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Stockton Unified Schooi District ' Geological and Environmental Hazards Assessment CSU-Stanislaus,Stockton Campus School Site Page 9 contributed to site soil and groundwater contamination. TK-I I was located in close proximity to TK-10 with a pump island located in between the two USTs. The San Joaquin County Environmental Health Department(SJCEHD) requested the_submittal of a work plan to investigate the lateral and vertical extent of contamination at the site. At the request of CSUS, Condor subsequently prepared and submitted the Work Plan for Soil and Groundwater Sampling by Direct Push (Geoprobe), dated June 21, 2000,which was subsequently approved by the SJCEHD. On December 28 and 29 2000, Condor conducted a limited soil and groundwater investigation, including 'the installation of five direct push borings at the site. Condor prepared the Preliminary Investigation and ;Evaluation Report (PIER), dated- February 7, 2001, describing the results of the work. Laboratory analytical results of the soil and groundwater samples and field observations indicated that petroleum hydrocarbons were present in site soil and groundwater down to the approximate: total depth of the investigation (4I feet below grade). In the PIER, Condor recommended additional soil and groundwater investigation. -Condor prepared the Work Plan -Additional Soil and Groundwater Investigation, dated October S, 2001 at the request of CSUS. The proposed work included the installation of direct push borings and monitor wells. The proposed work also included conducting a sensitive receptor survey (SRS)'to identify potential sensitive receptors within a 2,000-foot radius of the site. The direct push borings were to include cone penetrometer(CPT) borings to begin evaluation of deeper subsurface conditions (vertical investigation). The additional soil and groundwater investigation activities were conducted between`November 19 and December']8, 2001. The lateral and vertical extent of petroleum hydrocarbon contamination at the site was further investigated by the advancement of four cone penetrometer (CPT) borings and four direct push borings, and the installation, development, and sampling of three shallow groundwater monitor wells. The above referenced SRS was also conducted. Results of the work were described in Condor's Additional Soil and Groundwater°Investigation and Monitor Well Installation Report, dated January 11, 2002. Laboratory analytical results of soil and groundwater samples indicated that soil below approximately 56 feet below ground surface (bgs) was not impacted by petroleum hydrocarbons at or above the laboratory reported detection limits. Groundwater was impacted with petroleum hydrocarbon constituents, however, to the total depth of the investigation (approximately 81 feet bgs). The lateral and vertical extent of groundwater contamination at the site, therefore, was not fully evaluated and Condor indicated that further groundwater investigation would be necessary. Water table measurements from the three newly installed monitor wells:indicated that the Ell water table was approximately 37 feet bgs and that the.groundwatergradient was toward the east. Soil sample analytical results, groundwater sample analytical results and the groundwater gradient are shown in Figures 3, 4 and 5, Appendix E, respectively. The estimated extent of soil impacted by petroleum hydrocarbons at the site is shown in cross-section Uin `Figure 7, Appendix E and indicates that an �-t approximately 3,000 cubic yards of hydrocarbon impacted soil remains in place at the site. ! The results of the SRS indicated the presence of one intact air conditioning well approximately 1,500 feet north of the site,one irrigation wel l approximately 1,900 feet northeast of the site, and ane municipal well approximately 1,400 feet south of the site within the study area. The municipal well was not in use at the Itime of the survey. The location of two additional wells within the study area could not be identified. No surface water bodies were identified within. the search radius. One school, four childcare facilities, and two senior care facilities were identified within the search radius. ` it CONDOR