Overview of Remedial Approachesat Superfund Fractured Bedrock Sites

Edward Gilbert, CPGTechnology Assessment Branch

Technology Innovation and Field Services DivisionOffice of Superfund Remediation & Technology Innovation

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Remedial Technologies

• Groundwater extraction and treatment (P&T)• In situ Chemical Oxidation (ISCO) / Reduction (ISCR)• Enhanced In Situ Bioremediation

– Biostimulation– Bioaugmentation

• In Situ Thermal– Electrical Resistance Heating (ERH)– Thermal Conductive Heating (TCH)– Gas Thermal Remediation (GTR)– Steam Enhanced Extraction (SEE)– Radio Frequency Heating (RF)

• Monitored Natural Attenuation (MNA)

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Contaminants of Concern

• VOCs• SVOCs/PAHs• Metals• Pesticides/PCBs• Dioxins/Dibenzofurans• Radionuclides

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Frac Rock Site Decision Documents

• Data mining of CERCLIS– FY2000 – 2012 (partial) RODs, ESDs, or Amended RODs– Queried text for any mention of fractured bedrock

• Groundwater Remedies• 76 Sites• 87 Operable Units in fractured bedrock

• DNAPL Remedies• 7 Sites• 7 Operable Units in fractured bedrock

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Groundwater at Fractured Bedrock Sites

• Selected Remedies at 87 OUs– 30 GW Extraction (including multiphase extraction)– 16 Bioremediation– 13 Oxidation (ISCO) – 3 Reactive Walls– 2 Chemical Reduction (ISCR)

– 36 No Action; deed restrictions; groundwater use/well drilling regulation; zoning regulation; covenants; monitoring; natural attenuation; MNA; etc.

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NAPL at Fractured Bedrock Sites

• Selected Remedies at 7 Sites– 5 Free Product Recovery– 1 Bioremediation (oxygen addition)– 2 ISCO– 1 Vapor Extraction– 1 ERH– 1 Non-fundamental change (ESD)

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CLU-IN’s Fractured Bedrock Project Profileshttp://clu-in.org/products/fracrock/

• 248 profiles submitted– 114 GW Pump and Treat

• Plus 13 Multi Phase Extraction

– 67 Bioremediation– 55 Chemical Oxidation (in situ)– 25 ‘Soil’ Vapor Extraction– 9 Thermal Treatment (in situ)– 5 Flushing (in situ)

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CERCLIS

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CLU-IN

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Region 2 Sites

• 31 Sites with contaminated gw in fractured rock– 21 ROD– 10 Pre-ROD

• Selected remedies at 19 sites– 9 P&T (+ 1 possible)– 4 Enhanced bio (+ 1 possible)– 2 ISCO (+ 1 possible) – 3 MNA– 1 Leachate collection for containment – 4 TI Waivers

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Karst

• Very difficult to characterize adequately– Conduits – Very high and turbulent groundwater flow velocities – Extreme heterogeneity– Dual-porosity and dual-permeability regimes– Sediment transport

• RODs for 71 sites – 53% no active groundwater remedy– 37% pump and treat– 21% some form of in-situ remediation technology

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Remedial Effectiveness?

• Jury is still out…– Shift from P&T to other technologies

• A method to track remedy progress/success?• Need for fractured bedrock site database

– CERCLIS– SEMS– Clu-In

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Technical Impracticability Waivers*

• 91 waivers at 85 sites; FY88-FY11• 85 waivers applied to groundwater

– Complex geology cited as a contributing factor in the rationale for 54 of the 85 waivers• Fractured bedrock• Karst• Heterogeneous soils with low permeability

– VOCs, metals, SVOCs and PAHs

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* Summary of Technical Impracticability Waivers at National Priorities List Sites, EPA 2012

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Technical Impracticability Waivers*

• In light of the continuing scientific advances in groundwater remediation technologies which continue to evolve, regions should not be limited by previously-approved TI waivers described in this technical report as justification for what may be appropriate when evaluating and documenting current or future TI waivers.

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* Summary of Technical Impracticability Waivers at National Priorities List Sites, EPA 2012

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Future?

• In Situ Thermal• Enhanced In Situ Bioremediation*• ISCO/ISCR*• Combined remedies/treatment trains• Continued use of P&T for control/containment• MNA

* Fracking - Increased distribution/delivery

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