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ANACONDA SMELTER NPL SITE ANACONDA REGIONAL WATER, WASTE & SOILS OPERABLE UNIT

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General: The SAP Addendum was approved with comment. Comments and responses have been incorporated into the final document.

Specific Comments:

1. Agency Comment:

Sampling should be conducted in a synoptic fashion for each watershed. This is especially important for Mill Creek.

Atlantic Richfield Response: Comment noted. The text in Section 2.1 states the following;” However, this sampling will include regular monthly sampling and storm flow sampling and will not necessarily target sustained high flows; therefore, the sample locations that NRD will sample have been included in the Mill Creek sampling required in this SAP Addendum such that a complete synoptic high flow data set is available on all locations within Mill Creek.” As discussed during the May 21, 2013 surface water technical meeting, the sampling goal is to collect Mill Creek within one day. Other drainages will be collected within one day, either prior to or after Mill Creek sampling depending on drainage specific flows.

2. Agency Comment:

If there is no flow at ANT-1, the sampling location in Antelope Creek can be moved upstream as needed to find flowing water.

Atlantic Richfield Response: Comment noted. Table 1 has been modified to reflect that if there is no flow at the proposed location, the sample location will be moved upstream as needed to find water flow. The location of the Antelope station will be discussed with oversight during the field work.

3. Agency Comment:

The background stations can be adjusted as needed based on access.

Atlantic Richfield Response: Comment noted. The location of the background stations will be discussed with oversight during the field work.

Response to Agency Comments for the Page 1 of 3 Draft Final Spring 2013 Anaconda High Flow Stream Sampling Event- Addendum 1 to the Final Willow Creek Mass Loading Study SAP 4. Agency Comment:

CAL-9 should be sampled at the highway bridge to be consistent with previous data.

Atlantic Richfield Response: Comment noted. The Figure 1 and Table 1 have been modified to reflect the change in CAL-9.

5. Agency Comment:

Agency oversight should be present when selecting new sites.

Atlantic Richfield Response: Comment noted. The sampling schedule will be coordinated with the Agencies and it is anticipate the Agencies will be present during the work.

6. Agency Comment:

Some of the historic locations shown on Figure 1 are inaccurate. Please consult with Agency oversight prior to sampling to locate historic sites.

Atlantic Richfield Response: Comment noted. Atlantic Richfield has visited the sample sites to determine and identify the location, to as close as possible, that historic samples were collected. The historic sample location will be utilized to the extent possible for all samples.

7. Agency Comment:

The reporting limits listed in Table 2 are too high for copper, cadmium, and lead. Recent reporting limits provided by Pace Analytical are shown in the table below and should be sufficient. Please update Table 2.

BPSOU Metals IDLs in Surface Water 2/21/2012 Metal IDL µg/L Cadmium 0.028 Copper 0.25 Lead 0.018 Zinc 2.5

Response to Agency Comments for the Page 2 of 3 Draft Final Spring 2013 Anaconda High Flow Stream Sampling Event- Addendum 1 to the Final Willow Creek Mass Loading Study SAP

Atlantic Richfield Response: Comment noted. Table 2 has been modified to reflect the following reporting limits obtained from Pace Analytical

Metal IDL µg/L Cadmium 0.032 Copper 0.174 Lead 0.046 Zinc 0.98

8. Agency Comment:

This plan does not address sediment sampling required in the SOW.

Atlantic Richfield Response: Comment noted. Sediment sampling will be addressed in the forthcoming 2013 storm water sampling SAP Addendum anticipated to be submitted in late May, 2013.

Response to Agency Comments for the Page 3 of 3 Draft Final Spring 2013 Anaconda High Flow Stream Sampling Event- Addendum 1 to the Final Willow Creek Mass Loading Study SAP

ANACONDA SMELTER NPL SITE ANACONDA REGIONAL WATER, WASTE & SOILS OPERABLE UNIT

Final

Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 to the Final Willow Creek Mass Loading Study Sampling and Analysis Plan (SAP)

Prepared for:

Atlantic Richfield Company 317 Anaconda Road Butte, Montana 59701

Prepared by:

Pioneer Technical Services, Inc. P. O. Box 3445 Butte, Montana 59702

May 23, 2013

TABLE OF CONTENTS

Page

1.0 INTRODUCTION ...... 1

2.0 HIGH FLOW STREAM WATER MONITORING PROGRAM ...... 1 2.1 High Flow Sampling Locations ...... 1 2.2 Sample Location Access ...... 2 2.3 Time and Duration of Sampling ...... 2 2.4 Sampling Methods and Procedures ...... 3 2.4.1 Sample Collection Method ...... 3 2.4.2 Flow Measurement Method ...... 3 2.5 Sampling Analysis and Procedures ...... 4 2.6 Safety ...... 4

3.0 DATA MANAGEMENT/ DATA VALIDATION ...... 4

4.0 REPORTING ...... 4

5.0 REFERENCES ...... 5

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page i of ii to the Final Willow Creek Mass Loading Study SAP Rev. 2

LIST OF FIGURES

Figure 1 ARWW&S Sitewide Surface Monitoring High Flow Sampling Locations

LIST OF TABLES

Table 1 High Flow Stream Monitoring Locations, ARWW&S OU, Anaconda – Deer Lodge County, Montana Table 2 List of Analytical Parameters, Detection Limits, Laboratory Methods and Holding Times for High Flow Surface Water Sample Analyses, ARWW&S OU, Anaconda - Deer Lodge County, MT

REVISION SUMMARY

Revision Author Version Description of Change Date Rev 0 Joe McElroy Draft Issued For Atlantic Richfield Review May 1, 2013 Rev 1 Joe McElroy Draft Final Issued to Agencies for review and May 10,2013 comment Rev 2 Joe McElroy Final Incorporates Agency comments and May 23, 2013 issues final version to Agencies.

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page ii of ii to the Final Willow Creek Mass Loading Study SAP Rev. 2

1.0 INTRODUCTION

This Spring 2013 Anaconda High Flow Stream Sampling Event, Addendum 1 to the Anaconda Regional Water, Waste, and Soils Operable Unit (ARWW&SOU) Final Willow Creek Mass Loading Study Sampling and Analysis Plan (SAP) (AERL, 2001) (SAP Addendum 1) has been developed to include sampling during high flow stream conditions within streams and tributaries in the Anaconda, Montana area. Background reference streams (Upper Boulder River and Little Boulder River) in the area of Bernice, Montana, will also be sampled. Collection of these high flow seasonal data will support ongoing development of the Conceptual Site Model (CSM) and will be utilized to update the available surface water data to support a Technical Impracticability (TI) Evaluation of certain surface water applicable or relevant and appropriate requirements. Data are being collected at select stream and tributary locations where existing data are incomplete or outdated. The sampling scope identified in this SAP Addendum 1 is consistent with what was proposed by the Agencies for high flow conditions in the recently distributed “Scope of Work (SOW) for Field Data Collection for Surface Water Technical Impracticability Evaluation” (CDM, 2013). A separate SAP addendum will be submitted addressing the remaining sampling identified in the Agencies SOW.

2.0 HIGH FLOW STREAM WATER MONITORING PROGRAM

The high flow stream water monitoring program consists of collecting high flow surface water data during the sustained high water flow conditions that typically occur in late May/June from prolonged snow melt. The sampling locations were developed based on the historical mass loading studies conducted in the late 1990s and early 2000s; locations were also selected based on Agency recommendations provided in the CDM (2013) SOW. To update historical data results and support a TI evaluation, the locations discussed in the section below will be sampled during high flow conditions in late May/June 2013.

2.1 High Flow Sampling Locations

High flow water monitoring has been historically conducted on the four major streams in the Anaconda area including Lost Creek, Warm Springs Creek, Mill Creek, and Willow Creek. Under this SAP Addendum 1, sampling will not be conducted on Warm Spring Creek or Willow Creek since existing U.S. Geological Survey (USGS) stations are adequate for determining high flow water quality. On Warm Springs Creek, the existing upstream USGS station (USGS- 12323760) is considered representative of upstream/background conditions. However, sampling is required on Lost Creek and Mill Creek to provide high flow data in addition to the ongoing USGS sample stations on Lost Creek and Mill Creek.

On Lost Creek, the existing USGS stations located on the lower reaches of Lost Creek provide sufficient high flow data, so a background sample located at the state park (LC-1M) will be sampled along with the two existing USGS stations on Lost Creek. For Mill Creek, additional high flow data are required on the upper reach of Mill Creek and its tributaries; therefore, under this SAP Addendum 1, all tributaries including and above Cabbage Gulch in Mill Creek, the mainstem of Mill Creek, and the two Mill Creek USGS stations will be sampled. The historic

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page 1 of 5 to the Final Willow Creek Mass Loading Study SAP Rev. 2

MC-5 station located on the mainstem of Mill Creek, upstream of the confluence with Ceanothus Creek, is included in this monitoring plan to evaluate upstream/background conditions in the mainstem of Mill Creek.

Given that Mill Creek tributaries and Willow Creek do not have upstream locations available for background sampling like Lost Creek (Station LC-1M), Warm Springs Creek (existing USGS Station-12323760), and Mill Creek main stem (Station MC-5), the Boulder River and the Little Boulder River upstream of Basin, Montana, were identified as potential background locations for comparison to these areas. Therefore, two sample locations on the Boulder River and one sample location on the Little Boulder River, above Basin, Montana, have been included in the high flow water sampling network. Data collected from the Boulder River and Little Boulder River as well as background locations in the Anaconda area (Mill Creek upstream [MC-5], Lost Creek upstream [LC-1M], and Warm Springs Creek [USGS 12323760]) will be evaluated for their applicability to act as background references for the Anaconda area streams and tributaries. In addition, samples will be collected on California Creek, Modesty Creek, and Antelope Creek at historic locations to update water quality and provide background information, in areas surrounding the four main Anaconda streams.

Note that the Natural Resource and Damage (NRD) program is also planning to conduct water quality samples in Mill Creek in 2013, specifically in Cabbage, Joiner, Muddy (and also within California Creek). However, this sampling will include regular monthly sampling and storm flow sampling and will not necessarily target sustained high flows; therefore, the sample locations that NRD will sample have been included in the Mill Creek sampling required in this SAP Addendum such that a complete synoptic high flow data set is available on all locations within Mill Creek.

The high flow event sampling locations are summarized in Table 1 and provided on Figure 1.

2.2 Sample Location Access

Atlantic Richfield Company (Atlantic Richfield) is currently coordinating access to all sample locations. Every attempt will be made to have access to all sample locations by the time sampling occurs. However, if access to a particular station has not been received or it is determined will not be granted, then the sample location will be adjusted if possible, to a location where access is available. The access or any potential access issues will be discussed with the Agencies prior to sampling to allow adequate time to determine if an alternate location is feasible.

2.3 Time and Duration of Sampling

In order to evaluate high flow stream conditions at the locations identified in Table 1, the sample locations will be monitored one time during a sustained high flow condition (typically in late May or June). The actual sampling will be conducted starting with the headwater locations first, then proceeding downstream to the extent practical.

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page 2 of 5 to the Final Willow Creek Mass Loading Study SAP Rev. 2

Timing of the high flow sampling will be determined by watching existing UGSG flow data to determine when runoff is nearing the peak flow. The sampling schedule will be verbally coordinated with the Agencies to allow for oversight and to reach agreement that high flow conditions are present and sampling is appropriate. Sampling will not be conducted immediately after a storm event since the purpose of this SAP Addendum 1 is to capture sustained high flows.

2.4 Sampling Methods and Procedures

2.4.1 Sample Collection Method

Field sampling of the streams and tributaries will be completed consistent with procedures described in the Clark Fork River Superfund Site Investigation (CFRSSI) Standard Operating Procedures (SOPs) SW-1, G-5, G-7, G-8, and HG-4 (ARCO, 1992a). Stream samples will be collected using a grab or equal width increment (EWI) technique as described in SOP SW-1 (ARCO, 1992a). If the channel width is less than approximately 5 feet across, a grab sample will be collected at the center of the channel. If the channel width is greater than 5 feet, the channel will be divided into 5-foot sections and the sample collected at the center of each section.

2.4.2 Flow Measurement Method

In addition to water quality sample collection, stream flow measurement at each location will be measured and/or estimated. Prior to the sampling, site reconnaissance will be performed at each of the sampling locations. During reconnaissance, it will determined if it will be safe to manually collect flow measurements. If it is determined to be potentially unsafe to collect manual flow measurements during high flow conditions, a staff gage will be installed and the cross-section surveyed during low flow conditions (survey may occur after high flow). At these locations, the field crew will document the staff gage reading at the time of sampling and the flow will be estimated utilizing Manning’s equation. Also the field crew will estimate the velocity utilizing a floating object and stopwatch. If a bridge is located near the sampling station, either upstream or downstream, flow gaging measurements will be taken by working from the bridge (provided it is safe), to provide additional information to check the flow estimates.

It is currently assumed that the flow measurements in the majority of the tributaries will be performed using a Marsh McBirney Model 2000 flow meter consistent with CFRSSI SOP SW-6 (ARCO, 1992). Stream flow will be measured by dividing the stream into multiple sections and measuring the depth and velocity of each section. Ideally, each section discharge should not exceed 5 percent (%) of the total flow. At sampling sites where discharge was too small to gage, flow will be estimated or measured with a calibrated bucket and stopwatch. On mainstem locations, the gaging location may be adjusted in the field to the nearest bridge or other feature that allows safe gaging.

Flows at the time of the high flow sampling will be obtained from the USGS database and documented for each stream sampled (MC-7D=USGS12323670, MC-10A=USGS12323700, LC-2=USGS12323840, LC-5=USGS12323850) in the Data Summary Report.

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page 3 of 5 to the Final Willow Creek Mass Loading Study SAP Rev. 2

2.5 Sampling Analysis and Procedures

High flow event samples will be analyzed for total and dissolved Constituents of Concern (COCs), hardness, total dissolved and suspended solids, dissolved organic carbon, turbidity, calcium, magnesium, sodium, potassium, and common ions, as listed in Table 2. In addition to the laboratory analysis, field crews will collect the following parameters: pH, temperature, specific conductance, dissolved oxygen, redox, and flow measurements. Pace Analytical will complete all laboratory work.

2.6 Safety

Safety concerns identified during preparation of this SAP Addendum 1 include weather, working around water, ground disturbance, working at heights, uneven terrain, and working close to highways and public roadways. Required personal protective equipment (PPE) will include work gloves, latex sampling gloves, hard hats, long-sleeved shirts, safety glasses with side shields, and steel-toed boots. The work will be conducted consistent the BP/Atlantic Richfield Control of Work (CoW) health and safety practices. The contractor(s) will be responsible for implementing and complying with these practices.

To minimize the potential for harm to personnel, equipment, or the environment, the work will be reviewed and the appropriate CoW items such as Work Risk Assessments (WRAs), Daily Toolbox Meeting Records, Task Safety Environmental Assessments (TSEAs), and permits, if any, will be completed, signed, and countersigned, as appropriate, prior to initiating any tasks associated with this work.

A Project Site-Specific Health and Safety Plan will be developed for the project.

3.0 DATA MANAGEMENT/DATA VALIDATION

Analytical results will be reported using a simplified format (i.e., without full data packages) including data tables with detection limit qualifiers and quality control (QC) summary tables. The general approach to the data validation is described in the Clark Fork River Superfund Investigation Data Management/Data Validation Plan, Revision 2 (ARCO, 1992b). A simplified validation system will be implemented consistent with the procedures described in the EPA Addenda to the Clark Fork River Superfund Site Investigations Data Management/ Data Validation Plan (EPA, 2000).

4.0 REPORTING

Data will be summarized and presented in one Data Summary Report. The Data Summary Report will include data validation, data summary tables with qualifiers, field activities and notes, and other pertinent data. All data will be electronically available to the Agencies. Data will be uploaded into the Anaconda Smelter National Priorities List (NPL) Site Surface Water Database. Analysis of the data will be performed as part of the ongoing Anaconda Smelter NPL Site Surface Water Management Plan preparation and Surface Water Total Metals TI Evaluation.

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page 4 of 5 to the Final Willow Creek Mass Loading Study SAP Rev. 2

5.0 REFERENCES

AERL, 2001. Anaconda NPL Site, Anaconda Regional Water, Waste and Soils Operable Unit, Final Willow Creek Mass Loading Study Sampling and Analysis Plan (SAP). March 2001.

ARCO, 1992a. Clark Fork River Superfund Site Investigations, Standard Operating Procedures. September 1992.

ARCO, 1992b. Clark Fork River Superfund Investigations Data Management/Data Validation Plan, Revision 2. September 1992.

BP, 2007. Guidance on Practice for Design and Construction Activities Adjacent to or In Water bodies in Conduct of Remediation or On-Shore Decommissioning Activities.

CDM, 2013. Scope of Work for Field Data Collection for Surface Water Technical Impracticability Evaluation. April 15, 2013.

EPA, 2000. Addenda to the Clark Fork River Superfund Site Investigations Data Management/Data Validation. February 15, 2000.

Final Spring 2013 Anaconda High Flow Stream Sampling Event - Addendum 1 Page 5 of 5 to the Final Willow Creek Mass Loading Study SAP Rev. 2

FIGURES

MOD-4 !.

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ANT-1 !. BR-1 (USGS) !.

!. BR-2 LC-1M !. WS-6 (USGS) !.

LC-2 (USGS) !.

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MCT-8 !. !. !. MCT-9 MC-7D MCT-7 (USGS) MCT-6 !. WC-13 MCT-5 !. (USGS) !. !. !. MC-5 MCT-4 CG-5 !.!. !. CC-9 !. MCT-2 !. MCT-3

MCT-1 !. MCT-0 !.!. CC-6

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CAL-2 !.

CAL-9 !.

DISPLAYED AS: PROJECTION/ZONE: MSP FIGURE 1 ARWW&S SITEWIDE DATUM: NAD 83 UNITS: INTERNATIONAL FEET SURFACE WATER MONITORING LEGEND SOURCE: PIONEER/USGS HIGH FLOW !. USGS STATIONS (FOR MONITORING STREAM FLOWS) 0 3,000 6,000 12,000 18,000 24,000 SAMPLING LOCATIONS !. HIGH FLOW SAMPLING LOCATIONS Feet DATE: 5/21/2013

Path: \\192.168.254.15\project$\ARCO\ARWW&S\2013\SiteWideSurfaceWaterSampling\Drawings\Arcmap\Project\HighFlow\SWSW-HFLOW-GI-PLN-002-13.mxd

TABLES

TABLE 1 HIGH FLOW STREAM MONITORING LOCATIONS, ARWW&S OU, ANACONDA – DEER LODGE COUNTY, MONTANA

Sample Stream ID Coordinates USGS ID Type Description Easting Northing Mill Creek and Tributary Sampling Locations In mainstem of Mill Creek upstream MC-5 1090357.501 681542.3455 NA Mainstem of confluence with Ceanothus Creek. In Mainstem downstream of the MC-7D 1102833.698 687652.1269 12323670 Mainstem confluence with Cabbage Gulch. USGS Station located upstream of MC-10A 1128999.598 698025.4262 12323770 Mainstem confluence with Mil-Willow Bypass. In Muddy Creek located upstream of the confluence with Ceanothus MCT-0 1128999.598 698025.4262 NA Tributary Creek. In Andesite Creek located upstream MCT-1 1085650.993 673394.6152 NA Tributary of confluence with Ceanothus Creek. In Hoodoo Creek located upstream of MCT-2 1084594.723 675278.6414 NA Tributary confluence with Ceanothus Creek. In Moose Creek located upstream of MCT-3 1085631.236 677634.8642 NA Tributary confluence with Ceanothus Creek. In Joiner Creek located upstream of MCT-4 1088029.802 679102.518 NA Tributary confluence with Mill Creek. In Clear Creek located upstream of MCT-5 1092413.43 681576.9987 NA Tributary confluence with Mill Creek. In Cobble Creek located upstream of MCT-6 1093795.934 683818.0072 NA Tributary confluence with Mill Creek. In Silver Creek located upstream of MCT-7 1095616.355 684671.4436 NA Tributary confluence with Mill Creek. In Lapilli Creek located upstream of MCT-8 1096601.769 685158.2238 NA Tributary confluence with Mill Creek. In Lost Horse Creek located upstream of confluence with Mill MCT-9 1100664.374 687673.1539 NA Tributary Creek. In Ceanothus Creek located upstream CC-6 1101060.875 687584.3451 NA Tributary of confluence with Muddy Creek. In Ceanothus Creek located upstream CC-9 1085374.907 673381.0666 NA Tributary of confluence with Mill Creek. In Cabbage Gulch located upstream CG-5 1090630.131 681414.5128 NA Tributary of confluence with Mill Creek.

Final Addendum 1 to the Final Willow Creek Page 1 of 2 Mass Loading Study SAP Rev. 2 Lost Creek In mainstem of Lost creek at state LC-1M 1092338.317 724701.5797 NA Mainstem park. In mainstem of Lost Creek west of highway 273 at existing USGS LC-2 1109566.039 715596.4511 12323840 Mainstem Station. In mainstem of Lost creek west of LC-5 1140538.908 734952.5515 12323850 Mainstem frontage Road at USGS Station. Other/Background In main stem of California Creek at CAL-2 1090751.423 658364.9413 NA Mainstem headwaters. In main stem of California Creek CAL-9 1075638.16 650843.66 NA Mainstem located at the highway bridge. In modesty Creek at previously MOD-4 1111224.272 749022.8281 NA Mainstem sampled location. Need to field verify, to determine exact location. If there is no flowing water at this location it will be moved upstream as needed to find flowing ANT-1 1112738.044 729515.6329 NA Mainstem water. Reference Streams (Boulder River and Little Boulder River) Boulder River at about Trapper Creek near Basin, MT. Need to field BR-1 1213758.436 747716.2123 461541112291001 Mainstem verify. Boulder River above Lowland Gulch, BR-2 1234043.816 744170.4846 NA Mainstem above Bernice. Need to field verify. USGS Station on mainstem of Little Boulder River about North Fork near LBR-1 1298466.652 719745.2369 461135112085101 Mainstem Boulder, MT. Need to field verify.

Final Addendum 1 to the Final Willow Creek Page 2 of 2 Mass Loading Study SAP Rev. 2

TABLE 2 LIST OF ANALYTICAL PARAMETERS, DETECTION LIMITS, LABORATORY METHODS AND HOLDING TIMES FOR HIGH FLOW SURFACE WATER SAMPLE ANALYSES, ARWW&S OU, ANACONDA - DEER LODGE COUNTY, MT

Analyte Desired Method Preservative Holding Reporting Time Limits Total Arsenic (As) 0.093 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Cadmium (Cd) 0.032 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Copper (Cu) 0.174 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Lead (Pb) 0.046 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Zinc (Zn) 0.98 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Calcium (Ca) 20 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Potassium (K) 20 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Magnesium (Mg) 5.0 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Total Sodium (Na) 50 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Dissolved As 0.093 µg/L ICP-MS by EPA Filter to 0.45 6 months Method 200.8 µm, HNO3 to pH <2, Cool to 4°C Dissolved Cd 0.032 µg/L ICP-MS by EPA Filter to 0.45 6 months Method 200.8 µm, HNO3 to pH <2, Cool to 4°C

Final SAP Addendum 1 to the Final Willow Creek Page 1 of 2 Mass Loading Study SAP Rev. 2

Dissolved Cu 0.174 µg/L ICP-MS by EPA Filter to 0.45 6 months Method 200.8 µm, HNO3 to pH <2, Cool to 4°C Dissolved Pb 0.046 µg/L ICP-MS by EPA Filter to 0.45 6 months Method 200.8 µm, HNO3 to pH <2, Cool to 4°C Dissolved Zn 0.98 µg/L ICP-MS by EPA Filter to 0.45 6 months Method 200.8 µm, HNO3 to pH <2, Cool to 4°C Dissolved Ca 20 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Dissolved K 20 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Dissolved Mg 5.0 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Dissolved Na 50 µg/L ICP-MS by EPA HNO3 to pH 6 months Method 200.8 <2, Cool to 4°C Turbidity 0.3 NTU EPA 180.1 Cool to 4°C 48 hours Dissolved Organic SM5310C H2SO4 to 28 days Carbon pH<2 after filtering; Cool to 4°C Hardness as CaCO3 NA SM2340B HNO3 to pH 6 months <2, Cool to 4°C Total Suspended Solids 1.0 mg/L SM 2540 D Cool to 4°C 7 days Total Dissolved Solids, 20 mg/L SM 2540 C 7 days Sulfate, Chloride, 1.0 mg/L EPA 300.0 28 days Calcium, Magnesium, Sodium, Potassium Total Alkalinity 5.0 mg/L SM 2320 B 14 days

Final SAP Addendum 1 to the Final Willow Creek Page 2 of 2 Mass Loading Study SAP Rev. 2