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CLEARWATER . G R O U P, I N C F rear—n nee ;t a I S.r rc- that this additional well would not provide sufficient information to justify the cost (measured primarily in the passage of additional time, as the expense of the well is to be borne by 7-11) associated with its installation This finding is based on the following facts • The well to be installed is slated for an area of the site that has been shown by previous sampling to be virtually free of contamination Given site hydrogeology and the sheer fact that the mass of contaminants dissolved in site groundwater can be shown to be fairly insignificant, it is not likely that significant contaminant migration has occurred in the period following the collection • Even if the well were to be installed, and samples collected confirmed the presence of low concentrations of contamination, subsequent well installations and sampling would be complicated by the presence of the confirmed problem at the Southland site The contemplated additional well would either tell us that concentrations of contaminants are low, or are below detectable levels, and that further downgradient exploration is made problematic by the . presence of 7-11 contamination In other words, the data provided by this installation would really add nothing to the material collected and evaluated to date My review of the file indicates that the information required to complete a formal evaluation for file closure has already been collected The effect of source (impacted soil) removal has been documented by the measured decrease of contaminant concentrations in monitoring wells immediately downgradient of the former USTs Actual measured concentrations have been quite low all along If any additional effort is to be invested in this file, it appears as if this effort would be best spent quantifying the volume of residual contamination present and completing a basic evaluation of risk posed by these compounds It seems as if a RBCA Tier 1 evaluation accompanied by the residual contaminant volumetric calculation would be the wisest use of available resources Additionally, the well survey should be restricted to parcels between the former UST basin on the subject site and the 7-11, as properties downgradient of the 7-11 are at risk due to the release at this property, not the subject site A measure of prudence may include the water use assessment of one or two additional parcels to the north and the east, but a 2000 foot radius seems difficult to technically defend With your concurrence, a modification in the water use survey will be documented