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Moffett/Ellis/Whisman Presentation to the Moffett RAB
 

Moffett/Ellis/Whisman Presentation to the Moffett RAB

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

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

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    Moffett/Ellis/Whisman Presentation to the Moffett RAB Moffett/Ellis/Whisman Presentation to the Moffett RAB Presentation Transcript

    • Middlefield-Ellis-Whisman (MEW) Superfund Study Area S f S EPA Update:Site-Wide Groundwater Feasibility Study y yNAS M ff tt Fi ld R t Moffett Field Restoration Advisory ti Ad i Board May 12, 2011
    • 2
    • Purpose of Site-wide GroundwaterFeasibility StudyEvaluate 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
    • Key Feasibility Study Inputs Pilot tests Community Criteria and Suggested Strategy Paper
    • Community Criteria and SuggestedStrategy Paper1) 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 property2) Incorporate results from optimization evaluations3) Consider specific technologies
    • Scope of GroundwaterCleanup• 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
    • EPA Screening of TechnologiesIn 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 ExcavationBarriers – 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 andDisposal 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.
    • Barriers ContinuousPermeable 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
    • 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
    • Technologies Retained1. Groundwater Extraction and Treatment2. In Sit R d T h l i (i l di I Sit2 I Situ Redox Technologies (including In Situ Bioremediation, In Situ Chemical Oxidation and Zero Valent Iron Injections) to treat high conc. areas j ) g3. Permeable Reactive Barriers (PRB)4. Monitored Natural Attenuation (as component of an alternative) lt ti )
    • Projected VOC Plume – A Aquifer (0 to45 feet bgs) 1992 2009 2019
    • EPA Working Alternatives – Shallow A AquiferAlt. 1 No ActionAlt. Extraction & Treatment (Existing & Optimized)2A/2BAlt. 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
    • Conceptual LayoutOptimized Pump and Treat Nort Sout h of h of 101 101
    • Conceptual LayoutIn 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
    • Conceptual Layoutwith 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
    • Projected VOC Plume – B1/A2 Aquifer(50 to 75 feet bgs) 1992 2009 2019
    • VOC Plume (B2 Aquifer 75 to 110 feet bgs)
    • EPA Work Alternatives – Deeper AquiferAlt. 1 No ActionAlt. Extraction & Treatment (Existing & Optimized)2A/2BAlt. 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 gAlt. 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 withPRBs 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
    • 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
    • EPA Site-wide Groundwater FeasibilityStudy - 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 GroundwaterProperty Owner Meetings – February 15 Upcoming Meetings – Property Owners Meeting – May 24
    • Discussion/Questions
    • Contact InformationFor More Informationwww.epa.gov/region9/mewwww.epa.gov/region9/moffettfieldPenny ReddyGroundwater Project ManagerEPA Region 9 Superfund Division415.972.3108Reddy.Penny@epa.govReddy Penny@epa gov
    • 26
    • EPA Working Alternatives – Shallow AAquiferAlt. 1 (No Action) Description of AlternativeAlt. 2A (P&T/Slurry Wall) ( y ) Existing Remedy g yAlt. 2B (P&T/Slurry Wall) Existing Remedy Optimized for mass removalAlt. 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
    • 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
    • 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
    • VOC Plume (B2 Aquifer 75 to 110 feet bgs)
    • B1/A2 Aquifer B2 Aquifer
    • Conceptual Layoutwith 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
    • Draft Conceptual LayoutIn Situ Redox in A2/B1Aquifer• Focusing treatment on Facility- Specific Source Areas and High Concentration