W912DR18R0055_-_Attachment_AY_-_OMM_Plan_Bldg_151_SSDS_May_2018.docx

OPERATION, MAINTENANCE AND MONITORING PLAN

BUILDING 151 SUB-SLAB DEPRESSURIZATION SYSTEM

DEFENSE SUPPLY CENTER RICHMOND

Prepared For

Defense Logistics Agency and

Defense Supply Center Richmond

May 2018

OPERATION, MAINTENANCE AND MONITORING PLAN

BUILDING 151 SUB-SLAB DEPRESSURIZATION SYSTEM

DEFENSE SUPPLY CENTER RICHMOND

Prepared For:

Defense Supply Center Richmond

USACE – Baltimore District

Prepared By:

Arcadis U.S., Inc.

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

May 2018

OPERATION, MAINTENANCE AND MONITORING PLAN

Defense Supply Center Richmond Building 151 Sub-Slab Depressurization System

May 2018

Contents

TABLES

Table 1. Equipment List Table 2. OM&M Schedule Table 3. Alarm Details

Figures Figure 1. SSDS As-Built Layout Figure 2. Piping and Instrumentation Diagram Figure 3. Construction Details – Wall Penetration Figure 4. Construction Details – Break Room SSDS Point Figure 5. Construction Detail Figure 6. Construction Detail – SSDS Fan and Tool Room Window Penetration

APPENDICES

A System Equipment Manuals

Acronyms and Abbreviations

Introduction This Operation, Maintenance and Monitoring Plan (OM&M Plan) was prepared by Arcadis U.S., Inc. for Defense Logistics Agency (DLA) for the Building 151 SubSlab Depressurization System (SSDS) at the Defense Supply Center Richmond (DSCR), located in Richmond, Virginia (the “Site”). Building 151 is located within the portion of the installation occupied by the Virginia Army National Guard (VAARNG) and serves as their consolidated vehicle maintenance operations facility. The building consists of vehicle maintenance bays, sub-grade service pits, offices, a breakroom, tool room, and other facilities. It is occupied by mechanics and supervisors during business hours. Building 151 is located within the operable unit (OU) 6 area of concern, and samples of indoor air, sub slab vapor, and outdoor air are collected every 3rd and 5th year in accordance with the record of decision (ROD) for OU 6.

Currently, there is no complete vapor intrusion pathway. However, concentrations of volatile organic compounds (VOCs) are present in sub-slab soil vapor under a portion of Building 151 near sub-slab vapor monitoring points (VMP) VMP173 and VMP168 (monitoring point locations shown on Figure 1) which represent a potential for vapor intrusion to occur in the future should building conditions change. At these locations, sub-slab concentrations of trichloroethene (TCE) exceed United States (U.S.) Environmental Protection Agency (USEPA) Regional Screening Levels for sub-slab soil vapor calculated using the USEPA vapor intrusion screening level calculator for commercial space. TCE concentrations were detected by the U.S. Army Corps of Engineers (USACE) in 2015 in these VMPs at concentrations of 9,136 micrograms per meter cubed (µg/m3) and 101 µg/m3, respectively, which exceed the USEPA screening level of 100 µg/m3.

To address the presence or potential presence of VOCs beneath the building floor slab, vapor mitigation measures have been implemented via installation of an SSDS, with two vapor extraction points. One of the vapor extraction points is located in the tool room and the other is located inside the break room. Figure 1 shows the configuration of the SSDS in Building 151, including the extraction points, VMPs, and the observed extent of the SSDS-induced sub-slab vacuum after completion of installation.

System Objectives The overall objective of the SSDS is to mitigate the potential for workers within Building 151 to be exposed to vapors originating from the OU 6 groundwater plume via vapor intrusion. The specific performance objectives of the SSDS include:

· Induce a negative pressure field beneath the slab of the building near VMP168 and VMP173. The area requiring mitigation is defined by the area encompassing these monitoring points, as shown on Figure 1.

· Provide adequate vacuum to effectively mitigate the potential for vapor intrusion. Guidance documents from the New Jersey Department of Environmental Program (NJDEP 2018) indicate that a pressure differential of -0.004 to -0.005 inches of water column (in w.c.) is sufficient to mitigate the vapor intrusion pathway. The Virginia Department of Environmental Quality (VADEQ) does not provide specific guidance on acceptable differential pressure for building mitigation. A conservative vacuum of 0.010 in w.c. was used as the design objective in the area requiring mitigation, though vacuum influence of 0.004 in w.c. is considered to have adequate protection from subsurface vapor intrusion based on the USEPA Guidance.

System Overview The Building 151 SSDS consists of two subslab depressurization extraction points (Extraction points 1 and 2), located in the tool room and the break room, respectively, as shown on Figure 1. Pipe from these extraction points runs to a radon mitigation-style fan on the exterior wall of the building, outside the tool room. The extracted sub-slab vapor is then discharged to the atmosphere outside of the building, 18 inches above the roof line of the tool room and away from other vents or windows on the building. A drain pipe is installed at the low point of the system piping, where the system pipe exits the building in the tool room, to prevent condensate from building up in the system and obstructing the air flow. Each vacuum point has a gauge to measure the applied vacuum, a low vacuum indicator light, a gate valve, and a sample port to collect samples of extracted sub-slab vapor. Vacuum monitoring points, located across the area requiring mitigation, enable monitoring of the sub-slab differential pressure extension to ensure performance objectives are achieved.

SSDS Components This section describes SSDS components and specifications, including equipment designations for each system component. An equipment list is provided in Table 1. The layout of the SSDS including the locations of extraction points, major system components, and the area of vacuum influence is provided on Figure 1. As-Built drawings of the SSDS components are shown on Figures 2 through 6. Manufacturer’s manuals for system equipment are included in Appendix A.

SSDS Extraction Points To facilitate the installation of extraction sumps directly beneath the existing slab, a 1-foot diameter opening was created in the existing concrete floor slab at each extraction point. Sub-slab material was removed to create an extraction sump with a volume of approximately 1 cubic foot. The extraction sump was then filled with clean pea gravel. An open-ended 4-inch diameter schedule 40 carbon steel pipe was installed vertically into the upper 2 inches of the extraction sump pea gravel. A 6-mil polyethylene vapor barrier was placed on top of the washed stone, and new concrete was poured to repair the opening.

The vertical riser pipes for the extraction points were constructed of 4-inch diameter schedule 40 carbon steel pipe and include a vacuum gauge and a vapor sample port. The 4-inch schedule 40 carbon steel riser pipe then transitions to 4-inch schedule 40 polyvinyl chloride (PVC) pipe approximately 6-feet above grade. Extracted soil vapors are conveyed via the 4-inch diameter solvent-welded schedule 40 PVC pipe from the extraction point to the SSDS exhaust fan and discharge stack. Conveyance piping is sloped back toward the extraction points, where possible, to drain condensate from the system piping to below the concrete slab at the extraction points. Where the system pipe exits the main building and in the tool room, the piping is sloped towards the low spot at the tool room window penetration, where a ½ inch condensate drain line is connected to the system pipe, to allow condensate to drain from the system pipes back to below the concrete slab. There is also a cleanout cap at this low spot to allow any accumulating water to be manually cleared, if necessary.

Differential Pressure Gauges The vacuum indicators are Dwyer Instruments Magnehelic model 2310 differential pressure gauges with a range of 0-5 in w.c. These gauges, located on the risers at extraction points 1 and 2, indicate the vacuum applied to the sub-slab soil vapor extraction points. One differential pressure gauge is also installed at the system exhaust fan to measure the applied vacuum at the inlet to the SSDS exhaust fan.

System Exhaust Fan A RadonAway HS5000 radon exhaust fan capable of operating at a flow rate of 29 standard cubic feet per minute at an inlet vacuum of 20 in w.c. with a maximum pressure rating of 35 in w.c., is used to apply vacuum at the extraction points. The fan is located on the exterior wall of Building 151, just outside of the tool room. The fan discharges approximately 18 inches above the building’s roofline and includes a friction loss free rain hat to prevent intrusion of precipitation into the system.

Controls and Alarms One RadonAway Checkpoint IIa P/N 28001-2 system alarm is installed at each vacuum extraction point. The Checkpoint IIa alarms are plugged into electrical outlets on separate circuits from the fan and are set to alarm when the system vacuum falls below 0.25 in w.c. An illuminated green light on the alarm unit casing indicates the system pressure is above 0.25 in w.c. If the vacuum pressure falls below 0.25 in w.c., the green light will turn off, a red light will illuminate, and an audible alarm will sound. If the warning alarm sounds, the building workers may be directed to disconnect power from the alarm to silence it and alert an appropriate representative from DLA. Note that the alarm is present to alert the building occupants that service is required, it does not indicate a hazardous condition since there is not currently a complete vapor intrusion pathway.

Maintenance and Monitoring This section describes basic system OM&M requirements. The recommended schedule for OM&M tasks is shown in Table 2. The most current approved version of Table 2 should always be consulted in advance of quarterly OM&M events so that new requirements may be incorporated into the plan promptly.

The OM&M Performance Monitoring Log included in Appendix B should be completed on a quarterly basis and records maintained.

System Performance Monitoring On-site system monitoring will be conducted to verify that the system is operating properly. The Performance Monitoring Log included in Appendix B is to be completed at the frequency indicated in Table 2. The System Monitoring Log will be used to summarize the visual observations and data collection necessary to monitor system performance. System monitoring will include, but is not limited to, the following:

· General site inspection to ensure the system is running properly;

· Inspection of piping and fittings to ensure no damage;

· Record applied vacuum at extraction points; and

· Record sub-slab differential pressure at sub-slab monitoring points.

Sub-Slab Differential Pressure Monitoring Sub-slab differential pressures will be measured at VMPs at the frequency indicated in Table 2 and recorded in the Performance Monitoring Log (Appendix B). A micromanometer capable of measuring to the nearest 0.001 in w.c. will be used to measure instantaneous differential pressure at the VMPs with the system operating.

The micromanometer will be zeroed before each VMP measurement with both ports vented to the atmosphere. Micromanometers owned by system operators will be factory-calibrated annually or anytime the unit is dropped or otherwise suspected to be reading inaccurately. To measure sub-slab differential pressures, the threaded cap on the VMPs will be removed and a threaded compression fitting and tubing installed. With the other end of the tubing connected to the positive port on the micromanometer, negative readings measured by the micromanometer indicate a vacuum at the VMP. As discussed above, vacuum readings of 0.004 in w.c. or greater (i.e., pressure of less than -0.004 in w.c.), indicates that adequate vacuum extends to that VMP.

System Vapor Sampling Since Building 151 is located within the OU 6 area of concern, samples of indoor air, sub slab vapor and outdoor air are to be collected every 3rd and 5th year, in accordance with the ROD for OU 6.

Routine Maintenance General routine maintenance items are discussed below. Building 151 personnel will be notified at least 24 hours in advance of any maintenance requiring a system shutdown. Any work requiring lockout/tagout of equipment, or work on energized equipment, will be done in accordance with DLA and USACE requirements and in accordance with proper lockout/tagout requirements as specified in the health and safety plan (HASP).

System Exhaust Fan

5.3.1.1 Routine Maintenance

The system exhaust fan should be inspected for abnormal sound, odor, or vibration on a quarterly basis.

5.3.1.2 Non-Routine Maintenance

If the fan is not operating at normal fan inlet vacuum conditions and fan damage is suspected, complete fan voltage, current check, and dielectric testing to confirm that it is functioning per manufacturer’s performance specification (included in Appendix A). The blower motor voltage and current draw and dielectric testing should be checked by a competent person in accordance with DLA and USACE contractor safety program regarding work on energized equipment. The competent person must also have National Fire Protection Act (NFPA) 70E Arc Flash prevention training.

System Piping

5.3.2.1 Routine Maintenance

Inspect all system piping for signs of damage, leaks, blockages, and lack of structural integrity due to missing or damaged pipe supports. Check the condensate drain line, located in the tool room where the system pipe goes through the exterior wall, to ensure no blockage is present and that condensate is free to drain from the system piping.

5.3.2.1 Non-Routine Maintenance

Upon discovery, isolate damaged or leaking piping within the building from the sub-slab to eliminate leakage into the building. Repair any piping damage that is identified immediately or as soon as possible. If the condensate drain line or valve is clogged, remove clog to allow condensate to drain from the system piping.

System Monitoring Devices Alarm details for the monitoring devices are summarized in Table 3. Manufacturer quick start guides and manuals (Appendix A) may be utilized to perform testing of system monitoring devices. Each monitoring device will be tested at the frequency indicated in Table 2 to confirm the device is functioning, accuracy of readings, and alarm response.

Alarm Notification Procedure The system’s alarm notification procedure should be tested at the frequency indicated in Table 2. The system shutdown will be coordinated in advance with DLA, USACE, VAARNG/Building 151 personnel, and any other appropriate parties, so that an unnecessary alarm response is not initiated.

System Operation This section covers the general procedures to be followed when starting the system, performing a system shutdown, and responding to alarm conditions.

Starting the System The following steps should be taken to properly start the system under normal conditions:

1. Communicate with DLA/USACE to confirm that a system startup should be initiated. Follow the site protocol in the event that the fans are locked or tagged out.

2. Conduct a visual inspection of the system to ensure there are no obvious problems with any of the system process piping or electrical components.

3. To start the system, turn the breaker switch located by the window in the tool room to ‘On’. The exhaust fan should turn on.

4. Once sufficient vacuum has built up in the system piping, plug in and turn on the low vacuum alarm sensors at the extraction points. The green indicator lights on the pressure alarms should illuminate.

5. If the red alarm indicator lights remain illuminated and/or the exhaust fan does not turn on, the appropriate DLA/USACE representative should be notified.

6. Complete the Performance Monitoring Log.

Shutting the System Down The following steps should be taken to initiate a system shutdown:

1. Turn off the low vacuum alarm sensors on each SSDS vacuum point by unplugging them.

2. Turn the SSDS offline by switching the exhaust fan switch in the breaker box to the “Off” position.

3. Conduct lockout/tagout in accordance with the USACE health and safety requirements and the HASP.

Responding to Alarms The following steps should be taken to respond to an alarm condition. Any work on live electrical circuits should only be performed by personnel deemed to be qualified by the facility manager and in accordance with NFPA 70E health and safety requirements.

1. Record the status of the exhaust fan and note which alarm indicator light is illuminated using an Alarm Response Log (Appendix B) to document any alarm response activities.

2. Conduct a visual inspection of the system for problems with any of the system equipment, process piping or electrical components.

3. Check to see if condensation is present in the process piping low spots and drain if necessary.

4. Confirm all alarm conditions have been corrected.

5. Check the breaker switch in the breaker box located in the tool room to see if it is tripped and reset as necessary.

6. If the exhaust fan does not start, investigate the potential causes listed in the manufacturer’s manual included in Appendix A. Utilize a licensed electrician or qualified person for further diagnosis of the exhaust fan malfunction as necessary. A replacement fan should be procured and installed in accordance with manufacturer’s recommendations.

7. If the alarm condition cannot be corrected, consult the appropriate DLA/USACE representative.

Reporting A summary of the OM&M field monitoring will be provided for USACE and DLA following each visit on the routine progress calls.

Annual Reports will be provided to USACE and DLA which will include results of monitoring data, interpolation of the extent of vacuum influence, a summary of system performance, system down time, any maintenance performed, and any recommendations related to continued system monitoring. Building 151 vapor monitoring will be conducted in accordance with the ROD as discussed above.

References NJDEP, 2018. Vapor Intrusion Technical Guidance. Site Remediation and Waste Management Program. January.

image1.jpeg image2.png