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SEP 17 '99 04:47PM ESCNC F- "TONT P.4i10 <br /> File No. NFS-4463-02 Doc. No. 9909-057 <br /> September 17, 1999 <br /> boring was drilled in the northwest comer of the site to evaluate possible hydrocarbons in soil and <br /> groundwater from the 19:5 pipeline spill. Three soil samples and one grab groundwater sample were <br /> collected and analyzed for a hydrocarbon scan. There were no detectable hydrocarbons in any of <br /> the soil samples or the groundwater sample. <br /> The investigation also included collecting 16 surficial soil samples from depths of approximately 6 <br /> inches. The samples were composited by the laboratory into four samples_ The four composite <br /> samples were analyzed for pesticides. DDE and DDT were the only analyses detected. DDE <br /> concentrations ranged from 8.8 to 25 parts per billion (ppb), and DDT concentrations ranged from <br /> 4.2 to 11 ppb. These concentrations are well below the toxic levels of 1.000 ppb, as defined by Title <br /> 22 of the California Code of Regulations and the US EPA Preliminary Remediation Goals of 1,700 <br /> ppb for a residential setting. The file review and pesticide and petroleum sampling results report was <br /> issued on May 24, 1999. <br /> Percolatign Test Results <br /> Based upon review of the site plans and percolation rates reported in the May 17, 1999 geotechnical <br /> report, an additional percolation test was performed on the adjacent Pombo property on July 9, 1999. <br /> An application was submitted to the county for the test. The final half-hour of the four hour test was <br /> observed by a PHS/EHD representation. The percolation rate was calculated to be 0.24 inches per ten <br /> minutes (40 minutes per inch). The letter report for the percolation test was issued on July 30, 1999. <br /> Chevron Riryht-of-Wav Relocation Preliminary Assessment Soil Sampling <br /> In agreement with Chevron Pipeline and ESCNC's client, an investigation was proposed along the <br /> Chevron right of way on the north side of the subject site and the adjacent Pombo parcel. A <br /> workplan was submitted to San Joaquin County for review_ The criteria and requirements of the <br /> investigation were provided by Chevron and Chevron's consultants in a letter to Ridgeway <br /> MacKenzie Partnership on June 14, 1999. The investigation reports were issued on August 23, 1999. <br /> If any questions arise, or if additional information is desired,please give as a call. <br /> Very truly yours, <br /> EARTH SYSTEMS CONSULTANTS <br /> Northern California <br /> G�Pisce re� y a Sc <br /> Senior Geologist S or E ,*neer <br /> Rejistered EnoineeringGeologist 1501 eotechnical Engineer 2304 <br /> GMP/GRH:mb Ltr#204 <br /> Distribution: 1 to Addressee <br /> Attachments Drilling Permit <br /> Earth Systems Consultants Northern California 3 <br />