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ATTACHMENT A • FIELD AND LABORATORY PROCEDURES Chevron Service Station 20-0794, 4747 North West Lane, Stockton, CA Health and Safety As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120), and by California Occupational Health and Safety Administration (Cal-OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (CCR Title 8, Section 5192), SECOR will prepare a Site-Specific Health and Safety Plan prior to the commencement of fieldwork. The Site-Specific Health and Safety Plan will be reviewed by the field staff and contractors before beginning field operations at the site. Exploratory Drilling The soil borings will be drilled using an 8-inch hollow-stem auger drilling equipment to approximately 60 feet bgs. The 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 depth intervals 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 documentation. 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. Approxi- mately 15 feet of screen will be placed in the bottom of each boring. 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 feet above the sand pack. The monitoring 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. Slug Testing The slug test consists of quickly raising (slug in) or lowering (slug out) the water level in a well from equilibrium and measuring the subsequent rate of rise or fall, respectively. Slug in and slug out tests will be performed on each well using a slug of know volume to derive values for transmissivity(T) and hydraulic conductivity(K).