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-3- The soils described above are shown on the attached boring logs. The logs also denote sampling depths. The soil sample from boring B5 was collected primarily for logging purposes and was not analyzed . Soil samples were delivered under chain-of-custody procedures to a state certified laboratory for hazardous waste testing. No odors were apparent in any of the samples or drill cuttings. RESULTS OF ANALYSES Samples were analyzed by gas chromatography using EPA method 8020 and the "LUFT" method developed by the California Department of Health Services (DOHS) . (LUFT refers to a state manual entitled "Leaking Underground Fuel Tanks") . The samples were analyzed as follows : - Total petroleum hydrocarbons (TPH) - volatile fraction as gasoline with benzene , toluene, ethylbenzene, and xylene (BTEX) . - Total petroleum hydrocarbons (TPH) - non-volatile fraction as diesel . The laboratory report (attached) indicates that no petroleum hydrocarbons were found above detection limits in any of the samples. The detection limits are 10 milligrams/kilogram (mg/kg) for gasoline and diesel, 5 micrograms/kilogram (ug/kg) for benzene, toluene and ethylbenzene and 15 ug/kg for xylene. (Nig/kg is loosely equivalent to parts per million and ug/kg is equivalent to parts per billion) . DISCUSSION A spill or release of product will generally move straight down through the soil with very little lateral movement until ground water has been reached or may pond on a semi-permeable to impermeable layer . If ground water is encountered the hydrocarbons will generally float on the surface and migrate in the direction of ground water flow. Conversations with Eleanor Ratliff of San Joaquin County Environmental Health Division, indicate that ground water is in excess of 40 feet below ground in the area of the project site. Nonetheless lateral movement of product might be expected along the interface of the fill material and the less permeable, clayey native soil . This situation enhances the likelihood of finding any contamination which might be present. The samples in the (diesel tank) pits were collected at locations most likely to reveal contamination should a leak or spill have occurred. Two samples were taken in each pit to cover whichever end was the "re-fill end" where spillage is most likely. The samples were taken in the native soil just below the backfill material (s) . While it is possible in these investigations to miss a contaminated area it seems unlikely due to the situation described above and the precautions taken by MacKinnon Environmental Consulting (MEC) to ensure sampling was adequate. However no consultant can guarantee complete coverage of a site as it is impossible to sample all points.