Fourth Five-Year Review Report

Home , Allied Waste Industries, Republic Services

Five-Year Review Report

for Marshall Landfill Site

Boulder County, Colorado

August, 2011

PREPARED BY:

u.s. Environmental Protection Agency, Region 8 Denver, Colorado

Approved by: Date:

Assistant Regional Administrator Office of Ecosystems Protection and Remediation U.S. Environmental Protection Agency, Region 8

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Five-Year Review Report

Table of Contents

List of Acronyms ...... i Executive Summary ...... iii Five-Year Review Summary Form ...... v 1.0 Introduction ...... 1 2.0 Site Chronology ...... 2 3.0 Background ...... 3 3.1 Location and Setting...... 3 3.2 Site History ...... 4 4.0 Remedial Actions ...... 5 4.1 Remedy Selection ...... 6 4.2 Remedy Implementation ...... 7 4.3 Remedy Operation and Maintenance ...... 8 5.0 Progress since the Last Review...... 8 6.0. Five-Year Review Process ...... 9 6.1 Administrative Components ...... 9 6.1.1 Community Involvement ...... 10 6.1.2 Document Review ...... 10 6.1.3 Data Review ...... 10 6.1.4 Site Inspection ...... 12 6.1.5 Interested Party Interviews ...... 13 7.0 Technical Assessment ...... 14 7.1 Question A...... 14 7.2 Question B ...... 15 7.3 Question C ...... 16 7.4 Technical Assessment Summary ...... 16 8.0 Issues ...... 16 9.0 Recommendations and Follow-up Actions ...... 17 10.0 Protectiveness Statement ...... 18 11.0 Next Review...... 19

Tables Table 1 – Chronology of Site Events Table 2 – Actions Taken Since the Last Five-Year Review Table 3 – Issues Identified Table 4 – Recommendations and Follow-up Actions

Figures Figure 1 – Site Location Figure 2 – Water Quality Monitoring Locations

Appendix Appendix A – List of Documents Reviewed Appendix B – Site Surface and Ground Water Performance Standards Appendix C – Photo Log of Site Conditions

List of Acronyms

ARAR Applicable or Relevant and Appropriate Requirements BFI Browning-Ferris Industries CD Consent Decree CDPHE Colorado Department of Public Health and Environment CERCLA Comprehensive Environmental Response, Compensation and Liability Act CFR Code of Federal Regulations EPA United States Environmental Protection Agency ESD Explanation of Significant Difference IC Institutional Controls IR Information Repository LGAC Liquid-phase granular activated carbon MOM Monitoring, Operations and Maintenance NCP National Contingency Plan NPL National Priorities List O&M Operation and Maintenance OU Operable Unit PCE Perchloroethene POC Point of Compliance PRP Potentially Responsible Party RAO Remedial Action Objectives RI/FS Remedial Investigation/Feasibility Study ROD Record of Decision RPM Remedial Project Manager TCE Trichloroethene TDS Total Dissolved Solids VGAC Vapor-phase granular activated carbon VOC Volatile Organic Compounds

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Executive Summary

The United States Environmental Protection Agency (EPA) Region 8 has conducted the fourth five-year review of the remedial actions implemented at the Marshall Landfill Site (Site) in Boulder County, Colorado. The purpose of the five-year review is to determine whether the remedy at the Site is protective of human health and the environment. Because hazardous substances, pollutants or contaminants remain in place at the Site above levels that allow for unlimited use and unrestricted exposure, five-year reviews are required. The trigger action for this review is completion of the third five-year review in September 2006.

The Site is located in southeastern Boulder County, approximately one mile east of the town of Marshall and consists of two adjacent landfills, each comprising approximately 80 acres. Together the two landfills, totaling 160 acres, comprise one operable unit (OU1). The Marshall Landfill, in the northern portion of the Site, began operating in 1965, when the Richland Company, under contract with Boulder County, began a solid waste composting and disposal operation at the Site. In 1974, use of the Marshall Landfill was discontinued when Urban Waste Resources, along with Mesa Sand and Gravel, opened the Boulder Landfill to the immediate south, this southern portion of the landfill closed in January 1992. Landfill operations companies changed ownership multiple times by successive corporate acquisition. Republic Services, Inc is the current successor of landfill operations and is a responsible party in conjunction with the City of Boulder. Throughout the period of landfill operations, the land has been owned by The Cowdrey Corporation.

Several sources of contamination were identified during the Remedial Investigation/Feasibility Study (RI/FS), which was conducted in 1986. These included areas of saturated refuse, trenches used for waste disposal, small undefined areas where organic solvents were disposed, and two unlined leachate lagoons.

Onsite groundwater within the shallow alluvial aquifer was found to be contaminated with volatile organic compounds, heavy metals, chloride, nitrate and sulfate. Flow in the shallow aquifer is generally to the north and northwest and then east along Cowdrey Drainage. No contamination was identified in the deeper bedrock aquifer within the Laramie and Fox Hills Formations. No contamination was detected in surface waters leaving the Site during the RI. However, after completion of the RI, 1, 1 -dichlorethane was detected at 5 micrograms per liter (µg/L) in surface water from the Cowdrey Drainage.

The following Remedial Action Objectives (RAO) for the Marshall Landfill Site were developed in the Feasibility Study and Record of Decision (ROD; September 26, 1986): • Assure that all surface water discharge from the landfills does not adversely impact the current or planned future beneficial uses of the surface waters in this area or any other waters that it may contact; • Control the generation of contaminated groundwater at the Site;

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• Assure that any offsite contaminated groundwater originating at the Site does not adversely impact possible beneficial uses of groundwaters in this area or any other surface waters and groundwaters it may contact; and • Eliminate or control impacts resulting from leachate seepage in the landfills.

The Site remedy included a groundwater collection and treatment system, landfill improvements, and environmental monitoring programs. The remedy was considered operational in 1993. The collection and treatment system was placed on a stand-by mode in November 2004 after influent to the treatment system consistently met the discharge requirements for the main contaminants of concern.

While specific onsite and non-point of compliance monitoring wells have exhibited low level exceedances, the downgradient offsite point of compliance (EPA-18) has consistently met established groundwater criteria; indicating that offsite migration of contaminants of concern is not observed. Additionally, no exposure pathways have been identified for shallow groundwater in the vicinity of the Site. Information gathered to date indicates that the RAO are being met for the Site. The results of this fourth five-year review identified four issues that may potentially impact future remedy protectiveness. These issues are listed in the five-year review summary form.

The remedy at OU1 currently protects human health and the environment because no exposure pathways have been identified for contaminated shallow groundwater in the vicinity of the Site, the downgradient offsite point of compliance (EPA-18) has consistently met established groundwater criteria, the RAOs are being met, the Institutional Controls (IC) are in place, and the remedy is intact. However, in order for the remedy to be protective in the long-term, the following actions need to be taken to ensure long-term protectiveness: update the maintenance plan to specify maintenance required to repair animal damage to the landfill cover and update the water quality monitoring plan to delineate the presence of and monitor for 1,4-dioxane. Additionally, monitoring of the surface and ground water, as well as land and water usage in the vicinity, will continue in order to determine if changes in remedy protectiveness occur in the future.

The Site will continue to be evaluated through EPA’s five-year review process to ensure potential changes in protectiveness are detected and mitigated. The next five-year review will be completed by August 2016.

Five-Year Review Summary Form

SITE IDENTIFICATION Site name (from CERCLIS): Marshall Landfill Site EPA ID (from CERCLIS): COD980499255 Region: 8 State: CO City/County: Boulder County SITE STATUS

NPL status: � Final Deleted Other (specify) Remediation status (choose all that apply): Under Construction Operating � Complete Construction completion date: May 1993 Multiple OUs?* YES � NO

Has site been put into reuse? YES � NO REVIEW STATUS

Lead agency: � EPA State Tribe Other Federal Agency ______Author name: Joy Jenkins Author title: Remedial Project Manager Author affiliation: U.S. EPA Region 8 Review period:** 10 /15 /2010 to 08 /2011 Date(s) of site inspection: 03 /03 /2011 Type of review: Post-SARA � Pre-SARA NPL-Removal only Non-NPL Remedial Action Site NPL State/Tribe-lead Regional Discretion

Review number: 1 (first) 2 (second) 3 (third) � Other (specify): 4 (fourth) Triggering action: Actual RA Onsite Construction at OU #____ Actual RA Start at OU#____ Construction Completion � Previous Five-Year Review Report Other (specify) Triggering action date (from CERCLIS): 9 / 29 / 2006 Due date (five years after triggering action date): 9 / 29 / 2011

Five-Year Review Summary Form, cont’d.

Issues:

Affects Affects Future Issue Current Issue Protectiveness # Protectiveness (Y/N) (Y/N) 1 Surface Water Monitoring Locations typically dry during N N annual sampling events. 2 Monitoring, Operations and Maintenance plan does not N Y address required repairs for damage due to animal activity. 3 The water quality monitoring plan requires updating to N N optimize remedy efforts 4 1,4 dioxane was measured onsite above Colorado N Y groundwater standards.

Recommendations and Follow-up Actions:

Anticipated Recommendations and Party Oversight Issue # Issue Date of Follow-up Actions Responsible Agency Completion 1 Surface Water Collect, at minimum, one Republic EPA June 2015 Monitoring water sample when surface Services, Locations typically water is present in the Inc and City dry during annual Community Ditch and the of Boulder sampling events. Cowdrey drainage at both surface water POCs during the next five-year review period. 2 Monitoring, Update the Monitoring, Republic EPA December Operations and Operations and Services, 2012 Maintenance plan Maintenance plan to specify Inc and City does not address maintenance that will be of Boulder required repairs for performed to repair animal damage due to damage to the landfill cover. animal activity. 3 The water quality Optimize the water quality Republic EPA/ December monitoring plan monitoring plan to Services, CDPHE 2012 requires updating effectively use resources for Inc and City to optimize remedy protectiveness monitoring. of Boulder efforts Include clarification of performance standards. 4 1,4 dioxane was Update water quality Republic EPA/ December measured onsite monitoring plan to delineate Services, CDPHE 2012 above Colorado the extent of the 1,4 dioxane Inc and City groundwater presence and to monitor for of Boulder standards. potential offsite migration.

Five-Year Review Summary Form, cont’d.

Protectiveness Statement:

The remedy at OU1 currently protects human health and the environment because no exposure pathways have been identified for contaminated shallow groundwater in the vicinity of the Site, the downgradient offsite point of compliance (EPA-18) has consistently met established groundwater criteria, the RAOs are being met, the ICs are in place, and the remedy is intact. However, in order for the remedy to be protective in the long-term, the following actions need to be taken to ensure long-term protectiveness: update the maintenance plan to specify maintenance required to repair animal damage to the landfill cover and update the water quality monitoring plan to delineate the presence of and monitor for 1,4-dioxane. Additionally, monitoring of the surface and ground water, as well as land and water usage in the vicinity, will continue in order to determine if changes in remedy protectiveness occur in the future.

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Five-Year Review Report

1.0 Introduction

The United States Environmental Protection Agency (EPA) Region 8 has conducted a fourth five-year review of remedial actions implemented at the Marshall Landfill Site (Site) in Boulder County, Colorado. The Site consists of two parcels, the northern 80-acre Marshall Landfill and the southern 80-acre Boulder Landfill. Both landfill operations are inactive and are considered one operable unit (OU). The Site Location map is presented in Figure 1.

The purpose of five-year reviews is to determine whether the remedy at a site is protective of human health and the environment. The methods, findings, and conclusions of reviews are documented in Five-Year Review reports. In addition, Five-Year Review reports identify issues found during the review, if any, and recommendations to address them.

The EPA has prepared this five-year review pursuant to the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) and the National Pollution Contingency Plan (NCP). CERCLA § 121 states1:

If the President selects a remedial action that results in any hazardous substances, pollutants, or contaminants remaining at the site, the President shall review such remedial action no less often than each five years after the initiation of such remedial action to assure that human health and the environment are being protected by the remedial action being implemented. In addition, if upon such review it is the judgment of the President that action is appropriate at such site in accordance with section [104] or [106], the President shall take or require such action. The President shall report to the Congress a list of facilities for which such review is required, the results of all such reviews, and any actions taken as a result of such reviews.

The agency interpreted this requirement further in the National Contingency Plan (NCP); 40 CFR §300.430(f)(4)(ii) states:

If a remedial action is selected that results in hazardous substances, pollutants, or contaminants remaining at the site above levels that allow for unlimited use and unrestricted exposure, the lead agency shall review such action no less often than every five years after the initiation of the selected remedial action.

EPA Region 8 has conducted a five-year review of the remedial action implemented at the Site. This review was conducted from October, 2010 through June, 2011. This report documents the results of the review.

1 The record of decision (ROD) for this Site was finalized before the Superfund Amendments and Reauthorization Act (SARA) amended CERCLA on October 17, 1986; therefore, the five-year review is required by policy rather than statute.

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This is the fourth five-year review for the Site. The triggering action for this review is the date of the previous five-year review report completion on September 29, 2006. Because hazardous substances, pollutants or contaminants remain at the Site above levels that allow for unlimited use and unrestricted exposure, another five-year review is required.

2.0 Site Chronology

Table 1 presents the chronology of significant events at the Site.

Table 1: Chronology of Site Events Event Date Solid waste management operations began at the Marshall Landfill parcel of the Site under 1965 management of Richland Company Operations purchased by Salvage, Inc., later renamed Urban Waste Resources (UWR) 1969 UWR operated the solid waste landfill 1970-1974 UWR discontinued use of the Marshall Landfill parcel of the Site and, with Mesa Sand and 1974 Gravel, opened the Boulder Landfill parcel to the south Landfill, Inc., purchased the operation 1975 EPA proposes Marshall/Boulder Landfill for the NPL July 1982 Marshall Landfill included on NPL September 1983 EPA, Landfill, Inc., Boulder County, Colorado Department of Health, City of Louisville and 1983 Farmers Reservoir and Irrigation Co. enter into a Cooperative Agreement. EPA issued order to Landfill, Inc. requiring them to install Community Ditch pipeline by April 1983 1984 to protect the quality of drinking water conveyed across the Site Pipeline Installation 1984 Remedial Investigation/Feasibility Study completed by Landfill, Inc 1986 Record of Decision (ROD) issued by EPA September 1986 Consent Decree finalized and accepted by all parties (EPA, City of Boulder, Landfill, Inc. and March 1989 landowners) Additional site investigations performed 1989-1990 Boulder Landfill parcel closes January 1992 Final remedial design submittal approved by EPA May 1992 Construction of treatment plant and collection system initiated August 1992 First Explanation of Significant Differences to the ROD issued by EPA November 1992 Remedial action construction complete with EPA approval of Final Remedial Measures October 1993 Implementation Report Final O&M Plan approved by EPA 1993 First Five Year Review Completed November 1995 Corrective measures completed to address seepage identified in first five-year review 1996

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Table 1 presents the chronology of significant events at the Site.

Table 1: Chronology of Site Events Event Date Final Revised Off-Site Water Quality Monitoring Plan approved by EPA 1997 Second five-year review completed September 2001 Second Explanation of Significant Differences to ROD issued by EPA September 2003 Groundwater collection and treatment system terminated November 2004 Water quality monitoring plan implemented (quarterly for 12 quarters) November 2004 Third five year review completed September 2006 Water quality monitoring plan adjusted from quarterly to annual sampling November 2008

3.0 Background

The following sections describe Site location, geologic setting and history.

3.1 Location and Setting

The Site is located in southeastern Boulder County, approximately one mile east of the town of Marshall. The Site is south of Colorado Highway 170 and is bounded on the east by South 66th Street. Marshall Lake is located approximately 2,000 feet to the west. Approximately two miles east is the town of Superior. The cities of Boulder and Louisville are three miles to the northwest and northeast, respectively. The area within a one-mile radius of the Site is sparsely populated.

The land surrounding the Site is used primarily for livestock grazing. The other adjacent land uses are as follows: (1) storage facility for the National Center for Atmospheric Research on the east side of South 66th St.; (2) an irrigation and municipal drinking water reservoir, Marshall Lake, to the west of the Site; (3) a natural gas compressor station operated by Excel Energy; (4) a recreational trail near the northern border of the Site installed recently by the Boulder County Open Space; (5) approximately 15 houses are clustered to the Northeast of the Site approximately a mile away and some additional houses and ranches are dispersed in the general area.

The Cowdrey Drainage runs through the northern portion of the Site, which conveys surface water from Cowdrey Reservoir No. 2 approximately 3 miles to South Boulder Creek, see Figure 2. At some times in the past, Cowdrey Drainage flow was diverted to Davidson Ditch where it was used for irrigation. However, for most of the year the Cowdrey Drainage is dry. The Community Ditch also crosses the northern portion of the Site and flows in the same direction as the Cowdrey drainage. The community ditch carries water from Marshall Lake east to the City of Louisville, where it is used as drinking water and then farther east, where the flow is used as irrigation water.

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As part of the response actions (described in Section IV), in 1984 a pipeline was installed to replace the open ditch portion of the Community Ditch that ran through the northern portion of the Site. Additionally, two small lagoons, constructed by Boulder County in an attempt to collect and contain landfill leachate, were previously located within the Marshall Landfill Site.

The Site lies along the north-facing side of Lake Mesa, a geologic feature which is a broad, upland pediment surface, consisting of a gravel-capped bedrock erosional surface along the crest, a series of colluvial and terrace deposits along the flanks, and colluvial and weathered soil along Cowdrey Drainage. Refuse in the Marshall Landfill was placed along the bedrock slope north of Cowdrey Drainage, down into Cowdrey Drainage and up along the flank of the Lake Mesa geologic feature.

The uppermost hydrostratigraphic unit is an unconfined aquifer consisting of: (1) alluvial sands, gravels and clays mantling the top and flank of Lake Mesa; (2) colluvial material along the base of Lake Mesa; (3) weathered bedrock and alluvium along Cowdrey Drainage; and (4) refuse placed in the Marshall/Boulder Landfill. Underlying the Site, groundwater flow in the shallow alluvial aquifer is generally to the north.

Deeper hydrostratigraphic units are bedrock aquifers within the Laramie and Fox Hills Formations. These units underlie the shallow alluvial and colluvial deposits that make up the shallow aquifer. The regional groundwater flow direction in the bedrock aquifers is to the east.

The land and resource use in the general vicinity of the Site is anticipated to remain as a rural designation with continued livestock grazing, and very low density housing. New housing in the immediate vicinity is not anticipated. Future use of the shallow alluvial groundwater is not anticipated.

3.2 Site History

The Site consists of two adjacent landfills, each comprising approximately 80 acres. The Marshall Landfill, located to the north, began operating in 1965, when the Richland Company, under contract with Boulder County, began a solid waste composting and disposal operation at the Site. Although the contract specified composting operations, landfilling comprised the majority (80%) of waste handling activities. In 1969, the operation was sold to Salvage, Inc., which was later acquired by a group of local investors and renamed Urban Waste Resources. Between 1969 and 1974, the Marshall Landfill accepted municipal waste, unstabilized sewage sludge and many unknown, potentially hazardous wastes.

In 1974, use of the Marshall Landfill was discontinued when Urban Waste Resources, along with Mesa Sand and Gravel, opened the Boulder Landfill to the immediate south. Landfill, Inc., a wholly owned subsidiary of Browning-Ferris Industries (BFI), purchased the landfill operation in 1975. The Boulder Landfill closed in January 1992. BFI was then purchased by Allied Waste Industries which was subsequently purchased by Republic Services, Inc. Throughout the period of landfill operations, the land has been owned by the Cowdrey Corporation which leased the land to the landfill operators.

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In September 1983, the Marshall/Boulder Landfill was listed on the National Priorities List (NPL) due to the release of contamination to irrigation and drinking water. A major concern was the contamination of water flowing in Community Ditch because it serves as a source of drinking water for the City of Louisville. In response to this concern, a 60- inch pressurized pipeline was installed to convey the water across the inactive landfill.

Several sources of contamination were identified during the Remedial Investigation/Feasibility Study (RI/FS), which was conducted in 1986. These included: • Areas of saturated refuse within the northern portion of the Boulder Landfill and throughout the Marshall Landfill; • Trenches used for waste disposal between 1972 and 1974 at the Marshall Landfill; • Small, undefined areas within the Marshall Landfill where industrial wastes, primarily organic solvents, were disposed along with solid wastes; and • Two unlined leachate lagoons in the southern portion of the Marshall Landfill.

No contamination was detected in surface waters leaving the Site via Cowdrey Drainage and Community Ditch during the RI. However, after completion of the RI, 1,1-dichloroethane was detected at 5 micrograms per liter (µg/L) in surface water from the Cowdrey Drainage. Onsite groundwater within the shallow alluvial aquifer was found to be contaminated, as characterized by elevated levels of: • Volatile organic compounds (VOCs) such as benzene, trichloroethene (TCE) and perchloroethene (PCE); • Heavy metals such as barium, iron, manganese and zinc; and • Major ions, such as chloride, nitrate and sulfate.

No contamination was identified in the deeper bedrock aquifer.

Based on the findings of the RI/FS, EPA selected a preferred remedy, which was described in the 1986 ROD.

Of additional interest in the area, Superior Paper Products was located near the northeastern border of the Site. Chemicals were used and stored at this location. The Superior Paper Products location was vacated and stored chemicals and debris were cleaned up in 1991. EPA conducted a preliminary investigation in 1992 and filed a ‘No Further Action’ decision for the Superior Paper Products site.

4.0 Remedial Actions

The following remedial action objectives (RAO) for the Site were included in the Feasibility Study and ROD (September 26, 1986):

• Assure that all surface water discharge from the landfills does not adversely impact the current or planned future beneficial uses of the surface waters in this area or any other waters that it may contact; • Control the generation of contaminated groundwater at the Site;

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4.1 Remedy Selection

The remedy described by the ROD involves collection of contaminated groundwater leaving the Site; treatment of the collected groundwater; environmental monitoring; and landfill cover and perimeter improvements.

The major components of the remedy selected by the ROD include:

• Elimination of offsite transport of contaminants emanating from the Site by constructing a drain or series of drains to capture shallow groundwater along the southern and eastern Site boundaries; • Treatment of collected contaminated groundwater in a facility consisting of equalization/sedimentation basins, an air stripper, and carbon adsorption of air stripper off-gas (vapor-phase granular activated carbon, or VGAC); • Implementation of an environmental monitoring program to verify the effectiveness of the remedial action and to assure protection of public health; • Completion of landfill improvements, including re-grading, revegetation, installation of perimeter ditches and fences and signage to minimize future environmental and public health impacts from the Site; • Drainage of existing leachate lagoons and transfer of the liquid to the treatment system; and • Redirection of the discharge of an existing french drain (installed to collect seepage during landfill operations) to the treatment facility.

A Consent Decree (CD) was entered into on March 29, 1989. The parties are EPA, Landfill, Inc. (now Republic Services, Inc), City of Boulder and the landowners. Section IV of the CD required the potentially responsible parties (PRPs), including Landfill Inc. and the City of Boulder, to design, construct, operate, maintain and monitor the performance of the remedial measures implemented at the Site. The Scope of Work included as Exhibit II of the CD detailed the procedures, tasks and schedule to be followed by the responsible parties in performing the selected remedial action. The remedial action required by the CD is the same as that described by the ROD and consists of the following tasks: Task I-Landfill Improvement; Task II-Groundwater Collection and Treatment; Task III-Monitoring. The CD also established the methods by which remediation standards for water quality would be developed for the Site.

Additional investigations were carried out in 1989 and 1990 in order to provide information needed to design the collection and treatment systems specified in the ROD and determine the remediation standards. In November 1992, based on the findings of these investigations, EPA issued an Explanation of Significant Differences (ESD) to the 1986 ROD remedy. The ESD included four significant modifications to the remedy as originally selected:

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• The groundwater collection system was changed to consist of a well array along most of the eastern Site boundary and a collection trench along part of the southern and eastern Site boundaries instead of the series of drains specified by the ROD; • Breakpoint chlorination/dechlorination was added to the treatment system to remove ammonia from collected groundwater prior to its discharge; • In addition to the air stripper and VGAC for off-gas treatment specified in the ROD, a liquid-phase carbon adsorption system (liquid-phase granular activated carbon, or LGAC) was added to remove VOCs directly from the water; and • The effluent limitation for chloride was changed from 280 mg/L to 320 mg/L, after the Colorado Water Quality Control Commission modified the numeric water quality stream standard for chloride to 320 mg/L.

When the ROD was issued, groundwater standards did not exist for several VOCs of concern at the Site. As such, the original Applicable or Relevant and Appropriate Requirements (ARARs) were no longer protective of human health and the environment. In addition, many of the Colorado surface water quality standards had also been updated since issuance of the ROD. In September 2003, EPA issued a second ESD to the 1986 ROD remedy which outlined updated performance standards for surface water and groundwater.

The 2003 ESD also identified Institutional Controls (ICs) that are necessary to ensure long-term protection of the engineered remedy and to prevent future release of contamination. ICs have been implemented and are active for the Site and contain two components. The first component is an informational device that identifies the property as a Superfund Site in the records of the Boulder County Planning Department. The device is an electronic map, which identifies the landfill boundary, and which will be referenced if any applications related development or other changes in land use are submitted to Boulder County. The second component is a local enforcement device. The device is a prohibition on the development of the Superfund Site and surrounding lands pursuant to the Rural Preservation Planning Area land use designation. This land use prohibition is enforceable by Boulder County and the surrounding municipalities including: the City of Boulder, the City of Louisville, and the Town of Superior through the Intergovernmental Agreement US 36 Interstate Corridor Comprehensive Development Plan effective June 20, 2000. Specifically, the agreement states that the municipalities “shall not grant a permit for development” for all areas within the Rural Preservation Planning Area including the Superfund Site.

4.2 Remedy Implementation

The remedy implemented is the remedial action selected in the 1986 ROD, as subsequently modified in the 1992 and 2003 ESDs. Collection and treatment of groundwater began in 1993. In 2004, groundwater collection and treatment were discontinued and these systems were placed in a stand-by mode because the influent concentrations of the contaminants of concern were lower than the discharge standards. In order to assess the impact of the discontinuation of treatment, EPA required 12-quarters of groundwater well monitoring after the plant ceased operation. After

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the 12-quarter monitoring period, results indicated that the monitoring frequency could be reduced to once annually. This annual sampling event occurs in November. This annual monitoring is ongoing and the plant is currently in a ‘mothballed’ status.

4.3 Remedy Operation and Maintenance

The PRPs are conducting long-term monitoring and maintenance activities in accordance with the Monitoring, Operations and Maintenance plan (MOM plan; ARCADIS, 2003) and modifications detailed in subsequent documents including: the Proposal to Terminate Active Remedial System Operation (ARCADIS, 2004), the Response Letter to the Request for Reduction in Sampling Frequency (EPA, 2009), and the Clarification of Action Levels and Re- Sampling Requirements (ARCADIS, 2005).

The primary activities associated with operations, maintenance and monitoring of the remedy since the discontinuance of treatment plant operations in 2004 include: • Maintenance of landfill improvements including inspection of cap and vegetation, repair of erosion, and maintenance of fences and signage; • Piezometric monitoring to evaluate changes in water table depth and flow direction; • Offsite and onsite surface water and groundwater monitoring for contaminants; and, • Maintenance of groundwater monitoring wells.

Monitoring results are reported to EPA according to the reporting requirements and schedules in the MOM plan as modified by the subsequent documents previously listed. Currently water quality monitoring and water table level measurements are performed annually in November.

Currently annual PRP Site monitoring, operations and maintenance costs average approximately $105,000 per year (based on years 2005 through 2009 data). These costs are shared between the PRPs.

5.0 Progress since the Last Review

In the third five-year review (2006) the remedy was determined to be protective of human health and the environment. However, some issues were identified that may have potentially affected protectiveness if not addressed. The issues and subsequent progress toward resolution are presented in Table 2.

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Table 2: Actions Taken Since the Last Five-Year Review Issues from Previous Recommendations/ Party Action Taken and Date of Review Follow-up Actions Responsible Outcome Action

- COMPLETED - Clarify which surface No distinction made The Cowdrey drainage water points of between upper and surface water point of compliance are in the EPA 12/06 lower Cowdrey compliance is in the upper and lower drainage lower Cowdrey drainage. Cowdrey drainage. - COMPLETED - Analytical methods have Detection limits been revised for reported for some Revise analytical ammonia, mercury and inorganics and metals EPA and City method or document silver. These revised are higher than of Boulder/ new performance analytical methods went 12/06 relevant surface water Republic standard in an ESD. Services into effect for the quality performance February 2007 and standards. subsequent sampling events. Frequent Continue monitoring in exceedances of accordance with the City of - COMPLETED - groundwater Proposal to Terminate Boulder/ An annual monitoring standards at 11/08 Active Remediation Republic plan is in place. monitoring location Services System Operation. EPA-14.

The actions taken have sufficiently addressed the issues identified in the third five-year review. In August 2007, EPA made a Site-Wide Ready for Anticipated Use (SWRAU) determination based on compliance with RAOs, institutional controls in place, and prevention of contaminant exposure.

6.0. Five-Year Review Process

This is the fourth five-year review of the Site. The following sections describe the Five-Year review process applied to the Marshall Landfill Site.

6.1 Administrative Components

The five-year review team was lead by Joy Jenkins, the EPA Remedial Project Manager, and included Fonda Apostolopoulos (CDPHE project manager), EPA technical support staff including Andrew Schmidt (hydrologist), and John Dalton (Community Involvement Coordinator).

The review was initiated on October 15, 2010 and included the following components: • Community Involvement; • Document Review; • Data Review;

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• Site Inspection; and • Interested Party Interviews.

The responsible parties were notified at the start of the five-year review process. The schedule for the review extended through June 2011.

6.1.1 Community Involvement

In March 2011, EPA visited the Boulder Public Library, (1001 Arapahoe Ave., Boulder, CO), where an information repository (IR) had previously been established. As a result of the visit, EPA’s Region 8 Records Center updated the IR for Marshall Landfill and provided it to the library. The IR contains the most relevant technical and informational documents in electronic format for viewing by the public and interested individuals. Additional records are maintained and are available for public review at the EPA Region 8 office records center (1595 Wynkoop, Denver, CO).

A notice that the five-year review was in progress was posted to EPA Region 8’s Marshall Landfill Site Website (http://www.epa.gov/region8/superfund/co/marshall/index.html) and placed in the Boulder Daily Camera (Boulder, Colorado) on March 31, 2011. The notice invited members of the public to submit their input regarding the review to EPA during the public comment period closing on May 2, 2011 and provided the contact information of the EPA remedial project manager, Joy Jenkins. No individuals contacted EPA as a result of the public notice.

Following completion of the five-year review, a notice will be posted to EPA Region 8’s Marshall Landfill Site website and placed in the Boulder Daily Camera announcing that the review has been completed and that copies of the report are available for the public to review at the EPA Superfund Records Center in Denver, CO and the Boulder Public Library in Boulder, CO.

6.1.2 Document Review

The documents reviewed in preparation of this five-year review report are listed in Appendix A.

6.1.3 Data Review

The remedy includes a monitoring program designed to track groundwater levels and to evaluate groundwater and surface water quality. The current monitoring program includes annual piezometric measurement to determine groundwater level and flow direction and water quality monitoring of seven specific groundwater wells and two surface water locations. In 2004, four point of compliance (POC) sampling locations were identified. These include the two offsite surface water locations (CDO and CDPO) and two POC groundwater well locations, one onsite (EPA-14) and one offsite (EPA-18). The PRPs are required by the 1989 Consent Decree to monitor groundwater east of South 66th Street and the southern portion of the Site that may have

Marshall Landfill Five-Year Review Report - 10

been impacted from activities not related to the landfill operation or PRP involvement (T7-3, T3 3, and T4-3). Water monitoring locations are presented in Figure 2. Water Quality performance standards are included in Appendix B.

A summary of these data and their interpretation for demonstrating remedy performance is provided below.

Water Quality Monitoring Results for VOCs Examination of the VOC data reveals that between August 2006 and May 2011 there were no exceedances of VOC concentrations at the Community Ditch monitoring location when samples were able to be collected. However, it should be noted that on nine of the 12 sampling dates since fall 2006 the monitoring location (CDPO) was dry. The Cowdrey Drainage monitoring location (CDO) was dry on all sampling dates within this review period; however, no VOC exceedances have ever been recorded at this location since monitoring began here in 1995. Benzene concentrations have exceeded the groundwater performance standards at the onsite POC (EPA-14). The average concentration over the review period was 7 ug/L Benzene, while the performance standard is 5 ug/L. The offsite POC (EPA-18) has consistently met the performance standards for VOC’s since monitoring at this location began in 1995, indicating no migration of VOC contamination to this offsite location.

Exceedances for VOCs have been observed at the groundwater wells east of South 66th Street during the review period. Two of which (T7-3 and T3-3) have shown statistically declining concentrations of the VOCs that have been detected since monitoring began. The third of these wells (T4-3) has exhibited similar concentrations for Tetrachloroethene (PCE; 5 year average 27 ug/L) and Trichloroethene (TCE; 5 year average 11 ug/L) and slightly increasing concentrations of 1,1-Dichloroethane (5 year average 11 ug/L) during the monitoring period. VOC exceedances have not been observed at the other two monitoring wells (NA-4 and T5-2) near the Site boundary.

The State of Colorado has established a groundwater standard for 1,4 dioxane at 6.1 ug/L, see Section 7.2 for additional information. In May of 2011, six of the seven ground water monitoring wells were screened for 1,4 dioxane2. This chemical was found above the Colorado standard at two onsite locations; EPA-14 (at 23 ug/L) and NA-4 (at 15 ug/L). No detections of 1,4 dioxane were identified at the other five monitoring well locations including the offsite point of compliance.

Additionally, a review of recent data provided to CDPHE’s Solid Waste and Materials Management Unit for the Boulder portion of the landfill as required by the State of Colorado, indicates that certain VOCs have been detected at the landfill boundary. A review of all available data indicates that offsite migration of VOCs has not been observed.

Water Quality Monitoring Results for Metals and other Inorganics No metal or other inorganic compound exceedances were observed in the three surface water samples that were collected during the review period except for a slightly elevated ammonia concentration recorded in 2007 at CDPO. Elevated levels of iron, ammonia, chloride and total

2 The sample bottle for T7-3 was damaged in transit and the sample could not be analyzed.

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dissolved solids (TDS) are observed at the onsite groundwater monitoring location (EPA-14). The offsite groundwater monitoring location (EPA-18) has consistently met all metals and inorganic performance standards. The three eastern monitoring wells and the two monitoring wells near the Site boundary have exhibited exceedances for chloride at one well, TDS at two wells, and nitrate at one well. No metals exceedances have been observed at the Site with the exception of iron exceedances that are consistently observed at the onsite groundwater monitoring location (EPA-14).

Arsenic exceedances have been reported in past monitoring reports; however, further investigation indicated that the analytical method used produced a positive bias for arsenic due to inorganic interference. The analytical method has subsequently been changed from EPA method 200.8 to a modified method that uses a collision cell technology (EPA method 200.8-CCT) to eliminate the positive interference.

Some chemicals included in the MOM plan for sample analysis have not been detected at the Site for the duration of monitoring. Chemicals could be identified that no longer require laboratory analysis in order to optimize monitoring efforts.

6.1.4 Site Inspection

On March 3, 2011 EPA conducted a five-year review Site inspection. Participants included EPA RPM Joy Jenkins, EPA community involvement coordinator John Dalton, CDPHE’s project manager Fonda Apostolopoulos, and representatives from City of Boulder, and Republic Services. The objectives of the inspection were to observe the condition of the RA landfill improvements and on-going maintenance, and to interview the responsible parties/operators to identify issues that may impact protectiveness. Interviews are summarized in Section 6.1.5.

Signage to deter trespassers and fencing were in good condition. The Boulder portion of the landfill is surrounded by an approximately 10 foot tall fence, while the Marshall portion of the landfill is bordered by an approximately three foot tall fence. Neither fence will eliminate the potential for trespassers; however, no trespass activity has been observed or reported at the Site. Signage indicating that the area is private property is spaced in frequent intervals on the Site fence line.

Very good vegetative cover over the capped area was observed and no soil erosion issues were identified. Additionally, no seepage of landfill impacted water was apparent within the Site boundary. Cover disturbance by prairie dogs was observed on parts of the northern half of the landfill (Marshall Landfill area) near the eastern side. The burrows were not active and appeared to have been abandoned shortly after they were dug. There does not appear to be a significant issue with prairie dog use; however, this situation will require monitoring and maintenance to repair cover disturbance by animals. Photographs from the Site inspection are included as a Photo Log in Appendix C.

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6.1.5 Interested Party Interviews

During the five-year review process, interviews were conducted with parties involved with the Site, including representatives of CDPHE, Community Ditch-Farmer’s Reservoir and Irrigation, City of Louisville-water treatment operations, and PRPs and contactors involved in Site activities. The purpose of the interviews was to document the perceived status of the Site and any perceived problems or successes related to the remedy already in place. The interviews were conducted during the Site inspection in March 2011 and later via phone.

Fonda Apostolopoulos: State Project Officer, CDPHE. Mr. Apostolopoulos believes the Site remains protective of human health and the environment. He reports no complaints, violations or other incidents requiring response. He believes the remedy in place is performing as designed.

Sidney E. Copeland: City of Louisville, Water Treatment Operations. Mr. Copeland indicated that the Community Ditch pipeline, located in the northern portion of the Site, is drained and inspected every three years. No problems with infiltration from the groundwater have been identified. Community Ditch water comprises a portion of Louisville drinking water source. The City has a regular drinking water monitoring program that includes analysis for VOCs and other potential contaminants. Results of Louisville’s water quality monitoring are posted on their website (http://www.louisvilleco.gov/SERVICES/PublicWorks/WaterTreatmentDivision/tabid/354/Defa ult.aspx). No landfill related concerns or problems have been observed.

John P. Akolt: Counsel to Farmer’s Reservoir and Irrigation Company (FRICO). Mr Akolt confirmed that water conveyed by the Community Ditch is delivered to the City of Louisville as well as agricultural customers. No Community Ditch water quality concerns or issues have been reported to FRICO with respect to the Marshall Landfill Superfund Site.

Floyd Bebler: City of Boulder, Wastewater. Mr. Bebler, conducts inspections of the Site and treatment plant twice yearly at minimum. He reports no complaints, violations or other incidents other than general maintenance requiring response from the City of Boulder. He looks to EPA and/or CDPHE to guide the PRPs through the National Priorities List (NPL) deletion process and establish beneficial use of the land.

Chris Douville: City of Boulder, Treatment Plant Coordinator. Mr. Douville conducts two formal visits and approximately two informal inspections of the treatment plant yearly. He reports no complaints, violations or other incidents other than general maintenance requiring response. Mr. Douville would like to see the now-inactive treatment plant dismantled to allow for better use of resources at the Site. He is interested in working with EPA to delete the Site from the NPL.

Melissa Green: Republic Services: She reports no difficulties in day-to-day operations at the Site and relies on the PRP agreement to implement Republic Services’ responsibilities. She is one of the local representatives for Republic Services.

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Victoria Warren: Director of Hydrogeology & Superfund, Republic Services. Ms. Warren reports no breech of institutional controls at Marshall Landfill and believes the remedy is working well. She believes EPA should investigate reuse possibilities.

Dana Sincox: Senior Geologist, Herst & Associates. Consultant for Republic Services and City of Boulder. Ms. Sincox coordinates water sampling activities every year in November, is responsible for data collection, analytical data review, and ensuring any required monitoring well maintenance is reported to the PRPs. She believes that the current remedy performance is effective in protecting human health. Ms. Sincox believes EPA should look into reuse projects for the property.

7.0 Technical Assessment

Three questions are answered in the five-year review process to evaluate Site conditions and determine issues that may impact protectiveness, recommendations for corrective action, and determination of remedy protectiveness of human health and the environment.

7.1 Question A

Is the remedy functioning as intended by the decision documents?

Yes, the remedy is functioning as intended. The technical assessment of the current state of the landfill improvements, surface and ground water monitoring results, and ICs are described below.

Landfill Improvements Ample vegetative cover has been established at the Site. Semi-annual inspections, as described in the MOM plan, are conducted by the City of Boulder to ensure erosion is detected and mitigated and that fences and signage are in good condition. Additionally, severe rain events trigger Site inspections to ensure sudden erosion events are detected and mitigated. The MOM plan describes actions required for identified erosion issues, and fence and signage damage.

Disruption of the cover soil by prairie dogs has been observed occasionally. While animal activity is not prevalent, the current MOM plan does not indicate whether or how soil or vegetative cover damage created by animals, such as prairie dogs, should be repaired nor does the MOM plan address any mitigation that may be required due to surfacing trash, such as previously discarded tires, that may occur at older landfills.

Compliance with Surface and Groundwater Performance Standards One of the remedial action objectives of the ROD is to ensure that surface drainage from the Site does not adversely impact beneficial uses of nearby surface waters. When surface water has been present for sampling, analysis demonstrates that water quality performance standards are generally maintained in Cowdrey Drainage and Community Ditch. However, these POCs have been dry during most of the sampling events in this review period. While the main downstream user of the Community Ditch water, City of Louisville, has not observed contamination issues

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associated with this surface water, surface water sampling at these POCs in the next review period are expected to increase confidence in the protectiveness determination.

Groundwater monitoring has identified exceedances of certain VOCs, inorganics including chloride, ammonia and TDS and iron at onsite and nonpoint of compliance locations. However, no exceedances at the offsite point of compliance location (EPA-18) have been observed during the review period, indicating the remedial objectives to control generation of contaminated groundwater and to protect surrounding groundwater are being met.

As described in Section 6.1.3, some analytical parameters included in the MOM plan have not been detected. A review and evaluation of historical data may offer some opportunity to optimize the monitoring plan to conserve resources for other uses.

Institutional Controls The institutional controls described in Section 4.1 are in force.

7.2 Question B

Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives (RAOs) used at the time of remedy selection still valid?

Yes. There have been no changes in the physical conditions of the Site or surrounding land uses that would change the exposure assumptions, cleanup levels or remedial action objectives for the Site. All performance standards are ARARs-based and were not based on calculated site-specific exposure assumptions or toxicity data.

On May 10, 2011, a search of permitted groundwater wells in the vicinity of the Site was conducted using the Colorado Division of Water Resources well permit database (http://water.state.co.us/Home/Pages/default.aspx). No permitted domestic, residential or drinking water use wells drawing on the shallow aquifer downgradient of the Site were identified. Therefore domestic use exposure pathways are not anticipated.

A review of current ARARs indicates that the State of Colorado Water Quality Control Commission has amended the Statewide Groundwater Performance Standards to include 1,4 dioxane. The updated performance standards are listed in Table A of The Basic Standards for Ground Water, Regulation No. 41 (5 CCR1002-41, effective November 30, 2009). Since 1, 4 dioxane generally is more mobile and persistent in the subsurface than the other organic contaminants found at this Site, EPA directed the PRPs to screen the groundwater monitoring wells for this compound. The groundwater monitoring wells were sampled for 1,4 dioxane in May 2011 to evaluate the presence at the Site. As described in Section 6.1.3, 1,4 dioxane was measured above the current Colorado standard of 6.1 ug/L in two of the onsite monitoring wells. This chemical was not detected at the other monitoring wells including the offsite point of compliance. While the presence of this chemical onsite does not impact current protectiveness because there is no exposure pathway, a delineation of the extent of the chemical’s presence and future monitoring will determine if protectiveness is affected in the future.

No other new ARARs or changes in current ARARs affect protectiveness of the remedy.

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7.3 Question C

Has any other information come to light that could call into question the protectiveness of the remedy?

No. There is no other information available that calls into question the protectiveness of the remedy

7.4 Technical Assessment Summary

An evaluation of current and historic site information and water quality data indicates that the remedial action objectives are being met. While exceedances of certain contaminants exist in the groundwater within the Site boundary and directly to the east of the Site boundary, there have been no exceedances at the offsite point of compliance monitoring location (EPA-18) indicating that offsite migration of contaminates is not affecting protectiveness of the remedy. Historic surface water monitoring and observations from the City of Louisville indicate that surface water has been in compliance, however, water has not been flowing during the majority of the sampling events. Additional sampling of surface waters will assist in future protectiveness determination.

Land use and exposure pathways have not changed since the last five year review. Changes in current ARARs or new ARARs that may have impacted protectiveness included only a new standard for 1, 4 dioxane. Sampling was conducted and 1,4 dioxane was determined to be present in two of the onsite groundwater monitoring wells. While this finding does not indicate the current protectiveness is compromised, delineating the extent of the 1,4 dioxane presence and monitoring for potential offsite migration is necessary for future protectiveness determinations.

Other information that was identified in the five-year review process includes potential required landfill cover maintenance. The current MOM plan does not address maintenance that may be required to repair animal disturbance or possible surfacing trash. While this does not currently impact protectiveness, it may in the future. Therefore plans for these maintenance activities should be put in place by updating the Site’s MOM plan. Additionally, optimization of the monitoring plan is expected to more effectively use resources and can be incorporated in an updated MOM plan.

8.0 Issues

Based on the information collected during the five-year review process, four issues were identified and are summarized in Table 3.

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Table 3: Issues Identified Affects Affects Future Issue Current Issue Protectiveness # Protectiveness (Y/N) (Y/N) 1 Surface Water Monitoring Locations typically dry N N during annual sampling events. 2 Monitoring, Operations and Maintenance plan N Y does not address required repairs for damage due to animal activity. 3 The water quality monitoring plan requires N N updating to optimize remedy efforts 4 1,4 dioxane was measured onsite above N Y Colorado groundwater standards.

In addition, the PRPs indicated that the future of the treatment plant is an important issue for Site management. The PRPs would like to dismantle the mothballed treatment plant because it is unlikely that the current configuration of the plant could be used to treat Site groundwater if a need should arise in the future. This issue does not impact protectiveness in the short term. EPA anticipates that EPA, CDPHE and the PRPs will come to a decision on this issue in the near future.

9.0 Recommendations and Follow-up Actions

Recommendations and required follow up actions have been developed to mitigate the issues identified in this five-year review process. These recommendations and follow up actions are listed in Table 4 along with the party responsible for the action, the oversight agency and the dates anticipated for completion of the mitigation action.

Table 4: Recommendations and Follow-up Actions Recommendations Anticipated Issue Affects Future Party Oversight Issue and Date of # Protectiveness Responsible Agency Follow-up Actions (Y/N) Completion 1 Surface Water Collect, at minimum, N Republic EPA June 2015 Monitoring one water sample Services, Locations when surface water is Inc and City typically dry present in the of Boulder during annual Community Ditch and sampling the Cowdrey drainage events. at both surface water POCs during the next five-year review period.

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Recommendations Anticipated Issue Affects Future Party Oversight Issue and Date of # Protectiveness Responsible Agency Follow-up Actions (Y/N) Completion 2 Monitoring, Update the Y Republic EPA December Operations and Monitoring, Services, 2012 Maintenance Operations and Inc and City plan does not Maintenance plan to of Boulder address specify maintenance required that will be performed repairs for to repair animal damage due to damage to the landfill animal activity. cover. 3 The water Optimize the water N Republic EPA/ December quality quality monitoring Services, CDPHE 2012 monitoring plan plan to effectively use Inc and City requires resources for of Boulder updating to protectiveness optimize monitoring. Include remedy efforts clarification of performance standards. 4 1,4 dioxane Update water quality Y Republic EPA/ December was measured monitoring plan to Services, CDPHE 2012 onsite above delineate the extent of Inc and City Colorado the 1,4 dioxane of Boulder groundwater presence and to standards. monitor for potential offsite migration.

The anticipated completion date of issue number 1 was selected to allow for sufficient time to coordinate sampling of these intermittent surface flows before the next five-year review process begins. Sampling of the surface flows is expected to take place as soon as is feasible and no later than June of 2015.

10.0 Protectiveness Statement

The remedy at OU1 currently protects human health and the environment because no exposure pathways have been identified for contaminated shallow groundwater in the vicinity of the Site, the downgradient offsite point of compliance (EPA-18) has consistently met established groundwater criteria, the RAOs are being met, the ICs are in place, and the remedy is intact. However, in order for the remedy to be protective in the long-term, the following actions need to be taken to ensure long-term protectiveness: update the maintenance plan to specify maintenance required to repair animal damage to the landfill cover and update the water quality monitoring plan to delineate the presence of and monitor for 1,4-dioxane. Additionally, monitoring of the surface and ground water, as well as land and water usage in the vicinity, will continue in order to determine if changes to remedy protectiveness occur in the future.

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11.0 Next Review

The Marshall Landfill Site requires ongoing five-year reviews in accordance with CERCLA § 121(c). The next five-year review will be completed by August of 2016.

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Figures ______

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Marshall Landfill Water Treatment Plant (Operation Marshall

Discontinued)

Landfill # # #

MarsahaflMarshall LakeLake

# Boulder Landfill

Figure 1: Site Location Area Enlarged Marshall Landfill Superfund Site NPL Site Boulder County, Colorado Date: May 18, 2011 Map Projection: UTM, Meters, 13 North, NAD83 £ Data Sources: NPL Site - U.S. EPA Region 8 (2011); 0 0.25 0.5 0.75 1 Miles Base - Bing Maps Web Service (2011). Colorado

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Colorado Colorado Area Enlarged Area

EPA-18 EPA-18

£ Cowdrey Drainage Drainage Cowdrey Marshall Landfill Marshall Treatment Water Plant (Operation Discontinued) Community Ditch Ditch Community T4-3 T4-3 T7-3 T7-3 T3-3 T3-3 CDO CDO CDPO 66th Street

T5-2 T5-2

NA-4 NA-4 U.S. EPA U.S. ESAT (2011); ESAT

ACRADIS (1994);ACRADIS

EPA-14 EPA-14 Water Pipeline Pipeline Water Boulder Boulder Landfill Marshall LandfillMarshall Drainages Pipeline & - UTM, Meters, 13 Meters, North, UTM, NAD83 NPL BoundaryNPL Division & Line -

USDA NAIP USDA aerial 1-meter photo (2009).

June 6, 2011

Wells, & SampleWells, - Locations Imagery - 0 500 1,000 1,500 2,000 Feet

Data Sources: Data (2011); Region 8 Date: Projection:Map

Boulder County, Colorado Colorado County, Boulder Marshall Landfill Superfund Site SuperfundSite Landfill Marshall

Figure 2: Water Quality Monitoring Locations 2:Figure Water

NPL NPL Boundary Pipeline Water Division Site Line Drainage Well Groundwater Sample Surface Location Water Cowdrey Reservoir #2 Reservoir Cowdrey

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Appendix A ______

List of Documents Reviewed

ARCADIS, 2003. Monitoring, Operations, and Maintenance (MOM) Plan, Marshall/Boulder Landfill Remedial Systems. Prepared for Browning-Ferris Industries, Inc and the City of Boulder, Colorado by ARCADIS. June 25.

ARCADIS, 2004. Technical Memorandum: Proposal to Terminate Active Remediation System Operation, Marshall/Boulder Landfill. Prepared for Allied Waste Industries, In and City of Boulder by ARCADIS. October 28.

ARCADIS, 2005. Clarification of Action Levels and Re-Sampling Requirements, Monitoring, Operations, and Maintenance (MOM) Plan, Marshall/Boulder Landfill Remediation Project. July 27.

Boulder County Commissioners, 2000. Intergovernmental Agreement, U.S. 36 Corridor Comprehensive Development Plan, June 20.

CDPHE Water Quality Control Commission. State of Colorado Basic Standards for Ground Water, Regulation No. 41 (5CCR 1002-41).

EPA, 1986. Record of Decision Marshall Landfill, CO. September 26.

EPA 1995. Five-Year Review (Type 1), Marshall/Boulder Landfill Superfund Site, Boulder County, Colorado. November 15.

EPA, 1992. Explanation of Significant Differences, Marshall Landfill, Boulder, CO. November 1.

EPA, 2001. Second Five-Year Review Report for Marshall Landfill Site, Boulder County, Colorado. September.

EPA, 2003. Explanation of Significant Differences, Marshall Landfill Superfund Site, Boulder County Colorado. September.

EPA, 2004. Approval Letter of Discontinuation of Groundwater Collection and Treatment.

EPA, 2006. Third Five-Year Review Report for Marshall Landfill Site, Boulder County, Colorado. September.

EPA, 2009. Response Letter to the Request for Reduction in Sampling Frequency, Marshall Landfill Superfund Site, Boulder County, Colorado. February 23. (letter was incorrectly dated 2008).

Herst & Associates, 2008. Final Report for Water Quality Monitoring Program, Marshall Landfill, September 26.

Appendix A - 1

Herst & Associates, 2009. November 2009 Groundwater and Surface Water Quality Evaluation Report, Marshall Landfill, Colorado, Herst & Associates, December 29.

Herst & Associates, 2011. November 2010 Groundwater and Surface Water Quality Evaluation Report, Marshall Landfill, Colorado, Herst & Associates, April 14.

Appendix A - 2

Appendix B ______

Water Quality Performance Standards for Site Surface and Ground Water

Water Quality Performance Standards for Site Surface and Ground Water Ground Water Surface Water Performance Surface Water Performance Parameter Performance Standard for the Upper Standard for the Lower Standard Cowdrey (Hardness=50) Cowdrey (Hardness=50) TDS (mg/L) 6501 Chloride (mg/L) 250 3202 320 Existing as of 01-01-00 or 250 Existing as of 01-01-00 or 250 Sulfate (mg/L) 250 whichever is less restrictive whichever is less restrictive Ammonia (as N) (mg/L) 0.213 N/A 0.02 Nitrate (as N) (mg/L) 10 10 10 Nitrite (as N) (mg/L) 1 1.0 0.05 Arsenic (mg/L) (Dissolved) 0.01 0.05 0.05 Barium (mg/L) (Dissolved) 2 -- Acute=.002 Cadmium (mg/L) (Dissolved) 0.005 0.01 Chronic=.0013 Chromium (mg/L) (Dissolved) 0.1 0.05 0.011 Copper (mg/L) (Dissolved) 1.0 1.0 Acute=0.007 Chronic=0.005

Existing as of 01-01-00 or Iron (mg/L) (Dissolved) 101 300ug/l whichever is less Same restrictive Acute=0.03 Lead (mg/L) (Dissolved) 0.05 Acute=0.05 Chronic=0.0012

Existing as of 01-01-00 or 50 ug/l Manganese (mg/L) (Dissolved) 11 whichever is less restrictive Same (dissolved)

Mercury (mg/L) (Dissolved) 0.002 Acute=0.002 Chronic=0.00001 Acute=0.26 Nickel (mg/L) (Dissolved) 0.1 N/A Chronic=0.029 Selenium (mg/L) (Dissolved) 0.05 Chronic=0.01 Acute=0.018 Chronic=0.005

Silver (mg/L) (Dissolved) 0.05 Acute=0.05 Acute=0.065 Chronic=0.066 Zinc (mg/L) (Dissolved) 5 Chronic=5.0 Same Phenols (mg/L) 4.2 Water Standard (WS)=4.2 Same 1,1-dichloroethane (mg/L) 0.007 WS=0.007 Same Trans 1,2-dichloroethylene (mg/L) 0.1 WS=0.1 Same 1,1,1-trichloroethane (mg/L) 0.2 WS=0.2 Same Tetrachloroethylene (mg/L) 0.005 WS=0.005 Same 1,1-dichlorothylene (mg/L) 0.007 WS=0.007 Same Ethylbenzene (mg/L) 0.680 WS=0.7 Same Toluene (mg/L) 1 WS=1.0 Same Benzene (mg/L) 0.005 WS=0.0012 Same Trichloroethylene (mg/L) 0.005 WS=0.05 Same 1 Alternate Background Standards are allowable pursuant to the Consent Decree and documented in the “Technical Memorandum: Review of Remediation Standards” dated July 29, 2002. 2 ESD, 1992 USEPA which documented Colorado Water Quality modified the chloride water quality stream standard for Upper and Lower Cowdrey Drainage to 320 (mg/L). This does not impact the standard for groundwater. 3 Risk Based Concentration Table value, for a single contaminant in a single medium, the RBC corresponds to the target risk or hazard quotient, EPA 4/2/2002.

Appendix B - 1

Appendix C ______

Photo Log of Site Conditions

Fourth Five-Year Review for the Marshall Landfill Site

Photograph 1. Thick vegitation on landfill cap, norther portion of the site. Cowdrey Drainage runs from the left to the center of the image.

Photograph 2. Vegetative cover appears in good condition on side slopes of Cowdrey Drainage.

Appendix C - 1 �

Photograph 3. Fencing in good condition around the Marshall (northern) portion of the landfill

Photograph 4. Fencing in good condition around the Boulder (southern) portion of the landfill.

Appendix C - 2 �

Photograph 5. Abandoned prairie dog burrow near eastern edge of the site boundary.

Photograph 6. Area in foreground shows evidence of past animal disturbance in the northern portion of the landfill looking east to 66th Street.

Appendix C - 3 �