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F` i Mr.Nuel Henderson,SJCEHD November 4,2005 Well Installation Work Plan ARCO Station 5469,Stockton,California Page 4 Task 2: Field Activities Task 2A: Soil Borings A licensed well driller will advance the soil borings using a truck mounted drill rig equipped with 10-inch diameter hollow stem augers. Each boring will be completed as a monitoring well, as described below. The initial 5 feet of each boring will be advanced with air knifing and vacuum equipment to reduce the possibility of damaging underground utilities. Soil samples will be collected at 5-foot intervals using a California-type, split- spoon sampler equipped with three pre-cleaned brass tubes. The ends of the bottom-most, intact tube from each sample interval will be lined with Teflon-rm sheets, capped, and sealed. Each sample will then be labeled, placed in a resealable plastic bag, and stored in an ice- chilled cooler. Strict chain-of-custody procedures will be followed from the time the samples are collected until the time the samples are relinquished to the laboratory. Soil contained in the remaining brass tubes will be screened for volatile organic compounds using a photoionization detector (PID). Stratus will record PID readings, soil types, and other pertinent geologic data on a borehole log. A minimum of three soil samples from each boring will be submitted for chemical analysis. Additional samples may be selected for chemical analysis based on soil type and field observations. Details regarding exploratory boring procedures are included in Appendix A. Task 2B: Monitoring Well Installation Groundwater monitoring wells MW-11 through MW-13 will be installed to a depth of approximately 53 feet bgs, using 4-inch diameter PVC casing and 20 feet of 0.02-inch diameter machine slotted casing, situated from approximately 33 to 53 feet bgs. A filter pack of LonestarTM #3 sand will be placed in the annular space around the well casing from the bottom of the well screen to approximately three feet above the top of the well screen. Approximately three feet of bentonite will be placed on top of the filter pack and hydrated with clean water to provide a transition seal for the well. Neat cement will be used to backfill the remaining annular space around the well casing. A watertight locking cap will be placed over the top of the well casing, and a traffic rated vault box will be installed around the top of the well. The actual well construction may be modified in the field based on conditions encountered at the time of the investigation. Task 2C: Waste Manaizement All drill cuttings and wastewater generated during the field activities will be contained in U.S. Department of Transportation-approved 55-gallon steel drums. The drums will be appropriately labeled and stored at the site pending proper disposal. A licensed contractor will transport the soil and wastewater to an appropriate facility for disposal. KABp-Arco for URS154691Work Plans\Arco5469-well install workplan-2005.doc 5TRATU5