street, on the west by Yuma Street, and on the south by West 10th Avenue. Interstate-25 is located approximately 75 feet west of the western portion of the site.1

The site is underlain by alluvium and the Denver formation sandstone. The depth to groundwater is greater than 10 feet and depth to bedrock is approximately 10 to 30 feet.2 Two ditches crossed OU-2 in the late 1800s that were later abandoned and gradually filled with rubble and possibly radium mill tailings.3 The topography is fairly level with a slight westerly slope, and almost all of the property is covered with reinforced concrete pavement. Approximately 65 percent of the 11th and Umatilla properties are located within the 100-year designated floodplain, and the entire OU is located within the 500-year floodplain. Two major water conduits, Denver Water Department Conduit 12 and Conduit 18, run east-west across the center of the site. Both of the conduits are approximately five feet deep and carry treated water for residential and commercial use. Another water supply conduit runs north-south on the eastern boundary of the site. There are approximately 0.3 miles of railroad track on the site.4

It is believed that the contamination in OU-2 was a result of the Schlesinger Radium Company which began operations in 1914 at the location of 1100 Umatilla, formerly the Du-Wald Steel Corporation. In 1917, Schlesinger Radium Company became the Radium Company of Colorado (RCC) and reportedly processed between 1,000 and 1,200 tons of radium ore per year. The RCC ceased operations in 1924. Complex Ores Recovery Company, which had financial ties with the RCC, occupied the site until 1928, and it is unknown whether Complex Ores Recovery Company processed radium ore.5

The City of Denver owned the site from 1938 to 1948 and operated a municipal landfill on the southern portion of the site. Household waste and large quantities of broken battery casings were placed in the landfill. Residual lead from the casings mixed with radium contaminated soils created approximately 400 tons of commingled contamination. In the late 1950s and early 1960s, an operation to reclaim the lead from the batteries was conducted in the northeast quadrant of the site (the area surrounding the East Storage building). This operation resulted in commingled contamination as well as lead-only contaminated soils.6

In 1955, Rocky Mountain Research Corporation received a license from the U.S. Atomic Energy Commission to possess uranium ore. Residual radioactive contamination on the Rocky Mountain Research Corporation property may be associated with operations related to that license.7 The responsible party search could not connect the Schlesinger Radium Company to a viable, present day company and failed to show that the present owners had any record of having been connected with the activities that caused the site to be contaminated with radioactivity.8

In 1982, contaminated soil was excavated from 1100 Umatilla Street (formerly Du-Wald Steel) during construction of an addition. The material was placed in the southwest corner and then re-graded. During remodeling of one of the buildings at 1100 Umatilla, subfloor venting measures were taken and a vapor barrier was installed to prevent radon from entering the building. Colorado Department of Public Health and Environment and the EPA jointly performed oversight of this work.9 23

Denver Radium OU-2 includes the following properties:

Table 1: Operable Unit 2 Properties10

Operable Unit Property Name at Time of Address ROD OU-2 DuWald Steel (now Atlas Metals 1100 Umatilla Street and Iron) OU-2 Rocky Mountain Research 1020-1030 Yuma Street Corporation (now A1 Transmission and Nationwide Courier) OU-2 G&K Services 999 Vallejo Street OU-2 Jenkins Property 2191 West 10th Street OU-2 Staab Property 2121 West 10th Street OU-2 Air Conditioning, Inc. 1001 South Tejon Street OU-2 Colorado DOT- Jerome 2300 West 11th Avenue Maintenance Yard OU-2 Burlington Northern Railroad Between 10th and 11th Avenues OU-2 Flame Spray, Inc. 1900 West 12th Avenue OU-2 Alpha Omega Electronics 1010 Yuma Street OU-2 Capital Management Realty (now 1050 Yuma Street Royal Textile) OU-2 Denver Water 1600 West 12th Avenue OU-2 20-foot-wide concrete alley East of Yuma Street and adjacent to the west property line of Jerome Maintenance Yard

Remedial Investigation

In 1986, the initial RI identified approximately 15,400 cubic yards (yd3) of contaminated soil, and contamination was found in both interior and exterior areas. Concentrations of Ra-226 were found as high as 931 picocuries per gram (pCi/g).11 The average radium concentration in the contaminated soils on the 11th and Umatilla properties ranged from 3.2 pCi/g to 931 pCi/g. Depths ranged from less than 6 inches to 144 inches, and the maximum depth of radium contamination found on the properties was 120 inches.12

The estimated volume of contaminated material to be removed during each of the phases as stated in the Statement of Work was as follows:

Phase A: 3,000 cubic yards Phase B: 5,275 cubic yards Phase C: 91,500 cubic yards13

A portion of the alley east of Yuma Street indicated Ra-226 concentrations of 119.1 pCi/g in the 6-to 12- inch layer on the west side of the alley and 54.3 pCi/g in the 12- to 18-inch layer on the east side.14 A field survey evaluation conducted on January 16, 2004 located and assessed the delineation of subsurface 24

Ra-226 impacts suspected to be located beneath public rights-of-way. The data collected beneath the alleyway indicated Ra-226 detections above 20 microroentgen per hour (µR/hr) action level within an area approximately 20-foot by 32-foot.15

Gamma radiation readings in excess of background were found over 170,436 square feet of the properties including in several buildings. Average gamma radiation measurements ranged from 0.6 µR/hr to 94 µR/hr above background. The maximum gamma radiation measurement was 611 µR/hr above background, and the average and maximum gamma radiation measurements in this area were 12 µR/hr and 17 µR/hr, respectively.16

Radon decay-product concentration (RDC) was found to exist at 1100 Umatilla and the basement of the building located at 1050 Yuma Street. During a 1985 EPA investigation, a maximum radon decay- product concentration of 0.030 working level (WL) was detected in the southwest and northwest areas of the 1100 Umatilla office building. Concentrations up to 0.304 WL were detected in the northeast area of the basement of the 1050 Yuma Street building. These levels exceeded the limit of 0.02 WL allowed by EPA for radon. No emergency response action was taken due to the patterns of occupancy, and the concentrations of radon decay-products reduced the likelihood of significant long-term exposure.17 Also, it was thought that removal of radium contamination adjacent to the office building would reduce radon levels inside the office space. In 1992, the buildings were re-tested for radon and the EPA standard was still exceeded. A subfloor ventilation system was installed at 1100 Umatilla in the Du-Wald Steel Corporation’s office/scale house.18 After the system was installed and activated, the RDC measurements averaged 0.004 WL, and gamma exposure rates ranged from 20 to 39 µR/hr with a background exposure rate of 18 µR/hr.19

Groundwater in the shallow alluvial aquifer on-site contained elevated concentrations of uranium, gross alpha, and gross beta. In addition, elevated concentrations of lead in the soil were found at 1100 Umatilla. The RI collected 71 soil samples from 36 bore holes surrounding the East Storage building. Out of 71 soil samples collected, 31 had total concentrations of lead greater than 1,000 parts per million (ppm) with the highest concentration at 36,600 ppm. A UNC Geotech report completed in December 1990, estimated the volume of lead-only contaminated soil (lead greater than 1,000 mg/kg) to be 531yd3. The total volume of commingled contamination was estimated at 609 yd3. The lead component of this commingled waste was thought to be associated with the broken battery casings that were disposed of at the municipal landfill on the property.20

Remedial Objectives/Record of Decision

The selected remedy in the September 29, 1987 Record of Decision (ROD) entailed:

1. Excavating radium contaminated soil from open areas and from under the buildings; 2. Placing the excavated material into a temporary land storage facility to be constructed on the OU- 2 properties; 3. Maintaining the 6-inch thick concrete cap that already covers a portion of the contaminated material on the northeast part of 1100 Umatilla Street; and 4. Removing the estimated 15,400 yd3 of radiologically contaminated material from on-site temporary storage and shipping to a permanent disposal facility when such a facility became available.21 25

However, the plans for on-site temporary land storage and on-site temporary containment at OU-2 were abandoned when a permanent disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah became available in 1988.22, 23

In September 1993, the EPA issued an Explanation of Significant Differences (ESD) to address on-site conditions that became apparent after the ROD was signed. The following differences were revealed:

1. Further assessment identified the volume of radium-only contaminated soil was almost four times greater (60,000 yd3) than the amount given in the original ROD (15,400 yd3). 2. No excavation of radiologically contaminated soils occurred in the following areas: a. Under structures at 1100 Umatilla b. Near the underground power line c. Within a four foot buffer zone around water level d. On the Burlington Northern Railroad (BNRR)right-of-way 3. Onsite temporary storage of excavated contaminated material was not required since a permanent off-site facility became available before excavation began. 4. The ROD did not address soils containing commingled contaminants. The EPA assembled a treatment plant at 1100 Umatilla to solidify 2,800 tons of commingled contamination in a cement matrix before being shipped to the Envirocare facility.24

Also, the EPA prepared a memorandum to modify the ROD to include the alley property east of Yuma Street and to include the alley in the Institutional Controls plan.

Remedial Action

Remedial activities were conducted in four phases beginning in August 1990 and concluding in August 1993.* Approximately 92,798†,‡ tons of contaminated soils were disposed of off-site. Of this total, 14,211 tons of soil were commingled radium/RCRA Characteristics for lead.25

Table 2: Remedial Phases of OU-226

Phase A Conducted August 1990 through October 1990 Properties: 1900 West 12th Avenue 1010 Yuma Street 1050 Yuma Street 2300 West 11th Avenue

1,358.54 tons of contaminated material removed

* The Closeout Report (July 1994) states that remedial activities (Phase A-D) concluded in September 1992. The Remedial Action Completion Report states that remedial activities (Phase A-D) concluded in December 1992. † The September 2008 Five-Year Review Report states that 92,731 tons of contaminated soil was excavated at OU-2. ‡ The Closeout Report (July 1994) states that 97,572 tons of contaminated material were disposed of off-site. 26

Phase B Conducted January 1990 through September 1990 Properties: 2121 West 10th Street 2191 West 10th Street

3,622.26 tons of contaminated material removed

Phase C Conducted September 1991 through December 1991 Properties: 1100 Umatilla Street

14,211.22 tons of contaminated material removed

Phase D Conducted January 1992 through November 1992 (Transportation and Disposal) Properties: 1100 Umatilla Street Between 10th and 11th Avenues

73,605.52 tons of contaminated material removed

Separate Action: Conducted in 1993 Properties: 1100 Umatilla Street property

933 tons of contaminated material removed

Radiologic contamination at OU-2 was excavated in six inch lifts in order to minimize the amount of “clean material” that was removed with the waste. After a lift was removed, the excavation was surveyed to determine whether it was necessary to remove another lift.27

The cleanup work at OU-2 was performed by two contractors: a design/construction contractor (UNC Geotech) and a transportation/disposal contractor (Chem Nuclear Environmental Systems Inc.). A total of 993 gondolas and 308 truck mounted, bimodal containers were loaded and shipped during the period from January 1990 to November 1992.28

During Phase A, a total of 17.63 tons of contaminated material was excavated and shipped from Flame Spray, Inc. Verification samples were taken and a final inspection was completed on October 19, 1990. A total of 190.79 tons of contaminated material was excavated and shipped from Alpha Omega Electronics. Verification samples were taken and a final inspection was completed on October 29, 1990. A total of 68.14 of contaminated material was excavated and shipped from the Capital Management Realty Building. Verification and a final inspection were completed on October 19, 1990. A total of 1,081.98 tons were excavated and shipped from the Jerome Park Maintenance Shop. Verification and a final inspection were completed on October 19, 1990. 27

During Phase B, a total of 2,103.93 tons of contaminated material was excavated from the interior of the Staab Building. A combined total of 1,518.33 tons of contaminated material was excavated from the exterior of the Staab and Jenkins Building was excavated and shipped.

During Phase C, both radiologic and heavy metal (lead) contamination were found on the 1100 Umatilla Street property, and a total of 14,211 tons of radiologic and commingled material was excavated and shipped off-site. The non-radium contaminated soil, broken battery casings, and commingled material were isolated and stabilized by solidification. The radium and lead contaminated soil, and broken battery casings totaled approximately 4,774 tons. The treated soil was sampled and analyzed in accordance with the Toxicity Characteristic Leaching Procedure (TCLP) and determined to be nonhazardous.29

The 1100 Umatilla Street property contained 80 percent of the contaminated material found under OU-2. In areas where contamination exceeded 7 to 8 feet in depths, the contamination extended into the water table. As practice, remedial excavation was halted above the depth of the water table.

Phase D included the remaining portions of 1100 Umatilla Street, BNRR, Staab, Jenkins, G & K Services, and Air Conditioning, Inc. properties. A total of 293.88 tons of contaminated material were excavated and shipped from the BNRR right-of-way. Verification and a final inspection were completed on October 5, 1992.30

In a separate removal action conducted in 1993, a total of 933 tons of lead-contaminated soils from the 1100 Umatilla Street property (Du Wald Steel) were treated and shipped to the Weld County Landfill in Erie, Colorado.31

The contaminated material was excavated with front-end loaders and track hoes while field personnel monitored the excavated area for remaining contamination with hand-held radiation detectors. Soil sample analysis results were used as well as in some cases, remote deposit capture (RDC) measurements and hand-held detector surveys to ensure that all contamination was removed and achieved conformance with applicable standards.32

Seven deposits of contamination required area averaging because of conditions that precluded safe or cost-effective removal of contaminated material. Table 2 shows the details of the materials left in place as averaged areas.

Table 3: Materials Left in Place as Averaged Areas-OU233

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-2- 2300 West Area AA 120 9.6 pCi/g Beneath the floor slab of 11th Avenue the north shop building OU-2- 2300 West Area AB 70 8.9 pCi/g Around a telephone line 11th Avenue inside the east property boundary OU-2- 2300 West Area AD 75 16.3 pCi/g Around a telephone line 11th Avenue inside the east property boundary OU-2- 2191 West Area DT 210 14.2 pCi/g Northeast corner of the 10th Street 2191 West 10th Street building building OU-2- 2121 West Area ED 470 13.5 pCi/g East side of the 2121 West 10th Street 10th Street building building OU-2 – 1001 Area EE 187 8.8 pCi/g North side of the 1001 South Tejon South Tejon Street Street Property property OU-2- 999 Vallejo Area EF 408 12.5 pCi/g North side of the 999 Street Property Vallejo Street property

Contaminated materials were transported by rail in covered gondola cars to the permanent off-site facility in Utah. The disposal contractor loaded the material directly onto the cars at the site, and each gondola car was sealed, surveyed, and decontaminated, as necessary. The cars were used only for the transportation of wastes from the Denver Radium Site, and the loaded cars were labeled “Denver Radium Superfund Waste.” A composite sample was taken from each railcar during loading and analyzed to ensure that the material conformed to the acceptance requirements of the disposal facility.34

The solidified nonhazardous radium and lead contaminated soil and the lead contaminated mill tailings (a RCRA-exempt waste) were shipped to the Envirocare of Utah, Inc. facility for disposal. The treated lead contaminated soil that was not also contaminated with radium was disposed of in a municipal landfill. The vinyl asbestos tile removed from the Staab building (approximately 165 pounds [10 cubic feet]) was disposed of at an approved disposal facility. The soil removed from 1600 West 12th Avenue property satisfied the EPA-approved criteria for off-site backfill material and was used as subsurface fill at OU-1.§, 35

Off-site air-quality monitoring data were collected before, during, and after remedial action. One low- volume air particulate sampler, two atmospheric radon detectors, and one gamma thermoluminescent dosimeter were placed at each of five measurement locations. The results indicated that there were no significant differences between the data sets collected over the entire period.36

The 2006 Closeout Report states that the backfill material and was used as subsurface fill at Operable Unit 2. 29

Air particulate measurements were collected using Model LV1 low-volume air particulate samplers manufactured by F&J Specialty Products, Inc. Each sampler was contained in an environmentally protected shelter and was connected to a dedicated electrical power outlet. The samplers were operated continuously for seven days at a nominal rate of five liters per minute. The filters were analyzed by the Geotech analytical laboratory for natural uranium, Th-230, Ra-226, and polonium-210 (Po-210). All airborne radionuclide concentrations measured during the reporting period were below the applicable regulatory standard (10 CFR 20).37

Atmospheric radon measurements were collected using Terradex outdoor Type F Track Etch® radon detectors. Two detectors were exposed in an environmentally protected enclosure approximately 1 meter above ground level, and each detector consisted of an alpha-sensitive film protected by a membrane filter permeable only to radon. All atmospheric radon concentrations measured during the reporting period were below the regulatory standard of 3.0 picocuries per liter (pCi/l) above background.38

Direct external gamma exposure measurements were collected using TMA/Eberline thermoanalytical environmental dosimeters. Each dosimeter was exposed approximately 1 meter above ground level at each sample location and was submitted to TMA/Eberline Thermo Analytical, Inc. for analysis. All gamma exposures measured during the reporting period were below the limit of 100 millirems per year (mrem/yr) above background. The background exposure rates for the Denver area range from 130 to 175 mrem/yr (CH2MHill, 1986).39

Supplemental Standards

The EPA criteria for determining that conditions in a given instance warrant a deviation from usual remedial action procedures, are known as supplemental standards for remedial action under the regulations set forth in the National Contingency Plan, 40 CFR Section 192.22. A supplemental standards report for OU-2 was completed in June 1995 to document the location and rationale for leaving 11,060 cubic yards of radiological contaminated soil in place on the BNRR property, alley east of Yuma Street (remediated in 2005 under the Denver Radium Streets (OU-7) program), and 1100 Umatilla Street.

The locations where contaminated soils were left in place include:

1. The Shredder complex located on the 1100 Umatilla Street; 2. Locations within two feet of groundwater 3. Locations around utilities 4. Beneath and near the scale, scale house, warehouse, east storage building, and the southeast warehouse on the 1100 Umatilla Street 5. Locations on the BNRR property; 6. A portion of the alley east of Yuma street; and , 7. Five verification areas where Th-230 contamination exists.40

The conditions at OU-2 meet criterion (c) of 40 CFR Section 192.21 which addresses the unreasonably high cost of remedial action relative to the long-term benefits. Areas where waste material was left in place with Supplemental Standards in accordance with 40 CFR Part 192, Subpart C, require the maintenance of Institutional Controls (ICs) and do not allow for unrestricted use and unrestricted exposure. IC plans must require that property owners use best efforts to maintain current zoning and 30

prevent changes to land use. However, the Supplemental Standards Report found that no unacceptable health risk will exist if the contaminated soil was allowed to remain undisturbed at the 1100 Umatilla Street.

A review of the supplemental standards regarding the radiological contaminated soil left in place at 1100 Umatilla Street was conducted in May 2005 by the CDPHE Hazardous Materials and Waste Management Division. The report focused on the health risk scenario for unprotected construction workers, because this scenario offers levels of radiation dosage not expected to be exceeded the foreseeable future. Aligning with the Supplemental Standards calculation that total annual radiation dose for the unprotected construction worker to be approximately 993 mrem/yr, the report concludes that remediation at the 1100 Umatilla Street is needed, but can be safely deferred as long as adequate institutional controls are implemented. However, the report noted that an annual dose rate of 993 mrem is in excess of the 1) applicable radiation dose rate limit in CRR 1007 Part 4.14** of 100 mrem/yr 2) the applicable radiological criterion for release to unrestricted use in CRR 1007 Part 4.61.2 of 25 mrem/yr, 3) the applicable radiological criteris for release to restricted use in CRR 1007 Part D 4.61.3.2 and 4.61.3.3 of 100 mrem/yr, 4) 500 mrem/yr in the case that institutional controls might fail. Therefore, strict ICs are required to sufficiently be protective of health and safety.41

Institutional Controls A Materials Management and Health and Safety Plan for 1100 Umatilla Street was drafted in 2003 and revised in 2004 and in 2005. The Management Health and Safety Plan applies whenever plans intend to breach the concrete cap at 1100 Umatilla and expose any underlying soils which may contain radium- contaminated materials. The plan will be implemented by any owner, lessee, or licensee of 1100 Umatilla Street, and outlines procedures for the handling of materials contaminated with Ra-226 and its progeny exceeding EPA standards as well as health and safety monitoring procedures and document retention.42

Signed June 25, 2006, Atlas Umatilla, LLC, present-day owners of 1100 Umatilla Street granted an Environmental Covenant to the Hazardous Materials and Waste Management Division of the Colorado Department of Public Health and Environment. The purpose of the covenant is to ensure continued protection of human health and the environment by implementing the ICs required for OU-2. Use restrictions include adherence to the Materials Management and Health and Safety Plan, inspection of the concrete cap at least twice each calendar year and performing sufficient maintenance of the concrete cap, not using the groundwater beneath the Property for any purpose, and monitoring and maintaining indoor air quality within fully enclosed buildings of the property.43 Other primary activities associated with the Operations and Maintenance plan are to monitor the ICs and inspect and maintain a radon venting system in the office/scale house building on the property.44

ICs also are in effect at the BNRR property (between 10th and 11th Avenues) and 1100 Umatilla Street property by a City and County of Denver Municipal Ordinance (Denver Ordinance No. 668-13). The Denver Revised Municipal Code, Chapter 48 [Solid Waste], Article VIII [Disposal fees]45 creates a special zoning for these properties and prohibits disposal of the materials in Denver without paying a fee.

** Colorado Rules and Regulations Pertaining to Radiation Control Part 4, Standards for Protection Against Radiation 31

The City will charge $5.10/cubic foot of radioactive waste or radium contaminated material to any person disposing or implementing a remedial control of the above material, unless the disposal is incidental to installation, maintenance, repair, improvement, or replacement of utilities, streets, sidewalks, or alleys in public rights-of-way.46

De-listing

During remediation, all properties existing in OU-2 were developed and being utilized for commercial and light industrial use. A site visit by CDPHE in August 2003 confirmed that all properties within OU-2 were being used for the same purposes. A site visit in July 2008 confirmed that OU-2 continued to be used as a metal recycling facility. Additional utilities and another structure were added to the property with no negative impact on the protectiveness of the remedy.47

In October 2005, a statistical analysis was performed in conjunction with the decommissioning that followed remediation activities at OU-2. The statistical analysis was conducted in accordance with procedures presented in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), and facilitated the de-listing of OU-2 from the National Priorities List (NPL). MARSSIM is release criterion developed by the EPA to provide guidance for federal agencies, states, site owners, contractors, and other private entities to demonstrate site compliance with a radiation dose or risk-based regulation. Based on sampling results and the statistical analysis, the street segments on 1100 Umatilla Street met the release criterion and were suitable for release and delisting from the NPL.48 On November 4, 2005, Denver submitted an application to the EPA to request de-listing of street segments/alleys in OU-2 and 6 from the NPL to allow unrestricted routine and emergency street maintenance and repair. The subject street segment/alley in OU-2 was 1100 Umatilla Street adjacent to Atlas Metals. Clean confirmation soil samples were collected and analyzed for Ra-226 by Eberline Services in Oak Ridge, Tennessee using gamma spectroscopy. 49

A Final Close-Out Report was signed on September 27, 2006.50 In a letter dated January 2, 2008, the State of Colorado concurred with the EPA’s intent state in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.51

On November 8, 2010 the direct final partial deletion of the Denver Radium Superfund Site from the NPL became final, and all of OU-2 of the Denver Radium Superfund Site was deleted from the NPL.

Bibliography

Atlas Umatilla, LLC. July 2005. Environmental Covenant: Atlas Umatilla, LLC and State of Colorado.

City and County of Denver. Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES.

City and County of Denver. October 2005. MARSSIM Evaluation Report: 11th Avenue and Umatilla- OU-2, 15th Street Bridge-OU-VI, Denver Radium Sites. Denver, Colorado.

City and County of Denver. November 4, 2005. Application for De-listing of OU-II and OU-VI Denver Radium Site Denver, Colorado.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003. 33

Colorado Department of Public Health and Environment. May 2005. Review of Denver Radium Superfund Site Supplemental Standards Report, Operable Unit 2, DuWald Steel Property- 11th Avenue & Umatilla, Denver.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

Engineering Management and Support. March 6, 2005. Materials Management and Health and Safety Plan: 1100 Umatilla Street, Denver, Colorado.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

RUST Geotech Inc. July 1994. Operable Unit 2- Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

State of Colorado. January 2, 2008. Notice of Deletion.

Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988.

U.S. Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium/11th & Umatilla, CO.

U.S. Environmental Protection Agency. June 14, 1993. Denver Radium Site Operable Unit 2: Remedial Action Completion Report.

U.S. Environmental Protection Agency. September 17, 1993. EPA Superfund Explanation of Significant Difference for the Record of Decision: Operable Unit 2.

U.S. Environmental Protection Agency. June 1995. Supplemental Standards Report: Operable Unit II, Du-Wald Steel Property, Denver Radium Superfund Site.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium.

January 30, 2004. Memorandum Re: Preliminary Field Survey Evaluation Denver Radium Streets- Operable Units II and VI.

Endnotes

1 United States Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets 2 United States Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium/11th & Umatilla, CO. 3 RUST Geotech Inc. July 1994. Operable Unit 2- Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 34

4 Engineering Management and Support. March 6, 2005. Materials Management and Health and Safety Plan: 1100 Umatilla Street, Denver, Colorado. 5 RUST Geotech Inc. July 1994. 6 United States Environmental Protection Agency. September 17, 1993. EPA Superfund Explanation of Significant Difference for the Record of Decision: Operable Unit 2. 7 RUST Geotech Inc. July 1994. 8 United States Environmental Protection Agency. September 29, 1987. 9 United States Environmental Protection Agency. September 29, 1987. 10 United States Environmental Protection Agency. September 25, 2006. 11 RUST Geotech Inc. July 1994. 12 United States Environmental Protection Agency. September 29, 1987. 13 Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988 14 RUST Geotech Inc. July 1994. 15 January 30, 2004. Memorandum Re: Preliminary Field Survey Evaluation Denver Radium Streets- Operable Units II and VI. 16 United States Environmental Protection Agency. September 29, 1987. 17 United States Environmental Protection Agency. September 29, 1987. 18 United States Environmental Protection Agency. September 17, 1993 19 RUST Geotech Inc. July 1994. 20 United States Environmental Protection Agency. September 17, 1993 21 United States Environmental Protection Agency. September 17, 1993 22 United States Environmental Protection Agency. September 17, 1993 23 RUST Geotech Inc. July 1994. 24 United States Environmental Protection Agency. September 17, 1993 25 United States Environmental Protection Agency. June 14, 1993. Denver Radium Site Operable Unit 2: Remedial Action Completion Report. 26 United States Environmental Protection Agency. September 25, 2006 27 United States Environmental Protection Agency. June 14, 1993. 28 United States Environmental Protection Agency. June 14, 1993. 29 United States Environmental Protection Agency. September 25, 2006 30 United States Environmental Protection Agency. June 14, 1993. United States Environmental Protection Agency. June 14, 1993. 31 Colorado Department of Public Health and Environment. September 30, 2003. Five-Year Review Denver Radium Site. 32 RUST Geotech Inc. July 1994. 33 RUST Geotech Inc. July 1994 34 RUST Geotech Inc. July 1994 35 RUST Geotech Inc. July 1994 36 RUST Geotech Inc. July 1994 37 RUST Geotech Inc. July 1994 38 RUST Geotech Inc. July 1994 39 RUST Geotech Inc. July 1994 40 United States Environmental Protection Agency. June 1995. Supplemental Standards Report: Operable Unit II, Du-Wald Steel Property, Denver Radium Superfund Site. 41 Colorado Department of Public Health and Environment. May 2005. Review of Denver Radium Superfund Site Supplemental Standards Report, Operable Unit 2, DuWald Steel Property- 11th Avenue & Umatilla, Denver. 42 Engineering Management and Support. March 6, 2005. Materials Management and Health and Safety Plan. 43Atlas Umatilla, LLC. July 2005. Environmental Covenant: Atlas Umatilla, LLC and State of Colorado. 44 Colorado Department of Public Health and Environment. September 30, 2008. Five-Year Review Denver Radium Site. 45 Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII.-DISPOSAL FEES. 46 Colorado Department of Public Health and Environment. September 30, 2008. 47 Colorado Department of Public Health and Environment. September 30, 2008. 35

48 City and County of Denver. October 2005. MARSSIM Evaluation Report: 11th Avenue and Umatilla-OU-2, 15th Street Bridge-OU-VI, Denver Radium Sites. Denver, Colorado. 49 City and County of Denver. November 4, 2005. Application for De-listing of OU-II and OU-VI Denver Radium Site Denver, Colorado. 50 Colorado Department of Public Health and Environment. September 30, 2008. 51 State of Colorado. January 2, 2008. RE: Notice of Deletion 35

Denver Radium Superfund Site

Operable Unit 3 1000 West Louisiana Properties

Table of Contents:

Background Information 36 Remedial Investigation 37 Remedial Objectives/Record of Decision 38 Explanation of Significant Differences 38 Remedial Action 39 Supplemental Standards 44 Monitoring 45 Institutional Controls 46 De-listing 47 Bibliography 48 Endnotes 49

Tables and Figures:

Table 1: Operable Unit 3 Properties 36 Table 2: Remedial Phases of OU-3 40 Table 3: Materials Left in Place as Averaged Areas-OU-3 42

Background Information

Denver Radium Operable Unit Three (OU-3), also known as the 1000 West Louisiana Properties, consisted of a 15 acre area bounded on the east by Jason Street, on the north by Mississippi Avenue, on the west by Lipan Street, and on the south by Platte River Drive.1

Depth to bedrock is approximately 16 feet, and depth to groundwater is approximately 15 feet. OU-3 is not within the South Platte River 100-year flood plain,2 and the properties are underlain by alluvium and the Denver formation sandstone. Several buried municipal utilities exist within the OU-3 property boundaries, and a small drainage ditch, which runs through an uncontaminated area, drains east to the South Platte River. 3 There is one storm sewer on the southeastern portion of the 1377 South Jason Street, several sanitary sewers on the 1298 South Kalamath Street, and gas and water mains that run under the streets surrounding the properties.4

The vacant lot owned by Packaging Corporation of America may have been the site of a smelter that operated in the late 1800s, and was later converted into a radium-processing facility.5 From 1918 to 1921, the Chemical Products Company, located at 1000 West Louisiana Street, operated a milling and separated vanadium and radium from uranium ores for the National Radium Institute.6,7 The majority of the buildings associated with radium processing were demolished prior to 1970 except for the brick building at 1298 Kalamath Street. (Creative Illumination, Inc.). This building was demolished during Denver Radium Superfund Site remediation activities.

The responsible party search failed to trace the Chemical Products Company to a viable, present-day entity. However, the Chemical Products Company may have been associated with Ludlum Steel Company, and sources also indicate a possible association with the Ore Products Company.8

Table 1: Operable Unit 3 Properties9

Operable Unit Property Name at Time of Address ROD OU-3 Creative Illumination, Inc. 1298 South Kalamath Street OU-3 Packaging Corporation of 1377 South Jason Street America (PCA) now Caraustar Custom Packaging OU-3 Central and Sierra Railroad right Between West Louisiana and of way West Florida Streets OU-3 GT Car Shop/Aspen Design and 1235 South Jason Street Manufacturing OU-3 Kwan Sang Noodle Company, 1140 West Louisiana formerly Titan Labels OU-3 Various Tenants 1300 South Jason Street OU-3 Central and Sierra Railroad Between W. Louisiana & W. Florida Streets

Remedial Investigation

In May 1982, a consulting firm performed a radiological engineering assessment performed at the vacant lot located at 1000 West Louisiana Avenue. Surface gamma radiation surveys were performed, subsurface exploratory holes were bored and gamma logged, and soil samples were collected to determine radium-226 (Ra-226) concentrations and the presence of other radioactive elements of interest. The results concluded that 95 percent of the open ground area exceeded the Environmental Protection Agency (EPA) Interim Standards for radium contamination levels.10

In April 1986, the Remedial Investigation (RI) identified approximately 15,738 cubic yards (yds3) of contaminated soil covering an area of 200,400 square ft (ft2) at OU-3.1 The health-based standard for concentration criterion for surface soil is 5 pCi/g of radium-226. The maximum depth of radium contamination was 96 inches. Radium measurements ranged from 476.3 pCi/g to 2,120 pCi/g for multiple measurements at several locations and ranged from 2 pCi/g to 2,120 pCi/g for individual maximum measurements. The volume weighted average radium concentration of contaminated soils was 114.2 pCi/g.11

The estimated tonnage of contaminated material to be removed during each of the phases as stated in the Statement of Work was as follows:

Phase A: 3,660 tons Phase B: 59,070 tons Phase C: South Jason Street12

A gamma radiation grid scan survey performed at 1298 South Kalamath Street building identified elevated gamma radiation throughout the basement and first and second floors. The average and maximum gamma radiation measurement for the first floor was 154 microroentgens per hour (µR/hr) and 2,189 µR/hr, respectively. The average and maximum gamma radiation measurement for the basement was 73 µR/hr and 779 µR/hr, respectively.13

Grab samples were obtained to measure radon decay products in the 1298 South Kalamath Street building with the highest sample being 0.17 working levels (WL), taken from the basement. The average value for the building was 0.043 WL, (The Federal standard is 0.02 WL) exceeding radon standards on all three floors of the 1298 South Kalamath Street building. 14 Emergency response action was not taken because the patterns of occupancy and the concentrations of radon decay products present during periods of occupancy reduced the likelihood of significant long-term exposure.15

Samples of site groundwater were not collected and analyzed during the initial RI because the radium processing wastes at the site presented minimal potential for radionuclides leaching. Radium is a heavy, radioactive metal that combines chemically with other elements to form various compounds. Most of these compounds are relatively insoluble and as a result, not very mobile within the environment. Therefore, the initial Feasibility Study (FS) concluded that only limited migration of the radium contamination is expected via surface water or groundwater.16

1 The Denver Radium Site Feasibility Study reported 15,659 yds3 of contaminated soil and 101 yds3 of contaminated debris (plaster board, wood, and brick). 38

The 1000 W. Louisiana and 1377 South Jason Street were investigated for non-radiological contamination, and soil samples were analyzed for Extraction Procedure (EP) toxicity metals, volatile and semi-volatile organic compounds. None of the samples exceeded the EP toxicity standards per 40 CFR 261.24.17

Remedial Objectives/Record of Decision

The selected remedy in the September 29, 1987 Record of Decision (ROD) included:

1. Cleaning up the 1298 South Kalamath Street property and storing approximately 200 cubic yards of contaminated material in a temporary storage facility at OU-10; 2. Excavating contaminated soil on the 1000 West Louisiana Avenue properties and consolidating and capping the material on the vacant lot at 1000 West Louisiana Ave.; 3. Maintaining the cap at 1000 West Louisiana Ave. and the temporary storage facility at OU-10 until a facility suitable for the permanent disposal of Denver Radium Site wastes became available; and, 4. Removing the contaminated material from both locations to the permanent disposal facility.

However, the plans for on-site temporary storage and on-site temporary containment at OU-10 were abandoned when a permanent disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah became available in 1988.18

In November 1993, the EPA issued an Explanation of Significant Differences (ESD) to address on-site conditions that became apparent after the ROD was signed. The following differences were revealed:

1. Temporary storage of the contaminated material was not required; 2. The area of contamination and associated volume of contaminated soils increased; 3. The contaminated portion of the 1298 South Kalamath Street building was demolished, rather than decontaminated and restored; and, 4. Relatively small volumes of Ra-226 contamination were left in place.

The ESD further recommended that the OU-10 Management Plan developed by Denver be amended to include the affected portions of South Jason Street and South Platte River Drive.19

In a letter dated June 14, 1991, Denver recommended that the radium contaminated material under South Jason Street should be excavated and disposed of off-site, consistent with the ROD for OU-3. Denver argued that the no action alternative selected by the EPA transferred remedial costs to Denver’s taxpayers.20

The EPA responded to Denver’s concerns regarding the radium left in place at South Jason Street concluding:

1. There was little or no potential for buildings to be constructed over the radium deposits, and therefore, no potential for radon gas to accumulate to harmful levels in such structures; 2. Since the contamination lied beneath hard asphalt surface, there was limited potential for radio- particulates to be released to the atmosphere where they could be inhaled or ingested. Even during street or utility maintenance activities, normal dust suppression techniques are adequate to minimize any radiation hazard; 39

3. A utility worker performing maintenance in South Jason Street would have to work in the street more than 960 hours in a one-year period to exceed the level of radiation exposure that is considered to be safe by the International Commission on Radiologic Protection; and 4. The radium contamination was not adversely affecting groundwater in the area and was unlikely to do so in the future because of the relatively small quantity of radioactive material present and its generally insoluble nature.21

Remedial Action

Remedial activities were conducted in four phases beginning in August 1989 and concluding in September 1991. The total quantity of contaminated material removed was 63,403 tons2 (approximately 53,000 yds3).3

EPA and the State of Colorado entered into a State Superfund Contract (SSC) on May 1, 1988 and later amended on August 4, 1989. The following tasks were agreed for OU-3:

 All site preparation, including provision for access, security, decontamination facilities, utilities, equipment staging areas, and other items needed to prepare for and carry out the cleanup for OU- 3.  Excavation of radium-contaminated soils to meet target residual levels established in the EPA standard of 40 CFR 192 (residual levels exceeding 15 pCi/g of radium-226 are considered hazardous), and the remediation of contaminated soil buried beneath buildings included in OU-3.  Backfilling and grading of excavated areas, reconstruction of remediated buildings, decontamination and demobilization of equipment and decommissioning facilities used in the cleanup;  Preparation of all documentation necessary to verify site cleanup, demonstrate compliance with historic preservation requirements, and propose NPL deletion; and  Loading and transportation of contaminated material to a suitable permanent off-site disposal facility, decontamination and demobilization of equipment, and decommissioning of facilities used for loading and transportation.

With regard to cost share, the SSC states that the State must provide a 10% match on OU-3 due to the absence of a responsible party.

Radiological contamination at OU-3 was excavated in six-inch lifts in order to minimize the amount of clean material that was removed with the waste. After a lift was removed, the excavation was surveyed to determine whether it was necessary to remove another lift.

The design/construction contractor was CN Geotech, and Chem Nuclear Environmental Systems, Inc was the transportation and disposal contractor. A total of 621 gondolas and 3 truck-mounted, bi-modal containers were loaded and shipped in the period between October 1989 and September 1991.22

2 The September 2008 Five-Year Review states that 63,672 tons of contaminated material was removed from OU-3. 3 The Denver Radium Site Operable Unit III Remedial Action Completion Report states 63,335 tons removed. 40

Table 2: Remedial Phases of OU-323

Phase A Conducted August 21, 1989 through January 19, 1990 Properties: 1298 South Kalamath Street 3,567 tons of contaminated material removed Phase B Conducted June 27, 1990 through January 19, 1991 Properties: 1377 South Jason Street, southern portion of Property South Platte River Drive - Areas adjacent to street which had elevated radium at the surface 1000 West Louisiana Avenue 32,389 tons of contaminated material removed Phase C Conducted June 1, 1991 through September 30, 1991 Properties: Between 10th & 11th Avenues 1140 West Louisiana South Jason Street between West Louisiana Ave and South Platte River Drive South Platte River Drive adjacent to PCA and Harbert Casting Properties 1328 South Jason St (Schooley Property) 1346 South Jason Street (Schooley property/American Fire Fighters) 1380 S. Jason (Harbert Casting) 1336, 1338, 1340 South Jason Street (Schonewill properties) 1354, 1356, and South Jason Street (Courtesy Electric Properties) 1140 West Louisiana 24 27,626 tons of contaminated material removed Phase D Conducted July 1991 through September 1991 Properties: 1235 South Jason Street 1345 South Jason Street 50 tons of contaminated material removed

The Colorado State Historic Preservation Officer concluded that 1298 South Kalamath Street building was eligible for inclusion in the National Register of Historic Places. Since the remedial action design included removal of the brick portion of the building, documentation was prepared in accordance with the guidelines of the National Park Service Historic American Engineering Record prior to demolition. The documentation was delivered to the National Park Service and the State of Colorado.25

During Phase A, an engineering assessment of the 1298 South Kalamath Street building showed that it did not possess the structural integrity to withstand the stresses of the required decontamination efforts. 41

The safest and most cost-effective remedy involved demolition of the building. After the property was verified to be clean, the excavation was backfilled with clean fill and compacted. Following the release of the property back to 1298 South Kalamath Street, the property owner constructed a new building on the site.26

Additional assessment performed after Phase A remedial action showed radium contamination to be present under portions of the blue metal building located adjacent to the brick building. Phase B remediation started with the final clean up of the 1298 South Kalamath Street property. To facilitate removal of the contaminated soil, a 10 by 85 foot area of the concrete floor was saw cut, and the concrete was removed. Radium contaminated soils were removed in this area to a depth of three feet. Once the area was verified clean, the concrete floor was reconstructed. This work lasted approximately one month and 49 tons of contaminated materials were removed.

One area located south of the 1377 South Jason Street was assessed to have limited, spotty contamination present at depths ranging from two to eight feet. 1000 West Louisiana Ave was assessed to have widespread contamination at depths of eight feet. The quantity of contamination excavated in the area south of 1377 South Jason Street increased 400 percent over the estimated amount reported in the remedial design. The full extent of contamination in this area was difficult to assess prior to excavation because there were three separate lenses of contamination at different depths. This problem was magnified by the shielding of the clay-rich fill material located above the contaminated lenses. Because groundwater was encountered at 25 feet, six tons of moderately contaminated soil remained at the location. The radiological assessment data showed contamination present along the southern boundary of the 1377 South Jason Street at a depth of 51 inches. A 30 inch diameter steel water line located in this area at a depth of 62 inches was shut down for remediation. Hand excavation removed most of the contamination, but limited contamination was left in place beneath of portion of the water main.

The contamination did not pose a hazard to public health or the environment because the contamination was left in place under 5 to 25 feet of clean fill. All repair and replacement work near the water line below the water table would need to be informed of the contamination and would need to take precautions in order to prevent inadvertently spreading the material.

During Phase B, 32,389 tons were excavated. 1,549 tons came from the 1298 South Kalamath Street, 8,412 came from the area south of the PCA building, and 22,428 tons from the 1000 West Louisiana Avenue property.

A total of 340 gondola cars and 3 bi-modal containers were shipped to the disposal facility between July and December 1990. The transport and disposal contractor installed an in-rail scale to enable rail cars to be loaded near capacity and eliminated the problem of overloading.27

Phase C covered 2.4 acres of exterior contamination. Once the contamination in the east parking lot was completely excavated, reconstruction was initiated. Approximately 6,900 tons of soil and debris were removed from this portion of OU-3.

At the 1380 S. Jason property, the contamination extended laterally beyond the assessed boundaries which increased the amount of contaminated material removed from this property by approximately 450 tons. A total of 1,326 tons of contamination was removed from the 1380 S. Jason property, and 600 tons of contaminated material was excavated from the east side of Jason Street and 1140 West Louisiana.

Approximately 13,700 tons of contaminated material was excavated from 1377 South Jason Street north parking lot, and one 5,000 gallon underground storage tank was removed during the remediation of the 1377 South Jason Street north parking lot by the owner of the property.

Final remedial activity during Phase C involved the decontamination of the load-out area and spotty contamination present on the BNRR rail spur, which runs along the west side of the 1377 South Jason Street north parking lot. Approximately 4,700 tons of contamination was removed. A total of 288 gondolas were shipped between March and September 1991.

The contamination on the Phase D properties was discovered by the State Project Officer during the Phase B remedial action. Fifty tons of contaminated material was excavated and removed from the Phase D properties, and 1.5 bi-modal containers were shipped to the disposal facility during July 1991.

Table 3: Materials Left in Place as Averaged Areas-OU-328

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-3 Area A/Area B 25/24 5.0 pCi/g East of South Jason, at the base of mature trees OU-3 Area C 105 10.9 pCi/g North of 1140 West Louisiana building- along underground utility lines beneath West Louisiana Ave. OU-3 Area D 506 13.8 pCi/g North wall of the 1380 S. Jason building- along foundation OU-3 Area E 509 10.3 pCi/g Alley of the 1298 South Kalamath Street building

Contaminated material was excavated using front end loaders while field personnel monitored the excavated area for remaining contamination using hand-held radiation detectors. Soil samples were collected and analyzed to verify that excavation activities achieved conformance with the applicable standards. After excavation of contaminated materials, samples representative of the 6-inch thick (15cm) soil layer at the bottom of each verification area were collected and blended to create a composite sample for the specific verification area. All of the composite samples were analyzed for Ra-226, and select 43

samples were analyzed for thorium-230 (Th-230), thorium-232, uranium-238, and potassium-40. Th-230 was identified in area V-122 in concentrations that exceeded the proposed clean-up criterion for that radionuclide of 600 dmp/100cm2 based on a limit of 1 mrem/y. The EPA determined that this occurrence did not present a risk to human health or the environment.29

Contaminated materials were transported by rail in covered gondola cars to the permanent off-site disposal facility. The disposal contractor loaded material directly onto the cars at the site. Each gondola car was sealed, surveyed, and decontaminated, as necessary, prior to leaving the site and was only used for transportation of wastes from the Denver Radium Site. The wastes were labeled “Denver Radium Superfund Waste,” and a composite sample was collected from each railcar as it was loaded and analyzed to ensure that the material conformed to the acceptance requirements of the disposal facility.

Off-site air-quality monitoring data were collected before, during, and after remedial action. One low- volume air particulate sampler, two atmospheric radon detectors, and one gamma thermoluminescent dosimeter were placed at each of five measurement locations. The results indicated no significant differences between the data sets that were collected over the entire period.30

Atmospheric radon measurements were collected using Terradex outdoor Type F Track Etch® radon detectors. Two detectors were exposed in an environmentally protected enclosure approximately one meter above ground level, and each detector consisted of an alpha-sensitive film protected by a membrane filter permeable only to radon. All atmospheric radon concentrations measured during the reporting period were below the regulatory standard of 3.0 pCi/L above background of 581 pCi/m3 (1000L is equal to 1m3).32

The average radon daughter concentration (RDC) results were 0.0067 WL for the 1377 South Jason Street building which conformed to EPA standards for occupied or habitable buildings. Prior to remediation activities, elevated RDC measurements were identified at the building. Following remediation activities, the RDC levels were 0.0238 WL which also conformed to EPA standards for occupied or habitable buildings.34 44

In 1999, Metro Wastewater Reclamation District rehabilitated a sanitary sewer located along the Sanderson Gulch. The rehabilitated line terminated at its junction with the existing Platte River interceptor sewer at the intersection of West Louisiana Avenue and Jason Street in OU-3.35 This sewer line was completed under a CDPHE and City and County of Denver approved Soils Management Plan. The sewer was installed by digging two holes on opposite sides of the presumed contamination. A tunnel- boring device was then used to bore underneath the location of the presumed contamination, pulling the new sewer line as it progressed underneath West Louisiana Street. All soils were segregated, containerized, characterized, and managed under the Soils Management Plan.36

Prior to construction activities, HDR Engineering performed groundwater sampling and radiological analysis at OU-3. The preferred discharge option was Sanderson Gulch. In order to obtain a discharge permit through CDPHE, groundwater characterization for volatile organic compounds (VOC’s) was required. The groundwater samples collected from the fill area contained no detectable VOC’s. Groundwater samples from OU-3 displayed measurable radioactivity for all analytes in both filtered and unfiltered samples. Filtered samples at two monitoring wells for Ra-226 results were 2.40 pCi/g and 9.09 pCi/g. Filtered samples at the same two monitoring wells for Ra-228 were 9.14 pCi/g and 1.60 pCi/g respectively.37

Contamination beneath the water line on the south end of 1377 South Jason Street property was overlain by approximately 6 to 8 feet of clean fill. This contamination was declared not to pose a hazard to the public health or the environment under the current land use scenario. Data after the initial remedial action indicated a substantial amount of contamination left in place under South Jason Street, South Platte River Drive, and beneath the 1377 South Jason Street building.

The total cost of remedial action at Operable Unit 3 from August 1989 to September 1991 was $13,591,560.00.38

Supplemental Standards

The EPA criteria for determining that conditions in a given instance warrant a deviation from usual remedial action procedures are known as supplemental standards for remedial action under the regulations set forth in the National Contingency Plan, 40 CFR Section 192.22. A Supplemental Standards Report for OU-3 was completed in June 1995 to document the location and rationale for leaving 5,868 yds3 of radiological contaminated soil in place under South Jason Street, around the 1377 South Jason Street building, and along South Platte River Drive.39

The locations where contaminated soils were left in place include:

1. Deposits of Ra-226 contaminated soil left in place along the east and west sides of and beneath South Jason Street and South Platte River Drive and contamination associated with a water line beside South Platte River Drive; 2. Deposits of Ra-226 contaminated soil left in place below groundwater south and northwest of the 1377 South Jason Street building; and, 3. Deposits of Ra-226 contaminated soil in the 1:1 slope around the foundation of the 1377 South Jason Street building left in place to avoid causing structural damage to the building.40 45

Concentrations of the Ra-226 left in place range from 20 pCi/g up to 687 pCi/g.

The conditions at OU-3 met criterion (c) of 40 CFR Section 192.21 which addresses the unreasonably high cost of remedial action relative to the long-term benefits. Areas where waste material was left in place with Supplemental Standards in accordance with 40 CFR Part 192, Subpart C, require the maintenance of Institutional Controls (ICs) and do not allow for unrestricted use and unrestricted exposure. IC plans require that property owners use best efforts to maintain current zoning and prevent changes to land use.

In November 2005, Robert Terry of the American Board of Health Physics (ABHP) Certified Health Physicist, Hazardous Materials and Waste Management Division with (CDPHE) analyzed the 1995 Supplemental Standards Report for OU-3. He concluded that the supplemental standards met current Applicable or Relevant and Appropriate Requirements (ARAR) of CCR 1007 Parts 4.14, 4.61.3.2 and 4.61.3.3- Standards for Protection Against Radiation. Federal law requires on-site remedial actions attain or waive Federal environmental ARARs. However, he cautioned making any determination that the Health Risk Assessment for Denver Radium Site Ou-3, where supplemental standards were applied, meets the current ARAR requirements of CCR 1007 Part 4.61.2.

Furthermore, the report determined that given the radiation dose estimates that were presented in the Health Risk Assessment for Denver Radium Site OU-3, further remedial action can be deferred for the time being as long as proper ICs are maintained for controlling radiation doses. However, the report clarified that the contamination on-site is significant and where eventual cleanup to remove contaminated material with Ra-226 is at concentrations up to 687.1 pCi/g is still recommended.41

Jason Street Remedial Action

In 2007-2008, Jason Street was remediated from Louisiana to South Platte Drive by Envirocon, Inc. The project was completed in three phases to remove the radium impacted material beneath the asphalt at depths varying from approximately 2- to 6-feet maximum depth. Phase 1 began at the northern end of the extent of contamination (near the Louisiana intersection) and proceeded south for approximately 125 lf. Phase 1 was implemented from September 17th-October 12th, 2007. Phase 2 began approximately 125 linear feet to the south of the northern end of the extent of contamination (near the Louisiana intersection) and proceeded south for approximately 225 linear feet. Phase 2 was implemented from September 21st- December 3rd. Phase 3 began approximately 350 lf to the south of the northern end of the extent of contamination. Phase 3 was implemented from October 9th, 2007-January 7, 2008. All wastes left in place under Supplemental Standards for Jason Street were removed.

Monitoring

On August 4, 1994, water samples were taken from the Jason Street interceptor interconnect and tested for radium. The results indicated that Ra-226 levels in one well were 12 pCi/L plus or minus 2 pCi/L, and that Ra-228 levels in the same well were 28 pCi/L plus or minus 2 pCi/L. The results for a second 46

well indicated that Ra-226 levels were 51 pCi/L plus or minus 6 pCi/L and Ra-228 levels were 16 pCi/L plus or minus 2 pCi/L.42

On December 6, 2001, groundwater and surface water samples were taken at the Hospital Shared Services (HSS) facility on South Platte River Drive. The analytical results indicated that iron, manganese, Ra- 226, Ra-228, gross alpha, and gross beta were above the State of Colorado drinking water standards for groundwater (5 pCi/L for Ra-226). The high concentration of radionuclides was of concern and was found at concentrations of what appeared to be contaminant migration from the Shattuck site (Denver Radium OU-8 site), contaminant migration from the Jason Street site (Denver Radium OU-3 site), a potential new source of contamination, or a radiological waste source in the old landfill beneath the property.43

In July 2003, SM Stoller, under contract from the EPA and CDPHE, installed and developed six new groundwater monitoring wells surrounding the OU-3 site. The new wells, along with the HSS site, were sampled by CDPHE on July 15-17, 2003. The analytical results revealed significantly lower concentrations of contaminants in the HSS well, as compared to the December 2001 results. The samples indicated that the maximum contaminant levels (MCL) for gross alpha and gross beta were exceeded in a well (OU3-GW5) located within the supplemental standards waste left in place, and the well immediately down gradient of that location (OU3-GW4) just exceeded drinking water MCLs.44

Further groundwater analysis occurred in 2006 with fieldwork conducted on June 22, 2006. The Hazardous Materials and Waste Management Division (HMWMD) of CDPHE conducted two rounds of groundwater monitoring on shallow alluvial groundwater monitoring wells at the OU-3 site. Samples were collected from six of the seven groundwater monitoring wells, and the HSS MW-4 well. Gross alpha and gross beta were detected in two of the seven monitoring wells at levels about the State Drinking Water MCL (OU2-GW4 and OU3-GW5). The seasonal change of groundwater flow is likely the cause of a change in well OU3-GW4 from being above the Drinking Water Standards in July 2003 to being below the Drinking Water Standards in February 2004.45

In the initial sampling of the HSS well on December 6, 2001, the well had gross alpha at 297 pCi/l and gross beta at 215 pCi/l. The subsequent sampling events identified gross alpha at <4 pCi/l (7/15/03); <4 pCi/l (2/11/04); and 1.1 pCi/l (6/22/06). Gross beta was detected at 20 pCi/l (7/15/03); 11 pCi/l (2/11/04); and 17 pCi/l (6/22/06).46

Natural attenuation of residual groundwater contamination is expected.47

Institutional Controls

An initial Management Plan was prepared for OU-3 by GEI Consultants, Inc. in July 1998 to address management procedures needed such as public and worker exposure concerns and ultimate material disposal.48 Also, a Management Plan addressing OU-2, OU-3, and OU-6 was written in 2003 applying to affected rights-of-way. The Management Plan addressed activities that would result in the removal, transportation, and disposal of contaminated materials from Affected Streets.49 47

ICs, including groundwater ICs, are in effect at OU-3 by a City and County of Denver Municipal Ordinance (Ordinance No. 668-13, adopted December 9, 2013). The Denver Revised Municipal Code, Chapter 48 [Solid Waste], Article VIII [Disposal fees]50 created a special zoning for these properties and prohibits disposal of the materials in Denver without paying a fee. The City will charge $5.10/cubic foot of radioactive waste or radium contaminated material to any person disposing or implementing a remedial control of the above material, unless the disposal is incidental to installation, maintenance, repair, improvement, or replacement of utilities, streets, sidewalks, or alleys in public rights-of-way.51

An informational IC exists for OU-3 by the Colorado State Engineer requiring notification for new groundwater water wells.52 The State Engineer has agreed to include on each permit application correspondence, each well permit, and each acknowledgement for a Monitoring Hole Notice of Intent for the affected area, a notice that the applicant should contact the CDPHE and the EPA for information regarding groundwater quality. If any person seeks to drill a well into groundwater in this area, the State Engineer notifies that person that the groundwater is contaminated. They also are notified that they should contact the EPA and CDPHE, and that the State Engineer will send a copy of the well permit to EPA and CDPHE.53 The State Engineer has agreed to provide copies of such correspondence containing the notice to the CDPHE and EPA; the affected area has been delineated by EPA and CDPHE.

The primary Operations and Maintenance activity at the OU-3 properties is to monitor compliance of the ICs in place.54

De-listing

The area that encompassed Denver Radium OU-3 was already developed and utilized for commercial and light industrial uses at the time of remedial action. A site visit performed by the EPA in August 2003, confirmed that all properties at OU-3 were being used for the same purposes.

A Final Close-Out Report was signed on September 27, 2006.55 In a letter dated January 2, 2008, the State of Colorado concurred with the EPA’s intent state in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.56

On November 8, 2010 the direct final partial deletion of the Denver Radium Superfund Site from NPL became final, and all of OU-3 of the Denver Radium Superfund Site was deleted from the NPL.

Bibliography

ARIX. May 1982. Engineering Assessment and Remedial Action Plan for Radium Processing Residues at 1000 West Louisiana Avenue.

ATEC Associates, Inc. August 11, 1994. Radium in Water, Jason Street Interceptor Interconnect.

City and County of Denver. Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES.

City and County of Denver. February 13, 1992. Re: Denver Radium Sites/OU-3, 1000 W. Louisiana Avenue.

City and County of Denver. June 17, 2003. Management Plan Denver Radium Site Operable Units II, III, and VI.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and the Environment. November 2005. ATTN: Mark Rudolph, RE: Assessment of 1995 Supplemental Standards for OU-3.

Colorado Department of Public Health and the Environment. November 8, 2006. Groundwater Monitoring Report.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

GEI Consultants, Inc. July 31, 1998. Management Plan Denver Radium Site Operable Unit 3- 1000 West Louisiana Avenue.

HDR Engineering Inc. July 12, 1999. Groundwater Characterization Report Sanderson Gulch Sewer Rehabilitation, HDR Project No. 6926-020-050.

HDR Engineering Inc. November 8, 1999. Soils Management Plan Sanderson Gulch Common Interceptor Sewer Rehabilitation Project.

RUST Geotech Inc. April 1994. Denver Radium Site Operable Unit 3 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

RUST Geotech Inc. October 1994. Denver Radium Superfund Site Supplemental Standards Report, Operable Unit 3.

State of Colorado. February 15, 2002. Letter to Mr. George Schiel, President: Hospital Shared Services.

State of Colorado. January 2, 2008. Notice of Deletion. 49

Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988.

U.S. Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium 3, Colorado.

U.S. Environmental Protection Agency. September 20, 1991. Remedial Action Completion Report: OU-3.

U.S. Environmental Protection Agency. September 17, 1992. The Jason Street Portion of the Denver Radium Site

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium.

U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site.

CH2M Hill. July 1987. Feasibility Study. Denver Radium Site.

Endnotes

1 U.S. Environmental Protection Agency. September 29, 1987. Superfund Record of Decision: Denver Radium 3, Colorado. 2 RUST Geotech Inc. April 1994. Denver Radium Operable Unit 3 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 3 U.S. Environmental Protection Agency. September 29, 1987. 4 CH2M Hill.July 1987. Feasibility Study. Denver Radium Site. 5 RUST Geotech Inc. April 1994. 6 U.S. Environmental Protection Agency. September 29, 1987. 7 RUST Geotech Inc. April 1994. 8 U.S. Environmental Protection Agency. September 29, 1987. 9 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium 10 ARIX. May 1982. Engineering Assessment and Remedial Action Plan for Radium Processing Residues at 1000 West Louisiana Avenue 11 CH2M Hill. July 1987 12 Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988 13 CH2M Hill. July 1987. 14 CH2M Hill. July 1987 15 U.S. Environmental Protection Agency. September 29, 1987. 16 CH2M Hill. July 1987 17 CH2M Hill. July 1987 18 U.S. Environmental Protection Agency. September 29, 1987. 19 U.S. Environmental Protection Agency. September 25, 2006 20 City and County of Denver. February 13, 1992. Denver Radium Sites/OU-3, 1000 W. Louisiana Avenue. 21 U.S. Environmental Protection Agency. September 17, 1992. The Jason Street Portion of the Denver Radium Site 22 U.S. Environmental Protection Agency. September 20, 1991. Remedial Action Completion Report: OU-3. 23 U.S. Environmental Protection Agency. September 25, 2006 24 U.S. Environmental Protection Agency. September 20, 1991. 25 RUST Geotech Inc. April 1994 26 U.S. Environmental Protection Agency. September 20, 1991 27 U.S. Environmental Protection Agency. September 20, 1991 28 RUST Geotech Inc. April 1994 50

29 RUST Geotech Inc. April 1994 30 RUST Geotech Inc. April 1994 31 RUST Geotech Inc. April 1994 32 RUST Geotech Inc. April 1994 33 RUST Geotech Inc. April 1994 34 U.S. Environmental Protection Agency. September 25, 2006 35 HDR Engineering Inc. November 8, 1999. Soils Management Plan Sanderson Gulch Common Interceptor Sewer Rehabilitation Project. 36 U.S. Environmental Protection Agency. September 25, 2006 37 HDR Engineering Inc. July 12, 1999. Groundwater Characterization Report Sanderson Gulch Sewer Rehabilitation, HDR Project No. 6926-020-050. 38 U.S. Environmental Protection Agency. September 20, 1991. 39 RUST Geotech Inc. October 1994. Denver Radium Superfund Site Supplemental Standards Report, Operable Unit 3. 40 U.S. Environmental Protection Agency. September 25, 2006 41 Colorado Department of Public Health and the Environment. November 2005. ATTN: Mark Rudolph, RE: Assessment of 1995 Supplemental Standards for OU-3. 42 ATEC Associates, Inc. August 11, 1994. Radium in Water, Jason Street Interceptor Interconnect. 43 State of Colorado. February 15, 2002. Letter to Mr. George Schiel, President: Hospital Shared Services. 44 Colorado Department of Public Health and the Environment. November 8, 2006. Groundwater Monitoring Report. 45 Colorado Department of Public Health and the Environment. November 8, 2006 46 Colorado Department of Public Health and the Environment. November 8, 2006 47 Colorado Department of Public Health and the Environment. September 30, 2008. Five-Year Review, Denver Radium Site 48 GEI Consultants, Inc. July 31, 1998. Management Plan Denver Radium Site Operable Unit 3- 1000 West Louisiana Avenue. 49 City and County of Denver. June 17, 2003. Management Plan Denver Radium Site Operable Units II, III, and VI. 50 Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES. 51 Colorado Department of Public Health and Environment. September 30, 2008. 52 U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site. 53 Colorado Department of Public Health and Environment. September 30, 2008. Five-Year Review, Denver Radium Site 54 Colorado Department of Public Health and Environment. September 30, 2008. 55 Colorado Department of Public Health and Environment. September 30, 2008. 56 State of Colorado. January 2, 2008. Notice of Deletion 51

Denver Radium Superfund Site

Operable Unit 4, 5, 9B

Table of Contents:

Background Information 52 Remedial Investigation 54 Remedial Objectives/Record of Decision 54 Explanation of Significant Differences 55 Remedial Action 55 Supplemental Standards 60 OU-9B (ROBCO Metals) 62 Ground-water Monitoring 64 Institutional Controls 65 De-listing 66 Bibliography 67 Endnotes 69

Tables and Figures:

Table 1: Operable Unit 4 & 5 Properties 53 Table 2: Remedial Phases of OU-4, -5 56 Table 3: Materials Left in Place as Averaged Areas-OU-4, -5 57 Table 4: Action Levels for Metals of Concern at ROBCO 63

Background Information

Denver Radium Operable Units 4 (OU-4) and 5 (OU-5) comprised both the 500 South Santa Fe Drive property and adjacent property, immediately east of OU-4, owned by the Denver and Rio Grande Western Railroad (D&RGWRR). Operable Unit 4, the 500 South Santa Fe Drive property, is a 17.3 acre parcel near the South Platte River bounded by South Santa Fe Drive on the west and the D&RGWRR right-of- way on the east. The property to the north is occupied by a Regional Transportation District (RTD) bus maintenance facility. The site consisted of a brick manufacturing plant and associated equipment and various other buildings. OU-5 consisted of a 1.6 acre portion of the D&RGWRR right-of-way in Denver's main rail corridor. OU-4 and -5 were added to the National Priorities List (NPL) as part of the Denver Radium Site in September 1983.1

The 500 South Santa Fe Drive property is located within the Platte River Valley, but is not within the designated flood plain. The site is underlain by fill material, alluvium, and the Denver formation. Depth to groundwater is approximately 16 feet and depth to bedrock is approximately 25 feet. The topography of the site is predominately flat, although surface runoff tends westward toward the South Platte River.2 Groundwater beneath the property is expected to flow to the southwest, but can be influenced by the presence of paleo-channels and irregularities.3 The South Platte River crossed the property until 1908 when it was diverted to the west.4

In the late 1800s, a series of ore refining and smelting facilities operated at OU-4 under various names: Bailey Smelter Company; Colorado Zinc Company; and Sutton, Steele, and Steele Mining and Milling Company. Waste material likely was disposed in the nearby South Platte River channel (at the time located 100 feet to the west).5 The Merchant’s Mill Ditch was constructed through the eastern part of the site in the early 1870s and transported water from the South Platte River northward, approximately eight miles, until emptied back into the river near its confluence with Cherry Creek.6 The ditch was in use until 1910, and then abandoned and used as a dump by various operations at this site. The National Radium Institute (NRI) built a plant on the site in 1914, a portion of which was located over the course of the Merchant’s Mill Ditch, and went into full-scale production in June 1914. By 1916, 8.5 grams of radium had been produced from 1,500 tons of ore. The plant ceased operation in 1917. Some fractioning operations may have continued for a year afterward. The office and laboratory buildings built by the NRI stood on-site when remedial action activities began.

The NRI plant remained empty until 1920 when the Minerals Recovery Company, specializing in manufacturing concentrating machines, purchased the property. Some evidence and historical documents support that the company signed a contract to produce 10 grams of radium at the site, and some reports refer to “radium processing” occurring at the plant. However, no records have been found that clarify whether radium was produced, or in what quantities, during the early 1920s. The company ceased operations in 1925, and ownership of the property during the next two years is uncertain. In 1927 the property was occupied by the U.S. Gasoline Recovery Corporation plant, and in 1930 the southern half of the area was used by the Prest-O-Lite Company, which manufactured acetylene and acetylene apparatus.

Various businesses occupied the property during the 1930s and 1940s such as:  Security Oil and Refining Company

 Prest-O-Lite Company  Midway Gas and Oil Company  Knight Non-Metallic Corporation  Security Petroleum  Brannan Sand and Gravel Company  Luke & Smith Warehouse  Western Verniculite Company  Indian Village Tourist Camp  Western Lumber Company

In 1940, ROBCO acquired the property and commenced operations at 500 South Santa Fe Drive until moving to another property in the early 1980s.

OU-5: D&RGWRR had several rail lines and spurs on the property. Some areas of OU-5 show evidence of use as landfills by various companies that operated on the site. Uranium ore and refuse from processing facilities and laboratories were found at depths up to 20 feet. The man-made fill is underlain by alluvial deposits of sand, gravel, clay, and shale.7

OU 9-B (Metals): In September 1998 during remedial activities occurring at OU-4, approximately 16,540 cubic yards (yds3) of soil containing elevated levels of arsenic, cadmium, chromium, copper, lead, selenium, and zinc were discovered. This contamination was the result of ore processing operations and was found to be exempt from RCRA regulation in accordance with 40 CFR 261.4(b)(7). Radiological contamination was not associated with this material. The contamination was identified east and west of the pit and in four small discrete outlying deposits.8 An investigation to characterize the nature and extent of metals contamination was conducted in 1989 and 1990. This metal contamination is believed to be from the operation of the Tabor Smelter on this property in the 1880s and 1890s.9

Table 1: Operable Unit 4 & 5 Properties10

Property Name at Time of Address Operable Unit ROD OU-4 Robinson Brick and Tile 500 South Santa Fe Drive Company (ROBCO) now Home Depot OU-5 Denver and Rio Grande Western Immediately east of OU-4 Railroad right-of-way (D&RGWRR)

Remedial Investigation

In May 1982, a consulting firm completed an initial engineering assessment of the 500 South Santa Fe

Drive property. In April 1986, CH2M Hill and Jacobs Engineering Group completed a Remedial Investigation Report (RI), and in September 1986, completed a Feasibility Study (FS). Focusing on the radium and uranium processing residues discarded in the early 1900s, the RI identified approximately 7,005 cubic yards (yds3) of contaminated soil and 199 yd3 debris (concrete, wood, tile, and plaster board and sheet metal siding) at depths as great as 44 inches.11 Approximately 803 yd3 of contaminated soil was identified at the adjacent railroad property, located to the east of the ROBCO site.12 Average radium concentrations ranged from 11 to 3,307 picocuries per gram (pCi/g), and a maximum concentration of Radium 226 (Ra-226) of 5,093 pCi/g was detected inside the laboratory.13

Gamma radiation readings in excess of background were found over 12 % of the 17.3 acre of the ROBO site and over 30% of the 1.6 acre D&RGWRR right-of-way. Surface gamma radiation readings exceeding 1000 microroentgens per hour (µR/hr) above background were found in several locations, including inside the laboratory.14 Alpha radioactivity contamination was found in excess of State of Colorado standards in all three buildings. Low-levels of non-radiological contamination, mainly polyaromatic hydrocarbons, were detected at the 500 South Santa Fe Drive site. No indication of migration via surface water drainage or toward groundwater was observed.15

In November 1987, UNC Geotech prepared a Supplemental Radiological Data report for OU-4 and OU-5. The results confirmed the previously collected data. Radium concentrations in the contaminated areas ranged from 6 pCi/g to 4,310 pCi/g. Contamination was determined to exist on property owned by the RTD. At the time of the report, the area was used for parking. The report recommended immediate restrictions on parking in the RTD parking lot to prevent the spread of contamination where surface contamination was identified. 16

In 1991, a Focused Feasibility Study was completed to address the non-radiological, metal contaminants of concern at the ROBCO site. A risk assessment determined that dermal contact and incidental ingestion of soils contaminated with arsenic, lead, and zinc concentrations exceeding 79 ppm, 1,000 ppm and 17,000 ppm, respectively, will increase the risk of health hazard associated with the site. The area of contamination covered approximately 207,000 square feet or approximately 4.8 acres. The soils volume contaminated with arsenic, zinc, and lead was estimated to be 16,540 yd3. 17

Remedial Objectives/Record of Decision

The selected remedy in the September 30, 1986 Record of Decision (ROD) included full removal and permanent off-site disposal. The scope of remedial action included:

1. Removing the approximately 7,000 yd3 of contaminated soil and 200 yd3 of building debris from the property and storing it in a temporary off-site storage facility; 2. Maintaining the temporary storage facility until a facility for the permanent disposal of Denver Radium Site waste became available; and

3. Transporting the contaminated material from the off-site storage facility to the off-site permanent disposal facility.

Plans for off-site temporary storage were abandoned when a permanent disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah became available in 1988.18

In December 1994, the EPA issued an Explanation of Significant Differences (ESD) to address on-site conditions that became apparent after the ROD was signed. The following differences were revealed:

1. The area of contamination and associated volume was greater than estimated in the ROD; 2. Relatively small volumes of Ra-226 and Th-230 contamination were left in place; and 3. Soil contaminated with Th-230 was removed from the site and shipped to the permanent disposal facility.19

Remedial Action

Remedial activities were conducted in three phases that began in April 1988 and concluded in March 1991. The total quantity of material removed during remediation was 96,984 tons1 of contaminated material.20 Contaminated material from Phase A was temporarily stockpiled on the eastern portion of the property, which was remediated during Phase B. The remainder of the property was remediated during Phase C. Approximately, 2,100 tons of radioactive material also was contaminated with metals.21 During the initial phase of remediation, a deep excavation pit was created as radiological contamination was removed. The pit was only partially backfilled at the request of the EPA.22

1 The July 1994 Closeout Report states that the quantity of material removed during remediation was 105,555 tons.

Table 2: Remedial Phases of OU-4, -523

Phase A Conducted April 25, 1988 through November 8, 1989

57,586 tons of contaminated material excavated and stockpiled on-site Phase B Conducted October 23, 1989 through March 7, 1990

The stockpiled material from Phase A (including 1,290 tons of contaminated material with elevated levels of Th-230) and 9,677 tons of contaminated material located below the stockpile were excavated and transported to the Envirocare facility. Phase C Conducted November 1, 1990 through March 7, 1991

29,271 tons of contaminated material removed and transported to the Envirocare facility.

Radiological contamination at the ROBCO Site was excavated in six-inch lifts to minimize the amount of clean material removed with the waste. After a lift was removed, the excavation was surveyed to determine whether it was necessary to remove another lift.

During Phase A, the remedial action plan called for the demolition of the grinding plant and the NRI office and laboratory. The Colorado State Historic Preservation Officer concluded that the latter two buildings were eligible for inclusion in the National Register of Historic Places. The buildings were documented in accordance with the guidelines of the National Park Service Historic American Engineering Record. Results of this procedure were furnished to the National Park Service and the State of Colorado.24

The contaminated material that was excavated during Phase A was temporarily stockpiled on site in anticipation of the transportation and disposal contract being awarded in the spring of 1989. The stockpile was stabilized using an encrusting agent awaiting the start of the load out operation. On September 19, 1988, construction activities at the site were suspended due to discovery of cadmium contamination on the face of the excavation in the area west of the grinding plant. After analysis of the non-radiologically contaminated material, radium excavation resumed at the site on October 20, 1988.

A soil deposit containing elevated concentrations of Thorium-230 (Th-230) was discovered during Phase “A” excavation. The EPA made the decision to remove the Th-230 contaminated soils based on the fact that the elevated concentration would result in the growth of Ra-226 to a significant level within a relatively short period of time.

The last shipment of waste left the site on March 4, 1991, and a final inspection was held on March 14, 1991.25

Table 3: Materials Left in Place as Averaged Areas-OU-4, -526

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-4 Area E 20 7.2pCi/g Adjacent to and beneath the railroad tracks OU-4 Area F 225 11.8pCi/g Adjacent to and beneath the railroad tracks OU-5 Area F1 9 11.8pCi/g Adjacent to and beneath the railroad tracks OU-5 Area G 90 11.0pCi/g Adjacent to and beneath the railroad tracks

The contaminated materials were excavated using front end loaders and track hoes while field personnel monitored the excavated area for remaining contamination using hand-held radiation detectors. Soil samples were collected and analyzed to verify that excavation activities achieved conformance with the applicable standards.27

Contaminated materials were transported by rail in covered gondola cars to the permanent off-site disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah. Material was loaded directly onto the cars at the site by the Geotech transportation subcontractor. Each gondola car was filled with material and then sealed, surveyed, and decontaminated, as necessary. The cars were used only for the transportation of wastes from the Denver Radium Site, and each car was labeled “Denver Radium Superfund Waste.” A composite sample was collected from each railcar and analyzed for Ra-226 and by the Extraction Procedure (EP) toxicity method for arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver. Every tenth sample was analyzed in the laboratory for Ra-226, Th-232, and Potassium-40 (K-40). Selected samples were analyzed for Th-230. Results of the analyses of samples obtained from a drilling program were used to verify that Th-230 found at OU-4 and OU-5 did not exist beneath the remediated areas in concentrations exceeding the criteria proposed by EPA’s Region VIII office. Neither sub-floor ventilation systems nor radon decay-product concentration measurements were required.

Approximately 8,750 tons of metals-contaminated radiological mill tailings (RCRA exempt waste) was shipped to the Envirocare of Utah, Inc., facility for disposal, where it was placed in a segregated cell that conformed to RCRA disposal-facility standards. Radiological contaminated material containing asbestos was shipped in barrels to the Envirocare facility.

Air Monitoring Off-site air-quality monitoring data were collected before, during, and after remedial action. One low- volume air particulate sampler, two atmospheric radon detectors, and one gamma thermoluminescent dosimeter were placed at each of five measurement locations. Baseline air measurements were taken at four locations on the OU-4/5 site from October 1987 to May 1988. Further measurements were taken through September 1988, including the first five months of soil excavation on the site. Also, airborne heavy metals monitoring occurred between November 4 and December 7, 1988; air samples were collected in work areas and breathing zones of workers engaged in cleanup activities on the site.28 The results indicated that there were no significant differences between the data sets collected over the entire period.29

Air monitoring results showed that the concentrations of airborne radioactive particulates, atmospheric radon levels, and direct external gamma radiation exposure were well within the limits established in widely accepted public health standards and guidelines. The average lead concentrations off-site were 0.14 micrograms per cubic meter (µg/m3) and peak lead concentration was 0.31 µg/m3 which is still below the EPA’s National Ambient Air Quality Standard of 1.5 µg/m3. Cadmium was analyzed, but was not detected in any of the samples. The average detection limit for cadmium was 0.02 µg/m3. Arsenic and mercury levels were below detection limits in all air samples collected.30

Air particulate measurements were collected using Model LV1 low-volume air particulate samplers manufactured by F&J Specialty Products, Inc. Each sampler was contained in an environmentally protected shelter and was connected to a dedicated electrical power outlet. The samplers were operated continuously for seven days at a nominal rate of five liters per minute for twenty-four hours daily. The filters were analyzed by the Geotech analytical laboratory for natural uranium, Th-230, Ra-226, and polonium-210 (P-210).

EPA has designated 10 CFR 20, Table 11, Column 1, as the relevant and appropriate standard for airborne radionuclides. These standards are expressed as concentrations in microcuries per milliliter (µCi/mL) above background as follows:

Natural Uranium……………………….5.0 X10-12 Th-230……………………………………….8.0 x 10-14 Ra-226…………………………………….…3.0 x 10-12 Po-210……………………………………...2.0 x 10-11

All airborne radionuclide concentrations measured during the reporting period were below the applicable regulatory standard (10 CFR 20).31

Atmospheric radon measurements were collected using Terradex outdoor Type F Track Etch® radon detectors. Two detectors were exposed in an environmentally protected enclosure approximately 1 meter above ground level, and each detector consisted of an alpha-sensitive film protected by a membrane filter permeable only to radon. All atmospheric radon concentrations measured during the reporting period were below the regulatory standard (10 CFR 20, Table II, Column I) of 3.0 picocuries per liter (pCi/l) above background.32

Direct external gamma exposure measurements were collected using TMA/Eberline thermoanalytical environmental dosimeters. Each dosimeter was exposed approximately 1 meter above ground level at each sample location and was submitted to TMA/Eberline Thermo Analytical, Inc. for analysis. All gamma exposures measured during the reporting period were below the limit of 100 millirems per year (mrem/yr) above background. The limit above background refers to the recommendations of the National Council on Radiation Protection and Measurements (1977). The background exposure rates for the Denver area range from 130 to 175 milli rem/year (mrem/yr) (CH2MHill, 1986).33

Non-radiological Contamination: Analyses of discolored soils exposed in the pit walls revealed elevated concentrations of cadmium, lead, and zinc. As requested by EPA, Geotech conducted an investigation to develop a hydrological model for the site and to assess the non-radiological contamination (UNC Geotech, Inc., 1990). The results of this investigation indicated that concentrations of metals in the soil (arsenic, cadmium, copper, lead, and zinc) exceeded typical urban background levels over much of the site. Local cells of low-pH groundwater were associated with elevated levels of cadmium, uranium, zinc, and gross alpha contamination. This investigation identified Ra-226 and Th-230 contaminated soil beneath the floor of the pit and south of the pit at depths of 11 to 15 feet.

Regulated waste (other than residual radioactive material) was identified in three instances:

1. Some of the Ra-226 contaminated soil located in the pit was found to contain lead and cadmium at concentrations above the corresponding RCRA toxicity-characteristic regulatory limits according to results of the EP toxicity method. The soil was exempt from RCRA regulation in accordance with 40 CFR 26J.4(b)(7) because the presence of lead and cadmium in the mill tailings was the result of ore processing operations (Bevill Waste). 2. Asbestos was found mixed with Ra·226 contaminated soils near the north boundary of the property. 3. Soil containing elevated levels of arsenic, cadmium, chromium, copper, lead, selenium, and zinc was identified east and west of the pit and in four small discrete outlying deposits. Concentrations of some of the contaminants exceeded the corresponding RCRA toxicity-characteristic regulatory limits. This contamination was the result of ore processing operations and was found to be exempt from RCRA regulation in accordance with 40 CFR 26J.4(b)(7). Radiological contamination was not associated with this material. This contamination was addressed by the EPA as a separate operable unit (OU-9 - Metals, see EPA 1991). According to the ROD for OU-9 - Metals, issued in December 1991, the selected remedy for this OU included backfilling the pit created during remedial action activities at OU-4/OU-5, capping the contaminated areas,

maintaining the cap and monitoring the groundwater at the site, imposing ICs, and conducting 5- year reviews of the remedy.

Supplemental Standards

The EPA criteria for determining that conditions in a given instance warrant a deviation from usual remedial action procedures are known as supplemental standards for remedial action under the regulations set forth in the National Contingency Plan, 40 CFR Section 192.22. In June 1995, a Supplemental Standards Report was prepared for OU-4 to document the location and rationale for leaving 655 yd3 radium and thorium contamination in place.34

The locations where contaminated soils were left in place include:

1. Area A: 91ft2 area of Ra-226 contamination situated below groundwater north of the pit. 2. Area B: 3,637ft2 area of Ra-226 and Th-230 contamination situated below groundwater beneath the floor of the pit. 3. Area C: Thorium contamination only- gamma scan range: 19-23 4. Area D: Area of Th-230 contamination above the north end of the pit. The average Ra-226 concentration of 3.7pCi/g conforms to EPA standards. The average Th-230 concentration of 44.4pCi/g exceeds the proposed Th-230 limits. 5. V-80: Th-230 concentration was found to be 41.9pCi/g. The results of the analysis were not available until after V-80 was backfilled.

Sampling and analysis were conducted to detect Th-230 contamination, including drilling and sampling holes in verification areas V-22 through V-50 and analyzing the samples from other verification areas for Th-230. The results of the analyses indicated that widespread Th-230 contamination in concentrations exceeding the proposed limits did not exist. 35 Following excavation of contaminated materials, samples representative of the 6-inch-thick (15-cm) soil layer at the bottom of each verification area were collected and blended to form a composite sample for that verification area. The composite samples were analyzed for Ra-226 and, as required, for uranium, Th-232, Th-230, and K-40.

Areas A and B are located below groundwater, Area C is overlain by ten feet of uncontaminated soil, and Area D is overlain by two feet of clean soil. The maximum Ra-226 reading in the contaminated area is 92.9 pCi/g, and the highest Th-230 concentration in the soil is 213 pCi/g.

Remediation of the estimated 655 yd3 would cost approximately $597,672.00. The justification for Supplemental Standards was as follows: 1. No adverse human health or environmental effects expected from current use scenarios. 2. IC Plan will require property owner to use best efforts to maintain current zoning and prevent any change in use. 3. Criterion (c) is met of 40 CFR 192.21. 4. Removal of the soil would be costly and potentially dangerous and would result in any decrease in exposure to the public or the environment.

The Supplemental Standards Report demonstrated that no acceptable health risk would exist if the contaminated soil was allowed to remain at OU-4, and that the costs associated with removing the soils were not justified.

Review of Supplemental Standards Report for OU-4/-5

In response to the findings of the 2003 Five Year Report, a request was made for a review of the Denver Radium Site Closeout Report for OU 4/5, specifically reviewing the supplemental standards. As stated above, a total of four small areas that contain buried residual radioactive contamination were left in place under supplemental standards.

Area A, relatively small at < 100 ft2, is located below groundwater. It is an area described as a pit, which was excavated to groundwater. The area appears to have been once used as a landfill and also had some metals associated with it. Area A had Ra-226 concentrations at 44.5 pCi/g and Th-230 concentrations were near background levels and not of concern.

Area B, an area of 3,637 ft2, is also below the groundwater interface. Area B samples had Ra-226 concentrations ranging from 8.35 pCi/g to 66.9 pCi/g and Th-230 concentrations ranging from 48.3 pCi/g to 213.0 pCi/g.

A discrepancy was noticed for Area C among the Completion Report and the Supplemental Standards report. In the Completion Report, Area C consisted of the walls of the excavation pit. The Completion Report stated that gamma scans did not indicate any residual radioactive material, resulting in no further work. Th-230 does not have a gamma component, and there was no reliable correlation between Ra-226 and Th-230 at this site. In the Supplemental Standards Report, Area C is contaminated with Th-230, and the area matches V-80. V-80 is about 120 ft x 60 ft and was backfilled prior to the analytical results being available. Management determined it would be cost-prohibitive to re-excavate. The Th-230 concentration was listed at 41.9 pCi/g.

Area D, approximately 60 ft x 30 feet, is located at the north end of the pit. Area D had Ra-226 concentrations at 3.7 pCi/g and Th-230 concentrations at 44.4 pCi/g.

Regarding the Health Risk Assessment, the report concluded that the exposure values are consistent with the dose constraint in 4.61.3.2 of the Radiation Regulations.2 However, should land use change and residential properties be constructed at the site, the report recommends using radon resistant construction methods and materials.

Materials Left in Place as Averaged-Areas: None of the four deposits that were left in place as averaged areas are candidates for a single family home to be built over them because the areas are located at railroad right of ways.

2 Colorado Rules and Regulations Pertaining to Radiation Control Part 4, Standards for Protection Against Radiation

Area E and F are under and parallel to the railroad siding, and both Area E and F show point sources (F1) or a very small, thin deposit with high levels of contamination (244.9 pCi/g at 24” depth and 625 pCi/g at 18” depth, respectively) with borehole samples adjacent with significantly less contamination. Area F1 is intimate with the tracks and the deposit is at depth, indicating it is probably not cost-effective to remediate. Area G also contains a small deposit located at 18” depth along the tracks just east of the junction with the siding. The deposit is defined by two excavation control samples that show a low-grade deposit or disseminated piece of ore. When averaged with other available borehole and sample data to represent the remainder of the 100-m2 area, the locations meet the subsurface criteria.

The report concludes that the areas with radium contamination do not need any remediation to fulfill the requirements of the ROD and the current Colorado Rules and Regulations Pertaining to Radiation Control. Rather, the report recommends that deposits be tracked through ICs, and if the railroad tracks were to be replaced or removed, consideration should be given to remediating the area-averaged deposits. 36

OU-9B (ROBCO)

Remedial Action The ROBCO site occupied approximately 17 acres in south-central Denver at 500 South Santa Fe Drive. The South Platte River is approximately 1,000 feet west of the property. In October 1990, URS Consultants performed a soil sample investigation testing 46 two-foot borehole soil samples for total arsenic, total cadmium, and total lead. The highest concentrations of total arsenic, total cadmium, and total lead were found in the burnt trash/debris layer between the asphalt/compacted soil layer and the top of the alluvium. Also the northernmost boreholes, the samples taken closest to the excavated areas, exhibited the most contamination.37 A subsurface investigation was performed at the ROBCO site in 1994 to determine the extent of soil contaminated with metals above EPA action levels, which would be potentially disturbed during the construction of the Home Depot Store. The refined soil calculation indicated that there was 76,822 cubic yards of soil present at the site with concentrations of metals above EPA action levels. Approximately 48,132 cubic yards of heavy metal contamination were contained in the top four to six feet of the ROBCO property, and approximately 24,521 cubic yards of heavy metal contaminated soils were contained in the top two feet.38

As stated in the ROBCO Statement of Work, the remedy was made up of the following components: A. The soil cap will be placed in certain designated areas of metals contaminated soil and shall consist of a minimum of two feet of clean soil. B. Following construction of the soil cap, long term maintenance, groundwater monitoring and ICs shall be initiated.

In the ROD completed on December 23, 1991, the RA alternative was selected to prevent direct contact with or inhalation or ingestion of metals-contaminated soils by covering the affected areas with a soil cover. The remedial action also included a continued down gradient groundwater monitoring for contaminant migration toward the South Platte River via groundwater. The contaminants which pose significant risks were arsenic, lead, and zinc. The Focused Feasibility Report detected other metals such

as chromium, cadmium, copper, and selenium at the site, but was not found present in concentrations which would pose any significant environmental or public health threats.39 The soils contaminated by these metals were largely confined to fill material comprising the area of contamination of sand mixed with cinders, charred lumber, glass shards, rubble, brick material, and metal shavings.40

The table below summarizes the action levels (concentrations above which the health risks are unacceptable) identified in the Focused Feasibility Report for ROBCO.

Table 4: Action Levels for Metals of Concern at ROBCO Metal Value (ppm) Arsenic 79 Lead 1,000 Zinc 17,000

The remedial action was completed in three phases. The closure of the ROBCO site required a phased and shared scope of work between the ROBCO’s Phase I and III Contractor (Enviroclean) and the EPA designated Phase II Contractor (Sverdrup Environmental, Inc. and Spectrum Services, Inc.). The closure of the ROBCO site was completed on April 24, 1996 with the final placement of structural fill. Demolition and excavation activities were performed and soils exceeding the site screening criteria were placed within the Area of Consolidation (AOC), a soil cap was constructed, a geo-textile identification was placed, and the cap system was covered with structural fill. The AOC was divided into 5 distinct zones to allow for “Utility Corridors” that would be constructed with soils meeting the site screening criteria.

Phase I prepared the ROBCO site for excavation, movement and consolidation of heavy metal contaminated soils that exceeded the site screening criteria. During Phase II, the existing ROBCO Building/Plant foundation was rubblized and the area of contamination outside the AOC was excavated. Phase III provided for the onsite construction of the AOC cap, installation of the Identification Barrier, the installation and construction of light pole foundations, electrical conduit placement from light pole foundations, and the placement and compaction of structural fill on top of the Identification Barrier to bring the top of compacted structural fill to the final design grade and contour. The Construction Quality Assurance Contractor mobilized on October 23, 1995. Phase I and III Contractor (Enviroclean) mobilized on October 30, 1995. The Phase II Contractor (Sverdrup Environmental, Inc and Spectrum Services, Inc.) mobilized on November 6, 1995.

Upon completion of Phase I construction of the AOC, a capacity of 19,870 yds3 was available for consolidation of soil exceeding site screening criteria. During Phase II construction, additional soils exceeding site screening criteria were found and a Contingency Zone adding 5,000 yds3 of capacity to the AOC was created.

Lead was detected in a soil sample and exceeded site screening criteria for lead at 2,453ppm. Thus, future activity or construction adjacent to the ROBCO site along the sewer right of way to the south/southwest may encounter lead contaminated soils. Also, during the demolition of an existing 46-

inch sanitary sewer from the south to north tie-in structures, the demolished brick structure was mixed with soil exceeding site screening criteria and compacted in place.

Approximately 62,062 cubic yards of material were excavated and/or moved during Phase II of the remedial action.41 During Phase II activity, 8,599 cubic yards of concrete, debris, and rubble exceeding the site screening criteria were managed from November 1995 to February 1996. From November 1995 to February 1996, 25,736 cubic yards of soil exceeding site screening criteria were managed. The Soils Exceeding Site Screening Criteria (SESSC) were delineated into three categories: as excavated from the utility corridors and toes of the area of consolidation (15,248 cubic yards), as stock-piled for management in the area of consolidation (7,930 cubic yards), and as excavated from the area of contamination, but stock-piled in the area of consolidation for frost management (4,549 cubic yards). At the direction of the EPA, contaminated soils that occurred below the water table were left in place.42

During Phase III, ten light pole foundations were installed in borings drilled using a 30-inch diameter auger and drill rig. Phase III also removed soils from the decontamination pad as well as soil within one foot of the liner (in all directions), and the soil was placed in the AOC Contingency Zone. The Identification Barrier was constructed using a geo-synthetic composite that consisted of High Density Polyethylene (HDPE) plastic Geonet between two layers of felt fabric. The Identification Barrier provided a visual identification of areas in which soils exceeding site criteria are beneath. Finally, the final grading of the ROBCO site was completed using soils excavated from other portions of the site. Other sources of off-site soil used for structural fill were obtained from the Western Mobile pit in Golden, Colorado (20,000 cubic yards of fill material) and from the Cooley pit in Morrison, Colorado (8,000 cubic yards of fill material).43

Groundwater Monitoring

A Groundwater Monitoring Plan (GWMP) was prepared in July 1992 as a requirement of the ROD issued by the EPA in December 1991. Due to poor natural quality and location, the alluvial aquifer was not considered to be a potential drinking water source, and therefore, the objective of the GWMP was to verify that contaminants from the ROBCO Metals site will not reach the South Platte River in detrimental concentrations. Contaminants monitored by the system include the heavy metals arsenic, cadmium, copper, chromium, lead, selenium, and zinc; and the radionuclides gross alpha, gross beta, Ra-226, Th- 230, and uranium.44

Monitoring wells were installed between the OU-9B site and the South Platte River during July 1992. Initial sampling of the wells indicated that heavy metals, cadmium and selenium, were present in the groundwater, and concentrations of the compounds were above Colorado Drinking Water Standards (CDWS). Due to levels of contamination and the questionable source of contamination, additional fieldwork and analysis was conducted from December 7-December 24, 1992. Sverdrup completed the following field objectives:  Purged and sampled twenty monitoring wells,  Collected groundwater samples from twenty-three boring locations,  Collected surface water samples at two locations in the South Platte River,

 Recorded piezometric measurements in available OU-9 and RTD monitoring wells,  Performed rising head hydraulic conductivity test using a slug at seven (7) monitoring well locations, and  Collected soil samples from various, selected boring locations.

The December 1992 groundwater sampling results indicated elevated concentrations of dissolved cadmium, iron, manganese, selenium, and zinc above CDWS. It was suggested that the maximum concentration of cadmium in the groundwater was expected at greater depths and just above the bedrock. The report added that depths just above the bedrock are relatively impermeable and are believed to be a confining stratum in the hydro-geologic profile.45

The origin of contamination was not determined, but based upon the mapping of the groundwater contaminated by excessive concentrations of cadmium; the origin appeared to be the OU-9 site. The results of the field work concluded that the compounds arsenic, lead, and zinc were not affecting groundwater quality down-gradient of the OU-9 site or the surface water quality of the South Platte River. However, the compound, cadmium, was determined to be affecting the groundwater quality, but was not found to significantly affect the quality of the surface water of the South Platte River.46

Periodic groundwater monitoring is a requirement of the ROD as an Operations and Maintenance measure for OU-9B. For more detailed information and a timeline of groundwater monitoring results, refer to Appendix 6-Operable Unit 4, 5, & 9 Groundwater Monitoring Results.

Institutional Controls

Home Depot, U.S.A. the current owner of the ROBCO property implemented an Operations and Maintenance Plan to establish the methods by which the Site will be effectively and safely inspected, operated, and if required repaired.47

In July 1995, an Agreement and Covenant Not to Sue was made and entered into by and between the EPA, Colorado Department of Public Health and Environment (CDPHE) and Home Depot U.S.A., Inc. to settle and resolve the potential liability of Home Depot for the present contamination at the ROBCO property. Home Depot agreed to covenants restricting the use and development of the property in conformance with ICs. The property is restricted to non-residential uses that are compatible with maintaining the integrity of the cap. Other restrictions include prohibiting Home Depot to drill water wells on the property with the exception of groundwater monitoring wells and prohibiting the use of groundwater from beneath the property for any purpose. Home Depot also agreed to ICs regarding development of the property. All metals-contaminated soil excavated from within the Pre-Consolidation or Post-Consolidation AOC by Home Depot must either be re-deposited within the Post-Consolidation AOC and capped or disposed at a permitted off-site facility. Prior to such action, Home Depot must notify the EPA and CDPHE. Home Depot also acknowledged that it was purchasing property where response actions were presently anticipated and may interfere with Home Depot’s use of the property. Home Depot is not obligated to provide funds, materials, supplies, or personnel for the completion of remedial action.48

Home Depot submitted a Draft Operations and Maintenance Plan (O&M plan) on May 30, 1997, and it was approved by CDPHE and the EPA on March 17, 1998. In accordance with the O&M plan, the EPA and CDPHE will perform biannual, offsite groundwater monitoring, and Home Depot will perform biannual inspections of store facilities and site facilities.49 The O&M plan was amended by Home Depot as of August 18, 2003 to plan for construction of the parking lot and two commercial buildings built to the north of Home Depot.50

The Denver Ordinance (No. 668-13) provides ICs at properties where radium-contaminated soil remains in place under supplemental standards. The Denver Revised Municipal Code, Chapter 48 [Solid Waste], Article VIII [Disposal fees]51 created a special zoning for these properties and prohibits disposal of the materials in Denver without paying a fee. The City will charge $5.10/cubic foot of radioactive waste or radium contaminated material to any person disposing or implementing a remedial control of the above material, unless the disposal is incidental to installation, maintenance, repair, improvement, or replacement of utilities, streets, sidewalks, or alleys in public rights-of-way.52

Currently, an informational IC exists for OUs 4, 5, and 9-B by the Colorado State Engineer requiring notification for new groundwater water wells.53 The State Engineer has agreed to include on each permit application correspondence, each well permit, and each acknowledgement for a Monitoring Hole Notice of Intent for the affected area a notice that the applicant should contact the CDPHE and the EPA for information regarding groundwater quality. If any person seeks to drill a well into groundwater in this area, the State Engineer notifies that person that the groundwater is contaminated. They also are notified that they should contact the EPA and CDPHE, and that the State Engineer will send a copy of the well permit to EPA and CDPHE.54 The State Engineer has agreed to provide copies of such correspondence to the CDPHE and EPA. The affected area has been delineated by EPA and CDPHE.

De-listing

A site visit was performed in March 1998 and in August 2003 during the Five-Year Review processes. Since 1993, a storm water retention basin was built on the northern portion of the site.55 The 2003 site visit noted the construction of the Home Depot and parking lot as well as two commercial buildings built to the north of Home Depot. An automotive repair facility (Star Tech Mercedes) and an unoccupied building share a sewer line that was placed through the northern end of the contingency zone for ROBCO metals wastes (OU-9B). The sewer line was confirmed to have been installed properly under the Home Depot O&M Plan.56

EPA and CDPHE have determined that all RA construction activities, including the implementation of institutional controls, were performed according to specifications. A Final Close-Out Report was signed on September 27, 2006.57 In a letter dated January 2, 2008, the CDPHE concurred with EPA in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.58

On November 8, 2010 the direct final partial deletion of the Denver Radium Superfund Site from the NPL became final, and all of OU-4,-5,-9B of the Denver Radium Superfund Site was deleted from the NPL.

Bibliography

CH2M Hill. April 18, 1986. Revised Group 4 & 5 Feasibility Study.

City and County of Denver. Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES.

Colorado Department of Public Health and Environment. November 6, 2000. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO.

Colorado Department of Public Health and Environment. March 7, 2002. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO.

Colorado Department of Public Health and Environment Hazardous Materials and Waste Management Division. November 13, 2003. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment. April 14, 2008. Review of Supplemental Standards Report for OU4/5, Docket 8218. Prepared by Philip Egidi.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

ERM-Rocky Mountain, Inc. December 12, 1994. Subsurface Investigation Robinson Brick Company.

ERM-Rocky Mountain, Inc. June 9, 1995. Robinson Brick Company Groundwater Monitoring Report.

ERM-Rocky Mountain, Inc. April 1996. Phased Remedial Response Action Closure Report: Phases I, II, and III. Robinson Brick Company 500 South Santa Fe Drive, Denver, Colorado 80223.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

Morrison Knudsen Corporation. November 20, 1998. Denver Radium Superfund Site Five-Year Review.

Morrison Knudsen Corporation. September 29, 1999. Technical Memorandum: Materials Left in Place Denver Radium Site.

RUST Geotech Inc. July 1994. Denver Radium Site Operable Unit 4 and 5 Interim Close Out Report for the U.S. Environmental Protection Agency 5-Year Review Site.

State of Colorado. January 2, 2008. Notice of Deletion.

Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988.

Sverdrup. July 1992. Groundwater Monitoring Plan for the Remedial Design at the Denver Radium Site Operable Unit No. 9 Robinson Brick Company-Metals.

Sverdrup. May 1993. Groundwater Contamination Characterization Report for the Remedial Action at the Denver Radium Site Operable Unit No. 9 Robinson Brick Company-Metals.

Sverdrup Corporation. November 1996. Monitoring Well Decommissioning, Installation, and Sampling Report of Perimeter Wells at the Denver Radium Superfund Site Operable Unit No. 9.

UNC Geotech. November 6, 1987. Supplemental Radiological Data for Operable Unit 4/5.

UNC Geotech. December 1988. Denver Radium Site Environmental Air Sampling at Denver Radium Operable Unit 4/5.

URS Consultants. December 7, 1990. Robinson Brick Company Denver, Colorado. Soil Sampling Report October 1990 Sampling. Work Assignment No. 08-8L01.

URS Consultants. January 14, 1991. Focused Feasibility Study Robinson Brick Company Operable Unit 9. Denver, Colorado.

URS Consultants, Inc. July 31, 1991. Robinson Brick Company Focused Feasibility Study Final Report. Work Assignment No. 08-8L01.

URS Operating Services, Inc. July 6, 1998. Analytical Results Report for Denver Radium OU9 (ROBCO) Denver, Colorado Revision 1.

U.S. Environmental Protection Agency. September 30, 1986. Superfund Record of Decision: Denver Radium/ROBCO, CO.

U.S. Environmental Protection Agency. December 29, 1988. John M. Brink, Remedial Project Manager to Tom Stauch, Public Health Engineering Department of Health and Hospitals.

U.S. Environmental Protection Agency. June 18, 1991. Denver Radium Site Operable Units 4 & 5: Remedial Action Completion Report.

U.S. Environmental Protection Agency. June 1995. Supplemental Standards Report, Operable Unit 4.

U.S. Environmental Protection Agency Region 8. July 26, 1995. Agreement and Covenant Not to Sue: Denver Radium Site Operable Units 4 & 9B.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium.

U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site.

Endnotes

1 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets. 2 U.S. Environmental Protection Agency. September 30, 1986. Superfund Record of Decision: Denver Radium/ROBCO, CO. 3 ERM-Rocky Mountain, Inc. December 12, 1994. Subsurface Investigation Robinson Brick Company. 4 RUST Geotech Inc. July 1994. Denver Radium Site Operable Unit 4 and 5 Interim Close Out Report for the U.S. Environmental Protection Agency 5-Year Review Site. 5 ERM-Rocky Mountain, Inc. December 12, 1994. 6 URS Consultants. January 14, 1991. Focused Feasibility Study Robinson Brick Company Operable Unit 9. Denver, Colorado. 7 RUST Geotech Inc. July 1994. 8 U.S. Environmental Protection Agency. September 25, 2006. 9 Federal Register. September 9, 2010 . Vol. 75, No. 174/ Rules and Regulations. 10 U.S. Environmental Protection Agency. September 25, 2006. 11 RUST Geotech Inc. July 1994. 12 CH2M Hill. April 18, 1986. Revised Group IV & V Feasibility Study. 13 U.S. Environmental Protection Agency. September 30, 1986. 14 U.S. Environmental Protection Agency. September 30, 1986. 15 CH2M Hill. April 18, 1986. Revised Group 4 & 5 Feasibility Study. 16 UNC Geotech. November 6, 1987. Supplemental Radiological Data for Operable Unit 4/5. 17 URS Consultants. January 14, 1991. 18 RUST Geotech Inc. July 1994. 19 RUST Geotech Inc. July 1994. 20 U.S. Environmental Protection Agency. June 18, 1991. Denver Radium Site Operable Units 4 & 5: Remedial Action Completion Report. 21 U.S. Environmental Protection Agency. September 25, 2006. 22 RUST Geotech Inc. July 1994. 23 United States Environmental Protection Agency. September 25, 2006. 24 RUST Geotech Inc. July 1994. 25 U.S. Environmental Protection Agency. June 18, 1991 26 RUST Geotech Inc. July 1994. 27 RUST Geotech Inc. July 1994. 28 U.S. Environmental Protection Agency. December 29, 1988. John M. Brink, Remedial Project Manager to Tom Stauch, Public Health Engineering Department of Health and Hospitals. 29 UNC Geotech. December 1988. Denver Radium Site Environmental Air Sampling at Denver Radium Operable Unit 4/5. 30 U.S. Environmental Protection Agency. December 29, 1988. 31 UNC Geotech. December 1988. 32 RUST Geotech Inc. July 1994. 33 RUST Geotech Inc. July 1994. 34 U.S. Environmental Protection Agency. June 1995. Supplemental Standards Report, Operable Unit 4. 35 RUST Geotech Inc. July 1994. 36 Colorado Department of Public Health and Environment. April 14, 2008. Review of Supplemental Standards Report for OU4/5, Docket 8218. Prepared by Philip Egidi. 37 URS Consultants. December 7, 1990. Robinson Brick Company Denver, Colorado. Soil Sampling Report October, 1990 Sampling. Work Assignment No. 08-8L01. 38 ERM-Rocky Mountain, Inc. December 12, 1994. 39 URS Consultants, Inc. July 31, 1991. Robinson Brick Company Focused Feasibility Study Final Report. Work Assignment No. 08-8L01. 40 ERM-Rocky Mountain, Inc. April 1996. Phased Remedial Response Action Closure Report: Phases I, II, and III. Robinson Brick Company 500 South Santa Fe Drive, Denver, Colorado 80223. 41 Morrison Knudsen Corporation. September 29, 1999. Technical Memorandum Materials Left in Place Denver Radium Site.

42 ERM-Rocky Mountain, Inc. December 12, 1994. 43 ERM-Rocky Mountain, Inc. April 1996. 44 Sverdrup. July 1992. Groundwater Monitoring Plan for the Remedial Design at the Denver Radium Site Operable Unit No. 9 Robinson Brick Company-Metals. 45 Sverdrup. May 1993. Groundwater Contamination Characterization Report for the Remedial Action at the Denver Radium Site Operable Unit No. 9 Robinson Brick Company-Metals. 46 Sverdrup. May 1993. 47 Morrison Knudsen Corporation. September 29, 1999. 48 U.S. Environmental Protection Agency Region 8. July 26, 1995. Agreement and Covenant Not to Sue: Denver Radium Site Operable Units 4 & 9B. 49 Morrison Knudsen Corporation. November 20, 1998. Denver Radium Superfund Site Five-Year Review. 50 United States Environmental Protection Agency. September 25, 2006. 51 Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES. 52 Colorado Department of Public Health and Environment. September 30, 2008. Five-Year Review, Denver Radium Site. 53 United States Environmental Protection Agency. May 2012. 54 Colorado Department of Public Health and Environment. September 30, 2008. 55 Morrison Knudsen Corporation. November 20, 1998. 56 United States Environmental Protection Agency. September 25, 2006. 57 Colorado Department of Public Health and Environment. September 30, 2008. 58 State of Colorado. January 2, 2008. Notice of Deletion.

Denver Radium Superfund Site

Operable Unit 6, 9-A, 11 Open Space Properties

Table of Contents: Background Information 72 Remedial Investigation 75 Remedial Objectives/Record of Decision 78 Explanation of Significant Differences 80 Remedial Action 81 Excavation Activities 87 Supplemental Standards 88 Institutional Controls 90 De-listing 90 Bibliography 91 Endnotes 93

Tables and Figures: Table 1: Operable Unit 6 Properties 72 Table 2: Operable Unit 9-A Properties 74 Table 3: Operable Unit 11 Property: 74 Table 4: Remedial Phases of OU-6 81 Table 5: Materials Left in Place as Averaged Areas OU-6 83 Table 6: Materials Left in Place as Averaged Areas OU-9 85

Background Information

Denver Radium Operable Units 6, 9A, and 11 comprised 10 properties known as the “Open Space Properties.” The “Open Space Properties” contain outlying properties involving minor amounts of interior and exterior contamination,1 and are located in proximity to the South Platte River and along the Santa Fe Drive corridor.2 The Open Space Properties were grouped because they all contained contamination in open areas and none involved large, extensively contaminated areas.3

Table 1: Operable Unit 6 Properties:

Property Name at Time of Address Operable Unit ROD OU-6C Allied Chemical and Dye 1271 West Bayaud Avenue Corporation (Allied) OU-6F Brannan Sand and Gravel 47.5 acres between 61st Avenue (Brannan) and Clear Creek OU-6A Colorado and Southern Railroad 2301 15th Street: Adjacent to the (CSRR)/Centennial State Tire South Platte River between 15th and Retread Company and 16th Streets (Centennial Tire) OU-6B Denver Water Department 1190 Yuma Street OU-6D Public Service Company of Adjacent to an electrical Colorado (Public Service) substation at South Pecos and West Arizona Avenue OU-6E Ruby Hill Park Jewell Street and South Platte River Drive OU-6- Alley Alley in City and County of Between Mariposa and Lipan and Denver right-of-way extends between 5th and 6th Avenue OU-6- Environmental Environmental Materials 1155 West 5th Avenue Materials Property Incorporated (Environmental Materials/EMI)

Historical Source of Radiological Contamination:

The contamination discovered at the Centennial Tire, Burlington Northern Railroad, and North Confluence Park properties is believed to be the result of a 1920’s radium processing laboratory. The remaining properties are believed to have become contaminated as a result of radium processing wastes being transported to the properties from various processing sites.4

1271 W. Bayaud Ave. (OU6C): Historically, the property has been used for chemical manufacturing since the late 1800s. Chemicals manufactured at this site included sulfuric, nitric, muriatic acid, blue vitriol, and ammonia.5 The contamination on this property was presumed to be the result of approximately 2 feet of fill carried onto the property from construction sites in downtown Denver during the early 1960s. Approximately 30 feet of alluvium is located under the fill, below which is bedrock (the Denver Formation). The property is within the South Platte River 100-year flood plain. 73

47.5 acres between 61st Avenue and Clear Creek - (OU-6F): The mined-out gravel pit was used as a municipal landfill between 1960 and 1982. In 1982, the pit contained 10 to 15 feet of refuse and was being covered by construction debris (concrete pieces, blocks, and rubble).6 Depth to bedrock is uncertain, and the property is within the Clear Creek 100-year flood plain.

2301 15th Street (OU-6A): The property included a building at 2301 15th Street that was occupied by the National Radium Corporation in 1926 and 1927. The building was believed to be the ore lab and was located on the southeast corner of the Centennial Tire property adjacent to the Burlington Northern Railroad. In order to facilitate the removal of radium contaminated soils present under portions of the building’s thick concrete floor, the building was razed by the owner of the property prior to remedial action.7 Later industrial uses of the 2301 15th property included ore assaying and textile dyeing.8 The property is underlain by approximately 25 feet of fill and alluvium, below which is the Denver Formation. The Confluence Park portion of the property is within the South Platte River 100-year flood plain.

1190 Yuma Street (OU-6B): Denver Water purchased the property in 1937.9 The contamination on this property may have been related to operations from the Schlesinger Radium Company and the Radium Company of Colorado. These companies processed radium-bearing ore on the nearby 1100 Umatilla Street (OU-2). The property is underlain by 30 feet of alluvium, below which is the Denver Formation. This property is not within the South Platte River 100-year flood plain.

Adjacent to an electrical substation at South Pecos and West Arizona Avenue (OU-6D): The source of radiological contamination at this site is unknown. Radiological contamination was detected in fill materials deposited prior to 1979 on the south end of the property. The City of Denver used this property in the past to dump excess fill materials from the Platte River Beautification Project.10 This property is underlain by approximately 8 feet of fill and soil, below which is the Denver Formation. The property is not within the South Platte River 100-year flood plain.

Jewell Street and South Platte River Drive (OU-6E): The source of radiological contamination at this site is unknown. However, aerial photographs from 1948 and 1956 show that portions of the property were used as a landfill. Also, the southeast portion of the park was occupied by an industrial plant during the same time period.11 The depth to bedrock is uncertain, and the property does not lie within the South Platte River 100-year flood plain.

Between Mariposa and Lipan and extends between 5th and 6th Avenue (OU-6-Alley): Initially, the alley was part of OU 7, and the source of radiological contamination is unknown. The alley is underlain by about 30 feet of alluvium, below which is the Denver Formation. The alley is not within the South Platte River 100-year flood plain.

1155 West 5th Avenue (OU-6-EMI): This property was added to OU-6 when contamination was detected on the property in the spring of 1991 due to remediation of the nearby alley. The property was believed to be the site of ore processing between 1908 and 1921. However, no records have been found which list radium or uranium processing on this site.12 A Statement of Work was drafted for Ou-6 Phase C in July 1992, and amendment two of the Superfund State Contract included the remediation of the Environmental Materials, Inc. property as well as the adjacent RTD property.13 The property is underlain by approximately 30 feet of alluvium, below which is the Denver Formation. The property does not lie within the South Platte River 100-year flood plain. 74

Table 2: Operable Unit 9A Properties:

Property Name at Time of Address Operable Unit ROD OU-9-A International House of Pancakes 2001 East Colfax Avenue (IHOP) and Larry’s East Site Amusement Center and Trading Post (now Mama’ s Café, Herbs and Art, and Purple Haze)

Historical Source of Radiological Contamination:

The source of radiological contamination was believed to be a result of operations from Schlesinger Radium Company. Schlesinger Radium Company operated a radium reduction plant at Ou-2 in 1915 and also operated a laboratory at the East Colfax location. The laboratory conducted research, higher fractionation, and radium measurements.1 The building that housed the laboratory was demolished prior to 1950. Another part of the unit was occupied by an apartment complex from 1924 to 1939 and a car sales lot from 1939 until 1962.14 The IHOP restaurant was built in 1965. The other building that housed Larry’s East Side Amusement Center and Trading Post existed at the time of the Schlesinger Radium Co. laboratory, but no contamination was found in the building. Depth of the bedrock, known as the Denver Formation, is approximately 16 feet.

Table 3: Operable Unit 11 Property:

Property Name at Time of Address Operable Unit ROD OU-11 Commercial Investors Realty 1295 South Santa Fe Drive Property

Historical Source of Radiological Contamination:

The source of radiological contamination was related to the processing or handling of radium ore by the Rocky Mountain Radium Products plant located on or near the site. OU-9-A does not lie within the South Platte 100-year flood plain, and the property is underlain by approximately 18 feet of alluvium, below which is the Denver Formation.

In 1983, the former property owner hired Western Radiation Consultants, Inc. (WRC) to conduct a site investigation. WRC confirmed the presence of Ra-226 contaminated soil on the site, specifically, north of the structure, on a side hill west of the billboard, and near South Platte River Drive. The property owners initiated a partial excavation of the contaminated area adjacent to South Platte River Drive. The contaminated soil, gravel, and debris were placed in approximately thirty 30-gallon Type-7A U.S.

1 The Remedial Action Completion Report states that radium contamination at the site resulted from the Cold Light Manufacturing Company which manufactured thousands of luminous dials for military use from 1919-1920. 75

Department of Transportation drums lined with heavy gauge polyethylene. The drums initially were placed on the north side of the 1295 South Santa Fe Drive and subsequently were placed beneath the billboard and covered with a plastic liner wrapped in wire mesh fence.15

In 1988, the Ra-226 contaminated soil that was excavated in 1983 and stored on site in drums was shipped to Las Vegas, Nevada and used in a remedial technology test project.16

Remedial Investigation

EPA released a Remedial Investigation (RI) for OUs 6, 9A, 11 on April 30, 1986, and a Feasibility Study (FS) on August 1, 1987. The RI report focused on radium and uranium processing residues discarded in the early 1900s. These residues contained uranium, radium, and thorium. Radium-226 (Ra-226) was the contaminant of primary concern due to its associated radioactivity (alpha, beta, and gamma radiation emissions of Ra-226 and its daughter isotopes), and its tendency to decay into radon gas, which constitutes the primary health risk associated with residues from processing facilities. 17

The Open Space properties were estimated to have approximately 1,370 yd3 of contaminated soil over an area of 16,902 ft2 at a maximum depth of 56 inches. The volume-weighted average concentration of Ra- 226 in soils on the properties was 100.7 pCi/g. Average Ra-226 measurements in the soil samples ranged from 8 pCi/g at 1190 Yuma Street to 244 pCi/g at the 2301 15th Street. Maximum individual Ra-226 measurements from soil samples ranged from 19 pCi/g at 1190 Yuma Street to 2,775 pCi/g at 2301 15th Street. Average gamma radiation measurements ranged from 7 µR/hr at OU-9-A (Contiguous Property No. 8) to 239 µR/hr at 1190 Yuma Street. There were no elevated levels above EPA standards of radon decay products found in any of the property buildings.

Non-radiological contamination was found at the OU-6C and OU-6A properties. Polynuclear aromatic hydrocarbon compounds were found in soil samples from these properties, and a soil sample from the Allied property exhibited hazardous waste characteristics by exceeding the EP toxicity test limits for lead and mercury.

Radiological Contamination by Operable Unit and Property:

OU-6: Operable Unit 6 contained approximately 848 yds3 of contaminated soil at depths ranging from less than 6 inches to 36 inches. Ra-226 concentrations were identified as high as 2,775 pCi/g.18

1271 W. Bayaud Ave. (OU6C): A total area of 4,320 ft2 on the property was contaminated with approximately 290 yd3 of material. The maximum depth of contamination found at this site was 22 inches, and the maximum gamma radiation reading was 275 µR/hr. The maximum Ra-226 concentrations were identified at 198 pCi/g, and the highest radon decay-product concentration (RDC) value was measured at 0.012 WL.19

Historical aerial photographs indicated potential chemical spills. Soil samples indicated elevated EP toxicity lead and mercury results as well as the presence of polynuclear aromatic hydrocarbons.20 UNC Geotech provided supplemental data for the Allied property in 1989 to identify the real and vertical extent of radium-226 contamination in soils exceeding the applicable or relevant and appropriate standard established by the EPA. The exterior extent of contamination identified was similar to previous reports. Ra-226 concentrations were as high as 102.7 pCi/g at depths ranging from 6 to 33 inches.

47.5 acres between 61st Avenue and Clear Creek - (OU-6F): The most elevated radiation was found over an area of approximately 200 ft2 and included approximately 10 yd3 of contaminated soil. Maximum gamma readings in this contaminated area were 180,000 counts per minute (cpm) at 18 inches and 400,000 cpm at greater than 16 inches.21 The contamination appeared to be a result of hospital waste.22 A 1989 Geotech investigation confirmed that a no-action alternative was appropriate for this property.23

2301 15th Street (OU-6A): Approximately 2,800 ft2 of radiologically contaminated material was identified including approximately 207 yd3 of Ra-226 contaminated soil.24 The maximum radium concentration was 2,775 pCi/g, and the maximum gamma radiation readings were 1,900 µR/hr. Samples indicated the presence of polycyclic aromatic hydrocarbons (PAH’s), possibly from the railroad tracks on the site.25 The 1989 supplemental Geotech investigation indicated that contamination was more extensive than indicated in previous studies, and it identified additional contamination on the north side of the Centennial Tire building. The investigation identified Ra-226 concentrations as high as 290.1 pCi/g at depths ranging from 6 to 90 inches. A deposit of Ra-226 was identified in the basement of the building at 2301 15th Street.26

1190 Yuma Street (OU-6B): Approximately 300 yd3 of contaminated soils was identified beneath approximately 1,500 ft2 at the property. The contamination was dispersed in the fill material beneath 2 inches of asphalt and 4 inches of base material. The maximum radium concentration area was 18.7 pCi/g, and the maximum gamma radiation reading was 800 µR/hr. The volume of contamination was based on an assumed depth between 0 and 5 inches. The 1989 Geotech investigation confirmed the presence of deposits located in previous studies and identified Ra-226 concentrations as high as 254.9 pCi/g at depths ranging from 6 to 15 inches.27

Adjacent to an electrical substation at South Pecos and West Arizona Avenue (OU-6D): Contamination was reported in a 325 ft2 area and approximately 20 yd3 of contaminated soil was identified at a maximum depth of 18 inches. The maximum and average radium concentrations for this property were 54 and 37 pCi/g, respectively.28 The 1988 Geotech investigation identified contamination that was more extensive than indicated in previous studies and identified an additional deposit located south of the original deposit. This investigation identified Ra-226 concentrations as high as 49.1 pCi/g at depths ranging from 6 to 15 inches.29

Jewell Street and South Platte River Drive (OU-6E): Initially, approximately less than 1 yd3 of radioactively contaminated material was detected located within a 1 ft2 area under approximately 4 to 6 inches of clean overburden. No contamination was observed in the buildings, baseball fields, or picnic areas. However, excavation crews found radiation to extend deeper than anticipated. The volume of material was updated to be approximately 10 yd3. The 1989 Geotech investigation confirmed the 77

presence of the deposit described in previous studies and identified Ra-226 concentrations at depths ranging from less than 6 inches to 21 inches.30

Between Mariposa and Lipan and extends between 5th and 6th Avenue (OU-6-Alley): The estimated contaminated area covered approximately 125 ft2 with a maximum surface reading of 29 µR/hr. The 1989 Geotech investigation identified Ra-226 concentrations as high as 63.7 pCi/g at depths ranging from 6 to 33 inches.31

1155 West 5th Avenue (OU-6-EMI): Approximately 600 tons of radium contamination was assessed to be buried both around the existing building and beneath the building located on this property.32

2001 East Colfax Avenue (OU-9A): Operable Unit 9 contained approximately 96 yd3 of contaminated soil at depths up to 50 inches. The contamination only involved exterior areas.33 An additional investigation of OU-9 was conducted by UNC Geotech in February 1989. The results confirmed previously collected data, and Ra-226 concentrations in the soils ranged from 17.0 to 79.0 pCi/g.34

Low-level radioactive material was found to be embedded in two-thirds of the concrete floor slab of the IHOP building. However, alpha radioactivity measurements in the building were not above standards. Thus, subject to remedial design or remedial action, the slab was considered not contaminated.35

1295 South Santa Fe Drive (OU-11): The remedial investigation identified approximately 332 yd3 of contaminated soil at depths ranging from 6 to 30 inches. Concentrations of Ra-226 were found as high as 690 pCi/g. The contamination only involved exterior areas.

1295 South Santa Fe Drive (OU-11): CDH performed an initial field investigation of this property in 1982, and the EPA performed an additional site investigation in 1985. The EPA study divided the 2 property into two sections: Area A1 and Area A2. Area A1 was approximately 1,151 ft with maximum subsurface contamination estimated to be 36 inches deep. The total volume of contaminated soil was estimated to be 130 yd3. The average surface-level gamma radiation measurement was 30.8 µR/hr with a maximum measurement of 76 µR/hr.

2 Area A2 was approximately 5,232 ft with subsurface contamination estimated to be 12 inches deep. The volume of contaminated soil was estimated to be 190 yd3. The average surface-level gamma radiation measurement was 15.3 µR/hr with a maximum measurement of 83 µR/hr.

The 1985 study also noted that the drums from the partial excavation in 1983 were stacked along the northwestern exterior wall of the structure. EPA performed a gamma radiation survey around the perimeter of the drums and exposure rates were found to be approximately 65 µR/hr.36

An additional investigation of OU-11, as directed by the EPA, was conducted by Geotech in 1989. The investigation confirmed the presence of a large deposit of radium-contaminated soil around the billboard and identified an additional deposit north of the billboard. The investigation identified Ra-226 concentrations as high as 199 pCi/g. The investigation also identified two additional areas of suspected contamination—the sidewalk on the northwest side of the building identified in previous surveys and an area in the asphalt west of the building. However, laboratory analyses of samples collected from both locations indicated that these areas were free of Ra-226 contamination.37

Contamination previously identified in the basement could not be located; furthermore, samples from an area of gamma activity slightly above ambient levels were analyzed in the laboratory and found to be free of Ra-226 contamination. The Geotech investigation did not include RDC measurements. This investigation indicated slightly elevated gamma exposure rates of 19 to 21 µR/hr throughout the interior of the building and concluded that these gamma exposure rates and the elevated radon daughter concentration (RDC) values observed in previous studies could have been caused by the masonry materials used in the buildings construction.38

Remedial Objectives/Record of Decision

OU-6: The selected remedy in the September 29, 1987 Record of Decision (ROD) was off-site permanent disposal for the Allied, CSRR/Centennial Tire, Denver Water Department, and Public Service properties, and no action was selected for the Brannan, Ruby Hill Park, and alley properties. If the cost of acquiring additional information and sampling exceeded the cost of remedial action, the EPA would implement a remedial action alternative other than ‘No Action.’

The 1987 ROD called for removal of approximately 1,375 tons of radium-contaminated soil from seven properties. Additional assessment of these properties performed prior to the Remedial Action estimated the contamination to be 2,324 tons. Also, additional assessment showed that the 47.5 acres between 61st Avenue and Clear Creek property was not contaminated.39

The scope of remedial action included:  Determining whether contaminant levels at 47.5 acres between 61st Avenue and Clear Creek, Jewell Street and South Platte River Drive, and alley properties were within the limits specified in 40 CFR 192 to verify that the No Action alternative was appropriate; [The ROD determined that according to the Remedial Investigation, it did not appear that radium contamination in soils on these properties exceeded the target residual levels established in contaminant-specific ARARs for the Open Space Properties.] o For the alley, the EPA recommended: 1. Denver improve existing institutional controls (ICs) so that all routine maintenance, repair, or construction activities in the alley carried out by government agencies, utility companies, contracting companies, private individuals, etc., will be monitored, and, 2. That Denver consider removing or requiring the removal of any contaminated material excavated during routine maintenance, repair, or construction activities in the alley to a facility approved for the storage and disposal of such contaminated material. 79

 Placing a cap over the contaminated material at the 1271 West Bayaud Avenue property and, if necessary, the 47.5 acres between 61st Avenue and Clear Creek and alley properties;  Removing the contaminated material from the 2301 15th Street, 1190 Yuma Street, adjacent to an electrical substation at South Pecos and West Arizona Avenue, and, if necessary, the Jewell Street and South Platte River Drive properties, placing the material in containers, and storing it in a temporary storage facility located at the 1314 West Evans Ave property (OU-10);  Maintaining the temporary storage facility at OU-10 and the containment caps at the 1271 West Bayaud Avenue and, possibly, 47.5 acres between 61st Avenue and Clear Creek and alley properties until a facility suitable for the permanent disposal of Denver Radium wastes became available;  Establishing ICs for maintenance, repair, and construction activities on the alley properties; and;  Transporting the contaminated material from 1271 West Bayaud Avenue, OU-10, and, possibly, the 47.5 acres between 61st Avenue and Clear Creek and alley properties to the off-site permanent disposal facility.

A Statement of Work for OU-6 established the tasks and schedule for implementation of Remedial Design (RD) for Phase C (Environmental Materials, Inc.). The remedy selected included the installation of a radon venting system for the office area on the upper level of the building, demolition of parts of the concrete flooring in the lower levels of the building and the subsequent excavation of contaminated materials, and the excavation of small areas of contaminated soils outside of the building on the site. Additional work included in this remedy was the removal and decontamination of a small underground fuel tank.40

OU-9-A: The selected remedy in the September 29, 1987 ROD included off-site permanent disposal. The scope of remedial action included:

 Clean-up and storage of the contaminated material in the temporary storage facility at OU-10;  Maintaining the temporary storage facility at OU-10 until a facility became available for the permanent disposal of the Denver Radium Site wastes; and,  Final removal of the contaminated material from OU-10 and transported to the offsite permanent disposal facility.

OU-11:

The selected remedy in the September 29, 1987 ROD included off-site permanent disposal. The scope of remedial action included:

 Removing the contaminated material from the property, placing it in containers, and storing it in a temporary storage facility located at the OU-10 site, 1314 West Evans Ave. property;  Maintaining the temporary storage facility at the 1314 West Evans Ave. property until a facility suitable for the permanent disposal of Denver Radium Site waste became available; and  Transporting the contaminated material from the 1314 West Evans Ave. property to the off-site permanent disposal facility. 80

Plans for off-site temporary storage for OU-6,-9A,-11 were abandoned when a permanent disposal facility operated by Envirocare Inc., in Tooele County, Utah became available in 1988.41

The EPA conducted a responsible party search, but the investigation did not reveal that any of the present owners of the Open Space Properties had any record of being connected with the activities that resulted in the contamination.42

An Explanation of Significant Differences (ESD) was issued in January 19, 1995 for OU-6,-9A,-11 to address the following significant differences: 1. Temporary containment was not necessary since an off-site disposal facility became available in 1988. The contaminated material was shipped by rail to the Envirocare of Utah, Inc. disposal facility. 2. Previously identified contamination increased in volume and extended onto an adjacent property at 1155 West 5th Avenue. Surveys indicated that Ra-226 contaminated soils were present both beneath and outside the EMI building. Concentrations of Ra-226 were detected as high as 443.8 pCi/g and at depths ranging from 6 to 78 inches. 3. Small amounts of radium-contaminated soils were left in place on two properties in OU-6 based upon supplemental standards.  15th Street properties: 2301 15th Street (near a concrete box culvert on the Confluence Park property), and  Environmental Materials, Inc.: 1155 West 5th Avenue (under the EMI building).

The two areas of contamination left in place next to the concrete culvert on the Confluence Park property are associated with a layer of gravel to cobble sized “slag” that dips steeply to the East. Further excavation in these areas would have damaged the culvert, which was leaking from several places. The contamination is overlain by five feet of clean backfill and does not pose a risk to human health or the environment.

Contamination was not excavated from under the EMI building since the EPA determined that such action was not necessary for the remedy to be protective and to meet the interior cleanup standards set forth in 40 CFR Section 192.12(b). That section states that in any occupied or habitable building:

I. The objective of remedial action shall be and reasonable effort shall be made to achieve annual radon decay product concentration not exceeding 0.02 WL. The radon decay product concentration in any case, shall not exceed 0.03 WL and, II. The level of gamma radiation shall not exceed the background level by more than 20 microroentgens per hour.

The radon concentrations and gamma radiation levels in the EMI building meet these standards. Supplemental standards and ICs discusses later in this chapter are in place in the above areas.43

Remedial Action

During remedial action for OU-6, -9A, and -11, 8,336 tons of contaminated soil were excavated and disposed offsite.

OU-6: Remediation activities were conducted in four phases beginning in July 1990 and concluding on January 25, 1994. The cleanup work was performed by two contractors: a design/construction contractor (CN Geotech) and a transportation and disposal contractor (Chem Nuclear Environmental Systems, Inc.).44 A total of 4,083 tons of radium-contaminated waste were removed between October 1990 and September 1991. The total quantity of material removed during remediation was 6,936 tons. Reconstructed excavations were topped with at least 15 cm of imported clean fill containing a normal background level of Ra-226. Radiologic contamination was excavated in six-inch lifts in order to minimize the amount of clean material removed with the waste. After a lift was removed, the excavation was surveyed to determine whether it was necessary to remove another lift. Once the soil was analyzed to ensure compliance with regulations applicable to waste transportation, it was shipped to the off-site disposal facility.45

The building at 2301 15th Street was demolished during remedial action activities because it was not structurally sound and could not be remediated safely. A Final Completion Inspection was held at the EMI property on January 25, 1994. The inspection determined that the selected remedy had been constructed in accordance with Remedial Design plans and specifications.46

Table 4: Remedial Phases of OU-6

Phase A 118 tons of contaminated material was July 13, 1990-October 19, 1990 excavated from the Public Service Company vacant lot at South Pecos Street and West Arizona Avenue and disposed off-site. The excavated area was backfilled with clean soil and re-vegetated. Phase B 3,965 tons of material was excavated for off-site March 1, 1991- September 30, 1991 disposal and were transported by rail to the permanent disposal facility in Utah. Phase C 2,403 tons of contaminated soil was excavated from the Environmental Material, Inc. and Regional Transportation District properties and transported by rail to the permanent disposal facility in Utah. Phase D 450 tons of contaminated soil was excavated 1993 from the EMI property and transported by rail to the permanent disposal facility in Utah.

Phase A Remedial Action: Public Service Company- Vacant Lot (1100 South Pecos): A total of 118 tons of radiologically contaminated material was removed from the property from October 4-10, 1990.

Phase B Remedial Action: Alley Property: A total of 635 tons of radiologically contaminated material was excavated from this property.

Allied Chemical Property (1271 West Bayaud Ave): A total of 135 tons of radiologically contaminated material was removed from the property.

Centennial Tire, BNRR, and North Confluence Park (2315 West 15th Ave): This area was characterized by deposits of radiologic contamination near the surface underlain by layers of clean fill, and then underlain by more radiologic contamination. A total of 3,028 tons of radiologically contaminated material was removed from the properties. Two small deposits of contamination were left in place. These small deposits (6.5 tons) are located under a 1930’s vintage gravity water line which is buried approximately 10 feet below the surface, along the western boundary of the North Confluence Park Property.

Denver Water Board- Vacant Lot (1190 Yuma Ct): A total of 139 tons of radiologically contaminated material was removed from the property.

Ruby Hill Park (Jewell at South Platte River Drive): A total of 28 tons of radium contamination was removed in less than 3 days.

Brannan Sand and Gravel (47.5 acres between 61st Avenue and Clear Creek): The property was determined to be uncontaminated.47

Contaminated material was excavated with front-end loaders and track hoes, while field personnel monitored the excavated area for remaining contamination with hand-held radiation detectors. Soil samples were collected and analyzed, and gamma scans and RDC measurements were conducted to verify that excavation activities achieved conformance with the applicable standards.

After the excavation of contaminated materials was completed, soil samples representative of the 6 inch thick soil layer at the bottom of each verification area were collected and blended to form a composite sample for each verification area. All composite samples were analyzed for Ra-226, and at least 10% were analyzed for Th-230, Th-232, and potassium.

Contaminated materials were transported by rail in either railroad gondola cars or bimodal containers to the permanent off-site disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah. Material was loaded directly onto the cars at the site by the contractor. Each gondola car was filled with material and then sealed, surveyed, and decontaminated, as necessary. The bimodal containers were transported by truck to a rail facility and loaded onto flatcars for conveyance to the permanent off-site disposal facility. The gondola cars and bimodal containers were used only for the transportation of wastes from the Denver Radium Site, and each car was labeled “Denver Radium Superfund Waste.” A composite transportation sample was collected from each railcar or container and was analyzed to ensure that the waste material conformed to the acceptance requirements of the disposal facility. A total of 7 truck-mounted, bi-modal containers were loaded and shipped in October 1990 (Phase A), and a total of 13 truck-mounted, bi-modal containers and 42 gondolas were loaded and shipped in the period between April and June 1991 (Phase B).

The metals-contaminated radiological waste that was removed from the Environmental Materials and Allied properties was shipped to the Envirocare of Utah, Inc. facility and disposed of in a segregated, mixed-waste cell.48

Several deposits required area averaging standards due to conditions that precluded safe or cost-effective removal of the contaminated material. Table 5 summarizes the results of the area-averaging calculations.

Table 5: Materials Left in Place as Averaged Areas OU-649

Site Location Area ID Size in Square Averaged Comments Feet Concentration of Ra-226 OU-6 Area A 170 9.5pCi/g Beneath 15th Street near the Colorado and Southern Railroad tracks OU-6 Area B 360 14.4pCi/g Beneath Confluence Park jogging trail near the CSRR tracks OU-6 Area D 595 14.1pCi/g North side of the Environmental Materials building OU-6 Area E 192 10.3pCi/g North side of the Environmental Materials building OU-6 Area F 369 10.8pCi/g West side of the storage yard at the Environmental Materials building OU-6 Area G 10 7.3pCi/g West side of the storage yard at the Environmental Materials building OU-6 Area H 5 8.5pCi/g West side of the Environmental Materials building OU-6 Area I 346 12.4pCi/g Beneath the railroad tracks west of the Environmental Materials building OU-6 Area J 17 6.8pCi/g West side of the Environmental Materials building OU-6 Area K 10 7.8pCi/g South side of the Environmental Materials building 84

Lead in concentrations exceeding RCRA EP toxicity characteristic regulatory levels was detected in 10 composite samples collected at the Environmental Materials property. The composite samples were collected from containers of radiological waste material prepared for transportation. At the request of EPA, Geotech collected four additional samples from areas of radiological contamination on the Environmental Materials property for toxicity-characteristic metals analysis (excluding mercury) using the Toxicity Characteristic Leaching Procedure. Two of the samples exceeded the RCRA toxicity characteristic regulatory limit for lead. A third sample exceeded the RCRA toxicity-characteristic for cadmium.50

The presence of lead and cadmium in the mill tailings on the Environmental Materials property was attributed to radium ore processing operations; therefore, the soil on this property was exempt from RCRA regulation in accordance with 40 CFR 26I.4(b)(7). Two transportation samples collected at the Allied property exceeded the RCRA toxicity characteristic regulatory level for lead. EPA determined that the RCRA exemption, 40 CFR 261.4(b) (7), could not be applied to this property.51

Interior Verification

Ra-226 contaminated soil was excavated from three locations beneath the interior floor slab of the Environmental Materials building to bring the building into conformance with EPA standards. Post- construction RDC measurements averaged 0.018 WL. Gamma scans of the interior indicated gamma exposure rates ranging from 14 to 28 µR/h.52

OU-9-A:

Remediation activities were conducted in March 1991. The International House of Pancakes (IHOP) restaurant located on the 2001 East Colfax Avenue property was closed for a period of six weeks to allow for cleanup activities. Approximately 89 tons of contamination was removed from the interior of the IHOP and 670 tons of contamination was removed from the parking lot located directly east of the IHOP.53 A total of 759 tons2 were excavated and removed from the property.54

Excavation of contaminated material was performed by hand and conveyor belt in interior areas, and backhoe and front-end loader in exterior areas. Removal was directed by field personnel who measured radiation in the excavations with hand-held detectors. Excavation also was guided by soil sample analyses. After the removal of material was completed based on the readings of the field instruments, verification was performed by collecting and analyzing soil samples. Following excavation of contaminated materials, soil samples representative of the 6 inch thick (15-cm) soil layer at the bottom of each verification area were collected and blended to form a composite sample for that verification area. All composite samples were analyzed for Ra-226, Th-232, Th-230, and K-40.

A total of 46 truck-mounted, bi-modal containers were loaded and shipped in March 1991. Once cleanup was complete, the parking lot was backfilled with clean fill and compacted.

Contaminated materials were sealed in containers and delivered by truck to railroad loading areas; the containers were then transported by rail to the permanent off-site disposal storage area. Material was loaded directly into containers at the site by the Geotech subcontractor. Each container was filled with

2 The Operable Unit 9 Interim Close-Out Report states that the total quantity of material removed during remediation was 640 tons. 85

contaminated material and then inspected to ensure that no spillage of waste material occurred. The containers were used only for the transportation of wastes from the Denver Radium Site and were labeled "Denver Radium Superfund Waste" as an added measure of protectiveness. Composite samples were taken from selected containers and were analyzed to ensure that the material was acceptable under the requirements of the disposal facility.

During remediation activities at OU-9A, three areas (Areas A, B, and C) on the unit required the use of area-averaging calculations because of considerations that precluded cost-effective and safe removal of all contaminated material. Table 6 summarizes the results of the area-averaging calculations.

Table 6: Materials Left in Place as Averaged Areas OU-9

Site Location Figure/Area ID Square Feet Averaged Comments Concentration OU-9-A Area A 78 5.7 pCi/g Beneath the foundation footers of the 2001 East Colfax Avenue IHOP building OU-9-A Area B 4 5.7 pCi/g Beneath the foundation footers of the 2001 East Colfax Avenue building OU-9-A Area C 19 5.7 pCi/g Beneath the foundation footers of the 2001 East Colfax Avenue building

OU-11: Remediation activities were conducted beginning in June 1991 and concluding in August 1991. The total quantity of material removed during remediation was approximately 786 tons (approximately 655 yds3). Contaminated material was excavated with front-end loaders while field personnel monitored the excavated area for remaining contamination with hand-held radiation detectors. Soil samples were collected and analyzed to verify that excavation activities achieved conformance with the applicable standards.

Following excavation of contaminated materials, soil samples representative of the 6 inch thick soil layer at the bottom of each verification area were collected and blended to form a composite sample for that verification area. All composite samples were analyzed for Ra-226 and Th-230. Two samples were analyzed for Th-232 and K-40. Th-230 was detected in elevated concentrations in verification areas V-6, V-7, V-8, and V-10. The results of analyses for Th-230 were not available until after the excavation at OU-11 was backfilled. Further Th-230 characterization, conducted in November 1991, indicated only one occurrence ofTh-230 in area V-9 exceeded the proposed limit. The characterization confirmed that Ra- 86

226 concentrations in all locations were in conformance with EPA standards. EPA assessed the health risks associated with the Th-230 contamination left in place at OU-11. This assessment included an evaluation of the modeling results of similar Th-230 occurrences using the RAETRAN computer code. This modeling program predicts the radon flux in a residential structure that might be built over a Th-230 deposit. The RAETRAN results indicated that radon levels in the structure would not exceed current guidelines. EPA concluded that the Th-230 contamination did not present a risk to public health or the environment and further remediation of the property is unnecessary. EPA also determined that Ra-226 concentrations would remain below 15 pCi/g for at least 200 years.

Contaminated materials were transported for disposal in bimodal containers. The contractor loaded material directly into the containers at the site. Each bimodal container was sealed, surveyed, and decontaminated, as necessary, prior to leaving the site. The container were transported by truck to a rail facility and loaded onto flatcars for conveyance to the permanent off-site disposal facility. A total of 46 bimodal containers were loaded and shipped between June and July 1991. The containers were used only for the transportation of wastes from the Denver Radium Site. The loaded cars were labeled "Denver Radium Superfund Waste" as an added measure of protectiveness. A composite sample was collected from every tenth container, or, at a minimum, from one container per day as the containers were loaded. The samples were analyzed to ensure that the material conformed to the acceptance requirements of the disposal facility.

The Ra-226 contaminated soil that was excavated in 1983 and stored on site in drums was shipped to Las Vegas, Nevada, in 1988 and used in a remedial technology test project for low-level radioactive waste by the Department of Energy (DOE).55

Air particulate measurements were collected at two OU-6 properties using Model LV1 low-volume air particulate samplers manufactured by F&J Specialty Products, Inc. Each sampler was contained in an environmentally protected shelter and was connected to a dedicated electrical power outlet. The samplers were operated continuously for seven days at a nominal rate of five liters per minute for twenty-four hours daily. The filters were analyzed by the Geotech analytical laboratory for natural uranium, Th-230, Ra-226, and polonium-210 (Po-210).

EPA has designated 10 CFR 20, Table 11, Column I, as the relevant and appropriate standard for airborne radionuclides. These standards are expressed as concentrations in microcuries per milliliter (µCi/mL) above background as follows:

Natural Uranium……………………….5.0 X10-12 Th-230……………………………………….8.0 x 10-14 Ra-226…………………………………….…3.0 x 10-12 87

Po-210……………………………………...2.0 x 10-11

All airborne radionuclide concentrations measured during the reporting period were below the applicable regulatory standard (10 CFR 20).

Direct external gamma exposure measurements were collected using TMA/Eberline thermoanalytical environmental dosimeters. Each dosimeter was exposed approximately 1 meter above ground level at each sample location and was submitted to TMA/Eberline Thermo Analytical, Inc. for analysis. All gamma exposures measured during the reporting period were below the limit of 100 millirems per year (mrem/yr) above background. The limit above background refers to the recommendations of the National Council on Radiation Protection and Measurements (1977). The background exposure rates for the Denver area range from 130 to 175 mrem/yr (CH2MHill, 1986).

Excavation Activities:

Farmers and Gardeners Ditch During 1994-1995, Walsh Environmental completed construction of the box culvert on the Farmers & Gardeners Ditch between 15th and 16th Streets. Soils were monitored for radiological contamination during the excavation work. All soils excavated which exhibited gamma readings in excess of 25 µR/hr above background level were stockpiled for sampling and laboratory analysis. Elevated gamma radiation were detected in nearly the entire length of the project area from 15th to the point at which the pipe installation connects with the manhole approximately 100 feet beyond (northeast of) 16th Street. A total of approximately 200-250 yd3 of material were excavated and resulted in ten stockpiles stored on private property at a location adjacent to the old 16th Street viaduct between Platte Street and the South Platte River.57 Ra-226 concentrations in the contaminated soils ranged from 2.0 pCi/g to 64 pCi/g.58

In February 1995, GEI Consultants produced a Materials Handling Plan for the radium-contaminated soils excavated during the utility improvement activities at OU-6.59 The soils were contained in 3.5 yd3 steel containers provided by Envirocare of Utah, Inc. and were sealed with crimped steel bands. The containers were secured in a temporary fenced, posted, and locked storage area on City and County of Denver property, 818 Water Street.60 The metal boxes were transported by flatbed trailers to Envirocare of Utah on July 24-25 1996.61 The area where the boxes containing the contaminated soils were temporarily stored was screened for radioactive contamination using a Ludlum Measurements, Inc. Model 19 Micro R Meter Scintillation detector and a Ludlum Measurements, Inc. Model 44-9 Beta and Gamma Count Rate Meter. The results of the survey concluded that 818 Water Street was not affected by radioactive contaminated soils, and the site was cleared for reuse.62 The 2003 Five-Year Review states that no official documentation of these removal actions were found in site files.63 In January 2004, a 88

gamma survey was conducted to resolve the undocumented removal action. The gamma survey confirmed all the waste was removed from this location.64

Commons Park West In 1998, Phoenix Contractors, Inc. proposed the development of Park Commons West along the 1500 and 1600 blocks of Platte Street.65 Based on the radium-contaminated material excavated during the construction of the Farmer’s and Gardener’s Ditch into a box culvert and the review of preliminary plans for the Commons Park West Planned Unit Development, Denver Environmental Services identified proposed storm-drain easements that could bisect known radium-contaminated soils. Also, the City Engineer’s Office planned to demolish the existing 16th street bridge structure over the South Platte River to replace it with a new pedestrian bridge.

On January 23-24, 1998 and on June 10th-18th, 1998, soil sampling was conducted in the vicinity of the 16th Street Bridge on the west bank of the Platte River from 15th Street to 16th Street. The results indicated elevated alpha-radium level of 22.8 pCi/g in one of ten samples collected.66

During the construction of the storm sewer pipe at the Commons Park West property, Phoenix Development Company, Inc. retained Slosky & Company, Inc. to implement radiological surveillance during excavation activities. Approximately 0.2 cubic meters from two locations was identified as potentially exceeding the site-specific soil action level for off-site disposal. The potentially contaminated soils were segregated in a secured holding area pending quantitative analysis. Laboratory analysis of the segregated soils demonstrated that the soils were below the established soil action level of 7.0 pCi/g and therefore, the soils were used as clean fill on the project site. Less than eight cubic meters of soils contaminated with petroleum hydrocarbons were identified, and the petroleum contaminated soils were disposed at the Waste Management, Inc., Denver Area Disposal Site on September 22, 1998.67

Supplemental Standards

Voluntary Clean Up Plan (VCUP)

On January 3, 2011, a VCUP Application was submitted on behalf of Provendor, LLC. to the Colorado Department of Public Health and Environment pursuant to C.R.S. 25-16-307(2) of the Colorado Voluntary Cleanup and Redevelopment Act for OU-9A. The Petition was submitted for the property identified in the Petition and listed here generally as the 2001 East Colfax Avenue Site, Denver, Denver County, Colorado.

CDPHE approved the request for a No Action Determination based on the following two requirements for proper implementation:

 Installation of a passive sub-slab ventilation system on any new construction; and

 Upon removal of the existing building, the building owner or developer should act on the opportunity to remove the three areas of residual radium contamination left in place under the existing building footers. Due to the potential for changing health based regulatory cleanup standards, CDPHE advises that these three areas be removed. 89

Based on the information provided by Provendor, LLC concerning 2001 East Colfax Avenue property it is the opinion of CDPHE that no further action is required to assure that theis property is protective of existing and proposed uses and does not pose an unacceptable risk to human health or the environment at the site, when used for commercial use.

Under the commercial use proposed by this petition, the use of the property shall comply with all applicable federal, state, and local laws or regulations, including all necessary approvals or permits to conduct all activities envisioned under the proposed land use. The Department makes no representation with respect to approvals of permits required by federal, state, or local laws or regulations, other than the Voluntary Cleanup and Redevelopment Act.68

The EPA criteria for determining that conditions in a given instance warrant a deviation from usual remedial action procedures are known as supplemental standards for remedial action under the regulations set forth in the National Contingency Plan, 40 CFR Section 192.22. A supplemental standards report for OU-6 was completed in June 1995 to document the location and rationale for leaving approximately 53 yd3 of radium contamination including the 2301 15th Street property.

The supplemental standards report explains areas adjacent to the railroad tracks where contaminated soils were left in place and the area comprised of two deposits of Ra-226 contamination next to the concrete culvert on the Confluence Park property. The contamination is associated with a layer of gravel- to cobble-size “slag” that dips steeply to the east. Further excavation in these areas would have placed the culvert, which was leaking from several locations, at risk. Seven samples were taken from the contamination exposed in the excavation floor and walls. Concentrations of Ra-226 ranged from 28 to 153 pCi/g at depths from five to nine feet. Radon decay-product concentrations were not applicable because no habitable enclosed structure is located with the immediate vicinity where the two deposits of contamination was left in place near the concrete box culvert. The contamination was overlain by five feet of clean backfill.

The conditions at OU-6 met criterion (c) of 40 CFR Section 192.21 which addresses the unreasonably high cost of remedial action relative to the long-term benefits. At the time of the report, remediation of the estimated 53 yd3 of contaminated material would cost approximately $125,000 for an average cost $2,400 per cubic yard of. Additional costs may occur for repairing or replacing the concrete box culvert if it were damaged by removing the contamination. The rationale for leaving the material in place is explained by the semi-permanent location of the contaminants and the difficulty of removal. Finally, the materials do not pose a risk to human health or environmental hazard. Therefore, the materials satisfy the requirements of criteria (c), and the use of supplemental standards was permitted.

Areas where waste material was left in place with Supplemental Standards in accordance with 40 CFR Part 192, Subpart C, require the maintenance of Institutional Controls (ICs) and do not allow for unrestricted use and unrestricted exposure. IC plans must require that property owners use best efforts to maintain current zoning and prevent changes to land use. IC plans are in place to ensure protectiveness of human health and the environment.69

Institutional Controls

As an IC required by the ROD, the alley between Mariposa and Lipan Streets (5th and 6th Ave), was included in the Management Plan for OU-7. However, Denver Alley right-of-way within OU-6 was remediated in 2005 and no longer requires restrictions.

Denver Ordinance No. 688-13 provides ICs at properties where radium-contaminated soil remains in place under supplemental standards. The Denver Revised Municipal Code, Chapter 48 [Solid Waste], Article VIII [Disposal fees]70 creates a special zoning for these properties and prohibits disposal of the materials in Denver without paying a fee. The City will charge $5.10/cubic foot of radioactive waste or radium-contaminated material to any person disposing or implementing a remedial control of the above material, unless the disposal is incidental to installation, maintenance, repair, improvement, or replacement of utilities, streets, sidewalks, or alleys in public rights-of-way.71

De-listing

Remedial action at OU-9A and OU-11 removed all contamination, and these properties are available for unlimited use and unrestricted access. Pursuant to Section 121(c) of CERCLA, a Five-Year Review is not required.

A site visit for the 2003 Five-Year review revealed that the Centennial Tire building (2301 15th Street) was demolished, and the construction of luxury apartments was completed. Denver indicated the owner had consulted with Denver and precautions were taken during the excavation to identify potential contamination. In 2003, all properties at OU-6, OU-9A, and OU-11 (except for 2301 15th Street) were recommended for deletion from the Denver Radium Site and the NPL.

On November 4, 2005, Denver submitted an application to the United States Environmental Protection Agency (EPA) to request de-listing of street segments in Ou-6 from the NPL to allow unrestricted routine and emergency street maintenance and repair. The subject street segment/alley in OU-6 was 2301 15th Street. Clean confirmation soil samples were collected and analyzed for Ra-226 by Eberline Services in Oak Ridge, Tennessee using gamma spectroscopy.72

A Final Close-Out Report was signed on September 27, 2006.73 In a letter dated January 2, 2008, the State of Colorado concurred with the EPA’s intent state in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.74 On November 8, 2010 the direct final partial deletion of the Denver Radium Superfund Site from the NPL became final, and all of OU-6, 9-A, and -11 of the Denver Radium Superfund Site was deleted from the NPL. Operations and Management is, by statute, the responsibility of the State of Colorado and is required at 2301 East 15th Street, a property on OU-6.75

Bibliography

CH2MHill. August 1987. Feasibility Study Denver Radium Site Open Space Properties (Operable Units 6, 9, 11).

City and County of Denver. Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES.

City and County of Denver (E.K.Demos). November 18, 1996. Notice of Transportation and Disposal of Radioactive Soils Excavated at Operable Unit 6 of the Denver Radium Superfund Site.

City and County of Denver (John Student). March 31, 1998. Re: Proposed Commons Park West, 1548- 1670 Platte Street—planned utility excavation across Denver Radium OU-6.

City and County of Denver. November 4, 2005. RE: Application for De-listing of OU-2 and OU-6 Denver Radium Site Denver, Colorado.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

E.T. Technologies. February 23, 1996. Generator’s Transportation and Shipping Plan: City and County of Denver NORM Contaminated Soils.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

GEI Consultants, Inc. February 1995. Materials Handling Plan for Radium Contaminated Soils Excavated During Utility Improvement Activities at Operable Unit 6- Denver Superfund Site.

Morrison Knudsen Corporation. November 20, 1998. Denver Radium Superfund Site Five-Year Review.

RUST Geotech Inc. November 1993. Denver Radium Site Operable Unit 9 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

RUST Geotech Inc. June 1994. Denver Radium Site Operable Unit 6 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site.

Slosky and Company, Inc. May 11, 1998. Site Health and Safety Plan: Park Commons West Storm Sewer Installation.

State of Colorado. January 2, 2008. Notice of Deletion.

Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988.

UNC Geotech. January 1989. Denver Radium Site: Operable Unit 2, Phase A, Operable Unit 6, Phase A. Final Design of Remedial Action. 92

U.S. Environmental Protection Agency. September 29, 1987. Record of Decision: Open Space Properties.

U.S. Environmental Protection Agency. September 30, 1991. Remedial Action Completion Report. Operable Unit 9.

U.S. Environmental Protection Agency. September 30, 1991. Remedial Action Completion Report. Operable Unit 6.

U.S. Environmental Protection Agency. July 1992. Statement of Work. Denver Radium Site, OU 6 Environmental Materials, Inc. Remedial Action.

U.S. Environmental Protection Agency. March 30, 1994. Remedial Action Completion Report. Denver Radium Superfund Site Operable Unit 6- Phase D.

U.S. Environmental Protection Agency. January 1995. Explanation of Significant Differences: Denver Radium Site Operable Units 6, 9, & 11.

U.S. Environmental Protection Agency. June 1995. Supplemental Standards Report Operable Unit 6, 15th Street Property.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Superfund Site.

Walsh Environmental. January 3, 1995. Results of Soil Sampling from F&G Pipe Excavation Platte River Improvements Project.

Endnotes

1 RUST Geotech Inc. June 1994. Denver Radium Site Operable Unit 6 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 2 U.S. Environmental Protection Agency. January 1995. Explanation of Significant Differences Denver Radium Site Operable Units 6, 9, & 11. 3 CH2MHill. August 1987. Feasibility Study Denver Radium Site Open Space Properties (Operable Units 6, 9, 11). 4U.S. Environmental Protection Agency. September 30, 1991. Remedial Action Completion Report. Operable Unit 6. 5 CH2MHill. August 1987. 6 CH2MHill. August 1987. 7 U.S. Environmental Protection Agency. September 30, 1991. 8 CH2MHill. August 1987. 9 CH2MHill. August 1987. 10 UNC Geotech. January 1989. Denver Radium Site: Operable Unit 2, Phase A, Operable Unit 6, Phase A. Final Design of Remedial Action. 11 CH2MHill. August 1987. 12 U.S. Environmental Protection Agency. September 30, 1991. 13 Superfund State Contract for Remedial Implementation at the Denver Radium NPL Site between the U.S. Environmental Protection Agency and the Colorado Department of Health. May 1, 1988 14 RUST Geotech Inc. November 1993. Denver Radium Site Operable Unit 9 Interim Closeout Report for the U.S. Environmental Protection Agency 5-Year Review Site. 15 CH2MHill. August 1987 16 U.S. Environmental Protection Agency. April 1994. Operable Unit 11 Closeout Report: Denver Raium 17U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium 18 RUST Geotech Inc. June 1994. 19 RUST Geotech Inc. June 1994. 20 CH2MHill. August 1987. 21 CH2MHill. August 1987. 22 RUST Geotech Inc. June 1994. 23 RUST Geotech Inc. June 1994. 24 RUSTGeotech Inc. June 1994. 25 CH2MHill. August 1987. 26 RUST Geotech Inc. June 1994. 27 RUST Geotech Inc. June 1994 28 CH2MHill. August 1987. 29 RUST Geotech Inc. June 1994 30 RUST Geotech Inc. June 1994 31 RUST Geotech Inc. June 1994 32 U.S. Environmental Protection Agency. September 30, 1991. 33 RUST Geotech Inc. June 1994 34 RUST Geotech Inc. June 1994 35 CH2MHill. August 1987. 36 CH2MHill. August 1987. 37 RUST Geotech Inc. November 1993. 38 RUST Geotech Inc. April 1994. 39 U.S. Environmental Protection Agency. September 30, 1991. 40 U.S. Environmental Protection Agency. July 1992. Statement of Work. Denver Radium Site, OU 6 Environmental Materials, Inc Remedial Action. 41 RUST Geotech Inc. April 1994. 42 U.S. Environmental Protection Agency. September 29, 1987. Record of Decision: Open Space Properties. 43 U.S. Environmental Protection Agency. January 19, 1995. 44 U.S. Environmental Protection Agency. September 30, 1991. 45 U.S. Environmental Protection Agency. September 30, 1991. 94

46 U.S. Environmental Protection Agency. March 30, 1994. Remedial Action Completion Report. Denver Radium Superfund Site Operable Unit 6- Phase D. 47 U.S. Environmental Protection Agency. September 30, 1991. 48 RUST Geotech Inc. June 1994 49 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium. 50 RUST Geotech Inc. June 1994 51 RUST Geotech Inc. June 1994 52 RUST Geotech Inc. June 1994 53 U.S. Environmental Protection Agency. September 25, 2006. 54 U.S. Environmental Protection Agency. September 30, 1991. Remedial Action Completion Report. Operable Unit 9. 55 RUST Geotech Inc. November 1993. 56 RUST Geotech Inc. April 1994 57 Walsh Environmental. January 3, 1995. Results of Soil Sampling from F&G Pipe Excavation Platte River Improvements Project. 58 GEI Consultants, Inc. February 1995. Materials Handling Plan for Radium Contaminated Soils Excavated During Utility Improvement Activities at Operable Unit 6- Denver Superfund Site. 59 GEI Consultants, Inc. February 1995. 60 E.T. Technologies. February 23, 1996. Generator’s Transportation and Shipping Plan: City and County of Denver NORM Contaminated Soils. 61 Morrison Knudsen Corporation. November 20, 1998. Denver Radium Superfund Site Five-Year Review. 62 City and County of Denver (E.K.Demos). November 18, 1996. Re: Notice of Transportation and Disposal of Radioactive Soils Excavated at Operable Unit VI of the Denver Radium Superfund Site. 63 Colorado Department of Public Health and Environment, 2003. Five-Year Review, Denver Radium Site. September 30, 2003. 64 Colorado Department of Public Health and Environment, 2008. Five-Year Review, Denver Radium Site. September 30, 2008. 65 Slosky and Company, Inc. May 11, 1998. Site Health and Safety Plan: Park Commons West Storm Sewer Installation. 66 City and County of Denver (John Student). March 31, 1998. Re: Proposed Commons Park West, 1548-1670 Platte Street—planned utility excavation across Denver Radium OU-6. 67 Slosky & Company, Inc. October 1998. 68 Colorado Department of Public Health and Environment, July 11, 2013. No Action Determination Approval – Voluntary Cleanup Plan Approval for (File : RV110103-1) 2001 East Colfax Avenue Site, Denver, Denver County, Colorado. 69 United States Environmental Protection Agency. June 1995. Supplemental Standards Report Operable Unit 6, 15th Street Property. 70 Denver, Colorado, Code of Ordinances, TITLE II - REVISED MUNICIPAL CODE, Chapter 48 - SOLID WASTE , ARTICLE VIII. - DISPOSAL FEES. 71 Colorado Department of Public Health and Environment. September 30, 2008. 72 City and County of Denver. November 4, 2005. RE: Application for De-listing of OU-II and OU-VI Denver Radium Site Denver, Colorado. 73 Colorado Department of Public Health and Environment. September 30, 2008. 74 State of Colorado. January 2, 2008. Notice of Deletion 75 Colorado Department of Public Health and Environment. September 30, 2003. 95

Denver Radium Superfund Site

Operable Unit 7 Denver Radium Streets

Table of Contents: Background Information 96 Remedial Investigation 97 Remedial Objectives/Record of Decision 100 Explanation of Significant Differences 101 Remedial Action 102 Management Plan 102 Radioactive Materials License 103 Quarterly Reports 103 Deer Trail Regional Facility 103 Storage and Permanent Off-site Disposal Activities 104 Denver Radium Streets 107 2002 Denver Radium Pilot Study 107 2003 Denver Street Replacement Activities 108 2004 Denver Street Replacement Activities 110 2005 Denver Street Replacement Activities 111 2006 Denver Street Replacement Activities 111 2007 Denver Street Replacement Activities 111 De-listing 115 Bibliography 116 Endnotes 120

Tables and Figures: Table 1: Operable Unit 7 Properties 96 Table 2: Radium Concentration: Denver Radium Streets 99 Table 3: Storage and Permanent Off-site Disposal Activities 100 Table 4: Radium Waste Disposal 2003-2007 107 Table 5: Quantity of materials saw-cut, removed, and disposed of: 108 Table 6: Quantity of materials saw-cut, removed, and disposed of: 109 Table 7: 2003 Radium Streets Exportation Summary 109 Table 8: 2007 Radium Streets Exportation Summary 112 Table 9: Denver Radium Street Implementation 115 Figure 1: Project Location Map 109 Figure 2: Project Location Map 110 Figure 3-6: Project Location Map 113-114

Background Information

Denver Radium Operable Unit 7(OU-7), known as ‘Radium Streets,’ consisted of nine street segments containing Radium-226 (Ra-226) contaminated asphalt. The nine contaminated street segments were owned by Denver and extended approximately 4.5 miles through largely residential areas. At the time of the Record of Decision (ROD) published in 1986, it was estimated that 800 residential properties bordered the contaminated street segments. The majority of the contaminated streets were confined near Cheesman Park with the exception of 23rd Street located 1.5 miles northwest of Cheesman Park. Radioactive materials did not extend beyond the paved right-of-way of the streets onto any private or public properties.1 It was estimated that 38,500 cubic yards (yds3) of radium-contaminated material was contained within OU-7, covering approximately 832,000 square feet. Maximum concentrations of Ra- 226 ranged from 4 to 79 picocuries per gram (pCi/g). 2

The radium contamination contained in the street segments likely was a result of road paving operations occurring in Denver during the 1920s. Radium processing was discontinued in Denver in the late 1920s, and the tailing piles were abandoned. Radium-contaminated aggregates were incorporated into asphaltic concrete pavement and used as fill and aggregate in street construction. However, the exact source of the contaminated aggregates is unknown. The impacted areas of OU-7 generally contained a 4-to-6 inch layer of radium-contaminated asphalt underlain by compacted gravel road base. Typically, the street segments were overlain by 4-to-12 inches of uncontaminated asphalt pavement.3

Table 1: Operable Unit 7 Properties4,5

Operable Unit Property Name at Time Estimated Date of Road Date of Removal as Part of of ROD Paving6 the Radium Streets Program OU-7 9th Avenue: from Ogden 1924: Capitol Hill Paving 2007 St. to Cheesman Park (5.5 District No. 2 blocks, 80,000 ft2) OU-7 11th Avenue: from Josephine Street to 1922: Capitol Hill Paving 2003 Cheesman Park (4.5 District No. 8 blocks, 60,000 ft2) OU-7 23rd Street: from California Street to unknown 2007 Lawrence St. (6 blocks, 120,000 ft2) OU-7 Corona Street: from 7th 1924: Capitol Hill Paving Avenue to 10th Avenue (3 2007 District No. 2 blocks, 80,000 ft2) OU-7 Downing Street: from 7th 1924: Capitol Hill Paving Avenue to 10th Avenue (3 2005 District No. 2 blocks, 80,000 ft2) OU-7 Humboldt St: from 7th 1924: Capitol Hill Paving Avenue to 9th Avenue (2 2004 District No. 2 blocks, 52,000 ft2)

Operable Unit Property Name at Time Estimated Date of Road Date of Removal as Part of of ROD Paving7 the Radium Streets Program OU-7 Lafayette St: from 1st 1922: Capitol Hill Paving Avenue to 10th Avenue (9 2004 District No. 4 blocks, 180,000 ft2) OU-7 Marion Street: from 6th 1922: Washington Park Avenue to 10th Avenue (4 2003 Paving District No. 2 blocks, 100,000 ft2) OU-7 York Street: from 6th 1925: Capitol Hill Paving Avenue to 13th Avenue (7 2007 Districts No. 5 and 6 blocks, 80,000 ft2)

Other streets underlain with Ra-226 contaminated soils were identified during remedial action. The street segments are as follows:

South Jason Street between South Platte River Drive and West Louisiana Avenue South Platte River Drive in the block immediately west of South Jason Street Alley Property east of Yuma Street in an alley between the 2300 West 11th Avenue property and 1600 West 12th Avenue property

The contamination under South Platte River Drive and South Jason Street are related to radium and vanadium extraction activities conducted by Chemical Products Company at the OU-3 site.8

Remedial Investigation

In September 1981, the, Colorado Department of Public Health and Environment (CDPHE) contracted with ARIX, a consultant, to perform engineering assessments and to prepare remedial action plans. Among other sites, ARIX assessed the nine street segments and one alley (between Lipan Street and Mariposa Street extending from 5th Avenue to 6th Avenue). Radiological surveys were performed from sidewalk to curb on both sides of the streets and across the full width of the streets. One borehole exploration was performed at the southeast corner of the intersection of 11th Avenue and Gaylord Street. Approximately 95 percent of the 45 blocks included in OU-7 were underlain with radioactively contaminated asphalt pavement. The report concluded that health risks were minimal unless the material was disturbed via street renovation or access to buried utilities. The remedial action suggested that departments inform the appropriate agency when planning construction activities that would disturb the underlying radioactive asphalt pavement.9

The 1985 draft Feasibility Study conducted by CH2MHill compiled a detailed description of each street and its contamination levels based on the data obtained from the 1982 study completed by ARIX. No final Feasibility Study was released.

9th Avenue: Elevated gamma anomalies extended from the west edge of Cheesman Park to the west side of the 9th Avenue/Ogden Street intersection. The length of contaminated street was approximately 2,000 feet, and the area of pavement was approximately 80,000 square feet. Forty-six percent of the street had gamma radiation levels above 20 µR/hr above background. Gamma radiation levels above 40 µR/hr 98

above background were only reported for 2 percent of the area, and the maximum reading reported was 57 µR/hr above background.

11th Avenue: Elevated gamma anomalies extended from the west side of the intersection of 11th Avenue and Josephine Street to the east edge of Cheesman Park. The length of contaminated street was approximately 1,500 feet and the area of pavement was approximately 60,000 square feet. Forty-eight percent of the street area was reported to have gamma radiation levels between 20 and 40 µR/hr above background. No gamma levels above 50 µR/hr above background were reported. Radium concentrations at representative locations on 11th Avenue from Josephine to Race Street ranged from 14 to 84 pCi/g.

23rd Street: Elevated gamma anomalies extended from the southeast side of the intersection of 23rd and California Streets to the southeast side of the 23rd and Lawrence Street intersection. The area of contamination of the street was approximately 120,000 square feet. Only 7 percent of 23rd Street was reported to have gamma radiation levels above 20 µR/hr above background. The highest gamma level reported was 23 µR/hr above background.

Corona Street: Elevated gamma anomalies extended from the north side of the Corona Street and 7th Avenue intersection to the south side of Corona Street and 10th Avenue intersection. The 8th Avenue intersection did not show contamination. The length of contaminated street was approximately 2,000 feet, and the area was approximately 80,000 square feet. Twenty-seven percent of Corona Street was reported to have gamma levels over 20 µR/hr above background, and the highest gamma level reported was 29 µR/hr above background.

Downing Street: Elevated gamma anomalies extended from the north side of the Downing Street and 7th Avenue intersection to the south side of the Downing Street and 10th Avenue intersection. No elevated gamma anomalies were found at the intersection of Downing Street and 8th Avenue, and this intersection was excluded from the contaminated areas. The length of the contaminated street was approximately 2,000 feet, and the area was approximately 80,000 square feet. Sixteen percent of Downing Street was reported to have gamma levels above 20 µR/hr above background, and the highest gamma level reported was 34 µR/hr above background.

Humboldt Street: Elevated gamma anomalies extended from the north side of the Humboldt Street and 7th Avenue intersection to the north side of the Humboldt Street and 9th Avenue intersection. No elevated gamma anomalies were found at the 8th Avenue intersection. The length of the contaminated street was approximately 1,300 feet, and the area was approximately 52,000 square feet. Forty-four percent of Humboldt Street was reported to have gamma levels above 20 µR/hr above background, and the highest gamma level reported was 40 µR/hr above background. The area of contaminated asphalt was approximately 2,700 square yards.

Lafayette Street: Elevated gamma anomalies extended from the north side of the Lafayette Street and 1st Avenue intersection to the south side of the Lafayette Street and 10th Avenue intersection. No elevated gamma anomalies were found at the 3rd, 6th, 7th, and 8th Avenue intersections. The length of the contaminated street was approximately 4,500 feet, and the area was approximately 180,000 square feet. Forty percent of Lafayette Street was reported to have gamma levels between 20 and 40 µR/hr above background. Less than one percent was above 40 µR/hr, and the maximum level reported was 51 µR/hr above background. The area of contaminated asphalt was approximately 13,845 square yards. 99

Marion Street: Elevated gamma anomalies extended from the north side of the Marion Street and 6th Avenue intersection to the south side of the Marion and 10th Avenue intersection. No elevated gamma anomalies were found at the 6th, 7th, and 8th Avenue intersections. The length of the contaminated street was approximately 2,500 feet, and the area was approximately 100,000 square feet. Sixty-seven percent of Marion Street was reported to have gamma levels between 20 and 40 µR/hr above background. Three percent was above 40 µR/hr, and the maximum level reported was 51 µR/hr above background.

York Street: Elevated gamma anomalies extended from the north side of the York Street and 6th Avenue intersection to the south side of the York and 13th Avenue intersection. No elevated gamma anomalies were found at the northern half of the 7th Avenue intersection, the 9th Avenue intersection, or the section of York Street from 9th Avenue to approximately 10th Avenue. The length of the contaminated street was approximately 4,000 feet, and the area was approximately 80,000 square feet. Thirty percent of Marion Street was reported to have gamma levels between 20 and 40 µR/hr above background. Less than one percent was reported above 40 µR/hr, and the maximum level reported was 57 µR/hr above background.10

In June 1985, the EPA placed twelve borings in the various contaminated streets to confirm the depth and thickness of contamination and to determine the radium concentration. Results showed that the majority of contamination was within 6 inches of the surface. However, three locations indicated contamination 12, 16, and 18 inches from the surface. Maximum contamination levels in the borings ranged from 4 to 79 pCi/g.11

Table 2: Radium Concentration: Denver Radium Streets12

Boring Location Contamination1 Pavement Maximum Number Depth (inches) Thickness Radium (inches) Concentration (pCi/g) 1 York St. near 7th Ave 10 12 54 2 York St. near 11th Ave 10 10 26 3 11th Ave near Race St. 16 4 38 4 9th Ave near Cheesman -- 5.5 12 Park 5 Humboldt St. near 7th 5 5 52 Ave 6 Downing St. near 10th 6 6 79 Ave 7 Marion St. near 8th Ave 6 6 16 8 23rd St. near California 6 6 8 St. 9 23rd St. near Lawrence -- 10.5 4 St. 10 7th Ave near Marion St. -- 6 4

1 Contamination was defined as a 6 inch layer of surface material with greater than 5 pCi/g radium concentration or a 6 inch layer of subsurface material with greater than 15 pCi/g radium concentration. 100

11 Lafayette St. near 1st 6 6 19 Ave 12 Lafayette St. near 5th 12 6 70 Ave

In March 1996, GEI Consultants, Inc. surveyed and estimated the potential volume of contaminated asphalt in OU-7.

Table 3: Contaminated Material Volume Estimate, Denver Radium Site Streets13

STREET Volume of Contaminated Material: Top Four Inches (cubic feet) Corona 1,458 Downing 3,596 Marion 14,756 Lafayette 25,915 Humboldt 4,887 York 5,576 9th Avenue 4,396 11th Avenue 8,675 23rd Avenue 9,069 TOTALS 78,328

Remedial Objectives/Record of Decision (ROD)

The ROD published March 24, 1986 determined that the radium contamination in the Denver Radium Streets posed a minimal threat to public health. The rationale was based on the indication that the material was bound in the asphalt and was not free to move in any direction. None of the streets were near surface water or ground-water resources, and the material had little potential for erosion or leaching due to the pavement capping. Contamination of the surface water or groundwater was not determined to be a potential exposure pathway.

Therefore, the selected remedy by the EPA combined features of excavation and disposal with the ‘Modified No Action Alternative.’ The costs of other alternatives, such as limited excavation and disposal or asphalt shielding, were not justified due to high costs and a marginal reduction in risk.

Modified No Action Alternative: The contaminated material would be left in place, and institutional controls (ICs) would be established to monitor all routine maintenance, repair, or construction activities

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occurring in the affected streets. This alternative was determined to limit the public health risk by preventing the spread of the contamination to areas where it could potentially enter pathways of exposure that would increase public health risks.

The operation and maintenance activities required to ensure the effectiveness of the remedy were

1. Excavation controls, and 2. Recommended provisions for disposal of contaminated material removed during routine maintenance, repair, or construction activities in the streets.

The future remedial activities that were required to complete the site response were:

1. Design of ICs: A detailed analysis of the required activities to establish improved ICs needed to be completed. 2. Selection of a disposal facility: A facility for the proper disposal of any contaminated material removed during normal maintenance and repair activities needed to be selected.

A responsible party search was conducted, and financially viable, present-day successors of the paving contractors who were thought to have used the contaminated asphalt were not identified. In response, the EPA viewed the Denver Radium Streets as a fund-lead site, meaning the Superfund monies would need to be used to remediate the site, because responsible parties were not identified. However, the EPA determined that since the streets were owned by Denver at the time of disposal, a minimum of 50 percent cost-share responsibilities, imposed by CERCLA Section 104(c)(3)(C)(ii), would apply to Denver. Also, Denver was considered a responsible party under CERCLA Section 107(a)(1) by virtue of its current ownership of the streets.14 The EPA determined that the State of Colorado or subdivision thereof, such as Denver, should be responsible for all operation and maintenance costs including the costs of the ongoing program to dispose of contaminated material removed during street excavations. The ROD also stipulated that the design of ICs and the selection of a disposal facility must be completed to fulfill the remedial action requirements.15

Explanation of Significant Differences

On September 15, 1992, the EPA released a report to explain the significant differences between the remedy selected in the 1986 ROD, and the remedy which was planned to be implemented. As stated in the ROD, due to the low levels of radioactive contamination at OU-7, no remedial activities were planned unless maintenance, repair, or other construction activities were required. In this instance, the original ROD determined that the excavated material was to be removed to an off-site disposal facility approved for storage or disposal of radium-contaminated material.

However, the significant difference to the remedy stated that the excavated radium-contaminated materials were to be retained and reburied on-site, if feasible, provided that the area to be excavated was not greater than 20 percent of the total area of the roadway in one city block. The 20 percent figure was based on the assumption that all maintenance, repairs, or other construction activity could be successfully performed without excavation of more than 20 percent of the total area of the street. The location of the radium-contaminated asphalt reburied on-site would be permanently documented by the implementing agency. The reburied material was to be covered with a new, hard surface, such as asphalt or concrete, 102

having a minimum depth of 6 inches to ensure no direct exposure. Only if retention and reburial was not feasible, the materials would be disposed of at a licensed, off-site disposal facility, consistent with the ROD. A variance to the 20 percent guideline could be granted by the Colorado Department of Public Health and the Environment (CDPHE). The modified remedy sought to reduce the need to transport contaminated material and the risk associated with such transport.16

In 1994, the EPA released a minor change to the ROD involving the inclusion of the contaminated “Alley Property” into OU-7 (previously a portion of OU-2). The property was located east of Yuma Street in an alley between the Colorado Department of Transportation’s Jerome Park maintenance yard and property owned by the Denver Water Department. Ra-226 contamination was found at a depth of 6 to 12 inches at a concentration up to 54.3 pCi/g.17

Remedial Action

Management Plan

Superfund remediation activities were not performed at OU-7. The State delegated the administration of the ICs to Denver’s Department of Public Works with oversight by CDPHE. The ICs were specified in the Management Plan, Denver Radium Site, Operable Unit 7, Denver Streets contracted to GEI Consultants. A first draft was completed in 1993 and was approved by the EPA and CDPHE on October 15, 1993. The Management Plan established procedures and controls for the protection of workers, the public, and the environment; the monitoring of any operation involving radium contaminated materials; and the control, interim storage, and eventual permanent disposal of excavated contaminated material.18

All activities that resulted in penetration of the affected streets’ pavement surface or curb and gutter were subject to the conditions and requirements of the plan. The plan outlined the personnel and coordinated responsibilities among the designated positions. Prior to the assignments of work orders, the Work Supervisor must have verified that the work planned was or was not in an affected street or intersection. The plan outlined three special conditions procedures: (1) Pavement repair, replacement, and modification, (2) Trenching and utility cuts, and (3) Pavement profiling (rotomilling). The plan also outlined emergency procedures when situations posed an imminent and substantial threat to life, health or property. Additionally, the Management Plan requires a minimum of 48-hour advance notification prior to the initiation of the work.

To revise the management plan, revisions were submitted to the EPA and CDPHE for review and comment. Upon final approval, the Management Plan Revision replaced the appropriate sections in the Management Plan.19 The Management Plan was revised in 1996, 2000, 2002, and 2003.

In December 1996, the Management Plan was revised to reflect personnel changes and to contain updated information on material deposition. On January 11, 2000 the Environmental Services Division (now known as the Department of Environmental Health (DEH)) was notified via letter by a resident that possible radioactive material may be present in the public right-of-way in the vicinity of 23rd Avenue and Glenarm Street. A field survey was conducted on January 12, 2000, and approximately 200 cubic feet of radium contaminated asphalt was found south of the current southern boundary of the known radium 103

contamination in 23rd Street. The Management Plan was amended in 2000 to reflect this change.20 In May 2002, DEH revised the Management Plan to reflect updated procedures for handling materials contaminated during removal of contaminated asphalt and road reconstruction.21

Radioactive Materials License

DEH began applying for a radioactive material license from the CDPHE on April 16, 1994 to secure a temporary storage facility for low level radioactive material collected from Denver Radium Streets. The City first selected the North Side Treatment Plant located at 56th Avenue and Washington Street as the location for the temporary storage facility,22 as well as the Roslyn Street Maintenance Complex located at 5440 Roslyn Street. Due to City zoning requirements, the proposed locations needed to be changed.23 Environmental Services resubmitted on application for a radioactive materials license to CDPHE on February 18, 1998.24 The license was granted and issued on December 31, 1998.25 In 1998, DEH announced that low-level contaminated asphalt and dirt would be temporarily stored at Denver International Airport (DIA) located at 27500 East 80th Avenue. The material was stored in environmentally safe waste drums, and the site received annual inspection.26 The license had an expiration date of December 31, 2003.27 On October 27, 2003, the DEH submitted an application for the renewal of the radioactive material license.28 The request for the license amendment was granted on January 7, 2004 with a new expiration date of December 31, 2008.29 (License 961-01/Amendment No. 03). The Radioactive Materials License was terminated on February 21, 2008 with the completion of the Denver Radium Streets project in 2007.30

Quarterly Reports

The Management Plan specified that quarterly reports must be submitted to CDPHE by Denver (CCOD). The plan required the City to maintain file documentation of all regulated activities conducted on the affected streets. CCOD began documenting all known regulated activities occurring in the streets beginning in 1993. Each quarterly report documented all known Radium Street activities during the specified time period such as rotomilling activities, street cut activities, and pre-operational surveys.31 In 2007, CCOD presented the final quarterly report to CDPHE as the result of the completion of the remedial action for OU-7.

Deer Trail Regional Facility

On February 28, 2006, the Rocky Mountain Low-Level Radioactive Waste Board designated the Clean Harbors Deer Trail Facility (CHDTF) in Adams County as a Regional Facility for disposal of the radium contaminated waste from the Denver Radium Superfund Site pursuant to the Rocky Mountain Low-Level Radioactive Waste Compact (99 Stat.1902-1909, 42 USC 2121d) and the Rules of the Board, for disposal of waste from the mining, milling, smelting, or similar processing of ores and mineral bearing material primarily for radium.

The City of Denver evaluated the site in 2006 by submitting a trial disposal of 6 B-25 boxes. On December 18, 2006, the inventory at DIA was loaded, transported, and disposed of at the CHDTF.32 On February 14, 2007, 45 B-25 boxes containing radium-impacted materials generated from BWAB (an oil and gas company) and Atlas Metals stored at DIA interim Facility from July 2006 to February 2007 were disposed of at the CHDTF.33 104

On March 20, 2007, an Agreement was entered between Denver and Clean Harbors DEH, Inc. for the transportation and disposal of waste generated from the Denver Radium Superfund Site for the 2007 Denver Radium Clean-up Program. On September 25, 2007, an Amendment to the Transportation and Disposal Agreement was entered between Denver and Clean Harbors for the transportation and disposal for radium-impacted materials generated from the Jason Street City right-of-way located in OU-3.34

Summary of Table 3: Storage and Permanent Off-site Disposal Activities

Table 3 summarizes the quarterly reports in chronological order, to indentify the amount of contaminated material removed from each location and distinguish the designated storage location before transporting the material to the disposal site. Indicated in bold text, under the storage location column, are the dates the contaminated material was transported from the temporary storage locations to the disposal site.

Table 3: Storage and Permanent Off-site Disposal Activities

Quarterly Report Street Amount of Storage Location Cut/Replacement Contaminated Location Material First Quarter 1998 12th Ave and York 1 (55-gal) drum Roslyn Fleet Maintenance Street (unauthorized) Complex Second Quarter 1998 Core samples collected 1 (55-gal) drum Roslyn Fleet Maintenance during pre-operational Complex survey of the streets Third Quarter 1998 York Street between 6th 9 (55-gal) drums Roslyn Fleet Maintenance Ave and 7th Ave Complex (unauthorized) Fourth Quarter 1998 No new material stored First Quarter 1999 No new material stored Second Quarter 1999 646 York Street 7 (55-gal) drums Denver International Airport (DIA) 871 Marion Street 3 (55-gal) drums DIA Third Quarter 1999 No new material stored Fourth Quarter 1999 Transported 21 55-gal drums were transported to the Envirocare disposal site on December 28, 1999 (243 cubic feet, Export Permit: CCOD-99-1)35 First Quarter 2000 No new material stored Second Quarter 2000 594 Lafayette St. 4 (55-gal) drums DIA 167 Lafayette St. 6 (55-gal) drums DIA Third Quarter 2000 319 Lafayette St. 5 (55-gal) drums DIA

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Fourth Quarter 2000 11th and Gaylord 23 (55-gal) drums DIA 2 96 cubic foot DIA containers 11th and Vine 10 (55-gal) drums DIA 11th and York 18 (55-gal) drums DIA 2 96 cubic foot DIA containers MISC 2 (55-gal) drums DIA Transported All 55-gallon drums were transported to the Envirocare disposal site on November 16, 2000. (514 cubic feet, Export Permit CCOD-00-1)36 1st and Lafayette 41 B-25 boxes DIA First Quarter 2001 824 Lafayette St. 6 (55-gal) drums DIA Second Quarter 2001 1st and Lafayette 34 B-25 boxes DIA Quarterly Report Street Amount of Storage Location Cut/Replacement Contaminated Location Material Third Quarter 2001 No new material stored Fourth Quarter 2001 Transported Eighty B-25 boxes and 6 55- gal drums were transported to the Envirocare disposal site. First Quarter 2002 No new material stored Second Quarter 2002 23rd and Curtis 12 (55-gal) drums DIA 568 Lafayette 10 (55-gal) drums DIA 2 B-25 boxes DIA Third Quarter 2002 23rd and Champa 3 B-25 boxes DIA 820 Park Avenue West 11th Avenue Pilot Study Fourth Quarter 2002 No new material stored First Quarter 2003 DIA Second Quarter 2003 1280 South Jason (OU- 3) 800 Corona DIA Champa and Stout St. 7 B-25 boxes DIA 3 (55-gal) drums DIA Third Quarter 2003 Transported During the week of July 7, 2003, 377 tons of low-level radioactive materials (91 B- 25 containers and 29 55-gal drums) from 11th Avenue 2002 Pilot Study and from street cuts were transported and disposed of at the U.S. Ecology disposal facility in Grand View, Idaho.

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Fourth Quarter 2003 York St./7th Ave 10 B-25 boxes DIA 710 Downing 8( 55-gal) drums DIA 1100 Umatilla (OU-2) 10 tons First Quarter 2004 No new material stored Second Quarter 2004 No new material stored Third Quarter 2004 No new material stored Fourth Quarter 2005 Transported All material was transported and disposed of at the U.S. Ecology disposal facility in Grand View, Idaho. Quarterly Report Street Amount of Storage Location Cut/Replacement Contaminated Location Material First Quarter 2005 No inventory Second Quarter 2005 No inventory Third Quarter 2005 No inventory Fourth Quarter 2005 Corona and 9th Ave 5 B-25 boxes DIA Bannock St. 1 (55-gal) drum DIA First Quarter 2006 Corona and 10th Ave 1 B-25 box DIA Second Quarter 2006 No new material stored Third Quarter 2006 No new material stored Fourth Quarter 2006 Transported 6 B-25 boxes were transported and disposed of at the Clean Harbors Deer Trails Regional Facility on December 18, 2006. First Quarter 2007 BWAB Property 45 B-25 boxes On February 14, 2007, 45 B- Holdings, LLC 25 boxes stored at DIA [Environmental interim Storage Facility Materials, Inc site: OU- from July 2006 to February 6] and Atlas Metals 2007 were disposed of at the Clean Harbors Deer Trail Facility. Second Quarter 2007 9th Avenue Ogden to 3,434 tons Clean Harbors Deer Trails Franklin Street Regional Facility Park Avenue West from 2,915 tons Clean Harbors Deer Trails California to Arapahoe Regional Facility Street Corona Street from 7th 1,630 tons Clean Harbors Deer Trails to 10th Avenue Regional Facility Third Quarter 2007 Corona Street from 7th 761 tons Clean Harbors Deer Trails (Final Quarterly Report) to 10th Avenue Regional Facility York Street 5,075 tons Clean Harbors Deer Trails Regional Facility Jason Street (OU-III) 4,840 tons Clean Harbors Deer Trails Regional Facility

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Denver Radium Streets Remediation

Following the creation and implementation of the Management Plan, CDPHE left Denver the responsibility to enforce the plan to ensure that the contaminated material was handled properly and disposed of at a licensed facility. However, ICs were ineffective due to limited resources to monitor for intrusive activities and limited effectiveness in permitting systems. Also, actively managing the contaminated materials required annual training of Denver and utility workers and required a large financial commitment from the City. According to the 2003 Five-Year Review, from August 1993 through August 2003, a total of 129 known street cuts were made for gas, sewer and water line repairs. Approximately 10 percent were performed outside the constraints of the Management Plan.37 The primary health concerns were the protection of street workers’ health, maintaining that radium contaminated materials were not spread around the neighborhoods, and were not used for fill or other purposes around houses or businesses. Therefore, Denver decided to remove the contaminated asphalt and sub-grade from the right-of-way, allowing for the de-listing of OU-2, -3, -6, -7 and -8. The solution also eliminated the management of street cuts and subsequent administrative burdens, while permanently eliminating the risk of spreading radium impacted materials around the community. The funding source included the state-imposed solid waste user fee at the Denver Arapahoe Disposal Site (DADS) as per Colorado statute. Revenue generated by the fee was used for the cost of handling, transporting, and disposing of radium impacted materials from the OU-7.

Since 2002, Denver informed and maintained public relations when project cleanup activities (including pilot test activities) were initiated. Denver held numerous open houses for the community, providing information as well as a venue for discussing public/neighborhood concerns, and Denver also maintained a public website.

Table 4: Radium Waste Disposal 2003-2007

Date Quantity (MT) Disposal Facility Contractor July 2003 7500.00 US Ecology Parsons June 2004 7500.00 US Ecology USACE June 2005 4500.00 US Ecology USACE December 2006 22.05 Clean Harbors Clean Harbors August 2007 24794.00 Clean Harbors Clean Harbors

2002 Denver Radium Pilot Study

A Curbstone Preservation and Decontamination Pilot Study was conducted in August 2002 along 11th Avenue between Race and Gaylord Streets. The study was used to refine and develop cost-effective, safe procedures for full-scale asphalt removal and curbstone preservation of the contaminated streets in OU-7. The study demonstrated that significant cost savings would be gained by Denver’s ability to transport and dispose of material under the Army Corps contracts at a reduced cost through 2009.

The method selected for removal of the contaminated materials was segmented excavation. Construction activities were conducted between August 12 and August 27, 2002. The asphalt as well as several inches 108

of sub grade were saw-cut into uniform blocks of different sizes and removed with a backhoe. The contaminated material was loaded into B-25 boxes with dimensions 6 ft. x 4 ft. x 4 ft. and a Department of Transportation (DOT) limited capacity of 10,000 lbs. The boxes were loaded onto a flatbed truck and were transported to DIA, where the material was temporarily stored until final disposal.

Prior to pavement saw-cutting and removal, the curbstone was screened for gross radioactivity. After removal of the contaminated asphalt and sub grade material, small amounts of contaminated material remained on the curbstone face. The contamination was removed either by a power washer or a wire brush used to manually remove surface debris from the curbstone. Air and radiation monitoring were conducted throughout the construction process.

The volume of waste removed included 75 B-25 boxes with an average net weight per B-25 box of 742 lbs. The study generated two 55-gal drums of wastewater. Gross Alpha was estimated at 83 pCi/l and gross Beta was estimated at 165 pCi/l.38

2003 Street Replacement Activities

Denver retained Parsons Engineering Science, Inc. to conduct the remedial activities. On June 13, 2003, Parsons was issued a Notice to Proceed for the demolition and reconstruction of 11th Avenue and Marion Streets.39 Remedial activities were performed from June 26, 2003 to October 1, 2003. Remediation activities included removal of Ra-226 impacted asphalt, curb, gutter, and impacted sub-grade material, removal of additional impacted materials adjacent to underground utilities, if present, and replacement and/or realignment of sanitary sewer lines. The waste was containerized in 225 cubic yard (yd3) capacity double wall poly liner bags. Ra-226 walkover surveys were conducted, and clean confirmation soil samples were collected and analyzed. The waste generated from the streets was transported and disposed at US Ecology in Grand View, Idaho.40 The 2003 projects were completed ahead of schedule and within budget. New features were added within the streets such as handicapped ramps at all intersections and upgraded storm water sewer inlets.

11th Avenue: Race Street to Josephine Street

Table 5: Quantity of materials saw-cut, removed, and disposed of:

Average Thickness: 8.17 inches Total Area Saw-Cut: 39,193 ft2 Total Area Excavated: 34,838 ft2 Number of Super Sacks® removed: 319 Volume removed: 34,524 ft3 Waste transportation 3,286 tons

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Marion Street: 6th Avenue to 10th Avenue

Table 6: Quantity of materials saw-cut, removed, and disposed of:

Average thickness 7.87 inches Total Area Excavated: 6,615 yd2 Number of Super Sacks® removed: 267 Volume removed: 38,581 ft3 Waste transportation 2,796 tons

Total Export - 11th Avenue: Race Street to Josephine Street and Marion Street: 6th Avenue to 10th Avenue

Table 7: 2003 Radium Streets Exportation Summary41

Export Date Number of bags Weight (tons) July 2003 170 1,730.4 August 2003 153 1,595.2 September 2003 162 1,723.1 October 2003 101 1,045.6 TOTAL 586 bags 6,094.3 tons

Following demolition and removal, both streets were available for unrestricted use and were certified clean. Prepared by Denver on March 3, 2004, the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) report indicated that both street segments met the release criteria, and future work in these streets should not trigger the implementation of the Management Plan.42, 43 On March 8, 2004, Denver submitted an application to request partial de-listing of the street segments, 11th Ave from Race to Josephine Street and Marion Street from 6th Avenue to 10th Avenue.44

Figure 1: Project Location Map:45

Project Area

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2004 Street Replacement Activities

Lafayette Street from 1st to 10th Avenues and Humboldt St. from 7th to 9th Avenue

On July 29, 2004, Parsons Engineering Science was awarded the demolition and reconstruction contract of Lafayette Street from 1st to 10th Avenues and Humboldt St. from 7th to 9th Avenue. The demolition of the streets started August 8, 2004 and reconstruction of Humboldt Street and part of Lafayette ended in October 29, 2004. Remediation activities included removal of Ra-226 impacted asphalt, curb, gutter, and impacted sub-grade material, removal of additional impacted materials adjacent to underground utilities, and replacement and/or realignment of sanitary sewer lines. Waste generated from the streets was disposed at US Ecology in Grand View, Idaho under Denver and Department of Army contract. For each phase, impacted materials were removed followed by radiation surveying, demolition of non-impacted items, and reconstruction of the street. The Ra-226 material was containerized in 220 cubic feet capacity double wall poly liner bags and was transported to the US Ecology Disposal Facility. A total of 824 disposal bags were collected from both street segments. Each disposal bag was marked and tagged with a consecutive, unique number noting the origin of the impacted material, date of generation, weight, and other data.46

Prepared by DEH in March 2005, the MARSSIM report indicated that both street segments should be partially de-listed from OU-7, and future work in these streets should not trigger the implementation of the Management Plan.47 On March 10, 2005, Denver submitted an application for partial deletion of the street segments Humboldt Street from 7th Avenue to 9th Avenue and Lafayette Street from 1st Avenue to 10th Avenue from the NPL.

Figure 2: Project Location Map:48

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2005 Street Replacement Activities

Downing Street from 7th Avenue to 10th Avenue

On May 2005, Denver issued Parsons a Field Change/Change Directive to expand the Denver Radium Street reconstruction project to include Downing Street from 7th Avenue to 10th Avenue. The project began on June 6, 2005 and concluded in July 2005. Approximately 213 bags and 2,439 tons of radium- impacted waste49 were shipped and disposed at US Ecology in Grand View, Idaho under the Department of Army contract.50 All radium-impacted asphalt and sub grade from Downing St. were removed. In October 2005, Parsons released the MARSSIM Evaluation Report for Downing Street- 7th Avenue to 10th Avenue. The MARSSIM report indicated that the street segment met the release criteria and was suitable for free release and partial delisting. On November 4, 2005, Denver submitted an application for partial deletion of Downing Street segment from 7th Avenue to 10th Avenue from the NPL.

Bannock St., OU-VIII from Jewell to Mexico

On August 2005, Denver issued Parsons a Field Change to expand the 2005 Radium Contract (CE 41036) to include the cleanup and reconstruction of Bannock St., OU-8 from Jewell to Mexico. The cleanup and reconstruction started on September 09, 2005. The depth of contamination was 24 inches. Waste generated from Bannock was transported to US Ecology through the Shattuck contract as part of the Settlement between Denver and the United States.51

2006 Street Replacement Activities

Corona Street from 7th to 10th Avenue; 9th Avenue from Franklin to Ogden Street; Park Avenue West from Arapahoe Street to California; and Operable Unit III- Jason Street

For the 2006 Denver Radium Replacement Program, Denver remediated Corona Street from 7th to 10th Avenue, 9th Avenue from Franklin to Ogden St., Park Avenue West from Arapahoe St. to California, and OU- 3 at Jason Street. The program was on hold due to litigation between Adams County and the State of Colorado regarding the Clean Harbors permit for disposal of low-level radioactive waste at Clean Harbors Deer Trail facility. On May 3rd, 2006, Denver submitted an application for exportation of waste from the region for disposal at US Ecology. The request was denied by the Rocky Mountain Low-Level Radioactive Waste Board. On June 30, 2006, Denver submitted to the Board a ‘Request for Reconsideration.’ The Rocky Mountain Low-Level Radioactive Waste Board denied the export application on August 9, 2006.52 However, on December 5, 2006, a transportation and disposal agreement was reached between Denver and Clean Harbors.

2007 Street Replacement Activities

On April 17, 2007, Parsons Commercial Technology Group Inc and Envirocon Incorporated were awarded the demolition and reconstruction contract of 9th Avenue from Franklin to Ogden Street, Corona from 7th to 10th Avenue, York from 6th to 13th Avenue, and Park Avenue. On June 26, 2007, Denver issued Envirocon a Field Change/Change Directive to expand the Denver Radium Street reconstruction project CE 62054 to include a portion of Operable Unit 3, Jason Street from Louisiana Avenue to South Platte River Drive. 112

As of September 14, 2007, radium-impacted materials on 9th Avenue from Ogden to Franklin Street, Corona from 7th to 10th Avenue, Park Avenue West from Arapahoe to California, and York Street from 6th Avenue to 13th Avenue were removed, transported and disposed at the Deer Trail Disposal facility. Following disposal, the street segments were reconstructed.

On September 16, 2007, the MARSSIM Closure Report for Park Avenue West from Arapahoe Street to California Street, prepared by Envirocon, indicated that this portion of OU-7 met the release criteria.53 In November 2007, Parsons released the MARSSIM Closure Report for 9th Avenue- Cheesman Park to Ogden Street; Corona Street- 7th Avenue to 10th Avenue; and York Street- 6th Avenue to 13th Avenue. The MARSSIM report indicated that 9th Avenue, Corona, and York Street met the release criterion.54 In January 25, 2008, Envirocon released a MARSSIM Closure report for Jason Street from West Louisiana Avenue to South Platte River Drive. The report indicated that the street segment met the release criteria.55

A total of 21,769.97 tons or 13,686.77 yd3 of radium impacted materials were generated and disposed at Clean Harbors Deer Trail Facility.

Table 8: 2007 Radium Streets Exportation Summary

Location Radium Waste Removed 9th Ave. from Ogden to Franklin 3,434 tons Park Ave. West from California to Arapahoe 2,915 tons Corona St. from 7th Ave. - 10th Ave. 2,391.66 tons York Street 5,075 tons Jason Street 7,946.31 tons Total 21,761.97 tons56

The cleanup of Operable Unit 7, commonly referred to as Denver Radium Streets was completed in 2007, allowing Operable Unit 7 (Denver Radium Streets) to be eligible for deletion from the NPL.

113

Figure 3: Project Location Map:57

Figure 4: Project Location Map

114

Figure 5: Project Location Map:

Figure 6: Project Location Map:

115

Table 9: Denver Radium Street Implementation:

Site Cleanup Cost Volume Disposal Facility Status Disposed Cleanup/T&D

Pilot Study 2002 $185,394 280 Yd3 US. Ecology

11th Ave/Marion 2003 $3,923,990 3,717 Yd3 US. Ecology

Lafayette/Humboldt/O 2004 $4,747,625 4,711 Yd3 US. Ecology U-2

Downing/Bannock/O 2005 $1,109,130 8,431 Yd3 US. Ecology U-VI

Park Ave/9th 2007 $6,763,641 14,763 Yd3 Clean Harbors Ave/Corona/York /Jason

TOTAL $16,729,780 31,902 Yd3

De-listing

A Final Close-Out Report was signed on September 27, 2006.58 In a letter dated January 2, 2008, the State of Colorado concurred with the EPA’s intent state in the Notice of Deletion for Ou-7 of the Denver Radium Superfund Site from the NPL.59

On November 8, 2010 the direct final partial deletion of OU-7 from the NPL became final, and all of OU- 7 of the Denver Radium Superfund Site was deleted from the NPL.

116

Bibliography

ARIX. July 1982. Engineering Assessment and Remedial Action Plan for Radium Processing Residues at Nine Streets and One Alley in Denver, Colorado. Prepared for the Colorado Department of Health Under Contract No. C-298167.

CH2MHill. July 26, 1985. Draft Feasibility Study: Streets, Denver Radium Site.

City and County of Denver Environmental Services. February 16, 1994. Quarterly Report of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 13, 1995. Quarterly Report of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. April 22, 1998. Quarterly Report: First Quarter 1998 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. May 13, 1998. “Low Level Radioactive Materials to be Stored at Temporary Site at DIA.”

City and County of Denver Environmental Services. October 7, 1998. Quarterly Report: Third Quarter 1998 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. January 4, 1999. Quarterly Report: Fourth Quarter 1998 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 12, 1999. Quarterly Report: Second Quarter 1999 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. January 6, 2000. Report of Exports of LLRW from the Rocky Mountain Region.

City and County of Denver Environmental Services. January 25, 2000. Quarterly Report: Fourth Quarter 1999 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 5, 2000. Quarterly Report: Second Quarter 2000 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. October 11, 2000. Quarterly Report: Third Quarter 2000 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. November 21, 2000. Report of Exports of LLRW from the Rocky Mountain Region.

City and County of Denver Environmental Services. January 23, 2001. Quarterly Report: Fourth Quarter 2000 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. April 11, 2001. Quarterly Report: First Quarter 2001 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 10, 2001. Quarterly Report: Second Quarter 2001 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. October 5, 2001. Quarterly Report: Third Quarter 2001 of Activities for Operable Unit 7 of the Denver Radium Superfund Site. 117

City and County of Denver Environmental Services. January 11, 2002. Quarterly Report: Fourth Quarter 2001 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services: Diana Shannon. May 13, 2002. RE: Proposed Revisions to Management Plan, Denver Radium Site, Operable Unit VII, Denver Streets.

City and County of Denver Environmental Services. July 10, 2002. Quarterly Report: Second Quarter 2002 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. August 2002. Denver Radium Streets Monthly Report.

City and County of Denver Environmental Services. October 1, 2002. Quarterly Report: Third Quarter 2002 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. June 2003. Quarterly Report: Second Quarter 2003 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Department of Public Works. June 13, 2003. Re: Contract No. CE31001

City and County of Denver Environmental Services. September 2003. Quarterly Report: Third Quarter 2003 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. December 2003. Quarterly Report: Fourth Quarter 2003 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. 2004. 2004 Radium Streets Information Sheet.

City and County of Denver. January 13, 2004. Report of Export of LLRW from the Rocky Mountain Region.

City and County of Denver. February 2004. Final Report: Denver Radium Streets: 11th Ave: Race St. to Josephine St. and Marion Street: 6th Ave. to 10th Ave.

City and County of Denver. March 3, 2004. MARSSIM Evaluation Summary Report. 11th Avenue- Race Street to Josephine Street and Marion Street- 6th Avenue to 10th Avenue.

City and County of Denver. March 8, 2004. Re: Application for partial de-listing of 11th Avenue, Race Street to Josephine Street, and Marion Street, 6th Avenue to 10th Avenue.

City and County of Denver Environmental Services. June 2004. Quarterly Report: Second Quarter 2004 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. First Quarter 2005. Quarterly Report: First Quarter 2005 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. March2005. MARSSIM Evaluation Report. Humboldt Street- 7th Avenue to 9th Avenue AND Lafayette Street- 1st Avenue to 10th Avenue.

City and County of Denver. July 2005. Denver Radium Streets Monthly Report.

City and County of Denver Environmental Services. July 2005. Quarterly Report: Second Quarter 2005 of Activities for Operable Unit 7 of the Denver Radium Superfund Site. 118

City and County of Denver Environmental Services. December 2005. Quarterly Report: Fourth Quarter 2005 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 2006. Quarterly Report: Second Quarter 2006 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. 2007. 2007 Denver Radium Streets Information Sheet.

City and County of Denver Environmental Services. January 2007. Quarterly Report: Fourth Quarter 2006 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. April 2007. Quarterly Report: First Quarter 2007 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. July 2007. Quarterly Report: Second Quarter 2007 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. October 2007. Quarterly Report: Third Quarter 2007 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver Environmental Services. December 2007. Quarterly Report: Fourth Quarter 2007 of Activities for Operable Unit 7 of the Denver Radium Superfund Site.

City and County of Denver. February 2008. Denver Radium Streets Monthly Report.

Colorado Department of Health: Thomas Looby. February 18, 1986. RE: Denver Streets Draft R.O.D.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site.

Envirocon. September 16, 2007. MARSSIM Closure Report: For Park Avenue West from Arapahoe Street to California Street.

Evirocon. January 25, 2008. MARSSIM Closure Report: For Jason Street from West Louisiana Avenue to South Platte River Drive.

GEI Consultants. August 27, 1996. RE: Denver Radium Superfund Site: Quantity Estimate of Contaminated Pavement Volume in OU-7.

Colorado Municipal Facts. 1923, 1924, 1925.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

Parsons. July 2004. Denver Radium Streets: Draft Work Plan- Lafayette Street: 1st Avenue to 10th Avenue, Humboldt Street: 7th Avenue to 9th Avenue.

Parsons. November 2007. MARSSIM Evaluation Report.

RUST Geotech Inc. June 1994. Denver Radium Site Operable Unit 7 Interim Close Out Report for the U.S. Environmental Protection Agency Five-Year Review Site. 119

State of Colorado. September 20, 2003. Final Denver Radium Site Five-Year Review.

State of Colorado. January 2, 2008. Notice of Deletion.

U.S. Environmental Protection Agency. 1985. Task Memorandum for Denver Radium Site-Streets.

Conducted by Jacobs Engineering Group for CH2MHill.

U.S. Environmental Protection Agency. March 24, 1986. Superfund Record of Decision Denver Radium Site Streets.

U.S. Environmental Protection Agency. October 9, 1992. Superfund Explanation of Significant Differences for the Record of Decision: Denver Radium Superfund Site (OU-7) Denver, Colorado.

U.S. Environmental Protection Agency. March 3, 1994. Minor Change to the ROD Operable Unit 7 (Streets).

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets.

120

Endnotes

1 CH2MHill. July 26, 1985. Draft Feasibility Study: Streets, Denver Radium Site. 2 U.S. Environmental Protection Agency. March 24, 1986. Superfund Record of Decision Denver Radium Site Streets. 3 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Streets 4 U.S. Environmental Protection Agency. September 25, 2006 5 CH2MHill. July 26, 1985. 6 Denver Municipal Facts. 1923, 1924, 1925. 7 Denver Municipal Facts. 1923, 1924, 1925. 8 RUST Geotech Inc. June 1994. Denver Radium Site Operable Unit 7 Interim Close Out Report for the U.S. Environmental Protection Agency Five-Year Review Site. 9 ARIX. July 1982. Engineering Assessment and Remedial Action Plan for Radium Processing Residues at Nine Streets and One Alley in Denver, Colorado. Prepared for the Colorado Department of Health Under Contract No. C- 298167. 10 CH2MHill. July 26, 1985 11 U.S. Environmental Protection Agency. 1985. Task Memorandum for Denver Radium Site-Streets. Conducted by Jacobs Engineering Group for CH2MHill. 12 U.S. Environmental Protection Agency. March 24, 1986 as cited in CH2MHill. July 26, 1985. Draft Feasibility Study: Streets, Denver Radium Site. 13 GEI Consultants. August 27, 1996. RE: Denver Radium Superfund Site: Quantity Estimate of Contaminated Pavement Volume in OU-7. 14 U.S. Environmental Protection Agency. March 24, 1986. 15 U.S. Environmental Protection Agency. March 24, 1986. 16 U.S. Environmental Protection Agency. October 9, 1992. Superfund Explanation of Significant Differences for the Record of Decision: Denver Radium Superfund Site (OU-7) Denver, Colorado. 17 U.S. Environmental Protection Agency. March 3, 1994. Minor Change to the ROD Operable Unit 7 (Streets). 18 U.S. Environmental Protection Agency. September 25, 2006 19 City and County of Denver Environmental Services: Diana Shannon. May 13, 2002. Re: Proposed Revisions to Management Plan, Denver Radium Site, Operable Unit VII, Denver Streets. 20 City and County of Denver Environmental Services. January 25, 2000. 21 City and County of Denver Environmental Services. July 10, 2002. 22 City and County of Denver Environmental Services. February 16, 1994 23 City and County of Denver Environmental Services. July 13, 1995. 24 City and County of Denver Environmental Services. April 22, 1998. 25 City and County of Denver Environmental Services. January 4, 1999. 26 City and County of Denver. May 13, 1998. “Low Level Radioactive Materials to be Stored at Temporary Site at DIA.” 27 City and County of Denver Environmental Services. June 2003. 28 City and County of Denver Environmental Services. December 2003. 29 City and County of Denver Environmental Services. June 2004. 30 City and County of Denver. February 2008. Denver Radium Streets Monthly Report. 31 City and County of Denver Environmental Services. February 16, 1994. 32 City and County of Denver Environmental Services. January 2007. 33 City and County of Denver Environmental Services. April 2007. 34 City and County of Denver Environmental Services. October 2007. 35 City and County of Denver. January 6, 2000. Report of Exports of LLRW from the Rocky Mountain Region. 36City and County of Denver. November 21, 2000. Report of Exports of LLRW from the Rocky Mountain Region. 37 State of Colorado. September 20, 2003. Final Denver Radium Site Five-Year Review. 38 City and County of Denver. August 2002. Denver Radium Streets Monthly Report. 39 City and County of Denver Department of Public Works. June 13, 2003. Re: Contract No. CE31001 121

40 City and County of Denver. March 8, 2004. Re: Application for partial de-listing of 11th Avenue, Race Street to Josephine Street, and Marion Street, 6th Avenue to 10th Avenue. 41 City and County of Denver. January 13, 2004. Report of Export of LLRW from the Rocky Mountain Region. 42 City and County of Denver Environmental Services. September 2003. 43 City and County of Denver. March 3, 2004. MARSSIM Evaluation Summary Report. 11th Avenue- Race Street to Josephine Street and Marion Street- 6th Avenue to 10th Avenue. 44 City and County of Denver. March 8, 2004. 45 City and County of Denver. February 2004. Final Report: Denver Radium Streets: 11th Ave: Race St. to Josephine St. and Marion Street: 6th Ave. to 10th Ave. 46 Parsons. July 2004. Denver Radium Streets: Draft Work Plan- Lafayette Street: 1st Avenue to 10th Avenue, Humboldt Street: 7th Avenue to 9th Avenue. 47 City and County of Denver. March2005. MARSSIM Evaluation Report. Humboldt Street- 7th Avenue to 9th Avenue AND Lafayette Street- 1st Avenue to 10th Avenue. 48 City and County of Denver. 2004. 2004 Radium Streets Information Sheet. 49 City and County of Denver. July 2005. Denver Radium Streets Monthly Report. 50 City and County of Denver Environmental Services. July 2005. 51 City and County of Denver Environmental Services. December 2005. 52 City and County of Denver Environmental Services. July 2006. 53 Envirocon. September 16, 2007. MARSSIM Closure Report: For Park Avenue West from Arapahoe Street to California Street. 54 Parsons. November 2007. MARSSIM Evaluation Report. 55 Evirocon. January 25, 2008. MARSSIM Closure Report: For Jason Street from West Louisiana Avenue to South Platte River Drive. 56 City and County of Denver Environmental Services. December 2007. 57 City and County of Denver. 2007. 2007 Denver Radium Streets Information Sheet. 58 Colorado Department of Public Health and Environment. September 30, 2008. 59 State of Colorado. January 2, 2008. RE: Notice of Deletion 122

Denver Radium Superfund Site

Operable Unit 8 Shattuck Chemical, Inc.

Table of Contents:

Background Information 123 Remedial Investigation 125 Remedial Objectives/Record of Decision 128 Opposition to ROD 128 Amended ROD 130 Remedial Action: Original ROD 130 Remedial Action: Amended ROD 131 Explanation of Significant Differences 137 Institutional Controls 138 De-listing 139 Bibliography 140 Endnotes 142

Tables and Figures:

Table 1: Operable Unit 8 Properties 124 Table 2: Operable Unit 8 Chronology of Site Events 124 Table 3: Shattuck FUSRAP/NORM Loads Material Received 2003 135 Table 4: Shattuck FUSRAP/NORM Loads Material Received 2004 136 Table 5: Shattuck FUSRAP/NORM Loads Material Received 2005 136

123

Background Information

Denver Radium Operable Unit Eight (OU-8) consisted of 10 acres divided into three areas: the 5.9-acre S.W. Shattuck Chemical Inc. (Shattuck) property located at 1805 South Bannock Street; the 4.3-acre railroad right-of-way to the west of the Shattuck property; and nearby “vicinity properties” located within the area bounded by South Santa Fe Drive (U.S. Highway 85), South Broadway, Jewell Avenue, and Mexico Avenue.1

The site is located within the drainage basin of the South Platte River, which is approximately 3,000 feet west of the site. Beneath OU-8 is a shallow unconfined aquifer perched on bedrock and merges with the alluvial aquifer beneath the floodplain of the South Platte River.2 The groundwater is not used as a drinking water source and flows west across the site and then northwest toward the South Platte River. Surface water on the site generally flows the topography towards the northwest.

At the time of the Record of Decision (ROD), the facilities located on the Shattuck property included: six permanent buildings, miscellaneous storage sheds, underground storage facilities, above ground storage tanks, process equipment and piping, and asphalt and concrete paving. A runoff catchment basin, capturing a limited amount of surface runoff, was located on the Shattuck property south of Building 6 at the time of the ROD. The rail lines are elevated above the surrounding grade, impeding the flow of surface runoff, and creating some ponding during rainfall.3

Contamination at OU-8 is due to the site’s historical use for mineral-processing operations, including the processing of tungsten ores, carnotite ores (for uranium and vanadium), radium slimes, molybdenum ores, and depleted uranium. During the 1920s, the site treated molybdenum ores and extracted ferric vanadate from vanadium and uranium ores byproduct. In the 1930s, the site processed radium slimes to recover radium and produced radium salts, uranium compounds, and other rare mineral products from carnotite ores. In the 1940s, the site processed uranium compounds and molybdenum, and in the 1950s, the site processed uranium ores. The activity on the site is unknown during the majority of the 1960s, but from 1969 to 1984, operations at the site consisted primarily of processing molybdenite for the recovery of molybdenum compounds and recovery of rhenium as a by-product. During the same period, small batch operation for the production of uranium products from depleted uranium occurred on the site.4 The processed ore residues remained on the site and became intermixed with site soils. A detention pond was created at the northern end of the property to hold molybdenum slime waste. The previous site activities and operations resulted in the contamination of the site with radioactive elements including Ra-226, Th- 230, various uranium isotopes, and non-radioactive metals such as lead, arsenic, and selenium. Operations ceased in 1984, and the site was fenced for restricted access. 5 Pursuant to a consent decree between CDPHE and the S.W. Shattuck Chemical Company, Inc., a subsurface impoundment, utilized as an evaporation pond when the 1805 South Bannock facility was in operation, was excavated and closed in 1987.6 In 1989, the EPA conducted an emergency removal action at one of the vicinity properties, which involved the installation of an active radon reduction system in order to reduce excessively high levels of radon present at a commercial property.

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Table 1: Operable Unit 8 Properties7

Operable Unit Property Name at Time of ROD Address OU-8 S.W. Shattuck Chemical Company 1805 South Bannock Street

Table 2: Operable Unit 8 Chronology of Site Events8

EVENT DATE Initial discovery: U.S. Environmental Protection Agency (EPA) notes reference to National Radium Institute January 1979 (NRI) and initiates search. Denver Radium Site on the National Priorities List September 8, 1983 (NPL) Surface Impoundment Closure 1987 Superfund State Contract or Agreement Signature May 1988 Baseline Risk Assessment September 1991 Remedial Investigation/Feasibility Study completed September 1991 Pre-NPL responses October 1991 Record of Decision (ROD) signature January 28, 1992 Enforcement documents (Unilateral Administrative August 1992 Order) Remedial Design Begins April 1994 Remedial Design Complete June 1996 Construction date (start)- monolith July 1996 Actual Remedial Action start September 1996 Oily soils shipped off-site 1997 Storm Sewer Remedial Activity February-March 1997, March-May 1999 Construction completion date- monolith September 1998 Final Close Out Report February 1999 5-Year Review November 1999 Amended ROD June 2000 Amended ROD Implementation (Start/Finish) September 2002/September 2006 Design Submittal October 2002 Mobilization December 2002 Building Erection (Start/Finish) December 2005/March 2006 Perimeter Air Monitoring (Start/Finish) March 2003/August 2006 Monolith Demolition (Start/Finish) March 2003/March 2006 Bannock Street Remediation (Start/Finish) September 2005/February 2006 Perimeter Soils Removal (Start/Finish) October 2005/July 2006 Molybdenum Soils Removal (Start/Finish) May 2006/July 2006 Final Status Surveys (Start/Finish) August 2003/August 2006 Independent Verification August 2003/August 2006 Backfill (Start/Finish) May 2005/July 2006 Site Restoration/Vegetation August 2006 Demobilization September 20069 125

Remedial Investigation

The Remedial Investigation (RI) for OU-8 was conducted in 1988 by the EPA, and radiological- contaminated soils were identified on the 1805 South Bannock Street property, the railroad rights of way, and the vicinity properties. Contaminated soil on the 1805 South Bannock Street property covered approximately 230,000 square feet, and the estimated volume of contaminated soil on the property was 38,500 cubic yards. The contamination was found to extend from the ground surface to depths ranging over 14.5 feet below the ground surface.10 Radioactive soil contamination covered approximately 34,000 square feet of the 187,000 square feet of railroad rights-of-way with a total volume of contaminated materials estimated to be greater than 4,500 cubic yards. The volume of contaminated soil on the vicinity properties was estimated to be 6,000 cubic yards. Additional metals contamination, including radioactive lead-210, thorium-230, and uranium, as well as non-radioactive metals such as lead and arsenic, were identified in the soils. It was predicted that 500 cubic yards of the estimated volume on the Shattuck property would require remediation due to thorium-230 and uranium contamination. The majority of the additional metals contamination was co-located within the radium-226 contaminated soils.11

The OU-8 site includes the 1805 South Bannock Street property, the 4.3 acre railroad right-of-way located to the west of the 1805 South Bannock Street property, and the nearby properties, referred to as “vicinity” properties.12 The 1992 ROD divided the 1805 South Bannock Street property into three areas: (1) the buildings and process area located in the center of the property; (2) the open space areas to the north and south; and, (3) the closed evaporation pond which is located in the north open area of the property. Buildings and process area:

The majority of soils in this area were contaminated. The highest measured one-meter gamma radiation exposure rate in this area was 2,800 microroentgens/hour near the southeast corner of Building 6. Subsurface radiation data indicated contamination depths ranging from one to nine feet, with an average depth of about 40 inches and an average equivalent radium-226 concentration of about 90 picocuries per gram (pCi/g).13

Open space areas:

The open areas of the Shattuck property to the north and south of the buildings and process area exhibited contamination throughout the area, with the exception of the southern area near the perimeter of the property, the area near the southwest corner of Building 6, and the areas east and south of the closed evaporation pond. Depth of contamination for the contaminated areas ranged from 0.5 to over 14.5 feet, with an average depth of approximately 39 inches and an average equivalent radium concentration of about 69 pCi/g.14

Closed Evaporation Pond:

Direct gamma radiation measurements on the asphalt surface of the closed pond indicated no surface contamination in this area. Soil immediately beneath the asphalt cover exhibited background concentrations of radioactive contaminants. Radium-226 and thorium-230 contamination was found from approximately 6 feet to 7.5 feet below the surface over the western two thirds of the former pond area.

126

Railroad Rights-of Way

The 4,500 cubic yard estimate of contaminated soil on the railroad rights-of-way included nearly the full length of the area between the east rail line and the Shattuck property as well as some limited areas to the west of the rail line. The estimated depth of contamination was 0.5 to 2.5 feet along the southern portion and 5 feet from the northern portion. The soil directly beneath the rail line was not sampled, but the data for the surrounding area indicated that radium contamination beneath the line was likely. The highest radium equivalent value measured in the railroad rights of way was 570 pCi/g.15

Vicinity Properties

The estimated volume of contamination was 6,000 cubic yards.

 1860 South Bannock Street property: Radium contaminated soils were located beneath the floor slab of a building, the concrete driveway and parking area, and beneath an asphalt-covered area extending beyond the property to the north and south. The amount of contaminated material was approximately 2,700 cubic yards and extended to a depth of over eight feet. In August 1989, an emergency removal action was conducted on the property due to high levels of radon gas and decay products measured in the building. While contaminated source materials were not removed, a vent system was installed and slab joints were sealed to mitigate the radon.

 1700-1830 South Bannock Street property: The contaminated area consisted of uncovered soil, as well as asphalt, concrete, driveways, and parking areas. The deposit included approximately 1,300 cubic yards of material contaminated with radium to a depth of over three feet.

 1822 South Bannock Street property: Radium contaminated soils were located in the fill material beneath the concrete floor slab of a building and adjacent to the east side of the building. The deposit included approximately 250 cubic yards of material and extends to a depth of approximately 2.5 feet.

 1788 South Acoma Street property: Radium contaminated soils were limited to exterior soils ranging from a depth of two feet, with an estimated volume of 220 cubic yards.

 South Bannock Street: 1,100 cubic yards of radium contaminated soils were estimated to exist beneath South Bannock Street. This estimate was based on adjacent investigations. Investigation into the street was not performed because of the presence of numerous utility lines.16

Buildings

Based on procedures outlined in the Nuclear Regulatory Commission (NRC) Regulatory Guide 1.86, radioactive contamination was identified in five of the six permanent buildings on the Shattuck property. The volume of the radiologically contaminated material associated with the buildings was estimated to be approximately 2,095 cubic yards. The estimate included 100 percent of three of the buildings, floor slabs of two of the buildings, and at least one building was contaminated with depleted uranium. 127

The contamination of the buildings was associated with radioactive constituents which had been processed on the site. Radium-226 and uranium were identified in building-material samples. Based on visual inspection, radiologically contaminated building materials were suspected to contain relatively abundant concentrations of asbestos in two of the contaminated buildings, with minor amounts in a third building.

Tanks

Direct radiation measurements showed elevated levels of total alpha activity for five above ground storage tanks, indicating that these tanks were contaminated by the processing operations at the site. The averages of the total alpha activity on the five tanks were greater than the average listed in the NRC Regulatory Guide 1.86. Also, non-maximum measurements exceeded the NRC maximum. The radioactive contamination associated with the tanks was at relatively low levels, and it was expected that the tanks could be adequately decontaminated.17

Air

Air investigations included indoor and outdoor measurements for radioactive contaminants and organic vapors. Three buildings exhibited concentrations of radon gas and its decay products in excess of the EPA guideline of 0.02 working levels (WL). Monitoring of the outdoor air detected low atmospheric concentrations of radioactive contaminants. While one vicinity property exhibited very high radon levels requiring emergency removal, measurements of radon at other vicinity properties where radium contaminated soils were identified did not exceed the EPA guideline of 0.02 WL. Indoor and outdoor measurements of organic vapors were less than the detection limit of approximately one part per million benzene equivalent.

Groundwater

The on-site alluvial groundwater is contaminated with gross alpha radioactivity and gross beta radioactivity in excess of Safe Drinking Water Act Maximum Contaminant Levels (MCLs), and uranium in excess of the range of proposed standards. The off-site alluvial aquifer down gradient from the site continues to exhibit significant concentrations which then fall off to background levels as the aquifer is diluted by the system underlying the Platte River. The primary radioactive contaminant in the groundwater is uranium.

Volatile organic compounds were detected in concentrations above MCLs in an up-gradient well, onsite wells, and down-gradient offsite wells. Data from the up-gradient well provide strong evidence that significant offsite sources of volatile compounds, specifically 1,1,1-trichloroethane, have affected groundwater. Soil boring data indicated that onsite sources of tetrachloroethene and associated degradation products may impact groundwater quality as well. The semi-volatile compounds phenol, benzoic acid, and phthalates were detected in onsite wells.

The metals arsenic, cadmium, and selenium were measured in levels exceeding MCLs, and very high concentrations of molybdenum were observed in on-site and off-site well samples. Data submitted by Denver, and confirmed by CDPHE, indicated that groundwater associated with the site was infiltrating the storm sewer located along South Santa Fe Drive. The storm sewer discharges into the South Platte River just south of Louisiana Avenue. 128

Remedial Objectives/Record of Decision

An original ROD for OU-8 was signed in January 1992 and selected solidification and stabilization as well as groundwater monitoring as its remedial action strategy. Also, buildings and facilities were to be demolished and disposed of off-site.

The contaminated site soils received treatment by solidification and stabilization process implemented under the ROD, and thus satisfied the statutory preference for treatment of the principal-threat wastes. The original ROD remedy imposed a minimum 300-year effectiveness criterion, in effect making the Shattuck site a perpetual waste management facility located in a commercial, light industrial and residential area.

Groundwater contamination present beneath the site was to be remediated by natural attenuation or by removal of the onsite source. Groundwater monitoring was specified to determine the effectiveness of the concrete structure referred to as the monolith for stabilization in immobilizing site contaminates. Statutory 5-year reviews also were required by the initial ROD.18

Therefore, the selected remedy for OU-8 detailed in the initial ROD, dated January 1992, included the following:

 Demolition and off-site disposal of existing facilities on the 1805 South Bannock Street property;  Excavation, consolidation, stabilization, disposal, and capping of all contaminated soils (including soils from the vicinity and railroad right-of-way properties) on the 1805 Bannock Street property;  Institutional controls (ICs), maintenance, and monitoring to assure protectiveness of the selected remedy; and  Source control and monitoring of flushing and attenuation of the contaminated groundwater plume. The groundwater portion of the remedy may be modified in the future if remedial objectives are not met within a reasonable time frame.19

Opposition to Original ROD:

In March 1993, Mayor Wellington E. Webb sent a formal letter to Dr. Pat Nolen, former Executive Director of the Colorado Department of Environmental Health urging a decision to change the selected remedy for OU-8 to require permanent off-site disposal.20 After continued opposition from the community and Mayor Webb towards the selected remedy and new information indicating the cost of off- site disposal had been lowered, the EPA continued to proceed with the on-site stabilization remedy on January 26, 1994.21 In May 1994, Denver, Department of Zoning Administration, issued a Cease and Desist order to the S.W. Shattuck Chemical Company, Inc. stating violations of the Denver Zoning Ordinance.22 On June 10, 1994, the Shattuck Company issued an appeal from the Cease and Desist order claiming that Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) preempted local zoning ordinances.23 In response, remedial action was delayed for two years during legal action. 129

In February 1996, a federal judge in Colorado found Denver’s Cease and Desist order unconstitutional under the Constitution’s Supremacy Clause.24 In March 1996, Mayor Webb announced that Denver filed a notice of appeal in U.S. District court to overturn the federal district court ruling allowing radioactive wastes to be permanently disposed on the OU-8 property. The City argued that the EPA violated Denver’s ordinance prohibiting permanent radioactive waste sites by allowing Shattuck Chemical to dispose of 50,000 cubic yards of radioactive waste on its property.25 The U.S. Court of Appeals for the Tenth Circuit again ruled against Denver citing that CERCLA preempts the Denver Zoning ordinance.26 However, pressure to dispose of the radioactive waste off-site continued from concerned citizens, the media, and a 10,000 signature petition.

In October 1997, Mayor Webb announced that Denver would be suing the EPA citing that the EPA violated its own standards and procedures in deciding upon the current clean-up plan. The City cited four reasons why the EPA remedy was defective:

1. EPA failed to consider the existing and potential uses of groundwater. 2. EPA failed to consider state and federal radioactive waste disposal citing criteria at Shattuck that EPA considered at 10 other sites. 3. EPA failed to require the use of liners at the Shattuck site to contain contaminants as required by federal and state law. 4. EPA failed to require government ownership of the disposal site as required by state and federal law for radioactive disposal sites.27

A five-year review report for the Shattuck Site or OU-8 was conducted independently by SC&A, a consulting company, and was released on November 12, 1999. The purpose of the five-year review was to determine whether the remedy at the site was protective of human health and the environment. Also, the report provided a summary of the adequacy of the implementation of the remedy and changes to applicable or relevant and appropriate requirements (ARARs) and other risk-related factors. The report identified seven deficiencies that prevented the remedy from being protective:

1. Lack of institutional control of the plume outside the site boundary 2. Vulnerability of cover/monolith design to long-term degradation 3. Monolith-monitoring plan deficiencies 4. Plume-monitoring plan deficiencies 5. Site characterization and modeling deficiencies 6. Risk assessment deficiencies 7. Specific design technical issues that need to be re-evaluated28

Additionally, the State, City and County of Denver, stakeholders, and the local community requested alternative on-site containment remedies. The combination of concerns raised by the five-year review report, requests to reconsider the remedy, and the State’s withdrawal of support prompted the EPA to announce the removal of the radioactive waste through the guidance of an Amended ROD released on June 16, 2000. 29

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Amended ROD:

The ROD Amendment stipulated that the monolith be removed from the site along with any additionally identified contaminants in excess of cleanup levels specified in the Amended ROD.

Clean-up goals or Remedial Action Objectives (RAO’s) specified in the Amended ROD included:

 Eliminate the potential for direct contact with soil or ingestion of soil with potential to cause excess cancer risks greater than 10-6 from gamma radiation.  Eliminate the potential for inhalation of soil with the potential to cause excess cancer risks of greater than 10-6 from Th-230 in wind-blown dust and radon progeny.  Eliminate the potential for exposure to soil having Ra-226 activity levels greater than 5 pCi/g occurring in any six-inch layer of the monolith from its top surface to its bottom surface. This includes any original soils not incorporated into the monolith which are above the groundwater table.  Eliminate the potential for direct contact with soil or ingestion of soil with natural uranium (U- nat) activity levels greater than 75 pCi/g.  Eliminate the potential for inhalation of radon progeny at an activity greater than 0.02 working levels.  Eliminate the potential for future groundwater contamination.

On April 26, 2006, the EPA informed the US Army Corps of Engineers and Shaw Environmental that an additional remedial action criterion for molybdenum in soil had been established for the Shattuck site by regulatory agencies. The new screening criteria, below 390 milligrams per kilogram (mg/kg), was to be applied to soil lying beneath the footprint of a former molybdenum pond that was used to store wastewater and sludge from the former ore processing operations.30

Remedial Action: Original ROD

Remedial action executing the initial ROD included demolition of radium-contaminated buildings, excavation of radium-contaminated soil from the vicinity properties, Bannock Street, the storm sewer located east of Santa Fe Drive, and the Shattuck Chemical property, onsite stabilization/solidification of the radium-contaminated soil into a disposal cell, capping of the stabilized material, and installation of monitoring wells to evaluate the effectiveness of the remedy.

The remedial action was conducted in two phases beginning in September 1992 and concluding in September 1998. During Phase 1, approximately 67,345 tons of building debris were disposed of off-site and 8,700 cubic yards of contaminated soils were excavated from the vicinity properties. Approximately 200 cubic yards of asbestos-containing material were removed and disposed of under appropriate regulations, and approximately 400 cubic yards of contaminated soils were excavated from beneath Bannock Street. Approximately 65,000 loose cubic yards of radiologically contaminated soil excavated from Shattuck Chemical and the vicinity properties were stabilized/solidified onsite in a disposal cell. Stabilization/solidification of the radiologically contaminated material began in July 1996 and was completed in November 1997. Capping of the stabilized material was completed in June 1998.31 The 131

waste form was constructed on site by mixing contaminated soil, cement, fly ash, and water and was consolidated into a solidified cement/soil monolith with an actual volume of approximately 83,610 cubic yards. The remedy for the original ROD was completed in September 1998 and created a roller compacted cement/soil monolith of approximately 5 acres.

Oil-impacted soils were found onsite during remediation, and approximately 2,000 cubic yards of oil- impacted soils were excavated during Phase II activities from the Shattuck Chemical Property located at 1805 South Bannock Street. The material was covered and transported by truck to Conservation Services Inc. in Bennett, Colorado.* Bioremediation was used for the oil-impacted soils that extended beneath the completed portion of the monolith. A plan addressing the remaining soils contaminated with oil at OU-8 was submitted in August 1998. The bioventing system was approved by EPA and was installed in September 1998.

In 1997, the storm sewer along Santa Fe Boulevard west of the site was remediated, and in 1999, an additional section located north of the original section was remediated. The remediation consisted of using InSituForm to install a lining within the existing sewer lines, manholes, and inlet boxes.32

ICs included in the original ROD were site fencing, restrictions against excavating into the cover and stabilized materials, restrictions prohibiting the construction of enclosed structures on the site, restrictions against using groundwater beneath the site, and restrictions to prevent agricultural use of the site.33 A Construction Completion Report was submitted on September 29, 1998. Also, a plume-monitoring plan was developed and implemented in 1998, and a monolith-monitoring program consisting of 10 monitoring wells was developed and implemented in 1998.34

Management Plan: Bannock Street Segment

In March 18, 1999, Denver published a Management Plan for OU-8 to address public and worker exposure concerns and ultimate material disposal. Contaminated fill was known to be present in South Bannock Street between East Mexico Avenue and East Jewell Avenue. The management plan encompassed all activities that resulted in penetration of the affected streets’ pavement surface, curb and gutter, sidewalk, or excavation of contaminated materials below the street, and governed all maintenance, repair, or other construction activities on the OU-8 Bannock Street segment.

Remedial Action: Amended ROD

Implementation of the RAO’s stipulated by the Amended ROD began in September 2002 and concluded in September 2006. The U.S. Army Corps of Engineers, Omaha District managed the cleanup effort at the site for the EPA through a Total Environmental Restoration Contract. The remedial action contractor was Shaw Environmental and Infrastructure, Inc.35

* The September 2008 Five-Year Review states that the material was transported to Thornton, Colorado. 132

Building Erection

To control dust and minimize the potential for community exposure of airborne contaminants generated during demolition of the monolith, three structures were erected to cover:

1. Mining structure 2. Materials handling 3. Load-out operations

Cover Material Removal

A majority of the top rip-rap layer of the monolith cover had previously been removed from the site by International Technologies (IT) Corporation and disposed at an approved offsite facility. Prior to monolith demolition the remaining cover material was removed using suitable excavating equipment. Cover material was sampled and analyzed in 500 cubic yard lots. Cover materials were either used for on-site backfill, if suitable, or were moved to the load-out area for off-site transportation.

Monolith Demolition

Monolith demolition proceeded east to west within the mining structure. As monolith material was removed, it was transported to the west end of the mining structure, where it was sized to remove material greater than 18 inches and either loaded on the conveyor or stockpiled nearby. Composite samples were taken for laboratory analysis to confirm transportation and disposal characterization.

Soil underlying the monolith was surveyed through instrument surveys and then sampled and analyzed. Areas of underlying soil that displayed radiological activities that exceeded the Amended ROD criteria were excavated and transferred to the Load-out Structure for disposal at the approved off-site facility.

After underlying soils were excavated to the extent that Pre-Verification surveys and sample results indicated that the cleanup criteria was met, Final Status Survey (FSS) sampling was performed in accordance with the Final Status Survey Plan (FSSP). Independent verification sampling was performed in selected survey units by CDPHE.

Bannock Street Remediation

Remediation work to complete the removal of the east perimeter and Bannock Street ROW soils occurred from September 2005 to February 2006. Denver was responsible for reconstructing the street as remediation work was completed.

Perimeter Soils Removal

Samples were collected from each perimeter boring at 1 foot intervals. Sample results were used to establish subsurface intervals where radiological activity exceeded the activity specified in the Amended ROD and if required were excavated and disposed at the approved offsite facility. The sampling procedures followed during the borehole drilling were as follows:

 Boreholes will not be drilled within 12 inches of a known underground utility. 133

 The asphalt paving will be cut using a concrete saw with an attached water mist to minimize dust in order to access the potentially contaminated soils beneath the asphalt paving.  Once the potentially contaminated soils are accessible, a combination of a split-spoon sampler and a motorized drill rig or hand or power augers will be used to drill the boreholes.  The split-spoon samplers will be driven into the extracted from the ground unless refusal is encountered.  The split-spoon samplers and drill bit or hand or power augers will be decontaminated between each use.  The split-spoon samples will be surveyed for radioactivity using a shielded gamma scintillation probe.  The gamma scintillometer reading which corresponds to a Radium-226 concentration above the action level for subsurface soils will be estimated by comparing the gamma scintillometer readings to Radium-226 concentrations evaluated by the Opposed Crystal System (OCS).  Soil samples will be analyzed for Radium-226 concentrations using the OCS in accordance with Chapter 4.0 of the Field Assessments Procedures Manual prepared for the U.S. Department of Energy Uranium Mill Tailings Remedial Action Project.

The investigation included drilling 9 new boreholes in the 1700 block of South Bannock Street and 13 boreholes in the 1800 block of South Bannock Street. All of the proposed were drilled to a depth of 3 feet except for one which will be drilled to a depth of 6 feet due to its proximity to potentially deep contamination on the shoulder.36

Molybdenum Soils Removal

To begin remediation of the former molybdenum pond, soil beneath the footprint of the pond was excavated to bedrock and placed in 500 cubic yard stockpiles at other locations around the site. Soil samples were collected from the excavator bucket as each stockpile was being constructed and analyzed on-site by gamma spectroscopy analysis for site Radionuclides of Concern (ROC’s) and molybdenum.

If the materials contained ROC’s in excess of the Amended ROD criteria, the stockpiles were loaded and shipped to the approved off-site facility receiving radiological materials from Shattuck. If the radiological criteria were not exceeded, but the soil contained molybdenum in excess of the screening criteria, the stockpiles were loaded and transported for disposal at an approved local landfill. If the material contained neither ROC’s nor molybdenum in excess of the Amended ROD or screening criteria, the stockpiles were retained on-site to be used as backfill.37

Independent Verification and Final Status Surveys

A Final Status Survey of the Mining Structure at the Shattuck Chemical Superfund Site was conducted between March 7 and March 16, 2006. The free release criteria specified in Army Regulation (AR) 11-9 are:

 Removable alpha = 20 disintegrations per minute per 100 square centimeters (20dpm/100cm2)  Total alpha (fixed + removable) = 500 dpm/100cm2  Removable beta = 1000dpm/100cm2  Total beta (fixed + removable) = 5000dpm/100cm2 134

The mining structure and ancillary equipment met the free-release criteria specified in project plans and license conditions. The mining structure and ancillary equipment were free-released for disposal or recycling as elected by the demolition contractor.38

CDPHE was tasked to conduct that independent verification (IV) of the Shattuck Site. The IV survey consisted of performing document reviews, conducting gamma exposure rate measurements, and collecting soil samples to formally document the radiological levels in the soil after clean-up in 25 percent of the survey units. Results of the IV showed that clean-up efforts at the site met the remedial active objectives for radium-226, thorium-230, and uranium in soil based on survey results documented in the final status surveys conducted by the remedial action contractor. The conclusion was further supported by the analytical results collected as part of the IV. However, the IV did not address metals or groundwater. The IV statements were issued for each survey unit as the project progressed between March 2005 and September 2006.39

Backfill

Backfill and site restoration activities progressed from south to north, independent of the mining, materials handling, and railcar loading operations. A survey unit (SU) was not backfilled until CDPHE had concurred with the results of the FSS report for that SU and at the direction of the US Army Corps of Engineers.

Backfill material consisted of reclaimed cover material or reclaimed fill from underlying and perimeter soil excavation, if the radiological activities were below the Amended ROD criteria. Additional materials were brought in from offsite sources. The backfill material was placed into approved survey units and spread in loose horizontal lifts approximately 8 to 12 inches thick. The materials were then compacted by traversing the area with a dozer or wheel loader.

Site Restoration/Vegetation

The site was graded to its final configuration, and a vegetative cover was established over the site by hydro-seeding. A detention pond, connected to Denver storm sewer system, was constructed at the north end of the property. A final land survey was completed to document the final grade of the site.40

The radiological materials were classified as technologically enhanced naturally occurring radioactive materials (TENORM) and were shipped to the US Ecology Site in Idaho. A total of 2,252 rail cars containing over 243,000 tons of material were shipped to the disposal facility. Transportation of the material was the responsibility of a separate contractor under a specific radioactive materials license (New Horizons Environmental Consulting).41 Molybdenum containing soils were shipped to the CBI, Inc. RCRA Subtitle D landfill in Adams County, Colorado.42

Explanation of Tables 3-5

Formerly Utilized Sites Remedial Action Program (FUSRAP) is a program commencing in 1997 when Congress directed the U.S. Army Corps of Engineers to conduct assessment, remedial action, and site closure activities for sites in accordance with a Memorandum of Understanding between the Corps and the Department of Energy (DOE). The waste generated at FUSRAP sites typically consists of low-level radioactive material such as uranium, thorium and/or radium, with some mixed waste.43 Naturally 135

Occurring Radioactive Materials (NORM) include primordial radionuclides that are naturally present in the rocks and minerals of the earth’s crust and cosmogenic radionuclides produced by interation of cosmic nucleons with target atoms in the atmosphere and in the earth.44

Tables 3-5 detail the monthly totals in cubic yards and cubic feet of contaminated material handled, transported and disposed of in the years 2003 through 2005. The contaminated material was stored at the temporary storage facility was disposed at one or more of the following facilities:

 Envirocare in Utah;  Envirosafe in Idaho; or  WCS in Texas.45

Table 3: Shattuck FUSRAP/NORM Loads Material Received 200346

2003 Type of Material Monthly Total CY Monthly Total CF (ft3) (yd3) January NA 0 0 February NA 0 0 March NORM 2,090.7 56,448.9 April NORM 3,767.4 101,719.8 May NORM 5,554.3 149,966.1 June NORM 6,797.6 183,535.2 July NA 0 0 August NORM 4,257.0 114,939.0 September NORM 6,134.7 165,636.9 October NORM 5,620.4 151,750.8 November NORM 4,202.9 113,478.3 December NORM 6,487.0 175,149.0

TOTAL 44,912.0 yd3 1,212,624.0 ft3

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Table 4: Shattuck FUSRAP/NORM Loads Material Received 200447

2004 Type of Material Monthly Total CY Monthly Total CF (ft3) (yd3) January NORM 6,933.3 187,200.7 February NORM 6,074.3 164,006.3 March NORM 3,865.0 135,660.7 April NORM 7,816.7 211,051.7 May NORM 6,388.1 172,478.7 June NORM 4,198.2 113,351.4 July NORM 8,544.8 230,710.8 August NORM 5,515.8 148,926.6 September NORM 5,936.3 160,280.1 October NORM 6,651.3 179,585.9 November NORM 6,550.4 176,860.8 December NORM 3,768.3 101,744.1

TOTAL 72,242.5 yd3 1,981,857.8 ft3

Table 5: Shattuck FUSRAP/NORM Loads Material Received 200548

2005 Type of Material Monthly Total CY Monthly Total CF (ft3) (yd3) January NORM 9,036.5 243,985.5 February NORM 4,376.8 118,173.6 March NORM 4,850.9 130,973.8 April NORM 7,131.1 192,540.2 May NORM 5,036.2 135,978.9 June NORM 3,180.7 85,877.7 July NORM 6,296.7 170,010.9 August NORM 2,850.6 76,966.8 September NORM 503.2 13,587.4 October NORM 5,854.4 158,068.2 November NORM 2,638.3 71,234.9 December NORM 3,275.3 88,432

TOTAL 55,030.7 yd3 1,485,829.9 ft3

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Explanation of Significant Differences

In March 2007, the EPA published an Explanation of Signification Differences for OU-8, Shattuck Chemical Site. Three significant differences were identified from the Amended ROD:

1. The initial volume of material to be removed and disposed of was underestimated in the Amended ROD. 2. The average density of the excavated material was higher than expected. 3. Extreme weather caused unanticipated expenditures.

1. The initial volume of material to be removed and disposed of was under-estimated in the Amended ROD:

Based on past remedial action, the Amended ROD projected a total of 165,000 tons of monolith material, underlying soils, and perimeter soils would be generated for off-site disposal by remedial actions at the site. At project completion in September 2006, approximately 243,872 tons of radiological contaminated materials were transported to the US Ecology facility. The final tonnage included additional radioactive materials from Bannock St, from the perimeter of the monolith area (including the removal of clean fill used in the original remedy) and material from the molybdenum pond area located at the north end of the site.

Approximately, 31,515 tons of molybdenum containing soil was excavated from beneath the area of the former molybdenum ponds found at the north end of the Shattuck property. The site team discovered that the molybdenum concentrations in groundwater were much higher (10 to 100 times the ARAR concentration of 0.1 mg/L) than could be reasonably expected to attenuate without source removal. Further complicating the situation, the site team discovered that backfill material used in molybdenum pond area contained radionuclide concentrations above the clean-up standards established in the Amended ROD. Consequently, it was determined that source removal at the molybdenum pond area was required. At the end of the project a total of approximately 275,387 tons of material from the monolith and molybdenum containing soils were excavated and disposed of at approved off-site facilities at a final cost of $57,126,558.06.

2. The average density of the excavated material was higher than expected:

The under-estimation of the weight-to-volume ratio of excavated material resulted in remedial cost at the site to be higher than expected. The average density of the excavated monolith material was estimated in the Amended ROD to be approximately 2,600 to 3,000 pounds per cubic yard. The actual density of the material ranged from 3,400 to 3,800 pounds per cubic yard. As a result, a lower volume of material could be loaded into each railcar before its maximum weight limit was reached, increasing the number of railcars needed to transport the material and transportation costs.

3. Extreme weather caused unanticipated expenditures:

During March (heavy snowstorm), July, and December (high wind events) 2003, three separate weather events impacted the Shattuck Site with unforeseen repair and maintenance to the protective structure at the site.49 138

Institutional Controls

In July 1996, the Denver City Council adopted an ordinance (No. 145) that required radium disposal fee to recover costs associated with the burial of radium contaminated soils. Shattuck Chemical Company filed suit in December 1996 challenging the ordinance. In response, the City of Denver filed counterclaims seeking response costs under CERCLA and damages for trespass and nuisance. In July 1997, the United States filed suit against Denver’s radium disposal fee citing:

 Preemption under the Supremacy Clause;  Impermissible discrimination against Shattuck Chemical Company, the U.S., and any party performing a remedy on a radioactive waste site in Denver pursuant to EPA order, and;  Assessment of an impermissible tax against the U.S.

Denver submitted a counterclaim to the U.S. citing response costs under CERCLA because the Bureau of Mines operated one of the radium mills that contaminated property in Denver. Also, Denver submitted a counterclaim for denial of due process in using City property as part of the EPA remedy. As a result, the Shattuck and U.S. cases were consolidated. Denver and Shattuck settled the dispute in 1999 resulting in Shattuck paying Denver $654,000 to settle all claims.50

Currently an informational IC exists for Ou-8 by the Colorado State Engineer requiring notification for new groundwater water wells.51 The State Engineer has agreed to include on each permit application correspondence, each well permit, and each acknowledgement for a Monitoring Hole Notice of Intent for the affected area, a notice that the applicant should contact the CDPHE and the EPA for information regarding groundwater quality. If any person seeks to drill a well into groundwater in this area, the State Engineer notifies that person that the groundwater is contaminated. The individuals also are notified that they should contact the EPA and CDPHE. The State Engineer will send a copy of the well permit and copies of all correspondence or well permits containing the notice to the CDPHE and EPA. The affected areas have been delineated by EPA and CDPHE. 52

The Amended ROD called for complete removal of contaminated soils at the Shattuck site, and the remedial actions performed at Shattuck were successful in removing all contaminated materials from the site soils. Therefore, ICs are not required for the soil on this property, and no operation and maintenance activities are necessary to monitor the effectiveness of the remedy.

CDPHE will continue to conduct monitoring of the groundwater associated with OU-8. CDPHE recommended in May 2012 that the groundwater monitoring frequency should be reduced to a semi- annual basis to allow for natural attenuation of site related contaminants. Monitoring frequencies were changed to twice per year based on low and high water table regimes.53

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De-listing

As of the last Five-Year Review in September 2008, OU-8 was vacant with no structures were present on- site. Following construction completion, the property was sold for redevelopment.

A Final Close-Out Report was signed on September 27, 2006.54 In a letter dated January 2, 2008, the CDPHE concurred with the EPA’s intent state in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.55 On November 8, 2010 the direct partial deletion became final, and the majority of OU-8 of the Denver Radium Superfund Site was deleted from the NPL. The groundwater at OU-8 is the only portion of the Denver Radium Superfund Site that remains on the NPL.56

140

Bibliography

City and County of Denver. March 11, 1993. Letter to Dr. Pat Nolan (CDPHE) and Robert Duprey (USEPA).

City and County of Denver: Department of Zoning Administration. May 11, 1994. Order to Cease and Desist: Re: 1805-75 S. Bannock Street.

City and County of Denver. March 11, 1996. Press Release: “Keep Radioactive Waste Out of Denver Neighborhoods.”

City and County of Denver. October 10, 1997. Press Release: “Mayor Announces City Lawsuit Against EPA Over Shattuck Site.”

City and County of Denver. July 25, 2004. Settlement of Denver Radium Superfund Site Lawsuit; U.S. v. Denver, Civil Action No. 97-D-1611.

Colorado Department of Public Health and Environment, 2003. Five-Year Review Denver Radium Site. September 30, 2003.

Colorado Department of Public Health and Environment. September 2007. Confirmatory Survey and Review Report: Shattuck Chemical Superfund Site, OU-8 Denver Radium Superfund Project, Final Report.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

Environmental Management Support, Hammer, Siler, George Associates. July 23, 1999. Study to Evaluate Reuse Options.

Faught, John, Professional Attorney. June 10, 1994. Exhibit One: Notification of Appeal.

Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations.

Rocky Mountain Compact States. January 15, 2004. December 2003 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS).

Rocky Mountain Compact States. January 10, 2005. December 2004 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS).

Rocky Mountain Compact States. January 5, 2006. December 2005 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS).

SC&A, Inc. November 12, 1999. Final Report: Five-Year Review Report. EPA Contract Number 68- D7-0001

Shaw Environmental Inc. September 2006. Revised Final Remedial Action Completion Report. Shattuck Chemical Superfund Site. Contract No. DACA 45-96-D-0007. Task Order No. 0031.

State of Colorado. January 2, 2008. Notice of Deletion. 141

U.S. Department of Justice. February 23, 1996. Press Release: “Judge Orders Long-Awaited Clean-up of Denver Radioactive Waste Site Denies City’s Attempt to Block Cleanup.”

U.S. Environmental Protection Agency. January 28, 1992. Superfund Record of Decision Denver Radium (Operable Unit 8), Denver, CO.

U.S. Environmental Protection Agency. January 1994. Remedial Design/Remedial Action. Denver Radium Operable Unit 8.

U.S. Environmental Protection Agency. January 26, 1994. Re: Denver Radium Superfund Site, Shattuck Chemical Company

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report. Denver Radium Superfund Site.

U.S. Environmental Protection Agency. March 2007. Explanation of Significant Difference- Shattuck Chemical Site OU-8.

U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site.

U.S. Department of Justice. November 30, 1996. CERCLA Preempts Denver Zoning Law. Colorado Compliance. P. 14.

State of Colorado. September 20, 2006. Final Status Survey of the Mining Structure to Support Free Release Shattuck Chemical Superfund Site, Denver, Colorado.

142

Endnotes

1 U.S. Environmental Protection Agency. January 28, 1992. Superfund Record of Decision Denver Radium (Operable Unit 8), CO. 2 SC&A, Inc. November 12, 1999. Final Report: Five-Year Review Report. EPA Contract Number 68-D7-0001 3 U.S. Environmental Protection Agency. January 28, 1992. 4 SC&A, Inc. November 12, 1999. 5 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium 6 SC&A, Inc. November 12, 1999. 7 U.S. Environmental Protection Agency. September 25, 2006. 8 SC&A, Inc. November 12, 1999. 9 Shaw Environmental Inc. September 2006. Revised Final Remedial Action Completion Report. Shattuck Chemical Superfund Site. Contract No. DACA 45-96-D-0007. Task Order No. 0031. 10 U.S. Environmental Protection Agency. September 25, 2006. 11 U.S. Environmental Protection Agency. January 28, 1992. 12 U.S. Environmental Protection Agency. June 16, 2000. EPA Superfund Record of Decision Amendment: Denver Radium Site 13 U.S. Environmental Protection Agency. January 28, 1992. 14 U.S. Environmental Protection Agency. January 28, 1992. 15 U.S. Environmental Protection Agency. January 28, 1992. 16 U.S. Environmental Protection Agency. January 28, 1992. 17 U.S. Environmental Protection Agency. January 28, 1992. 18 18 Shaw Environmental Inc. September 2006. 19 U.S. Environmental Protection Agency. January 1994. Remedial Design/Remedial Action. Denver Radium Operable Unit 8. 20 City and County of Denver. March 11, 1993. Letter to Dr. Pat Nolan (CDPHE) and Robert Duprey (USEPA). 21 U.S. Environmental Protection Agency. January 26, 1994. Re: Denver Radium Superfund Site, Shattuck Chemical Company. 22 City and County of Denver: Department of Zoning Administration. May 11, 1994. Order to Cease and Desist: Re: 1805-75 S. Bannock Street. 23 Faught, John, Professional Attorney. June 10, 1994. Exhibit One: Notification of Appeal. 24 U.S. Department of Justice. February 23, 1996. Press Release: “Judge Orders Long-Awaited Clean-up of Denver Radioactive Waste Site Denies City’s Attempt to Block Cleanup.” 25 City and County of Denver. March 11, 1996. Press Release: “Keep Radioactive Waste Out of Denver Neighborhoods.” 26U.S. Department of Justice. November 30, 1996. CERCLA Preempts Denver Zoning Law. Colorado Compliance. P. 14. 27 City and County of Denver. October 10, 1997. Press Release: “Mayor Announces City Lawsuit Against EPA Over Shattuck Site.” 28 SC&A, Inc. November 12, 1999. 29 U.S. Environmental Protection Agency. September 25, 2006. 30 Shaw Environmental Inc. September 2006. 31 SC&A, Inc. November 12, 1999. 32 SC&A, Inc. November 12, 1999. 33 Shaw Environmental Inc. September 2006. 34 SC&A, Inc. November 12, 1999. 35 Colorado Department of Public Health and Environment. September 2007. Confirmatory Survey and Review Report: Shattuck Chemical Superfund Site, OU-8 Denver Radium Superfund Project, Final Report. 36 SC&A, Inc. November 12, 1999. 37 Shaw Environmental Inc. September 2006. 38 State of Colorado. September 20, 2006. Final Status Survey of the Mining Structure to Support Free Release Shattuck Chemical Superfund Site, Denver, Colorado.

39 Colorado Department of Public Health and Environment. September 2007. 143

40 Shaw Environmental Inc. September 2006. 41 Colorado Department of Public Health and Environment. September 2007. 42 U.S. Environmental Protection Agency. September 25, 2006. 43 U.S. Army Corps of Engineers. 2014. 44 U.S. Environmental Protection Agency. August 30, 2012.

45 Rocky Mountain Compact States. January 15, 2004. December 2003 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS). 46 Rocky Mountain Compact States. January 15, 2004. December 2003 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS). 47 Rocky Mountain Compact States. January 10, 2005. December 2004 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS). 48 Rocky Mountain Compact States. January 5, 2006. December 2005 FUSRAP/NORM Monthly Report for Rocky Mountain Compact States (RMCS). 49 U.S. Environmental Protection Agency. March 2007. Explanation of Significant Difference- Shattuck Chemical Site OU-8. 50 City and County of Denver. July 25, 2004. Settlement of Denver Radium Superfund Site Lawsuit; U.S. v. Denver, Civil Action No. 97-D-1611. 51 U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site. 52 Colorado Department of Public Health and Environment. September 30, 2008. Five-Year Review, Denver Radium Site 53 United States Environmental Protection Agency. May 2012. 54 Colorado Department of Public Health and Environment. September 30, 2008. 55 State of Colorado. January 2, 2008. RE: Notice of Deletion 56 Federal Register. September 9, 2010. Vol. 75, No. 174/ Rules and Regulations. 143

Denver Radium Superfund Site

Operable Unit 10

Table of Contents:

Background Information 144 Remedial Investigation 145 Remedial Objectives/Record of Decision 146 Remedial Action 146 Institutional Controls 148 De-listing 149 Bibliography 150 Endnotes 150

Tables and Figures:

Table 1: Operable Unit 10 Property 145 Table 2: Materials Left in Place as Averaged Areas: OU-10 147

144

Background Information

Denver Radium Operable Unit 10 (OU-10) comprised the 17.2 acre Card property located at 1314 West Evans Avenue. The property is bounded on the north and east by commercial office buildings and some light manufacturing and storage buildings, bounded on the west by Colorado and Southern railroad property, and bounded to the south by the Public Service Company and West Wesley Avenue.1

OU-10 is underlain by a sequence of fill, alluvial sand and gravel, and the Denver Formation. Depth to groundwater is approximately 20 feet, and depth to bedrock is approximately 10 feet. OU-10 does not lie within the 100-year floodplain.2

In 1890, Overland Cotton Mill initially built a brick building on what is now the 1314 West Evans Avenue property. Due to a coal strike in 1903, the cotton mill closed. In 1920, the Pittsburgh Radium Company (PRC) purchased the property with a goal of processing 120 tons of carnotite ore monthly. The PRC operated until radium production ceased in the United States in 1923 and converted the plant to a vanadium producing mill for one more year until 1925. It was estimated that in 1924, PRC may have processed as much as 10 tons of vanadium daily from roscoelite.

In 1939, Colorado Builders Supply Company purchased the PRC property, and the brick building was converted to a projectile and munitions manufacturing facility known as Mariposa Works. In the early 1940s, the building was gutted by a fire. The building was renovated and projectile manufacturing continued on the property until the mid-1950s. Following, a variety of industrial operations such as hardware manufacturing, mining equipment manufacturing and repairing, and steel truss manufacturing occurred on the property. The Colorado Historical Society has placed the brick building originally used as a cotton mill on the National Register of Historic Places.

Four structures were located on this property at the time of Remedial Investigation (RI): a brick commercial building, an office building, the UPL building, and the True Truss building. In the summer of 1985, a Consolidated Freightways facility, consisting of a building and a paved lot, was constructed on the south end of the property.3

As listed in the OU-10 Closeout Report published in March 1992, the following businesses occupied the OU-10 property:

 Noisaire, a commercial air conditioning manufacturer;  Mentor Corporation, a real estate firm;  KAI Enterprises, a woodworking business;  Hinton Steel, a steel supply company; (1401 W Wesley Ave, Denver, CO 80223)  Hercules, a sheet metal and duct work manufacturer; (1310 West Evans Ave. Denver, CO 80223) and  Consolidated Freightways, a trucking terminal.

The responsible party search failed to trace the Pittsburgh Radium Company to a viable, present-day entity and failed to connect that the present owners had any record of having been connected with the activities that caused the site to be contaminated with radioactivity.4

145

Table 1: Operable Unit 10 Property:

Property Name at Time of Address Operable Unit ROD OU-10 Card Corporation 1314 West Evans Ave

Remedial Investigation

The RI and Feasibility Study (FS) were prepared by Jacobs Engineering Group and CH2M Hill on behalf of the EPA in June 1987. The RI focused on radium and uranium processing residues discarded in the early 1900s containing uranium, radium, thorium. The primary contaminants of concern at OU-10 included gamma radiation associated with radiologically-contaminated soils; radon gas and radon decay products in indoor air spaces; and alpha and beta particles associated with the radioactive decay of radon. Radiological data were collected from a radiation survey conducted in 1985 as part of the RI. A grid-scan survey at the 3-foot level was conducted in open areas. In areas where elevated gamma radiation levels were detected, surface gamma radiation exposure measurements were also taken. Contamination was found in open areas, and under structures and pavement. Forty-one areas of surface and subsurface radiologic soil contamination were identified on the property.5

The estimated volume of contaminated soil was 3,923 cubic yards, and 3,448 cubic yards of contaminated soils were estimated to be in open areas. Also, OU-10 was estimated to have 200 cubic yards of contaminated sediments from the pond, and 10 ft2 of a contaminated brick wall. Four hundred seventy- five cubic yards of the contaminated soils lie under structures at a maximum depth of 42 inches. Depths of open area contamination ranged from 6 to 108 inches.6 Individual maximum readings ranged from 5.8 pCi/g to 960 pCi/g. Sediment samples were collected both near the pond and from the bottom of the pond. Samples adjacent to the pond contained 23 pCi/g of radium. Two sediment samples were taken from the pond bottom and contained 6.3 and 3.4 pCi/g of radium-226 indicating that at least some of the sediments on the pond bottom and surrounding the pond were contaminated. The volume of radiologically contaminated sediments was estimated to be 200 cubic yards. One sample of airborne radon particulates located in the UPL Building in an unventilated closet was above Federal standards (0.03 WL maximum) with a concentration of 0.0435 WL. Analytical results from groundwater samples indicated that site groundwater was not contaminated with radiologic material.7

A Supplemental Radiological Data report was completed for OU-10 on March 1988 to confirm previously collected data and to further characterize the lateral and vertical extent of the radiological contamination. Surface gamma exposure-rate scans were performed over the entire portion of OU-10 to re-establish areas considered contaminated and to assess possible changes in site conditions. Gamma exposure-rates ranged from 15 µR/g to 1154 µR/g. Radium concentrations in the contaminated areas ranged from 7 pCi/g to 6,794 pCi/g, and depths of contamination ranged from 6 inches to 81 inches. In several areas, contamination was detected beneath 2 to 3 feet of uncontaminated overburden. The major area where contamination was not detectable at the surface was the area adjacent to two of the railroad spurs.

The extent of contamination identified in the Supplemental Radiological Data report was approximately double the volume that was identified in previous reports. The major differences resulted from the extent 146

of contamination associated with railroad spurs and additional contamination identified in the south end of the UPL building.

Remedial Objectives/Record of Decision

The selected remedy in the June 30, 1987 ROD included full removal and permanent off-site disposal.

The scope of remedial action included:

- Excavation of approximately 4,000 cubic yards of radium-contaminated soil and sediment from the Card property; - Storage of the contaminated material within reinforced synthetic bags placed within the True Truss building and within possible additions to the building; - Optional staging and storage of contaminated material from selected other Denver Radium Site properties on the Card property- the total amount of material to be staged or stored on the Card property not to exceed 13,000 cubic yards including the contaminated material already present on the Card property; - Final removal of all contaminated material to facility suitable for the permanent disposal of Denver Radium Site wastes; and - Decontamination and dismantling of True Truss building and any additions and disposal of the material in a sanitary landfill. - Draining the waste pond, if necessary, to remove liquids and contaminated sediments.

However, the plan to use the True Truss building for on-site storage of the contaminated material in synthetic bags was abandoned when a permanent disposal facility operated by Envirocare of Utah, Inc., in Tooele County, Utah became available in 1988.8

Remedial Action

Remedial activities at OU-10 were conducted in two phases beginning in September 1988 and concluding on September 22, 1989. While the initial radiological assessment identified 10,694 tons of radioactive material at depths ranging from 0 to 81 inches, the actual quantity of contaminated material removed totaled 15,021 tons at depths ranging from 0 to 80 inches. No extensive changes were made to the major structures on the property, although several small structures were removed and not replaced at the request of the owner.

During Phase 1, remedial action involved the decontamination and reconstruction of the site and temporary on-site stockpiling of contaminated materials. The material was stockpiled in the southwest corner of the property in a designated load-out area. Following the removal of the stockpile, samples were taken to ensure that all contaminated materials were removed.

Asbestos was known to be present at OU-10. Removal of asbestos was limited to what was necessary to conduct remediation activities. The material was removed in accordance with Chapter 4-9 of the Revised Municipal Code of Denver. Three underground storage tanks were removed as well as abandoned utilities such as wires and pipes throughout the property. 147

Two areas in the Norsair Building required additional investigations and the usage of area-averaging calculations over a 100 square meter area because of considerations that included cost-effective and safe removal of contaminated material.

Table 2: Materials Left in Place as Averaged Areas: OU-10*

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-10 Area A 50 6.7 pCi/g Beneath the large air compressor in the Norsair Building OU-10 Area B 445 13.6 pCi/g Beneath a punch press in the Norsair Building

Contaminated materials were excavated using front end loaders while field personnel monitored the excavated area for remaining contamination using hand-held radiation detectors. Soil samples were collected and analyzed to verify that excavation activities achieved conformance with the applicable standards. After excavation of contaminated materials, samples representative of the 6-inch thick soil layer at the bottom of each verification area were collected and blended to create a composite sample for the specific verification area. All of the composite samples were analyzed by the Opposed Crystal System (OCS) to evaluate radium concentrations in the field for excavation-control decisions. Some soil samples, including those analyzed by the OCS, were sent to the Geotech Analytical Laboratory for high- resolution gamma spectrometer confirmation analysis.

Due to a large amount of past industrial activities and the presence of an oil and waste pond at the OU-10 site, additional sampling was conducted to determine non-radiological contamination. Nineteen soil samples were collected from the oil and waste pond at 10-foot intervals. Analysis of the soil samples by the Extraction Procedure (EP) toxicity method indicated that contaminant levels were below RCRA regulatory limits. Test results from Jacobs Engineering Group confirmed that aliphatic hydrocarbons (oil) and trace quantities of polychlorinated biphenyls (PCBs) were present near the pond, but the quantities were within standards. Polynuclear aromatic hydrocarbons were detected in soil and were stockpiled adjacent to the east side of the main stockpile. This area was windrowed and aerated. Prior to removal of materials, the area was monitored for contamination, and no detectable quantities were found.

Contaminated materials were transported by rail in covered gondola cars to the permanent off-site facility. The disposal contractor loaded material directly onto the cars at the site. Each gondola car was sealed, surveyed, and decontaminated, as necessary, prior to leaving the site. Gondola cars were only used for transportation of wastes from the Denver Radium Site. A composite sample was taken during the load- out of each gondola car and analyzed for Ra-226, Th-230, and EP toxic metals to determine that the

* Area averaging calculates the exposure risk of several readings from a 10 meter by 10 meter (100 sq/m) area. These calculations are considered below the EPA surface standard if they are less than 5 pCi/g above background and below the subsurface standard if they are less than 15 pCi/g above background. Background for the Denver Radium Site is 2 pCi/g. If calculations are below these standards, then the area is considered safe for unrestricted use and unrestricted access.

148

material was acceptable to the disposal facility. Non-radiological contaminated material containing asbestos and radiological waste was stored in barrels and shipped to the Envirocare Facility by rail. The wastes were labeled “Denver Radium Superfund Waste,” and the cars were transported to Utah via Wyoming.

Air particulate measurements were collected using Model LV-1 low-volume air particulate samplers manufactured by F&J Specialty Products, Inc. Each sampler was contained in an environmentally protected shelter and was connected to a dedicated electrical power outlet. The samplers were operated continuously for seven days at a nominal rate of five liters per minute. The filters were analyzed by the Geotech analytical laboratory for natural uranium, Th-230, Ra-226, and polonium-210 (Po-210). All airborne radionuclide concentrations measured during the reporting period were below the applicable regulatory standard (10 CFR 20).

Direct external gamma exposure measurements were collected using Harshaw TLD dosimeters. The dosimeter was essentially a thin plastic card that encapsulated five thermoluminescent elements. The cards were submitted to the DOE-Idaho Falls Dosimetry Laboratory for analysis. All gamma exposures measured during the reporting period were below the limit of 100 millirems per year (mrem/yr) above background. The background exposure rates for the Denver area range from 130 to 175 mrem/yr (EPA, 1986).

Institutional Controls

Ou-10 has been remediated to meet the clean-up standards specified in the ROD, and no operation and maintenance is required for this remedy. The current condition of the site allows for unrestricted use and unrestricted exposure, and the EPA will not conduct a 5-year review of the remedial action.

A site visit and inspection performed in August 2003 confirmed that all properties at OU-10 remain under commercial and industrial use.

While a five-year review is not required at OU-10, the Superfund Final Closeout report recommends that the locations of the waste left in place should be tracked with the established GIS database for proper disposal during potential future development.9

149

De-listing

A Final Close-Out Report was signed on September 27, 2006.10 In a letter dated January 2, 2008, the CDPHE concurred with the EPA’s intent state in the Notice of Deletion of the Denver Radium Superfund Site from the NPL.11 On November 8, 2010 the direct partial deletion from the NPL became final, and all of OU-10 of the Denver Radium Superfund Site was deleted from the NPL.

150

Bibliography

CH2MHill. April 24, 1987. Feasibility Study: Denver Radium Site Operable Unit 10.

Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008.

Federal Register. September 9, 2010 . Vol. 75, No. 174/ Rules and Regulations.

RUST Geotech Inc. March 1992. Denver Radium Site Operable Unit 10 Close Out Report for the U.S. Environmental Protection Agency.

State of Colorado. January 2, 2008. RE: Notice of Deletion

U.S. Environmental Protection Agency. April 23, 1987. Executive Summary and General Questions and Answers from the Final Feasibility Study: Denver Radium Site Operable Unit 10.

U.S. Environmental Protection Agency. June 1987. Superfund Record of Decision: Denver Radium/Card Property, CO.

U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Superfund Site.

Endnotes

1 U.S. Environmental Protection Agency. April 23, 1987. Executive Summary and General Questions and Answers from the Final Feasibility Study: Denver Radium Site Operable Unit X. 2 RUST Geotech Inc. March 1992. Denver Radium Site Operable Unit 10 Close OutReport for the U.S. Environmental Protection Agency. 3 CH2MHill. April 24, 1987. Feasibility Study: Denver Radium Site Operable Unit X. 4 U.S. Environmental Protection Agency. June 1987. Superfund Record of Decision: Denver Radium/Card Property, CO. 5 CH2MHill. April 24, 1987. 6 RUST Geotech Inc. March 1992. 7 CH2MHill. April 24, 1987. 8 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium Superfund Site. 9 U.S. Environmental Protection Agency. September 25, 2006 10 Colorado Department of Public Health and Environment, 2008. Five-Year Review Denver Radium Site. September 30, 2008. 11 State of Colorado. January 2, 2008. RE: Notice of Deletion 151

Appendix 1 Operable Unit Maps

152

153

OU-6B

154

155

156

Operable Unit 6 Properties OU-6A- Colorado and Southern Railroad/Centennial State Tire and Retread Company

157

OU-6B Denver Water Department Property (1190 Yuma Street) (*See Operable Unit 1 and 2 Photo)

158

OU-6C Allied Chemical and Dye Corporation (1271 West Bayaud Ave)

159

OU-6D The Public Service Company of Colorado Property

160

OU-6E Ruby Hill Park property

161

OU-6F Brannan Sand and Gravel property (61st Avenue and Clear Creek) Source: Google Maps (2013)

162

OU-6 Environmental Materials Incorporated property (1155 West 5th Avenue) and alley between Mariposa and Lipan extending between 5th and 6th Avenue

163

Operable Unit 7:

164

165

166

167

168

169

Appendix 2 Radium Waste Left in Place

169

Operable Volume of Waste Left in Place: Materials Left in Institutional Controls Operation and Maintenance Unit Place as Averaged Supplemental Standards Areas 1 NONE YES NONE NONE 2 11,060 yd3 YES Denver Ordinance, O&M Plan  Monitor ICs and maintain a and signed and executed an radon venting system at the (Atlas Metals- 1100 Umatilla Street environmental covenant on 1100 Umatilla property. and Burlington Northern Railroad- June 25, 2006 (restricts  Monitor compliance of the between 10th and 11th Avenues) disturbance of the concrete cap IC at the Burlington and subsurface soil and prohibits Northern property. use of groundwater) 3 Groundwater contamination- natural YES Denver Ordinance and  Monitor compliance of the attenuation is expected informational IC for IC at 1377 South Jason groundwater Street, Central and Sierra (Central & Sierra Railroad-Between Railroad ROW between W. Louisiana and W. Florida Streets) West Louisiana and West Florida Streets, and 1140 W. Louisiana  CDPHE monitors groundwater 4 Home Depot- 500 South Santa Fe YES Denver Ordinance, Home  O&M required at 500 South Drive Depot USA Notice and Santa Fe Drive Covenant  Inspect and maintain the Post Consolidation Area of contamination and monitor compliance with the IC at the Home Depot property 5 NONE YES NONE NONE 6 NONE * A gamma survey conducted YES NONE NONE in January 2004 confirmed that no IC’s were required and that all waste appeared to have been removed.* 7 NONE NO NONE NONE 8 Groundwater contamination NO Information IC for CDPHE monitors groundwater, 170

groundwater, Declaration of notification requirements exist for Covenants and Restrictions new groundwater wells. filed and recorded by Shattuck Chemical (restricts use of the surface and groundwater) 9-A NONE YES NONE NONE 9-B Groundwater contamination NO Informational IC for CDPHE monitors groundwater, (ROBCO) groundwater notification requirements exist for new groundwater wells. 10 NONE YES NONE NONE 11 NONE NO NONE NONE 171 Materials Left in Place as Averaged Areas-OU-11

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-1- Figure 2, Area 60 6.8 pCi/g Adjacent to and Materials A/Phase B beneath the Handling south foundation Building footer of the lower office level OU-1- Figure 2, Area 27 5.6 pCi/g Adjacent to and Materials B/Phase B beneath the Handling southern Building foundation in the lower office level OU-1- Figure 2, Area 105 7.7pCi/g West side of the Materials E/Phase B foundation Handling footing under Building the showroom OU-1- Figure 2, Area 193.5 12.0 pCi/g Beneath Erickson A/Phase C restrooms and Monuments front office OU-1- Rudd Figure 2, Area 430.5 15.0 pCi/g Under attached Investments B/Phase C shed north of Rudd Investments OU-1- B & C Figure 2, Area 305/370 9.3 pCi/g/ 8.0 Underneath B & Metals D1/D2/Phase C pCi/g C building building OU-1- B & C Figure 2, Area 18 10.0 pCi/g Beneath footer Metals E/Phase C in B & C metals building OU-1- B & C Figure 2, Area 119 8.8 pCi/g Beneath the Metals F/Phase C hallway at the building north end of B & C metals OU-1- Figure 2, Area 462 16.4 pCi/g East side of the Materials G/Phase C Materials Handling Handling Warehouse

172

Materials Left in Place as Averaged Areas-OU22

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-2- Jerome Area AA 120 9.6 pCi/g Beneath the floor Park slab of the north Maintenance shop building Yard OU-2- Jerome Area AB 70 8.9 pCi/g Around a Park telephone line Maintenance inside the east Yard property boundary OU-2- Jerome Area AD 75 16.3 pCi/g Around a Park telephone line Maintenance inside the east Yard property boundary OU-2-Jenkins Area DT 210 14.2 pCi/g Northeast corner building of the Jenkins building OU-2- Staab Area ED 470 13.5 pCi/g East side of the building Staab building OU-2 – Air Area EE 187 8.8 pCi/g North side of the Conditioning Air Conditioning, Property Inc., property OU-2- G & K Area EF 408 12.5 pCi/g North side of the G Services Property and K Services property

Materials Left in Place as Averaged Areas-OU-33

Site Location Figure/Area Square Feet Averaged Comments ID/Phase Concentration OU-3 Area A/Area B 25/24 5.0 pCi/g East of South Jason, at the base of mature trees OU-3 Area C 105 10.9 pCi/g North of Kwan Sang building- along underground utility lines beneath West Louisiana Ave. OU-3 Area D 506 13.8 pCi/g North wall of the Harbert Castings building- along foundation OU-3 Area E 509 10.3 pCi/g Alley of the Creative Illumination building

173

Materials Left in Place as Averaged Areas-OU-4, -54

Materials Left in Place as Averaged Areas OU-65

Site Location Figure/Area ID Square Feet Averaged Comments Concentration OU-6 Area A 170 9.5pCi/g Beneath 15th Street near the CSRR tracks OU-6 Area B 360 14.4pCi/g Beneath Confluence Park jogging trail near the CSRR tracks OU-6 Area D 595 14.1pCi/g North side of the Environmental Materials building OU-6 Area E 192 10.3pCi/g North side of the Environmental Materials building OU-6 Area F 369 10.8pCi/g West side of the storage yard at the Environmental Materials building OU-6 Area G 10 7.3pCi/g West side of the storage yard at the Environmental Materials building OU-6 Area H 5 8.5pCi/g West side of the Environmental Materials building OU-6 Area I 346 12.4pCi/g Beneath the railroad tracks west of the 174 Environmental Materials building OU-6 Area J 17 6.8pCi/g West side of the Environmental Materials building OU-6 Area K 10 7.8pCi/g South side of the Environmental Materials building

Materials Left in Place as Averaged Areas OU-9A6

Site Location Figure/Area ID Square Feet Averaged Comments Concentration OU-9A Area A 78 5.7 pCi/g Beneath the foundation footers of the IHOP building OU-9A Area B 4 5.7 pCi/g Beneath the foundation footers of the IHOP building OU-9A Area C 19 5.7 pCi/g Beneath the foundation footers of the IHOP building

Materials Left in Place as Averaged Areas: OU-107

1 RUST Geotech, Inc. August 1992. 2 RUST Geotech Inc. July 1994 3 RUST Geotech Inc. April 1994 4 RUST Geotech Inc. July 1994. 5 U.S. Environmental Protection Agency. September 25, 2006. Superfund Final Closeout Report: Denver Radium. 6 RUST Geotech Inc. June 1994 7 RUST Geotech Inc. March 1992. 175

Appendix 3 Maps of Radium Wast Left in Place

176

177

178 179 180 181 182 183

184

185

Appendix 4 Operable Unit Land Use Maps

186

Operable Unit 1 and 2 Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

187

Operable Unit 3 Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

188

Operable Unit 4, 5, 9B Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

189

Operable Unit 6 (Environmental Services) Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

190

Operable Unit 6A Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

191

Operable Unit 6C Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

192

Operable Unit 6D Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

193

Operable Unit 6E Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

194

Operable Unit 8 Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

195

Operable Unit 9A Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

196

Operable Unit 10 Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

197

Operable Unit 11 Land Use

Government Owned

Denver County Owned

Other Exempt

Vacant

Single Family Residential

Multi-Family Residential

Condominium

Commercial

Industrial

198

Appendix 5 Operable Unit Parcel Maps

199

Operable Unit 1 Parcel Outlines

200

Operable Unit 2 Parcel Outlines

201

Operable Unit 3 Parcel Outlines

202

Operable Unit 4, 5, 9B Parcel Outlines

203

Operable Unit 6A Parcel Outlines

204

Operable Unit 6C Parcel Outlines

205

Operable Unit 6D Parcel Outlines

206

Operable Unit 6E (Ruby Hill Park) Parcel Outlines

207

Operable Unit 6 Environmental Services Parcels

208

Operable Unit 8 Parcel Outlines

209

Operable Unit 9A Parcel Outlines

210

Operable Unit 10 Parcel Outlines

211

Operable Unit 11 Parcel Outlines

212

Appendix 6 Operable Unit 4, 5, & 9 Groundwater Monitoring Results

213

1995 Groundwater Monitoring Results: i The difference between metals contamination for each sampling event became smaller or remained within the confidence limits of two standard deviations. The statistical analyses indicated that the groundwater sampled during the April 1995 event is characteristic of groundwater qualities analyzed in past events.

1996 Groundwater Monitoring Results: ii

Metals Results: Cadmium: All monitoring well samples except the monitoring well approximately 400 feet east of the South Platte River Centerline (concentration of 170µg/l) had cadmium concentrations which were less than the associated EPA Drinking Water Standards and Health Advisories Maximum Contaminant Levels (MCL) and CDWS of 5µg/l. Previous data, seems to indicate the cadmium plume originated at the site and extends to the west/northwest toward the South Platte River.

Iron: Two well samples exceeded EPA’s Secondary Drinking Water Regulations for iron of 300µg/l (MW-11 and RW96-18 were 470 and 2,800µg/l, respectively)

Manganese: Eight of ten well samples exceeded the Secondary Drinking Water Regulations for manganese of 50µg/l. Concentrations exceeding MCL ranged from 100 to 4000µg/l.

Zinc: One well sample exceeded the Secondary Drinking Water Regulation for zinc (RW96-18, 16,000µg/l) of 5,000µg/l. The remaining concentrations ranged from 10 to 620µg/l.

Radiochemistry Results: Radium 226: Concentrations measured in the 1996 samples were lower than 1995, and no samples exceeded the Colorado Primary Drinking Water Regulations of 5pCi/l or the MCL of 20pCi/l.

Gross Alpha: Concentrations were less than the 1995 concentrations at every location except MW-14, RW92-20, and RW89-11.

Gross Beta: Concentrations were similar to the 1995 concentrations

Thorium: No substantial changes were observed when comparing the 1995 and 1996

Natural Uranium: Three well sample concentrations exceeded the MCL of 20µg/l. RW89-15, RW89- 14, and RW96-17 concentrations were 23.3, 27.0, and 25.9µg/l, respectively.

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1998 Groundwater Monitoring Results: iii

Metals Results: Cadmium: Total cadmium analytical results for six of the groundwater wells exceeded the associated EPA Drinking Water Standards and Health Advisories MCL and Colorado Primary Drinking Water Regulations of 0.005mg/l (ppm) with detection levels ranging from 0.00593 to 0.229 mg/l (ppm). Cadmium was not detected above the instrument detection limit in the two South Platte River surface water samples.

Iron: Detected at levels above the secondary water quality standard in all groundwater and surface water samples in the total iron fraction and in the dissolved fraction in one groundwater sample (MW-11). Detections ranged from 0.579 mg/l (ppm) to 18.0 mg/l (ppm).

Manganese: Total manganese was detected in all of the groundwater and surface water samples at concentrations above the secondary water quality standard ranging from 0.495mg/l (ppm) to 8.34mg/l (ppm) with the higher concentrations in groundwater clustered on the north side of the well field. Total manganese was detected in the surface water samples from the South Platte River at levels above the secondary water quality standards, but only slightly higher than background detection.

Dissolved manganese was detected in nine of the ten groundwater wells at levels above the secondary drinking water standard ranging from 0.126 mg/l (ppm) to 4.08 mg/l (ppm). Dissolved manganese was detected in surface water samples from the South Platte River, but at levels below the secondary drinking water standards.

Selenium: Detected above the detection limit in one sample (RW92-19 at 0.0144 mg/l (ppm)).

Zinc: Detected at levels above the secondary water quality standard in three groundwater wells (RW96- 18, RW89-14, and RW92-20) all located on the northwest side of the well field.

Radiochemistry Results: Total Radium: Five of the groundwater monitoring well samples exceeded the Colorado Drinking Water Quality Standards (RW89-15, MW-14, RW96-18, RW89-14, and RW92-19), but neither surface water sample exceeded the standard for total radium.

Thallium 208: Detected in three samples (RW89-15, RW96-17, and the upstream sample on the South Platte River) ranging from 12.2 to 25.9 pCi/L.

Gross Alpha: Exceeded the MCL and drinking water standard at five of the groundwater wells (MW-14, RW89-14, RW92-20, RW96-17, and RW89-12) ranging from 15.3 pCi/L to 79.5 pCi/L.

Gross Beta: Did not exceed MCL. 215

Total Thorium: Did not exceed MCL

Total Uranium: The three highest readings from groundwater wells (RW89-15, RW89-14, and RW96- 17) were the three groundwater wells that exceeded the total uranium MCL in the November 1996 sampling report.

January 2000 Groundwater Monitoring Results:iv

Metals Results: Cadmium: Dissolved cadmium was detected in the dissolved faction at levels that exceeded the State of Colorado Surface Water and Groundwater standard (0.005mg/l) in RW89-15(0.159mg/l), RW96-18 (0.058mg/l), and RW92-20 (0.005mg/l). Cadmium was not detected above the instrumental detection limit in the two South Platte River samples.

Iron: Detected in two wells (MW-14 at 0.35mg/l) and (MW-1 at 3.36 mg/l) exceeding the State of Colorado Surface Water Standard (0.3mg/l). Iron was not detected above the State of Colorado Surface Water Standard in the two South Platte River Samples.

Manganese: Dissolved manganese was detected in eight of the nine groundwater wells at levels above the State Drinking Water Standard ranging from 0.465 mg/l to 2.94 mg/l and included the background well as exceeding the State Drinking Water Standard. Dissolved manganese exceeded the State Drinking Water Standard in both the up-gradient and down-gradient surface water samples collected from the South Platte River.

Zinc: Detected in two wells (RW92-20 at 23.6 mg/l) and (RW96-18 at 10.5 mg/l) that exceeded the State of Colorado Surface Water Standard (5.0 mg/l). Zinc was not detected above State of Colorado Surface Water Standard in the two South Platte River surface water samples.

Radiochemistry Results: Total Radium: Five of the groundwater monitoring well samples exceeded Colorado Drinking Water Standards (RW92-20, MW-14, RW96-18, RW89-14, and RW92019). Neither surface water samples exceeded the standard for total radium.

Gross Alpha: Eight of the groundwater wells including the up-gradient groundwater well used to establish background levels exceeded the State Drinking Water Standard (MW-14, RW89- 15, RW92-20, RW96-17, RW89-12, RW92-19, RW96-18, and RW89-15) with values ranging from 42 9.3pCi/L to 160 25pCi/L.

Gross Beta: Six groundwater samples exceeded the 50pCi/L level (RW92-19, RW96-17, RW92-20, RW89-14, RW96-18, and MW-14).

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The 2000 results concluded that background surface and groundwater concentrations compared to down gradient surface and groundwater concentrations indicate that contamination from the Denver Radium OU-9B ROBCO site is not reaching the South Platte River in detrimental concentrations.

November/December 2001 Groundwater Monitoring Results:v

Metals Results: Cadmium: Detected in the dissolved fraction at levels that exceeded both the state surface water and groundwater standards (0.005mg/l) in well RW92-20 (0.2mg/l). Cadmium was not detected above the instrument detection limit in the two South Platte River surface water samples.

Iron: Detected in one well (MW-14 at 0.99 mg/l) that exceeded the State Groundwater Standard (0.3) mg/l). Iron was not detected above state surface water standard (0.3 mg/l) in the two South Platte River surface water samples.

Manganese: Dissolved manganese was detected in four of the six groundwater wells at levels above state standard ranging from 0.087 mg/l to 2.7 mg/l. Dissolved manganese exceeded the state standard in both the up-gradient and down-gradient surface water samples collected from the South Platte River.

Zinc: Detected in one well (RW92-20 at 27mg/l) that exceeded the state standard (5.0mg/l). Zinc was not detected above state standard in the two South Platte River surface water samples.

Radiochemistry Results: Total Radium: Exceeded the standard in monitoring well MW-14 and RW89-14. Neither surface water sample exceeded the standard for total radium.

Gross Alpha: Exceeded the standard in all of the groundwater samples collected including the up- gradient groundwater well used to establish background values with values ranging from 30 5.1pCi/l to 90 15 pCi/l and represent a general decline from the previous round of sampling collected in January 2000. The backgroundwater well exhibited concentrations exceeding the standard for Gross Alpha. The values in the South Platte River appear to have been relatively equal during the January 2000 sampling.

Gross Beta: One groundwater well exceeded the 50 pCi/l level (MW-14). Neither surface water sample exceeded the standard. Concentrations have improved since the January 2000 samples.

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Total Uranium: One well exceeded the equivalent of the federal MCL was well RW89-15 with 35.9 3.6 pCi/l.

The 2001 results concluded that up-gradient surface and groundwater concentrations compared to down- gradient surface and groundwater concentrations indicate that contamination from the OU-9B ROBCO site is not reaching the South Platte River in detrimental concentrations. The overall analytical trend demonstrated in all wells sampled was lower overall concentrations compared to the two previous sampling events. Exceptions were wells, MW-14 and RW92-20. MW-14, located down-gradient on the South Platte River, had slightly elevated levels of iron, total radium, gross alpha, and gross beta compared to previous sampling years. RW92-20 had slightly higher inorganic contamination while radiological contamination was lower.

July 2003 Groundwater Monitoring Results:vi

Metals Results: Cadmium: Dissolved cadmium was detected at levels that exceeded State Drinking Water MCL for groundwater of 5 µg/l in well RW92-20 (131 µg/l) and in well RW89-15 (5.7 µg/l). Cadmium was not detected above the instrument detection limit in the two South Platte River surface water samples. The concentration of cadmium in well RW92-20 is lower than what was observed during the last two sample rounds. The concentration of cadmium in well RW89-14 was slightly higher than during the last two sample rounds.

Manganese: Dissolved manganese was detected in five of the six groundwater wells at levels above the State Drinking Water MCL for groundwater with values ranging from 87.3 µg/l to 1,860 µg/l. Overall, manganese concentrations in all wells have dropped during the last two rounds of sample collections.

Zinc: Dissolved zinc was detected in one well (RW92-20 at 12,100 µg/l) exceeding the State Drinking Water MCL for groundwater of 5,000 µg/l. Zinc was not detected above state standard in the two South Platte River surface water samples. The zinc concentration in this well dropped by approximately 50 percent since the last monitoring round.

Total Uranium: Three of the six wells sampled contained uranium levels that were greater than the State Drinking Water MCL’s for groundwater with values ranging from 37µg/l to 60.3 µg/l.

Radiochemistry Results Total Radium: Monitoring well RW89-14 was the only groundwater sample to have exceeded the standard for total radium. Neither surface water sample exceeded the standard for total radium.

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Gross Alpha: Gross alpha readings exceeded the standard in four of the six groundwater samples collected including the up-gradient background sample with values ranging from 15.9 7.7pCi/L to 21.8 8.4pCi/L. This demonstrated a significant decline from the previous two rounds of sample collection.

Gross Beta: There were no exceedences for gross beta during this sample collection round.

The 2003 results concluded that up-gradient surface and groundwater concentrations compared to down- gradient surface and groundwater concentrations indicate that contamination from the Denver Radium OU-9B ROBCO site is not reaching the South Platte River in detrimental concentrations. The overall analytical trend for both inorganic and radiological analysis was lower overall concentrations compared to the previous two sample events. Exceptions were wells, RW89-14 and RW89-15, which exhibited slightly increased concentrations of inorganic analytes, and decreased concentrations for radiological parameters in comparison to the past two sample rounds.

It was recommended that continued monitoring should occur bi-annually for six years, and at that point, sample collection frequency should be re-evaluated. The 2006 CDPHE groundwater report showed continued attenuation of metals concentrations in groundwater, and that contamination is not reaching the South Platte River in detrimental conditions. The 2008 Five-Year Review recommended that based on groundwater trends, groundwater monitoring frequency be reduced to biennial until the time of the next Five-Year Review when monitoring frequency may be reassessed.vii As of May 2012, further monitoring was postponed until the Colorado Department of Transportation has completed the improvements along Interstate-25 adjacent to the site.viii

i ERM-Rocky Mountain, Inc. June 9, 1995. Robinson Brick Company Groundwater Monitoring Report. ii Sverdrup Corporation. November 1996. Monitoring Well Decommissioning, Installation, and Sampling Report of Perimeter Wells at the Denver Radium Superfund Site Operable Unit No. 9. iii URS Operating Services, Inc. July 6, 1998. Analytical Results Report for Denver Radium OU9 (ROBCO) Denver, Colorado Revision 1. iv Colorado Department of Public Health and Environment. November 6, 2000. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO. v Colorado Department of Public Health and Environment. March 7, 2002. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO. vi Colorado Department of Public Health and Environment Hazardous Materials and Waste Management Division. November 13, 2003. Annual Monitoring Report ROBCO Denver Radium OU-9, Denver, CO. vii Colorado Department of Public Health and Environment. September 30, 2008. viii U.S. Environmental Protection Agency. May 2012. Update to the Five-Year Review, Issues and Recommendations Update. Denver Radium Superfund Site. 219

Appendix 7 Regulatory Limits List

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Regulatory Agency Type of Contaminant Standard, Requirement, Comments Criteria, or Limitation FEDERAL Radium-226 Concentration 5 pCi/g above background1 Standards for cleanup of open lands U.S. EPA-40 CFR Part within 15 cm of the or buildings; 192, Subpart B-Standards surface measured over a concentration of radium-226 in land, 100-m2 area (soil) averaged over any area of 100 square meters. Point of compliance is at any contaminated area greater than 100 m2. However, during cleanup all contaminated areas would be remediated. 15 pCi/g above background2 within subsequent 15 cm layers measured over a 100-m2 area (soil) Gamma radiation 20 μR/hr above Relevant and appropriate to indoor background3 (soil) gamma radiation. Point of compliance is inside any site building. Thorium-230 Concentration 14pCi/g in the 0-6 inch (0-15cm) soil 40 pCi/g in any 6-inch thick layer layer between 6 inches deep and the maximum probable depth of a foundation, increasing exponentially to 500 pCi/g at a depth of 15 feet below the foundation, provided uncontaminated material overlies any contamination.

Regulatory Agency Type of Contaminant Standard, Requirement, Comments Criteria, or Limitation Radon Decay Product 0.02 WL annual average Relevant and appropriate to indoor Concentration 0.03 WL maximum radon. Point of

1 The background level used for the Denver Radium site is 2.0 pCi/g. 2 The background level used for the Denver Radium site is 2.0 pCi/g. 3 The background gamma radiation levels for Denver are approximately 15 μR/hr.

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compliance is inside any site building. Nuclear Regulatory Uranium-natural 5 pCi/m3, Unrestricted Point of compliance is any location Commission (NRC) Airborne area within site. 10 CFR Part 20 Concentrations 100 pCi/m3, Restricted area Thorium-230 3 pCi/m3, Unrestricted Point of compliance is any location Airborne area within site. Concentrations 30 pCi/m3, Restricted area Radium-226 Airborne 3 pCi/m3, Unrestricted Point of compliance is any location Concentrations area within site. 30 pCi/m3, Restricted area Gamma radiation 5 rem/yr, (5,000 Point of compliance is any location mrem/yr) Restricted area within site; 500 mrem/yr, site would be unrestricted for Unrestricted area remediation workers. STATE OF COLORADO Beta Particle and Photon Annual average less than or equal to If the gross beta particle activity CDPHE – 5 CCR 1003-1 Radioactivity 15pCi/L (groundwater) minus the naturally occurring 6.3 - Radionuclides potassium-40 beta particle activity at a sampling point has a running annual average (computed quarterly) less than or equal to 15 pCi/L (screening level), CDPHE may reduce the frequency of monitoring at that sampling point to once every 3 years. Systems must collect all samples required in section 6.3.3(a) during the reduced monitoring period.