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ATTACHMENT A FIELD PROCEDURES (CONTINUED) i Chevron Service Station 9-2033, 508 West Charter Way, Stockton, California cement from the bentonite seal to ground surface The well casings will be topped with a locking cap The wellheads will be contained in watertight well boxes, either traffic rated and flush mounted or in a "stove-pipe" arrangement The boring logs will show well construction details The wells will be developed after completion by pumping or bailing water from the wells until the water is visibly clear, the wells go dry, or until a maximum of ten casing volumes have been removed After development, water levels will be allowed to partially recover Groundwater samples will then be collected using a disposable Teflon bailer, placed into appropriate EPA- approved containers, labeled, placed on ice, and transported to a California State Certified laboratory accompanied by chain-of-custody documentation The well casings will be surveyed to the nearest 0 01 feet in elevation to a known benchmark Organic Vapor Procedures Soil samples collected continuously 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 sub-sample in a sealed container (either a zip-lock bag or a mason far) 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 (ppmv, 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 lsobutylene 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 3