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r 6- City of Stockton �..� JUIY I$ .1997 A68107.0IB ;r, of the UST excavation detected TpH_Dncentration Page 3 concentration of 0.03 mg/kg and xylenes at concentration of 1,880 m f g/kg, ethylbenzene at L In a request for bid letter dated February 8, 1996, 1 mg/kg. work pian for the project site to include Four sil he Ci of Stockton technique (soil probe) to depths of 25 feet BSG. In addition, (City) requested a be extended to groundwater and a advanced to the direct push LA on, they requested that one boring letter dated March 21, 1996 the grab collected that a from the groundwater. In a determine the vertical and horizontal extent of soil contaminatioborings � following'�ced to , outline the work performed to satisfy the request of the City and the suggestios of the e 4.0 INVELMS TI ATIVE PR ED This soil and groundwater assessment consisted of: preparation of a work plan and appropriate permit applications, a field investigation, a laboratory testing program, and preparation of a summary report. Standard operating procedures (SOPs), relevant to the field and Iaboratory activities, are described in Appendix A. Any specific deviations from the SOPS are stated in the following sections. 4.1 Work Pla RARdZemft : The work scope herein described was presented in Twining's work plan (A68107.07A) dated May 29, 1996 ('Twining, 1996). The work plan was approved by the SJCPHS in their letter dated October 11, 1996. An • "Application for Well/Pump Permit"was submitted to the SJCPHS on August 14, 1996 and approved on November 1, 1996. Copies of the SJCPHS work plan approval and the approved permit application are attached in Appendix B. 4.2 Field Investigation: The field investigation consisted of collecting sub-surface soil and groundwater samples for chemical analysis. 4.2.1 &M SAM2 ins Technigme and Locations: Subsurface soil samples were collected using a hydraulically-powered, soil probing machine that uses static force and percussion to advance small diameter sampling tools into subsurface soil for collecting soil cores. A sampling tool (bore sampler)was attached to the leading end of a probe rod and driven into do the subsurface using the machine. The sampling tool collected a continuous soil sample as it was advanced. The sampler advanced approximately 48 inches and then was recovered from the bore hole. The bore sample (soil sample) was extracted from the sampler. The soil sample was contained within a 2-inch diameter sampler liner of clear plastic. The soil samples were examined for the purpose of preparing lithologic logs. Soil descriptions were logged on a field boring log consistent with the Unified Soil Classification System (USCS). The soil samples were field screened for evidence of volatile organic v