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. Starrtec CLOSURE REPORT CALTRANS STOCKTON SHOP 10 Closure Sampling December 2,2009 2.4 Closure Sampling 2.1 CONFIRMATION BORINGS Following final system shutdown, Stantec recommended two confirmation borings be drilled in the source area, three soil vapor wells be installed, and a soil vapor study conducted. A work plan was prepared and submitted to the SJCEHD in September 2009. Soil boring and soil vapor sample locations are shown in Figure 2. A Sensitive Receptor Survey was also proposed to investigate any sensitive receptors within a 2,000 foot radius of the Site property boundary. The SJCEHD approved the work plan in a letter dated September 17, 2009. Two confirmation soil borings (CB-1 and CB-2)were advanced at the Site on October 8, 2009. These borings were advanced using direct-push Geoprobe®technology to a maximum depth of 50-ft-bgs. Use of direct-push drilling minimized the soil cuttings and costs of subsequent disposal. Confirmation soil boring logs were completed and are included in Appendix A. Soil samples were collected every 5 feet and screened for volatile organic compounds(VOCs)using a photoionization detector(PID). PiD levels ranged from 1.1 to 8.8 parts per million by volume(ppmv)in boring CB-1 and from 1.7 to 12.2 ppmv in boring CB-2. A total of four soil samples were submitted for analysis from each boring at depths of 20, 30, and 40 ft-bgs and at a depth where the PID showed elevated VOCs (at 35 ft-bgs in boring CB-1 and at 25 ft-bgs in boring CB-2). The collected soil samples were submitted to Agriculture Priority Pollutants Laboratories(APPL), Clovis, California under chain-of- custody procedures for analysis of TPHg and TPHd by modified U.S. Environmental Protection Agency(EPA) Method 8015M,and BTEX and fuel oxygenates (FOCs)by EPA Method 82606. Soil results indicated from 3.4 to 44 mg/kg TPHg was reported at depths ranging from of 20 to 40 ft-bgs in boring CB-1. Soil samples collected from boring CB-2 did not contain detectable levels of TPHg. Soil samples also contained from 43 to 1,100 mg/kg TPHd at depths of 20 to 40 ft-bgs in boring CB-1 and from 9.1 to 10 mg/kg at depths of 30 and 40 feet in boring CB-2. Laboratory reports indicated that diesel results were made up of mainly lower boiling compounds, which in general are less mobile and less volatile. BTEX and FOCs were reported at very low levels in two soil samples, CB-1-20 and CB-1- 35. Soil results are summarized in Table 4. Following collection of soil samples and advancement to the total depth of 50 ft-bgs, both locations were grouted to surface using a tremmie pipe and the surface was finished to match existing asphalt. A composite soil sample was collected from the soil cuttings and submitted for analysis of total lead,TPHg, TPHd, BTEX, and FOCs. Soil sample results for the soil cuttings analysis are included in Appendix C. All soil cuttings and drilling debris were stored in a 55-gallon drum onsite pending analytical results and will be disposed offsite according to local, state, and federal regulations. js iaprojects4caluanslshop 10ti MrJosurmfinal dosure report6closure rpt_fnl_doc 2-1