Overview of Remedial Approaches

at Superfund Fractured Bedrock Sites

Edward Gilbert, CPG

Technology Assessment Branch

Technology Innovation and Field Services Division

Office 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 Profiles

http://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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