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n FIELD INVESTIGATION To investigate the extent of residual soil contamination at the site, a total of six soil borings were advanced to depths ranging from approximately 16 to 31 feet below ground surface (bgs). All field activities were performed in accordance with Smith Technology's Workplan for Subsurface Investigation at 112 East Harding Way, Stockton, California, dated July 11, 1997. This workplan was approved by San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) on July 21, 1997. Soil Borings, Soil Sample Collection On July 24, 1997, a Smith Technology geologist supervised the advancement of six soil borings ranging in depth from 16 to 31 feet bgs. A site plan showing soil boring locations is included as Figure 2. Fisch Environmental, California Licensee C57 683865, advanced the borings using a truck mounted Geoprobe® narrow diameter rig employing direct push technology. Soil samples were described according to the Unified Soil Classification System. Descriptions of soil types encountered and sample collection intervals are presented on boring logs in Attachment 1. Soil samples were collected at five-foot intervals in acetate sampling tubes beginning at four feet below the ground surface. Each soil sample was field screened with a Photoionization Detector (PID) for the presence of volatile organic compounds. Sample tubes were immediately sealed at each end using Teflon tape and plastic end caps, labeled, and placed on ice pending laboratory analysis. Subsequent to sample collection, the soil borings were grouted to the surface with a neat cement grout. Selected soil samples were kept on ice and delivered under chain-of-custody documentation to State-certified NEI/GTEL Environmental Laboratories, Inc. for chemical analysis. Based on field observations (i.e. soil types and conditions, odor, discoloration) and discussions with facility personnel on site at the time of drilling, soil borings SB3, SB5 and S136 were placed in close proximity to the former UST pit location. Additionally, SB2 was positioned at the location of the former UST fuel dispenser. Borings SBI and S112 were placed within the excavated area of the former tanks. No obvious petroleum hydrocarbons were observed during field activities in the perimeter borings S132, SB3, SB5, and SB6. PID readings of collected soil samples did not exceed background levels of approximately 0 to 2 parts per million (ppm). However, obvious petroleum odor and elevated PID measurements were noted in soil samples collected from SBI and SB4 at depths ranging from 10 to 20 feet bgs and at 10 to 15 feet bgs, respectively. No obvious petroleum odors or elevated PID readings were noted in SBI at 30 feet bgs or S134 at 20 feet bgs, the deepest samples collected in the respective borings. An attempt was made to further advance the Geoprobe unit in several of the borings (including SB 1 and SB4), however probe refusal was encountered at depths ranging from 16 to 31 feet bgs due to the hardness of the formation. • w:1977361reportslsum.doc 2 •