Spring, 1999

Guidance For EPA Technical Impracticability Of Ground-Water Restoration

Restoration of contaminated ground water can be expensive and often an unrealistic venture. Remediation systems can produce large initial reductions in contaminant levels that often stabilize or rebound above the regulated clean-up levels. In other situations, complex geology coupled with prolonged releases and high contaminant retardation can create zones that are impractical to remediate.

The United States Environmental Protection Agency (EPA) recognizes that all releases cannot be restored to applicable ground-water quality levels. In response, the EPA has developed a guidance document that outlines criteria for determination of Technical Impracticability (TI) in attaining ground-water clean-up levels, which allows for remedial alternatives. States authorized for Hazardous and Solid Waste Amendments (HSWA) Corrective Actions will have primary authority for remedy decisions and TI determination, remaining generally consistent with the EPA process.

The TI decision process should be part of the site investigation, remedy selection and in most cases remedy action and performance evaluation. Sites which have yet to begin remedial actions, along with sites that have remedial systems in place with diminishing returns or poor contaminant recovery are eligible for TI evaluation. TI decisions do not necessarily encompass an entire site or plume, but can be made for specific contaminants or areas of impact.

The EPA recommends taking a phased approach for determining restoration potential. In general, this approach begins with site characterization, with allowances for intermediate clean-up actions. The phased approach represents a general overview for site remediation or TI determination, however, with slight differences depending on site classification.

Regulatory Framework for TI Decisions

Engineering feasibility and reliability are the primary considerations for determination of TI. The regulatory basis for determinations of TI at Superfund and Resource Conservation and Recovery Act (RCRA) Corrective Action program sites have different overriding criteria. In either case, the EPA explicitly states that cost should not be a major factor in TI decisions, unless compliance would be inordinately exorbitant.

Superfund

For a site to be eligible for any remedial alternative, it must satisfy the following conditions: the remedy or TI decision must be protective of human health and the environment; and the remedy or TI decision must meet or provide basis for waiving the Applicable or Relevant and Appropriate Requirements (ARARs) identified for the action.

RCRA

The RCRA program specifies prior to a TI waiver, the impacted media should be within the range of 10^-4 to 10^-6 lifetime cancer risk or hazard index of less than one for non-carcinogens as appropriate. Conditions in which attainment of media clean up may not be required are; 1) remediation would provide no significant reduction in risks to actual or potential receptors; 2) the release does not occur in, or threaten ground waters that are current or potential drinking water sources; and 3) remediation of the release to media clean-up standards is TI.

Timing of TI Decision

TI decisions are either made when a final site decision document is being developed or after the remedy has been implemented and monitored for a period of time. Most TI decisions are made after interim or full scale aquifer remediation have been implemented. However, pre-implementation or Afront-end@ TI decisions are made when supported by detailed site characterization and data analyses.

Determination of Remediation Difficulty

In determining the difficulty of remediation, the EPA recommends analyzing five areas of concern (AOC); site use, chemical properties, contaminant distribution, geology and hydrology. Each of the AOCs have specific indicators which determine remedial difficulties on a site-specific basis.

The volume, duration and type of release (acute or continual) are primary indicators for determining remedial difficulty with respect to site use. Biotic/abiotic decay potential, volatility and retardation potential are important chemical properties which can lead to difficult removal. Within the category of contaminant distribution, the potential contaminant phase, volume impacted and vertical extent are all important indicators. The impacted geology with respect to stratigraphy, texture of unconsolidated deposits, degree of heterogeneity and fracturing of bedrock all have predominant roles in the difficulty of site restoration. Finally, site hydrology with respect to hydraulic conductivity, vertical flow and temporal variation all impact the difficulty of site restoration.

TI Evaluation Components

Prior to compilation and analyses of the TI components, it is strongly recommended to meet with the governing environmental agency to discuss specific elements of the TI evaluation. The meeting is meant to organize and confirm the TI evaluation structure and components, thus, decreasing costs and accelerating the review and decision process. Specific components identified within the EPA guidance document for a TI evaluation must include the following, when applicable; 1) specific ARARs or media clean-up standards in which TI determination are sought; 2) spatial area which TI decision will apply; 3) conceptual model describing site geology, hydrology, ground-water contamination, transport and fate; 4) evaluation of restoration potential of site, which include data and analyses of TI from an engineering perspective; 5) estimate cost of existing or proposed remedy options, including construction, operation and maintenance; and 6) any additional information the EPA deems warranted.

 Evaluation Process and Duration of TI Decision

The first step in the EPA's review process is to assess the completeness and adequacy of the TI evaluation. The EPA or authorized state DEP retains the option to request revisions and additions to the report. After a period of public comment and agency review, the TI decision is rendered.

Both Superfund and RCRA Corrective Action TI decisions are subject to future review. At Superfund sites, the TI waiver would remain in effect so long as the strategy is protective of human health and the environment. RCRA TI decisions would be incorporated into facility permits or enforcement orders and, therefore, would be subject to continual oversight. The EPA would conduct a full assessments every five years at any site where contamination remains above levels that require for unrestricted use. The EPA does retain the right to enact further remedial actions at any site as it deems necessary. The protectiveness of TI decisions at both a Superfund Site and a RCRA facility would be ensured through a monitoring program.

Conclusion

For over 54 years, Leggette, Brashears & Graham, Inc. (LBG) has incorporated the most appropriate technologies and regulations in each of our projects to best suit the needs of our clientele. As a result of continually staying ahead of the environmental field, we have saved our clientele valuable time and money over the long term. If you would like more information concerning the EPA TI process, please contact your local LBG office or Michael Manolakas at (203) 452-3100 or Rich Townsend at (651) 490-1405.