W912DR18R0055_-_Attachment_X_-_DRAFT_2017_OU8_GWMR_8.4.18.docx

DRAFT

2017 GROUNDWATER MONITORING REPORT

FOR

OPERABLE UNIT 8

DEFENSE SUPPLY CENTER RICHMOND

Prepared For

Defense Logistics Agency

And

Defense Supply Center Richmond

August 2018

DRAFT

2017 GROUNDWATER MONITORING REPORT

FOR

OPERABLE UNIT 8

DEFENSE SUPPLY CENTER RICHMOND

Prepared For:

Defense Supply Center Richmond Defense Logistics Agency United States Army Corps of Engineers, Baltimore District

Prepared By:

Arcadis U.S., Inc.

Contract No. W912DR-13-D-0019 Task Order No. 0005

August 2018

Table of Contents

List of Figures

List of Tables

List of Appendices

APPENDIX A: FIELD DOCUMENTATION

APPENDIX A1: WELL SAMPLING FORMS

APPENDIX A2: EQUIPMENT CALIBRATION RECORDS

APPENDIX B: LABORATORY ANALYTICAL DATA SUMMARY PACKAGES

APPENDIX C: IDW DISPOSAL DOCUMENTATION

APPENDIX D: DATA VALIDATION REPORTS

APPENDIX E: DATA QUALITY EVALUATION

Acronyms and Abbreviations

Draft 2017 Groundwater Monitoring Report Operable Unit 8, Defense Supply Center Richmond August 2018

3-3

INTRODUCTION

Arcadis, U.S., Inc. (hereinafter referred to as Arcadis) has prepared this report to document the activities, procedures, and results of monitoring activities for the Defense Logistics Agency (DLA) Restoration Program at the Defense Supply Center Richmond (DSCR), hereinafter referred to as the Site, located in Chesterfield County, Virginia. The work was performed in accordance with the scope of work dated June 22, 2015 from the United States (U.S.) Army Corps of Engineers (USACE) Baltimore District, and all amendments and question and answer sets under the USACE, Baltimore District Contract No. W912DR-13-D-0019, Task Order No. 0005, awarded September 25, 2015.

This report presents the results of the annual groundwater monitoring performed in April 2017 and October 2017 at Operable Unit (OU) 8 at the DSCR installation located near Richmond, Virginia. DSCR is located approximately 8 miles south of the City of Richmond, Virginia, and is the aviation demand and supply chain manager for DLA. OU 8 is defined as the groundwater beneath and downgradient of the Acid Neutralization Pits (ANPs), located in the northern portion of the installation. The ANPs are referred to as OU 5. Figure 1-1 shows the location of all OUs including OU 8 and OU 5 at the DSCR installation.

DSCR installation was added to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) in 1987 by the facility's former name, Defense General Supply Center. In 1990, DSCR, DLA, United States Environmental Protection Agency (USEPA), and Virginia Department of Environmental Quality (VDEQ) signed a Federal Facilities Agreement (FFA) that established DLA as the lead agency responsible for evaluating, selecting, and executing response actions to assure protection of human health and the environment at the installation. The lead federal agency for DSCR is DLA. USEPA is the lead regulatory agency, and VDEQ is designated as a support agency.

Site Background The following sections provide a summary of OU 8 site geology and hydrogeology, environmental history, selected remedies, and implemented remedial actions. Figure 1-2 shows the current OU 8 site map and associated site features.

Geology and Hydrology Site Geology – The general stratigraphy of coastal plain sediments in the OU 8 area is as follows:

· Silty sand, sandy silt, and silty or fat clay from the ground surface to depths ranging from approximately 12 to 30 feet below ground surface (bgs).

· Upper water bearing unit (UWBU) – Poorly graded sand with gravel, interlayered with poorly graded gravel. The thickness of this unit is approximately 2 to 19 feet. The top of the unit is approximately 13 to 19 feet bgs, and the bottom of the unit is approximately 21 to 28 feet bgs. The unit is present throughout OU 8 but is absent to the north.

· Silty and/or fat clay. The thickness of this unit is approximately 5 to 10 feet. The top of the unit is approximately 21 to 28 feet bgs, and the bottom of the unit is approximately 26 to 36 feet bgs. This unit is present beneath the poorly graded sand with gravel unit and is absent in the northernmost part of the installation.

· Lower water bearing unit (LWBU) – Poorly graded sand with gravel and silty sand, poorly graded sand with gravel, and/or poorly graded sand with gravel interlayered with poorly graded gravel. The thickness of this unit is approximately 10 to 25 feet. The top of the unit is approximately 26 to 36 feet bgs, and the bottom of the unit is approximately 46 to 52 feet bgs. This unit is present throughout OU 8 and the northern portion of the installation.

The fining-upward stratigraphic sequences indicate fluvial environments of deposition for the coastal plain sediments. Two such sequences are identified in the site stratigraphy. Each sequence includes poorly graded sands with gravels deposited as channel lag or point bars and overlying sands, silts, and clays deposited in over-bank environments. Beneath the coastal plain sediments, from approximately 46 to 52 feet bgs, is saprolite weathered from the underlying Petersburg Granite. Locally, bedrock was not encountered in borings, and the thickness of saprolite and depth to bedrock is unknown.

Site Hydrogeology – The hydraulic conductivity (permeability) of the sand with gravel portion of the UWBU at OU 8 was measured by aquifer testing during a pilot test study performed in 1995. The test results yielded hydraulic conductivities ranging from approximately 25.92 – 53.28 feet per day (ft/d) with a geometric mean hydraulic conductivity of approximately 34.56 ft/d. The general groundwater flow direction in UWBU is towards the east and northeast.

The hydraulic conductivity of the LWBU was estimated to be 7.3 to 16.5 ft/d. The general direction of groundwater movement in the LWBU is typically north-northeast. A comparison of the potentiometric surfaces in the UWBU versus the LWBU shows that the UWBU potentiometric surface was approximately 10 feet higher than the LWBU. These relative potentiometric surface elevations indicate that the vertical component of hydraulic gradient form the UWBU to the LWBU is downward.

OU 5 Site History OU 8 is the designation for groundwater beneath and downgradient of OU 5 which includes the ANPs and the surrounding soil. The ANPs consist of two former concrete tanks that received wastewater from metal cleaning (including paint and rust removal) operations at Warehouse 65 from 1958 to the early 1980s. The solvents used during metal cleaning operations are not documented; and solvents may have been transported from other installation locations and disposed of in the ANPs. The ANPs were closed in 1985; residual sludge was washed from the tank bottoms and removed, and the tanks were backfilled with clean soil. At the time of closure, the concrete sides and bottoms of the tanks were found to be broken and cracked (MACTEC, 2006a). A Remedial Investigation (RI) of the ANPs was completed in 1989 and the results showed low levels of chlorinated volatile organic compounds (VOCs), including tetrachloroethene (PCE) and trichloroethene (TCE), in the soil surrounding the tanks.

OU 8 Site History Subsequent site investigations, including RI, Feasibility Study (FS), and the Supplemental FS, identified impacts to groundwater near Warehouse 65. The investigation results showed that chlorinated VOCs in the shallow groundwater (less than 25 feet bgs) had extended from the ANPs to the northeast and were limited to the UWBU. The primary compounds of concern in the UWBU at OU 8 are VOCs, specifically TCE and vinyl chloride (VC). Additionally, PCE and cis-1,2-dichloroethene (cis-1,2-DCE), have been detected above USEPA Maximum Contaminant Levels (MCLs).

1997 – 2004 Dual-Phase Extraction System Interim Measure – A Dual Phase Extraction (DPE) system was operated at OU 8 from June 1997 through January 2004 to address the UWBU chlorinated VOC contamination. It was initially operated as a pilot system and then continued as an interim action till January 2004, when it was shut down to evaluate the potential rebound of VOC concentrations. The associated DPE wells (DP1 through DP12) are shown on Figure 1-2. Based on the results of rebound testing, it was determined that rebound was not significant in aerial extent and restarting of the DPE system was not recommended. The DPE system was decommissioned in February 2008. The operation of the DPE system did not appear to have any effect on the potentiometric surface of the LWBU suggesting continuity in the clay aquiclude underlying the UWBU.

2006 Focused Feasibility Study – Semi-annual groundwater monitoring activities were conducted at OU 8 from 2004 to 2006 during the DPE system rebound evaluation to monitor the groundwater contamination. A revised human health baseline risk assessment (HHBRA) and revised Focused Feasibility Study (FFS) (MACTEC, 2006a) were completed in 2006 based on the results of the investigations and groundwater monitoring activities. Remedial action objectives (RAOs) were established in the FFS to address impacted groundwater associated with OU 8. The RAOs, which take into consideration the future use of the installation, include the following:

· Prevent unacceptable risk to human health and the environment from exposure to VOCs in groundwater; and

· Reduce groundwater VOCs within OU 8 plume to meet chemical-specific applicable or relevant and appropriate requirements (ARARs).

2007 Record of Decision – Based on the evaluation of alternatives presented in the revised FFS, DLA and USEPA, with concurrence from VDEQ, selected institutional controls (ICs) and monitored natural attenuation (MNA), with in-situ bioremediation (ISB) as a possible contingency to be the preferred remedy to address chlorinated solvent-impacted groundwater at OU 8. This remedy was specified in the OU 8 Record of Decision (ROD) (DSCR, 2007). A two-tiered approach was outlined in the ROD to confirm MNA. In tier 1, natural attenuation processes would be confirmed and attenuation rates determined during a three-year period (semi-annual monitoring events). Annual monitoring would begin in Tier 2 (beginning in Year 4). A Contingency Work Plan was proposed at the onset of Tier 2 if trigger criteria outlined in the ROD were met.

2007 Institutional Controls Implementation – The selected remedy includes implementation and enforcement of following institutional controls (ICs):

· Potable groundwater use has been prohibited installation-wide.

· Land use is restricted solely for nonresidential purposes until conditions allow for unlimited use and unrestricted exposure to groundwater.

· Land use controls (LUCs) will be attached to the property deed to restrict groundwater use and prohibit residential development and land use for schools or childcare facilities, should the property change ownership in the future before completion of the remedy.

· An assessment by the installation environmental group is required before construction activities can be undertaken at OU 8 to ensure that conditions will not present an unacceptable risk to construction workers. Prior to any excavation, monitoring data will be reviewed to determine potential vapor hazards and any associated health and safety requirements.

Annual inspections are conducted, in accordance with the ROD and the Final Environmental Site-Wide Land Use Control (LUC) Remedial Design (AECOM, 2015) to determine whether the institutional controls remain effective and that land and groundwater use restrictions are being achieved. The annual inspections describe identified deficiencies or violations and proposed measures or corrective actions taken or required. In the event of a deficiency or violation, the installation will take appropriate corrective action. The results of the inspections are presented under separate cover in an Annual LUC Inspection Report.

2008 – 2014 Warehouse 65 Source Area Identification – Additional monitoring well and direct push technology (DPT) site characterization activities were conducted from 2008 - 2011 during the MNA evaluation monitoring phase in accordance with the ROD and subsequent Remedial Design/Remedial Action Work Plan (RD/RAWP) (Earth Tech, 2008a). Three separate areas (north of Warehouse 65, Warehouse 66, and former Building 75) were identified as potential additional sources based on the investigation data and groundwater monitoring data. Interviews conducted with the installation personnel revealed that vehicle paint stripping operations were conducted in the former open cylinder storage area located north of Warehouse 65 as well as in the warehouse. The analytical results showed elevated levels for PCE, TCE, and cis-1,2-DCE in the groundwater samples collected in the open cylinder storage area. This area (north of Warehouse 65 source area) was determined to be a second potential source to the OU 8 groundwater contamination.

In 2014, additional DPT and monitoring well site characterization activities were performed to further evaluate the three suspected source areas (north of Warehouse 65, Warehouse 66, and former Building 75) (AECOM, 2015). The investigations concluded that none of the three suspected areas were contributing as additional sources of contamination. The investigation findings pointed toward the likely presence of a hydraulically upgradient source area underneath Warehouse 65; however, this source was unable to be located.

2011 Explanation of Significant Differences – In accordance with the ROD, the biological and geochemical parameters in groundwater were monitored from September 2008 to March 2010 over a three-year period for evaluation of MNA as the site remedy. Evaluation of MNA parameters from monitoring data indicated that groundwater geochemical conditions were not conducive to biodegradation. In addition, absence of daughter products in most of the OU 8 groundwater plume did not support the occurrence of biodegradation throughout the plume. Evaluation of the September 2008 to March 2010 groundwater data further indicated that VOC concentrations are increasing in many pre-sentinel wells and VOCs could migrate off installation at concentrations exceeding MCLs. Thus, based on the results of the 2009 and 2010 monitoring, the contingency remedy trigger criteria were met. Thereafter, an Explanation of Significant Difference (ESD) was issued in 2011 requiring the implementation of ISB as the contingency remedy (DSCR, 2011).

2010 – 2014 ISB Remedy Implementation –Injection and monitoring wells were subsequently installed in the OU 8 source area (downgradient of the ANPs and the suspected Warehouse 65 source area). In April/May of 2010, an ISB pilot test was conducted in these source areas to test the effectiveness of ISB as a contingency remedy. Approximately 6,700 gallons of 3 percent (by volume) edible oil emulsion were injected to evaluate the effectiveness of organic carbon addition to the contaminant degradation processes at OU 8. Subsequent monitoring after the pilot test confirmed the general efficacy of the ISB remedy. The pilot test demonstrated the ability of the emulsified vegetable oil (EVO) injection to effectively reduce high concentrations of VOCs in groundwater and stimulate complete reductive dechlorination.

Full-scale ISB using 3 percent (by volume) EVO was then initiated as a contingency remedy per the RD/RAWP Addendum (AECOM, 2013) and included the installation of additional monitoring and injection wells. Four treatment areas (TAs) were selected for substrate injection and implemented from July 2013 – April 2014. These areas included:

· TA 1 – Chlorinated VOC hotspot near OU 8-MW-120 (approx. 15 to 25 feet bgs);

· TA 2 – Chlorinated VOC plume spine near OU 8-MW-121 (approx. 15 to 25 feet bgs);

· TA 3 – Chlorinated VOC plume spine near OU 8-MW-113 (approx. 15 to 25 feet bgs);

· TA 4 – Chlorinated VOC hotspot near OU 8-MW-102 In accordance with the ESD and the RD/RAWP Addendum, semi-annual groundwater monitoring activities were conducted at OU 8 from 2013 onwards to evaluate the contaminant degradation following implementation of the contingency remedy and remedial effectiveness evaluations presented in annual monitoring reports. The 2015 Groundwater Monitoring Report (AECOM, 2017a) presented a remedial evaluation based on March/April 2015 and October 2015 semi-annual groundwater monitoring events and January 2015 and July 2015 quarterly fence line monitoring data and included a comprehensive assessment of the remedy implementation and its effect on plume stability as follows. In response to the EVO based ISB, significant decline in PCE/TCE concentrations occurred in TAs 1, 2, and 3 and the downgradient areas. The concurrent increase in cis-1,2-DCE concentration without significant generation of VC or ethene in these areas suggested that reductive dechlorination process may have slowed or stalled at the cis-1,2-DCE stage. At TA 4 in the southern lobe, PCE concentration has generally increased showing a limited effectiveness of reductive dechlorination, except at well MWANP-17 (where substrate was directly injected). This limited effect may be attributed to the complex flow regime in the area. Overall, and based on the USEPA 1998 MNA Evaluation Technical Protocol (USEPA, 1998), MNA of OU 8 TAs showed limited to strong evidence of reductive dechlorination. Inadequate substrate (declining TOC concentrations) and the presence of cis-1,2-DCE stall (potentially due to lack of bioaugmentation) have been identified as the potential limiting factors to explain the stall in progress of reductive dechlorination.

The likely presence of a continuing unknown source underneath Warehouse 65 also appeared to be impeding the overall effectiveness of the remedy in-place for the OU 8 groundwater plume. This was evident from the continuing expansion of the OU 8 plume along the northeast edge that had migrated beyond the installation boundary. Based on more recent groundwater data, the northwest edge of the plume also appeared to be expanding as well.

2015 – 2016 North Lobe and South Lobe Pump Tests – Between 2015 and 2016, two long-term pilot pump tests (USACE, 2015; Arcadis, 2015) were initiated in the plume’s northern and southern lobes to verify pumping rates in discrete strata, radius of influence, contaminant migration and hydraulic control. The northern lobe pilot pump test was started in June 2015 and the southern lobe pilot pump test was started in May 2016. Both pilot pump tests are currently running to maintain hydraulic control of both lobes of the dissolved phase plume and mitigate any further offsite migration.

2016 Bio-enhanced Directed Groundwater Recirculation Pilot Test – A review of historical site data concluded that very little source mass remained around the former ANPs and suggested a larger portion of the source mass may be under F Bay of Warehouse 65. A pre-design investigation was completed in August 2016 to support this pilot test and ensure appropriate placement of pilot test wells. During the pre-design investigation, chlorinated VOCS were measured in both vadose zone soil and groundwater under F Bay in Warehouse 65. Based on a review of historical maps showing operational layout of the interior of Warehouse 65, there was a vitrified clay pipe (VCP) that served as a waste line from inside the building to the former ANPs outside the building. This VCP waste line is believed to be the source of the OU 8 groundwater plume. Between October and December 2016, the ISB remedy was optimized with the installation of a bio-enhanced directed groundwater recirculation (BDGR) system in the Warehouse 65 source area (Arcadis, 2017b).

Purpose and Objectives In accordance with the ESD and the RD/RAWP Addendum, semi-annual groundwater monitoring activities have been conducted at OU 8 from 2013 onwards to monitor contaminant concentrations, plume extent and movement, and assess remedy optimization and natural attenuation of VOCs, in OU 8. This report summarizes the analytical data collected for the semi-annual groundwater monitoring and fence line soil vapor monitoring events during the April 2017 and October 2017.

Figure 11: OU Location Map

Figure 12: OU 8 Site Map

FIELD ACTIVITIES

The OU 8 annual monitoring activities comprise of two semi-annual groundwater monitoring events, and quarterly fence line groundwater and soil vapor monitoring events. The groundwater sampling and analysis plan for the semi-annual groundwater monitoring events and the quarterly fence line monitoring events is presented in Table 2-1 and locations of monitoring wells planned for April and October semi-annual sampling events shown on Figure 2-1. In 2017, the two semi-annual groundwater monitoring events were completed by Arcadis in April 2017 and October 2017 and were performed according to the project planning documents (Arcadis, 2016).

Fence line groundwater monitoring and vapor monitoring events were conducted in January 2017 and July 2017. A discussion of associated field activities is presented in greater detail in the following sections.

Annual Groundwater Monitoring Events The Spring annual groundwater monitoring event was conducted from 28 March 2017 through 6 April 2017 and consisted of gauging and sampling of 82 monitoring wells. The Fall annual groundwater monitoring event was conducted from 2 October 2017 through 5 October 2017 and consisted of gauging and sampling of 76 monitoring wells (Table 2-1). Any deviations from the planned scope of each monitoring event are presented in the non-conformances section (Section 2.1.5) below.

Field activities included groundwater elevation measurements, monitoring well inventory and inspections, groundwater sampling and analysis, and investigation-derived waste (IDW) containment and disposal. A discussion of each field activity is presented in greater detail in the following sections for both annual groundwater monitoring events.

Groundwater Elevation Measurements During the Spring 2017 event, static groundwater level measurements were collected from 81 out of the planned 82 monitoring wells on 3 March 2017 prior to sampling. These included 80 UWBU wells and 2 LWBU wells. Gauging data is not available for the following wells in the Spring 2017 event:

· MWANP-15 was unable to be located during the Spring gauging event.

During the Fall 2017 event, static groundwater level measurements were collected from 75 out of the planned 76 monitoring wells on 3 October 2017 prior to sampling. These included 69 UWBU wells and 2 LWBU wells. The following wells were not able to be gauged in the Fall 2016 event:

· MWANP-15 was unable to be located during the Spring gauging event.

Depth to groundwater measurements were collected from the top of casing (TOC) of each well using an electronic water level meter. Respective groundwater elevations are provided but may be inaccurate due to discrepancy and suspected accuracy issues in TOC elevations previously reported. Elevation discrepancies have been observed during review of several previous reports and use of previous elevation data results in groundwater elevations that do not match previous conceptual site models. The depth to groundwater measurements and other well construction information including total well depths, screen intervals and well diameters for each well included in the OU 8 semi-annual groundwater monitoring program are presented in Table 2-2. Groundwater contours for Spring 2017 and Fall 2017 are presented on Figures 2-2 and 2-3. Monitoring wells with discrepancy and/or accuracy issues were not used when determining groundwater contours.

Monitoring Well Inventory and Inspection An inventory of all monitoring wells planned for sampling at OU 8 was conducted prior to the groundwater sampling activities. The well inventory and inspection was conducted to determine if all wells planned for sampling were accounted for, properly identified, and in good condition. The following conditions were inspected during the inventory and inspections results were noted in well sampling forms:

Surface Completion Well Seal Well Cap Lock Well Monument Well Labeling Groundwater Sampling and Analysis Activities During the Spring 2017 event, groundwater samples were collected from 80 out of the planned 81 monitoring wells between 3 April 2017 to 7 April 2017. The following issues were noted with locating the 81 monitoring wells planned for sampling:

· As previously stated, MWANP-15 was not able to be located and was therefore not sampled.

During the Fall 2017 event, groundwater samples were collected from 75 of the 74 planned monitoring wells between 3 October 2017 to 5 October 2017. As previously stated, MWANP-15 was not able to be located and was therefore not sampled.

Groundwater samples were collected in accordance with USEPA recommended low-flow groundwater sampling procedures and in accordance with the project planning documents (Arcadis, 2016). This method produces minimal well drawdown and minimizes loss of VOCs during sampling. Monitoring wells with depths to water greater than 18 to 20 feet below the TOC were sampled using Proactive® Monsoon submersible pumps with control units that allowed regulation of the groundwater flow rate and disposable 3/8-inch tubing. Smaller diameter wells were sampled using Geopump® peristaltic pumps and disposable or dedicated 0.25-inch Teflon-lined low-density polyethylene (LDPE) tubing.

Groundwater samples were collected, preserved, packaged, and shipped in accordance with the project planning documents under chain-of-custody conditions (Arcadis, 2016). Chain-of-custody records were included with each shipment of sample coolers to the off-site Department of Defense Environmental Laboratory Accreditation Program (DoD ELAP)-certified analytical laboratory. All laboratory summary data packages including chain of custody records are included in Appendix B. Analytical results are also tabulated and included as Tables 2-3 through Table 2-16.

Field Water Quality Parameters: During groundwater sampling, field parameters were measured using Horiba® U53 or equivalent water quality meters that were calibrated at the beginning of each day with manufacturer auto-calibration solution. The following field parameters were recorded:

pH Specific conductivity Oxidation-reduction potential (ORP) Temperature Dissolved oxygen (DO) Turbidity Groundwater samples for field tests and laboratory analyses were collected after the parameters stabilized. Stabilization was defined as three successive readings within 0.3 percent (%) for temperature, <0.3 feet of drawdown, 0.1 units for pH, 10 millivolts for ORP, 3% for conductivity, and 10% for DO, and 10% turbidity. The sample collection forms are included in Appendix A1. The instrument calibration data is presented in field notes included as Appendix A2.

Despite using low-flow sampling techniques, turbidity readings of less than 20 nephelometric turbidity units (NTUs) could not be achieved in some wells. For these wells, each well was pumped to achieve the lowest possible stabilized turbidity reading and groundwater samples were collected after three successive stabilized readings.

ISB Performance Monitoring Parameters: All groundwater samples from OU 8 were analyzed by USEPA SW-846 Method 8260B for VOCs at the DoD ELAP-certified laboratory. In addition, all groundwater samples were analyzed for following ISB performance monitoring parameters at the off-site laboratory:

Anions [chloride and sulfate] (SW-846 Method 9056A);

Dissolved gases [ethane, ethene and methane] (USEPA Method RSK-175); and Total Organic Carbon (SW-846 Method 9060A).

In addition to the off-site laboratory analyses above, an on-site spectrophotometer (Hach Model DR 2800) was also utilized to analyze for the following ISB performance monitoring field parameters in both spring and fall events:

Ferrous Iron (Hach Method 8146) Nitrate/Nitrite (Hach Method 10020) Total Alkalinity (Hach Method 8203) Sulfate/Sulfite (Hach Method 8051) Manganese (Hach Method 8034) Additional Source Areas Assessment Parameters: Per the project planning documents (Arcadis 2016) and the 2013 RD/RAWP Addendum (AECOM, 2013), six select UWBU wells at OU 8 – OU 8-MW-50, OU 8-MW-67, OU 8-MW-102, OU 8-MW-120, OU 8-MW-123 and OU 8-MW-124 were also analyzed for following non-VOC parameters to evaluate UWBU groundwater at the three historical suspected source areas – north of Warehouse 65, Warehouse 66 and Former Building 75.

Semi-volatile organic compounds (SVOCs) – Base, Neutral and Acid (BNA) extractables (SW-846 Method 8270D);

SVOCs – Poly-Aromatic Hydrocarbons (PAHs) via Selective Ion Monitoring (SIM) (SW-846 Method 8270D);

Polychlorinated Biphenyls (PCBs) (SW-846 Method 8082A);

Pesticides (SW-846 Method 8081B); and Metals including Mercury (SW-846 Methods 6010LL and 7470A).

Investigation-Derived Waste Management and Disposal Following each sampling event, all IDW was containerized, sampled and analyzed, and properly disposed off-site. IDW generated during the Spring and Fall semi-annual field activities consisted of purge water from sampling activities and decontamination fluids. IDW was containerized in a 500-gallon poly tank and labeled for subsequent off-site disposal. The IDW disposal was conducted in accordance with the planning documents and DLA directives.

Following the Spring and Fall sampling events, waste characterization samples were collected at the end of each groundwater sampling event and analyzed for VOCs, SVOCs (BNA), SVOCs (PAHs via SIM), Metals (including Mercury), PCBs, pesticides, total organic carbon, select anions (chloride and sulfate) and dissolved gases (methane, ethane and ethene). The analytical summary data packages are included in Appendix B.

Using the analytical results and generator knowledge, a non-hazardous waste profile was generated and submitted to the waste hauling subcontractor. Utilizing the waste profile, 463 gallons of IDW water were disposed off-site following the Spring sampling event (which comprised IDW from OU 6, OU 7 and OU 8 groundwater monitoring) and 164 gallons of IDW water were disposed off-site following the Fall sampling event (OU 8 groundwater monitoring only). Appendix C presents the IDW disposal documentation including the waste profile and waste manifests.

Soil Vapor Monitoring Events Vapor monitoring (field readings) had been conducted since 2013 at OU 8 fence line, Warehouse 65, Warehouse 66 and Dervishian Army Reserve Center (ARC) related vapor monitoring points (VMPs) as detailed in the 2013 RD/RAWP Addendum (AECOM, May 2013) to monitor for potential accumulation of VOC or methane vapors as a result of ISB remedy implementation near the buildings (Warehouse 65, Warehouse 66 and Dervishian ARC) and off-site residences along the Strathmore Road. The locations of all OU 8 VMPs are shown in Figure 2-4.

Since 2016, the vapor monitoring of VMPs associated with Warehouse 65 is implemented as part of the quarterly monitoring associated with the Building 65 sub-slab depressurization system (SSDS). Results of VMP monitoring associated with Warehouse 65 are reported under separate cover in the Annual SSDS Monitoring Report.

Further, due to the limited effectiveness of the ISB remedy implemented as TA 4 near Warehouse 66 (AECOM, 2015), and based on the historic vapor monitoring data and previous building vapor intrusion (VI) investigations, there does not seem to be any potential for accumulation of VOCs or methane vapors in Warehouse 66. Thus, vapor monitoring of Warehouse 66 VMPs was discontinued in 2016.

The fence line vapor monitoring consisted of 19 VMPs; however, based on USEPA comments indicating that the existing fence line VMPs are too shallow for beneficial use for VOC VI evaluations, the VMP network was modified to incorporate four new deeper VMPs along the fence line adjacent to existing VMPs 117, 115, 107, and 103 (AECOM, 2016c). Since 2016, the fence line vapor monitoring program has been modified to only include the four shallow/deep VMP pairs.

Vapor monitoring was conducted four times during 2017 concurrent with semiannual groundwater monitoring quarterly fence line groundwater monitoring at the four shallow/deep VMP pair locations along the fence line in January 2017, June 2017, September 2017 and December 2017. Water was present in VMPs 197, 107, and 196 during the September 2017 monitoring event and were therefore unable to be monitored. Vapor monitoring was completed using dedicated Tedlar bags and field screened using a MultiRAE® Plus photo-ionization detector (PID) for field measurements of VOCs, Hydrogen Sulfide (H2S) and Carbon Monoxide (CO) and a Lantec® GEM-2000 multi-gas meter for field measurements for Methane (CH4), Oxygen (O2), and Carbon Dioxide (CO2) percentages in air. The VMP monitoring results for January 2017, April, July 2017 and October 2017 are presented in Table 2-17.

Variances/Non-conformances A list of any variances and non-conformances associated with the analytical data or fieldwork are listed below.

· During the Spring and Fall sampling event, monitoring well MWANP-25 was mistakenly misnamed by the analytical laboratory and was reported as MWANP-15. Analytical tables represent data correctly as MWANP-25.

· During the Spring event, sample vials for the analysis of ethane, ethene and methane for analysis by RSK175 for OS72-MW1 were misplaced by the analytical laboratory were not analyzed.

· OU8-MW-99 is included as a well to be sampled as part of fence line monitoring, however OU8-MW-99 is indicated as an annually monitored well and therefore was not samples during Fall 2017.

Figure 21: OU 8 Spring and Fall 2017 Sampling Locations

Figure 22: UWBU Spring 2017 Groundwater Contour Map

Figure 2-3: OU 8 Fall 2017 Groundwater Contour Map

Figure 2-4: OU 8 Vapor Monitoring Points

Table 21: OU 8 Groundwater Sampling and Analysis Plan

Table 2-1 page 2

Table 22: OU 8 Monitoring Well Construction Details & Groundwater Elevation Data

Table 2-2 page 2

Table 23: OU 8 Spring 2017 UWBU VOCs Data

Table 2-3 page 2

Table 2-3 page 3

Table 24: OU 8 Spring 2017 LWBU VOCs Data

Table 25: OU 8 Fall 2017 UWBU VOCs Data

Table 2-5 page 2

Table 2-5 page 3

Table 26: OU 8 Fall 2017 LWBU VOCs Data

Table 27: OU 8 Spring 2017 UWBU Field and ISB Performance Monitoring Parameters Data

Table 2-7 page 2

Table 2-7 page 3

Table 2-7 page 4

Table 2-7 page 5

Table 2-7 page 6

Table 2-7 page 7

Table 2-7 page 8

Table 28: OU 8 Spring 2017 LWBU Field and ISB Performance Monitoring Parameters Data

Table 29: OU 8 Fall 2017 UWBU Field and ISB Performance Monitoring Parameters Data

Table 2-9 page 2

Table 2-9 page 3

Table 2-9 page 4

Table 2-9 page 5

Table 2-9 page 6

Table 2-9 page 7

Table 210: OU 8 Fall 2017 LWBU Field and ISB Performance Monitoring Parameters Data

Table 211: OU 8 Spring 2017 UWBU SVOCs Data

Table 212: OU 8 Spring 2017 UWBU PCBs Data

Table 213: OU 8 Spring 2017 UWBU Metals Data

Table 214: OU 8 Fall 2017 UWBU SVOCs Data

Table 215: OU 8 Fall 2017 UWBU PCBs Data

Table 216: OU 8 Fall 2017 UWBU Metals Data

Table 217: OU 8 Fence Line Vapor Monitoring Data

RESULTS AND DISCUSSION

The following sections present the results of the groundwater and soil vapor monitoring activities conducted during semi-annual monitoring in 2017 as detailed in chapter 2 of this report.

Semi-Annual Groundwater Monitoring Results Potentiometric Surface Evaluations The depth to groundwater measurements and other well construction information including total well depths, screen intervals and well diameters for each well included in the OU 8 semi-annual groundwater monitoring program are presented in Table 2-2. Potentiometric surface maps are provided for the two 2017 semi-annual groundwater monitoring events at OU 8; however, they may not be accurate due to discrepancy and suspected accuracy issues in TOC elevations as previously discussed. The regional groundwater flow direction at OU 8 is historically toward the north-northeast, consistent with the historical migration of VOC plumes.

Laboratory Data Validation Data validation of the fixed laboratory analytical data was performed using Level III criteria, which comprises an evaluation of quality control (QC) summary results. All data validation was performed in accordance with the Draft Quality Assurance Project Plan (QAPP), the United States (US) Department of Defense (DoD) Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.0 (July 2013), a modified outline of the USEPA Contract Laboratory Program National Functional Guidelines (CLPNFG) for Superfund Organic Methods Data Review (June 2008) and the USEPA CLPNFG for Inorganic Superfund Data Review (January 2010). Where specific guidance was not available, the data was evaluated in a conservative manner consistent with industry standards using professional experience.

All data validation reports are included in Appendix D. A qualification summary table is provided at the end of each report if data was qualified. Quality criteria reviewed during a Level III data validation of organic analysis includes holding times, initial and continued calibration, blanks, surrogate recoveries, matrix spike and matrix spike duplicate recovery, internal standard performance, field duplicate sample analysis relative percent differences (RPD), reporting limits, and overall assessment of the sample delivery group. Select monitoring wells (6 total) that were analyzed for inorganics had analytical data validated based upon the above-mentioned criteria as well as duplicate sample RPD, ICP interference, Method of Standard Additions (MSA) and serial dilution checks.

The QC criteria reviewed, other than those discussed in each report, were met for April and October 2016 groundwater analytical data and are considered acceptable. Sample results that were flagged with a J qualifier were determined to be estimated because they are detected at a concentration above the instrumentation limit of detection (LOD) but below the instrumentation limit of quantitation (LOQ).

The data validation indicates that the data (collected in April and October 2016) presented in this report meet the project data quality objectives (DQOs) and are sufficient to evaluate groundwater contaminant levels and natural attenuation processes at OU 8.

Data Quality Evaluation A data quality evaluation (DQE) of the laboratory analytical data was performed using Level III criteria in accordance with the installation QAPP (Arcadis 2016a). The evaluated data quality indicators (DQIs) for organic analysis included in a Level III DQE report including a quality control review of holding times, initial calibration, continued calibration, evaluation of blank samples, surrogate recovery, matrix spike and matrix spike duplicate recovery, laboratory control sample recovery, internal standard performance, field duplicate sample analysis relative percent difference (RPD), reporting limits, and overall assessment of data. Evaluated DQIs for inorganic analysis include all aforementioned elements, including a review of inductively coupled plasma (ICP) interface check, mass spectrophotometer analysis (MSA) and serial dilution checks. DQIs are expressed in terms of precision, accuracy, representativeness, comparability, sensitivity, and completeness. Selected results were rejected or qualified based on the data validation practices and procedures included in the QAPP. The data validation reports documenting qualified parameters are included as Appendix D, and the DQE summary is included as Appendix E. The DQE indicates that the data presented in this report meet the project data quality objectives and are sufficient to evaluate groundwater contaminant levels and natural attenuation processes at OU 8.

Contaminants of Concern Results The VOC analytical results are tabulated in Tables 2-3 through Table 2-6. A discussion of the current concentrations of detected compounds above respective MCLs is presented below.

UWBU: Historically, six VOCs have been detected in OU 8 (AECOM 2017a) and were again detected in OU 8 at concentrations exceeding USEPA MCLs in April 2017 and October 2017.

These VOCs included:

· PCE,

· TCE,

· cis-1,2 DCE,

· VC,

· 1,2-Dichloroethane (1,2-DCA), and

· Dichloromethane (DCM) or Methylene Chloride.

A statistical summary of the analytical data for the above six VOCs is provided below in Table 3.1.

Table 31: OU 8 VOC Data Statistical Summary

MCL

(ug/L)

(ug/L)

(ug/L) October Highest Concentration Location

Note: µg/L = micrograms per liter

Plume Maps showing the extent of each compound are provided in Figures 3-1 through Figure 3-7 for April event and Figure 3-8 through Figure 3-14 for October event.

The highest PCE concentrations are within the area immediately downgradient of Warehouse 65 underneath the canopy and will be contained by the current layout of the BDGR pilot test. There is an area of high PCE concentrations immediately downgradient of the BDGR pilot test (around monitoring wells OU 8-MW-117, OU 8-MW-118 and DP-6); and further downgradient migration of which will be limited by the BDGR pilot test. PCE concentrations are generally stable to decreasing in the area directly influenced by the BDGR pilot test during 2017 when compared between Spring and Fall concentrations except for a few monitoring wells where concentrations slightly increased.

Near the north lobe and the Installation boundary along Strathmore Road, the PCE concentrations are stable or decreasing in most of the monitoring wells when compared between Spring and Fall concentrations. Near the southern lobe, the PCE concentrations are also generally stable when compared between Spring and Fall events. These conditions indicate controlled plumes, potentially due to the long-term operation of the north and south lobe pilot pumping tests.

Similar conclusions can be drawn for the PCE degradation products – TCE and cis-1,2-DCE. The other VOCs – VC, 1,2-DCA and DCM, appear to be present within the area downgradient of the Warehouse 65, and are controlled by the BDGR pilot test.

LWBU: In April and October 2017, no VOCs were detected above their respective MCLs.

Geochemical Results Historical results show that the geochemical conditions are generally not favorable for natural attenuation in the OU 8 UWBUs. Spring and Fall 2017 groundwater sampling continued to show unfavorable conditions with an average pH of 4.9 and 4.8 SU, respectively, with the lowest pH value of 1.93 (MWANP-3) in April 2017, which inhibits biologic activity under natural conditions, and dissolved oxygen concentrations of 2.7 and 2.3 mg/L, respectively, suggests an aerobic aquifer. While some chlorinated VOCs have been shown to biodegrade under aerobic conditions (e.g. cis-1,2-DCE and VC), more chlorinated compounds, such as PCE, will not undergo biotransformation under aerobic conditions. Additionally, PCE and TCE daughter products, cis-1,2-DCE and VC, are absent from the plume, except for select areas where the in-situ biodegradation (ISB) remedy has been implemented.

The ISB remedy was implemented in four areas in OU 8 focused on the remediation of higher concentrations of chlorinated VOCs near Warehouse 65 and eliminating further migration of groundwater impacts. Currently, the only area that appears to have appropriate geochemical conditions to support reductive dechlorination is in the vicinity monitoring wells OU 8-MW-50, OU 8-MW-67, OU 8-MW-68, and OU 8-MW-72. The remaining three areas indicate methane is being generated through biologic activity, however dissolved oxygen is greater than 1 mg/L in the monitoring wells closest to the injection wells and no daughter products (cis-1,2-DCE and VC), ethene or ethane are being generated.

The injection area immediately downgradient of Warehouse 65 is the only ISB area exhibiting active and complete dechlorination. The one ISB area that has exhibited appropriate geochemical conditions has four monitoring wells (OU 8-MW-50, OU 8-MW-67, OU 8-MW-68, and OU 8-MW-72) that have methane and TOC concentrations indicating biologic activity. Three of these wells (OU 8-MW-67, OU 8-MW-68, and OU 8-MW-72) have concentrations of ethene which demonstrates complete reductive dechlorination is occurring. While the pH in all four wells is below ideal (pH less than 5 SU), the low concentrations of natural electron acceptors (dissolved oxygen, nitrate, and sulfate) indicates utilization rates that exceed recharge rates. The geochemical conditions observed in the UWBU during 2017 sampling events continue to support the conclusion that natural attenuation by biologic pathways is not occurring plume-wide. Additionally, concentrations of TOC are not significant and have decreased in these areas since 2016 indicating that TOC concentrations are not sufficient to maintain ongoing degradation.

There are no impacts present in the Lower WBU and therefore an evaluation of the geochemical conditions was not performed.

Additional Suspected Source Areas Assessment Results Groundwater samples were collected from select six UWBU wells…