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Ms. Lori Duncan Page 3 of 6 Based on historical groundwater monitoring data within close proximity to the site, current depth to water is expected to be approximately 28 to 30 feet below grade and is expected to flow in a northeasterly direction (San Joaquin County PHS/EHD Corresp, 9/6/00). Historical data from San Joaquin County Flood Control and Water Conservation District suggests that water levels are currently at or near a historical high. Historical low water levels are expected to have been between 45 and 50 feet bgs. 2.3 Investigations Undertaken In accordance with the approved workplan dated July 20, 2000, a total of five soil borings were advanced at the site to investigate the lateral and vertical extent of residual soil contamination, as well as the potential impact to groundwater. Boring SB 1 was located in the former UST excavation, and borings SB2 through SB5 were located around the perimeter of the UST excavation (Figure 2). The borings were advanced to depths ranging from 16.5 to 17 feet bgs where refusal was met due to a hard pan formation. 3.0 INVESTIGATIVE PROCEDURES On September 11, 2000, Fisch advanced the borings under the supervision of field geologist Sean Garvey, and project manager Greg Stahl, a California Registered Geologist. Ms. Lori Duncan of San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) conducted the site inspection and observed field activities. Fisch utilized a truck mounted Geoprobe 5400 direct push rig to advance the borings and collect soil samples. Soil samples were collected at 5-foot intervals using a 1 3/4 -inch diameter by 24-inch long core sampler. The sampler was lined with clear acetate sleeves, affording soil identification and subjective evaluation for contamination. A flame ionization detector (FID) was used to monitor the presence of volatile organic compounds in the soil. Soil samples from the borings were sealed, labeled, and immediately placed in an iced cooler for transport to Argon, a state- certified analytical laboratory. Soil samples were selected based on observations and field screening results. Due to the presence of a hardpan formation extending from approximately 15 bgs to unknown depths, groundwater samples were unable to be collected. Borings SB2, SB4 and SB5 were advanced to a depth of approximately 16.5 feet bgs. Borings SB 1 and S133 were advanced to a depth of approximately 17 feet bgs. Refusal was encountered in all borings due to a hardpan formation. The completed borings were backfilled to the ground surface with neat cement grout. No soil cuttings were generated. All down-hole drilling and sampling equipment was decontaminated by washing with a laboratory grade detergent and rinsing with water. Rinsate collected from decontamination procedures was disposed of via evaporation on the asphalt/concrete surface within the confines of the investigation area. Nsautolreports\summary_WP.doc