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`. FIELD AND LABORATORY PROCEDURES Exploratory Drilling and Soil Sampling The soil borings will be drilled using either 8-inch or 11-inch hollow-stem auger drilling equipment. Borings will be logged by a SECOR representative using the Unified Soil Classification System and standard geologic techniques. Soil samples for logging will be collected at 5-foot intervals using a either a California-modified split-spoon sampler (above groundwater), or a Simul-Probe° or Enviro- Core® sampler. All soil samples for chemical analysis will be retained in brass, stainless steel, or plastic liners, capped with Teflon squares and plastic end caps, and sealed in zip-lock bags. Discrete groundwater samples will be collected in selected intervals based on stratigraphy and field analytical data. The samples will be placed on ice for transport to the laboratory accompanied by chain-of- custody documentation. All down-hole drilling and sampling equipment will be steam-cleaned following the completion of the soil boring. Down-hole sampling equipment will be washed in a tri- sodium phosphate or alconox solution between samples. Well Completion The borings will be converted to groundwater monitoring wells by installing 2-inch diameter (MW-14, MW-16, MW-17), and 4-inch diameter (MW-15, MW-15D), flush-threaded, Schedule 40PVC casing with 0.020-inch factory-slotted screen. The screen intervals will be installed in each well as described in the proposed scope of work section of the work plan. An RMC2/12 sand pack, or equivalent, will be placed in the annular space across the entire screened interval, and will extend approximately 1 to 2 feet above the top of the screen for the well. A bentonite and Portland cement seal will extend from the sand pack to the ground surface. The boring logs will show well construction details. Well Development and Surveying The wells will be developed and sampled after completion. The development procedure for each well will consist of pumping or bailing water from the well until the water is visibly clear, the well goes dry, or until a maximum of ten casing volumes have been removed. After development, water levels are allowed to partially recover. Groundwater samples are then collected using a disposable Teflon bailer, placed into appropriate EPA-approved containers, labeled, placed on ice, and transported to the laboratory accompanied by chain-of-custody documentation. A California State Licensed Surveyor will survey the newly installed wells. The well casings will be surveyed to the nearest 0.01 feet in elevation to a known benchmark. 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.