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Army Orion Park Housing Update to Moffett RAB

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Presentation to the on Former Orion Park Housing Area (OPHA) Supplemental Site Investigation (SSI) …

Presentation to the on Former Orion Park Housing Area (OPHA) Supplemental Site Investigation (SSI)
for Groundwater Project
Update
February 9, 2012

Published in: Education, Technology

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  • 1. Former Orion Park Housing Area (OPHA) Supplemental Site Investigation (SSI) for Groundwater Restoration Advisory Board Project Update February 9, 2012
  • 2. Supplemental Site Investigation (SSI) Topics• Background o Historical site use o Trichloroethene (TCE) plume in groundwater• SSI Investigation o Purpose o Investigation Methods o Results• Questions
  • 3. OPHA Site Location SF BAY OPHA
  • 4. OPHA Historical AerialStevens Creek
  • 5. Meandering Stream – Typical GeologyClaySilt and ClaySiltFine SandSandGravelSurface Water
  • 6. Historical Site Use Groundwater Flow
  • 7. TCE Plume in GroundwaterUpper A1 Aquifer Lower A2 Aquifer(≈ 0 to 25 feet bgs) (≈ 27 to 65 feet bgs) Note: General flow directions are based on measurements from August 2005. Source of TCE contours: Tetra Tech EC. 2007. Groundwater Monitoring Well Installation and Sampling Report for Orion Park Housing Area. September.
  • 8. Previous Investigations Investigation Title Year Investigator Report ConclusionsFederal Facilities 1989 EPA, Navy NAAgreementSoil and Groundwater 1999 NASA Detected TCE on-site at downgradientInvestigation boundaryGroundwater Investigation 2000 Navy Detected TCE on-site at upgradient and downgradient boundariesSite Characterization 2002 Navy No on-site sources identifiedOff-Site Investigation 2003 Army Detected TCE off-site upgradientOff-Site Investigation 2005 EPA Detected TCE off-site upgradientGroundwater Investigation 2007 Navy No on-site sources identifiedand Monitoring WellInstallationSeptic Tank and Drain Field 2009 Army Septic tank and drain field not a sourceInvestigation
  • 9. Supplemental Site Investigation (SSI)• Voluntary investigation by Army• Work Plan approved by EPA and Water Board• SSI Purpose o Investigate locations of concern (LOCs) previously identified with input from EPA and Water Board
  • 10. Investigation Overview• Verified Previous Groundwater Data (2010/2011) o Flow direction –Water Levels o TCE (and other VOCs) – Chemical analysis• Measured (2011) o Soil Lithology – cone penetrometer technology (CPT) o VOCs (≈ TCE) in soil and groundwater - membrane interface probe (MIP) o TCE in groundwater – direct push technology (DPT)
  • 11. Investigation Methods = electron capture detector (ECD) VOCs - Groundwater Soil lithology VOCs TCE CPT (cone MIP (membrane DPT (direct push penetrometer interface probe) technology) technology)
  • 12. CPT/MIP Investigation in Upper A1 Aquifer• 5 LOCs o 14 CPT/MIPs• Upgradient TCE plume preferential pathways o 6 CPT/MIPs
  • 13. CPT/MIP Investigation in Lower A2 Aquifer• 4 LOCs o 13 CPT/MIPs• Upgradient TCE plume preferential pathways o 5 CPT/MIPs
  • 14. Screening Criteria to Identify Potential On-Site Source Criterion Primary Characteristics: ECDmax in capillary fringe? If 1 of 2 = Yes ECDmax ≥ 7e+6 µV? Investigate Secondary Characteristics: Further ECDmax ≥ 4e+6 µV ECD decreasing with depth? If 2 of 3 = Yes ECD higher in fine-grain? • If YES → Investigate further • If NO → Not a Source
  • 15. Example - ECD Profile EvaluationCone Resistance Electron Capture and Soil Detector (ECD) Lithology (microvolts [µV]) x 106 Electrical Conductivity Example: Highest ECD in silty clay to clay (secondary) A1 Aquifer Aquitard A2 Aquifer
  • 16. CPT/MIP Investigation Results Confirmed LOC Further MIP ECD Profile LOC Connected with Investigation Results Upgradient Plume? Warranted?1, 2a, 4, 5a, < Screening criteria Confirmed No 5b, 5c 3 < Screening criteria Not Confirmed Yes2b/6b (A1 Upgradient ECDs Not Confirmed Yes Aquifer) > Screening criteria 6b (A2 < Screening criteria Not Confirmed Yes Aquifer)
  • 17. DPT Investigation in Upper A1 Aquifer• 8 groundwater grab samples o LOC 3 – 3 samples (from 2 locations) o LOCs 2b/6b – 5 samples
  • 18. DPT Investigation in Lower A2 Aquifer• 3 groundwater grab samples o LOC 6b – 3 samples
  • 19. 3-D Model - Lithology InputsLithology (2002 - 2011 CPT) Outputs A1/A2 Aquitard
  • 20. 3-D Model – TCE Plume and Groundwater Contours ECD responses (2011 MIP) Groundwater water levels Inputs Outputs
  • 21. 3-D TCE Plume Model (TCE ≈ ECD Lower Level - 5e+5µV) OSouth North North TCE Above A1/A2 Aquitard A1/A2 Aquitard TCE Below A1/A2 Aquitard Previous Boring SSI Boring
  • 22. 3-D TCE Plume Model (TCE ≈ ECD Mid Level - 7.5e+5µV)South O North TCE Above A1/A2 Aquitard A1/A2 Aquitard TCE Below A1/A2 Aquitard Previous Boring SSI Boring
  • 23. 3-D TCE Plume Model (TCE ≈ ECD Higher Level - 1e+6µV)South O North North TCE Above A1/A2 Aquitard A1/A2 Aquitard TCE Below A1/A2 Aquitard Previous Boring SSI Boring
  • 24. TCE Plumes• A1 Aquifer Plume (≈ 0 to 25 feet bgs)• A2 Aquifer Plume (≈ 27 to 65 feet bgs)
  • 25. DPT and 3-D Model Investigation Results LOC Method Results Screened out1, 2a, 4, 5a, 5b, during CPT/MIP No on-site source 5c Investigation DPT Confirmed localized area of low ECD 3 responses were caused by residual TCE in 3-D Model fine-grained soils 2b/6b (A1 DPT Confirmed connection with upgradient A1 Aquifer) 3-D Model plume DPT Confirmed connection with upgradient A26b (A2 Aquifer) 3-D Model plume
  • 26. Conclusions and Next Steps• Conclusions o No on-site sources o Historical migrating TCE plume extends from southern boundary o TCE held up in fine-grained soils• Next Steps o SSI Report will be available for review upon finalization
  • 27. OPHA Project Team Contacts• US Army Environmental Command – Amanda Michels – Amanda.R.Michels.civ@mail.mil• US Army Corps of Engineers – Celso Sabiniano – Celso.F.Sabiniano@usace.army.mil
  • 28. Questions