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ATTACHMENT A v FIELD AND LABORATORY PROCEDURES Chevron Service Station 20-1761, 1103 South Main Street, Manteca, CA zip-lock bag or a mason jar). The container was warmed for approximately 20 minutes (in the sun), then the head-space within was tested for total organic vapor, measured in parts per million as benzene (ppm; volume/volume). The instrument was calibrated prior to drilling using a 100-ppm isobutylene standard (its 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 were 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 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 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. Laboratory Procedures for Soil and Groundwater Samples Selected soil and groundwater samples were analyzed for the presence of total petroleum hydrocarbons as gasoline (TPHg) using modified EPA Method 8015, benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl tertiary butyl ether (MtBE) by EPA Method 8260. Soil Cuttings and Rinsate Water Soil cuttings generated during drilling operations were temporarily stored onsite and covered with plastic sheeting pending characterization and disposal. Soil cuttings were then removed by Chevron's disposal contractor to an appropriate disposal facility. Water generated during steam cleaning and well development was temporarily stored in DOT-approved 55-gallon drums pending transport by Chevron's disposal contractor to an appropriate disposal or treatment facility. Soil cuttings and rinsate water drums were temporarily stored onsite for approximately 4 to 8 weeks.