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1 December 20, 1994 Harding Lawson Associates <br /> 256661 <br /> I San Joaquin County <br /> Mr Harlin Knoll <br /> J Page 7 <br /> RECOMMENDATIONS <br /> According to the RWQCS Tri-Regional Guidelines, where groundwater impacts have occurred, the <br /> extent of impacted soil and groundwater is required to be evaluated Based on,these guidelines and <br /> HSC's phased approach to the characterization of these sites, HLA currently recommends the <br /> installation of one monitoring well at each UST site The proposed location at Site A is adjacent to <br /> the UST excavation (Plate 7) while the proposed Site B well is located approximately 75 feet in the <br /> downgradient direction from the former UST location (Plate 8) <br /> Soils beneath the fuel oil bunker have been impacted by petroleum hydrocarbon, however potential <br /> groundwater impacts have not been evaluated Therefore HLA recommends that the depth to water be <br /> measured by installing a temporary piezometer through the floor of the bunker at one of the previous <br /> sampling locations This data can be used to determine if hydrocarbon impacted soils immediately <br /> below the bunker are in contact with the groundwater In addition, two soil samples should be <br /> collected from the previous sampling locations and a leachability test performed on these samples to <br /> evaluate the potential for the hydrocarbons to leach into groundwater HSC has recently been <br /> requested by the RWQCB to perform leachability tests at two historic surface spill sites at the HSC <br /> facility where fuel oil has impacted soils to the water table The RWQCB will use this data to <br /> evaluate the need to remediate these two sites HLA believes that to be consistent with the RWQCB <br /> recommendations involving similar contaminants and site conditions, a leachability test should be <br /> performed at the fuel oil bunker <br /> We appreciate the opportunity to subnut this letter report to the SJCEHS If there are any questions <br /> regarding the information presented in the report, please contact either of the undersigned <br /> J Yours very truly, <br /> HARDING LAW N ASSOCIATES <br /> is Beegan <br /> Project Geo ognst <br /> CA <br /> chael J Leacox, <br /> Associate Geologist <br /> 1. <br /> 1 <br />