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ATTACHMI'N'll B FIELD ANI) LABORATORY PROCEDURES (CONTINUED) Chevion 9-3232, 8660 1 owei Saciamento Road, Stockton Cfk Soil samples foi logging will be callc:Lted continuously from the deep borings and in five- foot intervals for the single shallow well using a California-modified split-spoon sampler The sampler will be driven a maximum of 18 inches using a 140-pound hammer with a 30- inch drop Soil samples for chemical analysis will be retained in brass liners, capped with Teflon squares and plastic end caps, and sealed in clean zip-lock bags The samples will be placed on ice for transport to the laboratory accompanied by chain-of-custody docu- mentation Down-hole drilling 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 alconox solution between samples Groundwater Monitoring Well Installation The borings will be converted to a groundwater monitoring well by installing 2-inch diameter, flush-threaded, Schedule 40 PVC casing with 0 020-inch factory-slotted screen Approximately 20 feet of screen will be placed in the bottom of each shallow boring, and 5 to 10 feet of screen will be placed in the bottom of the deep borings A grade of sand appropriate to the screen size will be placed in the annular space across the entire screened interval, and will extend approximately 2 feet above the top of the screen for each well A bentonite seal will extend two to three feet above the sand pack The monitonng wells will be completed with neat cement from the bentonite seal to ground surface The well casings will be topped with a locking cap. The well heads 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 each well until the water is visibly clear, the wells go dry, or until a maximum of ten casing volumes have been removed Organic vapor Procedures Soil samples collected either continuously or at 5-foot depth intervals during drilling will be analyzed in the field for ionizable organic compounds using a photo-ionization detector (FID) 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 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 (ppm, volume/volume) The instrument will be calibrated prior to dnlling 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