B.08 GFI JBCA_ST027_SWMU145_DF_CASER_2022_030923 DRAFT for GFI.pdf

DEPARTMENT OF THE AIR FORCE

AIR FORCE CIVIL ENGINEER CENTER

JOINT BASE CHARLESTON SOUTH CAROLINA

9 March 2023

Ms. Laura Powers AFCEC/CZOE, JB Charleston ISS 203 S. Davis Drive, Bldg 247, 1st Floor Joint Base Charleston, SC 29404-4707

Mr. Robert A. Dunn, Hydrogeologist Underground Storage Tank Management Division Bureau of Land and Waste Management SC Department of Health and Environmental Control 2600 Bull Street Columbia, SC 29201-1708

RE: Draft Final 2022 Semi-Annual Groundwater Monitoring Report/Corrective Action System

Evaluation Report – August 2022 and November 2022, SWMU 145 (ST027), Building 575 JP-4 Tank Leak, UST Permit #01829, Joint Base Charleston-Air, South Carolina

Dear Mr. Dunn, The purpose of this letter is to submit one (1) hardcopy and electronic copy (CD) of the subject plan for SWMU 145 (ST027, Building 575 JP-4 Tank Leak), UST Permit #01829, at Joint Base Charleston- Air, South Carolina for your review and approval. Should you have any questions or comments regarding the attached, please contact me by telephone at (843) 963-2701 or by email at laura.powers.3@us.af.mil.

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 R.61-79.270.11 and 270.30(K).

Sincerely, LAURA POWERS, P.E., GS-12, DAFC

Remedial Project Manager cc: Justin Damann & Lisa Coffey, PG (FPM) mailto:laura.powers.3@us.af.mil

DRAFT FINAL

2022 SEMI-ANNUAL GROUNDWATER MONITORING REPORT

(CORRECTIVE ACTION SYSTEM EVALUATION

[CASE] REPORT – AUGUST 2022 and NOVEMBER 2022)

SWMU 145 (ST027) BUILDING 575 JP-4 TANK LEAK

GWPD SITE # A-10-AA-01829

JOINT BASE CHARLESTON-AIR

NORTH CHARLESTON, SOUTH CAROLINA

FACILITY ID SC3570024460

Performance Based Remediation

Contract Number: FA8903-13-C-0006

Prepared for

AIR FORCE CIVIL ENGINEER CENTER

2261 Hughes Ave., Suite 163

Joint Base San Antonio - Lackland, Texas 78236-9853

Prepared by:

FPM Remediations, Inc.

An Olgoonik Company

181 Kenwood Avenue Oneida, NY 13421

February 2023

This page is intentionally left blank.

CASE Report – August 2022 and November 2022 SWMU 145 (ST027) Building 575 JP-4 Tank Leak Joint Base Charleston - Air

FPM Remediations, Inc. i Contract No. FA8903-13-0006

2022 Semi-Annual Groundwater Monitoring Report (CASE Report – August 2022 and November 2022)

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 be 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.

Site:

SWMU 145 (ST027) Building 575 JP-4 Tank Leak, UST Permit #01829 Joint Base Charleston-Air North Charleston, South Carolina

Submitted to:

South Carolina Department of Health and Environmental Control (SCDHEC) 2600 Bull Street Columbia, South Carolina 29201

Prepared for:

Joint Base Charleston – Air Charleston, South Carolina

Prepared by:

FPM Remediations, Inc.

181 Kenwood Avenue Oneida, NY 13421

Author:

Justin Damann Title: FPM Site Lead Date: 03/08/2023

Reviewer:

Lisa Coffey Title: FPM Project Manager

Gaby Atik, PE SC #31468 Title: FPM Supervising Engineer

Laura Powers, PE Title: _____JBCA Remedial Project Manager

FPM Remediations, Inc. ii Contract No. FA8903-13-0006

FPM Remediations, Inc. iii Contract No. FA8903-13-0006

TABLE OF CONTENTS

SECTION PAGE

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

1.1 Report Organization ..................................................................................................... 1-1

1.2 Facility Information ..................................................................................................... 1-2

1.3 Site Information ........................................................................................................... 1-2

2.0 SITE BACKGROUND .................................................................................................. 2-1

2.1 Site History .................................................................................................................. 2-1

2.2 Site Hydrology, Geology, and Hydrogeology ............................................................. 2-1

2.3 Previous Investigation and Remediation Activities ..................................................... 2-3

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

3.1 Groundwater Monitoring Program .............................................................................. 3-1

3.2 Groundwater Monitoring Procedures .......................................................................... 3-1

3.3 Investigation-Derived Waste (IDW) ............................................................................ 3-1

3.4 Water Level Measurements ......................................................................................... 3-1

3.5 Geochemical Parameter Measurements ....................................................................... 3-2

3.6 Groundwater Monitoring Results ................................................................................ 3-2

3.7 Quality Control/Quality Assurance.............................................................................. 3-2

4.0 SITE PERFORMANCE MODEL ................................................................................ 4-1

5.0 REMEDIAL PROCESS OPTIMIZATION (RPO) .................................................... 5-1

6.0 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS ............................... 6-1

7.0 REFERENCES ............................................................................................................... 7-1

FPM Remediations, Inc. iv Contract No. FA8903-13-0006

TABLES

Table 1 Monitoring Well Screen Interval Details and Groundwater Level Measurements, August 2022 and November 2022 Table 2 Historical Groundwater Elevations, September 2003 to November 2022 Table 3 Historical and Recent Groundwater Geochemical Parameter Measurements, September 2003 to November 2022 Table 4 Groundwater Monitoring Results, August 2022 and November 2022 Table 5 Historical Groundwater Monitoring Results, September 2003 to November 2022

FIGURES

Figure 1 SWMU 145 (ST027) Building 575 JP-4 Tank Leak Site Location Figure 2 SWMU 145 (ST027) Building 575 JP-4 Tank Leak Historical Site Features Figure 3a SWMU 145 (ST027) Building 575 JP-4 Tank Leak Water Table Elevation Contours

(August 2022) Figure 3b SWMU 145 (ST027) Building 575 JP-4 Tank Leak Water Table Elevation Contours

(November 2022) Figure 4 SWMU 145 (ST027) Building 575 JP-4 Tank Leak COC Groundwater

Concentrations (August 2022 and November 2022) Figure 5a Historical Concentrations of Naphthalene in Groundwater, September 2003 to

November 2022 (Monitoring Wells MW20-01, -01R, -03, -04, -05, -05R, -08, - 08R, -09, and -09R)

Figure 5b Historical Concentrations of Naphthalene in Groundwater, September 2003 to November 2022 (Monitoring Wells MW20-10, -10R, -11, -11R, -12, -13, -14, -15, and -15R)

Figure 5c Historical Concentrations of Naphthalene in Groundwater, September 2003 to November 2022 (Monitoring Wells MW20-16, -16R, -22, -23, -24, -25, and -27)

Figure 6 Site Performance Model, Benzene and Naphthalene in Groundwater, September 2003 to November 2022

APPENDICES

Appendix A Daily Reports and Field Notes Appendix B Groundwater Sampling Logs Appendix C Laboratory Analytical Reports (CD only) Appendix D Data Validation Reports Appendix E SCDHEC Contractor Checklist

FPM Remediations, Inc. v Contract No. FA8903-13-0006

LIST OF ABBREVIATIONS AND ACRONYMS

ACQAP Annual Contractor Quality Assurance Plan AFCEC Air Force Civil Engineer Center AFVR Aggressive fluid vapor recovery bgs below ground surface BTEX Benzene, toluene, ethylbenzene and xylenes CAP Corrective Action Plan CASE Corrective Action System Evaluation CO2 Carbon dioxide COC Contaminant of Concern DO Dissolved Oxygen DOD Department of Defense ELAP Environmental Laboratory Approval Program FPM FPM Remediations, Inc.

ft foot or feet ft/ft feet/feet or foot/foot ft/min foot per minute or feet per minute GEL General Environmental Laboratories, Inc.

GWPD Groundwater Protection Division HP Horsepower IDW Investigation-Derived Waste IRP Installation Restoration Program JBCA Joint Base Charleston-Air LNAPL Light nonaqueous phase liquid LTM Long-term monitoring MCL maximum contaminant level µg/L micrograms per liter MOGAS Motor Gasoline MS/MSD matrix spike/matrix spike duplicate NCP National Oil and Hazardous Substances Pollution Contingency Plan (40 CFR 300) NFA No Further Action NTU Nephelometric Turbidity Unit O2 Oxygen

FPM Remediations, Inc. vi Contract No. FA8903-13-0006

LIST OF ABBREVIATIONS AND ACRONYMS (continued) ORP Oxidation-Reduction Potential OTIE Oneida Total Integrated Enterprises Parsons Parsons Engineering Science, Inc.

PARCC Precision, Accuracy, Representativeness, Completeness, Comparability PBR Performance Based Remediation pH negative logarithm of the concentration of Hydrogen (H+) ions in solution QAPP Quality Assurance Project Plan RBSL Risk Based Screening Level RCRA Resource Conservation and Recovery Act RI/FS Remedial Investigation/Feasibility Study SC Site Closeout SCDHEC South Carolina Department of Health and Environmental Control SCFM Standard cubic feet per minute SGS SGS North America, Inc.

SSTL Site-specific Target Level SSWP Site-Specific Work Plan SWMU Solid Waste Management Unit TRPH Total Recoverable Petroleum Hydrocarbons TVH Total Volatile Hydrocarbons URS URS Group, Inc.

USEPA United States Environmental Protection Agency UST Underground Storage Tank VMP Vapor Monitoring Point

FPM Remediations, Inc. 1-1 Contract No. FA8903-13-0006

1.0 INTRODUCTION

FPM Remediations, Inc. (FPM), in association with URS Group, Inc. (URS) under a Performance- Based Remediation (PBR) contract with the Air Force Civil Engineer Center (AFCEC), is conducting environmental remediation activities at Solid Waste Management Unit (SWMU) 145 (ST027) Building 575 JP-4 Tank Leak (the “site”) at Joint Base Charleston-Air (JBCA) (formerly called Charleston Air Force Base) (Figure 1).

The site is regulated under the Resource Conservation and Recovery Act (RCRA), as amended, and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The site is listed in RCRA Part B Permit SC3 570 024 460, dated July 31, 2019, executed with the South Carolina Department of Health and Environmental Control (SCDHEC), a delegated authority by the United States Environmental Protection Agency (USEPA) for RCRA Corrective Actions.

Because site groundwater contamination came from former petroleum underground storage tanks (USTs), the site has been delegated by SCDHEC to their UST Division, and is subject to SCDHEC UST Management Division regulations and policies (Groundwater Protection Division [GWPD] Site ID # A-10-AA-01829).

This 2022 Semi-Annual Groundwater Monitoring Report / Corrective Action System Evaluation (CASE) Report presents the results of the quarterly groundwater monitoring activities conducted in August 2022 and November 2022. Groundwater monitoring was completed in accordance with RCRA permit long-term monitoring (LTM) requirements, and also to evaluate the effectiveness of a biosparge system that was activated on March 7, 2017, to remediate the remaining groundwater contaminants of concern (COCs), which are benzene and naphthalene.

Quarterly sampling and analysis were completed in accordance with the SCDHEC-approved Draft Final Quality Assurance Project Plan Revision 1 Addendum to the SCDHEC UST Programmatic Quality Assurance Project Plan (QAPP) (Oneida Total Integrated Enterprises [OTIE], 2012), which has been subsequently modified by various monitoring report recommendations that were approved by SCDHEC. Most recently, the LTM program for 2022 was completed in accordance with the SCDHEC-approved (SCDHEC, 2022a) Annual Contractor Quality Assurance Plan (ACQAP) (FPM, 2022a) and the SCDHEC-approved (SCDHEC, 2022b) Site-Specific Work Plan (SSWP) (FPM, 2022b). The ACQAP and SSWP are addenda to the SCDHEC UST Management Division Programmatic Quality Assurance Program Plan, Revision 4.0 (SCDHEC, 2020).

1.1 Report Organization

The report has been organized into the following sections:

Section 1.0 Introduction Section 2.0 Site Background Section 3.0 Performance Monitoring Results Section 4.0 Site Performance Model Section 5.0 Remedial Process Optimization Section 6.0 Summary, Conclusions and Recommendations Section 7.0 References

FPM Remediations, Inc. 1-2 Contract No. FA8903-13-0006

Maps and illustrations are included in Figures, and tabulated data is included in Tables. Daily Reports and Field Notes are provided as Appendix A, Groundwater Sampling Logs are presented in Appendix B, Laboratory Analytical Results are included as Appendix C, and the Data Validation Report is presented in Appendix D. The SCDHEC Contractor Checklist is included as Appendix E.

1.2 Facility Information

JBCA occupies 3,731 acres approximately 10 miles northwest of the City of Charleston and has an approximate population of 5,500 that changes periodically as military operations vary from year to year and/or mission to mission. The facility is highly developed with most land used for military operations and housing. JBCA is surrounded by industrial, commercial, and residential properties that are part of the City of North Charleston, South Carolina.

1.3 Site Information

The site is located at Building 575 in the central portion of JBCA. The site is located within a designated aircraft maintenance area west of the major taxiways for primary Runway 15/33. The aircraft maintenance area is capped by 8 to 14 inches of concrete. Site location and site historical detail maps are provided as Figures 1 and 2, respectively. Semi-annual groundwater monitoring events have been conducted at the site since 1996. A biosparge system was installed in early 2017 to remediate residual groundwater contamination, followed by quarterly groundwater monitoring

(FPM, 2018).

FPM Remediations, Inc. 2-1 Contract No. FA8903-13-0006

2.0 SITE BACKGROUND

2.1 Site History

Several petroleum USTs were operated at the site on the north side of the Building 575 maintenance hangar. In 1977, a 10,000-gallon UST, used to store JP-8 jet fuel, was installed in a 6-inch-thick concrete vault. A 3,000-gallon UST and a 1,000-gallon UST were used previously at the site to store JP-4 jet fuel and Motor Gasoline (MOGAS), respectively. Both USTs were operated for approximately 30 years before they were removed from service in January 1988. Prior to removing the USTs, the Air Force suspected the 3,000-gallon JP-4 jet fuel UST was leaking due to a constant flux of water entering the tank. The leak was confirmed in January 1988 when the tank was removed and soils contaminated with JP-4 jet fuel were discovered. The 1,000-gallon MOGAS tank, which was removed at the same time, reportedly showed no signs of leakage.

According to Base personnel, some of the most heavily contaminated soils around the former USTs at the site were excavated and disposed of during the tank removals (General Environmental Laboratories, Inc. [GEL], 1988). The quantity of contaminated soils excavated and removed from the site was not reported.

Two 4,000-gallon fiberglass USTs (MOGAS and diesel fuel) were installed at the locations of the former 3,000-gallon and 1,000-gallon USTs at the site in April 1988. During leak testing in January 1996, it was discovered that both MOGAS and diesel were leaking from the tanks or transfer lines.

The source of the MOGAS contamination was due to a bad pipe coupling. The pipe coupling was replaced and the MOGAS tank was returned to service. The source of the diesel leak was not found and the tank was decommissioned. The entire site was decommissioned in 1997, and all tanks were removed in 1998 (Radian, 2000). A historical site features map is provided as Figure 2.

2.2 Site Hydrology, Geology, and Hydrogeology

The surface elevation at the site and the adjacent SWMUs averages about 40 feet (ft) above mean sea level. The site is relatively flat and is covered with 8 to 14 inches of reinforced concrete that completely surrounds Building 575. Surface drainage of the concrete pad around Building 575 is controlled by a series of storm drains and engineered surface drainage features. The concrete immediately surrounding Building 575 is gently sloped toward the open stormwater drain/sump (SWMU 22), which is located on the east and northeast sides of Building 575 (Figure 2). This storm drain forms the western edge of the former aircraft washrack adjacent to Building 575, and receives runoff from both the washrack (SWMU 20) and much of the concrete pad and aircraft apron adjacent to Building 575. This drain discharges into the Base sanitary sewer. The nearest surface water drainage feature, a drainage ditch, is located approximately 750 ft northwest of the site along Graves Avenue.

The site’s shallow stratigraphy (e.g., 0 to 34 ft below ground surface [bgs]) can be generally described as 8 to 14 inches of concrete overlying undifferentiated, moderately sorted sands and silty to clayey, fine to medium sands of the Ladson Formation. Underlying the concrete layer are 3 to 5 ft of gray to pale-brown, silty fine to medium sand with a trace of clay. The upper 1 to 2 ft of this sand unit appear to be backfill and/or reworked residual soils at several locations. Beneath the upper silty sand unit is a pale yellow-brown clayey sand unit that is about 4 to 7.5 ft thick. The water table of the surficial aquifer tends to occur in this clayey sand unit, and its physical characteristics (e.g., higher clay content) suggest that it may be less permeable than the overlying silty sand unit. Underlying the clayey sand unit are approximately 25 ft of pale-gray to yellow-

FPM Remediations, Inc. 2-2 Contract No. FA8903-13-0006 brown, silty, fine to medium sands. A plastic, low-permeability clay layer was encountered from

33.5 to 35 ft bgs in the soil boring for deep well MW20-08 (Versar, Inc., 1992). It is not known if this clay layer is laterally extensive or if it is associated with the basal, low-permeability soils that define the lower extent of the Ladson Formation and the upper portions of the confining Cooper Marl Formation. No soil borings that penetrate through this clay layer and into the Cooper Marl Formation have been completed at the site (Versar, Inc., 1992).

Groundwater at the site is encountered at average depths ranging from about 4 to 6 ft bgs. Water level data from 1990 through 1993 indicate that the water table at this site can fluctuate from 1 to 3 ft on a seasonal basis. The maximum observed change in water table elevation was 3.15 ft at well MW20-5 (Versar, Inc., 1992). The historic groundwater flow direction at the site has fluctuated from the southwest to the southeast, depending on the water levels in the site wells.

Fluctuations in flow direction may occur due to variable recharge rates at wells located close to unpaved areas versus wells that are not, but the prevailing flow direction has consistently been to the southwest/southeast.

The water level/light nonaqueous-phase liquid (LNAPL) gauging event conducted on August 23, 1995 indicated that the observed horizontal hydraulic gradient at the site is extremely low [0.0014 foot per foot (ft/ft)], particularly in the vicinity of the former UST and the adjacent SWMUs.

Vertical hydraulic gradients were observed at nested monitoring well MW20-18, which is screened in both the shallow (midpoint depth 8.2 ft bgs) and the deeper (midpoint depth 29.6 ft bgs) portions of the Ladson Formation, and the well pair MW20-03 and MW20-08, which are screened at 6.6 and 27.6 ft bgs, respectively. The vertical hydraulic gradient observed near MW20-18 was 0.0445 ft/ft, downward, while the vertical gradient near the well pair (MW20-03 and MW20-08) was observed to be 0.0371 ft/ft, downward. These vertical gradients are an order of magnitude greater than the observed horizontal gradient.

Ten in-situ aquifer hydraulic conductivity (“slug”) tests were conducted at groundwater monitoring wells MW20-03, MW20-06, MW20-08, MW20-09, MW20-11, MW20-14, MW20- 15, MW20-18 (shallow and deep), and MW20-21 at the site to assess the hydrogeologic characteristics of the surficial aquifer. The test data yielded estimated hydraulic conductivities ranging from 1 x 10-4 to 5 x 10-3 foot per minute (ft/min) at wells screened across the upper few feet of the surficial aquifer. In comparison, lower hydraulic conductivities of 1 x 10-4 to 9 x 10-4 ft/min were observed at the monitoring wells screened across deeper portions of the surficial aquifer (i.e., screen midpoints set at more than 20 ft bgs). The differences in hydraulic conductivity observed in shallow and deeper wells suggests the presence of at least two zones of slight lithologic variations so as to create differences in apparent hydraulic conductivity in the surficial aquifer. No distinct confining unit is present, but the changes in lithology with depth apparently have effected a measurable change in hydraulic characteristics with depth at the site (Parsons, 1997).

Assuming an estimated effective porosity of 30 percent for the clayey sand unit, and based on the hydraulic gradient of 0.0014 ft/ft, and the range of calculated hydraulic conductivities from the hydraulic conductivity tests, the range of calculated groundwater average linear flow velocities for the upper lithologic zone was estimated at 0.245 to 12.27 ft/year. The groundwater average linear flow velocities in the deeper, lithologic unit of the surficial aquifer would be similar to the low-end range velocities estimated for the upper flow zone (i.e., 0.245 ft/year) (Parsons, 1997).

FPM Remediations, Inc. 2-3 Contract No. FA8903-13-0006

2.3 Previous Investigation and Remediation Activities

Hydrogeological Investigation (1988) Several phases of environmental investigations have been conducted by various contractors at SWMU 145 (ST027). After the two USTs were removed and the fuel release was confirmed at the site (January 1988), GEL installed 14 shallow, hand-augered borings and 5 shallow groundwater monitoring wells (MW20-01 through MW20-05) to assess the impact of the tank leak on soil and groundwater quality (Figure 2).

Groundwater contamination was detected in four of the five monitoring wells. The highest concentration of dissolved benzene, toluene, ethylbenzene, and xylenes (BTEX) was detected in well MW20-03 at 43,630 micrograms per liter (µg/L). No BTEX compounds were detected in the groundwater at nearby well MW20-02 at that time. Although no measurable thicknesses of LNAPL were observed, it was noted that an oily sheen was present on the surface of groundwater samples collected from wells MW20-01 and MW20-03. The contractor reportedly screened soil samples from the 14 soil borings for the presence of fuel contamination. However, neither the field screening methods nor the results were published in their report.

Installation Restoration Program (IRP) Phase II (1992) Following the confirmation of groundwater contamination, ST027 was designated as an IRP site for continued investigation under a remedial investigation/feasibility study (RI/FS). An IRP Phase II and a Stage 2 RI/FS was conducted at the Base during 1989-1991, which included the site. Three additional groundwater monitoring wells were installed at the site in 1990 (Figure 2). Two of the wells (MW20-06 and MW20-07) were installed in locations presumed to be downgradient from existing wells, while the third well (MW20-08) was installed with a deep-screened interval to monitor the lower portions of the shallow aquifer. Two soil samples were collected for laboratory analyses from the soil boring for monitoring well MW20-08. Groundwater samples were collected from the three new wells and the five existing wells in 1990. Additionally, a sample of LNAPL was collected from well MW20-01 and analyzed for BTEX constituents. Analytical results indicated that the maximum total BTEX concentration in groundwater had declined slightly from 43,630 to 34,300 µg/L at monitoring well MW20-03. The two new site-perimeter wells, MW20- 06 and MW20-07, showed no detectable concentrations of BTEX compounds. Groundwater at monitoring well MW20-02 contained no detectable BTEX in 1988, and contained 262 µg/L of total BTEX in 1990. The concentrations of each of the BTEX compounds in the collected LNAPL sample were as follows: benzene, 1,100 µg/L; toluene, 4,100 µg/L; ethylbenzene, 1,600 µg/L; and xylenes, 11,000 µg/L. These concentrations were significantly below those expected in "fresh" MOGAS and above those expected in "fresh" JP-4 jet fuel (Versar, Inc., 1992).

Supplemental Groundwater Investigation (1993) EA Engineering, Science, & Technology, Inc. (EA, 1993) performed a supplemental groundwater investigation at ST027 to further delineate the extent of mobile LNAPL on the groundwater table.

Four additional shallow groundwater monitoring wells (MW20-09 through MW20-12) were installed and sampled from May through June 1993. The eight previously existing onsite monitoring wells (MW20-01 through MW20-08) were also gauged for groundwater levels during the investigation but not sampled. Minor quantities of mobile LNAPL were detected in wells MW20-01 (0.10 foot) and MW20-05 (0.05 foot).

FPM Remediations, Inc. 2-4 Contract No. FA8903-13-0006

Preliminary Bioventing Tests (1993) Engineering Science, Inc. (ES, 1993) performed preliminary bioventing field tests at the site in May 1993. Initial testing procedures included a soil/air permeability test and in situ microbial respiration tests to determine if the site was suitable for application of the bioventing technology.

A soil gas survey was conducted to identify areas where the subsurface soils were oxygen depleted and had elevated fuel hydrocarbon concentrations. Based on the soil gas survey results, one soil venting well (VW-I) and four permanent soil vapor monitoring points (VMPs) (three monitoring points - MPA, MPB, MPC; and one background point - BGl) were installed to perform the initial pilot testing (Figure 2). Several soil samples were collected from the unsaturated zone and analyzed for total recoverable petroleum hydrocarbons (TRPH), BTEX, nutrients, pH, and other physical parameters. A soil gas sample was collected from each of the four VMPs for analysis of BTEX and total volatile hydrocarbons (TVH). Additionally, portable field instruments were used to measure soil gas composition of oxygen (O2), carbon dioxide (CO2), and TVH during the soil gas survey and at the VMPs (Parsons, 1997).

Additional VMP Installations (1995) Eight additional permanent soil VMPs (MP-1 through MP-8) were installed in 1995 to further characterize the source area and the extent of soil vapor contamination. These VMPs were also field screened for O2, CO2, and TVH. Soil gas SUMMA canister samples were collected from three of the new vapor monitoring points (MP-3, MP-4, and MP-5) and analyzed using USEPA Method TO-3 for BTEX and TVH (Parsons, 1997).

Additional Monitoring Well Installations and Groundwater Sampling (1995) Nine new groundwater monitoring wells (MW20-14 through -21, including two wells screened at different depths at MW20-18) were installed in July 1995, to monitor groundwater geochemical indicators and to delineate dissolved contaminants in groundwater at the site (Parsons, 1997). One of the new monitoring wells (MW20-l8D) was installed as a deep, double-cased well to monitor groundwater quality in the lower zone of the surficial aquifer. A total of 20 shallow and two deep groundwater monitoring wells and 1 air sparging test well were installed at the site.

Groundwater samples were collected from all 22 groundwater monitoring wells in August 1995 and analyzed for fuel and nonfuel contaminants and for various inorganic and geochemical indicators to evaluate natural chemical and physical attenuation processes that were occurring.

Three confirmatory groundwater samples were also collected from three of the wells (MW20-02, MW20-04, and MW20-l2) in January 1996 to further quantify the presence or absence of chlorinated solvent contamination in groundwater (Parsons, 1997).

Samples of mobile LNAPL fuel (i.e., "free product") were collected and analyzed from two groundwater monitoring wells at the site. Mobile LNAPL was detected at monitoring wells MW20-01 (0.15 foot) and MW20-05 (0.1 foot) during the initial monitoring well gauging and purging event beginning on August 7, 1995. The LNAPL fuel layers were bailed from the wells on that date to allow relatively "fresh" samples of product to enter the wells from the formation. All of the wells were re-gauged and LNAPL samples were collected from the two wells on August 23, 1995 (Parsons, 1997).

Corrective Action Plan (CAP) (1997) and CAP Implementation (1997) The objective of the CAP was to develop and present a recommended risk-based remedial approach for fuel hydrocarbon and nonfuel organic contamination in soils and groundwater at and

FPM Remediations, Inc. 2-5 Contract No. FA8903-13-0006 downgradient from the site that is protective of both human health and the environment. Chemicals of potential concern in groundwater (benzene, toluene, ethylbenzene, naphthalene, chlorobenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, cis-1,2-dichloroethene) were identified in the

CAP.

In October 1997, a bioventing system to treat vadose zone soils was installed at the site (Parsons, 1997). The system was operated from 1997 through 2005 and was taken off-line and permanently abandoned in 2006.

Monitoring Well Installations 2004-2005 Groundwater monitoring wells MW20-22 and -23 were installed in March 2004. Groundwater monitoring well MW20-24 was installed in October 2004. Groundwater monitoring wells MW20- 25 through -27 were installed in April 2005.

Aggressive Fluid Vapor Recovery (AFVR) Remediation (2006-2007) AFVR was performed at four monitoring wells (MW20-04, MW20-11, MW20-09, and MW20-

10) in accordance with the AFVR Work Plan (Earth Tech, 2007a). AFVR is a dual-phase recovery technique that simultaneously extracts petroleum product, vapor, and groundwater by vacuum enhanced pumping. The AFVR events were completed using a standard vacuum truck with an approximate capacity of 3,000 gallons. AFVR was completed during October 2006, November 2006, and April 2007. A cumulative total of 225 gallons of separated free product were removed during the three events.

The first AFVR event following the approved modifications was performed on July 3, 2007. A total of three onsite wells were manifolded together to allow simultaneous extraction for the duration of the event. The multi-well manifold system was highly effective and after six hours of AFVR the vacuum truck was full and extraction was terminated. A total of 3,500 gallons of liquid were recovered from wells MW20-09, MW20-10, and MW20-11, which included approximately 350 gallons of separated free product (Earth Tech, 2007b).

Development of Site-Specific Target Levels (SSTLs) (2008) North Wind, Inc. calculated SSTLs for the remediation of naphthalene and benzene in groundwater at SWMU 145 (North Wind, Inc., 2008). The calculated SSTLs of 1,880 µg/L for benzene and 70 µg/L for naphthalene were accepted by the SCDHEC in a letter received by JBCA on February 4, 2008. SCDHEC would grant Conditional No Further Action (NFA) status for the site once the concentrations remained below the SSTLs for two consecutive semi-annual sampling events.

Historical sampling indicated that benzene concentrations at the site were below the calculated SSTL of 1,880 µg/L, while naphthalene concentrations remained above the calculated SSTL. As a result, naphthalene became the remaining COC for the site.

CAP (2008)

Groundwater remediation activities, targeting naphthalene in excess of the SSTL, were performed in September 2008 in accordance with the scope of work provided in the SCDHEC-approved CAP dated June 9, 2008. Groundwater remediation activities included the injection of BOS-200® (a Trap & Treat® in-situ remediation technology) into the surficial aquifer within four geographically separate treatment zones (A, B, C, and GW-2). Treatment Area A included the area adjacent to and surrounding wells MW20-03, MW20-08, MW20-09, and MW20-11. Treatment Area B included the area surrounding well MW20-27. Treatment Area C included the area surrounding well MW20-

FPM Remediations, Inc. 2-6 Contract No. FA8903-13-0006

05. Treatment Area GW-2 included an area north of Building 575 where three temporary injection wells were installed adjacent to GW-2 to target a high naphthalene groundwater concentration detected during pre-injection sampling activities. In November 2008, 45 days after completion of injection activities, URS conducted post-injection groundwater monitoring at monitoring wells MW20-05, MW20-08, MW20-09, MW20-11, and MW20-27. The results of the post-injection sampling indicated that naphthalene concentrations were below the SSTL (70 µg/L) in all monitoring wells except MW20-08 (URS, 2008).

Long-Term Management Monitoring Well Network Changes (2010/2011) Monitoring well abandonment and re-installation activities were performed by AECOM between December 2010 and March 2011 at the site. Monitoring wells were permanently abandoned to accommodate construction and asphalt paving of the area surrounding Building 575 and/or because they were no longer included in the compliance monitoring well network. Well abandonment activities (wells MW20-01, -02, -03, -05, -06, -07, -08, -09, -10, -11, -14, -15, -16, - 17, -18D, -18S, -19, -20, -21, -23, -25, -26 and ASW-1) were completed on January 7, 2011. Well re-installation activities (MW20-01R, -05R, -08R, -09R, -10R, -11R, -15R and -16R) were completed on March 30 and 31, 2011. Each replacement well was installed within approximately 3 ft horizontally of the location of the original well, and each was constructed to the same total depth as the original well (AECOM, 2011).

CAP Amendment (2017-2018) A CAP Amendment was submitted and approved by SCDHEC proposing the installation of a biosparge system (FPM, 2016). The purpose of the CAP amendment is to conduct remedial activities to remediate the site COCs to the benzene maximum contaminant level (MCL) (5 µg/L) and the SCDHEC naphthalene Risk Based Screening Level (RBSL) (25 µg/L) in order to achieve NFA at the site.

Three horizontal biosparge wells (BS-1, BS-2, and BS-3; Figure 4) were installed by Directional Technologies, Inc. between January 23 and February 7, 2017. Pilot holes for each well were drilled using a six-inch diameter drill bit at an entry angle between 30-35 degrees until the desired well depth of 25 ft bgs was reached. The drill string was then advanced joint by joint.

At the completion of each joint, the location of the drill head was obtained by the use of a walkover radio detection receiver. When the drill head reached the desired endpoint, the drill head and related tooling was removed for reaming and pullback. The well risers were constructed of solid three-inch inside diameter clean high-density polyethylene pipe and the well screen was constructed of the same material, with slot size of 0.010-inch and vented to allow pressurized air to escape.

After the initial ‘burn-in’ phase and monitoring of the system, the original compressor installed in the biosparge trailer (30-horsepower [HP] Rietschle DLR400) was found to produce too much air volume (approximately 260 standard cubic feet per minute [SCFM]) for the three horizontal biosparge wells. Soils at the site were identified as being more restrictive than initially designed for. As a result, the original compressor installed for the system was replaced with a smaller compressor (30-HP Busch Mink MP 1322 AP; approximately 160 SCFM) on March 20, 2017.

Notifications were made to AFCEC, the Base, and SCDHEC.

FPM Remediations, Inc. 2-7 Contract No. FA8903-13-0006

The installed biosparge system is continuously monitored remotely. The system controller (EOS ProControl®) emails a daily operating status to the FPM office and the system can be remotely turned on and off.

BTEX was added to the analyte list in the CAP Amendment to ensure consistency with the NFA requirements (i.e., concentrations remained below their respective MCLs/RBSLs).

The analytical results from March 2018, one year after biosparge system activation, indicated that only naphthalene remained above the SSTL of 70 µg/L and RBSL of 25 µg/L at monitoring wells MW20-01R (55.6 µg/L), MW20-10R (99.5 µg/L), and MW20-24 (78.4 µg/L). Naphthalene concentrations in wells MW20-01R and MW20-10R had not decreased from pre-biosparge levels.

Naphthalene in groundwater at monitoring well MW20-24 was non-detect during the baseline sampling event in August 2016, but more recent monitoring has indicated elevated naphthalene concentrations in groundwater.

In response to the lack of change in site COC concentrations observed in groundwater at monitoring wells MW20-01R and MW20-10R, an additional horizontal biosparge well (BS-4) (with similar specifications of the other three horizontal wells) was installed in April 2018 west of the original biosparge wells and closer to the referenced monitoring wells (FPM, 2018). Shortly thereafter, groundwater naphthalene concentrations in those wells decreased to levels below the RBSL, to 14.9 µg/L at monitoring well MW20-01R by September 2018, and to 10.5 µg/L at monitoring well MW20-10R by June 2018. Subsequent groundwater samples at these wells have shown continued decrease in naphthalene concentrations.

FPM Remediations, Inc. 2-8 Contract No. FA8903-13-0006

FPM Remediations, Inc. 3-1 Contract No. FA8903-13-0006

3.0 PERFORMANCE MONITORING RESULTS

3.1 Groundwater Monitoring Program

For this reporting period, groundwater monitoring was completed on August 11, 2022, and November 17, 2022. The biosparge system was turned off a minimum of 48 hours prior to each sampling event to allow groundwater to stabilize at the site.

In August 2022 and November 2022, groundwater samples were collected from two monitoring wells (MW20-08R and -24) (Figure 2) with SCDHEC concurrence of an optimized performance monitoring sampling network. Sampling and analysis were completed in accordance with the SCDHEC-approved ACQAPs and SSWPs (FPM, 2021a and 2021b).

3.2 Groundwater Monitoring Procedures

Groundwater samples were collected from the monitoring wells using low-flow purging and sampling methods using a peristaltic pump with dedicated Teflon®-lined polyethylene tubing to prevent cross-contamination. Information including sampling time, purge volume, measured field parameters, and general weather conditions are included in the field documentation provided as Appendix A.

Groundwater temperature, pH, oxidation reduction potential (ORP), specific conductivity, turbidity, and dissolved oxygen (DO) readings were measured via a flow-through cell and recorded periodically during purging activities. A groundwater sample was collected from the monitoring well after the field parameter readings had stabilized, as documented on the groundwater sampling forms (Appendix B) and summarized in Table 3. Stabilization was considered complete when pH varied to within 0.1 standard pH units, specific conductivity varied to within 3 percent, and turbidity remained below 10 nephelometric turbidity units (NTU) or varied within 10 percent for at least three consecutive measurements (adapted from SCDHEC UST Programmatic QAPP Rev.

2.0 and the USEPA Region 4 groundwater sampling procedures).

Groundwater samples were submitted to SGS North America, Inc. (SGS) of Orlando, Florida (formerly Accutest) for analysis. The samples were shipped in sealed coolers packed with ice under chain-of-custody via overnight courier to SGS. SGS’s laboratory holds Department of Defense (DOD) Environmental Laboratory Approval Program (ELAP) Certification (#L2242) and SCDHEC Certification (#96038001) for the USEPA SW-846 Method 8260D.

3.3 Investigation-Derived Waste (IDW)

During sampling activities, purge water was initially contained in a 5-gallon plastic bucket with a snap-on lid before being transferred to a temporary holding tank located at the JBCA Building 692 parking lot. The purge water will be discharged to the JBCA sanitary sewer system following laboratory analysis and approval from the North Charleston Sewer District and JBCA, or it will be disposed of at an off-base permitted facility. Other wastes generated during sampling events (i.e., sampling supplies, personal protective equipment, etc.) were disposed of as general refuse.

3.4 Water Level Measurements

Depth to groundwater measurements for the August 2022 and November 2022 events along with their calculated groundwater elevations are presented in Table 1. No free product was detected in any of the site monitoring wells during the water level gauging activities. The water level

FPM Remediations, Inc. 3-2 Contract No. FA8903-13-0006 measurements were used to develop the August and November 2022 water table elevation contour maps (Figures 3a and 3b). Groundwater flow direction at the site is generally to the southeast.

Historical water levels are presented in Table 2.

3.5 Geochemical Parameter Measurements

Recent and historical groundwater geochemical parameter measurements (temperature, DO, pH, ORP, specific conductivity, turbidity, methane, and sulfate) are presented in Table 3.

Measurements in August 2022 and November 2022 continued to indicate anaerobic geochemical conditions (e.g., low to negative ORP values, zero to very low DO concentrations below 0.7 mg/L) at groundwater monitoring wells MW20-08R and MW20-24. Groundwater redox conditions in August 2022 and November 2022 were moderate at well MW20-08R (-229.5 mV and 7.9 mV, respectively) and somewhat oxidizing at MW20-24 (82.6 mV and 48.9 mV, respectively).

3.6 Groundwater Monitoring Results

The August 2022 and November 2022 results are summarized in Table 4 and presented graphically in Figure 4. The historical laboratory analytical results are shown in Table 5.

During the August 2022 sampling event, the naphthalene concentration in groundwater at monitoring well MW20-08R (21.1 µg/L) met the SCDHEC RBSL of 25 µg/L. At monitoring well MW20-24, naphthalene exceeded the SCDHEC RBSL at 62.4 µg/L and 50.6 µg/L respectively for the parent and duplicate samples. During the November 2022 sampling event, the naphthalene concentration in groundwater at monitoring wells MW20-08R (34.1 µg/L) and MW20-24 (29.6 µg/L / 29.1 µg/L: parent/duplicate) both exceeded the SCDHEC RBSL. Overall naphthalene concentrations at the site have decreased since operation of the biosparge system began in 2017.

The reduction of COC concentrations at the site confirms the operation of the biosparge system has been effective; however residual contamination remains. The historical naphthalene concentrations are charted in Figures 5a, 5b, and 5c.

Benzene, ethylbenzene, toluene and xylene (total) concentrations in groundwater in site monitoring wells remained below their respective MCLs during both the August 2022 and November 2022 sampling events.

3.7 Quality Control/Quality Assurance

As part of the QA/QC sampling during the August 2022 and November 2022 sampling events, a blind duplicate sample was collected from monitoring well MW20-24 (sample ID ST27-MW20- 224). Other blind duplicate and matrix spike/matrix spike duplicate (MS/MSD) samples were collected as part of the larger sample sets for the August 2022 and November 2022 sampling events which included samples from several sites at JBCA. The August 2022 and November 2022 sampling events consisted of all JBCA sites sampled quarterly under this contract and was performed at the same time in one mobilization. Trip blanks (TB20220811, TB20220811A, and TB20221117) were included in the coolers containing the volatile organic compound (VOC) samples, an ambient blank (AB20220811) was collected at the end of the sampling day in August 2022. Due to a field error, an ambient blank was not collected during the November 2022 sampling event. Equipment blanks (EB20220811 and EB20221117) were collected at the end of the sampling day in August 2022 and November 2022.

FPM Remediations, Inc. 3-3 Contract No. FA8903-13-0006

The samples were stored in ice-filled coolers immediately after collection to maintain temperature criteria (4 ±2 degrees Celsius). The custody seals were applied to the coolers, and the coolers were shipped overnight to the analytical laboratory. Upon receipt, the laboratory confirmed the custody seals were present and intact and the temperature criteria were met.

Data validation was performed by the project chemist according to DoD QSM Version 5.4 for the groundwater sample laboratory results. Holding times, preservation methods, surrogate recoveries, laboratory control sample recoveries, matrix spike/matrix spike duplicate (MS/MSD) recoveries, method blanks, trip blanks, equipment blanks, field duplicates, instrument tuning, internal standards, and calibrations were reviewed. For each analysis performed, the following Data Quality Indicators (DQIs) were assessed: 1) laboratory analytical precision, 2) accuracy, 3) representativeness, 4) completeness, and 5) comparability (PARCC). Data qualifiers resulting from this review are summarized in Table 1 of the data validation report and were added to the results in Table 5. No deficiencies were noted during the data validation process for the samples and blanks related to this site, and 100% of the sample results are deemed acceptable for their intended use. An electronic copy of the laboratory analytical data for this monitoring period is included as Appendix C, and the data validation report is included as Appendix D.

FPM Remediations, Inc. 3-4 Contract No. FA8903-13-0006

FPM Remediations, Inc. 4-1 Contract No. FA8903-13-0006

4.0 SITE PERFORMANCE MODEL

Addition of the August 2022 and November 2022 groundwater monitoring results in the site performance model (Figure 6) shows that groundwater concentrations of naphthalene have decreased significantly at the site since the biosparge system startup in 2017. Naphthalene concentrations continue to fluctuate around the SCDHEC RBSL at two monitoring wells (MW20- 08R and -24). The two monitoring wells had naphthalene concentrations above the SCDHEC RBSL during the November 2022 sampling round, and naphthalene concentrations below the SCDHEC RBSL at MW20-08R and above the SCDHEC RBSL at MW20-24 during the August 2022 sampling round.

As noted in the site performance model, Plan A (for remediation of COCs at the site) was the installation of a biosparge system, which has reduced overall concentrations of both benzene and naphthalene in groundwater at the site. Site-wide benzene concentrations remain below the MCL (5 µg/L). Naphthalene concentrations at MW20-24 and MW20-8R are currently above the SCDHEC RBSL (25 µg/L) (Table 4, Figures 4 and 6). Based on naphthalene concentrations at the Site, a mobile biosparging effort was used to target monitoring well MW20-08R by supplementing this location with additional dissolved oxygen in December 2021. The mobile biosparge trailer was operated for an entire day (6-9 hours continuously) at the well. This effort was part of the Plan B approach to reduce COCs at the site.

Risk Mitigation Measures The main biosparging system continues to be operated on a rotating schedule (5 days on and 2 days off) to allow more movement of dissolved oxygen at the Site.

Monitoring well MW20-24 is located over 400 feet from the former UST location. Continuing naphthalene exceedances and the observation of blue tinted water in June 2017 in this well suggest that surface water runoff was entering and impacting the well. To address this condition, the surface completion of MW20-24 was replaced on June 9, 2022. The work was completed by Terry Environmental with oversight by FPM personnel. The outer casing was noticeably corroded. The expectation is that now that the well is sealed off from airfield runoff, a reduction in detected naphthalene will be observed; however, this was not observed in the data from the two monitoring events documented in this report. The remaining well with naphthalene detections above criteria (MW20-8R) is located cross-gradient from the former UST location and samples have continued to show naphthalene detections, despite the well’s location in proximity to a horizontal biosparge well. The mobile biosparging effort described in the previous paragraph also did not result in a sustained reduction of naphthalene concentrations. The possibility of another contributing source that is impacting the well has been discussed. Future groundwater monitoring rounds will provide additional groundwater data to confirm concentration trends and effectiveness of the treatment.

FPM Remediations, Inc. 4-2 Contract No. FA8903-13-0006

FPM Remediations, Inc. 5-1 Contract No. FA8903-13-0006

5.0 REMEDIAL PROCESS OPTIMIZATION (RPO)

Remedial Process Optimization (RPO) is the systematic evaluation and enhancement of site remediation processes to ensure…