ARCHIVED REPORTS XR0003043 - Laserfiche WebLink

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. Groundwater Monitoring Well Installation and Sampling Groundwater monitoring wells and oxygen diffusion/iso-gen remedial wells will be constructed by installing either 2 -inch or 4 -inch diameter, flush -threaded, Schedule 40 PVC casing with 0.020 -inch factory -slotted screen. Boring EX -3 will be converted to a groundwater extraction well by installing 6 -inch stainless steel casing with 0.020 -inch slotted screen. An RMC 2112 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. 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. The newly installed wells will be surveyed by a California State Licensed Surveyor. The well casings will be surveyed to the nearest 0.01 feet in elevation to a known benchmark for evaluation of measured water levels. 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 flame -ionization detector (FID) or a photo - ionization detector (PID) with a 10.2 eV lamp. The test procedure will involve measuring approximately 30 grams from an undisturbed soil sample, placing this subsample in a ziplock type bag or in a clean glass jar, and sealing the jar with aluminum foil secured under a ring - type threaded lid. The container will be warmed for approximately 20 minutes (in the sun), then the head -space within the container 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 r Laboratory Procedures Selected soil and groundwater samples collected will be analyzed for the presence of total petroleum hydrocarbons calculated as gasoline (TPHg), toluene ethYlbenzene xylenes i (BTEX compounds), and methyl tertiary butyl ether (MtBE), ethylene dibromide (EDB), 1,2- dichloroethane (1,2 -DCA), tertiary butyl alcohol (TBA), di -isopropyl ether (DIPE), ethyl 9-5775WP100900.doc October 10, 2000