ACTIVITY NAME

Vapor Intrusion Update

Former Naval Air Station Moffett Field

Restoration Advisory Board Meeting

February 13, 2014

2 BRAC Program Management Office.

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 GroundwaterInvestigation

• Current sampling

– February 2014 Indoor Air Sampling

• Next steps

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Site Background

Navy (yellow), NASA (blue) and MEW Areas of Responsibility (green)

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Indoor Air Cleanup Levels

ROD Amendment for the Vapor Intrusion Pathway (EPA, 2010)

Chemical of Concern

Indoor Air CleanupLevel (mg/m3)

Commercial

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

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May-June 2012 Sampling

• Sampled indoor air in 23 commercial buildings to identifyareas with COCs that exceed ROD cleanup levels

• Visually inspected all buildings within the Navy area thatare occupied or may be occupied – Nov 2011 and Apr2012

• Interviewed building managers about building use,operations, work hours for occupants, etc.

• Obtained information on heating, ventilation and airconditioning (HVAC) system operations and chemicalsused in the buildings

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Air Sampling Scope

• Buildings with HVAC systems were sampled with HVAC on andoff

• HVAC-off samples were collected over Memorial Day weekend

• Buildings without HVACs were sampled with windows and doorsshut when possible

• Sampled work areas andpathways (crawl spaces,utility conduits, elevatorshafts, stairwells)

• Collected 29 ambient air(outdoor/background)samples

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Results for Air Sampling

• Majority of buildings had detected VOCs above outdoor airlevels but below action levels.

• Only Buildings 10 and 126 had multiple samples that hadVOCs above action levels. A groundwater investigation wasconducted in 2012 and 2013 to investigate the VOC sourcenear Building 126 (Site 28).

• Buildings 3, 12, N210, and N239A (pathway locations) hadsamples from a single location that had a VOC exceedingproject action levels. None of the samples collected from thework areas in these buildings exceeded the ROD action levels.

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Building 10

• Chlorinated solvent vapors were detected in Building 10 aboveaction levels in the Vapor Intrusion ROD Amendment.

• The solvent vapors result from solvents that are dissolved inthe shallow groundwater. The primary vapor intrusionpathway is through the utility corridor connected to Building10.

• A blower system has beeninstalled in the utilitycorridor as an interimmeasure to reducemigration of vapors from thecorridor into Building 10.

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Building 10 Response Actions & Air Monitoring

• Check work area air quality monthly using field measurementinstruments and quarterly using air canisters.

• Air monitoring results in February 2013 indicated TCE was stillnear ROD cleanup levels near the corridor entrance in Building 10but below cleanup levels in the work area. Therefore,modifications were made to the system in May 2013:

– Installed a barrier wall at thecorridor entrance

– Installed a second blower in theBuilding 10 floor trench thatconnects to the corridor.

• Sampled Building 10 in June andNovember 2013

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Building 10 Response Actions & Air Monitoring

• Indoor air concentrations in the work areas were below actionlevels (TCE 0.89 to 1.1 mg/m3).

• The blower system successfully reduced indoor airconcentrations.

• The blower system will remain in place as an interim measureuntil long-term plans are implemented.

• The utility corridor is being evaluated to develop potentialclosure/sealing options.

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Vapor Pathway Investigation

• Follow-up indoor air sampling was conducted in May-June 2013 toevaluate floor conduit vapor pathways in Buildings 2, 3, and 12 and aTCE detection in Building N239A.

• In Buildings 2, 3 and 12, floor utility conduitswere sealed as an interim measure at pathwaylocations where elevated TCE was detected inMay 2012 . Indoor air samples were collected atthese locations before sealing and again 1 to 2weeks after.

• Sealing was effective for Building 2 which doesnot have an HVAC.

• Sealing had limited effectiveness in Buildings 3and 12, both of which have HVAC systems.

Building 3Room 130

Building 12Room 110

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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 theutility rooms.

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Soil Gas and Groundwater Investigation

June 2013: Collected 56 soil gas and 20 groundwater samplesaround the perimeter of buildings and along the Building 10utility corridor to investigate shallow groundwater as a vaporsource and potential vapor pathways in soil.

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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 2feet into groundwater.

• Samples were collected with a bailer andnot filtered.

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Soil Gas Results

• TCE and related degradation products are primarily limited to thevicinities of Buildings 3, 10, 15, 16, 45, 76, 126, 555, 567 and the utilitycorridor from Building 10.

• Isolated areas exist in the vicinities of Buildings 2, 14, N210 and 239A.

(mg/m3)

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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)

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February 2014 Air Sampling

• A 2nd series of indoor and outdoor air samples will becollected during February 11 – 18, 2014.

• This sampling will provide data on potential seasonaldifferences on the occurrence of vapor intrusion.

• The winter data from February 2014 will be compared to thelate-spring data from May-June 2012.

• Indoor air samples will only be collected from the basementand 1st floor of the 23 buildings during the February 2014sampling.

• As in 2012, samples collected in February 2014 will becollected with both the HVAC on and off.

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Vapor Intrusion Tier Response Evaluation

•Data collected in 2012, 2013 and 2014 will be evaluatedand used to rank the buildings according to the VaporIntrusion ROD Amendment.

•Response actions for each building will be developed.– Engineering controls, institutional controls, monitoring

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Future Activities

•The building tiering evaluation will be included in theFebruary 2014 sampling results report. The draft report isscheduled for late June 2014.

•Continue with CERCLA process for Remedial Design andRemedial Action

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Air Sampling for Vapor Intrusion

QUESTIONS ?