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Mr Kyle Christie Project 0805-146 03 January 24, 1996 Page 2 Dissolved gasoline hydrocarbons were detected in the groundwater samples collected from the three monitoring wells. Purgeable halocarbons were not detected, except for 1,2-dichloroethane, which was detected in monitoring well MW-2 Fecal and total coliform bacteria were not detected in the sample collected from well MW-3 In January 1993, RESNA observed the drilling of seven soil borings (B-13 through B-19) and the installation of two groundwater monitoring wells (MW-4 and MW-5) and four vapor extraction wells (VW-4 through «V-7) Results of this assessment were reported in RESNA's "First Quarter 1993 Status Report" (June 9, 1993, Report No 31009-7) The report indicated that hydrocarbons present in soli below 25 feet and in groundwater were probably from an off-site source Therefore, ARCO requested that an investigation of soil and groundwater be performed off site and upgradlent of the ARCO station to evaluate whether hydrocarbons were present upgradlent of the site. In October 1993, RESNA observed the drilling of two soil borings (B-20 and B-21) and the installation of two groundwater monitoring wells (MW-6 and MW-7) Analytical data indicated that residual hydrocarbons were present in the borings (RESNA, February 15, 1994, Report No 31009-9) Total petroleum hydrocarbons as gasoline (TPHG) and .� benzene concentrations ranged from below laboratory detection limits to 1,200 parts per million (ppm) and from below laboratory detection limits to 12 ppm, respectively The highest concentration was detected at 20 feet below ground surface (bgs) Dissolved gasoline hydrocarbons were detected m the monitonng wells In addition, HVOCs were also detected in groundwater samples collected from monitoring wells MW-6 and MW-7 In May 1995, EMCON prepared an off-site evaluation report ("Evaluation of Off-Site Sources," May 5, 1995) EMCON identified four potential upgradient/off--site sources (1) Texaco Service Station, located at 440 West Charter Way, (2) Chevron Service Station, located at 508 West Charter Way, (3) Transmission Store, located at 515 West Charter Way, and (4) Shell Service Station, located at 620 West Charter Way Residual hydrocarbons have been detected at the Texaco and Shell service stations and adjacent to the Transmission Store High concentrations of residual hydrocarbons were detected above the historical capillary fridge zone (25 feet bgs) at the Texaco Service Station and adjacent to the Transmission Store Dissolved hydrocarbons have been detected at the Texaco Service Station and at the Shell Service Station Free-product has been observed at the Texaco Service Station Based on the information supplied by SJCPHS, a subsurface investigation was conducted at the Chevron Service Station On May 12, 1995, EMCON observed the drilling of one angle boring (B-13) and two vertical soil borings and the installation of two vapor extraction wells (VW-8 and VW-9) SAC\N NPJOMOM8051460 31)S-95�=1