B.08 GFI JB CHS PBR CS023 (SWMU 23) Draft 2021 LUC Report redline.pdf

DRAFT

2021 Land Use Controls Report

PERFORMANCE-BASED REMEDIATION

Solid Waste Management Unit 23 (CS023) Joint Base Charleston Weapons

South Carolina

Contract FA8903-15-C-0016 May June 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:

AECOM

4016 Salt Pointe Parkway

North Charleston, South Carolina 29405

With Teaming Partners:

Land Use Controls Report (2021)

SWMU 23 (CS023)

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 i BWJ140078

Certification Page

Registered South Carolina Professional Geologist

Certification

By affixing my seal to this report, I certify that the data and interpretations stated in this, 2021 Land Use Controls Report for SWMU 23 (CS023), Joint Base Charleston Weapons, South Carolina, are true and accurate to the best of my knowledge. I further certify that I am registered to practice geology in the State of South Carolina and that it is within my professional expertise to verify the correctness of this information.

Eva Rasdal Moore, PG. Date Registration Number 2462

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 ii BWJ140078

TABLE OF CONTENTS

LIST OF FIGURES .................................................................................................................... iii LIST OF TABLES ...................................................................................................................... iii LIST OF APPENDICES ............................................................................................................. iii ACRONYMS AND ABBREVIATIONS ....................................................................................... iv

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

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

1.2 Site History and Previous Investigations .................................................................. 1-2

1.2.1 Installation Assessment ....................................................................................... 1-2

1.2.2 Initial Assessment Study ...................................................................................... 1-2

1.2.3 Interim RCRA Facility Assessment ...................................................................... 1-2

1.2.4 Confirmatory Sampling ........................................................................................ 1-2

1.2.5 RCRA Facility Investigation ................................................................................. 1-3

1.2.6 Supplemental RCRA Facility Investigation ........................................................... 1-3

1.2.7 Periodic Monitoring .............................................................................................. 1-4

1.2.8 Facility Conceptual Site Model ............................................................................. 1-4

1.2.9 RFI Addendum .................................................................................................... 1-4

1.2.10 Interim Measures ................................................................................................. 1-5

1.2.11 Bench Scale Study .............................................................................................. 1-5

1.2.12 Corrective Measures Study and Statement of Basis ............................................ 1-5

1.2.13 Land Use Control Implementation Plan ................................................................ 1-6

1.3 Report Organization................................................................................................. 1-6

2.0 ANNUAL MONITORING ACTIVITIES .......................................................................2-1

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

2.1.1 Groundwater Sample Collection and Handling Procedures .................................. 2-1

2.1.2 Surface Water Sample Collection and Handling................................................... 2-1

2.1.3 Laboratory Submittal and Analysis ....................................................................... 2-2

2.2 Data Evaluation and Usability .................................................................................. 2-3

2.3 Investigation Derived Waste Management ............................................................... 2-3

2.4 Annual Landfill Inspection and Maintenance ............................................................ 2-3

3.0 MONITORING RESULTS ..........................................................................................3-1

3.1 2019/2020 Analytical Results ................................................................................... 3-1

3.1.1 Arsenic and Cobalt Analytical Results .................................................................. 3-1

3.1.2 Summary of Analytes Exceeding Project Action Levels ....................................... 3-2

3.2 2021/2022 Analytical Results ................................................................................... 3-2

3.2.1 Arsenic and Cobalt Analytical Results .................................................................. 3-2

3.2.2 Summary of Analytes Exceeding Project Action Levels ....................................... 3-3

4.0 CONCLUSIONS AND RECOMMENDATIONS ..........................................................4-1

4.1 Conclusions ............................................................................................................. 4-1

4.2 Recommendations ................................................................................................... 4-1

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

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 iii BWJ140078

List of Figures

Figure 1 Joint Base Charleston Weapons Location Map Figure 2 SWMU 23 Location Map Figure 3 SWMU 23 Site Vicinity Map Figure 4 SWMU 23 Site Features Map Figure 5 SWMU 23 Groundwater Contour Map (October 2019) Figure 6 SWMU 23 Groundwater Contour Map (November 2021) Figure 7 SWMU 23 Arsenic Isoconcentration Map (October 2019) Figure 8 SWMU 23 Cobalt Isoconcentration Map (October 2019) Figure 9 SWMU 23 Arsenic and Cobalt Concentrations in Surface Water (October 2019) Figure 10 SWMU 23 Arsenic and Cobalt Concentrations in Surface Water (February 2020) Figure 11 SWMU 23 Arsenic Isoconcentration Map (November 2021) Figure 12 SWMU 23 Cobalt Isoconcentration Map (November 2021) Figure 13 SWMU 23 Arsenic and Cobalt Concentrations in Surface Water (November

2021) Figure 14 SWMU 23 Arsenic and Cobalt Concentrations in Surface Water (March 2022)

List of Tables Table 1 Well Construction Data Table 2 Groundwater Elevation Data Table 3 Groundwater Field Parameters Table 4 Groundwater and Surface Water Monitoring Matrix Table 5 Summary of Analytical Results in Groundwater – October 2019 Table 6 Summary of Analytical Results in Surface Water – October 2019 and February

Table 7 Summary of Analytical Results in Groundwater – November 2021 Table 8 Summary of Analytical Results in Surface Water – November 2021 and March

Table 9 Historical Arsenic and Cobalt in Groundwater Table 10 Historical Arsenic and Cobalt in Surface Water

List of Appendices Appendix A Field Documentation Appendix B Laboratory Analytical Packages Appendix C Data Validation Reports Appendix D IDW Documentation Appendix E Landfill Inspection Documentation Appendix F Historical Analytical Graphs

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 iv BWJ140078

ACRONYMS AND ABBREVIATIONS

µg/L............. micrograms per liter ABB-ES....... ABB Environmental Services, Inc.

AFCEC ....... Air Force Civil Engineer Center CAMP ......... corrective action management plan CMS ............ corrective measures study COPC ......... chemical of potential concern CSM ............ conceptual site model DO .............. dissolved oxygen DoD ............ Department of Defense EHC-M® ...... PeroxyChem EHC Metals ft ................. feet IAS .............. initial assessment study IDW ............. investigation-derived waste IM ............... interim measure IP ................ injection point JBC ............. Joint Base Charleston LCS ............. laboratory control sample LCSD .......... laboratory control sample duplicate LTM ............ long-term monitoring LUC ............ land use controls LUCIP ......... land use controls inspection plan MCL ............ maximum contaminant level MDL ............ method detection limit MS .............. matrix spike

MSD ............ matrix spike duplicate ORP ............ oxidation-reduction potential PAL ............... project action level PCB .............. polychlorinated biphenyl RCRA ............ Resource Conservation and

Recovery Act RFA ............... RCRA Facility Assessment RFI ................ RCRA Facility Investigation RPD .............. relative percent difference SCDHEC ....... South Carolina Department of Health and Environmental Control

SPAWAR ...... Space and Naval Warfare Systems Command

SVOC ............ semi-volatile organic compound

SWMU........... solid waste management unit TtNUS ........... Tetra Tech NUS, Inc.

UFP-QAPP .... Uniform Federal Policy –

Quality Assurance Project Plan

US ................. United States USEPA .......... United States Environmental

Protection Agency VOC .............. volatile organic compound ZVI ................ zero-valent iron

Joint Base Charleston Weapons, South Carolina

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

1.0 INTRODUCTION

This Annual Report for Solid Waste Management Unit (SWMU) 23 at Joint Base Charleston (JBC) Weapons, South Carolina, has been prepared in accordance with the Resource Conservation and Recovery Act (RCRA) Permit Number SC8 170 022 620 issued to JBC Weapons by South Carolina Department of Health and Environmental Control (SCDHEC) in conjunction with Region 4 of the United States Environmental Protection Agency (USEPA). This document has been prepared under Air Force Civil Engineer Center (AFCEC) Contract Number FA8903-15-C-0016 in support of the JBC Weapons Environmental Restoration Program.

This Annual Report documents the completion of annual groundwater and surface water monitoring, and landfill inspection and maintenance conducted to address groundwater contaminants per the Uniform Federal Policy – Quality Assurance Project Plan (UFP-QAPP) and Corrective Measures Study (CMS) / Interim Measures (IM) Work Plan (CMS Work Plan, AECOM, 2016) for both 2019 and 2021. Groundwater monitoring procedures were performed following Uniform Federal Policy – Quality Assurance Project Plan, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina (Bay West, 2016a).

1.1 Site Description

JBC Weapons is located ten miles north of Charleston, South Carolina, approximately 16 miles inland from the Atlantic Ocean (Figure 1). The facility is situated in two counties, Berkeley and Charleston, and occupies 16,868 acres. The eastern section of the facility is bordered by the Cooper River and the Back River; the western section is bordered by the CSX Railroad. The facility, formerly Naval Weapons Station Charleston, has been under Air Force direction since October 1, 2010, and renamed JBC Weapons.

JBC Weapons is divided into three sections: the northernmost section (referred to as Northside and formerly referred to as the Polaris Missile Facility Atlantic Fleet Area), the central section (referred to as Southside), and the southernmost section (referred to as the South Annex). The areas are managed separately by the Air Force and are collectively referred to as JBC Weapons.

SWMU 23 is located in the South Annex between Perimeter Road and Goose Creek and is heavily vegetated by marsh grass (Figure 2). The former landfill extends approximately 650 feet

(ft) in a north-south direction along Perimeter Road and approximately 575 ft to the East from Perimeter Road toward Goose Creek (Figures 3 and 4). The Goose Creek tidal marsh borders the former landfill on the east side. A 6-ft-high chain link fence borders the site on the western boundary and a gate bars access to the property from the paved road. Well construction data is presented as Table 1.

SWMU 23 is approximately 10 acres in size and has an unpaved access road that extends from Perimeter Road to the Goose Creek tidal marsh. The access road ends at the eastern edge of the SWMU at an L-shaped configuration of metal storage containers used by the Space and Naval Warfare Systems Command (SPAWAR) to support operation and maintenance of an adjacent antenna array. The SPAWAR antennas are located at the ends of five wooden piers that extend up to approximately 160 feet from the eastern border of the SWMU 23 site into the tidal marsh.

The landfill was used for disposal of construction material and other debris generated at the South Annex from 1918 until sometime between 1942 and 1978. Conflicting information is available on the discontinuance of landfill use. Reported dates of cessation of the landfill are

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 1-2 BWJ140078

1942 in the interim RCRA Facility Assessment (Kearney/Centaur, 1988); prior to 1952 in the draft Confirmation Sampling Report (ABB Environmental Services, Inc. [ABB-ES], 1993); and 1978 in the Initial Assessment Study (Harmon Engineering and Testing, 1984). In addition, an assessment conducted in 1977 of the Charleston Army Depot (currently the South Annex) indicated that the landfill was used on an as-needed basis (United States [US] Army, 1977).

When the landfill was in operation, combustible materials were burned, and the remaining residue was covered with soil. Materials reportedly disposed included wood, packing and shipping debris, tires, and household refuse (Harmon Engineering and Testing, 1984; US Army, 1977). The landfill also reportedly received sludge from the industrial wastewater treatment plant (Kearney/Centaur, 1988).

1.2 Site History and Previous Investigations

1.2.1 Installation Assessment

Several investigations have been conducted at JBC Weapons (formerly Naval Weapons Station Charleston) that have included SWMU 23. An installation assessment of Charleston Army Depot (now referred to as the South Annex) was conducted to search for, identify, and assess actual or potential chemical, biological, or radiological contaminant migration at the Charleston Army Depot and to identify any immediate on-post safety problems (US Army, 1977). The assessment indicated that a sanitary landfill in the western portion of the marsh, bordering Perimeter Road (corresponding to the approximate location of SWMU 23), contained old building materials, packing and shipping debris, and tires. Combustible materials reportedly were burned, and the remainder of debris covered with soil. The landfill was operated on an as-needed basis. The assessment reported that no known contaminants had been placed in the landfill.

1.2.2 Initial Assessment Study

An Initial Assessment Study (IAS) for JBC Weapons was completed in January 1984 (Harmon Engineering and Testing, 1984). The IAS was prepared to identify and assess potential sites posing a threat to human health or the environment from contamination from past hazardous materials operations. Based on information from historical records, aerial photographs, field inspection, and personnel interviews, 18 potentially contaminated sites were identified at JBC Weapons and were evaluated in the IAS. Five of the 18 sites were recommended for further study (as part of a Confirmation Study) based on their potential threat. SWMU 23 (identified as Site 17 in the IAS) was not recommended for further study in the IAS because of the innocuous nature of the waste.

1.2.3 Interim RCRA Facility Assessment

An Interim RCRA Facility Assessment (RFA) for JBC Weapons was conducted in 1988 (Kearney/Centaur, 1988) to update the IAS performed in 1984. The interim RFA was required because JBC Weapons began operating under a RCRA interim status. Twenty-five SWMUs and eight areas of concern were identified at JBC Weapons and evaluated in this report. Because of the uncertainty of what was landfilled at SWMU 23, the Interim RFA recommended further action at SWMU 23 to determine whether any hazardous waste constituents were present.

1.2.4 Confirmatory Sampling

Sampling was conducted at SWMU 23 in 1993 as part of the Confirmatory Sampling at Corrective Action Management Plan (CAMP) Group B sites. A draft report was issued that was never finalized because additional field work was warranted. Based on the results of the confirmatory sampling the Supplemental Confirmatory Sampling Work Plan for CAMP Group B was prepared (ABB-ES, 1997). An addendum to the work plan was issued in 1997; the work

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 1-3 BWJ140078 plan with addendum is referred to as the RCRA Facility Investigation Work Plan for SWMUs 2, 21, and 23.

1.2.5 RCRA Facility Investigation

The RFI field work was performed in 1997 (TtNUS, 2000a). The RFI investigation included soil, surface water and sediment sampling as well as installation of five groundwater wells and groundwater sample collection. Aquifer pumping tests were performed at each well.

A few sporadic detections of organic constituents were encountered in site soils. Inorganic constituents in soil were largely attributable to naturally occurring, with the exception of sodium which is likely the result of saltwater intrusion. Maximum concentrations of antimony, arsenic, cadmium and silver exceeded background groundwater concentrations and are potentially related to the landfill.

Elevated concentrations of inorganic constituents were present in site sediment and surface water. A few organic constituents were also present. There does not appear to be a correlation with the soil/groundwater data. Unfortunately, background surface water and sediment data are not available to assess whether the contaminant concentrations detected in the surface water and sediment data are site related. For all media sampled, there was no one contaminant standing out as being site related.

No significant potential human health risks are associated with exposure to surface soil, surface water, and sediment at SWMU 23 under current and future potential land use. Direct contact with subsurface soil and groundwater is not anticipated. A majority of the inorganic constituents detected in the site soil (surface and subsurface) samples are present at concentrations indicative of naturally occurring constituents.

No potential ecological risks are associated with surface soil or groundwater. Only tin in groundwater is of potential concern but it is unlikely that tin is present entirely as tributyl-tin, the most toxic form. Inorganic constituents in sediments appear to pose low to moderate potential ecological risks to benthos and semi-aquatic receptors.

It was concluded that there are limited groundwater impacts into the surrounding marsh from SWMU 23. A direct exposure route between groundwater and potential surface receptors was not established. The groundwater is saline and is not expected to be used as a potable water source.

1.2.6 Supplemental RCRA Facility Investigation

The RFI was considered incomplete and additional samples were collected in October 1999 and documented in the Supplemental RFI (TtNUS, 2000b). The Supplemental RFI included an additional nine surface water and sediment samples from the tidally influenced Goose Creek marsh. Surface water and sediment samples were co-located. Each of the existing monitoring wells was also sampled.

The Supplemental RFI summarized all data collected to date at SWMU 23. The results of this evaluation indicate that the majority of metals detected at SWMU 23 are near or below the background concentrations for each of the media sampled with the exceptions being less than double the background concentrations. There was a general decrease in metals concentrations detected at SWMU 23 compared to previous investigations.

Surface water and sediment samples were collected to determine the full extent of ecological impacts from SWMU 23. Results from the additional sample collection indicated a limited impact on the marsh from contaminants originating from SWMU 23 and an order of magnitude decrease in metals concentrations in the marsh relative to previous investigations. With the

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 1-4 BWJ140078 exception of copper, concentrations of metals detected in sediment samples during the Supplemental RFI investigation were less than historical and background concentrations (upgradient samples established as background in RFI). Based on the results of the Supplemental RFI investigation and previous investigations, the impact to the marsh from SWMU 23 is negligible.

1.2.7 Periodic Monitoring

Following the 2000 RFI Addendum, periodic monitoring was performed through 2012. The first year of monitoring (2002) included quarterly sample collection documented in an annual report.

Two additional wells (23MW06 and 23MW07) were installed in 2002 prior to the start of quarterly monitoring. Arsenic was identified as the analyte of most concern in groundwater.

Based on discussions during the March 2004 partnering meeting, the analyte list was modified to include pesticides/polychlorinated biphenyls, and well 23MW01 was eliminated from future monitoring (TtNUS, 2004).

In 2007, the 5th year of annual monitoring was performed (Terraine, 2007). Groundwater sampling was conducted quarterly for the first two years of the monitoring program. During the third, fourth, and fifth years of long-term monitoring (LTM), groundwater samples were collected semi-annually. Based on Year 5 analytical results, arsenic was considered the analyte of most concern. Arsenic was detected in three wells (23MW03, 23MW05, and 23MW07) at concentrations exceeding the maximum contaminant level (MCL). Based on review of five years of quarterly and semi-annual monitoring, it was determined that no seasonal trends were observed. Annual monitoring was recommended; the analyte list will continue to include polychlorinated biphenyls (PCBs) which will be collected at alternating locations (23MW04 and 23MW07) on the downgradient side of the landfill.

In the 2012 monitoring report (TEC-BSC, 2014), arsenic and cobalt were established as the constituents of potential concern (COPCs) in groundwater. Pesticides and PCBs were analyzed at two downgradient locations (23MW04 and 23MW07). Recommended were annual monitoring and a revision of the Basewide background study to define the background metals concentrations in the various hydrologic environments at the facility; and continue monitoring for total and dissolved metals to evaluate metals mobility in groundwater.

1.2.8 Facility Conceptual Site Model

A facility-wide conceptual site model (CSM) was prepared (AECOM, 2014) which included a tidal study at SWMU 23. It was determined that there is no observable response to tidal changes in water levels at the site.

1.2.9 RFI Addendum

The RFI Addendum (AECOM, 2018a) documents the completion of additional investigation efforts to define the previously identified groundwater plumes for arsenic and cobalt. SCDHEC requested additional investigation to delineate arsenic and cobalt in groundwater along the southern boundary of the site, since arsenic and cobalt were identified as COPCs in groundwater. In August 2016, a total of three monitoring wells (23MW08, 23MW09, and 23MW10) were installed at SWMU 23 to delineate the horizontal extent of COPCs in groundwater (Figure 4). The three new monitoring wells are located at the edge of the landfill surface (adjacent to the marsh) and define the horizontal extent of the groundwater plume. Well 23MW10 does not have elevated concentrations of either arsenic or cobalt in groundwater and defines the extent of the plume to the northeast. Wells 23MW08 and 23MW09 define the plume extent to the south and southeast at the landfill boundary (adjacent to the marsh). SCDHEC

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 1-5 BWJ140078 approved the RFI Addendum in their letter dated June 20, 2018, confirming that RFI activities are completed at SWMU 23.

1.2.10 Interim Measures

Interim Measure (IM) injections were performed at temporary injection points (IPs) in the vicinity of 23MW05, 23MW08, 23MW09, and 23MW10 in March 2017 as documented in the IM Completion Report (AECOM, 2018b). The objective of the IM was to evaluate the applicability of PeroxyChem EHC Metals (EHC-M®) as an amendment to remediate low levels of metals in groundwater along the downgradient side of the landfill. Post-injection groundwater monitoring was performed in June, September, and December 2017 and March 2018. Post-injection monitoring results are presented in the IM Completion Report (AECOM, 2018b).

Contaminant concentrations fluctuated following injections with initial increases of arsenic in wells 23MW07, 23MW08, and 23MW09. Arsenic is more soluble under reducing conditions and therefore more mobile, which may account for the initial increases of this COPC. Increased mobility means it is more likely to encounter and potentially adsorb to/precipitate with iron sulfide. However, the oxidation reduction potential (ORP) did not remain at low enough levels to sustain the conditions necessary to decrease metals concentrations (i.e., iron, sulfur, and arsenic were not in the species or chemical form necessary to react), which may explain why arsenic concentrations did not decrease to below the project action level (PAL) at any of the target wells. Cobalt concentrations have decreased to below PALs at all wells except 23MW05, however a consistent response was not observed at all wells located within the injection area.

1.2.11 Bench Scale Study

A Bench Scale Study was performed in 2018 utilizing soil and groundwater collected and submitted to Resolution Partners Laboratory. The results of the treatability test are documented in the Draft Final CMS Work Plan (AECOM, 2019).

Peroxychem’s MetaFix I-7A combined with sodium bicarbonate, MetaFix I-6A combined with EHC-M®, and zero valent iron (ZVI) were the products evaluated during the bench-scale test.

The results of the treatment test do not allow comparison of the treatments for arsenic removal because the arsenic concentration in the untreated control was below the method detection limit (MDL) of 30 micrograms per liter (μg/L), and the results of each treatment sample were below the MDL of 30 μg/L. Resolution Partners determined it possible that the arsenic added during the spike was bound to natural adsorptive surfaces in the soil (i.e., iron oxides, aluminosilicate minerals). Such adsorption will have been promoted by the unavoidable exposure of fresh soil surface area that is a result of soil handling during sampling at the site and establishment of the treatability tests in the laboratory.

Each of the six treatments applied to the soil/groundwater mixture from SWMU-23 provided the same degree of reduction in soluble cobalt as compared to the untreated control with an observed reduction from 7 μg/L to below the detection limit of 5 μg/L.

1.2.12 Corrective Measures Study and Statement of Basis

A Corrective Measures Study was developed for SWMU 23 in 2020. The CMS proposed a remedy natural attenuation, long term monitoring, land use controls, and contingency in-situ chemical reduction. This document was approved by SCDHEC and a Statement of Basis was developed and submitted in September 2020. The permit modification/renewal that will move the site to the LUC table is still pending.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 1-6 BWJ140078

1.2.13 Land Use Control Implementation Plan

Following the submission of the Statement of Basis, a land use control implementation plan was developed for SWMU 23. This plan was submitted as part of Attachment A to the Uniform Federal Policy – Quality Assurance Project Plan, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina (Bay West, 2016a).

1.3 Report Organization

This document is organized into the following sections:

Section 1.0 Introduction: Presents the site description and history.

Section 2.0 Annual Monitoring Activities: Presents the 2019 and 2021 groundwater and surface water monitoring activities and landfill inspection.

Section 3.0 Monitoring Results: Presents the results from the annual monitoring and analysis.

Section 4.0 Conclusions and Recommendations: Provides a summary of the information presented in the report and any recommendations.

Section 5.0 References

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 2-1 BWJ140078

2.0 ANNUAL MONITORING ACTIVITIES

The following presents a summary of the annual performance monitoring activities conducted at SWMU 23 during the October 2019 and November 2021 annual monitoring events. The 2019 annual monitoring event was performed prior to regulatory approval of the CMS (AECOM, 2020). The sample matrix was modified slightly in the CMS. Well 23MW01 will no longer be monitored and pesticides and PCBs will only be monitored at locations 23MW08 and 23MW09.

These changes were implemented for the 2021 annual monitoring event. Per the LUCIP (AECOM, 2020), surface water analytical results with detections that exceed their respective PALs will result in collection of confirmation surface water samples. Confirmation samples were collected following the 2019 annual event (February 2020) and following the 2021 annual event (March 2022).

2.1 Field Activities

Annual groundwater and surface water monitoring activities were completed in October 2019 and November 2021 and included the collection of depth to groundwater level measurements and collection of groundwater samples at all onsite monitoring wells, collection of three surface water samples and the completion of a landfill inspection.

All groundwater and surface water monitoring activities were performed according to the procedures outlined in the UFP-QAPP and RFI Addendum Work Plan (AECOM, 2016) and/or the LUCIP (AECOM, 2020) and the Uniform Federal Policy – Quality Assurance Project Plan, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina (Bay West, 2016a).

2.1.1 Groundwater Sample Collection and Handling Procedures

Prior to collection of groundwater samples, the depth to groundwater was measured using an electronic water level meter. Calculated groundwater elevations are presented on Table 2.

Contoured groundwater elevation maps from the 2019 and 2021 sampling events are provided as Figures 5 and 6, respectively. Field documentation is provided in Appendix A.

Groundwater samples were collected following low-flow purging methods. Purging of the monitoring wells was performed using a peristaltic pump with Teflon®-lined polyethylene tubing.

New tubing was used at each well during sample collection to eliminate the potential for cross-contamination. Low-flow purging and sampling were performed as detailed in the USEPA publication Ground Water Issue: Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures (USEPA, 1996) and Uniform Federal Policy – Quality Assurance Project Plan, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina (Bay West, 2016a). Field parameters (dissolved oxygen [DO], pH, temperature, salinity, ORP, and specific conductivity) were measured with a YSI 556 (or equivalent) and recorded periodically during purging activities. Groundwater samples were collected following field parameter stabilization. Field parameters are presented on Table 3. Field documentation is provided as Appendix A.

2.1.2 Surface Water Sample Collection and Handling

Surface water samples were collected at a total of three sample locations, 23SW17 through 23SW19. Surface water sample locations are presented in Figure 4. Surface water samples were collected via grab sample. Sampling was performed as detailed in the Uniform Federal Policy – Quality Assurance Project Plan, Basewide Groundwater, Surface Water, and Land Use Control Monitoring, Joint Base Charleston Weapons, Joint Base Charleston Air, South Carolina (Bay West, 2016a). Field parameters (DO, pH, temperature, ORP, and specific conductivity)

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 2-2 BWJ140078 were measured with a YSI 556 (or equivalent) and recorded at the time of sample collection.

Field documentation is provided as Appendix A.

2.1.3 Laboratory Submittal and Analysis

All sample containers were supplied by the analytical laboratory. Sample collection activities were coordinated with the analytical laboratory so that the proper containers, with appropriate preservatives, were provided that hold sufficient sample volumes. After preservation, all samples were stored in a cooler on ice until shipment to the laboratory. All samples were packaged for shipment in a controlled environment to ensure sample integrity. The samples were shipped on ice to maintain a temperature of approximately 4 degrees Celsius.

All samples in 2019, 2020, 2021, and 2022 were submitted to Pace Analytical Gulf Coast in Baton Rouge, Louisiana, a South Carolina certified off-site fixed laboratory. Chain of custody forms were completed to document sample custody and allow traceability of the sample history.

Copies of the chains of custody have been included in the laboratory analytical data packages provided electronically in Appendix B.

Groundwater samples in 2019 were analyzed for the following constituents by Pace Analytical Gulf Coast of Baton Rouge, Louisiana (SCDHEC Certification Number 73006001):

• Volatile organic compounds (VOCs) by USEPA Method 8260B

• Semi-volatile organic compounds (SVOCs) by USEPA Method 8270D

• Pesticides by USEPA Method 8081B

• PCBs by USEPA Method 8082A

• Total and Dissolved Metals by USEPA Method 6020B and

• Cyanide by 9012B

The groundwater monitoring program was modified in the approved CMS (AECOM, 2020).

Pesticides and PCB were monitored at select wells in 2021 as shown in Table 4.

Groundwater samples in 2021 were analyzed for the following constituents by Pace Analytical Gulf Coast of Baton Rouge, Louisiana (SCDHEC Certification Number 73006001):

• VOCs by USEPA Method 8260B

• SVOCs by USEPA Method 8270D

• Pesticides by USEPA Method 8081B

• PCBs by USEPA Method 8082A

• Total and Dissolved Metals by USEPA Method 6020B and

• Cyanide by 9012B

Surface water samples in 2019, 2020 and 2021 were analyzed for the following constituents by Pace Analytical Gulf Coast of Baton Rouge, Louisiana (SCDHEC Certification Number 73006001):

• Total Metals (Arsenic and Cobalt) by USEPA Method 6020B Surface water samples in 2022 were analyzed for the following constituents by Pace Analytical Gulf Coast of Baton Rouge, Louisiana (SCDHEC Certification Number 73006001):

• Total Metals (Arsenic and Cobalt) by USEPA Method 6020B

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 2-3 BWJ140078

2.2 Data Evaluation and Usability

One hundred percent of the analytical data were reviewed based on USEPA National Functional Guidelines for Inorganic Superfund Methods Data Review (USEPA, 2017a), USEPA National Functional Guidelines for Organic Superfund Methods Data Review (USEPA, 2017b), Department of Defense (DoD) Consolidated Quality Systems Manual for Environmental Laboratories [version 5.1 (DoD, 2017) for the October 2019 data, version 5.1.1 (DoD, 2018) for the February 2020 data, and version 5.3 (DoD, 2019) for the 2021 and 2022 data], and the Uniform Federal Policy – Quality Assurance Project Plan for Performance-Based Remediation, Basewide Groundwater, Surface Water, and Land Use Control Monitoring (Bay West, 2016a).

The data validation process included review of chains-of-custody, sample condition receipt forms, field duplicate samples, surrogate recoveries, method/trip blanks, laboratory control sample/laboratory control sample duplicate (LCS/LCSD) recoveries and relative percent differences (RPDs), and matrix spike/matrix spike duplicate (MS/MSD) recoveries and RPDs.

Data was evaluated to verify the achievement of precision, accuracy, representativeness, completeness, comparability, and sensitivity goals established to meet the project data quality objectives.

Results of the evaluation suggest representative samples were collected and analyzed, and the results are representative of the media analyzed. The overall quality of the data collected is discussed in the Data Validation Reports provided in Appendix C. Data qualifiers were added to the data as a result of the validation process (field duplicate RPDs, trip blank contamination, surrogate recovery, LCS recovery, LCS/LCSD RPDs, MS recovery, and MS/MSD RPDs);

however, the data reflect expected site conditions and should be considered compliant and adequate for their intended purpose.

2.3 Investigation Derived Waste Management

Investigation derived waste (IDW) consisting of purge water was contained in 55-gallon drums.

Drums are properly labeled and stored at the Hazardous Waste Storage Yard (Building 2306) prior to disposal. On December 20, 2019, one drum (Manifest #06434) of purge water was transported by A&D Environmental Services, LLC to their facility in Macon, Georgia. On March 16, 2022, one drum (Manifest #06790) of purge water was transported by Envirosmart to Lee County Solid Waste Facility in Bishopville, South Carolina for proper disposal. The final non-hazardous waste manifests for disposal are included in Appendix D.

Used personal protective equipment, primarily nitrile gloves and sample tubing, was consolidated into trash bags and placed into a dumpster behind Building 2 at JBC Weapons for disposal as non-hazardous waste at a Subtitle D Solid Waste Landfill, in accordance with the Uniform Federal Policy – Quality Assurance Project Plan for Basewide Soil Sampling and Analysis (Bay West, 2016b).

2.4 Annual Landfill Inspection and Maintenance

The 2019 landfill inspection was performed in October. The landfill was observed to be in acceptable condition with no erosion or damage of the soil cap observed. Activities including clearing around the monitoring wells and mowing the non-forested areas of the top of the cap were completed in 2019. The 2021 landfill inspection was performed in November. The landfill was observed to be in acceptable condition with no erosion or damage of the soil cap observed.

Activities including clearing around the monitoring wells and mowing the non-forested areas of the top of the cap were completed in 2021. Vegetation maintenance will continue to be performed around monitoring wells as needed and prior to the next annual monitoring event.

Landfill inspection field notes and photos are provided as Appendix E.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 3-1 BWJ140078

3.0 MONITORING RESULTS

The groundwater compliance points are used to monitor plume extent and to document post-injection groundwater parameter conditions. A groundwater monitoring matrix is provided as Table 4. The groundwater data collected from the October 2019 and November 2021 events represents post-injection groundwater conditions. Table 5 presents the results from the analysis of the groundwater samples collected during the 2019 annual monitoring event. Table 6 presents the results from the analysis of the surface water samples collected during the 2019 annual monitoring event and confirmation sampling performed in 2020. Table 7 presents the results from the analysis of the groundwater samples collected during the 2021 annual monitoring event. Table 8 presents the results from the analysis of the surface water samples collected during the 2021 annual monitoring event and confirmation sampling performed in 2022. Table 9 presents the historical analytical results for arsenic and cobalt in groundwater.

Table 10 presents the historical analytical results for arsenic and cobalt in surface water at the current monitoring points. Isoconcentration maps and surface water concentration maps for 2019 and 2021 annual monitoring for arsenic and cobalt are presented as Figures 7 through

14. Graphs of historical arsenic and cobalt concentrations are presented in Appendix F.

Groundwater flow was generally toward the west at the time of groundwater level measurements in October 2019 and generally toward the east at the time of groundwater level measurements in November 2021. Groundwater flow direction is tidally influenced at SWMU 23.

3.1 2019/2020 Analytical Results The groundwater compliance points are used to monitor plume extent and to document groundwater parameter conditions. Table 5 presents a summary of all analyses for October 2019 annual monitoring. Table 6 presents the surface water data from 2019 and confirmation sampling performed in 2020. Tables 9 and 10 present historical arsenic and cobalt concentrations in groundwater and surface water, respectively.

3.1.1 Arsenic and Cobalt Analytical Results

Arsenic concentrations (total and dissolved) were above the MCL (10 µg/L) at wells 23MW-05, 23MW-07, and 23MW-09 (Table 5). Concentrations of arsenic which exceed the MCL range from 29.3 µg/L (dissolved) to 45.8 µg/L (total) as shown on Figure 7. Arsenic concentrations (total and dissolved) were below the MCL (10 µg/L) at all other wells (23MW-01, 23MW-02, 23MW-03, 23MW-04, 23MW-06, 23MW-08, and 23MW-10) Concentrations of field filtered (dissolved) metals samples were generally slightly lower than the total metals samples, but no significant differences were observed between filtered (dissolved) and non-filtered (total) metals samples.

Cobalt concentrations (total and dissolved) were above the background level (11.1 µg/L) at well 23MW-05 (Table 5). Concentrations of cobalt which exceed the background level were detected at 18.1 µg/L (total) and 15.9 µg/L (dissolved) as shown on Figure 8. Cobalt concentrations (total and dissolved) were below the background level (11.1 µg/L) at all other wells (23MW-01, 23MW-02, 23MW-03, 23MW-04, 23MW-06, 23MW-07, 23MW-08, 23MW-09, and 23MW-10).

Concentrations of field filtered (dissolved) metals samples were generally slightly lower than the total metals samples, but no significant differences were observed between filtered (dissolved) and non-filtered (total) metals samples.

Arsenic concentrations (total) were above the MCL for arsenic (10 µg/L) at all three surface water locations (23SW-17, 23SW-18, and 23SW-19) in October 2019. Cobalt concentrations were above the background level (11.1 µg/L) at two surface water locations (23SW-17 and 23SW-18). These samples were collected in areas of high turbidity which likely influenced the results. Additional total and dissolved samples were collected in February 2020 to confirm the

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 3-2 BWJ140078 arsenic and cobalt concentrations. The concentrations from February 2020 were significantly lower than those recorded in October 2019. Total arsenic concentrations were above the MCL for Arsenic (10 µg/L) at 23SW-17. All other locations were below the PAL for total arsenic. Total cobalt did not exceed the PAL at any location. Dissolved arsenic and cobalt did not exceed their respective PALs in any sample indicating that turbidity impacts the surface water samples. This data is presented in Table 6 and on Figures 9 and 10.

3.1.2 Summary of Analytes Exceeding Project Action Levels

The VOCs hexachlorobutadiene, methylene chloride, and naphthalene were detected in well 23MW-10 at concentrations above their respective PALs. No SVOCs were detected above their respective PALs. No VOCs or SVOCs are COPCs.

No pesticides or PCBs were detected above their respective PALs. No pesticides or PCBs are COPCs.

Arsenic and cobalt results are discussed above. No other metals are COPCs. Calcium, iron, magnesium, manganese, potassium, and sodium were detected at concentrations above their respective PALs as shown on Table 5. Concentrations of total and dissolved metals detections were comparable with no significant differences between the separate analyses.

Cyanide was detected at wells 23MW06 (42 µg/L), and 23MW09 (5.1 µg/L) at concentrations exceeding the PAL (2 µg/L). Cyanide is not a COPC.

3.2 2021/2022 Analytical Results The groundwater compliance points are used to monitor plume extent and to document groundwater parameter conditions. Table 7 presents a summary of all analyses for November 2021 annual monitoring. Table 8 presents the surface water data from 2021 and confirmation sampling performed in 2022. Tables 9 and 10 present historical arsenic and cobalt concentrations in groundwater and surface water, respectively.

3.2.1 Arsenic and Cobalt Analytical Results

Arsenic concentrations (total and dissolved) were above the MCL (10 µg/L) at wells 23MW-05, 23MW-07, and 23MW-09 (Table 5). Concentrations of arsenic which exceed the MCL range from 30.8 µg/L (dissolved) to 179 µg/L (total) as shown on Figure 11. Arsenic concentrations (total and dissolved) were below the MCL (10 µg/L) at all other wells (23MW-02, 23MW-03, 23MW-04, 23MW-06, 23MW-08, and 23MW-10) Concentrations of field filtered (dissolved) metals samples were generally slightly lower than the total metals samples, but no significant differences were observed between filtered (dissolved) and non-filtered (total) metals samples.

No cobalt concentrations (total or dissolved) were above the background level (11.1 µg/L) at any well (Table 5). Cobalt concentrations (total and dissolved) were below the background level (11.1 µg/L) at all wells (23MW-01 through 23MW-10), as shown on Figure 12. Concentrations of field filtered (dissolved) metals samples were generally slightly lower than the total metals samples, but no significant differences were observed between filtered (dissolved) and non-filtered (total) metals samples.

Arsenic concentrations (total) were above the MCL for arsenic (10 µg/L) at two surface water locations (23SW18 and 23SW19) in November 2021. Cobalt concentrations did not exceed the MCL at any location in November 2021. Additional samples were collected in March 2022 to confirm the arsenic and cobalt concentrations. The concentrations from March 2022 were significantly lower than those recorded in November 2021. Arsenic and cobalt concentrations were below the PALs at all locations. This data is presented in Table 8 and on Figures 13 and

14. Graphs of surface water sampling analytical results are provided in Appendix F.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 3-3 BWJ140078

3.2.2 Summary of Analytes Exceeding Project Action Levels

The SVOCs benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, dibenz(a,h)anthracene, and indeno(1,2,3-cd)pyrene were detected in well 23MW-10 at concentrations above their respective PALs. No VOCs were detected above their respective PALs. No VOCs or SVOCs are COPCs.

No pesticides or PCBs were detected above their respective PALs in the select wells they were sampled in. No pesticides or polychlorinated biphenyls PCBs are COPCs.

Arsenic and cobalt results are discussed above. No other metals are COPCs. Calcium, iron, magnesium, manganese, potassium, and sodium were detected at concentrations above their respective PALs as shown on Table 5. Concentrations of total and dissolved metals detections were comparable with no significant differences between the separate analyses.

Cyanide was detected at wells 23MW-05 (14 µg/L), 23MW-06 (12 µg/L), 23MW-08 (3.8 µg/L), and 23MW-09 (12 µg/L) at concentrations exceeding the PAL (2 µg/L). Cyanide is not a COPC.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 4-1 BWJ140078

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 Conclusions

This report documents the 2019 and 2021 annual groundwater and surface water monitoring activities, and annual landfill inspection and maintenance.

Annual groundwater monitoring was performed at ten monitoring wells in 2019 and nine monitoring wells in 2021, per the approved CMS (AECOM, 2020). Analytical results for groundwater remain consistent with previous sampling events. Arsenic was detected in three monitoring wells above the PAL of 10 µg/L in 2019 and 2021, and cobalt was detected in one monitoring well above the PAL of 11.1 µg/L in 2019 and was not detected above the PAL in 2021. Overall, concentrations in groundwater are generally decreasing.

Surface water monitoring was performed at three locations. Arsenic was detected above the PAL of 10 µg/L in all three surface water locations, and cobalt was detected above the PAL of

11.1 µg/L in two of the surface water locations in 2019. Additional surface water samples were collected in February 2020 to confirm the 2019 analytical results. Total arsenic was detected above the PAL in one surface water location but dissolved arsenic concentrations did not exceed the PAL in surface water samples collected in February 2020. Cobalt did not exceed the PAL in any surface water samples collected in February 2020. Arsenic was detected above the PAL in two surface water locations in 2021. Cobalt did not exceed the PAL in any location in 2021. Additional surface water samples were collected in March 2022 to confirm the 2021 analytical results. Arsenic and cobalt did not exceed the PALs at any location during the 2022 sampling. The confirmation results collected in 2020 and 2022 indicate that the exceedances of arsenic and cobalt in surface water are related to turbidity.