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DAMES & MOORE A PROFESSIONAL 1-11 41TED PARTNE RSHIP <br /> underlying the site has not been adversely impac ed by the presence <br /> of diesel fuel in the soils and that the existing monitoring well <br /> network is adequete to detect migration of diesel fuel entering the <br /> groundwater system based on the following: <br /> 1. Soil samples collected directly above the Water table surface <br /> (35 feet below ground surface) did not contain <br /> any significant concentrations of petroleum hydrocarbons; <br /> 2 . Groundwater levels at the site have declined approximately 15 <br /> feet since the initial investigation in 1587 ; and <br /> 3 . Given the relatively large areal extent of soil determined to <br /> contain diesel fuel, and the fact that the 10, 000 gallon <br /> diesel tank was reported to be present at the site for over <br /> 30 years, Dames & Moore judges that the rel ase of diesel fuel <br /> is not recent and likely occured over a number of years. <br /> Given an estimated groundwater velocity of 0. 57 cm/day, it is <br /> our judgement that diesel fuel entering and migrating in the <br /> groundwater system would be detected by tie existing well <br /> network. <br /> Two rounds of groundwater sampling perform d in July 1987 and <br /> June 1988 indicate that grondwater in the vici ity of the <br /> maintenance shop has not been adversly impacted. At the request <br /> of your agency, Dames & Moore sampled the existing wells again in <br /> Janaury 1989 and submitted the results of this additional <br /> monitoring in a letter report dated February 3 , 1989 . The results <br /> of this sampling supports the conclusion that groundwater in the <br /> vicinity of the maintenace shop has not been adversely impacted. <br /> Pentaclorophenol (PCP) was detected in shallow soil samples <br /> collected in the vicinity of a truck parking a ea during site <br /> investigations performed by Bechtel and Klein elder in 1985 and <br /> 1987 , respectively. The results of this soil sampling indicated <br /> that concentrations of PCP were very low, and the extent of <br /> contamination is limited to the shallow soils (lass than 12 inches) <br /> in the immediate area of one sample location. he results of both <br /> of these investigations are presented in Klein elder's report <br /> entitled "Soil and Groundwater Assessment, American Moulding and <br /> Millwork" dated November 4, 1987 . <br /> Remediation of the PCP "hot spot" would req ire the excavation <br /> and disposal of less than one cubic yard of soil. The Department <br /> of Health Services indicated in a April 7, 1988 Letter to AM&M that <br /> this approach would be appropriate for addressing this minor <br /> problem, and that a soil cleanup level of 3 ppm would appear to be <br /> appropriate for the site. As stated in the FS/ P report prepared <br /> by Dames & Moore, the focus of the document was on the diesel spill <br />