Former Orion Park Housing Area            (OPHA) Supplemental Site Investigation              (SSI)       for Groundwater ...
Supplemental Site Investigation           (SSI) Topics• Background   o Historical site use   o Trichloroethene (TCE) plume...
OPHA Site Location            SF BAY OPHA
OPHA Historical AerialStevens Creek
Meandering Stream –     Typical GeologyClaySilt and ClaySiltFine SandSandGravelSurface Water
Historical Site Use                Groundwater Flow
TCE Plume in GroundwaterUpper A1 Aquifer                                          Lower A2 Aquifer(≈ 0 to 25 feet bgs)    ...
Previous Investigations   Investigation Title        Year Investigator            Report ConclusionsFederal Facilities    ...
Supplemental Site Investigation             (SSI)• Voluntary investigation by Army• Work Plan approved by EPA and Water Bo...
Investigation Overview• Verified Previous Groundwater Data (2010/2011)  o   Flow direction –Water Levels  o   TCE (and oth...
Investigation Methods                                 = electron                                   capture                ...
CPT/MIP Investigation          in Upper A1 Aquifer• 5 LOCs  o 14 CPT/MIPs• Upgradient TCE plume  preferential pathways  o ...
CPT/MIP Investigation          in Lower A2 Aquifer• 4 LOCs  o 13 CPT/MIPs• Upgradient TCE plume  preferential pathways  o ...
Screening Criteria to Identify  Potential On-Site Source   Criterion   Primary Characteristics:     ECDmax in capillary fr...
Example - ECD Profile EvaluationCone Resistance     Electron Capture   and Soil          Detector (ECD)   Lithology      (...
CPT/MIP Investigation Results                                        Confirmed LOC         Further                MIP ECD ...
DPT Investigation            in Upper A1 Aquifer• 8 groundwater grab  samples  o LOC 3 – 3 samples (from 2    locations)  ...
DPT Investigation            in Lower A2 Aquifer• 3 groundwater grab  samples  o LOC 6b – 3 samples
3-D Model - Lithology                              InputsLithology (2002 - 2011 CPT)                                      ...
3-D Model – TCE Plume and  Groundwater Contours   ECD responses (2011 MIP)    Groundwater water levels                    ...
3-D TCE Plume Model        (TCE ≈ ECD Lower Level - 5e+5µV)                                                   OSouth      ...
3-D TCE Plume Model    (TCE ≈ ECD Mid Level - 7.5e+5µV)South                                               O              ...
3-D TCE Plume Model    (TCE ≈ ECD Higher Level - 1e+6µV)South                                                O            ...
TCE Plumes• A1 Aquifer Plume (≈ 0 to 25  feet bgs)• A2 Aquifer Plume (≈ 27 to 65  feet bgs)
DPT and 3-D Model                    Investigation Results     LOC               Method                        Results    ...
Conclusions and Next Steps• Conclusions  o No on-site sources  o Historical migrating TCE plume extends from southern boun...
OPHA Project Team Contacts• US Army Environmental Command – Amanda  Michels – Amanda.R.Michels.civ@mail.mil• US Army Corps...
Questions
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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)
for Groundwater Project
Update
February 9, 2012

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Army Orion Park Housing Update to Moffett RAB

  1. 1. Former Orion Park Housing Area (OPHA) Supplemental Site Investigation (SSI) for Groundwater Restoration Advisory Board Project Update February 9, 2012
  2. 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. 3. OPHA Site Location SF BAY OPHA
  4. 4. OPHA Historical AerialStevens Creek
  5. 5. Meandering Stream – Typical GeologyClaySilt and ClaySiltFine SandSandGravelSurface Water
  6. 6. Historical Site Use Groundwater Flow
  7. 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. 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. 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. 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. 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. 12. CPT/MIP Investigation in Upper A1 Aquifer• 5 LOCs o 14 CPT/MIPs• Upgradient TCE plume preferential pathways o 6 CPT/MIPs
  13. 13. CPT/MIP Investigation in Lower A2 Aquifer• 4 LOCs o 13 CPT/MIPs• Upgradient TCE plume preferential pathways o 5 CPT/MIPs
  14. 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. 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. 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. 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. 18. DPT Investigation in Lower A2 Aquifer• 3 groundwater grab samples o LOC 6b – 3 samples
  19. 19. 3-D Model - Lithology InputsLithology (2002 - 2011 CPT) Outputs A1/A2 Aquitard
  20. 20. 3-D Model – TCE Plume and Groundwater Contours ECD responses (2011 MIP) Groundwater water levels Inputs Outputs
  21. 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. 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. 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. 24. TCE Plumes• A1 Aquifer Plume (≈ 0 to 25 feet bgs)• A2 Aquifer Plume (≈ 27 to 65 feet bgs)
  25. 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. 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. 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. 28. Questions

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