SITE INFORMATION AND CORRESPONDENCE_FILE 1

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a - l CHRONOLOGY OF KEI INVESTIGATION On April 4, 1986, stained contaminated soils were removed from an area of 12 feet x 12 feet. The removal of soil was conducted under the supervision of Mr. R. Crooks of San Joaquin County Health Department. Due to presence of many product lines, the soils were removed manually to minimize any accidental rupture of product lines and fuel spill. The contaminated soil excavation was stopped approximately five feet below the ground surface as no fuel odor was noted at this depth and the soil was too dense for manual removal. The general consensus, based on field observations, was that no further excavation was necessary. Two soil samples were taken using brass tubes at about four foot depths, per Mr. Crooks' instruction. The samples were analyzed for lead, total fuel hydrocarbons (THC) , and ethylene dibromide (EDB) . On June 17, 1986, a water sample was taken from existing well E2 and analyzed for TPH, BTX, lead and EDB, per instruction from Mr. Crooks of the San Joaquin County Health Department. On June 24, 1986, one 550 gallon underground tank was removed and a soil sample was taken under the supervision of Mr. Crooks. The same was analyzed for THC, BTX, lead and EDB. The on-site wells (designated as E1, E2 and E3) were installed by others unknown to either KEI or Mobil. In August, 1988 KEI collected soil samples following the removal of one gasoline storage tank at the referenced site. Two soil samples and one .water sample (collected at depths of 10 to 12 .5 feet) were analyzed by Sequoia Analytical Laboratory in Redwood City, California, for total petroleum hydrocarbon (TPH) as gasoline, and benzene, toluene, xylenes and ethylbenzene (BTX&E) . Analytical results of the soil samples showed TPH as gasoline of 200 and 240 ppm and BTX&E ranging from non-detectable to 6. 9 ppm. The water sample from the pit had 1.7 ppm TPH as gasoline and BTX&E ranging from 1. 6 to 130 ppb. To continue defining the extent of soil and ground water con- tamination beneath the site, KEI submitted a work plan dated September 16, 1988 calling for the installation of six borings. The six borings were installed on November 21, 1988 to depths of 12 to 13 feet. Soil samples collected from the borings had TPH as gasoline and diesel ranging from <1. 0 to 2 ,900 ppm; however, the three borings from the south side of the site (EB1, 2 and 3 on the attached Site Plan) had less than 10 ppm TPH, while three borings from the north side of the site (EB4, 5 and 6 on the attached Site Plan) had in excess of 1, 000 ppm of TPH as diesel above the water table. The complete results of the exploratory boring drilling are presented in KEI 's report KEI-PSS-0810-1 �. dated December 8, 1988.