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ATTACHMENT A • FIELD•D LABORATORY PROCEDURES Chevron Service Station 20-0794, 4747 North West Lane, Stockton, CA CPT Borings and Soil and Groundwater Sampling The CPT soil borings will be advanced using a direct push cone penetrometer testing (CPT) rig to log soil stratigraphy. Immediately adjacent to each CPT borehole, a second direct-push borehole will be advanced to collect discrete soil and groundwater samples. Soil samples will be collected using an Envirocore sampler, or similar technology. Soil samples will be retained in plastic sleeves and capped with Teflon squares and plastic end caps. Groundwater samples will be collected using a hydropunch, or similar technology, by lowering a stainless steel or Teflon bailer into accumulated groundwater in the borehole, then retrieving and transferring the water into laboratory supplied containers. The soil and groundwater sample containers will be placed on ice for transport to the laboratory accompanied by chain-of-custody docu- mentation. Down-hole boring and sampling equipment will be steam-cleaned prior to and following the completion of each soil boring. Down-hole sampling equipment will be washed in a tri-sodium phosphate or AlconoxTM solution between samples. Organic Vapor Procedures Soil samples collected at 5-foot depth intervals during drilling will be analyzed in the field for ionizable organic compounds using a photo-ionization detector (PID) with a 10.2 eV lamp or a flame ionization detector (FID). The test procedure will involve measuring approximately 30 grams from an undisturbed soil sample, placing this subsample in a sealed container(either a zip-lock bag or a mason jar). The container will be warmed for approximately 20 minutes (in the sun), then the head-space within will be tested for total organic vapor, measured in parts per million as benzene (ppm; volume/volume). The instrument will be calibrated prior to drilling using a 100-ppm isobutylene standard (in air) and a sensitivity factor of 55, which relates the photo-ionization potential of benzene to that of isobutylene at 100 ppm. The results of the field testing will be noted on the boring logs. PID and FID readings are useful for indicating relative levels of contamination, but cannot be used to evaluate hydrocarbon levels with the confidence of laboratory analyses. Soil Sampling for Stockpiled Soil Soil samples will be collected by advancing a 2-inch diameter brass sample liner into the soil stockpile, after removing approximately 6-inches to 1-foot of surface material in the sample location. One composite sample will be collected per approximately 100 cubic yards of soil. Soil samples for chemical analysis will be retained in the brass liners, labeled, and capped with Teflon sheets and plastic end caps. The samples will then be sealed in zip-lock bags, placed on ice, and transported to the laboratory accompanied by the appropriate chain-of- custody documentation. Laboratory Procedures for Soil and Groundwater Samples Selected soil and groundwater samples will be analyzed for the presence of TPHg using modified EPA Method 8015, and benzene, toluene, ethylbenzene, xylenes (BTEX) and methyl tertiary butyl ether(MtBE)by EPA Method 8260.