Middlefield-Ellis-Whisman (MEW) S f SSuperfund Study Area

EPA Update: Site-Wide Groundwater Feasibility Study y y

NAS M ff tt Fi ld R t ti Ad i NAS Moffett Field Restoration Advisory Board

May 12, 2011

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Purpose of Site-wide Groundwater Feasibility Study

Evaluate alternative technologies to accelerate groundwater cleanup

Current groundwater extraction & treatment system decreasing intreatment system decreasing in efficiency

Minimize the need for vapor mitigation b d i d t t tiby reducing groundwater concentrations

Key Feasibility Study Inputs

Pilot tests

Community Criteria and SuggestedCommunity Criteria and Suggested Strategy Paper

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 f th l th t h id ti l Areas of the plume that encroach on residential

neighborhoods, schools and other sensitive uses Reduce the need to long-term vapor intrusion mitigationg p g Enable reasonable future reuse of property

2) Incorporate results from optimization evaluations

3) Consider specific technologies3) Consider specific technologies

Scope of Groundwater Cleanup

• Large disperse commingled plume withcommingled plume with multiple source areas

• FS strategy treatment of source & high conc. Areas

• Range of concentrations within plumewithin plume

• Cleanup timeframes key component of FS

EPA Screening of TechnologiesIn Situ Treatment Technologies:

In Situ Bioremediation, In Situ Chemical Oxidation (ISCO), and Abiotic Dechlorination using Zero Valent Iron (ZVI)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 l i h E i– Multiphase Extraction– In Situ Thermal– Removal by ExcavationRemoval by Excavation

Barriers – Permeable reactive barriers, phytoremediationMonitored Natural Attenuation

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.

Extraction, Removal, Treatment and Disposal Technologies

Air SpargingAir injected into sat ratedAir injected into saturated zone at high pressure; strips solvents, which are extracted.

In Situ ThermalUses electrodes or heaters attached to power supplies toattached to power supplies to heat subsurface and volatilize VOCs; vapor collection.collection.

Multiphase Extraction Uses a high vacuum system to extract soil vapor and groundwater simultaneously.

Barriers

Permeable Reactive Barriers• Intercepts and treats

Continuous 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)

• Issues – fouling/movement

Gate System (need to add photo)

garound wall

Monitored Natural Attenuation

– Relies on natural processes to cleanup pollution in soil and groundwatersoil and groundwater.

– Conditions monitored to ensure that contaminants areConditions monitored to ensure that contaminants are degrading and not migrating.

– Criteria to demonstrate MNA:• Plume stability• Review of temporal trends in wellReview of temporal trends in well• Geochemical and biological parameters indicate conditions

supporting degradation

– Component of alternative

Technologies Retained

1. Groundwater Extraction and Treatment2 I Sit R d T h l i (i l di I Sit2. In Situ Redox Technologies (including In Situ

Bioremediation, In Situ Chemical Oxidation and Zero Valent Iron Injections) to treat high conc. areasj ) g

3. Permeable Reactive Barriers (PRB)4. Monitored Natural Attenuation (as component of an

lt ti )alternative)

Projected VOC Plume – A Aquifer (0 to 45 feet bgs)

1992 2009 2019

EPA Working Alternatives – Shallow A AquiferAlt. 1 No Action

Alt. 2A/2B

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 l t i i j tivalent iron injections

*MNA = MNA where demonstrated

Conceptual Layout Optimized Pump and Treat

SoutNorth of 101

h of 101

Conceptual Layout In Situ Redox in A Aquifer

• In Situ Redox in high t ticoncentrations areas

>1,000 ppb

• Optimized pump & treat for remainingtreat for remaining areas of plume until MNA demonstratedMNA demonstrated

Conceptual Layout with PRBs in A Aquifer

• PRBs downgradient of hi h t tihigh concentration areas to treat residual contaminationcontamination

• Modeling to determine• Modeling to determine number of PRBs

• Type of PRBs to be determineddetermined

Projected VOC Plume – B1/A2 Aquifer (50 to 75 feet bgs)

1992 2009 20191992 2009 2019

VOC Plume (B2 Aquifer 75 to 110 feet bgs)

EPA Work Alternatives – Deeper AquiferAlt. 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 AreasRegional Plume AreasOptimized 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 Areasy 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

Conceptual Layout with PRBs in A2/B1 Aquifer

• PRBs more difficult to i t ll t d d th

DRAFT FOR DISCUSSION ONLYinstall at deeper depthsPRBs Downgradient of High Concentration Areas

DISCUSSION ONLY

ALTERNATIVE 5A CONCEPTUAL LAYOUTB1/A2 Zone

• PRBs extended from A Aquifer in areas of

l t d t ti

Optimized Extraction and Treatment in Remaining Areas

NOTES:

Regional Plume PRB

elevated concentrations NOTES: 1) PRB reactive media

may consist of zero-valent iron, chelators, sorbents, or microbes

Groundwater Feasibility Study Challenges

• Scale of cleanup.

• Difficult to implement in situ technologies in developed areas.

• Geology & matrix diffusion effects limit ability to accelerate cleanupaccelerate cleanup.

• Potential recontamination of areas treated within different i f h lportions of the plume.

• Focusing on what we can do.g

EPA Site-wide Groundwater Feasibility Study - Tentative Schedule

• Summer 2011 – Draft Feasibility Study Report for review

F ll 2011 R d R i B d• Fall 2011 – Remedy Review Board

•Winter 2012 – Final Feasibility Study Report, Proposed Plan for public reviewpublic 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

Discussion/Questions

Contact Information

For More Information

www.epa.gov/region9/mewwww.epa.gov/region9/moffettfield

Penny ReddyGroundwater Project ManagerEPA Region 9 Superfund Division415.972.3108Reddy Penny@epa govReddy.Penny@epa.gov

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EPA Working Alternatives – Shallow A Aquifer

Alt. 1 (No Action) Description of Alternative

Alt. 2A (P&T/Slurry Wall) Existing Remedy( y ) g y

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)*Monitored Natural Attenuation (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 ConcIn Situ Redox or Optimized P&T (Med. & Low Conc. Area), MNA*

Regional PlumeIn 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

Regional Groundwater Progress UpdateRegional Groundwater Progress Update• Semi-annual water level measurements of nearly 1000

wells (Black Thursday)wells (Black Thursday)• Annual sampling of approximately 500 wells• Approximately 100 extraction wells pump over 450 gpmApproximately 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

MEW / NAS Moffett Field Site Background

• ROD Signed in 1989 to address soil and groundwater• Enforcement – Admin Order Consent Decree FederalEnforcement Admin Order, Consent Decree, Federal

Facility Agreement• Soil remedy (excavation and/or soil vapor extraction)

G d d l ll l d i d• Groundwater remedy - slurry walls, seal conduits, and 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 wallsup to 40,000 ppb inside slurry walls• Groundwater not used for potable use, but being cleaned

up to its beneficial use

VOC Plume (B2 Aquifer 75 to 110 feet bgs)

B1/A2 Aquifer B2 Aquifer

Conceptual Layout with PRBs in A Aquifer

• PRBs downgradient of high concentration areashigh concentration areas to treat residual contamination

• Modeling to determine number of PRBsnumber of PRBs

• Type of PRBs to beType of PRBs to be determined

Draft Conceptual Layout In Situ Redox in A2/B1Aquifer

• Focusing treatment on Facility-Specific Source Areas andSpecific Source Areas and High Concentration