Presentation to the Moffett Restoration Advisory Board May 12, 2011.

1. Middlefield-Ellis-Whisman (MEW)
Superfund Study Area
S f S
EPA Update:
Site-Wide Groundwater Feasibility Study
y y
NAS M ff tt Fi ld R t
Moffett Field Restoration Advisory
ti Ad i
Board
May 12, 2011

2. 2

3. Purpose of Site-wide Groundwater
Feasibility Study
Evaluate alternative technologies to
accelerate groundwater cleanup
Current groundwater extraction &
treatment system decreasing in
efficiency
Minimize the need for vapor mitigation
by d i
b reducing groundwater concentrations
d t t ti

4. Key Feasibility Study Inputs
Pilot tests
Community Criteria and Suggested
Strategy Paper

5. Community Criteria and Suggested
Strategy Paper
1) FS and Remedy Selection should focus on:
 Areas with high mass
 Areas that continue to act as sources
 A
Areas of th plume that encroach on residential
f the l th t h id ti l
neighborhoods, schools and other sensitive uses
 Reduce the need to long-term vapor intrusion mitigation
g p g
 Enable reasonable future reuse of property
2) Incorporate results from optimization evaluations
3) Consider specific technologies

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

7. EPA Screening of Technologies
In Situ Treatment Technologies:
In Situ Bioremediation, In Situ Chemical Oxidation (ISCO),
and Abiotic Dechlorination using Zero Valent Iron (ZVI)
Extraction, Removal, Treatment and Disposal Technologies –
, , p g
– Physical Treatment with Air Sparging
– Groundwater Extraction and Treatment
–M li h
Multiphase Extraction
E i
– In Situ Thermal
– Removal by Excavation
Barriers – Permeable reactive barriers, phytoremediation
Monitored Natural Attenuation

8. In Situ Treatment Technologies
• Evaluating In Situ Bioremediation, 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.

9. Extraction, Removal, Treatment and
Disposal Technologies
Air Sparging
Air injected into sat rated
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.

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

11. Monitored Natural Attenuation
– Relies on natural processes to cleanup pollution in
soil and groundwater.
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

12. Technologies Retained
1. Groundwater Extraction and Treatment
2. In Sit R d T h l i (i l di I Sit
2 I Situ Redox Technologies (including In Situ
Bioremediation, In Situ Chemical Oxidation and Zero
Valent Iron Injections) to treat high conc. areas
j ) g
3. Permeable Reactive Barriers (PRB)
4. Monitored Natural Attenuation (as component of an
alternative)
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13. Projected VOC Plume – A Aquifer (0 to
45 feet bgs)
1992 2009 2019

14. EPA Working Alternatives – Shallow A Aquifer
Alt. 1 No Action
Alt. Extraction & Treatment (Existing & Optimized)
2A/2B
Alt. 3 Extraction & Treatment (Optimized), Monitored Natural Attenuation [MNA]*
Alt. 4 In Situ Redox (High Conc. Areas > 1,000 ppb)
Optimized Extraction and Treatment (Remaining Areas), MNA*
Alt. 5A In Situ Redox (High Conc. Areas > 1,000 ppb)
( g , pp )
Permeable Reactive Barriers (PRB)(Treatment downgradient of high
concentrations areas)
Optimized Extraction and Treatment (Remaining Areas), MNA*
Alt. 5B Same as Alt. 5A except PRB would be replaced by barrier wells.
Notes: In Situ Redox = in situ bioremediation, in situ chemical oxidation, or zero
valent i
l t iron i j ti
injections
*MNA = MNA where demonstrated

15. Conceptual Layout
Optimized Pump and Treat
Nort Sout
h of h of
101 101

16. Conceptual Layout
In Situ Redox in A Aquifer
• In Situ Redox in high
concentrations areas
t ti
>1,000 ppb
• Optimized pump &
treat for remaining
areas of plume until
MNA demonstrated

17. Conceptual Layout
with PRBs in A Aquifer
• PRBs downgradient of
high
hi h concentration
t ti
areas to treat residual
contamination
• Modeling to determine
number of PRBs
• Type of PRBs to be
determined

18. Projected VOC Plume – B1/A2 Aquifer
(50 to 75 feet bgs)
1992 2009 2019

19. VOC Plume (B2 Aquifer 75 to 110 feet bgs)

20. EPA Work Alternatives – Deeper Aquifer
Alt. 1 No Action
Alt. Extraction & Treatment (Existing & Optimized)
2A/2B
Alt. 3 Extraction & Treatment (Optimized), Monitored Natural Attenuation [MNA]*
Alt. 4 Facility-Specific Source Areas
In Situ Redox (Source Areas)
Optimized Extraction and Treatment (Remaining Areas), MNA*
Regional Plume Areas
Optimized Extraction & Treatment, MNA*
Alt. 5A Same as Alt. 4 except PRBs would be included to treat residual
contamination from facility-specific source and Regional Plume Areas
y p g
Alt. 5B Same as Alt. 5A except PRBs would be replaced by barrier wells.
Notes: In Situ Redox = in situ bioremediation, in situ chemical oxidation, or zero
valent iron injections
*MNA = MNA where demonstrated

21. Conceptual Layout with
PRBs in A2/B1 Aquifer
• PRBs more difficult to DRAFT FOR
DISCUSSION ONLY
install t deeper depths
i t ll at d d th ALTERNATIVE 5A
CONCEPTUAL LAYOUT
B1/A2 Zone
PRBs Downgradient of
High Concentration Areas
• PRBs extended from Optimized Extraction and
Treatment in Remaining
Areas
A Aquifer in areas of Regional Plume PRB
NOTES:
elevated concentrations
l t d t ti 1) PRB reactive media
may consist of
zero-valent iron,
chelators, sorbents,
or microbes

22. Groundwater Feasibility Study Challenges
• Scale of cleanup.
• Difficult to implement in situ technologies in developed
areas.
• Geology & matrix diffusion effects limit ability to
accelerate cleanup
cleanup.
• Potential recontamination of areas treated within different
portions of the plume.
i f h l
• Focusing on what we can do.
g

23. EPA Site-wide Groundwater Feasibility
Study - Tentative Schedule
• Summer 2011 – Draft Feasibility Study Report for review
• F ll 2011 R
Fall 2011 – Remedy Review Board
d R i B d
• Winter 2012 – Final Feasibility Study Report, Proposed Plan for
public review
public review
• Spring 2012 – Public Meeting and Public Comment Period
• Fall 2012 – Groundwater ROD Amendment
**Community involvement activities throughout the process
Community Advisory Board Meetings – February 9, March 31
RAB Meetings – Regular Updates on Vapor Intrusion and Groundwater
Property Owner Meetings – February 15
Upcoming Meetings – Property Owners Meeting – May 24

24. Discussion/Questions

25. 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
Reddy Penny@epa gov

26. 26

27. EPA Working Alternatives – Shallow A
Aquifer
Alt. 1 (No Action) Description of Alternative
Alt. 2A (P&T/Slurry Wall)
( y ) Existing Remedy
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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)*
(MNA)
Alt. 4 Facility Specific Source Areas
In Situ Redox (High Conc. Areas > 1,000 ppb)
In Situ Redox or Optimized P&T (Med. & Low Conc
(Med Conc.
Area), MNA*
Regional Plume
In Situ Redox – High Conc. Areas (>1,000 ppb)
Optimized P&T (Remaining Areas), MNA*
Notes: In Situ Redox = in situ bioremediation, in situ chemical
oxidation, or zero valent iron injections
*MNA = MNA where demonstrated

28. Regional Groundwater Progress Update
• Semi-annual water level measurements of nearly 1000
wells (Black Thursday)
• Annual sampling of approximately 500 wells
• Approximately 100 extraction wells pump over 450 gpm
• Over 4.5 billion gallons groundwater treated through
2009
• Over 95,000 pounds of VOCs removed through 2009

29. MEW / NAS Moffett Field Site Background
• ROD Signed in 1989 to address soil and groundwater
• Enforcement – Admin Order Consent Decree Federal
Order, Decree,
Facility Agreement
• Soil remedy (excavation and/or soil vapor extraction)
• Groundwater remedy - slurry walls, seal conduits, and
G d d l ll l d i d
pump and treat
• Hydrogeology – interbedded sands, silts, clays (Bay mud)
y g gy , , y ( y )
• Shallow groundwater – 5 to 20 feet bgs
• Current TCE in shallow groundwater
up to 40,000 ppb inside slurry walls
40 000
• Groundwater not used for potable use, but being cleaned
up to its beneficial use

30. VOC Plume (B2 Aquifer 75 to 110 feet bgs)

31. B1/A2 Aquifer B2 Aquifer

32. Conceptual Layout
with PRBs in A Aquifer
• PRBs downgradient of
high concentration areas
to treat residual
contamination
• Modeling to determine
number of PRBs
• Type of PRBs to be
determined

33. Draft Conceptual Layout
In Situ Redox in A2/B1Aquifer
• Focusing treatment on Facility-
Specific Source Areas and
High Concentration