Amendment_0007_Attachment_Revised_Final_Callahan_Mine_Monthly_Monitoring_Report.pdf

Prepared for:

U.S. Army Corps of Engineers New England District

696 Virginia Road Concord, MA 01742

April 5-6, 2017, Performance Assessment Summary Report

Version: Final

Callahan Mine Superfund Site (MED980524128) Operable Unit 3 – TP-1 Performance Assessment

Brooksville, Maine

June 26, 2017

Prepared by:

Credere Associates, LLC 776 Main Street

Westbrook, Maine 04092

Contract W912WJ-16-C-0013

April 5-6, 2017, Performance Assessment Summary Report Version: Final Callahan Mine Superfund Site, Operable Unit 3 – TP-1 Performance Assessment Brooksville, Maine June 26, 2017 i

TABLE OF CONTENTS

1. INTRODUCTION.............................................................................................................. 1-1

1.1 Site Description ............................................................................................................................. 1-1

1.2 Site and Regulatory History .......................................................................................................... 1-1

2. OBJECTIVES .................................................................................................................... 2-1

2.1 Statement of Objectives ................................................................................................................ 2-1

3. COMPLETED ACTIVITIES AND METHODOLOGY ............................................... 3-1

3.1 Site Inspection ............................................................................................................................... 3-1

3.2 Bioreactor O&M ........................................................................................................................... 3-1

3.3 Bioreactor Flow Assessment ......................................................................................................... 3-1

3.4 Groundwater Level Gauging ......................................................................................................... 3-2

3.5 Climate Data Download ................................................................................................................ 3-2

3.6 Water Quality Sampling ............................................................................................................... 3-3

3.7 Decontamination ........................................................................................................................... 3-3

3.8 Investigation Derived Waste ......................................................................................................... 3-4

4. RESULTS ........................................................................................................................... 4-1

4.1 Site Inspection Results .................................................................................................................. 4-1

4.2 Bioreactor O&M Results .............................................................................................................. 4-1

4.3 Bioreactor Flow Assessment ......................................................................................................... 4-1

4.4 Groundwater Level Gauging Results ............................................................................................ 4-2

4.5 Water Quality Sampling Results ................................................................................................... 4-3

5. CONCLUSIONS SUMMARY .......................................................................................... 5-1

6. REFERENCES ................................................................................................................... 6-1 ii

FIGURES

Figure 1 ................................................................................................................ Site Location Plan Figure 2 ................................................................................................................. Detailed Site Plan Figure 3 ................................................... Groundwater Contours Through Shallow Tailings Wells Figure 4 ........................................................ Groundwater Contours Through Deep Tailings Wells

TABLES

Table 1 ............................. Summary of Monitoring Wells for Gauging and Transducer Download Table 2 .......................................................................................... Water Quality Sample Summary Table 3 .................................................... Summary of Measured HD-2 and Bioreactor Flow Rates Table 4 .......................... Summary of Groundwater Gauging Data, Elevations, and Level Changes Table 5 .................................................... Groundwater Elevation Change/Drawdown Calculations Table 6 ............................................................................................... Summary of Field Parameters Table 7 ......................................................................... Summary of Water Quality Sample Results

CHARTS

Chart 1 .....................................Groundwater Elevation Time Series Plot – MW-610 (Background) Chart 2 ............................................................... Groundwater Elevation Time Series Plot – DW-1 Chart 3 ........................................................ Groundwater Elevation Time Series Plot – MW-602D Chart 4 ......................................................... Groundwater Elevation Time Series Plot – MW-602S Chart 5 ........................................................ Groundwater Elevation Time Series Plot – MW-604D Chart 6 ......................................................... Groundwater Elevation Time Series Plot – MW-604S Chart 7 ........................................................ Groundwater Elevation Time Series Plot – MW-605D Chart 8 ....................................................... Groundwater Elevation Time Series Plot – OW-1124A Chart 9 ....................................................... Groundwater Elevation Time Series Plot – OW-1140D Chart 10 ..................................................... Groundwater Elevation Time Series Plot – OW-1142D Chart 11………..…. Groundwater Elevation Time Series Plot – Deep Tailings Wells along HD-2

APPENDICES

Appendix A ................................................................................................ Site Inspection Checklist Appendix B ....................................................................................................................... Photo Log Appendix C .......................................... Transducer Download Data (files included electronically) Appendix D .................................................................................................................. Climate Data Appendix E ........................................................................................ Laboratory Analytical Report Appendix F...................................................................... Maine DEP Basic Data Review Checklist iii

LIST OF ACRONYMS

ARA – Absolute Resource Associates btor – below top of riser °C – degrees Celsius CCC - criterion continuous concentration CENAE – Corps of Engineers New England District Credere – Credere Associates, LLC DEP – Department of Environmental Protection DO – dissolved oxygen DOT – Maine Department of Transportation DS – drainage structure ELAP – Environmental Laboratory Accreditation Program EPA – U.S. Environmental Protection Agency ft3 – cubic feet ft2 – square feet gpm – gallons per minute HD – horizontal drain mg/L – milligrams per liter mV - millivolts MW – monitoring well NAVD – North American Vertical Datum NOAA - National Oceanic and Atmospheric Administration NPL – National Priorities List NRWQC - EPA National Recommended Water Quality Criteria NWS – National Weather Service ORP – oxidation reduction potential OU – operable unit O&M – operations & maintenance PCB – polychlorinated biphenyl PWS – Performance Work Statement QAPP – Quality Assurance Project Plan SAP – Sampling and Analysis Plan SWQC - Maine DEP Statewide Surface Water Quality Criteria µS/cm – micro Siemens per centimeter USACE – U.S. Army Corps of Engineers YSI – Yellow Springs Instrument

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1. INTRODUCTION

Credere Associates, LLC (Credere) was retained by the U.S. Army Corp of Engineers (USACE) New England District (CENAE) under contract W912WJ-16-C-0013 to assess and maintain the performance of the Phase I Operable Unit (OU) 3 remedial actions at the Callahan Mine Superfund Site, located in Brooksville, Hancock County, Maine (Site). A Site location plan is included as Figure 1. This March 8-9, 2017, Performance Assessment Summary Report has been prepared in accordance with Credere’s Sampling and Analysis Plan (SAP)/Quality Assurance Project Plan (QAPP) dated November 29, 2016 (Credere, 2016). The SAP was developed in accordance with the Performance Work Statement (PWS) prepared by CENAE dated July 12, 2016 (CENAE, 2016).

1.1 SITE DESCRIPTION

The Callahan Mine is a 120-acre former lead, zinc, and copper mine located in the village of Harborside in the Town of Brooksville, Maine. The Site is located on the northwest corner of the Cape Rosier peninsula and is bordered by the tidal estuary, Goose Pond, to the east and north, which is bordered by the Holbrook Island Sanctuary State Park adjacent to Penobscot Bay.

Remedial design was completed in 2009 for the entire mine known as OU 1. OU 3 is a component of the OU 1 remedial design and comprises the mine’s 21-acre tailings impoundment and associated access roads. It is estimated the impoundment consists of 716,000 cubic yards of tailings and waste rock (CES Inc. [CES], 2016a).

1.2 SITE AND REGULATORY HISTORY

Exploration as a mine began in 1880 and continued intermittently through the 1970s with the mine being intensively quarried between 1968 and 1972. Sulfide ore was mined from the open pit mine in Goose Pond estuary. The ore was processed and concentrated onsite but shipped offsite for smelting. Waste tailings and tailings slurry were disposed onsite in the OU 3 tailings impoundment. Impoundment seeps were identified as a point source discharge of cadmium, copper, and zinc to surface water and sediment of the adjoining salt marsh and Goose Pond

(AMEC, 2014).

In September 2002, the Site was added to the EPA National Priorities List (NPL). The Site was assessed and a feasibility study was completed in 2009 to evaluate cleanup options. The OU 1 component of the OU 1 remedial design was completed between 2010 and 2013, with polychlorinated biphenyl (PCB) and metals impacted soil placed within the tailings impoundment. OU 2 is also a component of the OU 1 remedial design and includes additional soil and groundwater contamination beyond the previously delineated contamination in OU 1.

OU 2 is still being investigated.

The objectives of the OU 3 remedial design are to reduce point source discharges from the tailings impoundment, improve static and seismic stability of the slope of the tailings impoundment, and minimize truck traffic during remediation (AMEC, 2014). Phase I of the OU 3 remedial actions was completed to lower the groundwater table in the eastern portion of the

1-2 tailing impoundment to allow for the relocation of tailings as part of the Phase II remedial actions. The 30% Design Submission, Basis of Design Report (AMEC, 2013) presents numerical groundwater models that include predicted groundwater elevations and dewatering flow rates over time for the Selected Alternative – Horizontal Well(s). From July to November 2015, a 975-linear foot horizontal drain was installed along the eastern portion of the tailings impoundment (horizontal drain 2 [HD-2]) to lower the groundwater table and a compost bioreactor treatment system was installed to treat the dewatering flows as part of Phase I remedial actions (CES, 2016a). The Phase I remedial system has been assessed on a routine basis to inspect the physical condition of the systems, assess flow and treatment system effectiveness, and assess performance of the Phase I OU 3 remedial actions (CES, 2016b).

Phase II of the OU 3 remedial actions may consist of installation of additional horizontal borings for dewatering of the tailings impoundment; construction of two additional compost bioreactors for treatment of dewatering flows; and excavation, regrading, and capping of the tailings impoundment in order to reduce water recharge, infiltration, and seepage. If executed, this work is anticipated to begin in 2017 (AMEC, 2014).

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2. OBJECTIVES

2.1 STATEMENT OF OBJECTIVES

The primary objective of the work outlined in the SAP/QAPP and PWS is to assess and maintain the performance of the Phase I OU 3 remedial actions. The following Site-specific objectives for this work were established:

Inspect the OU 3 area for evidence of wear, settlement, erosion, etc. to identify areas requiring corrective action(s)

Maintain optimal operation of the horizontal drain HD-2 and compost bioreactor through inspection and subsequent maintenance, where necessary

Evaluate the dewatering performance of the horizontal drain HD-2 to achieve adequate groundwater level reduction to the basis of design elevation (46 feet North American Vertical Datum [NAVD] 88) along the eastern portion of the tailings impoundment to allow for Phase II remedial actions to begin

Assess the compost bioreactor treatment system performance to ensure effluent meets the National Recommended Water Quality Criteria (NRWQC; U.S. Environmental Protection Agency [EPA], 2016) and ambient water quality criteria in Chapter 584:

Statewide Surface Water Quality Criteria (SWQC) for Toxic Pollutants (Maine Department of Environmental Protection [DEP], 2012)

Assess the overall effectiveness of the Phase I OU 3 remediation systems using the increasing data set

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3. COMPLETED ACTIVITIES AND METHODOLOGY

Credere completed the following activities to meet the objectives outlined in Section 2.1 and in accordance with the SAP/QAPP (Credere, 2016) and PWS (CENAE, 2016). The work outlined below was completed on April 5 and 6, 2017. A Detailed Site Plan showing pertinent Site features, and well and sample locations is provided as Figure 2.

3.1 SITE INSPECTION

The Site inspection was performed on April 5 and 6, 2017, to observe and document changes to Site features including wear, settlement, erosion, etc. and identify the need for corrective action(s). The condition of the access roads, stormwater conveyance systems, discharge structures, piping and valves, compost bioreactor, spillways, aeration ponds, stormwater ditches, monitoring wells, and active and previously unidentified seeps were inspected and documented.

Site inspection was conducted by physically walking and inspecting the Site. A Site Inspection Checklist was completed in the field to document conditions and changes as well as corrective actions performed or required. A copy of the completed Site Inspection Checklist is included in Appendix A. Conditions were also documented by photographs, which are included in the Site Inspection Photo Log in Appendix B. Routine photographic stations were used during the Site visit and are identified on Figure 2.

Conditions at the time of the Site inspection were compared to the previous month’s inspection checklist and photo log to identify potential changes in conditions at the Site.

3.2 BIOREACTOR O&M

During the Site inspection, no evidence of erosion, debris, or the need for back flushing due to reduced flow rates was observed. Where possible, surface ice was broken up and channels were created to direct any future surface flows towards the discharge locations.

3.3 BIOREACTOR FLOW ASSESSMENT

Figure 2 shows the locations for flow measurement and observation. The Site inspection requires flow measurements at discharge structure 3 (DS-3, the bioreactor intake), bioreactor effluent (BCR), Aeration Pond #1 (AP-1) effluent, and Aeration Pond #2 effluent (AP-2) to assess the hydraulic load on the system, and observation of relative flow at the combined aeration pond discharge and stormwater ditch (ADSD) to assess contribution to discharge from the stormwater swale.

Influent Flow Assessment

The bioreactor influent flow was calculated via a rising head test performed inside the discharge structure 3 (DS-3). The influent flow was measure by closing the gate valve for both the influent flow and effluent flow of the structure, removing sufficient water from DS-3 using a pump to allow for inspection of the structure, reopening the influent gate valve and allowing any built up

3-2 surge of water from closing the HD-2 valve to return to steady flow, then measuring the water depth within DS-3 and monitoring the time required for the water level to rise approximately 3 inches (i.e., over 50 gallons). Influent flow was then calculated based on the DS-3 structure manufacturer’s specification that 1 inch of water corresponds to 17.58 gallons. The effluent gate valve was re-opened at the conclusion of the test.

In addition to the rising head test, the HD-2 influent flow rate was also measured from the sample port in DS-3 by monitoring the time to fill a certain volume. A graduated container was filled and the time to fill a volume recorded; these measurements were repeated 3 times and the average of the three measurements was calculated. Flow rates were calculated in gallons per minute (gpm) and recorded on the Site Inspection Checklist in Appendix A.

Bioreactor Effluent, Aeration Pond #1 Effluent, Aeration Pond #2 Effluent, and Combined Aeration Pond and Stormwater Ditch Flow Assessment

Flow rates were calculated for the bioreactor effluent and Aeration Pond #1 effluent during this Site inspection (BCR and AP-1 on Figure 2). The Aeration Pond #2 discharge was spread out beneath an ice sheet and was not a cohesive flow, therefore, a flow rate measurement could not be obtained (AP-2 on Figure 2). The combination point of the Aeration Pond #2 and stormwater ditch (ADSD on Figure 2) was evaluated for relative flow.

The BCR, AP-1, and AP-2 effluent flow rates were measured by monitoring the time required to fill a given volume from the discharge points indicated on Figure 2. A graduated container was filled and the time required to fill the volume was recorded. This procedure was repeated three times and the average of the three measurements was calculated. Flow rates were calculated in gallons per minute (gpm) and recorded on the Site Inspection Checklist in Appendix A.

3.4 GROUNDWATER LEVEL GAUGING

Groundwater level measurements were conducted to evaluate the effectiveness of the horizontal drain HD-2 at dewatering the tailing impoundment to the targeted elevation (46 feet NAVD 88).

Water level data was collected in conjunction with local precipitation data to assess the rate of dewatering. Water levels were measured manually and through download of transducer data from the wells summarized in Table 1. Downloaded transducer data for this period is included in Appendix C.

Water levels were collected from wells using a manual Solinst (or similar) water level indicator.

Manual water levels were recorded to the nearest 0.01 foot on the Site Inspection Checklist included in Appendix A. Water level data was also downloaded from previously installed transducers using In-Situ® software installed on a RuggedReader®.

3.5 CLIMATE DATA DOWNLOAD

Climate data (primarily including precipitation) was downloaded from the closest National Oceanic and Atmospheric Administration (NOAA), National Weather Service (NWS) Forecast Office in Caribou, Maine, for the East Surry, Maine, weather station located approximately 18

3-3 miles northeast of the Site. Monthly precipitation data summaries with daily precipitation totals were downloaded from the database at the following link:

http://w2.weather.gov/climate/xmacis.php?wfo=car.

Data for this reporting period are included in Appendix D.

3.6 WATER QUALITY SAMPLING

Water quality samples were collected from four locations: the discharge structure influent (i.e., from HD-2), the bioreactor effluent, the Aeration Pond #2 effluent, and combined flow from the aeration pond discharge and stormwater ditch. Aeration Pond #2 was mostly frozen and the discharge was not a cohesive flow, so samples were collected from cascade point of the Aeration Pond #1 effluent. The discharge structure influent (sample ID DS-3-0417 and duplicate sample ID DS-30-0417), the bioreactor effluent (sample ID BCR-0417), the Aeration Pond #1 effluent (sample ID AP-1-0417), and the combined aeration pond discharge and stormwater ditch were sampled on April 6, 2017. Samples were collected from the downstream location first (i.e.

ADSD) and then sampled consecutively upstream (AP-1, BCR, DS-3, respectively).

Water was collected from each sampled point using a peristaltic pump. Tubing was submerged in the pipe outflow at the DS-3 sampling point and in the ditch a short distance downstream of the combination point at ADSD, and in an overflowing container at the bioreactor effluent drop point and Aeration Pond #1 drop point. New tubing was used at each sampling location. Water was pumped to a Yellow Springs Instrument (YSI) flow through cell at 100 to 200 mL per minute for 5 minutes; then dissolved oxygen (DO), oxidation reduction potential (ORP), specific conductivity, temperature, and pH were monitored for three readings spaced 5 minutes apart to allow for complete exchange of water in the flow through cell. Turbidity measurements were collected at the same 5 minute intervals directly from the sampling locations and measured using a Hach 2100Q turbidity meter. The YSI 556 multi-parameter sonde was equipped with a membrane DO probe in accordance with EPA method 360.1. Field parameters were recorded on the Site Inspection Checklist included in Appendix A. DO for each sampling point was determined by taking the average of the three readings.

For chemical analyses, samples were collected directly into laboratory provided containers prior to the YSI flow through cell. Dissolved metals samples were field filtered with an in-line 0.45-micron filter. Samples were securely stored on ice and submitted to Absolute Resource Associates (ARA) of Portsmouth, New Hampshire. ARA is an Environmental Laboratory Accreditation Program (ELAP) and Maine certified laboratory. Table 2 summarizes the samples collected during this Site Inspection.

3.7 DECONTAMINATION

Non-disposable water quality measurement equipment and water level indicators were decontaminated between sample locations and wells, respectively. New tubing was used at each sample location.

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The water level meters were rinsed with potable water directly after removal from a well while the equipment was still damp/wet. The outside of the water level meter probe and reel tape was wiped using disposable paper towels to remove material adhering to the equipment, if any. The equipment was then rinsed thoroughly with deionized water.

YSI flow-through cell and the Hach 2100Q turbidity meter were rinsed of accumulated sediment between uses.

3.8 INVESTIGATION DERIVED WASTE

Purge water generated during the rising head test at DS-3 and during purging of sample locations for field parameters was discharged back to the bioreactor structure after sampling. Rinse water for water level meters was discharged directly onto the surface of the tailings pile. Therefore, no investigation derived liquid waste was generated. Solid waste (e.g., tubing, filters, paper towels, gloves, etc.) were disposed off-site as general household waste.

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4. RESULTS

The following section summarizes the results of the Site inspections, bioreactor O&M, bioreactor flow assessment, groundwater level gauging, and water quality sampling.

4.1 SITE INSPECTION RESULTS

A copy of the Site Inspection Checklist is included as Appendix A. A photo log of Site conditions is included as Appendix B, and the routine photographic station locations are identified on Figure 2.

No evidence of erosion, animal burrowing, vandalism, or other deterioration was observed at the Site. The aeration ponds were found to be partially frozen due to cold temperatures; however, water was flowing at the discharge points of the bioreactor and both aeration ponds.

All transducers were reset during the April 5-6, 2017 inspection to record depth to water measurements, rather than the depth of the transducer below water.

4.2 BIOREACTOR O&M RESULTS

Evidence of the need for back flushing was not identified during this Site visit as influent flow into DS-3 had low turbidity and flow rates were consistent with prior Site inspection flow rates.

Where the aeration ponds were partially frozen, ice was broken up to facilitate future flows.

4.3 BIOREACTOR FLOW ASSESSMENT

Flow rates measured during the April 5 and 6, 2017, inspection are summarized with historical flow rates on Table 3. The calculated rising head test flow rate from the HD-2 drain into DS-3 was 2.08 gpm. This was lower than the March 2017 flow rate (2.29 gpm), but within the range of flows during the previous year. Direct measurement of the flow rate into DS-3 as measured from the sample port indicated an average flow rate of 1.75 gpm. Groundwater modeling for HD-2 in the 30% Design Submission, Basis of Design Report (AMEC, 2013) predicted a flow rate of 1.28 gpm after 492 days of operation (extrapolated from Table 3 – Simulation Run Summary Flows and Accumulated Volumes) after an initial period of higher flows and subsequent lowering of average groundwater elevations in the impoundment.

Using a historical average of 2.21 gpm (calculated based on the flow rates between December 2015 and April 2017), the calculated volume of water discharged from HD-2 between December 1, 2015, and April 6, 2017, (492 days), is 1,565,741 gallons.

The average flow rate measured from the bioreactor discharge was 1.50 gpm, and the average flow rate measured from the Aeration Pond #1 discharge was 0.75 gpm. Aeration Pond #2 was mostly frozen, and though discharge was observed, there was no cohesive, measurable flow at discharge location AP-2. Flow measurements at this location will resume in May 2017 if conditions allow. Flow was observed at the combination point of the stormwater ditch and

4-2 aeration pond discharge, with significant stormwater flow, and a cloudy discharge from the aeration pond spillway.

4.4 GROUNDWATER LEVEL GAUGING RESULTS

Groundwater measurements are summarized in Table 4. Measured depths to water were generally consistent with previous gauging rounds and groundwater elevations showed an average site-wide decrease of 0.72 feet since December 2015, and a site-wide increase of 0.52 feet since the March 2017 inspection. Calculated groundwater elevations were within ±1 foot of the prior round’s elevations for wells gauged except for MW-604S (rose 2.80 feet), OW-1131 (rose 2.07 feet), OW-1141D (rose 7.71 feet) OW-1141S (rose 1.34 feet), and OW-1142S (rose

5.88 feet). Well OW-1140S was dry.

Groundwater elevation contours for the shallow and deep monitoring well locations are shown on Figures 3 and 4, respectively. Groundwater flow is to the east and appears to follow the contour of the impoundment. There is also a downward hydraulic gradient between the shallow well series and deep wells.

For the 16 wells near the eastern edge of the impoundment proximal to HD-2 (shown in gray on Table 4) that are being monitored relative to the 46 foot NAVD 88 design elevation, the 11 upgradient wells (DW-1, MW-602S, MW-602D, MW-603S, MW-603D, MW-605D, MW-605S, OW-1140D, OW-1140S, OW-1142D, and OW-1142S) had groundwater elevations ranging from

47.61 feet to 59.10 feet, all above the 46 foot NAVD 88 target elevation. In the five downgradient well (MW-604D, MW-604S, MW-705, MW-706, and OW-1124A), groundwater elevations ranged from 28.88 feet to 50.83 feet. Three of the downgradient wells (MW-604D, MW-705 and MW-706) had elevations below the 46 foot NAVD 88 target elevation.

Assuming no influence from precipitation or other sources of recharge, the water level decline in OU-3 as a result of water removed via HD-2 can be calculated with the following formula:

Change in groundwater level = water volume (ft3)/area (ft2) effective porosity (%)

For an effective porosity of 0.2% and an average flow rate of 2.21 gpm, the volume of water removed from OU-3 would equate to 2.18 feet of groundwater decline. As evidenced by the drought adjustment reported in CES’s water level analysis (CES, 2016c), the drawdown may be influenced periodically by extreme drought or high water conditions and not entirely attributable to HD-2. However, this precipitation influence is considered negligible due to steady state conditions over the lifetime of the drain and any appreciable drawdown should primarily be attributed to outflow from HD-2. A summary of data used to complete these calculations and the general water budget is included in Table 5.

Time series plots of groundwater elevations in individual wells and daily precipitation are shown on Charts 1 through 10. A combined time series plot of average daily transducer measurements of groundwater elevations for all deep tailings wells along HD-2 is shown on Chart 11.

Individual time series show groundwater elevations in most wells increased through the winter

4-3 and spring of 2015, showed a decline through December 2015, and have begun to show an increasing trend again. However, the overall variation in groundwater levels in deep tailings wells along HD-2 appears relatively unchanged when viewed together on Chart 11.

Precipitation data is included on these charts to assess the correlation of groundwater elevation and precipitation events. Overall, precipitation appears to have little influence other than possible annual seasonality on the long-term trends of groundwater elevations at each monitoring well. The background well, MW-610, is the only well that shows appreciable correlation to precipitation.

4.5 WATER QUALITY SAMPLING RESULTS

Comparison Criteria

The Maine DEP SWQC for Toxic Pollutants (Maine DEP, 2012), which is derived from the EPA NRWQC (EPA, 2016) with standards updated as recently as 2016, was used to evaluate the results of the water quality sampling. Criteria for the marine/saltwater chronic or criterion continuous concentration (CCC) were used, unless otherwise specified.

Field Parameter and Analytical Water Quality Results

Historical and current field parameters are summarized in Table 6, and historical and current analytical results are summarized in Table 7. The complete laboratory analytical report is included in Appendix E.

Field Parameters

At ADSD, AP-1, BCR, and DS-3, pH was general higher than historical measurements, and conductivity was generally consistent with historical measurements. ORP at DS-3 and BCR was lower than during the March 2017 inspection, but consistent with or lower than historical measurements. ORP at AP-1 and ADSD was higher than during the March 2017 inspection, the only historical data available for those locations. DO was consistent with historical measurements for all locations. Turbidity was lower at ADSD and higher at AP-1 than during the March 2017 inspection. Turbidity was higher than during recent sampling rounds at DS-3 and BCR, but below historical levels. Temperature was consistent with the expected seasonal fluctuations.

Analytical Results

For sample DS-3-0417, dissolved iron, manganese, and molybdenum, and total iron and manganese exceeded the EPA NRWQC. Other detected metals were below the EPA NRWQC and Maine DEP SWQC, where established. Sulfate, sulfide, and TSS were detected above laboratory reporting limits. The average of the three field measurements for DO was 0.80 mg/L, which is below the target DO for protection of all aquatic organisms (4.8 mg/L) and the limit for impacts to juvenile and adult survival (2.3 mg/L). Results were consistent with historical concentrations.

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For sample BCR-0417, dissolved iron and manganese, and total iron and manganese exceeded the EPA NRWQC. Other detected metals were below the EPA NRWQC and Maine DEP SWQC, where established. Sulfate, total sulfide, and TSS were detected above laboratory reporting limits. The average DO measurement was 3.41 mg/L, below the target DO for protection of all aquatic organisms (4.8 mg/L), and above the limit for impacts to juvenile and adult survival (2.3 mg/L).

For sample AP-1-0417, dissolved manganese, and total iron and manganese exceeded the EPA NRWQC. Other detected metals were below the EPA NRWQC and Maine DEP SWQC, where established. Sulfate, total sulfide, and TSS were detected above laboratory reporting limits. The average DO measurement was 2.64 mg/L, below the target DO for protection of all aquatic organisms (4.8 mg/L), and above the limit for impacts to juvenile and adult survival (2.3 mg/L).

For sample ADSD-0417, dissolved copper, zinc, and manganese, and total iron and manganese exceeded the EPA NRWQC and Maine DEP SWQC (established for copper and zinc). Other detected metals were below the EPA NRWQC and Maine DEP SWQC, where established.

Sulfate and TSS were detected above laboratory reporting limits, and total sulfide was below laboratory reporting limits. The average DO measurement was 14.84 mg/L, above the target DO for protection of all aquatic organisms (4.8 mg/L), and above the limit for impacts to juvenile and adult survival (2.3 mg/L). Results were compared to sample results for effluent flowing through the bioreactor, and copper and zinc concentration were higher than the bioreactor system effluent. Iron was also higher than the system effluent but lower than the DS-3 influent.

Maine DEP Basic Data Review Checklist

A completed Maine DEP Basic Data Review Checklist is included in Appendix F.

Data reviewed for this project are usable for making project decisions and are considered representative with regard to the sample design. Data qualified as estimated were evaluated relative to the respective regulatory criteria and the data quality objectives. Generally, these qualifications are not expected to alter conclusions drawn from the data.

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5. CONCLUSIONS SUMMARY

Credere makes the following conclusions with regard to the objectives in Section 2.1:

The Site inspection performed on April 5 and 6, 2017, did not identify any evidence of vandalism or degradation of the Site.

Ice removal was performed at Aeration Pond #2 to facilitate flow.

Transducer settings were adjusted to measure depth to water in all monitoring wells, rather than the depth of the transducer below water.

A flow rate of 2.08 gpm was measured flowing into DS-3, which is consistent with historical flow rates. The flow rate of the bioreactor discharge (BCR) was measured at

1.50 gpm, which is generally higher than historical flow rates, but similar to the flow rates observed during the January and March 2017 inspections. The flow rate at the Aeration Pond #1 discharge point was measured at 0.75 gpm, lower than the March 2017 flow rate. The Aeration Pond #2 (AP-2) discharge could not be measured due to ice buildup preventing a cohesive, measureable flow, and the combined aeration pond and stormwater ditch (ADSD) was observed for relative flow (significant stormwater flow, with some cloudy aeration pond discharge observed flowing into the ditch).

Based on the updated average flow rate of 2.21 gpm into DS-3, approximately 1,565,741 gallons of groundwater have discharged from HD-2 between December 1, 2015, and April 6, 2017, which theoretically equates to a 2.18-foot decrease in the groundwater elevation within the tailings impoundment, if all other influences are considered negligible (e.g., precipitation, drought, recharge, seepage). This calculated drawdown is not consistent with the average Site-wide elevation decrease of 0.72 feet as calculated from measured groundwater elevations, but the discrepancy is lower than in previous inspections.

Time series data for monitoring wells along the eastern edge of the impoundment proximal to HD-2 show seasonal variation, but no clear trend in increasing or declining groundwater elevation. The historical elevation data for each well is typically within a ±2-foot range. Of the 14 wells being monitored to evaluate the influence of HD-2 on decreasing groundwater elevation to the 46-foot NAVD 88 design target, only three of the wells have groundwater elevations consistently below the 46 feet NAVD 88 design target.

Water quality samples and field water quality parameters were collected at the established DS-3, BCR, AP-2, and ADSD sampling points. Water quality sample and field water quality parameter results were generally consistent with historical observations.

Water quality results for ADSD contained dissolved antimony, cadmium, cobalt, copper, lead, manganese, molybdenum, nickel, and zinc at higher concentration than that flowing through the bioreactor system. These elevated concentrations can likely be attributed to

5-2 stormwater flow that receives leachate from the waste rock pile to the north (waste rock pile 3) and possibly from Seep-508.

Based on these conclusions, the HD-2 drain is flowing at a rate consistent with historical flows and shows no indication of requiring back flushing or other maintenance. While the observed flow rate is greater than the flow predicted in the 30% Design Submission, Basis of Design Report (AMEC, 2013), the average groundwater elevation in the eastern impoundment has not achieved the corresponding drawdown predicted by the groundwater model for the selected alternative. There was a Site-wide increase in groundwater levels since the March 2017 Site inspection. It appears likely that the groundwater elevations exhibit seasonal fluctuations and this increase is part of the seasonal trend. Based on the current long-term monitoring data, the flow from HD-2 does not appear to be a significant influence on lowering groundwater levels in the OU-3 impoundment.

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6. REFERENCES

AMEC, 2013. 30% Design Submission, Basis of Design Report, Callahan Mine Superfund Site, Brooksville, Maine. Prepared for the Maine Department of Transportation (DOT).

Prepared by AMEC Environment and Infrastructure, Inc., Dated April 5, 2013.

AMEC, 2014. OU3 Draft Final Remedial Design Basis of Design Report, Callahan Mine Superfund Site, Brooksville, Maine. Prepared for Maine Department of Transportation (DOT), prepared by AMEC Environment and Infrastructure, Inc., Dated December 5, 2014.

Buchman, M. F., 2008. NOAA Screening Quick Reference Tables, NOAA OR&R Report 08-1.

Prepared by Seattle, WA, Office of Response and Restoration Division, National Oceanic and Atmospheric Administration, 34 pages: dated 2008.

CENAE, 2016. Revised Performance Work Statement Horizontal Drain Performance Assessment and Site Inspections, Callahan Mine Superfund Site, CERCLIS ID MED980524128, Brooksville, Maine. Prepared by CENAE, Dated July 12, 2016.

CES, 2016a. Remedial Action Completion Report for Phase I, Operable Unit 3, Callahan Mine Superfund Site, Brooksville, Maine. Prepared for Maine DEP, prepared by CES, Inc., Dated March 2016.

CES, 2016b. Callahan Mine Performance Monitoring Report. Prepared for Maine DEP, by CES, Inc., Dated August 31, 2016, October 6, 2016, and November 14, 2016.

CES, 2016c. Callahan Mine Final Water Level Analysis. Prepared for Maine DEP, prepared by CES, Inc., Dated December 19, 2016.

Credere, 2016a. Sampling and Analysis Plan/Quality Assurance Project Plan, Callahan Mine Superfund Site, Operable Unit 3 – TP-1 Performance Assessment. Prepared for USACE CENAE, prepared by Credere Associates, LLC, Dated November 29, 2016.

EPA, 1986. Quality Criteria for Water 1986. EPA-440/5-86-001: dated May 1, 1986.

EPA, 2000. Ambient Aquatic Life Water Quality Criteria for DO (Saltwater): Cape Cod to Cape Hatteras. EPA-822-R-00-012: dated November 2000

EPA, 2016. National Recommended Water Quality Criteria – Aquatic Life Criteria Tables:

updated 2016: https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table

Maine DEP, 2012. Chapter 584: Surface Water Quality Criteria for Toxic Pollutants. July 29, 2012.

FIGURES

T:\Data\ME\Town\Old Town\13001213 - Jefferson Street School

PROJECT:

DATE:

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DRAWN BY: 09/09/2016

16001352

CALLAHAN MINE

BROOKSVILLE, MAINE

BROOKSVILLE

776 MAIN STREET

WESTBROOK, MAINE

Tel. 207.828.1272 Fax 207.887.1051

WWW.CREDERELLC.COM

Credere Associates, LLC

FIGURE 1

SITE LOCATION PLAN

ASD

SCG

pCREDERE

SITE LOCATION

Topographic Map Data Sources: Esri, HERE, DeLorme, TomTom, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community

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CALLAHAN MINE SUPERFUND SITE BROOKSVILLE, MAINE

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US ARMY CORPS OF ENGINEERS 696 VIRGINIA ROAD CONCORD, MASSACHUSETTS

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DATE: 04/14/1704/14/17

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PROJECT: 1600135216001352

AutoCAD SHX Text FIGURE 3 - GROUNDWATER CONTOURS THROUGH SHALLOW GROUNDWATER CONTOURS THROUGH SHALLOW TAILINGS WELLS (04/07/17) CALLAHAN MINE SUPERFUND SITE, BROOKSVILLE, MAINE

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US ARMY CORPS OF ENGINEERS 696 VIRGINIA ROAD CONCORD, MASSACHUSETTS

AutoCAD SHX Text 776 MAIN STREET WESTBROOK, MAINE 04092 FAX: 207.887.1051 TEL: 207.828.1272 WWW.CREDERELLC.COM

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PROJECT: 1600135216001352

AutoCAD SHX Text FIGURE 4 - GROUNDWATER CONTOURS THROUGH DEEP GROUNDWATER CONTOURS THROUGH DEEP TAILINGS WELLS (04/06/17) CALLAHAN MINE SUPERFUND SITE, BROOKSVILLE, MAINE

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US ARMY CORPS OF ENGINEERS 696 VIRGINIA ROAD CONCORD, MASSACHUSETTS

AutoCAD SHX Text 776 MAIN STREET WESTBROOK, MAINE 04092 FAX: 207.887.1051 TEL: 207.828.1272 WWW.CREDERELLC.COM

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TABLES

Table 1 Summary of Monitoring Wells for Gauging and Transducer Download

Callahan Mine Superfund Site, Operable Unit 3 - TP 1 Performance Assessment Brooksville, Maine

Monitoring Wells (MW) for Gauging Monitoring Wells for Transducer Download and Manual Gauging

MW-603D MW-602S

MW-603S MW-602D

MW-605S MW-605D

MW-705 DW-1

MW-706 MW-604S

MW-707 MW-604D

OW-1131 OW-1140D

OW-1132 OW-1124A

OW-1140S OW-1142D

OW-1141D MW-610

OW-1141S

OW-1142S

Table 2 Water Quality Sample Summary

Callahan Mine Superfund Site, Operable Unit 3 - TP 1 Performance Assessment Brooksville, Maine

Sample Location Sample ID Justification Proposed Analyses1

Discharge Structure 3 (Compost Bioreactor

Influent)

DS-3

DS-30

Characterize raw water from the horizontal drain HD-2 prior to treatment

Compost Bioreactor Effluent

BCR*

Document level of treatment from bioreactor prior to aeration

Aeration Pond 1 Effluent**

AP-1**

Combined Aeration Ditch and Stormwater Ditch Combined Flow

ADSD

Notes:

1 – Dissolved metals are monitored to assess the metals concentrations bioavailable to aquatic biota.

DS-30 – Blind field duplicate sample

* - Location where matrix spike/matrix spike duplicate (MS/MSD) volume was collected for all analyses.

** - Discharge was observed from AP-2, but a cohesive flow could not be obtained for sampling. Therefore, samples were collected from the Aeration Pond 1 effluent.

Dissolved Metals1 via EPA Method 6020A Sulfate via EPA Method 300.0

Total Sulfide via EPA Method SM4500S2-D Total Iron and Manganese via EPA Method 6020A Total Suspended Solids via EPA Method SM2540D

DO via EPA Method 360.1 Confirm effluent from treatment system meets ambient water quality criteria prior to discharge (post-treatment water characterization)

Table 3 Summary of Measured HD-2 and Bioreactor Flow Rates

Callahan Mine Superfund Site, Operable Unit 3 - TP 1 Performance Assessment Brooksville, Maine

Yes No 8/11/2016 X 1.62 1.59 1.62 1.61

10/6/2016 X NM NM NM NM

11/14/2016 X 1.8345 1.8219 1.8474 1.8346

12/14/2016 X 1.188 1.132 1.188 1.169

1/10/2017 X 2.26 2.04 2.08 2.13

2/7/2017…