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City of Stockton A68104 01A October 25, 1995 Page 3 Due to the relatively wet winter and spring of 1994-1995, the lawn area around the former UST location was very susceptible to damage by the drilling equipment Therefore filed work on this project was postponed until June 22, 1995 The following text summarizes the results of the investigative work performed consistent with the work plan 4.0 INVESTIGATIVE PROCEDURES ' This site characterization consisted of a field investigation, a laboratory testing program, and preparation of a technical report These activities are summarized in the following subsections Standard operating procedures (SOPS), relevant to the field and laboratory activities, are described in Appendix A Any exceptions which were made to the SOPs are explained in the appropriate following section(s) ' 4.1 Field Investigation The field investigation consisted of drilling soil borings, installing and developing a monitoring well, and collecting soil and groundwater samples for chemical analyses ' 4.1.1 Soil Boring and Soil Sam ling On June 22, 1995, Twining drilled four soil borings (B-1 through B-3, and MW-1) at the locations shown on Drawing 3 The purpose of soil boring B-1 was to assess the presence of PPCs beneath the former location of a fuel dispenser Soil boring B-1 was drilled with a hand auger to approximately 3 feet BSG and a soil sample was collected at the bottom of the boring The soil boring for MW-1 and soil borings B-2 and B-3 were drilled with a Central Mine Equipment Company 75 truck-mounted drill rig equipped with continuous-flight, hollow- stem augers The purpose of soil boring MW-1 was to assess the vertical extent of PPC migration and to install a monitoring well for groundwater assessment The soil boring for ' MW-1 was drilled to approximately 40 feet BSG Soil samples were collected in MW-1 at 5-foot intervals starting at 15 feet BSG The purpose of soil borings B-2 and B-3 was to assess the lateral extent of PPC migration in soil near the former UST location. Soil boring B-2 and B-3 were drilled to approximately 20 feet BSG and soil samples were collected at 5-foot intervals starting at 5 feet BSG Soil boring B-3 was drilled at an angle of approximately 32 degrees from vertical in a southwesterly direction to investigate soil conditions beneath the maintenance building ' Consistent with our SOPS, soil samples were observed in the field for visible staining, petroleum odor and field screened for volatile organic vapors using a photoionization detector (PID) consistent with our SOPs The results of the field screening and lithologic descriptions of the subsurface soils are recorded in the soil boring logs presented in Appendix B