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Moffett RAB: EPA Regional Groundwater and Vapor Intrusion Update

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Steve Williams
Steve Williams

The document summarizes updates from the EPA on the regional groundwater and vapor intrusion investigation at NAS Moffett Field. It includes maps of the TCE plume in different aquifers over time and details preliminary findings from recent sampling. Next steps outlined are further delineating hotspots, installing extraction wells, finalizing reports, installing monitoring wells, and conducting modeling to evaluate capture. The document also summarizes comments from stakeholders and a remedy review board on the groundwater feasibility study, calling for more integration of groundwater and vapor intrusion remedies and evaluation of remediation technologies.

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EPA Regional Groundwater and Vapor Intrusion Update NAS Moffett Field Restoration Advisory Board Meeting February 7, 2013
Moffett RAB: EPA Regional Groundwater and Vapor Intrusion Update
TCE Plume and Estimated Capture Zone – A/A1 Aquifer (0 - 45 feet below ground surface)
TCE Plume and Estimated Capture Zone - B1/A2 Zone (50 - 75 feet bgs)
TCE Plume Estimated Capture Zone – B2 Aquifer (75 - 110 feet bgs)
Hydraulic Containment Work Completed • Advanced cone-penetrometers to evaluate types of soil in specific areas • Collected grab groundwater samples from boreholes to select well locations to define plume margins and characterize B2 Aquifer • Sampled wells at toe of plume in A/A1 Aquifer Zone to evaluate plume stability
Areas of Investigation – A/A1 Aquifer Zone
Areas of Investigation – B1/A2 Aquifer Zone
Areas of Investigation B2 Aquifer Zone
Preliminary Findings • Plume margins confirmed in each area with the exception of residential area south of 101 • High trichloroethene (TCE) in shallow groundwater beyond estimated plume boundary in residential area south of 101 • Plume area characterized in B2 Aquifer • Soil is heterogeneous with discrete layers of contamination
TCE Groundwater Results Along Western Margins – North of Highway 101
Maximum TCE Groundwater Results Western Margins – South of Highway 101 (A/A1 Aquifer)
Maximum TCE Groundwater Results Western Margins – South of Highway 101 (B1/A2 Aquifer)
High Priority Areas for Indoor Air Sampling
Groundwater – Next Steps • Determine extent of hot spots with further step-outs in residential area south of 101 • Install extraction wells to clean up hotspot areas • Finalize report summarizing data • Install and sample monitoring wells near plume boundaries (western, eastern, toe of plume) • Continue monitoring existing wells at toe of plume • Review plume boundaries • Conduct modeling to evaluate capture in B2 Aquifer
Questions
Moffett RAB: EPA Regional Groundwater and Vapor Intrusion Update
Groundwater Update Sitewide Groundwater Supplemental Feasibility Study • Stakeholder Comments on Preliminary Draft (July 2012) • National Remedy Review Board Meeting (July 24, 2012) • National Remedy Review Board Comments (January 14, 2013)
Stakeholder and Remedy Review Board Comments • In situ redox technologies (comments related to safety, support, implementation, cost) • Integrate groundwater and vapor intrusion (VI) remedy; provide metric for VI risk reduction related to groundwater • Address role of vadose zone contamination
Stakeholder and Remedy Review Board Comments • Evaluate improvements to slurry walls • Better explain approach to using monitored natural attenuation (MNA) • Areas of cleanup should also focus on sensitive populations and future development
EPA Next Steps • Meetings with stakeholders to discuss concerns and path forward for the Site-wide groundwater remedy
Questions
EPA Contact Information Penny Reddy EPA Groundwater Project Manager 415.972.3108 Reddy.Penny@epa.gov Alana Lee EPA Vapor Intrusion Project Manager 415.972.3141 Lee.Alana@epa.gov For More Information www.epa.gov/region9/mew www.epa.gov/region9/moffettfield
Additional Slides
Remedy Review Board Comments on Groundwater Feasibility Study • Provide a metric for measuring vapor intrusion risk reduction related to accelerated groundwater cleanup • Assess potential presence of dense non-aqueous phase liquid • Compile results of all in-situ redox technologies and provide more details on how the technologies would be applied and when • Address the role of vadose zone contamination • Evaluate improvements to slurry walls • Better explain approach to using monitored natural attenuation as component of remedy
Community Advisory Board Comments • Support for Alternative 4 (in situ redox plus optimized system and monitored natural attenuation) • Groundwater feasibility study should be integrated with vapor intrusion remedy • Areas for cleanup should not just include those with high concentrations but all areas of sensitive populations and future development • Monitored natural attenuation should not be considered until more active treatment is completed and concentrations fall below 50 ppb • Deployment of Permeable Reactive Barriers reconsidered
Community Advisory Board Comments (Continued) • Model should be relied upon only for comparative analysis • Concerns with safety to building occupants using in situ technologies beneath buildings and end results if only partial treatment • FS needs more discussion on difficulties implementing in situ treatment technologies beneath buildings and associated disruptions to properties
Projected VOC Plume – A Aquifer (0 to 45 feet bgs) 1992 2009 2019
Projected VOC Plume – B1/A2 Aquifer (50 to 75 feet bgs) 1992 2009 2019
Projected VOC Plume- B2 Aquifer (75 to 110 feet bgs)

More Related Content

Moffett RAB: EPA Regional Groundwater and Vapor Intrusion Update

  • 1. EPA Regional Groundwater and Vapor Intrusion Update NAS Moffett Field Restoration Advisory Board Meeting February 7, 2013
  • 3. TCE Plume and Estimated Capture Zone – A/A1 Aquifer (0 - 45 feet below ground surface)
  • 4. TCE Plume and Estimated Capture Zone - B1/A2 Zone (50 - 75 feet bgs)
  • 5. TCE Plume Estimated Capture Zone – B2 Aquifer (75 - 110 feet bgs)
  • 6. Hydraulic Containment Work Completed • Advanced cone-penetrometers to evaluate types of soil in specific areas • Collected grab groundwater samples from boreholes to select well locations to define plume margins and characterize B2 Aquifer • Sampled wells at toe of plume in A/A1 Aquifer Zone to evaluate plume stability
  • 10. Preliminary Findings • Plume margins confirmed in each area with the exception of residential area south of 101 • High trichloroethene (TCE) in shallow groundwater beyond estimated plume boundary in residential area south of 101 • Plume area characterized in B2 Aquifer • Soil is heterogeneous with discrete layers of contamination
  • 11. TCE Groundwater Results Along Western Margins – North of Highway 101
  • 12. Maximum TCE Groundwater Results Western Margins – South of Highway 101 (A/A1 Aquifer)
  • 13. Maximum TCE Groundwater Results Western Margins – South of Highway 101 (B1/A2 Aquifer)
  • 14. High Priority Areas for Indoor Air Sampling
  • 15. Groundwater – Next Steps • Determine extent of hot spots with further step-outs in residential area south of 101 • Install extraction wells to clean up hotspot areas • Finalize report summarizing data • Install and sample monitoring wells near plume boundaries (western, eastern, toe of plume) • Continue monitoring existing wells at toe of plume • Review plume boundaries • Conduct modeling to evaluate capture in B2 Aquifer
  • 18. Groundwater Update Sitewide Groundwater Supplemental Feasibility Study • Stakeholder Comments on Preliminary Draft (July 2012) • National Remedy Review Board Meeting (July 24, 2012) • National Remedy Review Board Comments (January 14, 2013)
  • 19. Stakeholder and Remedy Review Board Comments • In situ redox technologies (comments related to safety, support, implementation, cost) • Integrate groundwater and vapor intrusion (VI) remedy; provide metric for VI risk reduction related to groundwater • Address role of vadose zone contamination
  • 20. Stakeholder and Remedy Review Board Comments • Evaluate improvements to slurry walls • Better explain approach to using monitored natural attenuation (MNA) • Areas of cleanup should also focus on sensitive populations and future development
  • 21. EPA Next Steps • Meetings with stakeholders to discuss concerns and path forward for the Site-wide groundwater remedy
  • 23. EPA Contact Information Penny Reddy EPA Groundwater Project Manager 415.972.3108 Reddy.Penny@epa.gov Alana Lee EPA Vapor Intrusion Project Manager 415.972.3141 Lee.Alana@epa.gov For More Information www.epa.gov/region9/mew www.epa.gov/region9/moffettfield
  • 25. Remedy Review Board Comments on Groundwater Feasibility Study • Provide a metric for measuring vapor intrusion risk reduction related to accelerated groundwater cleanup • Assess potential presence of dense non-aqueous phase liquid • Compile results of all in-situ redox technologies and provide more details on how the technologies would be applied and when • Address the role of vadose zone contamination • Evaluate improvements to slurry walls • Better explain approach to using monitored natural attenuation as component of remedy
  • 26. Community Advisory Board Comments • Support for Alternative 4 (in situ redox plus optimized system and monitored natural attenuation) • Groundwater feasibility study should be integrated with vapor intrusion remedy • Areas for cleanup should not just include those with high concentrations but all areas of sensitive populations and future development • Monitored natural attenuation should not be considered until more active treatment is completed and concentrations fall below 50 ppb • Deployment of Permeable Reactive Barriers reconsidered
  • 27. Community Advisory Board Comments (Continued) • Model should be relied upon only for comparative analysis • Concerns with safety to building occupants using in situ technologies beneath buildings and end results if only partial treatment • FS needs more discussion on difficulties implementing in situ treatment technologies beneath buildings and associated disruptions to properties
  • 28. Projected VOC Plume – A Aquifer (0 to 45 feet bgs) 1992 2009 2019
  • 29. Projected VOC Plume – B1/A2 Aquifer (50 to 75 feet bgs) 1992 2009 2019
  • 30. Projected VOC Plume- B2 Aquifer (75 to 110 feet bgs)