Moffett RAB: Navy Vapor Intrusion Update


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Presentation to the Moffett Restoration Advisory Board on February 13, 2014 by Scott Anderson of the Navy

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Moffett RAB: Navy Vapor Intrusion Update

  1. 1. ACTIVITY NAME Vapor Intrusion Update Former Naval Air Station Moffett Field Restoration Advisory Board Meeting February 13, 2014
  2. 2. Update Topics • Background • Past activities – – – – May-June 2012 Indoor Air Sampling Building 10 Utility Corridor Interim Action May 2013 Vapor Pathway Investigation May-June 2013 Soil Gas and Groundwater Investigation • Current sampling – February 2014 Indoor Air Sampling • Next steps 2 BRAC Program Management Office.
  3. 3. Site Background Navy (yellow), NASA (blue) and MEW Areas of Responsibility (green) 3 BRAC Program Management Office.
  4. 4. Indoor Air Cleanup Levels Chemical of Concern Indoor Air Cleanup Level (mg/m3) Trichloroethene (TCE) 5 Perchloroethylene (PCE) 2 cis-1,2-Dichloroethene 210 trans-1,2-Dichloroethene 210 Vinyl Chloride 2 1,1-Dichloroethane 6 1,1-Dichloroethene 700 Commercial ROD Amendment for the Vapor Intrusion Pathway (EPA, 2010) 4 BRAC Program Management Office.
  5. 5. May-June 2012 Sampling • Sampled indoor air in 23 commercial buildings to identify areas with COCs that exceed ROD cleanup levels • Visually inspected all buildings within the Navy area that are occupied or may be occupied – Nov 2011 and Apr 2012 • Interviewed building managers about building use, operations, work hours for occupants, etc. • Obtained information on heating, ventilation and air conditioning (HVAC) system operations and chemicals used in the buildings 5 BRAC Program Management Office.
  6. 6. Air Sampling Scope • Buildings with HVAC systems were sampled with HVAC on and off • HVAC-off samples were collected over Memorial Day weekend • Buildings without HVACs were sampled with windows and doors shut when possible • Sampled work areas and pathways (crawl spaces, utility conduits, elevator shafts, stairwells) • Collected 29 ambient air (outdoor/background) samples 6 BRAC Program Management Office.
  7. 7. Results for Air Sampling • Majority of buildings had detected VOCs above outdoor air levels but below action levels. • Only Buildings 10 and 126 had multiple samples that had VOCs above action levels. A groundwater investigation was conducted in 2012 and 2013 to investigate the VOC source near Building 126 (Site 28). • Buildings 3, 12, N210, and N239A (pathway locations) had samples from a single location that had a VOC exceeding project action levels. None of the samples collected from the work areas in these buildings exceeded the ROD action levels. 7 BRAC Program Management Office.
  8. 8. Building 10 • Chlorinated solvent vapors were detected in Building 10 above action levels in the Vapor Intrusion ROD Amendment. • The solvent vapors result from solvents that are dissolved in the shallow groundwater. The primary vapor intrusion pathway is through the utility corridor connected to Building 10. • A blower system has been installed in the utility corridor as an interim measure to reduce migration of vapors from the corridor into Building 10. 8 BRAC Program Management Office.
  9. 9. Building 10 Response Actions & Air Monitoring • Check work area air quality monthly using field measurement instruments and quarterly using air canisters. • Air monitoring results in February 2013 indicated TCE was still near ROD cleanup levels near the corridor entrance in Building 10 but below cleanup levels in the work area. Therefore, modifications were made to the system in May 2013: – Installed a barrier wall at the corridor entrance – Installed a second blower in the Building 10 floor trench that connects to the corridor. • Sampled Building 10 in June and November 2013 9 BRAC Program Management Office.
  10. 10. Building 10 Response Actions & Air Monitoring • Indoor air concentrations in the work areas were below action levels (TCE 0.89 to 1.1 mg/m3). • The blower system successfully reduced indoor air concentrations. • The blower system will remain in place as an interim measure until long-term plans are implemented. • The utility corridor is being evaluated to develop potential closure/sealing options. 10 BRAC Program Management Office.
  11. 11. Vapor Pathway Investigation • Follow-up indoor air sampling was conducted in May-June 2013 to evaluate floor conduit vapor pathways in Buildings 2, 3, and 12 and a TCE detection in Building N239A. • In Buildings 2, 3 and 12, floor utility conduits were sealed as an interim measure at pathway locations where elevated TCE was detected in May 2012 . Indoor air samples were collected at these locations before sealing and again 1 to 2 weeks after. • Sealing was effective for Building 2 which does not have an HVAC. • Sealing had limited effectiveness in Buildings 3 and 12, both of which have HVAC systems. Building 12 Room 110 11 BRAC Program Management Office. Building 3 Room 130
  12. 12. Vapor Pathway Investigation • In Building N239A, two utility rooms (intermittent work areas) were inspected for solvent sources and vapor pathways. • Floor conduits were found in the utility rooms. 12 BRAC Program Management Office.
  13. 13. Soil Gas and Groundwater Investigation June 2013: Collected 56 soil gas and 20 groundwater samples around the perimeter of buildings and along the Building 10 utility corridor to investigate shallow groundwater as a vapor source and potential vapor pathways in soil. 13 BRAC Program Management Office.
  14. 14. Soil Gas and Groundwater Investigation Soil Gas • Installed soil gas probes above the water table • Probes sampled after 48 hours • Samples were analyzed using a mobile lab. Groundwater • Installed temporary groundwater wells 2 feet into groundwater. • Samples were collected with a bailer and not filtered. 14 BRAC Program Management Office.
  15. 15. Soil Gas Results • TCE and related degradation products are primarily limited to the vicinities of Buildings 3, 10, 15, 16, 45, 76, 126, 555, 567 and the utility corridor from Building 10. • Isolated areas exist in the vicinities of Buildings 2, 14, N210 and 239A. (mg/m3) 15 BRAC Program Management Office.
  16. 16. Groundwater Results •PCE only detected above MCL at Building 126. •TCE above 500 mg/L near Buildings 10, 76, 126 and N210. •Other COCs are high near Buildings 10, 29, 76, 126 and N210. (mg/L) 16 BRAC Program Management Office.
  17. 17. February 2014 Air Sampling • A 2nd series of indoor and outdoor air samples will be collected during February 11 – 18, 2014. • This sampling will provide data on potential seasonal differences on the occurrence of vapor intrusion. • The winter data from February 2014 will be compared to the late-spring data from May-June 2012. • Indoor air samples will only be collected from the basement and 1st floor of the 23 buildings during the February 2014 sampling. • As in 2012, samples collected in February 2014 will be collected with both the HVAC on and off. 17 BRAC Program Management Office.
  18. 18. Vapor Intrusion Tier Response Evaluation •Data collected in 2012, 2013 and 2014 will be evaluated and used to rank the buildings according to the Vapor Intrusion ROD Amendment. •Response actions for each building will be developed. – Engineering controls, institutional controls, monitoring 18 BRAC Program Management Office.
  19. 19. Future Activities •The building tiering evaluation will be included in the February 2014 sampling results report. The draft report is scheduled for late June 2014. •Continue with CERCLA process for Remedial Design and Remedial Action 19 BRAC Program Management Office.
  20. 20. Air Sampling for Vapor Intrusion QUESTIONS ? 20 BRAC Program Management Office.