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Assessment (RFA). U.S. EPA does not require such that an RFA report be submitted <br />by SHAD; however, U.S. EPA deems that SHAD must document, in a separate chapter <br />of the Remedial, Investigation Report, the following: <br />a. Results of the Remedial Investigation of those potential SWMUs and AM <br />those were already investigated under Superfund, <br />b. Assessment of results of the SWMUs, potential SWMUS, and AOCs which <br />have not been investigated by SHAD. If SHAD deems that Attachment A <br />is not a complete list, then SHAD should recommend additional areas and <br />notify U.S. EPA of such a recommendation, and <br />C. Rationales for not investigating certain SWMU(s), potential SWMU(s), or <br />AOC(s).. <br />2. The purpose of the list of findings is not stated. Are they intended to be factual <br />statements that support a course of action? Are they provided as support for the <br />recommendations presented in the following section? Are they intended as a <br />comprehensive set of conclusions that may be drawn from the results of the <br />investigation up to now? <br />3. SHAD should not rely on automated data analysis methods such as kriging to define <br />plume extent. These methods do not take into account some of the most significant <br />information related to contaminant distribution, including: hydraulic gradients, <br />stratigraphy, and hydraulic conductivity, all of which control the direction and rate of <br />transport. Also of critical importance are: historical data identifying contaminant <br />source areas and constituents; soil gas data or other direct evidence of contaminant <br />distribution in the vadose zone; and the effects of pumping wells and recharge <br />sources on contaminant transport. <br />The limitations and assumptions in the data analysis should be adequately evaluated, <br />r to ensure that appropriate conclusions are drawn from the data. It is not clear from <br />the discussion of the kriging analysis to what extent the recommendations for <br />proposed wells were influenced by more subjective analysis, although it is stated that <br />subjective analysis was performed. <br />2 <br />