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Non-Aqueous Phase Liquids (NAPLS) and Ground Water

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“Clarification of OSWER's 1995 Technical Impracticability Waiver Policy,” September, 2011.
OSWER Directive 9355.5-32
Clarification of OSWER's 1995 Technical Impracticability Waiver Policy (PDF) (4 pp, 764KB)

The purpose of this memorandum is to provide clarification to the 1995 Office of Solid Waste and Emergency Response (OSWER) memorandum titled, Superfund Groundwater RODs: Implementing Change This Fiscal Year, July 31, 1995, (OSWER Directive 9335.3-03P) regarding the use of Technical Impracticability (TI) waivers at Comprehensive Environmental Response Compensation and Liability Act (CERCLA) sites with Dense Non-Aqueous Phase Liquid (DNAPL) contamination.

"Recommendations from the EPA Ground Water Task Force (GWTF and Cover Letter)," December, 2007.
Recommendations from the EPA Ground Water Task Force (PDF) (82 pp, 983K)

The Recommendations from the EPA Ground Water Task Force Exit EPA Disclaimer is a result of a three-year effort that was established under the OSWER's One Cleanup Program Initiative. The goal of the GWTF was to identify, prioritize, and make recommendations for ground water issues that will benefit multiple cleanup and protection programs. The report focuses on two topics the GWTF selected for evaluation: cleanup goals appropriate for dense non-aqueous phase liquid (DNAPL) source zones; and, ground water use, value and vulnerability (UVV) as factors in setting cleanup goals. It includes background information, options and GWTF recommendations to address identified issues. The cover letter of the report includes the recommendations the EPA Office of Solid Waste and Emergency Response (OSWER) is currently pursuing.

“Superfund Ground Water RODs: Implementing Change This Fiscal Year,” July 31, 1995.
OSWER Memorandum 9335.5-03P, EPA-540-F-99-005,
NTIS Order Number PB99-963220,
Superfund Ground Water RODs: Implementing Change This Fiscal Year (PDF) (2 pp, 36K)

This memo from Elliott Laws, EPA Assistant Administrator for Solid Waste and Emergency Response, to the EPA Regional Administrators discusses the importance of consistent national implementation of policies concerning Records of Decision (RODs) for sites with ground-water contamination. It emphasizes that OSWER expects that Technical Impracticability (TI) waivers will generally be appropriate for sites with contaminated ground water where restoration to drinking water standards is technically impracticable, for example, sites with DNAPLs. The memo states that "Beginning immediately, RODs addressing DNAPL contamination that do not follow the policy in favor of TI waivers at such sites much include a written justification for that departure from this policy."

"Guidance for Evaluating Technical Impracticability of Ground-Water Restoration," September 1993.
OSWER Directive 9234.2-25, EPA/540-R-93-080, NTIS Order Number PB93-963507, 27p.
Available on-line from OSWER HTML.

This interim final guidance clarifies how EPA will determine whether ground water restoration at Superfund and RCRA sites is technically impracticable and if so, what alternative measures must to undertaken to ensure that a final remedy is protective. Topics include the types of technical data needed, the criteria for decisions, the types of documentation needed, and alternative remedial strategies for sites with dense non-aqueous phase liquids (DNAPLs).

"Considerations in Ground-Water Remediation at Superfund Sites and RCRA Facilities -- Update," May 27, 1992.
OSWER Directive 9283.1-06,
NTIS Order Number PB92-963358,
Considerations in Ground-Water Remediation at Superfund Sites and RCRA Facilities (PDF) (13 pp, 81K)

This directive clarifies and expands OSWER's 1989 directive "Considerations in Ground-Water Remediation at Superfund Sites" (see "remedy selection"), especially with regard to non-aqueous phase liquid (NAPL) contaminants. The directive recommends: that the likelihood of NAPL contamination, especially dense NAPLs (DNAPLs), should be evaluated as early as possible; where NAPLs are likely, the potential nature and extent of contamination should be characterized to determine appropriate remedial actions; further contamination (dissolved or NAPL) migration should be minimized by using early response actions; early actions should be coordinated with later actions in a phased approach; and ground water cleanup actions should be designed to include careful monitoring and provisions for modifying them over time to improve their effectiveness. For sites where it can be demonstrated to EPA that achieving chleanup standards is technically impracticable, EPA may issue a waiver for Suerfund sites or midify the permit or enforcement order for RCRA facilities. For these cases, EPA will determine alternative remedial objectives that protect human health and the environment.

See also:

"Presumptive Response Strategy and Ex-Situ Treatment Technologies for Contaminated Ground Water at CERCLA Sites, Final Guidance," October 1996.
OSWER Publication 9283.1-12, EPA/540/R-96/023, NTIS Order Number PB96-963508, 39p.
Available on-line from OSWER HTML.

This guidance outlines the "phased approach" strategy for addressing contaminated ground water. The strategy integrates the site characterization, early actions, remedy selection, design, implementation, and performance monitoring phases. The strategy emphasizes ways to select acheivable remedial objectives and ways to optimize the selected remedy so that it is more effective, less costly, and takes less time. The guidance also identifies presumptive technologies for treatment of extracted ground water, which are to be used to streamline the Feasibility Study for sites which evaluate pump and treat remedies.

Other Reports:

"DNAPL Remediation: Selected Projects Where Regulatory Closure Goals Have Been Achieved," August 2009.
EPA 542-R-09-008,
DNAPL Remediation: Selected Projects Where Regulatory Closure Goals Have Been Achieved (PDF) (52pp, 897K)

The  purpose  of this paper is to highlight sites where dense nonaqueous phase liquid (DNAPL) source reduction has been demonstrated as an aid in meeting   regulatory  cleanup  goals.  The  presence  of  DNAPL  in  the subsurface  can  serve  as  a  long-term source of dissolved contaminant plumes  in  groundwater,  making  it  more difficult to reach regulatory
closure.   However,   once  the  DNAPL  source  is  addressed,  residual groundwater  plumes  may  be  more amenable to treatment, including less aggressive  techniques  such  as  monitored natural attenuation (MNA) or bioremediation.  This  paper  updates  the  document, DNAPL Remediation: Selected  Projects  Approaching  Regulatory Closure, prepared in 2004 by providing more recent information on technologies and on five additional selected  sites  at  which  DNAPL  source  reduction  technologies  were applied.

"The DNAPL Remediation Challenge: Is There a Case for Source Depletion?," December 2003.
ORD publication EPA/600/R-03/143,
The DNAPL Remediation Challenge: Is There a Case for Source Depletion (PDF
) (129 pp, 1.1MB)

This report contains the findings and recommendations of a panel of national and international scientists and engineers selected by EPA's Office of Research and Development, National Risk Management Research Laboratory (ORD/NRMRL). All members are recognized authorities on the topic of DNAPL remediation. The panel was asked to conduct a critical, independent review of the current state of the science regarding difficulties and benefits associated with remediation of DNAPL source zones and research needs to address this important environmental challenge. The report presents the views of the panel and does not necessarily represent Agency views or policies.

"Ground Water Issue: Light Nonaqueous Phase Liquids," July 1995.
ORD and OSWER joint publication EPA/540/S-95/500,
NTIS Order Number PB95-267738,
Ground Water Issue: Light Nonaqueous Phase Liquids (PDF) (28 pp, 244K)

This issue paper from the Technical Support Project discusses light nonaqueous phase liquids (LNAPLs), or NAPL which has a density less than water. The paper summarizes LNAPL fate and transport and remediation technologies of use for LNAPL recovery. It includes a table of the physical properties of chemical compounds most prevalent at Superfund sites which have a specific gravity less than water.

"DNAPL Site Characterization," September 1994.
OSWER Publication 9355.4-16FS, EPA/540/F-94/049,
NTIS Order Number PB94-963317,
DNAPL Site Characterization (PDF) (12 pp, 686K)

This fact sheet provides a strategy for the investigation of dense non-aqueous phase liquids (DNAPLs) at sites, including a flow chart of suggested activities and suggestions on site conceptualization and objectives. It also summarizes noninvasive and invasive field methods for DNAPL characterization and provides a table summarizing how one might determine, infer or suspect DNAPL presence at a site.

"Evaluation of the Likelihood of DNAPL Presence at NPL Sites, National Results," September 1993.
OSWER Publication 9355.4-13, EPA/540-R-93-073,
NTIS Order Number PB93-963343,
Evaluation of the Likelihood of DNAPL Presence at NPL Sites, National Results (PDF) (114 pp, 1.5MB)

This publication presents the results of a survey of 712 National Priority List (NPL) sites to estimate the proportion of NPL sites where dense non-aqueous phase liquids (DNAPLs) may be present. The project also assesed the usefulness of various indirect indicators of DNAPL presence associated with historical site information and ground water contaminant information.

"Estimating Potential for Occurrence of DNAPL at Superfund Sites," January 1992.
OSWER Publication 9355.4-07FS,
NTIS Order Number PB92-963338CDH,
Estimating Potential for Occurrence of DNAPL at Superfund Sites(PDF) (10 pp, 472K)

The presence of DNAPL in soils and aquifers can control the ultimate success or failure of remediation at a site, but because of the complex nature of DNAPL transport and fate, it may often be undetected by direct methods. This fact sheet provides a guide for estimating the potential for the presence of dense non-aqueous phase liquids (DNAPLs) at a site based on historical site use information and site characterization data. It summarizes the definition of DNAPL and presents five conceptual models for its release and presence at sites. It includes a series of flow charts for deciding whether a site has a high, moderate, or low potential for containing DNAPL. It also includes step by step worksheets for calucating effective solubility of single-component DNAPL and for assessing the liklihood of DNAPL presence based on organic concentrations in soil samples; and a glossary of terms related to DNAPLs.

"Ground Water Issue: Dense Nonaqueous Liquids," March 1991.
ORD and OSWER joint Publication EPA/540/4-91-002, NTIS Order Number PB91-195974, 21p.

This issue paper of the Technology Support Project provides an overview from a conceptual fate and transport point of view, of DNAPL phase distribution, monitoring, site characterization, remediation, and modeling. It includes a table of the physical properties of chemical compounds most prevalent at Superfund sites which have a specific gravity greater than water.

See also: technical impracticability; remedy selection/RODs.


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