Middlefield-Ellis-Whisman (MEW) Superfund Study Area: EPA Update on Groundwater Feasibility Study to the Community Advisory Board March 31, 2011. Penny Reddy, EPA Region 9

1. Middlefield-Ellis-Whisman (MEW)
Superfund Study Area
EPA Update
Groundwater Feasibility Study
Presentation for Community Advisory Board
March 31, 2011
Penny Reddy, EPA Region 9

2. 2

3. MEW / NAS Moffett Field Site – Shallow TCE
Groundwater Plume
Fairchild
Intel
Raytheon
NEC/Renasas
SMI
Vishay/ SUMCO
NASA
Navy

4. Estimated Extent of Regional TCE Shallow Groundwater
Plume

5. Purpose of Site-wide Groundwater
Feasibility Study
• Evaluate alternative technologies to accelerate
groundwater cleanup
– Efficiency of system decreasing
– Minimize need for vapor mitigation by reducing
groundwater concentrations (Vapor Intrusion RAO).
• Feasibility Study Considerations:
– Community Criteria and Suggested Strategy
– Incorporating results of pilot tests

6. Scope of Groundwater
Cleanup
• Large disperse
commingled plume with
multiple source areas
• Range of concentrations
within plume
• FS strategy treatment of
source & high conc. areas;
move to passive remedy
• Cleanup timeframes key
component of FS

7. B1/A2 Aquifer B2 Aquifer

8. EPA Screening of Technologies
In Situ Treatment Technologies:
Enhanced Reductive Dechlorination (ERD), In Situ Chemical
Oxidation (ISCO), and Abiotic Dechlorination using Zero
Valent Iron (ZVI)
Extraction, Removal, Treatment and Disposal Technologies –
– Physical Treatment with Air Sparging
– Groundwater Extraction and Treatment
– Multiphase Extraction
– In Situ Thermal
– Removal by Excavation
Barriers – Permeable reactive barriers, phytoremediation
Monitored Natural Attenuation

9. In Situ Treatment Technologies
• Evaluating ERD (Intel/GTE study), In Situ Chemical Oxidation
(ISCO), and Abiotic Dechlorination using Zero valent iron
• Technologies rely on direct contact or create conditions to
degrade contaminants.
• Typically used for hot spot treatment/limited area.
• Challenging to distribute material into heterogeneous
subsurface. Multiple injections typically needed.
• Technologies piloted at the site with varying success.

10. Extraction, Removal, Treatment and
Disposal Technologies
Air Sparging
Air injected into saturated
zone at high pressure; strips
solvents, which are extracted.
In Situ Thermal
Uses electrodes or heaters
attached to power supplies to
heat subsurface and
volatilize VOCs; vapor
collection.
Multiphase Extraction
Uses a high vacuum system
to extract soil vapor and
groundwater simultaneously.

11. Barriers
Continuous
Permeable Reactive Barriers Wall
• Intercepts and treats
contaminants as groundwater
flows through reactive barrier
• Common reactive media ZVI;
• Construction – Depths
generally less than 100 feet
Funnel and
• Lifespan (15 to 25 years) Gate System
(need to add
photo)
• Issues – fouling/movement
around wall

12. Monitored Natural Attenuation
– Relies on natural processes to cleanup pollution in
soil and groundwater.
– Conditions monitored to ensure that contaminants are
degrading and not migrating.
– Criteria to demonstrate MNA:
• Plume stability
• Review of temporal trends in well
• Geochemical and biological parameters indicate conditions
supporting degradation
– Component of alternative

13. Technologies Retained
1. Groundwater Extraction and Treatment
2. In Situ Redox Technologies (including Enhanced
reductive dechlorination, In Situ Chemical Oxidation
and Zero Valent Iron Injections) to treat high conc.
areas
3. Permeable Reactive Barriers (PRB)
4. Monitored Natural Attenuation (as component of an
alternative)

14. Projected VOC Plume – A Aquifer (0 to
45 feet bgs)
1992 2009 2019

15. EPA Working Alternatives – Shallow A Aquifer
Alt. 1 (No Action)
Alt. 2A (P&T/Slurry Wall) -Existing Remedy
Alt. 2B (P&T/Slurry Wall) - Existing Remedy Optimized for mass removal
Alt. 3 (P&T/Slurry Wall) - Existing Remedy Optimized for mass removal, Monitored
Natural Attenuation (MNA) (when demonstrated)
Alt. 4
Facility Specific Source Areas – In Situ Redox (see criteria)*
Regional Plume
In Situ Redox – High Conc. Areas (>1,000 ppb)
P&T and MNA (when Demonstrated)
Alt. 5A
Facility Specific Source Areas – In Situ Redox (see criteria)*
Regional Plume
In Situ Redox – High Conc. Areas (>1,000 ppb)
Permeable Reactive Barriers (PRBs)1, P&T and MNA (when Demonstrated)
Alt. 5B – Will be evaluating P&T Barrier Wells in lieu of PRBs

16. Conceptual Layout
In Situ Redox in A Aquifer DRAFT FOR DISCUSSION ONLY
Alternative 4:
In Situ Redox (Facility Specific
Source Areas)
In Situ Redox (High
Concentration Areas)
P&T (Medium and Low
Concentration Areas)*
• In Situ Redox in high MNA (when demonstrated)
In Situ Redox
Treatment Area
concentrations areas (gridded or transect
injections)
>1,000 ppb (facility and
regional plume)
• Groundwater pump and
treat for remaining areas
of plume until MNA
demonstrated

17. Conceptual Layout DRAFT FOR DISCUSSION ONLY
with PRBs in A Aquifer
Alternative 5A:
In Situ Redox (Facility Specific
Source Areas)
PRBs (Range of Concentrations)
P&T (Low Concentration Areas)*
MNA (when demonstrated)
In Situ Redox
• PRBs downgradient of Treatment Area
(gridded or transect
injections)
high concentration areas PRB
to treat residual
contamination
• Modeling to determine
number of PRBs
• Type of PRBs to be
determined

18. EPA Working Alternatives – Deeper Aquifers
Alt. 1 (No Action)
Alt. 2A (P&T/Slurry Wall) -Existing Remedy
Alt. 2B (P&T/Slurry Wall) - Optimized for mass removal
Alt. 3 (P&T/Slurry Wall) - MNA (when demonstrated)
Alt. 4
Facility Specific Source Areas – In Situ Redox (see criteria)*
Regional Plume - P&T and MNA (when Demonstrated)
Alt. 5A
Facility Specific Source Areas – In Situ Redox (see criteria)*
Regional Plume -PRBs, P&T and MNA (when Demonstrated)
Alt. 5B
Facility Specific Source Areas – In Situ Redox (see criteria)*
Regional Plume -P&T Barrier Wells and MNA (when Demonstrated)

19. Projected VOC Plume – B2/A1 Aquifer
(50 to 75 feet bgs)
1992 2009 2019

20. Groundwater Feasibility Study Summary
• Focusing on high concentrations and source areas; moving to more
passive remedy.
• Evaluating reasonable timeframes to complete cleanup.
• Scale of cleanup challenging.
• Difficult to implement in situ technologies in developed areas.
• Geology & matrix diffusion effects limit ability to accelerate cleanup.
• Potential recontamination of areas treated within different portions of
the plume.

21. EPA Site-wide Groundwater Feasibility
Study - Tentative Schedule
• TBD – Agenda topics for next CAB Meeting
• Summer 2011 – Draft Feasibility Study Report for review
• Fall 2011 – Remedy Review Board
• Winter 2012 – Final Feasibility Study Report, Proposed Plan for
public review
• Spring 2012 – Public Meeting and Public Comment Period
• Fall 2012 – Groundwater ROD Amendment
**Community involvement activities throughout the process
Updates and Meetings with Moffett Field RAB, MEW Community Advisory
Board, City, Property Owners, Developers, Community Members

22. Discussion/Questions

23. Contact Information
For More Information
www.epa.gov/region9/mew
www.epa.gov/region9/moffettfield
Penny Reddy
Groundwater Project Manager
EPA Region 9 Superfund Division
415.972.3108
Reddy.Penny@epa.gov