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City of Stockton July 18, 1997 A68108.01B Page 3 In a request for bid letter (RFB) dated February 8, 1996, the City of Stockton (City) requested a work plan for the project site to include four soil borings advanced by the direct push technique (soil probe) to depths of 30 feet BSG. In a letter dated March 21, 1996 the San Joaquin County Public Health Services (SJCPHS) suggested that soil borings be advanced to determine the vertical and horizontal extent of soil contamination. In addition, if soil contamination appears to extend to groundwater, the SJCPHS suggested that a groundwater sample be collected. The following sections outline the work performed to satisfy the request of the City and the suggestions of the SJCPHS. 4.0 INVESTIGATIVE PROCEDURES 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 laboratory activities, are described in Appendix A. Any specific deviations from the SOPs are stated in the following sections. 4.1 Work Plan and Permit Application Approval: The work scope herein described was s �— presented in Twinings work plan (A68106.03A) dated May 29, 1996 (Twining, 1996). The �. work plan was approved by the SJCPHS in their letter dated October 22 1996. An "Application for Well/Pump Permit" for the proposed test borings was submitted to the SJCPHS on August 14, 1996 and approved on November 1 1996. Copies of the e SJCPHS work plan approval letter and the approved permit application are attached in Appendix B. r 4.2 Field Investigation: The field investigation consisted of collecting sub-surface soil and groundwater samples for chemical analysis. 4.2.1 Soil Sampling Technique 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 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 documented on a field boring log consistent with the Unified Soil Classification System (USCS). The soil samples were field screened for evidence of volatile organic compounds (VOCs) and/or other contaminates. The field screening consisted of; visual observation for straining or free fluids, unusual odor, and head space analysis using