B.08 GFI JB CHS PBR_FL073 (SWMU 73)_Draft CMI YR2.pdf

DRAFT

CORRECTIVE MEASURES IMPLEMENTATION YEAR 2

ANNUAL REPORT

Solid Waste Management Unit 73 (FL073)

PERFORMANCE-BASED REMEDIATION

Joint Base Charleston Weapons

SOUTH CAROLINA

Contract FA8903-15-C-0016 October 2022 Revision 00

Prepared for:

AFCEC/CZRE

US Air Force Civil Engineer Center 772nd ESS/PKS

2261 Hughes Avenue, Suite 155 JBSA Lackland, TX 78236-9853

Prepared by:

Tetra Tech, Inc.

661 Andersen Drive

Foster Plaza 7 Pittsburgh, Pennsylvania,15220

(412) 921-7090

With Teaming Partners:

Corrective Measures Implementation Year 2 Annual Report

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 iii BWJ140078

TABLE OF CONTENTS

TABLE OF CONTENTS .............................................................................................................. III ACRONYMS AND ABBREVIATIONS ......................................................................................... V EXECUTIVE SUMMARY ............................................................................................................. VI

1.0 INTRODUCTION

1.1 Site Description

1.1.1 Current and Future Land Use

1.2 Previous Investigations and Cleanup Actions

1.2.1 Interim Measures (IM)/Confirmatory Sampling (CS) at SWMU Sites

1.2.2 RFI for IM Sites

1.2.3 Interim Groundwater Monitoring

1.2.4 Initial Corrective Measures Study

1.2.5 2012 Groundwater Monitoring

1.2.6 2016 CMS Investigation

1.2.7 2020 Interim Measure Approach

1.3 Interim Measure Approach and Purpose

2.0 CMI YEAR 2 ACTIVITIES

2.1 Performance Monitoring Groundwater Sampling Events

2.2 Water Level Measurements

2.3 Groundwater Flow Direction

2.4 Land Use Control Inspection

2.5 Investigation-Derived Waste

3.0 PERFORMANCE MONITORING ANALYTICAL RESULTS

3.1 Nature and Extent of Contamination

3.2 Natural Attenuation and Geochemical Parameters

3.3 Data Quality Evaluation

4.0 RECOMMENDATIONS

5.0 REFERENCES

FIGURES ................................................................................................................................... 5-1 TABLES ..................................................................................................................................... 5-2 APPENDIX A FIELD DOCUMENTATION ................................................................................ 5-3 APPENDIX B LABORATORY DATA REPORTS .................................................................... 5-4 (ON ATTACHED CD) ................................................................................................................ 5-4 APPENDIX C DATA VALIDATION REPORTS ........................................................................ 5-5 (ON ATTACHED CD) ................................................................................................................ 5-5 APPENDIX D LUC INSPECTION CHECKLIST ....................................................................... 5-6 APPENDIX E WASTE MANAGEMENT DOCUMENTATION .................................................. 5-7

List of Figures

Figure 1-1 Location Map

Figure 1-2 Site Location Map

Figure 1-3 Site Map

Figure 2-1 Baseline and Corrective Measures Implementation Groundwater Sampling Results

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Contract FA8903-15-C-0016 iv BWJ140078

Figure 2-2 Groundwater Elevation Map – June 21, 2022

List of Tables

Table 2-1 Summary of Groundwater Quality Parameter Data

Table 2-2 Analytical Results in Groundwater Samples and Comparison to Media Cleanup Standards

Table 2-3 Well Construction Information and Groundwater Level Measurements

List of Appendices

Appendix A Field Documentation

Appendix B Laboratory Data Reports (on attached CD)

Appendix C Data Validation Reports (on attached CD)

Appendix D LUC Inspection Checklist

Appendix E Waste Management Documentation – to be provided

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ACRONYMS AND ABBREVIATIONS

°F degrees Fahrenheit µg/L microgram per liter

AFCEC Air Force Civil Engineer Center amsl above mean sea level bgs below ground surface

CM Corrective Measures

CMI Corrective Measures Implementation

CMO corrective measures objective

CMS Corrective Measures Study

COC chemical of concern

CS Confirmatory Sampling

DL Detection Limit

DO dissolved oxygen ft foot/feet

IDW investigation-derived waste

IM Interim Measures

JBC Joint Base Charleston lb Pound

LOD Limit of Detection

LOQ Limit of Quantitation

LTM long-term monitoring

LUC Land Use Control

MCL Maximum Contaminant Level

MCS media cleanup standard mg/kg milligram per kilogram mg/L milligram per liter

MNA Monitored Natural Attenuation

MS matrix spike

MSD matrix spike duplicate mV millivolt

ORC-A® Advanced Oxygen Releasing Compound®

ORP oxidation-reduction potential ppt parts per thousand

RA-O remedial action operation

RCRA Resource Conservation and Recovery Act

RFI RCRA Facility Investigation

SCDHEC South Carolina Department of Health and Environmental Control

SWMU Solid Waste Management Unit

TAL Target Analyte List

TOC Total Organic Carbon

UFP-QAPP .. Uniform Federal Policy-Quality Assurance Project Plan

WP Work Plan

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Contract FA8903-15-C-0016 vi BWJ140078

EXECUTIVE SUMMARY

Tetra Tech has prepared this Corrective Measures Implementation (CMI) Year 2 Report to document the Corrective Measures (CM) completed at Solid Waste Management Unit (SWMU) 73 (FL073) at Joint Base Charleston (JBC) Weapons located in Charleston, South Carolina. This work is being performed under Contract FA8903-15-C-0016 for the United States Air Force Civil Engineer Center (AFCEC) to satisfy the requirements of the Resource Conservation and Recovery Act (RCRA) Hazardous Waste Permit No. SC8 170 022 620 issued to JBC Weapons by the South Carolina Department of Health and Environmental Control (SCDHEC).

SWMU 73 (FL073) - South Annex Building 3440, Battery Shop Septic Tank is located in the southcentral portion of the base within the South Annex. The area around Building 3440 includes manicured flat grass lawns, and south of Building 3440 the ground surface slopes down with a change in elevation of approximately 13 feet (ft) towards the intersection of Woods Avenue and 7th Street. Building 3440 was constructed in 1941 as an “Inert Storage Warehouse” but by 1970 was being used as “Battery Storage, Administrative, and Battery Shop”. It is unknown when the building began to be used for this latter purpose. The base point of contact at the time the RCRA Facility Investigation (RFI) was completed, Barry Lewis, speculated that battery storage became a need for the depot when its mission changed to transportation in approximately 1952. The base sanitary sewer map dated September 1, 1970 showed a septic tank at the southern end of Building 3440 labeled “43”. A construction drawing for the building could not be located. The septic tank was shown to be a 1,000-gallon concrete septic tank similar to others used at the base. The Building 3440 tank is the perceived source of contamination at SWMU 73 (FL073).

In accordance with the CMI Work Plan (Tetra Tech, 2019), a CM was implemented of the proposed remedial action which included excavation, removal and off-site disposal of soil with contaminants at concentrations greater than Media Cleanup Standards (arsenic) in the subsurface soil to 4 feet below ground surface (bgs), in situ chemical oxidation using an oxygen release compound in the source area to immobilize groundwater contaminants (arsenic and iron), and a performance monitoring baseline event for the rest of the plume in May and June 2020 (Tetra Tech, 2020). This report describes Year 2 of the remedial action operation (RA-O) and the performance monitoring program.

Joint Base Charleston Weapons, South Carolina

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1.0 INTRODUCTION

Tetra Tech prepared this Corrective Measures Implementation (CMI) Year 2 Annual Report for Solid Waste Management Unit (SWMU) 73 (FL073) – South Annex Building 3440, Battery Shop Septic Tank, at Joint Base Charleston (JBC) Weapons in Charleston, South Carolina. This work was performed under Contract FA8903-15-C-0016 for the United States Air Force Civil Engineer Center (AFCEC) to fulfill the requirements of the Resource Conservation and Recovery Act (RCRA) Hazardous Waste Permit No. SC8 170 022 620 issued to JBC Weapons by the South Carolina Department of Health and Environmental Control (SCDHEC).

The field activities associated with the CMI Year 2 Annual Report include groundwater sampling as part of the remedial action operation (RA-O) and performance monitoring program, and land use control (LUC) monitoring. This work was conducted in accordance with the Basewide Groundwater, Surface Water, and Land Use Control Monitoring Uniform Federal Policy – Quality Assurance Project Plan (UFP-QAPP) (Bay West, 2016a).

1.1 Site Description

JBC Weapons is located 10 miles north of Charleston, South Carolina, approximately 16 miles inland from the Atlantic Ocean. JBC Weapons is situated in two counties, Berkeley and Charleston, and occupies 16,868 acres. A location map is provided as Figure 1-1.

JBC Weapons is situated in a temperate to subtropical climate with mild winters, hot and humid summers, and significant rainfall all year long. Average daily temperatures in the summer range from 78 degrees Fahrenheit (°F) to 82°F, with daily highs averaging between 87°F to 91°F.

SWMU 73 (FL073) - South Annex Building 3440, Battery Shop Septic Tank is located in the southcentral portion of the base within the South Annex (see Figures 1-2 and 1-3). The area around Building 3440 includes manicured flat grass lawns, and south of Building 3440 the ground surface slopes down with a change in elevation of approximately 13 feet (ft) towards the intersection of Woods Avenue and 7th Street. Building 3440 was constructed in 1941 as an “Inert Storage Warehouse” but by 1970 was being used as “Battery Storage, Administrative, and Battery Shop”. It is unknown when the building began to be used for this latter purpose. The base point of contact at the time the RCRA Facility Investigation (RFI) (Tetra Tech, 2011a) was completed, Barry Lewis, speculated that battery storage became a need for the depot when its mission changed to transportation in approximately 1952. The base sanitary sewer map dated September 1, 1970 showed a septic tank at the southern end of Building 3440 labeled “43”. The Building 3440 tank is the perceived source of contamination at SWMU 73 (FL073) and the March 2020 investigation conducted as part of this CMI confirmed its existence at that location.

1.1.1 Current and Future Land Use

JBC Weapons is an active military/industrial area and is expected to remain active for the foreseeable future. SWMU 73 (FL073) is located in the South Annex in an industrial and developed area of the base and future land use at the site is assumed to be consistent with current use, with no reasonable expectation of future residential use.

1.2 Previous Investigations and Cleanup Actions

The following sections highlight historical reports and environmental investigations completed for

SWMU 73 (FL073).

1.2.1 Interim Measures (IM)/Confirmatory Sampling (CS) at SWMU Sites

TolTest conducted IM field activities in 2005 at 11 sites (TolTest, 2005). At SWMU 73 (FL073), 10 test trenches were excavated but the septic tank was not located; soil samples were collected

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Contract FA8903-15-C-0016 2 BWJ140078 in the area of the suspected septic tank near the building’s loading area; and installation of temporary monitoring wells was planned but was not completed because the septic tank could not be located. Because the septic tank could not be located, TolTest performed a dye tracer test with Navy personnel and confirmed that Building 3440 is connected to the base’s sanitary system.

It was recommended that an RFI be implemented at SWMU 73 (FL073) to determine the nature and extent of surface contamination adjacent to the southwestern end of Building 3440 where impacts from the battery shop were possible; and to characterize the shallow aquifer in the area of Building 3440 associated with the septic tank itself. These results are presented in the Data Package Interim Measures Sites (Tetra Tech, 2006).

1.2.2 RFI for IM Sites

Soil and groundwater samples were collected in 2009 during the RFI at SWMU 73 (FL073), with criteria exceedances noted in both media (Tetra Tech, 2011a). Chromium was the only contributor to estimated unacceptable risk in soil; with an exceedance occurring at only one location. The basis for the risk was the assumption that chromium is present in the more toxic hexavalent form rather than the trivalent form. Therefore, the RFI recommended either a hot spot removal or resampling of soil for hexavalent chromium at this location. Metals were detected in all groundwater samples, arsenic and lead were the only metals detected at concentrations greater than screening criteria and facility background levels. Groundwater monitoring for arsenic and lead, and additional investigation to delineate the arsenic and lead plume were recommended.

1.2.3 Interim Groundwater Monitoring

Eight permanent monitoring wells (73MW01 through 73MW06, 73MW09, and 73MW10) were installed in 2011 as part of the Interim Groundwater Monitoring investigation (Tetra Tech, 2011b).

Proposed monitoring wells 73MW07 and 73MW08 were not installed during this investigation because of construction.

Arsenic was detected in groundwater at five monitoring wells and lead was detected in groundwater at two monitoring wells; however, only two groundwater samples had low-level arsenic concentrations in exceedance of the screening criterion (73MW02 and 73MW03).

Although most of the SWMU 73 (FL073) wells were installed as sentinel wells, arsenic and lead results during the interim monitoring event at two wells within the plume were significantly less than concentrations measured during the RFI. The source of arsenic contamination was unknown, but a continuing upgradient source was ruled out based on analytical results from upgradient well 73MW01. Because arsenic was detected at monitoring well location 73MW03 at a concentration that exceeded the screening criterion and because 73MW03 was the most downgradient well from the source area, the plume could not be delineated. It was recommended that the originally planned monitoring wells 73MW07 and 73MW08 be installed downgradient of 73MW03 to delineate the plume, and that a long-term monitoring plan be prepared for SWMU 73 (FL073).

1.2.4 Initial Corrective Measures Study

A Corrective Measures Study (CMS) was completed in 2011 to evaluate remedial alternatives for soil and groundwater (Tetra Tech, 2011c). Based on evaluations completed as part of this study, excavation and removal of contaminated surface soil, LUCs for groundwater, and long-term monitoring (LTM) of groundwater were chosen as the recommended remedial alternatives.

SCDHEC provided comments on the CMS Report in 2012. SCDHEC commented that a better discussion about the location of the septic tank needed to be provided, along with evidence to support the rationale that there may be an upgradient source. SCDHEC also inquired whether an investigation of another potential source had been conducted since the septic tank had not been located at the time of the completion of the initial CMS. SCDHEC also commented that the SWMU boundary may need to be modified. SCDHEC conditionally approved the CMS Report and

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Contract FA8903-15-C-0016 3 BWJ140078 response to comments in 2013 with the requirement to submit a CMS Work Plan (WP). None of the corrective measures identified in the conditionally approved 2011 CMS were implemented pending completion of the required additional data collection.

1.2.5 2012 Groundwater Monitoring

Groundwater monitoring was conducted in 2012 (TEC-BSC Joint Venture, 2013). Lead was detected in four monitoring wells at concentrations less than the screening criterion. Arsenic was detected in three monitoring wells, but only at concentrations greater than the Maximum Contaminant Level (MCL) in two monitoring wells (73MW02 and 73MW03). The maximum arsenic groundwater concentration measured in 2012 was 34.8 micrograms per liter (µg/L).

1.2.6 2016 CMS Investigation

Based on comments received from SCDHEC on the 2011 CMS requiring additional investigation at SWMU 73 (FL073), Tetra Tech developed a CMS WP to describe the plan for collecting additional data. The additional investigation was conducted in October 2016. One permanent groundwater monitoring well was installed (73MW07) and a round of groundwater samples was collected from all monitoring wells present at SWMU 73 (FL073) to better define the groundwater plume and to evaluate groundwater contamination. The groundwater samples were analyzed for target analyte list (TAL) metals and natural attenuation parameters. Also, one soil sample was collected at the location of the RFI chromium exceedance for analysis of total and hexavalent chromium, pH, and oxidation-reduction potential (ORP) to determine if hexavalent chromium was present in the soil.

Additionally, an intrusive investigation was conducted in the area of the septic tank and four soil samples were collected near the septic tank. One temporary groundwater monitoring well was also installed (73TW16) in a soil boring adjacent to and just downgradient of the septic tank. The soil samples collected near the septic tank and the groundwater sample collected from the temporary monitoring well were analyzed for TAL metals. The field work was conducted and completed in accordance with the Basewide Groundwater, Surface Water, and Land Use Control Monitoring Uniform Federal Policy-Quality Assurance Project Plan (UFP-QAPP) and Basewide Soil Sampling and Analysis UFP-QAPP (Bay West, 2016a and 2016b) and the CMS Work Plan for SWMU 73 (Tetra Tech, 2016). There were no deviations from the Basewide UFP-QAPPs or the CMS WP.

The underground septic tank discovered in 2016 during utility work was located during the CMS Investigation based on photographs and measurements taken by JBC Weapons personnel. An intrusive investigation was then conducted to locate and determine the approximate depth and size of the underground tank. A hand auger was advanced until refusal was encountered. When refusal was encountered, and field personnel were confident that the top of the septic tank was reached, step outs were conducted in 2-foot intervals in four directions and the hand auger was advanced again. This step out procedure was conducted outwards three times from the original point of refusal until refusal was no longer encountered. Based on the results of the 2016 intrusive investigation, the septic tank appeared to be approximately 4 ft wide by 8 ft long with the depth to the top of the septic tank ranging from approximately 10 to 14 inches below ground surface (bgs).

No piping associated with the tank was located. Soil samples 73SB11, 73SB12, 73SB13, and 73SB14 were collected at approximately 2 ft from each corner of the tank. Sample depth intervals ranged from 1 ft bgs to approximately 2.5 ft bgs as the water table was encountered at a depth of approximately 2.5 to 2.75 ft bgs in this area. Additional details about the sampling efforts can be found in the CMS Report (Tetra Tech, 2017).

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1.2.7 2020 Interim Measure Approach

The corrective actions selected in the SWMU 73 (FL073) CMS Report and Statement of Basis (Tetra Tech, 2018) were the excavation and off-site disposal of the septic tank and soil; and in situ chemical oxidation, monitored natural attenuation (MNA), and LUCs for groundwater. A CMI WP was prepared by Tetra Tech in May 2019 (Tetra Tech, 2019). In accordance with the CMI WP, contaminated soil at SWMU 73 (FL073) was excavated and transported off-site for disposal, though the total volume estimated in the CMI WP was not able to be removed during excavation due to the proximity of an electrical transformer. The septic tank also remains in place due to an electrical transformer which had been installed south of Building 3440 (within 2 feet of the septic tank) at a location that precluded the safe removal of the tank without installation of shoring. As a result, a decision was made to leave the tank in place until the plan for its safe removal could be developed. The tank contents were removed and containerized while soil adjacent to the tank was excavated and disposed offsite. The soil excavation at SWMU 73 (FL073) extended to 4 ft bgs within the southern and western septic tank areas.

In accordance with the CMI WP, injections of Advanced Oxygen Releasing Compound® (ORC- A®) (made by Regenesis) to promote precipitation of arsenic and iron from groundwater were applied at SWMU 73 (FL073) by supplying a source of dissolved oxygen to the aquifer. A slurry comprised of 230 pounds (lbs) ORC-A® and 65 gallons of water was injected through depths of 20 to 4 ft bgs at 99 points (borings) across the site. The borings were spaced approximately 10 ft apart. The purpose of the injections was to reduce the concentrations of arsenic and iron in the groundwater to below their media cleanup standards (MCSs) of 10 µg/L and 26,900 µg/L, respectively. Additional details about the soil excavation and ORC-A® injections can be found in the approved CMI Completion Report (Tetra Tech, 2020).

1.3 Interim Measure Approach and Purpose

The Corrective Measure Objectives (CMOs) listed below were developed in the site-specific CMS Report (Tetra Tech, 2017) and were developed to ensure that corrective actions taken at SWMU 73 (FL073) sufficiently reduced and/or eliminated risks to human health and the environment. The CMOs for SWMU 73 (FL073) are:

• Prevent unacceptable risks to potential future residential receptors from exposure to arsenic in soil;

• Attain MCSs for soil;

• Prevent unacceptable risks to potential future residential receptors from exposure to arsenic and iron in groundwater; and

• Attain MCSs for groundwater.

The MCSs for soil and groundwater at SWMU 73 (FL073) are:

Soil

• Arsenic: 14.1 milligram per kilogram (mg/kg);

Groundwater

• Arsenic: 10 µg/L; and

• Iron: 26,900 µg/L.

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2.0 CMI YEAR 2 ACTIVITIES

The groundwater monitoring for the baseline event was conducted in May 2020, the CMI implementation actions of the septic tank investigation, soil excavation, and ORC-A® injections occurred in May through June 2020. The Year 1 quarterly performance monitoring began September 18, 2020 with events in November 19, 2020, March 9, 2020, and the fourth event occurring June 10 and July 15, 2021 This section presents the details associated with CMI Year 2 field activities including annual groundwater sampling as part of the RA-O and performance monitoring program, and LUC monitoring at SWMU 73 (FL073).

The Year 2 events discussed in this report were completed in June 2022 and consisted of the completion of the following activities:

• Collection of RA-O and performance monitoring program groundwater samples on June 21, 2022; and

• Completion of the LUC Inspection on June 21, 2022; and

• Synoptic water level measurements collected on June 21, 2022.

Each of these field activities are discussed in the sections below. All field logs are contained in Appendix A.

2.1 Performance Monitoring Groundwater Sampling Events

In accordance with the CMI Work Plan (Tetra Tech, 2019), monitoring wells 73MW02, 73MW03, 73MW07, and 73MW11 were sampled as part of the second annual sampling event following the remedial action.

Groundwater samples were collected on June 21, 2022 using low-flow sampling techniques described in Worksheet #14 under Groundwater Sampling section of the Basewide Groundwater, Surface Water, and Land Use Control Monitoring UFP-QAPP (Bay West, 2016a). The performance and RA-O monitoring parameters include arsenic and iron, as well as MNA and water quality parameters. Water quality parameters were measured every 3 to 5 minutes during purging using a water quality meter with an inline flow-through cell. Water quality parameters included dissolved oxygen (DO), specific conductivity, pH, turbidity, temperature, salinity, ORP and ferrous iron. Purging was considered complete when parameters were stable for at least three consecutive readings within the limits defined in the UFP-QAPP. Stable field parameters are included in Table 2-1. The groundwater samples were analyzed for arsenic, iron, sulfate, sulfide and Total Organic Carbon (TOC). Groundwater samples were analyzed by Pace Analytical Gulf Coast via analytical test method 6020B (SW-846) for arsenic and iron, method 9056A (SW-

846) for sulfate, method 9034 (SW-846) for sulfide and method 9060A (SW-846) for TOC. Pace Analytical Gulf Coast is a current Department of Defense Environmental Laboratory Accreditation Program and State of South Carolina accredited laboratory. The parameters, analytical methods, applicable MCSs and sampling results from the baseline, Year 1, and Year 2 events are listed in Table 2-2.

A matrix spike/matrix spike duplicate (MS/MSD) sample was collected from 73MW02 during the June 21, 2022 sampling event and a duplicate sample was collected from 73MW11. Groundwater sampling forms are included in Appendix A.

2.2 Water Level Measurements

A groundwater level measurement was collected from each monitoring well located at SWMU 73 (FL073). Groundwater level measurements were collected on June 21, 2022. Water level measurements were made to the nearest 0.01 foot using an electronic water level meter. The

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Contract FA8903-15-C-0016 6 BWJ140078 water level meter was decontaminated between monitoring wells to avoid cross-contamination.

Monitoring well construction details and groundwater levels are included in Table 2-3. The monitoring well gauging sheet is included in Appendix A.

2.3 Groundwater Flow Direction

A groundwater elevation map for the June 21, 2022 synoptic water level event is included as Figure 2-2. During the June 2022 event, groundwater flowed primarily to the south by southeast.

The June 2022 groundwater flow pattern is consistent with previous groundwater monitoring results and with data collected during the 2020 baseline event (Tetra Tech, 2020) and Year 1 CMI event (Tetra Tech, 2022).

2.4 Land Use Control Inspection

A LUC inspection was completed on June 21, 2022. The LUC for SWMU 73 (FL073) includes prohibition of the installation of wells for potable water uses within the surficial groundwater aquifer. No issues requiring further action were identified during the LUC inspection. The June 2022 LUC inspection checklist is included as Appendix D.

2.5 Investigation-Derived Waste

Investigation-derived waste (IDW) generated during the field program included groundwater from well purging and decontamination liquids. The IDW was collected and containerized in a 55-gallon drum. The IDW liquid from SWMU 73 (FL073) was combined with that from SWMU 68 (ID068) and AOC G (ST042) as groundwater sampling was conducted concurrently at the three SWMUs.

The drum was transported to the Hazardous Waste Storage Area at JBC Weapons, for temporary storage and is awaiting disposal. Disposal documentation will be provided in Appendix E at a later date. Solid waste generated during sampling activities (i.e., personal protective equipment such as sampling gloves and disposable groundwater sample tubing) was collected and disposed of as general refuse in a dumpster.

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3.0 PERFORMANCE MONITORING ANALYTICAL RESULTS

3.1 Nature and Extent of Contamination

Arsenic and iron concentrations exceeded their respective MCSs in one or more samples collected at SWMU 73 (FL073) during Year 2 performance monitoring. Analytical results in groundwater are summarized in Table 2-2 and shown on Figure 2-2. The full laboratory reports are included in Appendix B.

Arsenic was detected at concentrations exceeding the 10 µg/L MCS in three of the four monitoring wells sampled during the Year 2 sampling event. Monitoring well 73MW03 had an arsenic concentration less than the 10 µg/L MCS. The highest arsenic concentration was identified in 73MW11, located in the groundwater source area, at 1,560 µg/L during the Year 2 sampling event.

Arsenic was detected at 96.4 µg/L in 73MW07, which is located near the downgradient edge of the arsenic in groundwater plume.

Iron was detected at concentrations exceeding the 26,900 µg/L MCS in 73MW02 and 77MW11, each located downgradient of the source area during the Year 2 sampling event (55,400 µg/L and 47,900 µg/L, respectively).

3.2 Natural Attenuation and Geochemical Parameters

Several measurements were made to evaluate the geochemistry of the groundwater and its effect on natural attenuation of the chemicals of concern (COC) in accordance with the CMI Work Plan (Tetra Tech, 2019). The geochemical parameters are included on Table 2-1 as field parameters.

Geochemistry parameters were measured to evaluate how they relate to both conditions for biological activity and inorganic COC concentrations. Ferrous iron field measurements were not collected from 73MW02 and 73MW07 in error. The ferrous iron 73MW11 concentration 2.66 milligrams per liter (mg/L) in June 2022, which is similar to the 2020 baseline sampling event and the 2021 annual sampling event. Monitoring well 73MW03 had a ferrous iron concentration of 3.3 mg/L during the June 2022 sampling event.

At 73MW11 in the groundwater source area, the ORP results were positive indicating oxidizing and conditions favorable to aerobic activity (44 millivolts [mV] in the June 2021 Year 1 annual sampling event and 45.0 mV for the June 2022 Year 2 annual sampling event). The results for 73MW02, 73MW03, and 73MW07 were all negative ranging from negative 78 mV to negative 123 mV during the June 2022 Year 2 annual sampling event.

The DO results for 73MW02, 73MW03 and 73MW07 were all less than 2 mg/L during the June 2022 Year 2 annual sampling event. At 73MW11, DO concentration was 0.47 mg/L during the baseline event and increased by two orders of magnitude to 17.21 mg/L in the first quarterly sampling event post-ORC-A® injection. The DO remained elevated from baseline concentrations through the second and third quarterly sampling events (14.99 mg/L and 10.16 mg/L, respectively), correlating to the decrease in arsenic concentrations over those three events. The DO decreased to 5.31 mg/L during the June 2021 Year 1 annual sampling event and decreased further to 3.77 mg/L during the June 2022 Year 2 annual sampling event, which also saw an increase in the arsenic concentration for those sampling events.

The pH range was 6.27 to 7.06 during the June 2022 Year 2 annual sampling event. This range is slightly acidic which favors maintaining metals, such as arsenic, in solution.

The Year 2 total dissolved solids concentrations (measured as salinity) are in the range of 0.1 to

0.3 parts per thousand (ppt) and are similar to measurements made during previous events.

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Similarly, the specific conductance values measured in the June 2022 Year 2 annual sampling event are similar to those measured during the prior events conducted in 2020 and 2021.

3.3 Data Quality Evaluation

All data generated by the fixed base laboratory were validated in accordance with the requirements of the Basewide Groundwater, Surface Water, and Land Use Control Monitoring UFP-QAPP and Basewide Soil Sampling and Analysis UFP-QAPP (Bay West, 2016a and 2016b) and the Department of Defense Quality Systems Manual, Version 5.0 (DoD, 2013), as specified in the QAPPs. For all sample results, detected results reported below the limit of quantitation (LOQ) but above the detection limit (DL) were qualified as estimated, (J). Non-detected results were reported to the limit of detection (LOD). The following were noted during data validation:

• The MS percent recovery for iron was below the quality control limit for sample 73MW02- PM-062122. The MSD percent recovery and MS/MSD relative percent difference were within quality control limits. The post digestion spike recovery for iron was below the quality control limit. No validation actions were required as the affected sample result was greater than four times the spike added to the sample.

• Sample 73DUP01-062122 was analyzed at a 10X dilution for arsenic and a 2X dilution for sulfate.

• Sample 73MW11-PM-062122 was analyzed at a 10X dilution for arsenic and a 2X dilution for sulfate.

Completeness for the sampling events, defined to be the percentage of analytical results to be usable, was 100 percent. All validation elements, including precision, accuracy, representativeness, completeness, comparability and sensitivity, were evaluated during the data validation process and the data, as qualified, were found to be acceptable for their intended use.

The data validation report is included in Appendix C.

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4.0 RECOMMENDATIONS

This report documents the Year 2 field activities associated with the CMI, including groundwater sampling as part of the RA-O and performance monitoring program, and LUC monitoring.

Synoptic water levels were collected on June 21, 2022, shown on Figure 2-2. During the June 2022 event, groundwater flowed primarily to the south by southeast. The June 2022 groundwater flow pattern is consistent with previous groundwater monitoring results and with data collected during the 2020 and 2021 events. The LUC inspection was conducted June 21, 2022; no issues requiring further action were identified during the LUC inspection.

The groundwater monitoring for the baseline event was conducted in May 2020, the CMI implementation actions of the septic tank investigation, soil excavation, and ORC-A® injections occurred in May through June 2020. The Year 1 quarterly performance monitoring began September 18, 2020 with events in November 19, 2020, March 9, 2020, and the fourth event occurring June 10 and July 15, 2021 (results shown on Figure 2-1). The Year 2 annual performance monitoring event took place on June 21, 2022. In 73MW11 there was an increase in the arsenic concentration from 2022 compared to the Year 1 quarterly sampling events. All arsenic concentrations remained above the MCS in 73MW11 during all sampling events. 73MW02 and 73MW03 arsenic concentrations decreased slightly from the baseline event, with 73MW03 concentration decreasing below the MCS to 9.42 µg/L, while arsenic concentrations remained greater than the MCS at 36.2 µg/L. 73MW07 concentration remained above the MCS (31.4 µg/L June 2021 and increasing to 96.4 µg/L in June 2022). One monitoring well, 73MW02, had iron concentrations that exceeded the MCS in the baseline (2020), Year 1 event (2021), and Year 2 (2022) sampling events. However, the iron concentrations have been relatively stable. The remaining well concentrations were under the MCS and saw slight decreases from the baseline event to Year 1 except for 73MW07 where iron increased from 17,700 µg/L in June 2021 to 47,900 µg/L in June 2022 (above the MCS).

The CMI stated that the monitoring would be conducted quarterly for Year 1, then conducted annually until there are three consecutive sampling events with concentrations less than the MSCs. The Year 3 sampling event will occur in the spring of 2023. LUCs are required until the CMOs have been achieved.

Currently, there are no monitoring wells located hydraulically downgradient from well 73MW07. It is recommended that an additional monitoring well be placed further downgradient on the SWMU73 (FL073) boundary to further define the extent of arsenic contamination and to ensure that the arsenic contamination does not extend beyond the Base property boundary. Installation of one monitoring well downgradient of 73MW07 is scheduled for November 2022.

Given the presence of the electrical transformer within 2 feet of the septic tank, the tank and adjacent contaminated soil could not safely be removed. As a result, it is recommended that the tank and soils remain in place until the transformer is either relocated or removed allowing for the safe and cost effective removal of the tank and soil.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 10 BWJ140078

5.0 REFERENCES

Bay West, 2016a. Uniform Federal Policy – Quality Assurance Project Plan, Performance-Based Remediation, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina, January.

Bay West, 2016b. Uniform Federal Policy – Quality Assurance Project Plan, Performance-Based Remediation, Basewide Soil Sampling and Analysis, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina, February.

DoD, 2013. Department of Defense (DoD) Quality Systems Manual for Environmental Laboratories, Version 5.0. July.

Environmental Protection Agency (EPA), 2017. National Functional Guidelines for Inorganic Superfund Methods Data Review. Office of Superfund Remediation and Technology Innovation, Washington, DC, January.

TEC-BSC Joint Venture, 2013. Draft 2012 Annual Monitoring Report, SWMU 73 South Annex Building 3440, (Battery Shop) Septic Tank, Joint Base Charleston Weapons, Charleston, South Carolina, August.

Tetra Tech, 2006. Data Package Interim Measures Sites SWMUs 38, 47, 66, 67, 68, 69, 72, 73, 74, 77, and 78, Naval Weapons Station, Charleston, South Carolina, August.

Tetra Tech, 2011a. RFI for Interim Measures Sites SWMUs 38, 47, 66, 67, 68, 69, 72, 73, 74, 77, 78, Naval Weapons Station Charleston, Charleston, South Carolina, April.

Tetra Tech, 2011b. Interim Groundwater Monitoring Report, SWMUs 16 and 17, and IM SWMUs 66, 67, 68, 69, 72, 73, and 77. Joint Base Charleston – Weapons, Charleston, South Carolina, June.

Tetra Tech, 2011c. Corrective Measures Study for Interim Measures SWMUs 38, 47, 66, 67, 68, 69, 72, 73, 74, 77, and 78. Joint Base Charleston – Weapons, Charleston, South Carolina, June.

Tetra Tech, 2016. Final Uniform Federal Policy – Quality Assurance Project Plan (UFP-QAPP) Performance Based Remediation, Corrective Measures Study Work Plan for SWMU 73 (FL073), JBC Weapons, South Carolina, July.

Tetra Tech, 2017. Corrective Measures Study Report for SWMU 73. Joint Base Charleston – Weapons, Charleston, South Carolina, October.

Tetra Tech, 2018. Statement of Basis for SWMU 73 (FL073) South Annex Building 3440, Battery Shop Septic Tank. Joint Base Charleston Weapons, North Charleston, South Carolina, April.

Tetra Tech, 2019. Corrective Measures Implementation Work Plan for SWMU 73. Joint Base Charleston – Weapons, Charleston, South Carolina, May.

Tetra Tech, 2020. Draft Final Corrective Measures Implementation Completion Report, Solid Waste Management Unit 73 (FL073). Joint Base Charleston Weapons, Charleston, South Carolina, May (approved as Final).

Tetra Tech, 2022. Draft Final Corrective Measures Implementation Year 1 Annual Report, Solid Waste Management Unit 73 (FL073). Joint Base Charleston Weapons, Charleston, South Carolina, February.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 11 BWJ140078

TolTest, 2005. Closure Report Interim Measures and Confirmatory Sampling SWMU Sites. Naval Weapons Station, Charleston, South Carolina, December.

FIGURES

Former Naval Station Charleston

Joint Base Charleston Weapons

COOPE R

RI VER

WA

ND

O

RI

VE

R

ATLANTIC

OCEAN

Back River

Charleston AFB/Intl

Charleston--North Charleston

§̈¦26

§̈¦526

§̈¦26

§̈¦526

£¤17

£¤78

£¤176

£¤52

£¤701

£¤52

£¤17

£¤78

£¤52

£¤52

UV61

UV41

UV700

UV162

UV171

UV165

UV7

UV703

UV61

UV171

UV171

UV165

Rh ett

River

Main

Red Bank Ladson

Spruill

Bushy Park

Clements Ferry

Hill

Jed bur g

King

Bees Ferry

Ro yle

Remount

County Line

Central

Old Trolley

Middle

Rifle Range

College Park

Old Dairy

Cyp ress Gardens

Harbor V iew

Long Point

Crowfie ld

Fort Jo hnson

Davison

Jamison Lincolnville

Ashley Phosphate

Ma ple

Stall

Bohicket

Sa vage

Meeting Street

Liberty Hall

Lee ds

Montague

Orleans

Lincoln

Magnolia

Gu m6th

Snake River

Middle

Berkeley

Charleston

Dorchester

³

3.5 3.50 Miles

JAX:C:\GIS\CHARLESTON\MXD\2016 FIELD DATA\SWMU 73\JL MAY 2017\FIGURE_1-1_LOCATION_MAP.MXD 12/15/2021

LOCATION MAP

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Charleston, SC

DATEDRAWN BY

CTO

J.MADDEN 12/15/21

DATECHECKED BY

P.LEHOCKY 12/15/21

FIGURE NUMBER

1-1

0 100 20050 Miles

BACK RIVER

COOPER RIVER

NORTH SIDE

(POMFLANT)

WEAPONS

STATION

WEAPONS

STATION

GOOSE CREEK

MAIN ENTRANCE

BUSHY

PARK

RED BANK RD

JOINT BASE CHARLESTON WEAPONS

BOUNDARY

NORTH CHARLESTON

CH

AR

LE

ST

ON

CO

BE

RK

EL

EY

CO

CSX RAILROAD

SOUTH SIDE

SWMU 73

³

6,000 6,0000 Feet

JAX: C:\GIS\Charleston\MXD\2016 Field Data\SWMU 73\JL May 2017\Figure_1-1_swmu73_fac_loc.mxd

SITE LOCATION MAP

SWMU 73 - SOUTH ANNEX BUILDING 3440

BATTERY SHOP SEPTIC TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

DATEDRAWN BY

CTO

J.MADDEN 12/15/21

DATECHECKED BY

P.LEHOCKY 12/15/21

FIGURE NUMBER

1-2

T-27

3442 ³ JAX: C:\GIS\Charleston\MXD\2016 Field Data\SWMU 73\JL May 2017\Figure_1-3_SWMU73_sitemap.mxd

100 1000 Feet

SITE MAP

SWMU 73 - SOUTH ANNEX BUILDING 3440 BATTERY SHOP SEPTIC TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Legend SWMU 73 Boundary

SWMU 66

Original Site Boundary of SWMU 73 Other SWMU Boundaries

DATEDRAWN BY

CTO

J.MADDEN 10/20/20

DATECHECKED BY

P.LEHOCKY 10/20/20

FIGURE NUMBER

1-3

+U

+U

+U

+U

+U

+U

+U

+U

Former

6th STREET

7th STREET

AVENUE A

WOODS AVE

AVENUE A

Surveyed Covered

Porch

73MW07 5/28/2020

ARSENIC 11.6

IRON 5,110

7/15/2021

ARSENIC 31.4

IRON 17,700

73MW09

73MW10

73MW05

73MW04

73MW01

Groundwater Plume Arsenic >10 ug/L

+U

ORC Injection Area

Electrical Transformer

73MW11 5/29/2020

ARSENIC 1,380

IRON 5,060

9/18/2020

ARSENIC 382

IRON 1,220

11/19/2020

ARSENIC 781

IRON 2,080

3/9/2021

ARSENIC 536

IRON 2,350

6/10/2021

ARSENIC 1,280

IRON 3,870

T-27

T-25

Former T-23

Tank

Fiber Optic

Conduit Box

73MW06

73MW03 5/28/2020

ARSENIC 10.5

IRON 24,300

6/10/2021

ARSENIC 9.13

IRON 20,500

73MW02 5/28/2020

ARSENIC 40.4/41.3

59,000/60,200

6/10/2021

ARSENIC 35.6/33.7

IRON 56,900/54,900

³ JAX: C:\GIS\Charleston\MXD\2016 Field Data\SWMU 73\JL May 2017\2-1_swmu73_gw_tags_ORC_Sept2021.mxd

100 1000 Feet

BASELINE AND CORRECTIVE MEASURES IMPLEMENTATION GROUNDWATER SAMPLING RESULTS

SWMU 73 - SOUTH ANNEX BUILDING 3440 BATTERY SHOP SEPTIC TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Shaded yellow tag indicates well for long-term monitoring program.

SWMU 69

Legend

Monitoring Well Location+U

DATEDRAWN BY

CTO

J.MADDEN 10/20/22

DATECHECKED BY

L ADAMS 10/20/22

FIGURE NUMBER

2-1

ORC Injection Area

Analyte MCS Metals (ug/L) Arsenic 10 Iron 26,900

Bold = Exceeds MCS ug/L = micrograms per Liter 40.4/41.3 - Parent sample/duplicate

Groundwater Plume Road Railroad Building Former Building SWMU 73 Boundary Original Site Boundary of SWMU 73 Other SWMU Boundaries Topog raphic Contour (1 ft interval)

6/21/2022

ARSENIC 1,560/1,520

IRON 3,340/3,620

6/21/2022

ARSENIC 36.2

IRON 55,400

6/21/2022

ARSENIC 9.42

IRON 18,700

6/21/2022

ARSENIC 96.4

IRON 47,900

IRON

+U

+U

+U

+U

+U

+U

+U

Former

6th STREET

7th STREET

AVENUE A

WOODS AVE

AVENUE A

Surveyed Covered

Porch

AVENUE B

73MW07

(8.45)

12 10

Transformer

T-27

T-25

Former T-23

Tank

Fiber Optic

Conduit Box

73MW10

(17.18)

73MW09

(14.07)

73MW06

(13.97)

73MW05

(15.50)

73MW04

(20.46)

73MW03

(14.67)

73MW02

(15.99)

73MW01

(25.93)

³ JAX: C:\GIS\Charleston\MXD\2016 Field Data\SWMU 73\JL May 2017\2-2_swmu73_gw_contours_June2021.mxd

100 1000 Feet

GROUNDWATER ELEVATION MAP - JUNE 21, 2022

SWMU 73 - SOUTH ANNEX BUILDING 3440 BATTERY SHOP SEPTIC TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Legend

Road Railroad

Building Former Building

Groundwater Flow Direction

"́ Monitoring Well Location

(27.22) Groundwater Elevation (ft amsl)

Groundwater Elevation Contour (dashed where inferred)

Extent of Excavation

SWMU 73 Boundary Original Site Boundary of SWMU 73 Other SWMU Boundaries

SWMU 69

DATEDRAWN BY

CTO

J.MADDEN 10/20/22

DATECHECKED BY

L. ADAMS 10/20/22

FIGURE NUMBER

2-2

Topographic Contour (1 ft interval)

ORC Injection Area

Groundwater Plume

+U

73MW11

(19.77) leah.adams Polygonal Line

TABLES

Table 2-1

Summary of Groundwater Quality Parameter Data SWMU 73 (FL073) - South Annex 3440, Battery Shop Septic Tank

Joint Base Charleston Weapons, South Carolina

Well Number Date pH (S.U.)

Specific

Conductance (mS/cm)

Dissolved Oxygen (mg/L)

Turbidity (NTUs)

Temperature (°C) ORP (mV) Salinity

(ppt)

Ferrous Iron

(mg/L)

73MW02 5/28/2020 6.39 0.348 0.49 7.0 21.85 -91.4 0.17 23.7

73MW02 6/10/2021 5.66 0.340 0.00 1.29 24.23 -132.0 0.20 +++

73MW02 6/21/2022 6.62 0.277 0.35 8.20 23.26 -78.0 0.10 NM

73MW03 5/28/2020 6.75 0.600 0.38 6.0 22.95 -121.9 0.29 8.6

73MW03 6/10/2021 5.88 0.583 0.00 1.42 23.22 -135.0 0.30 +++

73MW03 6/21/2022 7.06 0.500 1.61 3.00 27.80 -123.0 0.20 3.3

73MW07 5/28/2020 5.26 0.126 0.49 28 24.39 50.0 0.06 25

73MW07 7/15/2021 5.82 0.202 0.00 25.90 26.79 -123.0 0.10 +++

73MW07 6/21/2022 6.62 0.538 0.20 6.00 29.51 -84.0 0.30 NM

73MW11 5/29/2020 5.45 0.144 0.47 56 21.28 36.1 0.07 2.69

73MW11 9/18/2020 6.82 0.508 17.21 36.00 25.09 192.0 0.20 0.39

73MW11 11/19/2020 6.88 0.294 14.99 48.00 16.97 30.0 0.14 0.33

73MW11 3/9/2021 6.75 0.255 10.16 49.00 17.90 68.0 0.12 0.26

73MW11 6/10/2021 5.56 0.239 5.31 38.20 25.25 44.0 0.11 2.7

73MW11 6/21/2022 6.27 0.206 3.77 33.50 22.44 45.0 0.10 2.66

Notes:

+++ - Above range of Hach DR900 Colorimeter °C - Degrees Celsius mS/cm - MilliSiemens per centimeter mg/L - Milligram per liter mV - Millivolts ppt - Parts per thousand NTUs - Nephelometric turbidity units ORP - Oxidation reduction potential S.U. - Standard units NM - Not measured due to field error

Table 2-2

Analytical Results in Groundwater Samples and Comparison to Media Cleanup Standards

SWMU 73 (FL073)

Joint Base Charleston Weapons, South Carolina

Analyte MCS

ARSENIC 10 40.4 41.3 35.6 33.7 36.2 10.5 9.13 9.42 11.6 31.4

IRON 26900 59000 60200 56900 54900 55400 24300 20500 18700 5110 17700

SULFATE (SW-846 9056A) NC 0.236 0.251 0.5 0.501 0.266 0.159 J 0.225 0.151 J 11.4 6.41 SULFIDE (SW-846 9034) NC 1.5 U 1.5 U 1.5 U 1.5 U 1.5 U 1.5 U 1.5 U 2.6 1.5 U 3.6 u TOTAL ORGANIC CARBON (SW-846 9060A) NC 13.8 13.7 6.87 J 7.69 J 9.1 17.2 11.5 J 11.2 37.6 106

Notes:

Bolded values indicate detected analyte.

Highlighted values exceed the MCS.

ug/L = Microgram per liter.

mg/L = Milligram per liter.

NC = No criteria.

MCS = Media Cleanup Standard.

Data Qualifiers:

J = Estimated value.

U = Non-detect and the associated value is the limit of detection (LOD).

73MW07-PM-

GW-0520

73MW07

ORIGINAL

73MW07

73MW07-PM-

GW-0721

ORIGINAL

20210715

MISCELLANEOUS (MG/L)

73MW02 73MW02 73MW03

ORIGINAL DUPLICATE ORIGINAL DUPLICATE ORIGINAL

20210610 20210610

ORIGINAL

20200528

73MW02-PM-

GW-0621

73MW02-PM-

GW-0621-D

73MW03-PM-

GW-0621

73MW02 73MW02 73MW03

73MW03-PM-

GW-0520

73MW02

73MW02-PM-

GW-0520

73MW02-PM-

GW-0520-D

Sample Location:

Sample ID:

Sample Type:

73MW02-PM-

062122

ORIGINAL

20220621

73MW03

73MW03-PM-

062122

ORIGINAL

20220621

METALS, SW-846 6020B (UG/L)

Sample Date: 20200528 20200528 2020052820210610

Table 2-2 (continued)

Analytical Results in Groundwater Samples and Comparison to Media Cleanup Standards

SWMU 73 (FL073)

Joint Base Charleston Weapons, South Carolina

Analyte MCS

ARSENIC 10

IRON 26900

SULFATE (SW-846 9056A) NC

SULFIDE (SW-846 9034) NC

TOTAL ORGANIC CARBON (SW-846 9060A) NC

Notes:

Bolded values indicate detected analyte.

Highlighted values exceed the MCS.

ug/L = Microgram per liter.

mg/L = Milligram per liter.

NC = No criteria.

MCS = Media Cleanup Standard.

Data Qualifiers:

J = Estimated value.

U = Non-detect and the associated value is the limit of detection (LOD).

MISCELLANEOUS (MG/L)

Sample Location:

Sample ID:

Sample Type:

METALS, SW-846 6020B (UG/L)

Sample Date:

96.4 1380 382 781 536 1280 1560 1520 47900 5060 1220 2080 2350 3870 3340 3620

0.207 11.2 39 15.6 17.6 17.4 12.1 11.4

1.5 U 1.5 U 1.5 U 1.5 U 1.5 U 1.5 U 4 4.2

9.85 26.6 21.9 19.1 18.4 21.5 J 25.6 24.2

73MW11

73MW11-PM-

GW-062122-D

DUPLICATE

20220621

73MW07

73MW07-PM-

062122

ORIGINAL

20220621

73MW11

73MW11-PM-

GW-062122

ORIGINAL

20220621

ORIGINAL

73MW11

73-MW11-PM-

GW-0520

20200529

ORIGINAL

20200918

ORIGINAL

20210610

ORIGINAL

20201119

ORIGINAL

20210309

73MW11-PM-

GW-0621

73MW11 73MW11

73MW11-PM-

GW-1120

73MW11

73MW11-PM-

GW-0321

73MW11

73MW11-PM-

GW-0920

Table 2-3

Well Construction Information and Groundwater Level Measurements

SWMU73 (FL073)

Joint Base Charleston Weapons, South Carolina

Depth to Water (ft btoc)

Groundwater Elevation (ft amsl)

73MW01 29.95 32.43 3 - 13 26.95 16.95 5.54 26.89

73MW02 18.74 21.34 3 - 13 15.74 5.74 4.51 16.83

73MW03 18.26 20.87 3 - 13 15.26 5.26 5.28 15.59

73MW04 23.72 26.35 3 - 13 20.72 10.72 5.12 21.23

73MW05 17.89 20.66 3 - 13 14.89 4.89 4.48 16.18

73MW06 17.55 20.21 3 - 13 14.55 4.55 5.42 14.79

73MW07 15.31 17.98 5 - 10 10.31 5.31 7.90 10.08

73MW09 16.98 19.96 4 - 9 12.98 7.98 5.17 14.79

73MW10 19.21 21.75 3 - 13 16.21 6.21 3.53 18.22

73MW11 23.82 25.86 3 - 13 NM NM 4.47 NM

Notes:

ft amsl - feet above mean sea level.

ft btoc - feet below top of casing.

ft bgs - feet below ground surface.

NM - Not measured.

Bottom of Screen

Elevation (ft amsl) September, 2020

Well Number Ground

Elevation (ft amsl)

Top of Riser Elevation (ft amsl)

Screen Interval (ft bgs)

Top of Screen

Elevation (ft amsl)

Table 2-3

Well Construction Information and Groundwater Level Measurements

SWMU73 (FL073)

Joint Base Charleston Weapons, South Carolina

Depth to Water (ft btoc)

Groundwater Elevation (ft amsl)

Depth to Water (ft btoc)

Groundwater Elevation (ft amsl)

5.65 26.78 6.50 25.93

4.41 16.93 5.35 15.99

5.26 15.61 6.20 14.67

5.05 21.30 5.89 20.46

4.33 16.33 5.16 15.50

5.35 14.86 6.24 13.97

8.08 9.90 9.53 8.45

5.09 14.87 5.89 14.07

3.54 18.21 4.57 17.18

4.60 NM 6.09 19.77

June 15, 2021 June 21, 2022

APPENDIX A

FIELD DOCUMENTATION

Page 318 of 31908/30/2022 10:23Pace Gulf Coast Report#: 222062315

APPENDIX B

LABORATORY DATA REPORTS

(ON ATTACHED CD)

Cover

ANALYTICAL RESULTS

PERFORMED BY

Pace Analytical Gulf Coast 7979 Innovation Park Dr.

Baton Rouge, LA 70820

(225) 769-4900

Report Date 08/30/2022

Report # 222062315

9999999999

Project JBC / 112G07681SWMU 73

Samples Collected 6/21/22

Deliver To Additional Recipients Leah Adams Scott Nesbit, Tetra Tech Tetra Tech Michelle Coffman, Tetra Tech 661 Andersen Drive

Suite 200 Carrie Stock, Tetra Tech

Pittsburgh, PA 15220 Amy Thomson, Tetra Tech, Inc.

740-607-4055

LELAP Certificate Number:…