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ATTACHMENT C FIELD PROCEDURES Chevron Service Station. 9-1452, 334 East Main Street, Ripon, California sun), then the head-space within was tested for total organic vapor, measured in parts per million as benzene (ppmv; volume/volume). The instrument was 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 was 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 were collected by advancing a 2-inch diameter stainless steel sample liner into the soil stockpile, after removing approximately 6-inches to 1-foot of surface material in the sample location. One composite of four soil samples was collected per approximately 100 cubic yards of soil. Soil samples for chemical analysis were retained in the brass liners, labeled, and capped with Teflon sheets and plastic end caps. The samples were then sealed in zip-lock bags, placed on ice, and transported to the laboratory accompanied by the appropriate chain-of-custody documentation. PROPOSED CPT INVESTIGATION AND WELL INSTALLATION CPT Borings 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 groundwater samples. 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 groundwater sample containers will be placed on ice for transport to the laboratory accompanied by chain-of-custody documentation. Down-hole boring and sampling equipment will be steam-cleaned prior to and following the completion of the soil boring. Down-hole sampling equipment will be washed in a tri-sodium phosphate or AlconoxTM solution between samples. Laboratory Procedures Groundwater samples collected will be analyzed for the presence of TPHg and methanol by EPA Method 8015, BTEX, MtBE, EtBE, DIPE, TAME, TBA, EDB, 1,2 DCA, and ethanol by EPA Method 8260B.