SITE INFORMATION AND CORRESPONDENCE_FILE 1

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. From:staff To: Erin Garner • Date:119196 Time: 11:40:47 • Page 5 of 11 Subject: Supplemental Instructions to Slate Water Board December 2, 1995, Interim Guidance on Required Cleanup at Low Risk Fuel Sites January 5, 1996 / Page 2 LOW RICA SOILS CASE Deflnitlon. 1) The leak has been stopped and ongoing sources, including free product, removed or remediated. The tank or appurtenant structure that leaked must be repaired or permanently closed per Chapter 7, Section 2672 of the UST regulations. Free product shall be removed to the extent practicable per Chapter 5, Section 2655 of the UST regulations. Free product or soil which contains sufficient mobile constituents (leachate, vapors, or gravity flow) to degrade groundwater quality above water quality objectives or result in a significant threat to human health or the environment should be considered a source. For old releases, the absence of current groundwater impact is often a good indication that residual concentrations present in the soil are not a source of pollution. In general, it impacted soil is not in contact, or expected to come in contact, with or very close to the groundwater, it is unlikely that a is a significant source of pollution. 2) The site has been adequately characterized. The extent of the subsurface impact should be defined to the degree that is necessary to determine if the site poses a threat to human health, the environment, or other sensitive nearby receptors. The level of detail required at a given site will depend upon the presence or absence of potential receptors and exposure pathways. Delineating plumes to non-detect levels is not required at all sites. It is assumed that subsurface conditions are highly variable and that there is always some uncertainty associated with evaluating data at a site. However, the cost of obtaining additional data must be weighed against the benefit of obtaining that data and the effect the data may have on the certainty of decisions to be made at the site. 3) Little or no groundwater impact currently exists and no contaminants are found at levels above established MCLS or other applicable water quality objectives. By definition, soils only cases do not have significant groundwater impacts. 4) No water wells, deeper drinking water aquifers, surface water, or other sensitive receptors are likely to be impacted. 5) The site presents no significant risk to human health. The American Society of Testing and Materials' (ASTM) standard for Risked Based Corrective Action (RBCA), ASTM E-1739-95, details a framework and provides a methodology to perform a tiered risk analysis at petroleum release sites. This methodology incorporates EPA risk assessment practices to determine non-site specific (tier 1 look up table which provides generic risk based screening levels) and site specific (tier 2 and tier 3) clean up levels that are protective of public health and environmental resources.