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160 Phase II Environmental Site Assessment Work Plan Heritage Square Page 3 3.0 SCOPE OF WORK The purpose of the site work is to investigate if a release of hydrocarbons from the tank on the north side �. of the Heritage Square building and associated fill piping under the building basement has occurred, and to investigate potential hydrocarbon contamination beneath the parking lot due to migration of contaminants from the UST located on the east side of the Women's Center building. The field work will include the drilling of approximately 13 small diameter boreholes adjacent to the tank on the north side of the Heritage Square building and approximately 12 small boreholes in the parking lot adjacent to the tank on the Women's Center property. The proposed boring locations are shown on Figure 3, Soil LM samples will be collected at approximately two feet below the bottom of each tank and at five-foot intervals thereafter to a depth of 10 feet below the deepest evidence of hydrocarbon contamination or 30 feet, whichever is greater. Two soil samples will be retained from each borehole for laboratory analyses. .L. Soil samples will also be collected from three hand auger borings beneath underground piping located under the Heritage Square building. LM Based on previous drilling at a nearby site, groundwater is anticipated at approximately 35 feet below grade. If field evidence from any one borehole at a respective tank indicates soil contamination to 25 feet or more, one borehole will be advanced to the groundwater surface in the downgradient direction from the respective tank and a groundwater sample collected. The groundwater gradient direction will be estimated based on groundwater monitoring data from adjacent sites. 160 3.1 SITE PREPARATION Condor will complete drilling permit applications and obtain the required permits from the San Joaquin County Public Health Service, Environmental Health Department (PHS/EHD) prior to the field work. if *.W necessary, Condor will complete an encroachment permit application and obtain the permit from the City of Stockton Public Works Department. Condor will schedule and coordinate all field activities through the property owner, PHS/EHD, and the City of Stockton as needed. The proposed boring locations will t. be marked with white paint and USA will be notified at least 72 hours in advance of the fieldwork to locate and identify underground utilities in and near the work area. However, because companies ' contacted by USA may not identify utilities past private property lines and into the site, it is the L responsibility of the property owner to identify site utilities. ` 3.2 GEOPROBE BOREHOLES rV The boreholes will be advanced using a Geoprobe® percussion hammer driven sampler equipped with a 1.75-inch O.D_, 4-foot long, core barrel, fitted with a clean, single use, polyethylene liner. A licensed C57 drilling contractor will drill the boreholes under the supervision of a Condor geologist. The soil L` samples will be screened for the presence of-organic vapors in the field with a photoionization detector (PID). The total number and location of boreholes drilled at each location may be adjusted based on field data collected during the drilling. Following completion of the sampling, the boreholes will be filled with +� neat cement containing 3-5% bentonite. The slurry will be tremied into the borehole to avoid bridging. 3.3 SOIL SAMPLING The soil retained inside each core barrel will be logged according to the Unified Soil Classification System. Geological logs will be prepared containing field observations including soil type, estimated moisture content, PID measurements, and the presence of staining or odor. Soil samples will be selected from the polyethylene liner at distinct changes in lithology and at intervals suggestive of soil i CONDOR