B.08 GFI JB CHS PBR DA017 (SWMU 17) Draft SA CMI Progress Report 8.pdf

DRAFT

SEMI-ANNUAL CORRECTIVE MEASURES IMPLEMENTATION

PROGRESS REPORT #8 and CONSTRUCTION COMPLETION

REPORT

Solid Waste Management Unit 17 (DA017)

PERFORMANCE-BASED REMEDIATION

Joint Base Charleston Weapons

SOUTH CAROLINA

Contract FA8903-15-C-0016 February 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:

AECOM

4016 Salt Pointe Parkway

North Charleston, South Carolina 29405

With Teaming Partners:

Semi-Annual Corrective Measures Implementation Progress Report #8 & CCR

SWMU 17 (DA017)

Joint Base Charleston Weapons, South Carolina i

DOCUMENT CERTIFICATION

I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. This document is signed and certified in accordance with South Carolina Hazardous Waste Management Regulations Sections R.61-79.270.11 and 270.30(K).

M. Evelyn Rogers, P.E. Date Registration Number 14618

Joint Base Charleston Weapons, South Carolina ii

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 Report Organization................................................................................................. 1-2

2.0 SUPPLEMENTAL INJECTION ACTIVITIES ..............................................................2-1

3.0 GROUNDWATER REMEDIATION ACTIVITIES ........................................................3-1

3.1 Sample Collection and Handling Procedures ........................................................... 3-1

3.2 Laboratory Analysis ................................................................................................. 3-2

3.3 Investigation Derived Waste .................................................................................... 3-2

4.0 ENHANCED REDUCTIVE DECHLORINATION EVALUATION ................................4-1

4.1 Evaluation of Analytical Results ............................................................................... 4-1

4.2 Data Evaluation and Usability .................................................................................. 4-6

5.0 ANNUAL CONTAMINANT-SPECIFIC MONITORING ...............................................5-1

5.1 Beryllium and Arsenic .............................................................................................. 5-1

5.2 Surface Water Monitoring ........................................................................................ 5-1

6.0 LAND USE CONTROLS ............................................................................................6-1

6.1 LUC Inspections ...................................................................................................... 6-1

7.0 CONCLUSIONS AND RECOMMENDATIONS ..........................................................7-1

7.1 Conclusions ............................................................................................................. 7-1

7.2 Recommendations ................................................................................................... 7-1

7.2.1 TCE Plume Monitoring ......................................................................................... 7-2

7.2.2 Contaminant Specific Groundwater Monitoring .................................................... 7-3

7.2.3 Surface Water Monitoring .................................................................................... 7-3

7.2.4 Semi-Annual LUC Inspections ............................................................................. 7-3

7.2.5 Annual Reporting ................................................................................................. 7-4

8.0 REFERENCES ..........................................................................................................8-1

Joint Base Charleston Weapons, South Carolina iii

List of Figures Figure 1-1 Joint Base Charleston Location Map Figure 1-2 SWMU 17 Location Map Figure 1-3 SWMU 17 Site Map Figure 2-1 SWMU 17 Injection Well Layout Map Figure 3-1 SWMU 17 Groundwater Isocontours Shallow – High Tide (August 5, 2022) Figure 3-2 SWMU 17 Groundwater Isocontours Shallow – Low Tide (August 5, 2022) Figure 3-3 SWMU 17 Groundwater Isocontours Deep – High Tide (August 5, 2022) Figure 3-4 SWMU 17 Groundwater Isocontours Deep – Low Tide (August 5, 2022) Figure 3-5 SWMU 17 Groundwater Isocontours Shallow – High Tide (October 4, 2022) Figure 3-6 SWMU 17 Groundwater Isocontours Shallow – Low Tide (October 4, 2022) Figure 3-7 SWMU 17 Groundwater Isocontours Deep – High Tide (October 4, 2022) Figure 3-8 SWMU 17 Groundwater Isocontours Deep – Low Tide (October 4, 2022) Figure 4-1 SWMU 17 TCE Isocontour Map (August 2022) Figure 4-2 SWMU 17 cis-1,2-DCE Isocontour Map (August 2022) Figure 4-3 SWMU 17 VC Isocontour Map (August 2022) Figure 4-4 SWMU 17 TCE Isocontour Map (October 2022) Figure 4-5 SWMU 17 cis-1,2-DCE Isocontour Map (October 2022) Figure 4-6 SWMU 17 VC Isocontour Map (October 2022)

List of Tables Table 2-1 2022 Injection Totals Table 3-1 2022 Sample Matrix Table 3-2 Well Construction and Survey Details Table 3-3 Summary of Groundwater Elevation Data Table 3-4 Summary of Groundwater Field Parameter Data Table 4-1 Summary of Analytical Results in Groundwater – August 2022 Table 4-2 Summary of Analytical Results in Groundwater – October 2022 Table 4-3 Summary of Microbial Results in Groundwater Table 4-4 Summary of Historical Analytical Data Table 5-1 Summary of Analytical Results in Surface Water – August and October 2022 Table 6-1 Proposed 2023 Sample Matrix

List of Appendices Appendix A South Carolina Department of Health and Environmental Control

Correspondence Appendix B Injection Data and Field Documentation Appendix C Sampling Field Documentation Appendix D Laboratory Analytical Data Reports Appendix E Waste Manifests Appendix F Historical COC Concentration Graphs Appendix G Data Validation Reports Appendix H Land Use Control Inspection Documentation

Joint Base Charleston Weapons, South Carolina iv

ACRONYMS AND ABBREVIATIONS

μg/L................ micrograms per liter AFCEC .......... Air Force Civil Engineer Center cis-1,2-DCE ... cis-1,2-dichloroethene CCR ............... construction completion report CMI ............... corrective measures implementation CMI WP ........ corrective measures implementation work plan CMS ............... corrective measures study COCs ............. constituents of concern DHB ............... dehalobacter DHC .............. dehalococcoides DO ................. dissolved oxygen DoD ............... Department of Defense ELAP ............. Environmental Laboratory

Accreditation Program ERD ............... enhanced reductive dechlorination EVO ............... emulsified vegetable oil ft .................... foot or feet IDW…………..investigation derived waste JBC ................ Joint Base Charleston LCS ................ laboratory control sample LCSD ............. laboratory control sample duplicate LUC ............... land use control LUCMP .......... land use control management plan MCL ............... maximum contaminant level mg/L ............... milligrams per liter

MI ................... Microbial Insights MNA ............... monitored natural attenuation MS ................. matrix spike MSD ............... matrix spike duplicate mV ................. millivolts ORP ............... oxygen reduction potential qPCR ............. quantitative polymerase chain reaction RCRA ............. Resource Conservation and

Recovery Act RPD ............... relative percent difference SCDHEC ........ South Carolina Department of

Health and Environmental Control

SM ................. Standard Method SOP ............... standard operating procedure SRS-SD ......... Slow-Release Emulsified

Vegetable Oil Substrate® S.U……………standard units SWMU .......... solid waste management unit TCE .............. trichloroethene TOC ............. total organic carbon UFP-QAPP .... Uniform Federal Policy –

Quality Assurance Project Plan USEPA ........... United States Environmental

Protection Agency VC .................. vinyl chloride 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 Corrective Measures Implementation (CMI) Progress Report #8 for Solid Waste Management Unit (SWMU) 17, Old Southside Missile and Waste Oil Disposal Area at Joint Base Charleston (JBC) Weapons, South Carolina, has been prepared in accordance with the Uniform Federal Policy - Quality Assurance Project Plan (UFP-QAPP) and Corrective Measures Implementation Work Plan (CMI WP) for SWMU 17, Joint Base Charleston Weapons (AECOM, 2016) approved by the South Carolina Department of Health and Environmental Control (SCDHEC) in a letter dated October 10, 2016 (Appendix A). 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 report presents a summary of injection activities and results of monitoring performed at SWMU 17 between January 1, 2022 and December 31, 2022. As discussed during the November 3, 2021 Tier 1 meeting and with concurrence from SCDHEC, the second quarter 2022 sampling event was deferred while plans for supplemental injections at SWMU 17 were prepared and approved and then implemented. This report also serves as the Construction Completion Report (CCR) documenting the supplemental injection activities conducted in June 2022 and also documents the August 2022 sampling event, intended to represent the deferred fourth quarter 2021 and second quarter 2022 events, as well as the October 2022 sampling event. The details of the full-scale groundwater treatment via injection, as well as debris removal and soil excavation, are presented in the SWMU 17 Construction Completion Report (AECOM, 2018).

As recommended in CMI Progress Report #4, groundwater monitoring at SWMU 17 is now being conducted on a semi-annual basis and reported on an annual basis. This annual report is for the 2022 calendar year. For the sake of simplicity and brevity, this stand-alone report cites the CCR and previous CMI Progress Reports throughout rather than incorporating their content in whole.

1.1 Site Description

JBC Weapons is located 10 miles north of Charleston, South Carolina, approximately 16 miles inland from the Atlantic Ocean (Figure 1-1). The facility is situated in two counties, Berkeley and Charleston, and covers an area of approximately 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 was 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 but are collectively referred to as JBC Weapons.

SWMU 17 is located in the Southside of JBC Weapons (Figure 1-2), immediately east and across Wilkinson Way from SWMU 16 (Figure 1-3). SWMU 17 is generally rectangular (approximately 500 feet [ft] long and 200 ft wide) and covers approximately 2.1 acres. The site was used primarily for surface disposal of solid waste between 1950 and 1978, but oils and missile components were also disposed at the site. An estimated 3,000 to 4,000 gallons of engine oil were disposed at SWMU 17 between 1965 and 1966, and a thorium-alloy missile nose cone exhibiting low level radioactivity was removed from the site in 1984 (Tetra Tech, 2012).

As stated in the UFP QAPP and CMI WP (AECOM, 2016), the constituents of concern (COCs) for soil and groundwater at SWMU 17 were identified in the Corrective Measures Study (CMS) Update Rev. 3 (Tetra Tech, 2012) and confirmed in the letter from SCDHEC regarding the Statement of Basis for SWMU 16 and SWMU 17 (SCDHEC, 2012).

Joint Base Charleston Weapons, South Carolina

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

1.2 Report Organization

This Semi-Annual CMI Progress Report is organized into the following sections:

Section 1.0 Introduction: Presents the site description.

Section 2.0 Supplemental Injection Activities: Summarizes the supplemental remedial injection activities.

Section 3.0 Groundwater Monitoring Activities: Summarizes the groundwater monitoring activities.

Section 4.0 Enhanced Reductive Dechlorination Evaluation: Presents the results of the semi-annual groundwater monitoring event Section 5.0 Land Use Controls: Summarizes semi-annual inspection.

Section 6.0 Conclusions and Recommendations Section 7.0 References

Joint Base Charleston Weapons, South Carolina

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

2.0 SUPPLEMENTAL INJECTION ACTIVITIES

Upon analysis of the COC plumes following the April 2021 sampling event, it was determined that localized areas of high COC concentrations were still present at the site. It was proposed that the current areas of high COC concentrations be further remediated in the same manner using six existing injection wells that were previously used for injections (Figure 2-1). The injections were performed in accordance with the 2016 CMI Work Plan (AECOM 2016) and under the following underground injection control permit (Appendix A):

• Permit to Operate (March 21, 2022), #SCHE03020628 The reagent solution, Slow-Release Emulsified Vegetable Oil Substrate® (SRS-SD) and sodium bicarbonate, provided by Terra Systems of Wilmington, Delaware, was delivered in bulk as concentrated media. As part of this supplemental injection, zero valent iron (ZVI) was added to augment the injectate solution to accelerate dechlorination. For this supplemental injection event, similar to the full-scale injection event, potable water from a nearby fire hydrant was used with the concentrated emulsified vegetable oil (EVO) substrate to create the emulsion (i.e., injectate solution) for injection. Substrate batches were prepared 250 gallons at a time, with approximately 13 gallons of EVO, 45 pounds of sodium bicarbonate, and 22.9 pounds of ZVI per batch. The proposed injection design included 3,000 gallons of solution followed by 1,000 gallons of chase water be injected into each of the six injection wells (total of 24,000 gallons injected into the groundwater).

The EVO and sodium bicarbonate were delivered to JBC Weapons on May 26, 2022. The ZVI shipment was scheduled to be delivered to the site on June 6, 2022. The injection set up at SWMU 17 began on June 6, 2022. Cascade prepared the site and injection locations for injection per the approved Underground Injection Control permit. Approximately 20 to 25 gallons of tap water was injected into each of the six target injection wells to ensure the injection system was functional; the water test was completed and successful. The shipment of ZVI was delayed;

therefore, injections of the injectate solution did not commence until the ZVI arrived at the site on June 8, 2022.

Cascade began simultaneous injection of the solution into all six target wells (17IW08, 17IW09, 17IW10, 17IW12, 17IW14, and 17IW17) on June 8, 2022. Three 250-gallon batches of injectate solution were delivered into the subsurface; minor daylighting began at 17IW12 during the injection of the fourth 250-gallon batch of injectate solution. At that point, injection was stopped, and the daylighting hole was plugged using bentonite chips. Injection was then resumed with simultaneous injection into three wells (17IW09, 17IW12, and 17IW17). Upon completion of injection of the fourth 250-gallon batch of injectate into the subsurface, the first three wells were disconnected and the remaining three wells (17IW08, 17IW10, and 17IW14) were connected to the injection system for the fifth 250-gallon batch of solution. Injection began and moderate daylighting was observed at 17IW10 and 17IW14. The injection flow rate was reduced, but daylighting continued. Therefore, injection into 17IW08, 17IW10, and 17IW14 was stopped.

17IW08 had received 72 gallons, 17IW10 had received 64 gallons, and 17IW14 had received 50 gallons upon stopping. Next, injectate solution was delivered to each of the six injection wells one at a time to determine if injectate solution could be injected into any of the injection wells without daylighting. Moderate daylighting was observed when injection began at each of the six injection wells. Injection was therefore halted to allow formation to rest.

On June 9, 2022, injection activities resumed. Cascade and AECOM began variations of the injectate solution and method in an attempt to mitigate the daylighting. Injections were initiated at each targeted injection well, one at a time, at various pressures to attempt to deliver the injectate solution to the formation without causing significant daylighting. Attempts were made to inject a mixture of tap water and ZVI, an injectate solution without the addition of ZVI, and tap water only.

Joint Base Charleston Weapons, South Carolina

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

The same general daylighting occurred when injection of each of the mixtures began. Further attempts were made to flush the injection well screens with tap water. These processes were repeated on June 10, 2022. AECOM discussed the situation with SCDHEC on June 10, 2022, and SCDHEC approved cessation of injection at this time due to apparent clogging of the injection wells screens and/or formation. Injection totals per well are summarized on Table 2-1. A total of 2,495 gallons of injectate solution (a total of 117 gallons EVO, 204 pounds ZVI, 404 pounds sodium bicarbonate, and 2,134 gallons mix water) and 245 gallons of flush water were injected during this supplemental injection event. The injection volumes and activities were recorded on injection field logs provided in Appendix B.

Joint Base Charleston Weapons, South Carolina

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

3.0 GROUNDWATER REMEDIATION ACTIVITIES

As discussed during the November 3, 2021 Tier 1 meeting and with concurrence from SCDHEC, the second 2021 semi-annual sampling event (typically conducted during the fourth quarter each calendar year) and the first 2022 semi-annual sampling event (typically conducted during the second quarter each calendar year) were delayed until after the 2022 supplemental injection event so the impact of the supplemental injections could be evaluated. The supplemental injection event was conducted in June 2022. The first 2022 semi-annual sampling event, intended to represent both the deferred fourth quarter 2021 and second quarter 2022 sampling events, was conducted in August 2022.

The second semi-annual groundwater monitoring event was conducted in in October 2022. Both the August 2022 and the October 2022 monitoring events were conducted in accordance with Worksheet #17 of the UFP-QAPP and CMI WP (AECOM, 2016). The 2022 sample matrix is provided in Table 3-1.

3.1 Sample Collection and Handling Procedures

On August 2-5, 2022, 20 monitoring wells and one surface water location were sampled. On October 3-5, 2022, 24 monitoring wells and one surface water location were sampled (Table 3-1).

Groundwater level measurements were collected from site monitoring wells at both high tide and low tide during each monitoring event. Each monitoring well was opened and allowed to equilibrate to atmospheric pressure before collection of the water level measurement.

Measurements were made using an electronic oil/water interface probe and were measured from the marked survey point, if available, on the top of the monitoring well casing (Appendix C). Well construction data for existing wells at SWMU 17 are presented in Table 3-2 and groundwater measurements, including calculated groundwater elevations, are summarized in Table 3-3.

Potentiometric surface maps for the shallow and deep portions of the unconfined aquifer are based on gauging data at high and low tides during the August 2022 and October 2022 events are presented as Figures 3-1 through 3-8. At the times the August 2022 and October 2022 water level measurements were collected (high and low tide), the shallow and deep groundwater appeared to flow generally east, with some variability between the high tide and low tide during each event. Based on the variability of the groundwater flow direction, it appears groundwater is tidally influenced.

Groundwater purging was conducted following the sampling protocols specified in the UFP-QAPP and CMI WP (AECOM, 2016) and the Basewide Groundwater, Surface Water, and Land Use Control (LUC) Monitoring UFP-QAPP (Bay West, 2016a). Low-flow purging/sample collection techniques were employed and a peristaltic pump was used to purge/sample each monitoring well. Disposable sample tubing (Teflon®) in each monitoring well was positioned below the top of the water column, between the approximate middle and the uppermost portion of the well screen, depending on well recovery rates during purging. The pumping rate was adjusted to minimize drawdown. The pumps were operated continuously during sampling to minimize aeration in the tubing.

Temperature, pH, oxidation-reduction potential (ORP), specific conductivity, dissolved oxygen (DO), and turbidity were measured and recorded periodically during purging activities. A groundwater sample was collected from each monitoring well after the field parameter readings stabilized in accordance with the criteria found in Worksheet #14 of the Basewide Groundwater, Surface Water, and LUC Monitoring UFP-QAPP (Bay West, 2016a). Final field parameter measurements are summarized in Table 3-4, and groundwater sampling logs are provided in Appendix C.

Joint Base Charleston Weapons, South Carolina

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

Groundwater sample collection was conducted following the sampling protocols specified in the UFP-QAPP and CMI WP (AECOM, 2016) and the Basewide Groundwater, Surface Water, and LUC Monitoring UFP-QAPP (Bay West, 2016a). The collected samples were documented on chains-of-custody and shipped to Pace Analytical Services, LLC in Columbia, South Carolina (Pace, formerly Shealy Environmental Services, Inc.) via Federal Express for analysis (see Section 3.2).

3.2 Laboratory Analysis

During the August 2022 sampling event, groundwater samples were collected from 20 monitoring wells and one surface water location. Quality assurance/quality control samples (three trip blanks, three field duplicate samples, and one matrix spike/matrix spike duplicate [MS/MSD] set) and one investigation derived waste (IDW) sample (for waste profiling) were also collected. All samples were submitted to Pace Analytical Services, LLC in Columbia, South Carolina (Pace, formerly Shealy Environmental Services, Inc.) for analysis. Pace currently holds a Department of Defense (DoD) Environmental Laboratory Accreditation Program (ELAP) certification and the SCDHEC Certification number is 32010001. The groundwater samples were analyzed for select volatile organic compounds (VOCs) by Method SW-846 8260B; methane, ethane, and ethene by Method RSK-175; anions by Method 9056A; sulfide by Method A4500SF; total organic carbon (TOC) by Method Standard Method A5310C; alkalinity by Method A2320; and ortho-phosphate by Method E365.1. Wells 17MW02S, 17MW14S, 17MW15S, 17MW16S, 17MW17S, and 17MW18S were analyzed for beryllium by Method SW-846 6020B, and wells 17MW12D, 17MW36, and 17MW42 were analyzed for arsenic by Method SW-846 6020B. The surface water sample (17SW01) was analyzed for select VOCs by Method SW-846 8260B and arsenic and beryllium by Method

SW-846 6020B.

For the October 2022 sampling event, samples were collected from 24 monitoring wells and one surface water location. Quality assurance/quality control samples (three trip blanks, three field duplicate samples, and one MS/MSD set) and one IDW sample (for profiling) were also collected.

All samples were submitted to Pace Analytical Services, LLC in Columbia, South Carolina (Pace, formerly Shealy Environmental Services, Inc.) for analysis. Pace currently holds a DoD ELAP certification and the SCDHEC Certification number is 32010001. The groundwater samples for all wells except 17MW12D, 17MW14S, and 17MW36 were analyzed for select VOCs by Method SW-846 8260B; methane, ethane, and ethene by Method RSK-175; anions by Method 9056A;

sulfide by Method A4500SF; total organic carbon (TOC) by method A5310C; alkalinity by Method SM2320B; and ortho-phosphate by Method E365.1. Wells 17MW02S, 17MW14S, 17MW15S, 17MW16S, 17MW17S, and 17MW18S were analyzed for beryllium by Method SW-846 6020B, and wells 17MW12D, 17MW36, and 17MW42 were analyzed for arsenic by Method SW-846 6020B. The surface water sample (17SW01) was analyzed for select VOCs by Method SW-846 8260B and arsenic and beryllium by Method SW-846 6020B Groundwater samples were also collected from monitoring wells 17MW05S, 17MW07S, 17MW66, and 17MW67 during both the August 2022 and the October 2022 sampling events and submitted to Microbial Insights in Knoxville, Tennessee for analysis of dehalococcoides (DHC) and dehalobacter (DHB) populations by Microbial Insights (MI) standard operating procedure (SOP) using the Quantitative Polymerase Chain Reaction (qPCR) method Rev 1.2. Analytical data reports are provided in Appendix D.

3.3 Investigation Derived Waste

Two 55-gallon drums of IDW (purge water and decontamination water) were generated during the reporting period. The drums were properly labeled and stored at the Hazardous Waste Storage Yard (Building 2332) prior to disposal. On January 17, 2023, one hazardous drum of IDW was transported by ES-Integrated to the Giant Resource Recovery facility located in Sumter, Joint Base Charleston Weapons, South Carolina

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

South Carolina for proper disposal (Manifest #022212817). One non-hazardous drum of IDW was transported by ES-Integrated to Lee County Solid Waste Facility in Bishopville, South Carolina for proper disposal (Manifest #06909). The final manifest for disposal is included in Appendix E.

Used personal protective equipment, primarily nitrile gloves and tubing, was consolidated into trash bags and placed into a designated dumpster located behind Building 2 at JBC Weapons for disposal as non-hazardous waste at a Subtitle D Solid Waste Landfill, in accordance with the Basewide Soil UFP-QAPP (Bay West, 2016b).

Joint Base Charleston Weapons, South Carolina

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

4.0 ENHANCED REDUCTIVE DECHLORINATION EVALUATION

4.1 Evaluation of Analytical Results

The data collected from the baseline groundwater monitoring event (November 2016) in combination with the post-full-scale injection monitoring events (June 2018 through March 2019) and subsequent semi-annual monitoring events have been collectively used to evaluate whether the applied corrective measures are successfully remediating the COCs in groundwater beneath the site. Baseline groundwater data and the data from the first four quarterly monitoring events can be found in CMI Progress Report #4 (AECOM, 2019). CMI Progress Report #4 also includes an initial evaluation of enhanced reductive dechlorination (ERD) after the first-year post-implementation (four quarters). Subsequent data can be found in CMI Progress Reports #5 (AECOM, 2020), #6 (AECOM, 2021), and #7 (AECOM, 2022). These data, combined with the groundwater monitoring data presented in this report, are used to evaluate the current effectiveness of the full-scale injection event in 2018 and subsequent injection event in 2022.

The August 2022 and October 2022 analytical results for COCs and geochemical parameters in groundwater are presented in Tables 4-1 and 4-2, respectively. Isoconcentration maps for trichloroethene (TCE), cis-1,2-dichloroethene (cis-1,2-DCE), and vinyl chloride (VC) for August 2022 are presented as Figures 4-1 through 4-3, respectively, and isoconcentration maps for TCE, cis-1,2-DCE, and VC for the October 2022 sampling events are presented in Figures 4-3 through 4-6, respectively. Refer to Figures 3-1 through 3-8 for groundwater flow direction as it relates to the isoconcentrations. Trend plots summarizing concentrations of select VOCs and biogeochemical parameters in groundwater in the 21 monitoring wells included in the semi-annual monitoring events from the baseline groundwater sampling event (November 2016) through the October 2022 sampling event are provided in Appendix F.

Table 4-3 presents a summary of the microbial analysis results from November 2016 (baseline) through October 2022 for 17MW05S, 17MW07S, 17MW66, and 17MW67. A summary of historical analytical data for groundwater and surface water (November 2016 through October 2022) is provided in Table 4-4.

CMI effectiveness was evaluated using the indicators presented below. The data collected during groundwater monitoring was compared to these indicators to evaluate the in-situ ERD system performance.

• Effectiveness of Amendment Following Injections o TOC concentrations should increase following the EVO injections and should be maintained to enhance the reductive dechlorination. Elevated TOC concentrations must be present in the monitoring wells to maintain sufficient TOC concentrations throughout the treatment zone. TOC concentrations greater than 20 milligrams per liter (mg/L) are considered an indication of effectiveness in amending organic substrates (United States Environmental Protective Agency

[USEPA], 1998).

o DHC and DHB population densities must be maintained to support on-going reductive dechlorination of chlorinated compounds. Favorable growth conditions for DHC organisms are important to establish and maintain because DHC have the capability to fully dechlorinate TCE to ethene, while DHB have the capability to partially dechlorinate TCE to cis-1,2-DCE. Lu and others (2006) proposed using a DHC concentration of 1.0E+04 cells per milliliter as a screening criterion to identify sites where biological reductive dechlorination will proceed at “generally useful” rates.

• Establishing Anaerobic/Reducing Conditions in Subsurface

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Contract FA8903-15-C-0016 4-2 BWJ140078 o Anaerobic conditions are critical for reductive dechlorination. The EVO solution should be amended sufficiently to alter and maintain geochemical conditions conducive to reductive dechlorination. DO, ORP, and pH monitoring results can be used to determine if an anaerobic condition has been established effectively.

The DO concentration should be less than 0.5 mg/L, and the ORP should be less than -50 millivolts (mV) as an indication of reducing conditions favorable for reductive dechlorination. Reductive dechlorination typically occurs at a pH between 5.5 Standard Units (S.U.) and 8.5 S.U., although, a pH between 6.3 and

8.5 S.U. is more favorable.

• Contaminant Dechlorination o The ultimate goal of the CMI is the reduction in concentration of groundwater

COCs, specifically TCE and its daughter products. Under anaerobic conditions, TCE and its daughter products are degraded through reductive dechlorination.

Concentrations of TCE and its daughter products were monitored quarterly following completion of the full-scale injection activities and are now monitored semi-annually. Decreasing trends in TCE concentrations or increasing trends in daughter product concentrations should be observed if the bioremediation system is performing efficiently. Ultimately, the daughter products will also degrade into ethane and ethene, resulting in a long-term decreasing trend for the daughter products as well.

The following presents a review of the groundwater analytical results for selected monitoring wells located within the full-scale treatment zone at SWMU 17.

• 17MW05S

o Shallow zone monitoring well located near the center of the groundwater treatment zone.

o TCE concentrations at this location decreased following pilot study, full-scale, and supplemental injections. Concentrations decreased from baseline TCE concentration of 5,390 micrograms per liter (µg/L) in November 2016 to 425 µg/L flowing the full-scale injection and then fluctuated between non-detect and 39.8 µg/L (0.44 µg/L in October 2022). Cis-1,2-DCE was detected at a concentration of 372 µg/L in November 2016 (baseline) and decreased following full-scale injections to 13 µg/L in October 2022. VC was detected at a concentration of 579 µg/L in November 2016 (baseline), increased to 1,240 µg/L in June 2017 (post pilot study), and decreased to 380 µg/L in October 2022 (post full scale). General decreases in TCE, cis-1,2-DCE, and VC show dechlorination is occurring in this area.

o TOC concentrations increased from 10 mg/L in November 2016 (baseline) to 1,430 mg/L in June 2018 (following completion of full-scale injection activities), then decreased to 92.4 mg/L in April 2021, then increased to 2010 mg/L in August 2022 (following the supplemental injection activities) and subsequently decreased to a current concentration of 69 mg/L (October 2022), which is well above 20 mg/L and therefore considered sufficient to enhance reductive dechlorination. ORP decreased from 136.3 mV in November 2016 to a range of -50 mV to -80 mV following pilot scale injections. ORP decreased further following full scale injections to -106.3 mV (June 2018) and remains at -169.7 mV in October 2022, indicating strongly reducing conditions. Methane concentrations measured at this location post-full-scale injections increased from 163 µg/L to 9,060 µg/L in December 2019, with a current concentration of 7,000 µg/L in October 2022. These concentrations indicate the presence of strongly reducing conditions, which are conducive to dechlorination. Although the full volume of

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 4-3 BWJ140078 injectate planned were not able to be injected as designed during the supplemental injection event, noticeable increases in methane and TOC concentrations can be observed in the August and October 2022 data.

o The pH increased from 4.61 S.U. in November 2016 to 6.71 S.U. in October 2022. The pH is within the favorable range for reductive dechlorination.

o DHC/DHB population densities increased significantly following the pilot study injection and then initially decreased following full-scale implementation;

however, population densities increased to well above baseline 12 months post-full-scale injection. Population densities then decreased to near or below baseline in April 2021. Following the June 2022 supplemental injection, the population density of DHB increased significantly in August 2022 and then decreased dramatically in October 2022; the DHC population decreased slightly in both August 2022 and October 2022.

• 17MW06S

o Shallow zone monitoring well located near the center of the groundwater treatment zone.

o TCE concentrations at this location decreased following pilot study injections and increased immediately following both the full-scale, and supplemental injections.

The baseline TCE concentration was 10,200 µg/L in November 2016; the most recent concentration was 11,000 µg/L in October 2022. Cis-1,2-DCE was detected at a concentration of 416 µg/L in November 2016, increased following the full-scale injections to a maximum concentration of 2,060 µg/L in December 2018, increased following the supplemental injections to 2,000 µg/L in August 2022 then decreased to a concentration of 1,100 µg/L in October 2022. VC was detected at a concentration of 60.4 µg/L in November 2016, increased to of 384 µg/L in May 2020, increased to a high of 530 µg/L in August 2022 following the supplemental injections, and then decreased to 270 µg/L in October 2022.

o TOC concentrations remained relatively consistent from baseline to the most recent sampling event (4.5 mg/L in November 2016 and 3.9 mg/L in October 2022). Methane concentrations have decreased from 873 µg/L in November 2016 to a low of 176 µg/L in October 2020 followed by increasing to 340 µg/L in October 2022. ORP measurements have been positive except in December 2018, March 2019, and April 2021, including positive results in August 2022 and October 2022. The conditions observed post-supplemental injection do not fully support the presence of sustained reducing conditions at this well.

o The pH increased from 5.12 S.U. in November 2016 to 6.06 S.U. in December 2018 and was most recently 5.25 S.U. in October 2022. These pH values are below the favorable range for reductive dechlorination.

o The low pH and low TOC since the 2018 injection event indicate that the distribution of EVO and sodium bicarbonate was not optimal in this portion of the plume. The closest injection well is adjacent to the large excavation area, which may have influenced the preferential flow of the injected material in the targeted treatment zone.

• 17MW07S

o Shallow zone monitoring well located near the center of the groundwater treatment zone.

o TCE concentrations increased from baseline TCE concentration of 17,300 µg/L in

November 2016 to a maximum concentration of 22,600 µg/L in June 2018 and have decreased to a concentration of 63 µg/L in October 2022. Concentrations of

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 4-4 BWJ140078 cis-1,2-DCE and VC increased following pilot study injections, which is expected as TCE breaks down. Although the supplemental injections were not able to be implemented as planned, a notable decrease in TCE and cis-1,2-DCE as well as an increase in VC was observed following these injections. Cis-1,2-DCE was detected at a concentration of 213 µg/L in November 2016, increased to a concentration of 4,190 µg/L in June 2018, and was detected at a concentration of 370 µg/L in October 2022. VC was not detected in November 2016 (its detection limit was elevated [100 µg/L]) and was detected at a concentration of 6,000 µg/L in October 2022.

o TOC concentrations have increased from 5.3 mg/L in November 2016 and 12 mg/L in April 2021 to 560 in October 2022, following supplemental injections.

Methane concentrations have been elevated since May 2020 and remain elevated as of the most current sampling event with a concentration of 2,700 µg/L (October 2022). ORP measurements have fluctuated between positive and negative; ORP was measured at -87.3 mV in October 2022.

o The pH increased from 5.02 S.U. in November 2016 to 5.96 S.U. in October 2022.

o DHC/DHB population densities increased following pilot study injections, decreased following full-scale implementation, have fluctuated since then.

Notable increases in DHC/DHB population densities were observed following the supplemental injections. The DHC/DHB population density increased by two orders of magnitude from April 2021 to August 2022. By October 2022, DHC population densities remained relatively the same, but the DHB concentration decreased to an estimated value.

o Similar to well 17MW06S, the low pH and low TOC since the full-scale injection event indicates that the initial distribution of EVO and sodium bicarbonate was not optimal in this portion of the plume. However, this area does show substantial influence by the supplemental injections in June 2022.

• 17MW19S

o Shallow zone monitoring well located near the northern edge of the groundwater treatment zone.

o TCE concentrations increased after the baseline TCE concentration of 11,500 µg/L in November 2016 to 12,100 µg/L in June 2017 and then decreased to a low of 176 µg/L in October 2020. The TCE concentration increased to 1,600 µg/L in August 2022 after the supplemental injection and then decreased to a concentration of 550 µg/L in October 2022. Concentrations of cis-1,2-DCE and VC increased following the full-scale injections. Cis-1,2-DCE was detected at a concentration of 331 µg/L in November 2016 and was detected at a maximum concentration of 1,910 µg/L in December 2018; the cis-1,2-DCE concertation initially increased after the supplemental injection event (264 µg/L in April 2021 to 510 µg/L in August 2022) and then decreased to a concentration of 320 µg/L in October 2022. VC was detected at a concentration of 43.1 µg/L in November 2016 and increased to a maximum of 1,510 µg/L in April 2021 and then decreased after the supplemental injection event to 320 µg/L in August 2022 and then 230 µg/L in October 2022.

o TOC increased from 6.4 mg/L in November 2016 to 60.3 mg/L in March 2019, then decreased to 26 mg/L in October 2022. Methane concentrations measured at this location decreased from 1,360 µg /L in November 2016 to 981 µg/L in April 2021. A noticeable increase was observed after the supplemental injections

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 4-5 BWJ140078 in August 2022 (3,000 µg/L) and October 2022 (3,200 µg/L). Methane concentrations increased following the supplemental injections from 981 µg/L in April 2021 to 3,200 µg/L in October 2022. ORP measurements have decreased from 97.3 mV in November 2016 to -76.6 mV in October 2022. The combination of elevated methane and an ORP less than -50 mV supports the presence of reducing conditions.

o The pH increased from 5.16 S.U. in November 2016 to 6.3 S.U. in October 2022.

The pH is within the favorable range for reductive dechlorination.

• 17MW66

o Deep zone monitoring well located near the center of the groundwater treatment zone.

o Tetrachloroethylene was detected for the first time at an estimated concentration of 87 µg/L in August 2022, decreasing to non-detect in October 2022. TCE concentrations increased from baseline concentration of 302 µg/L in November 2016 to a peak concentration of 37,500 µg/L in December 2019, then decreased to a concentration of 452 µg/L in April 2021; after the supplemental injections, it increased to 4,300 µg/L in August 2022 and 6,200 µg/L in October 2022.

Concentrations of cis-1,2-DCE and VC also increased following pilot study injections. Cis-1,2-DCE was detected at a concentration of 12.1 µg/L in November 2016 (baseline), increased to a maximum concentration of 47,900 µg/L in May 2020, and decreased to a current concentration of 10,400 in April 2021; after the supplemental injections, cis-1,2-DCE increased to 36,000 in August 2022 and then 31,000 µg/L in October 2022. VC was detected at a concentration of 0.644 µg/L in November 2016, increased to a maximum concentration of 22,300 µg/L in April 2021, and decreased after the supplemental injections to a current concentration of 6,500 µg/L in October 2022.

o TOC concentrations increased from 9.7 mg/L in November 2016 to a maximum of 129 mg/L in October 2020, decreasing to a current concentration of 7.9 mg/L in October 2022. Concentrations of methane increased following supplemental injections from an estimated value of 208 µg/L in April 2021 to 2,500 µg/L in October 2022. ORP measurements (-77.9 mV in November 2016 to -120.4 mV in April 2021) remain negative at this location indicating reducing conditions conducive to dechlorination are present.

o The pH decreased from 7.30 S.U. in November 2016 to 5.87 S.U. in June 2017 (after the pilot study injections), and then increased to a current value of 6.41 S.U. The pH has remained within the typical range for reductive dechlorination.

o DHC population density increased by two orders of magnitude between May 2020 and October 2020 to its maximum concentration. By April 2021, it had decreased by one order of magnitude and continued decreasing through October 2022. The DHB population density increased to its maximum in March 2019 and then decreased through April 2021; the DHC population density increased in August 2022 after the supplemental injections, but then decreased in October 2022.

• 17MW67

o Deep zone monitoring well located near the western edge of the groundwater treatment zone.

o TCE concentrations increased after the pilot study injection from the baseline

TCE concentration of 419 µg/L in November 2016 to a maximum concentration of 11,900 µg/L in June 2017, then decreased to 7.12 µg/L in April 2021. After the

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 4-6 BWJ140078 supplemental injections, the TCE concentration increased to 1,600 µg/L in August 2022 and remained the same in October 2022. Concentrations of cis-1,2- DCE and VC increased following full-scale injections, and both remain higher than baseline concentrations. Cis-1,2-DCE was detected at a concentration of

7.61 µg/L in November 2016 (baseline), increased to a maximum concentration 5,320 µg/L in June 2018 (post-full-scale injection) and was detected most recently at a concentration of 3,400 µg/L in October 2022. VC was not detected during the baseline sampling in November 2016 (detection limit of 2.5 µg/L), increased to a maximum concentration of 9,480 µg/L in December 2018, and was detected most recently at a concentration of 2,900 µg/L in October 2022.

o TOC increased from 3.1 mg/L in November 2016 to 149 mg/L in September 2018 and was most recently detected at 6.4 mg/L in October 2022. Methane concentrations measured at this location from 915 µg/L in November 2016 (baseline) to a maximum of 10,200 µg/L in December 2019 and then most recently at 8,400 µg/L suggest strongly reducing conditions conducive to reductive dechlorination are present. ORP measurements have remained consistently low from -92.1 mV in November 2016 to -120.4 mV October 2022, which suggests reducing conditions conducive to dechlorination are present.

o The pH decreased from 7.29 S.U. in November 2016 to 6.46 in October 2022.

The pH has remained within the typical range for reductive dechlorination.

o DHC and DHB population densities were both higher in December 2019 than in December 2018; however, both DHC and DHB population densities October 2022 are less than the initial (post-full-scale injections) measurements in December 2018.

4.2 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), DoD Consolidated Quality Systems Manual for Environmental Laboratories [version 5.3 (DoD, 2019) for August 2022 data and version 5.4 (DoD, 2021) for October 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 sample relative percent differences (RPDs), surrogate recoveries, equipment/method/trip blanks, laboratory control sample/laboratory control sample duplicate (LCS/LCSD) recoveries and RPDs, and MS/MSD 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 G. Data qualifiers were added to the data as a result of the validation process (holding time exceedances, field duplicate RPDs, method blank contamination, 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.

Joint Base Charleston Weapons, South Carolina

Contract FA8903-15-C-0016 5-1 BWJ140078

5.0 ANNUAL CONTAMINANT-SPECIFIC MONITORING

5.1 Beryllium and Arsenic

Concentrations of arsenic exceeded the maximum contaminant level (MCL) of 10 µg/L in 17MW12D (17 µg/L) and 17MW36 (36 µg/L) in August 2022 and in 17MW12D (23 µg/L) and 17MW36 (41 µg/L) in October 2022. 17MW12D and 17MW36 are both deep monitoring wells located in the southwest portion of SMWU 17 along Wilkinson Way. Arsenic was not detected in 17MW42, a deep monitoring well located in the northern portion of SWMU 17 along the power line right of way.

Beryllium concentrations exceeded its MCL of 4 µg/L in all wells analyzed; beryllium was detected at concentrations ranging from 45 µg/L in 17MW18S to 82 µg/L in 17MW17S in August 2022 and ranging from 39 µg/L in 17MW18S to 68 µg/L in 17MW17S in October 2022. 17MW18S and 17MW17S are both located in the eastern portion of SWMU 17 within a Palustrine Forested wetland area.

Concentrations of arsenic and beryllium detected in each well in August and October 2022 were similar to the…