A Comparison of The EPA MNA Directive and The ASTM RNA Standard Matt Small, U.S. EPA, USTPO, Region 9 Hal White, U.S. EPA, OUST, HQ 10th Annual UST/LUST Conference Long Beach, CA 3/30-4/1/98 Two Natural Attenuation Guidance Documents EPA OSWER Directive 9200.4-17: Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites (Interim Final, Dec. 1, 1997) (www.epa.gov/OUST/directiv/d9200417.htm) ASTM: Standard Guide for Remediation of Groundwater by Natural Attenuation at Petroleum Release Sites (www.astm.org/COMMIT/e-50.htm#sponsor) Other Sources of Information Lustline (NEIWPCC); Bulletin 28, February 1998 Underground Tank Technology Update (UTTU; U. of Wisconsin-Madison) Vol. 12, No. 2, March/April 1998 EPA/OUST Fact Sheet Draft--March 1998 Applicability and Definition EPA ASTM Applicability: RCRA, Superfund, and UST program sites. Definition: Reliance on natural attenuation processes to achieve remedial objectives within a reasonable time frame. Applicability: UST release sites. Definition: A remedy where natural physical, chemical and biological processes will effectively achieve remedial goals. Contaminants of Concern and Affected Media EPA ASTM Petroleum hydrocarbons, organic solvents, and other hazardous chemicals, inorganics, metals, radionuclides, and mixed waste in groundwater and soil. Petroleum hydrocarbons in groundwater. Remedy Selection Criteria EPA ASTM MNA is not a default or presumptive remedy, it is one of many potential remedies. Selection is site and program specific. Requires site characterization, source control, monitoring, and contingency plans. In general, RNA should not be considered a presumptive remedy. Selection requires site characterization, assessment of potential risks, and evaluation of potential to meet remedial goals Site Characterization EPA ASTM Adequate to demonstrate that MNA is an appropriate remedial technology, generally more extensive than active remedial technologies. Same requirements as for any other remedial option. Recommend collecting secondary lines of evidence at new sites. Evidence of Natural Attenuation EPA ASTM Primary and secondary lines are typically required. Tertiary (field or microcosm data) when primary and secondary are inadequate or inconclusive. Primary lines are usually sufficient. Optional (or tertiary) and secondary lines to support RNA selection at sites with no historic data. Groundwater Plume Status EPA ASTM MNA is more likely an appropriate remedial technology at sties where plume is no longer increasing or is shrinking in size. (a stable plume is evidence of inadequate source control; very long remediation time) RNA is appropriate for stable or shrinking plumes, and in some cases, expanding plumes if risk reduction and performance goals are met. Remediation Time Frames EPA ASTM Time required to reach remedial goals is site-specific and should be “reasonable” when compared with active remedial technologies. Time frame must be considered as part of establishing remedial goals. Time frame is determined by regulatory agency. Source Control EPA ASTM Source control measures evaluated at every site. Remove free product to the maximum extent practicable. Source area removal and/or treatment is preferred. Integrate source area control considerations into remedial decisionmaking at all RNA sites. Degree of source control or removal required is at the discretion of the regulatory agency. Performance Monitoring EPA ASTM Site-specific, should be continued as long as concentrations are above cleanup goals. Continue 1 to 3 years after goals met to confirm that concentrations at or below cleanup goals. Monitoring frequency based upon sitespecific conditions: potential receptor impacts; achievement of remedial goals or expectation of being met; plume status; institutional controls. Remediation Objectives EPA ASTM Cleanup levels are sitespecific and should consider such factors as risk and current and potential future uses of the affected resource. (regulatory expectation that groundwater will be restored to beneficial uses) Determine remedial goals by applying riskbased corrective action. Goals may be concentration target levels or performance criteria, including containment. Contingency Remedies EPA ASTM The need for contingency plans should be evaluated for every MNA site. Implement contingency if concentration decreases do not meet expectations. Should be implemented if data indicate that RNA will not meet remedial goals, including containment. No Further Action EPA ASTM Monitoring should Plume shrinking or stable. No existing or continue as long as potential receptor concentrations impacts. NFA when remain above remedial goals are met required cleanup levels. Once levels are or it is expected that NA will continue and met, additional monitoring is needed ultimately meet goals. to ensure that clean Institutional controls in place if needed. conditions persist. Summary Guidance documents differ mainly in: Scope: ASTM RNA for petroleum in groundwater: a subset of the MNA directive, which also encompasses RCRA and Superfund, plus soil. Site Characterization: MNA directive recommends more detail than for active remedies. Plume Status: RNA allowed for expanding plumes with no receptor impacts. MNA requires shrinking or no longer expanding plume for application. Summary Source Control Requirements: , MNA explicitly addresses free product recovery-- required “to maximum extent practicable”. RNA defers to regulatory agency. Contingency Remedies: MNA advocates evaluation at all sites. Remediation Objectives: MNA expresses regulatory expectation of restoration of groundwater to beneficial uses. Summary Performance Monitoring/NFA: MNA requires monitoring until remedial goals are met. RNA allows for NFA if it is expected that NA will continue and eventually meet remedial goals.
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