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0 9 <br /> Ms. Linda Turkatte, R.E.H.S. <br /> June 16, 1993 <br /> Page 4 <br /> Joaquin County indicating approximately 18 feet of <br /> clean unsaturated soils above the highest historic <br /> groundwater level; <br /> 3 . Dicloroethane and dicloropropane were not found in <br /> the soil samples in this area collected by Balbi <br /> and Chang; however, these halogenated organic <br /> compounds were found in the groundwater indicating <br /> that there may be another source for the organic <br /> contaminants in the groundwater; and <br /> 4. The relatively low horizontal groundwater velocity <br /> which results from a flat hydraulic gradient <br /> (0. 002 to 0.005) and low hydraulic conductivity <br /> silty-clayey silt when considered with the very <br /> low levels of groundwater contamination below the <br /> areas of highest soil contamination further reduce <br /> the likelihood that the groundwater contamination <br /> is related to the soil contamination. <br /> This data, combined with documented substantial hydro- <br /> carbon contamination immediately upgradient, is sufficient evi- <br /> dence to include Adjacent Landowners as additional responsible <br /> parties for the groundwater contamination at the Site. <br /> We are aware of the limited view taken by PHS/EHD of <br /> its authority to name additional responsible parties pursuant to <br /> the LOP (reference April 19, 1993, letter from San Joaquin County <br /> to Margaret Ekholm regarding Site Code 1955 ("Ekholm Letter") ) . <br /> While we do not agree with that interpretation, for purposes of <br /> this site, the Adjacent Landowners would clearly fit within even <br /> the limited definition of PHS/EHD responsible parties. <br /> C. Groundwater Investigation. PHS/EHD should permit Roek <br /> Brothers to establish that releases from the Site have not <br /> contaminated the groundwater. <br /> As discussed above, the current factual data which has been <br /> generated from investigations at the Site supports the theory <br /> that the groundwater contamination was not caused from releases <br /> at the Site. Rather, the evidence supports the theory that <br /> groundwater contamination stems for an up-gradient source. (See <br /> items B. 1-4 above. ) <br /> We have been informed, however, that PHS/EHD will not even <br /> consider evidence from the Roeks attempting to confirm the lack <br /> of connection between soil and groundwater contamination at the <br /> Site. We are also informed that the staff of the Regional water <br /> Quality Control Board - Central Valley Region supports this <br /> F:\TRN\17093\C\ROEK.JMZ <br /> 75376/JMZ/06/16/93/2 <br />