B.08 GFI JB CHS PBR_ID068 (SWMU 68)_Draft 2022 Year 4 LTM Report.pdf

DRAFT

2022 Year 4 Annual Long-Term Monitoring Report

Solid Waste Management Unit 68 (ID068)

PERFORMANCE-BASED REMEDIATION

Joint Base Charleston Weapons

SOUTH CAROLINA

Contract FA8903-15-C-0016 January 2023 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 661 Andersen Drive

Foster Plaza 7 Pittsburgh, PA 15220

(412)921-7090

With Teaming Partners:

2022 Annual Long-Term Monitoring Report

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 i BWJ140078

Table of Contents

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

1.1 Project Authorization .................................................................................................. 1-1

1.2 Objective and Scope .................................................................................................. 1-1

1.3 Site Description and Location ..................................................................................... 1-1

1.4 Historical Use ............................................................................................................. 1-2

1.5 Previous Studies ........................................................................................................ 1-2

1.6 Tank Closure or Removal, Monitored Natural Attenuation, and Land Use Controls .. 1-4

1.7 Site Hydrology ............................................................................................................ 1-4

1.8 Human Health Risk Evaluation ................................................................................... 1-5

LONG-TERM MONITORING EVENT ACTIVITIES ................................................... 2-1

2.1 Field Activities ............................................................................................................ 2-1

2.1.1 LUC Inspection ....................................................................................................... 2-1

2.1.2 LTM Groundwater Sampling Event ........................................................................ 2-1

2.1.3 LTM Surface Water Sampling Event ...................................................................... 2-1

2.1.4 Water Level Measurements ................................................................................... 2-2

2.1.5 Groundwater Flow and Direction ............................................................................ 2-2

2.1.6 Investigation-Derived Waste .................................................................................. 2-2

ANALYTICAL RESULTS .......................................................................................... 3-1

3.1 Nature and Extent of Contamination .......................................................................... 3-1

3.2 Natural Attenuation and Geochemical Parameters .................................................... 3-1

3.3 Data Validation ........................................................................................................... 3-2

SUMMARY AND RECOMMENDATION .................................................................... 4-1

REFERENCES ........................................................................................................... 5-1

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List of Figures

Figure 1-1 Location Map Figure 1-2 Site Location Map Figure 1-3 Historical Features Figure 2-1 Groundwater Elevation Map – June 22, 2022 - Low-Tide Figure 3-1 Analyte Exceedances in Groundwater and Surface Water– June-September 2022 Figure 4-1 Arsenic Concentrations in Groundwater vs. Time Figure 4-2 Manganese Concentrations in Groundwater vs. Time

List of Tables

Table 2-1 Well Construction Information and Groundwater Level Measurements Table 2-2 Summary of Groundwater Quality Parameter Data and Field Test Kit

Measurements Table 2-3 Summary of Parameters, Analytical Test Methods and Media Cleanup Standards Table 3-1 Summary of Analyte Detections in Groundwater and Surface Water

List of Appendices

Appendix A Historical Analytical Results Appendix B Field Sampling Forms Appendix C LUC Inspection Checklist (June 2022) Appendix D Laboratory Analytical Reports (on attached CD) Appendix E Data Validation Reports (on attached CD)

Contract FA8903-15-C-0016 iii BWJ140078

Acronyms and Abbreviations

AFCEC ............ Air Force Civil Engineer Center bgs .................. below ground surface CMS ................ Corrective Measures Study COC ................ contaminant of concern DO ................... dissolved oxygen ERP ................. Environmental Restoration

Program ft ...................... foot/feet HHRSE ........... Human Health Risk

Screening Evaluation IDW ................. investigation-derived waste JBC ................. Joint Base Charleston LOD ................. limit of detection LTM ................ long-term monitoring LUC ................. land use control MCL ................ maximum contaminant level MCS ................ Media Cleanup Standard mg/kg .............. milligram per kilogram MNA ................ monitored natural attenuation MS/MSD .......... matrix spike/matrix spike duplicate NFA ................. No Further Action ORP ................ oxidation-reduction potential PAL ................. project action level

POC ................ point of contact RCRA .............. Resource Conservation and

Recovery Act RCRA Permit ... RCRA Hazardous Waste

Permit No. SC8 170 022 620 RFA ................. RCRA Facility Assessment RFI .................. RCRA Facility Investigation RSL ................. regional screening level RTC ................. response to comments SCDHEC ......... South Carolina Department of Health and Environmental Control

SoB ................. Statement of Basis SVOC .............. semi-volatile organic compound SWMU ............. solid waste management unit TDS ................. total dissolved solids TOC................. total organic carbon UFP-QAPP ...... Uniform Federal Policy –

Quality Assurance Project Plan µg/L ................. microgram per liter USEPA ............ United States Environmental

Protection Agency VOC ................ volatile organic compound

Contract FA8903-15-C-0016 1-1 BWJ140078

INTRODUCTION

1.1 Project Authorization

This 2022 Year 4 Annual Long-Term Monitoring (LTM) Report has been prepared to describe the LTM activities conducted in June and September 2022 at Solid Waste Management Unit (SWMU) 68 (ID068) at Joint Base Charleston (JBC) Weapons located in Charleston, South Carolina. This project is being conducted under Contract FA8903-15-C-0016 for the United States Air Force Civil Engineer Center (AFCEC), in support of the Environmental Restoration Program (ERP) at JBC Weapons.

The field activities conducted in June and September 2022 included groundwater and surface water sampling, 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, 2016).

1.2 Objective and Scope

The objective of annual LTM events at SWMU 68 (ID068) is to comply with the requirements of the Resource Conservation and Recovery Act (RCRA) Hazardous Waste Permit No. SC8 170 022 620 (RCRA Permit) issued to JBC Weapons by the South Carolina Department of Health and Environmental Control (SCDHEC). The LUC inspection event was completed on June 22, 2022 and the annual groundwater monitoring event was conducted June 22, 2022. A surface water sample was collected on September 1, 2022 per SCDHEC’s request.

The purpose of this document is to summarize results of the 2022 Year 4 Annual LTM event per the RCRA Permit, compare the Year 1 through Year 4 results (Tetra Tech, 2020a, Tetra Tech, 2020b, and Tetra Tech, 2022), and to verify that the remedy remains protective of human health.

The RCRA Permit requires that analytical results of all contaminants of concern (COCs) in groundwater must remain at or below cleanup levels (see Table 2-3 for Media Cleanup Standards [MCSs]) for a minimum of three consecutive years before it can be determined that No Further Action (NFA) is applicable at a given site.

1.3 Site Description and Location

Site Name: South Annex Building 3637, General Purpose Warehouse Waste Tank

RCRA Permit Status: Requires Land Use Controls

JBC Weapons is located 10 miles north of Charleston, South Carolina, and approximately 16 miles inland from the Atlantic Ocean. The facility is situated in two counties, Berkeley and Charleston, and occupies 16,868 acres. Air Force Environmental Restoration Program Site SWMU 68 (ID068) consists of asphalt and patches of grass near Building 3637 located in the northeastern corner of the South Annex (Tetra Tech, 2018b). The building was originally constructed as an “Inert Storage Warehouse” in 1941, during the time that the depot was handling ordnance. Records also show that the building was being used in 1970 as a “General Purpose Warehouse” (Tetra Tech, 2018b). The septic tank for this building may have been constructed to receive general sanitary wastewater from the employee facilities. Goose Creek and a tributary to Goose Creek are approximately 200 feet to the north. A location map and a site location map for SWMU 68 (ID068) are provided as Figure 1-1 and 1-2, respectively. The location of the historical septic tank is identified on Figure 1-3.

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1.4 Historical Use

SWMU 68 (ID068) – South Annex Building 3637, General Purpose Warehouse Waste Tank consists of asphalt and patches of grass near Building 3637 located in the northeastern corner of the South Annex (Tetra Tech, 2018b). The Building 3637 General Purpose Warehouse Waste Tank location was estimated by the base Point of Contact (POC) at the time, Barry Lewis, Hazardous Waste Program Manager. The Base sanitary sewer map, dated September 1, 1970, shows a septic tank labeled “45” adjacent to Building 3637. The building was originally constructed as an “Inert Storage Warehouse” in 1941, during the time that the depot was handling ordnance. Records also show that the building was being used in 1970 as a “General Purpose Warehouse” (Tetra Tech, 2018b). The septic tank for this building may have been constructed to receive general wastewater from the employee restroom.

1.5 Previous Studies

Several investigations have been conducted at SWMU 68 (ID068). A RCRA Facility Assessment (RFA) was completed in 1997 (WPNSTA Charleston, 1997). During the RFA, the 1,000-gallon concrete septic tank was located. The cover of the tank had been broken, allowing rainwater to seep into it. A large quantity of sediment was present at the bottom of the tank, and a sample was collected and analyzed for Appendix IX volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and metals. VOCs and SVOCs were not detected. Numerous metals were detected; comparisons of detected concentrations to criteria in place at the time showed that only arsenic at 4.760 milligrams per kilogram (mg/kg) exceeded its screening criterion of 0.390 mg/kg, but the detection was less than the facility background concentration of 14.2 mg/kg (WPNSTA Charleston, 1997). The RFA Report recommended that the tank be removed and samples be collected.

A RCRA Facility Investigation (RFI) was conducted in 2009 (Tetra Tech, 2011a). Soil and groundwater samples were collected during the RFI, with criteria exceedances noted in groundwater. The planned RFI was hampered by utility interferences at the site, so the RFI focused on impacts to the downgradient area (approximately 150 to 400 feet downgradient).

Thirteen temporary wells were installed as part of the RFI and arsenic was detected at concentrations greater than the maximum contaminant level (MCL) in 12 of the 13 temporary monitoring wells. The RFI recommended monitoring of groundwater for arsenic with additional investigation to delineate the plume. It was additionally noted that arsenic exceedances were also encountered at SWMU 20, located east of SWMU 68 (ID068); however, the concentrations of arsenic measured at SWMU 20 were lower than the concentrations measured at SWMU 68 (ID068). It was further noted that the originally perceived source (i.e. septic tank) may not be responsible for the contamination. It was suspected that the Historical Open Storage Area (see Figure 1-3) may be the source; therefore, additional groundwater investigation was recommended to encompass this upgradient area to assess if the Historical Open Storage Area was the source of arsenic contamination in groundwater. It was also recommended that soil sampling be conducted in this area.

Eight permanent monitoring wells were installed at SWMU 68 (ID068) in 2011 (68MW01 through 68MW08) (Tetra Tech, 2011b). One of these permanent monitoring wells, 68MW01, was installed in the Historical Open Storage Area to respond to the RFI recommendation. Arsenic remained present in groundwater at concentrations greater than screening criteria in seven of the eight monitoring wells. Arsenic concentrations exceeded screening criteria in monitoring wells 68MW01, 68MW02, 68MW03, 68MW04, 68MW05, 68MW06, and 68MW08. It was recommended that a long-term monitoring plan be prepared for SWMU 68 (ID068), and that monitoring wells be sampled for arsenic. Because groundwater flow direction was not consistent between the RFI and

Contract FA8903-15-C-0016 1-3 BWJ140078 the 2011 event, it was recommended that groundwater level measurements be carefully evaluated during future monitoring events to confirm groundwater flow direction. In addition, recommendations included possibly expanding the monitoring well network for future monitoring purposes. It was also determined that collection of a surface water sample may be warranted north of 68MW02 to monitor arsenic concentrations to the north.

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

SCDHEC provided comments on the CMS Report in 2012 and stated that additional investigation was warranted, a more in-depth investigation of the tank needed to be conducted, and the current use of the waste tank needed to be discussed. Furthermore, SCDHEC requested that SWMU 20 data be provided, along with an explanation to support the rationale that SWMU 20 could be contributing to the arsenic source at SWMU 68 (ID068). During preparation of the response to comments (RTCs) for the CMS report in late 2012 and early 2013, SWMU 68 (ID068) information and drawings were further examined, and additional site reconnaissance was conducted by the JBC Weapons POC in the SWMU 68 (ID068) septic tank area. The location of the SWMU 68 (ID068) septic tank was determined based on information supplied by the base. SCDHEC conditionally approved the CMS Report and RTCs in 2013 with the requirement to submit a CMS Work Plan for the additional investigation requested at SWMU 68 (ID068). None of the corrective measures identified in the conditionally approved 2011 CMS were implemented.

A round of groundwater samples was collected in 2012. Arsenic was detected at concentrations greater than the MCL in five monitoring wells (68MW03, 68MW04, 68MW05, 68MW06, and 68MW08) (TEC-BSC Joint Venture, 2013).

Based on comments received from SCDHEC on the conditionally approved 2011 CMS, a CMS Work Plan was developed to describe the plan for collecting additional data (Tetra Tech, 2016).

During the 2016 CMS investigation, two permanent and one temporary groundwater monitoring well were installed and a round of groundwater samples was collected from all permanent monitoring wells and a temporary monitoring well at SWMU 68 (ID068). The temporary monitoring well was installed adjacent to the presumed location of the septic tank. The permanent monitoring wells were installed to better define the groundwater plume. Also, an intrusive investigation of the septic tank area was conducted to confirm the location of the tank and three subsurface soil samples were collected. Groundwater samples collected from the permanent monitoring wells were analyzed for metals, total organic carbon (TOC), sulfate, sulfide, ferric iron, ferrous iron, and ortho-phosphate. Soil samples and the groundwater sample collected from the temporary monitoring well were analyzed for metals only to aid in the determination as to whether the septic tank may be the source of the contamination.

Arsenic was detected in 68MW03, 68MW04, 68MW05, 68MW06, 68MW08, and 68MW10 at concentrations greater than the project action level (PAL) and facility background concentration.

Manganese was also detected at concentrations greater than the PAL and facility background in 2016 in 68MW03, 68MW05, 68MW06, 68MW08, 68MW09, and 68MW10. Historical groundwater analytical data summarized in the CMS is included in Appendix A. There were no detections of arsenic or other target analytes at concentrations greater than PALs or facility background measured in the groundwater sample collected from the temporary well installed in 2016.

The presence of the buried concrete septic tank was suspected to be confirmed during the intrusive investigation conducted during the 2016 CMS investigation based on a subsurface obstruction encountered with a hand auger, but piping or other tank infrastructure were not identified. Soil samples were collected in areas around the tank based on confirmation of the

Contract FA8903-15-C-0016 1-4 BWJ140078 presence of the tank during the intrusive investigation. All detections of arsenic and other metals were less than PALs and facility background.

1.6 Tank Closure or Removal, Monitored Natural Attenuation, and Land Use Controls

Septic tank closure or removal, Monitored Natural Attenuation (MNA), and LUCs for groundwater was the remedial alternative recommended for SWMU 68 (ID068) in the 2018 Statement of Basis (SoB) (Tetra Tech, 2018a). SWMU 68 (ID068) is included in the October 23, 2019 permit modification (Hazardous Waste Permit, No. SC8 170 022 620, Appendix A-8, Solid Waste Management Units (SWMUs) and AOCs requiring LUCs).

Although it is unlikely that the septic tank is an ongoing source of contamination at the site based on the analytical results of samples collected in locations adjacent to the suspected tank location, the tank was further investigated in 2019 and 2020 (described further in the Year 2 2020 LTM Report [Tetra Tech, 2020b]). The proposed remedy included tank removal or closure in place along with identification of any tank infrastructure or piping.

MNA consists of long-term monitoring of arsenic and manganese as well as geochemical parameters to verify that subsurface conditions are resulting in decreased concentrations of arsenic and manganese to achieve site closure. The concentrations of inorganic COCs, such as arsenic and manganese, would be reduced as the groundwater flows into zones with oxidizing conditions. Such conditions would result in the precipitation of the metals and sorption to soil particles. Long-term monitoring of these COCs at select wells will provide insight into the rates of attenuation and degradation of the COCs. Monitoring of geochemical parameters, such as oxidation reduction potential (ORP), pH, ferrous iron, dissolved oxygen (DO), sulfate, and sulfide is conducted to evaluate whether subsurface conditions are favorable for achieving cleanup objectives.

LUCs for SWMU 68 (ID068) prohibit the installation of wells for potable water uses within the surficial groundwater. The Base Remedial Project Manager works with the 628 Civil Engineer Squadron Base Community Planner (Base Community Planner) to confirm that LUCs are implemented and enforced at applicable sites. Because the installation of wells uses the dig permit process, the Base Remedial Project Manager will be notified as part of the review and approval process and will be able to take action. Annual inspections are required to verify that LUCs are being enforced. LUC inspections are conducted by Tetra Tech using the SWMU 68 (ID068) LUC Monitoring Checklist. Deficiencies would be reported to SCDHEC and corrected.

1.7 Site Hydrology

The subsurface material within the upper 2 to 4 feet beneath the site consists of irregularly bedded silty sand, interpreted to be principally reworked natural material. Underlying the surface material is a clay unit that extends to 14 to 19 feet below ground surface (bgs). A sand and shell fragment mixture was encountered below the clay with a thickness from 5 to 8 feet. Underlying this layer, at 19 to 24 feet bgs, is a moderate olive brown silt. The water bearing zone was encountered at 6 to 8 feet bgs and 1.5 to 8.9 feet bgs following well completion, suggesting semi-confined conditions.

Synoptic water level data were collected during the 2016 CMS Investigation and from the August 2019 sampling event indicate that the groundwater flow patterns change between high and low tide conditions. During the 2016 CMS Investigation the groundwater flowed to the south during the high tide indicating that the groundwater is being recharged by the surface water to the north from Goose Creek and its tributary; and during low tide the groundwater flowed primarily to the

Contract FA8903-15-C-0016 1-5 BWJ140078 northwest toward a tributary of Goose Creek. During the August 2019 event, groundwater flowed primarily to the north during low tide and primarily to the east/northeast during high tide. There was a slight depression in groundwater in the vicinity of 68MW04 at high tide during the August 2019 event. Synoptic water level data for the June 2020 LTM event was collected during mid-tide and the groundwater flow direction was primarily to the north/northeast toward Goose Creek and an associated tributary. Synoptic water level data for the June 2022 LTM event was collected during low tide and the groundwater flow direction was primarily to the north/northwest toward Goose Creek and an associated tributary (see Section 2.1.4 and Figure 2-1).

1.8 Human Health Risk Evaluation

A human health risk screening evaluation (HHRSE) for SWMU 68 (ID068) was initially conducted as part of the RFI (Tetra Tech, 2011a). The HHRSE was updated as part of the CMS (Tetra Tech, 2018b) because new United States Environmental Protection Agency (USEPA) default exposure assumptions (used to estimate risks) for some exposure factors had been published, toxicity criteria for some chemicals had been updated, USEPA regional screening levels (RSLs) had been updated since the RFI report (Tetra Tech, 2011a) was completed, and permanent monitoring wells had been installed. Additionally, the Basewide Facility Background (background) concentrations were updated in 2017 (Tetra Tech, 2017).

As documented in the 2018 CMS, no COCs were identified for soil and arsenic and manganese were identified as COCs in groundwater. The calculated MCS for manganese in groundwater is 430 micrograms per liter (µg/L). The MCS for arsenic in groundwater is the USEPA MCL of 10 µg/L. Detailed information on the updated HHRSE and MCS determinations is located in the 2018 CMS (Tetra Tech, 2018b). Attainment of MCSs will allow for unlimited use/unrestricted exposure.

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LONG-TERM MONITORING EVENT ACTIVITIES

2.1 Field Activities

The LTM events discussed in this report were completed in June and September 2022. The LTM events consisted of the completion of the following activities:

• Completion of LUC inspections on June 22, 2022;

• Collection of LTM groundwater samples and water level measurements from 10 monitoring wells on June 22, 2022; and

• Collection of one surface water sample from a tributary to the Cooper River on September 1, 2022.

Each of these field activities are discussed in the sections below. Field sampling logs are contained in Appendix B.

2.1.1 LUC Inspection

A LUC inspection was completed on June 22, 2022. The LUC for SWMU 68 (ID068) includes prohibition of the installation of wells for potable water uses within the surficial groundwater aquifer. Site fencing is not part of the LUC; however, a security perimeter fence is located downgradient of SWMU 68 (ID068). No issues requiring further action were identified during the LUC inspection. A copy of the June 2022 LUC inspection checklist is included as Appendix C.

2.1.2 LTM Groundwater Sampling Event

The following 10 monitoring wells were sampled during the 2022 LTM event: 68MW01, 68MW02, 68MW03, 68MW04, 68MW05, 68MW06, 68MW08, 68MW10, 68MW11, and 68MW12 (Figure 2- 1).

Groundwater samples were collected on June 22, 2022 using low-flow sampling techniques described in Worksheet #14 under “Groundwater Sampling” of the UFP-QAPP (Bay West, 2016).

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 DO, specific conductivity, pH, turbidity, temperature, salinity, and ORP. 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 2-2. The groundwater samples were analyzed for arsenic and manganese, and MNA parameters including; sulfate, sulfide, and TOC, while ferrous iron was measured using a field test kit. Arsenic and manganese were analyzed at the fixed base laboratory, Pace Analytical Gulf Coast (Pace), via analytical test method 6020B (SW-846). Sulfate, sulfide, and TOC were analyzed at the fixed base laboratory, Pace, via methods 9056A (SW-846), 9034 (SW-846), and 9060A (SW-846), respectively. Pace is a current Department of Defense Environmental Laboratory Accreditation Program and State of South Carolina accredited laboratory. Ferrous iron was tested in the field via a HACH DR-890 with AccuVac Ampuls, Method 8146. The parameters, analytical methods and applicable MCSs are listed in Table 2-3.

A matrix spike/matrix spike duplicate (MS/MSD) sample was collected from 68MW12 during the 2022 sampling event. A duplicate sample was collected from 68MW08. Groundwater sampling forms are included in Appendix B.

2.1.3 LTM Surface Water Sampling Event

One surface water sample (68SW01) was collected from a tributary of the Cooper River on September 1, 2022. SCDHEC requested that a surface water sample be collected downgradient

Contract FA8903-15-C-0016 2-2 BWJ140078 of 68MW11 and be analyzed for arsenic. Arsenic was analyzed at Pace via analytical test method 6020B (SW-846). The surface water sample was collected with a dip cup and then transferred to the laboratory-provided container.

2.1.4 Water Level Measurements

A groundwater level measurement was collected from each monitoring well located at SWMU 68 (ID068), including those not scheduled for sampling during the LTM event. Groundwater level measurements were collected prior to purging and sampling on June 22, 2022. Water level measurements were made to the nearest 0.01 foot (ft) using an electronic water level meter. The water level meter was decontaminated between monitoring wells to avoid cross-contamination.

Monitoring well construction details and groundwater levels are included in Table 2-1. The monitoring well gauging sheet is included in Appendix B.

2.1.5 Groundwater Flow and Direction

A potentiometric surface map for the June 22, 2022 groundwater level measurement event is included as Figure 2-1. During the June 2022 event, groundwater flowed primarily to the north/northwest toward a tributary of the Cooper River during low tide.

2.1.6 Investigation-Derived Waste

Investigation-derived waste (IDW) generated during the field program included groundwater from well development and purging, and decontamination liquids. The IDW was collected and containerized in 55-gallon drums and combined with purge water from LTM sampling at AOC G (ST042) and SWMU 73 (FL073). The drums are temporarily staged in the Hazardous Waste Storage Area at JBC pending off-site disposal. 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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ANALYTICAL RESULTS

3.1 Nature and Extent of Contamination

Arsenic and manganese exceeded their respective MCSs in one or more samples collected at SWMU 68 (ID068) during the June 2022 sampling event. Arsenic concentrations were greater than the MCS (10 µg/L) in seven of the 10 monitoring wells sampled in 2022 (68MW03, 68MW04, 68MW05, 68MW08, 68MW10, 68MW11, and 68MW12). In 2022, the lowest arsenic concentration that exceeded the MCS was at 68MW12 (13.9 µg/L), and the highest concentration (56 µg/L) was found at 68MW03. The arsenic concentration in the surface water sample, 68SW01, was 2.1 µg/L, which is below the MCS.

Manganese concentrations were greater than the MCS (430 µg/L) in five of the 10 monitoring wells sampled in 2022 (68MW03, 68MW05, 68MW06, 68MW08, and 68MW10). In 2022, the lowest manganese concentration that exceeded the MCS was found at 68MW05 (458J µg/L), and the highest concentration (1,110J µg/L) was at 68MW06. Analytical results in groundwater from 2019 through 2022 are summarized in Table 3-1 and exceedances for the 2022 results are shown on Figure 3-1. The full laboratory reports for 2022 are included as Appendix D.

3.2 Natural Attenuation and Geochemical Parameters

Several measurements and analyses were made to evaluate the geochemistry of the groundwater and its effect on natural attenuation of the COCs. The geochemical parameters are included in Table 3-1 as miscellaneous parameters and field parameters. Several field parameters that are shown on Table 2-2 are duplicated on Table 3-1 for ready comparison.

Geochemistry parameters were measured to evaluate how they relate to high inorganic COC concentrations. In general, half of the ORP results were negative indicating reducing conditions in those wells. The exceptions to the negative ORP were at 68MW01, 68MW02, 68MW03, 68MW04 and 68MW12. Monitoring wells 68MW01 and 68MW02 are located near the shore (a tributary to the Cooper River) and affected by surface water. The other three wells are located in the central and southern portion of the site. The 2022 DO results were all less than 1 mg/L with the exception of 68MW10 which had a DO concentration of 3.07 mg/L. The 2022 DO results are consistent with measurements with previous years.

Ferrous iron concentrations in most wells were generally consistent with those reported in 2019, 2020, and 2021. Ferrous iron concentrations in wells close to the shore were generally less than concentrations from wells further inland. The ferrous iron concentrations in 68MW01, 68MW02, and 68MW 11 were nondetect, 0.08 mg/L, and 0.43 mg/L, respectively, compared to the inland wells’ concentration range of 0.21 to 3.30 mg/L.

Arsenic and manganese concentrations were relatively high, but the lowest concentrations were found in two shore wells, 68MW01 and 68MW02. The arsenic concentrations in 68MW01 and 68MW02 were 6.41J µg/L and 1.73 µg/L, respectively. The manganese concentrations were 58.6J µg/L and 10.6J µg/L, respectively. The lower concentrations in the wells near the shore may be attributable to oxidizing conditions that are present in the surface water.

The wells have TOC concentrations in the range of nondetect (at 1 mg/L) to 2.06J mg/L in 2022.

The TOC concentrations were generally lower for the 2022 event than for previous events. The TOC probably provides a food source for microorganisms and maintains an anaerobic microorganism population. This, in turn, creates reducing conditions as noted by the negative ORP values which favors maintaining iron, manganese, and arsenic in solution. The overlying clay minimizes the amount of precipitation that the reaches the groundwater and minimizes the introduction of oxygen to the groundwater until exposed to surface water.

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The sulfate concentrations were in a narrow range from 27.7 mg/L to 52 mg/L, similar to the 2021 event. The sulfate concentrations are relatively stable throughout the site. Sulfide was only detected in one of the monitoring wells, 68MW11 at 1.4J mg/L. Sulfide concentrations have typically been very low at the site (approximately less than 2.0 mg/L. The narrow range of sulfate concentrations and low concentrations of sulfide could be due to the absence or low numbers of sulfate-reducing microorganisms.

The pH range was 5.89 to 7.03 with most wells in the range of 6.5 to 7.0. This range is slightly acidic which favors maintaining metals, such as iron, manganese, and arsenic, in solution. These results are also consistent with pH measurements collected during previous events.

The total dissolved solids (TDS) concentrations (measured as salinity) are similar to measurements made in 2019, 2020, and 2021. The consistency of the results suggests that there has been no mixing by water from other sources, such as precipitation, or significant change in the geochemistry.

3.3 Data Validation

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 (Bay West, 2016) and the Department of Defense Quality Systems Manual, Version

5.0 (DoD, 2013), as specified in the UFP-QAPP. Non-detected results were reported to the limit of detection (LOD). The following comments were noted in the data validation report.

• The MS percent recovery for manganese was below the quality control limit for sample 68MW12. The MSD percent recovery and MS/MSD relative percent difference for manganese were within the quality control limits. All samples were affected. The detected results reported for manganese in the affected samples were qualified as estimated (J).

• The internal standard percent recoveries for arsenic were below the 60% quality control limit for samples 68MW01 and 68MW04. The detected results reported for arsenic in the affected samples were qualified as estimated (J).

• Detected results reported below the limit of quantitation but above the detection limit were qualified as estimated (J).

Completeness for this LTM event, 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 were found to be acceptable for their intended use. The data validation report is included in Appendix E.

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SUMMARY AND RECOMMENDATION

The purpose of annual LTM event at SWMU 68 (ID068) is to comply with the requirements of the RCRA Permit. The year 4 annual groundwater monitoring event was conducted in June 2022, the surface water sample was collected in September 2022, and the LUC inspection was conducted on June 22, 2022. Appendix A includes a summary of historical groundwater data collected at SWMU 68 (ID068). Table 3-1 provides a summary of detected analytes in groundwater from the August 2019 through June 2022 sampling events. The 2022 surface water result is also included on this table. A brief discussion of data trends is included below.

Arsenic exceeded the MCS in seven of the 10 wells sampled in 2022, which is relatively consistent with analytical results from 2019, 2020, and 2021. Arsenic was detected at a concentration greater than the MCS (10 µg/L) at 68MW01 at a concentration of 13.8 µg/L in 2011. Arsenic was detected at concentrations less than the MCS in this well in 2012, 2016, 2019, 2020, 2021, and 2022.

Arsenic was detected at 27.7 µg/L in 68MW02 in 2011 and has not been detected at a concentration greater than 2.5 µg/L since that time. The arsenic concentration at 68MW03 has increased from 21.6 µg/L in 2011 to 59.6 µg/L in 2016 to maximum concentrations of 73 µg/L and

76.3 µg/L in 2019 and 2020, respectively. The arsenic concentration decreased in 68MW03 to

61.9 µg/L during the July 2021 sampling event and 56 µg/L during the June 2022 sampling event.

The arsenic concentration at 68MW04 and 66MW05 has remained stable or decreased from 2011 to 2022 with concentrations greater than the MCS during most sampling events. The arsenic concentration at 68MW06 has remained relatively stable from 2012 to 2019 but decreased to 8.75 µg/L in 2020 which is below the MCS. The arsenic concentration in 68MW06 was 12.6 µg/L in July 2021 and decreased to 6.3 µg/L in June 2022. Arsenic concentrations peaked at 68MW08 in 2016 (35.8 µg/L) and decreased to 30.8 µg/L in 2019 and 26.4 µg/L in 2020. The arsenic concentration in 68MW08 was 27.8 µg/L and 23 µg/L in July 2021 and June 2022, respectively.

Arsenic exceeded the MCS in 2019 through 2022 but the concentrations have remained relatively stable or show a decreasing trend. Arsenic concentrations were also greater than the MCS in 2016, 2019, 2020, 2021, and 2022 at 68MW10 (2022 concentration of 25.8 µg/L), 2019, 2020, 2021 and 2022 at 68MW11 (2022 concentration of 37.2 µg/L), and 2020, 2021 and 2022 at 68MW12 (2022 concentration of 13.9 µg/L). The arsenic concentration was less than the MCS for the surface water sample that was collected (68SW01) and was detected at 2.1 µg/L. Figure 4-1 illustrates arsenic concentrations over time from 2011 through 2021.

Manganese exceeded the MCS (430 µg/L) in five of the 10 wells sampled in 2022 and did not exceed the MCS in the two wells that were installed in 2019 (68MW11 and 68MW12). The concentration of manganese exceeded the MCS in 68MW03 and decreased from 734 µg/L in 2016 to 616 µg/L in 2020 and increased to 703 µg/L in 2021 and 678J µg/L in 2022. The manganese concentration in 68MW05 was below the MCS in 2019 and 2020 and was detected at 800 µg/L in 2021 and 458J µg/L in 2022. Manganese concentrations exceeded the MCS at 68MW06, 68MW08, and 68MW10 in 2016, 2019, 2020, 2021, and 2022 with concentrations in 2022 of 1,100J µg/L, 484J µg/L, and 816J µg/L, respectively. The highest manganese concentrations at the site have been detected at 68MW06 and the concentrations have remained relatively stable and above the MCS. Figure 4-2 illustrates manganese concentrations over time from 2016 through 2022.

The results of the geochemical analyses and measurements indicate anoxic reducing conditions at the site that are favorable to maintaining iron, manganese, and arsenic in solution. Oxidizing conditions appear to exist close to the shore (a tributary to the Cooper River) which allows for precipitation of manganese and arsenic. No criteria were available for exceedance determination for such miscellaneous analytes and they are appropriately tabulated in Table 3-1.

Contract FA8903-15-C-0016 4-2 (R-05/26/22) BWJ140078

It is recommended that annual LTM continue and the next event is tentatively scheduled for June 2023.

Contract FA8903-15-C-0016 BWJ140078

REFERENCES

Bay West, 2016. 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.

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

TEC-BSC Joint Venture, 2013. DRAFT 2012 Annual Monitoring Report, SWMU 68 South Annex Building 3637, General Purpose Warehouse Waste Tank, Joint Base Charleston Weapons, 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 68 (ID068), JBC Weapons, South Carolina, July.

Tetra Tech, 2017. Basewide Background Study Report, Joint Base Charleston Weapons, South Carolina, March.

Tetra Tech, 2018a. Statement of Basis for Tank Closure or Removal, Monitored Natural Attenuation and Land Use Controls for Groundwater Solid Waste Management Unit 68 (ID068) South Annex Building 3637, General Purpose Warehouse Waste Tank. Joint Base Charleston Weapons, South Carolina, December.

Tetra Tech, 2018b. Corrective Measures Study Report Solid Waste Management Unit 68 (ID068), Performance-Based Remediation, Joint Base Charleston Weapons, South Carolina. Final, May.

Tetra Tech, 2020a. 2019 Annual Long-Term Monitoring Report Solid Waste Management Unit 68 (ID068), Performance-Based Remediation, Joint Base Charleston Weapons, South Carolina. Final, April.

Tetra Tech, 2020b. 2020 Annual Long-Term Monitoring Report Solid Waste Management Unit 68 (ID068), Performance-Based Remediation, Joint Base Charleston Weapons, South Carolina. Draft Final, November.

Tetra Tech, 2022, 2021 Year 3 Annual Long-Term Monitoring Report Solid Waste Management Unit 68 (ID068), Performance-Based Remediation, Joint Base Charleston Weapons, South Carolina. Final, June.

USEPA, 2017. National Functional Guidelines for Organic Superfund Methods Data Review (SOM02.4) EPA-540-R-2017-002, January.

WPNSTA Charleston, 1997. RCRA Facility Assessment for Fourteen New Units at Naval Weapons Station Charleston (draft). Naval Weapons Station Charleston Base Civil Engineering Department, December.

Figures

Former Naval Station Charleston

Joint Base Charleston Weapons

COOPER

RIVER

WA

ND

O

RIV

ER

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 Rang e

College P ark

Old Dairy

Cypress Gardens

Harbor View

Long Point

Crowfie ld

Fort Johnson

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 47\FIGURE_1-1_LOCATION_MAP.MXD 2/28/2017

CONTRACT NUMBER

APPROVED BY

APPROVED BY

DATE

DATE

FIGURE NO. REV

1-1

LOCATION MAP

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

AS NOTED

SCALE

DATE

DATECHECKED BY

DRAWN BY

J. ENGLISH 02/06/09

P.CHURCHILL 02/27/17

DATEREVISED BY

J.MADDEN 02/27/17

Charleston, SC

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 C

O.

BE

RK

EL

EY

CO

CSX RAILROAD

SOUTH SIDE

SWMU 68

³

1 10 Miles

JAX: C:\GIS\Charleston\MXD\2016 Field Data\SWMU 68\May2017\Figure_1-2_SWMU68_fac_loc.mxd

SITE LOCATION MAP

SWMU 68 - SOUTH ANNEX BULDING 3637, GENERAL PURPOSE WAREHOUSE TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

CTO

1-2

FIGURE NUMBER

DATEDRAWN BY

J.MADDEN 01/08/20

DATECHECKED BY

L.ADAMS 01/08/20

Road

Site Boundary Railroad Tracks

Installation Boundary County Line

Legend

SWMU 68

Approximate Location of

Historical Septic Tank.

9 9

³ JAX C:\GIS\CHARLESTON\MXD\2016 FIELD DATA\SWMU 68\MAY2017\FIGURE_1-3_SWMU68_2016_FEATURES.MXD 01/10/20 JM

50 500 Feet

HISTORICAL FEATURES

SWMU 68 - SOUTH ANNEX BULDING 3637

GENERAL PURPOSE WAREHOUSE WASTE TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Historical Open Storage Area

Legend

Topographic Contour (1ft Inverval)

SWMU 68 Boundary (dashed where estimated due to insufficient data with no exceedances) Original Site Boundary of SWMU 68

1-3

FIGURE NUMBER

DATEDRAWN BY

CTO

J.MADDEN 01/10/20

DATECHECKED BY

F.RAMSER 01/10/20

Aerial provided by ArcGIS World Imagery

Approximate Location of Historical Septic Tank

+U

+U +U

+U

+U

+U +U

+U

+U

+U

+U

PERIMETER ROADAVENUE D

GOOSE CREEK

POND

SWMU 68

SWMU 20

TRIBUTARY TO

GOOSE CREEK

68MW11

(2.63)

68MW12

(2.94)

2.70

2.80 2.90 3.00

3.10

3.20

3.20 3.10 3.10

2.70 2.80

2.90 3.00 3.10

68MW10

(3.31)

68MW09

(3.13)

68MW08

(2.95)

68MW07

(2.68)

68MW06

(3.41) 68MW05

(3.21)

68MW04

(3.10)

68MW03

(3.05)

68MW02

(3.12) 68MW01

(3.09)

32623260 3261

3125A

36783679

10 5

1 ³ JAX C:\GIS\CHARLESTON\MXD\2016 FIELD DATA\SWMU 68\MAY2017\FIGURE_2-2_SWMU68_GW_ELEV_LOWTIDE2022.MXD 12/22/22 JM

100 1000 Feet

GROUNDWATER ELEVATION MAP - JUNE 22, 2022 - LOW

TIDE SWMU 68 - SOUTH ANNEX BULDING 3637

GENERAL PURPOSE WAREHOUSE WASTE TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Historical Open Storage Area

Building Road Historical Fence Line Historical Railroad Spur

Legend

Groundwater Elevation (ft msl)(3.80)

Groundwater Elevation Contour (0.1ft interval)

Groundwater Flow Direction

Topographic Contour (1-foot Inverval)

&< Monitoring Well Location

SWMU 68 Boundary (dashed where estimated due to insufficient data with no exceedances) Original Site Boundary of SWMU 68 Other SWMU Site Boundaries

2-1

FIGURE NUMBER

DATEDRAWN BY

CTO

J.MADDEN 12/22/22

DATECHECKED BY

L.ADAMS 12/22/22

Surface Water Flow Direction

Tributary to Goose Creek

Projection/Geographic Reference System:

1983 North American Datum, South Carolina (Feet)

+U+U

+U

+U

+U+U

+U

+U

+U

+U

GOOSE CREEK

TRIBUTARY TO GOOSE CREEK

68MW08 ORIG DUP

ARSENIC 23.0 22.4

MANGANESE 484 J 478 J

68MW07

Not sampled in 2019/2020/2021, 2022, no exceedances previously

68MW06

MANGANESE 1100 J

68MW05

ARSENIC 28.9

MANGANESE 458 J

68MW04

ARSENIC 15.6 J

68MW03

ARSENIC 56.0

MANGANESE 678 J

68MW02

No Exceedance

68MW01

No Exceedance

PERIMETER ROAVENUE D

GO O SE CREEK

SWMU 68

SWMU 20

68MW11

ARSENIC 37.2

68MW12

ARSENIC 13.9

68MW10

ARSENIC 25.8

MANGANESE 816 J

AD

8MW09

Not sampled in 2019/2020/2021, 2022, no exceedances previously

PO ND

68SW01

No Exceedance

³ JAX C:\GIS\CHARLESTO N\MXD\2016 FIELD DATA\SWMU 68\MAY 2017\FIGURE_3-1_SWMU68_JUNE2022_EXCEEDANCES.MXD 01/17/23 JM

100 1000 Fe e t

His torical O pe n Storage Are a

Legend

Topographic Contour (1ft Inve rval)

Monitoring We ll Location SWMU 68 Bound ary (d as he d whe re e s timate d d ue to ins uffic ie nt d ata with no e xc e e d anc e s ) O riginal Site Bound ary of SWMU 68 O the r SWMU Site Bound arie s

3-1

FIGURE NUMBER

DATEDRAWN BY

CTO

J.MADDEN 01/17/23

DATECHECKED BY

L.ADAMS 01/17/23

MCS

ARSENIC

MANGANESE

MCS = Me d ia Cle anup Stand ard Re s ults and MCS are re porte d in μg/L

Ae rial provid e d b y Google Earth, d ate d 4/2021

Surfac e Wate r Sample!?

LEAH.ADAMS

Text Box

ANALYTE EXCEEDANCES IN GROUNDWATER AND SURFACE

WATER JUNE-SEPTEMBER 2022

SWMU 68 - SOUTH ANNEX BUILDING 3637

GENERAL PURPOSE WAREHOUSE WASTE TANK

JOINT BASE CHARLESTON WEAPONS

CHARLESTON, SOUTH CAROLINA

Jul‐09 Nov‐10 Apr‐12 Aug‐13 Dec‐14 May‐16 Sep‐17 Feb‐19 Jun‐20 Oct‐21 Mar‐23

Ar se ni c Co nc en tr at io n (m ic ro gr am s/ Li te r)

Sample Date

Figure 4‐1: Arsenic Concentration in Groundwater vs. Time

68MW01

68MW02

68MW03

68MW04

68MW05

68MW06

68MW08

68MW10

68MW11

68MW12

May‐16 Sep‐17 Feb‐19 Jun‐20 Oct‐21 Mar‐23

M an ga ne se C on ce nt ra tio n (m ic ro gr am s/ Li te r)

Sample Date

Figure 4‐2: Manganese Concentration in Groundwater vs. Time

68MW01

68MW02

68MW03

68MW04

68MW05

68MW06

68MW08

68MW10

68MW11

Tables

Depth to Water (ft btoc)

Groundwater Elevation (ft msl)

Depth to Water (ft btoc)

Groundwater Elevation (ft msl)

Depth to Water (ft btoc)

Groundwater Elevation (ft msl)

Depth to Water (ft btoc)

Groundwater Elevation (ft msl)

Depth to Water (ft btoc)

Groundwater Elevation (ft msl)

68MW01 05/21/11 9.07 8.77 10 - 20 -0.93 -10.93 5.68 3.09 5.37 3.40 5.20 3.57 5.21 3.56 5.57 3.20 68MW02 05/21/11 9.83 12.58 10 - 20 -0.17 -10.17 9.46 3.12 9.09 3.49 8.99 3.59 9.00 3.58 9.45 3.13 68MW03 05/21/11 11.41 11.25 11 - 21 0.41 -9.59 8.20 3.05 7.76 3.49 7.71 3.54 7.72 3.53 8.16 3.09 68MW04 05/21/11 10.77 13.46 10 - 20 0.77 -9.23 10.36 3.10 9.80 3.66 9.86 3.60 10.10 3.36 10.29 3.17 68MW05 05/21/11 6.24 8.47 5 - 15 1.24 -8.76 5.26 3.21 4.81 3.66 4.81 3.66 4.94 3.53 5.19 3.28 68MW06 05/21/11 9.73 12.12 8 - 18 1.73 -8.27 8.71 3.41 8.29 3.83 8.07 4.05 8.20 3.92 8.52 3.60 68MW07 05/21/11 4.30 6.95 9 - 19 -4.70 -14.70 4.27 2.68 2.75 4.20 2.14 4.81 2.96 3.99 3.62 3.33 68MW08 05/21/11 8.01 7.77 9 - 19 -0.99 -10.99 4.82 2.95 4.34 3.43 4.32 3.45 4.30 3.47 4.78 2.99 68MW09 10/11/16 8.37 7.98 10 - 20 -1.63 -11.63 4.85 3.13 4.43 3.55 4.29 3.69 4.48 3.50 4.65 3.33 68MW10 10/11/16 9.27 11.65 7 - 17 2.27 -7.73 8.34 3.31 7.89 3.76 7.79 3.86 7.98 3.67 8.23 3.42 68MW11 08/19/19 8.95 8.37 10 - 20 -1.05 -11.05 5.74 2.63 5.25 3.12 5.29 3.08 NM NM 5.71 2.66 68MW12 08/20/19 9.41 12.12 10 - 20 -0.59 -10.59 9.18 2.94 8.80 3.32 8.69 3.43 NM NM 9.11 3.01 ft msl- feet below mean sea level ft btoc- feet below top of casing ft bgs- feet below ground surface NM- not measured

7/14/21 High Tide06/22/2022 Low Tide 08/19/2019 High Tide

TABLE 2-1

Well Construction Information and Groundwater Level Measurements SWMU 68 - South Annex Building 3637 General Purpose Warehouse Waste Tank

Joint Base Charleston Weapons, South Carolina

Well Number Ground

Elevation (ft msl)

Top of Riser

Elevation (ft msl)

Screen Interval (ft bgs)

Top of Screen Elevation (ft msl)

Bottom of Screen

Elevation (ft msl)

Date Installed

08/22/2016 Low Tide6/24/2020 Mid-Tide

Table 2-2

Summary of Groundwater Quality Parameter Data and Field Test Kit Measurements SWMU 68 - South Annex Building 3637 General Purpose Warehouse Waste 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)

68MW01 6/22/2022 6.95 0.632 0.19 5.90 28.28 47 0.2 0.00

68MW02 6/22/2022 5.89 0.123 0.04 1.80 24.84 98 0.1 0.08

68MW03 6/22/2022 6.97 0.87 0.27 1.84 27.88 19 0.4 1.08

68MW04 6/22/2022 6.54 0.424 0.03 9.0 29.29 43 0.2 0.21

68MW05 6/22/2022 6.