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iaccumulated hydrocarbons to be on-site residues which have been washed <br />' into the collection pond by rain run-off <br /> No potential off-site sources currently generating hydrocarbon impacted <br /> soil were identified by Emcon at that time EMCON's investigations and <br />' subsequent report dated July 15, 1988 found no existing underground <br /> storage tanks on adjoining properties Previously, diesel tanks were <br /> removed from the Safeway site directly north of the subject site on Navy <br />' Drive <br /> 2 2 Recent Activities to Further Evaluate Wdrocarbon Impacts <br /> On October 22, 1992, MARK was requested to develop and implement a <br />' preliminary investigation of the potential presence of petroleum <br /> hydrocarbons within the soil and groundwater in the immediate vicinity of <br /> the excavation pits In response to that request, MARK prepared the <br />' Work Pian for Sampling and Analysis dated October 28, 1992 That scope <br /> of work included obtaining soil and groundwater samples from five <br /> boreholes as well as measuring dept to groundwater MARK personnel <br /> 1 conducted this field work on November 5 and 6, 1992 Locations of the <br /> boreholes are identified in Drawing 2-1 <br /> iData from this limited investigation indicated that <br /> • Groundwater in the vicinity of the former fuel storage tanks is found at <br /> 30 to 35 feet below the surface under apparently confined conditions <br /> Groundwater levels rose in all the borings, indicating that an upward <br /> vertical gradient may exist <br /> ■ Although soil samples obtained from the borings had a petroleum-like <br /> odor, analytical results for total petroleum hydrocarbons as gasoline and <br /> ' diesel fuel as well as BTEX compounds were below detection limits <br /> with the exception of one analysis for benzene This result was <br /> approximately 0 04 mg/kg, well below the LUFT action level of 10 <br /> mfg <br /> ■ Analyses of the groundwater showed that action level concentrations for <br /> ' benzene and toluene were exceeded, especially in the sample boring <br /> between the two tank pits <br /> On the basis of these observations, it appears that impacts to soil and <br /> groundwater may be limited to the immediate vicinity of the former <br /> storage tanks To respond to this condition, MARK recommends that <br /> limited further soil removal inside and between the existing excavations be <br /> carried out This work should be done using a combination of organic <br /> ' 2-2 <br /> COMPANY CONFIDENTIAL TRADE SECRET AND PROPRTI7ARY INFORMATION OF THE MAR}, GROUP Mr <br />