W912DR18R0055_-_Attachment_BB_-Draft_OU8_SSDS_Report_2017_REV1_clean.docx

BUILDING 65 SUB-SLAB DEPRESSURIZATION SYSTEM

ANNUAL MONITORING REPORT

FOR OPERABLE UNIT 8,

DEFENSE SUPPLY CENTER RICHMOND

Prepared For

Defense Logistics Agency and

Defense Supply Center Richmond

July2018

BUILDING 65 SUB-SLAB DEPRESSURIZATION SYSTEM

ANNUAL MONITORING REPORT

FOR OPERABLE UNIT 8,

DEFENSE SUPPLY CENTER RICHMOND

Prepared For:

Defense Supply Center Richmond Defense Logistics Agency USACE – Baltimore District

Prepared By:

Arcadis HTRW Contract No. W912DR-13-D0019 Task Order 0005

July 2018

Table of Contents

List of Figures

List of Tables Table 1: Weekly SSDS Data Table 2: Monthly Vent Well and Vapor Monitoring Point Data Table 3: Quarterly System Sampling

Acronyms and Abbreviations

Building 65 Sub-Slab Depressurization System Annual Monitoring Report - 2017 Operable Unit 8, Defense Supply Center Richmond July 2018 ii

EXECUTIVE SUMMARY

This report summarizes monitoring activities at the Operable Unit (OU8) Building 65 sub-slab depressurization system (SSDS) from October 2016 through October 2017. Vacuum monitored at vapor monitoring points (VMP) and SSDS vent wells (VW), had shown a decreasing trend of both applied vacuum at VWs and induced vacuum at VMPs from October 2014 through March 2015. This decreasing trend was attributed to the inadequate size of the existing SSDS blower. On 31 March 2015, the existing 0.5 horsepower (HP) blower was disconnected and a larger 3 HP blower was connected to the SSDS. The larger 3 HP blower provides sufficient vacuum (1.3 inches of water column [WC] to 4.6 inches WC) at each VW. On 10 June 2015 and 26 June 2016, a radius of influence (ROI) effectiveness study was conducted on the Building 65 blower system. Several different operating configurations were tested. The configurations included varying the flow rate of the blower and operating different VWs while monitoring the vacuum response at each VMP. The results of the 2015 ROI effectiveness study were evaluated and recommended modifications to the SSDS system were completed between April 2016 and June 2016 including the installation of an additional VW and additional VMPs.

A second ROI investigation was completed in October 2016 to evaluate the effectiveness of the additional VW and VMPs that were installed between April 2016 and June 2016. As a result of the ROI investigation, additional modifications have been recommended and are currently under review.

Quarterly vapor system sampling was conducted on 21 November 2016, 07 March 2017, 01 June 2017, and 06 September 2017. Vapor grab samples were collected from three OU8 SSDS locations; 1) SSDS System Influent, 2) SSDS after primary granular activated carbon (GAC), and 3) SSDS stack effluent after secondary GAC. Vapor samples were sent to Eurofins Air Toxics, Inc. during the first three quarters and TestAmerica Laboratories, Inc. during the 4th Quarter for TO-15 analysis.

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INTRODUCTION AND SITE HISTORY

This document summarizes monitoring activities conducted on the Building 65 sub-slab depressurization system (SSDS) located within Operable Unit 8 (OU8) at the Defense Supply Center Richmond (DSCR), in Richmond, Virginia (site). The monitoring activities presented in this report were conducted between October 2016 to October 2017. Figure 1 shows the location of OU8 at DSCR. Figure 2 presents the current layout of the SSDS which is focused in the northern end of Building 65 in the areas referred to as “E Bay” and “F Bay”.

Building 65 is a large warehouse currently used by the Defense Logistics Agency (DLA) Distribution for storage, excluding hazardous materials. Workers in Building 65 generally use propane-fired or electrical vehicles as transportation throughout the building and to move materials to and from upper shelving storage locations (e.g., 30 feet above ground surface). Building 65 is divided into separate bay areas that are separated by bay doors that roll-up. The northern end of Building 65 (i.e., F Bay) is a separate room from the rest of the warehouse building, and was added to the original building approximately 10 years after the original construction date. The southern portion of F Bay / northern portion of E Bay (Figure 2) is the location of former acid dipping and metal cleaning tanks used to prepare World War II combat helmets, cylinders, and other metal parts for repainting. Spent acids were discharged to the Acid Neutralization Pits (ANP) located to the northwest of Building 65.

The use of solvents during metal cleaning operations is not documented; however, solvent residuals have been detected in soil vapor and groundwater along the northern wall of F Bay of Building 65, between monitoring well OU8-MW-51 and injection well OU8-INJ-62 and north toward monitoring wells OU8-MW-69 and OU8-MW-70. Relatively large exhaust fans, exhaust fan duct work, and roof vents that appear consistent with reported solvent cleaning operations are still present in the F Bay of Building 65. A chronology of activities related to SSDS operation that were conducted at the OU8 Building 65 area is presented in the table below.

Figure 1: Operable Unit 8 - Defense Supply Center Richmond

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OU8 BUILDING 65 SUBSLAB DEPRESSURIZATION SYSTEM DESCRIPTION

As outlined in the table above, the SSDS system has changed from its initial configuration to increase its functionality. As currently installed the OU8 SSDS include a 3 HP regenerative blower, moisture separator, and GAC drums connected to nine VWs by an aboveground piping network. Modifications to the SSDS were proposed in a Phase 2 report (AECOM 2015) and completed between 29 February 2016 and 3 March 2016. The modifications included the installation of a replacement vacuum monitoring point (VMP) (VMP191) at location VMP95, the installation of a new VMP in the southwestern portion of F Bay (VMP192), and the installation of VW along the southern wall of F Bay (VW193). VMP191 was installed immediately adjacent to VMP95 to evaluate the effectiveness of previous SSDS upgrades; VMP95 was not removed or abandoned. Vapors from the subsurface are now extracted from nine vapor extraction wells or VWs.

Ten VMPs have been used to show vacuum influence of the SSDS. Construction of the VMPs was completed using hydraulic cement and volatile organic compound (VOC)-Free Modeling Clay, and 1/4- inch stainless steel Swagelok fittings. The end of each VMP is believed to be approximately two inches below the floor slab. Two VMPs are located in E Bay, seven VMPs are in F bay, and three VMPs are in the exterior covered storage area.

VWs are constructed of 2-inch polyvinyl chloride (PVC) piping and well screen. Details for VW193 indicate a total depth of 12- inches bgs using 2- inch PVC well screen with a PVC cap, and PVC riser. Screen length is 5- inches with a filter sand pack and 10- inch riser pipe. The VW riser pipes are connected via a camlock fitting to a 2-inch flex hose. The flex hose is then connected to a 2-inch PVC header pipe that is plumbed to the SSDS system shed.

A process flow diagram of the SSDS is shown on Figure 2. Figure 3 provides a site layout depicting the locations of the nine VWs and ten VMPs.

Figure 2: SSDS Process Flow Diagram

Figure 3: Vent Well and Vapor Monitoring Point Locations

SUMMARY OF FIELD ACTIVITIES

The SSDS system is monitored weekly, the vacuum field is monitored monthly and quarterly when sampling for VOCs is conducted. Details of weekly and monthly monitoring activities are described below. Quarterly monitoring occurred on 21 November 2016, 07 March 2017, 01 June 2017, and 06 September 2017.

Weekly Monitoring Summary Weekly system checks on the SSDS system include measurements of flowrate, temperature and pressure. Weekly system checks from 10 October 2016 – 26 September 2017 indicated normal operations, with exceptions detailed as follows.

The SSDS blower tripped the high temperature alarm and turned off the system three times during the reporting period. There was an interruption of the system in April, July, and August 2017. A field inspection of the SSDS and VWs by Arcadis determined that upon system restart the valves for five of the VWs (VW77, VW78, VW79, VW81 and VW82) had been closed. These VWs were opened and the SSDS system dilution valve was subsequently opened 100% to increase air flow in the system and cool the blower. The fan in the system shed was also turned on and building vents were opened to promote a cross-breeze in the shed to cool the blower. To further the cooling process during hotter temperatures the SSDS building door was left opened and two additional fans were used to cool the blower. The SSDS remained running for the duration of the operating period after making these minor modifications. Weekly system data for 2017 are included in Table 1.

Monthly Monitoring Summary Monthly monitoring of all VMPs and VWs occurred in all months in 2017. The purpose of monthly monitoring is to evaluate sub-slab vapor conditions and monitor for the presence of methane and VOCs. Field instrument readings (VOC, methane, carbon dioxide, and oxygen) are collected at each VMP, VW, SSDS stack exhaust, and an ambient location indoors and an ambient air location outdoors. Methane, carbon dioxide, and oxygen readings are documented with a Lantec™ GEM 2000. Photoionization detection readings were recorded with a MiniRAE™ 3000. Field instruments were calibrated per the manufacturer’s specifications prior to each use. Monthly monitoring data for 2017 is presented in Table 2.

Quarterly System Sampling Quarterly sampling was conducted on 21 November 2016, 07 March 2017, 01 June 2017, and 06 September 2017. The purpose of quarterly sampling is to monitor the removal of VOCs from the sub-slab and determine if the carbon in the GAC units is spent. Vapor samples were collected from three locations including the SSDS influent, after the first GAC unit also known as the GAC1 location, and from the SSDS effluent using laboratory provided summa canisters and analyzed for VOCs using USEPA Method TO-15. An ambient air sample was also collected from the area surrounding the SSDS system using a laboratory provided summa canister and analyzed for VOCs using USEPA Method TO-15 during the first three quarters. Samples were submitted to Eurofins Air Toxics, Inc. in Folsom, California in quarters one (1Q17), two (2Q17), and three (3Q17) and TestAmerica Laboratories, Inc. in Knoxville, Tennessee for analysis in quarter four (4Q17). During the quarterly sampling events, vapor samples indicated concentrations of cis-1,2-dichloroethene in the influent in all four quarterly samples, in the GAC1 samples during 2Q17, 3Q17, and 4Q17, and in the effluent samples during all four quarterly samples. Concentrations of trichloroethene and tetrachloroethene were detected in the influent and GAC1 samples. All other analytes were not detected or below the detection limit.

A summary of the analytical data is presented in Table 3.

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Conclusions and recommendations The Building 65 SSDS continues to operate and provides vacuum coverage throughout most of F Bay, mitigating the potential for vapor intrusion into this space. The system is currently being operated as modified by Arcadis on 19 May 2017. During field optimization activities five VWs were opened, and the dilution valve was opened 100% to increase air flow and cool the blower. These modifications were made due to decreased air flow in the system. The blower has overheated a number of times, tripping the system to turn off. The dilution valve was subsequently opened to increase system air flow and provide sufficient cooling to the blower, however the system vacuum decreased significantly.

Arcadis will evaluate the system design objectives, current operational data and future needs at the site to ensure the vapor intrusion pathway remains appropriately mitigated. System modifications have been suggested and will be presented under separate cover.

The purpose of the SSDS is to mitigate the potential for worker exposure to vapors originating from under Building 65 by inducing a negative pressure field directly beneath the floor slab. Given the intended purpose of the SSDS, GAC units are not required for monitoring system effectiveness. However, the GACs will continue to be monitored for the purposes of determining if changeout is required while still in use.

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REFERENCES

AECOM. 2016a. Draft Technical Memorandum Building 65 Sub-Slab Depressurization System Effectiveness Study Phase 3, Operable Unit 8, September 2016, Defense Supply Center Richmond, Virginia. September.

AECOM. 2016b. Draft Building 65 Sub-Slab Depressurization System Quarterly Monitoring Report April – June 2015 for Operable Unit 8, Defense Supply Center Richmond, Virginia. July.

AECOM. 2015. Final Technical Memorandum Building 65 Sub-Slab Depressurization System Effectiveness Study, Operable Unit 8, December 2015 Defense Supply Center Richmond, Virginia. December.

Defense Supply Center Richmond. 2007. Final Record of Decision Operable Unit 8 Acid Neutralization Pits Groundwater Defense Supply Center Richmond, Virginia.

MACTEC, 2006a. Final Revised Focused Feasibility Study Operable Unit 8 Conceptual Site Model, Defense Supply Center Richmond, Richmond, Virginia Revision 1, April.

MACTEC, 2006b. Final Environmental Land Use Control Implementation Plan for Defense Supply Center Richmond, Richmond, Virginia Revision 1, April.

MACTEC, 2006c. Supplemental Feasibility Study Investigation Report, Defense Supply Center, Richmond, Richmond, Virginia Revision 1, February.

USEPA, 2002. Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils. Washington, D.C: Office of Solid Waste and Emergency Response. www.epa.gov/correctiveactioneisvaporcomplete.pdf

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