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feasibility Study—Enhancement of Existing Remediation Activities 8200 N. Highway 99, Stockton, CA Page 8 of 10 Selection of soil samples for laboratory analysis will be based on field evidence of petroleum hydrocarbon contamination such as discoloration, odors, and photo ionization detector (PID) readings, as well as lithologic changes. if no evidence of contamination is noted in the field, samples from the capillary fringe and the bottom of the boring, at minimum, will be submitted for analysis. Up to five (5) selected soil samples will be submitted for laboratory analysis. Soil samples will be temporarily stored in an ice chest cooled to approximately 4° C, and will be delivered under chain of custody protocol to a California Certified Laboratory. Soil samples will be analyzed for total petroleum hydrocarbons as gasoline (TPHg) using EPA Method 8015M, benzene, toluene, ethylbenzene, and xylenes (BTEX)using EPA 8021B, and gasoline oxygenate additives using EPA Method 8260B. To complete the well, 4-inch diameter Schedule 40 PVC casing, with appropriately spaced centralizers, will be set from 65-feet bgs to the surface. 0.020-inch slotted screen will complete the well from 65- to 95-feet bgs. A filter pack consisting of#3 sand will be emplaced from total depth to approximately two feet above the top of the screened interval. The remaining annulus will be completed with four feet of hydrated bentonite pellets overlain by neat cement grout to the ground surface. All annular materials will be emplaced with a tremmie system. At the surface, the well will be fitted with a locking cap and above ground monument type well box. Soil cuttings generated from well installation activities will be profiled and stored in properly labeled DOT approved steel drums until disposal can be arranged. 4.2 Well Survey and Development After the installation of the groundwater extraction well the casing elevation will be surveyed by a licensed land surveyor in accordance with the requirements outlined in A132886. The coordinates and elevation will be uploaded to GeoTracker database upon receipt from the land surveyor. The newly installed well will be developed no sooner that 48 hours after installation. The well will be developed by pumping and surging until the turbidity of the pumped groundwater is visibly reduced. Groundwater samples will be collected after physical parameters (temperature, pH, and electrical conductivity) have stabilized and water levels have recovered to near their pre-purged levels. One water sample will be stored in an ice chest cooled to approximately 4° C and delivered under chain of custody protocol to a California certified laboratory for analysis. Groundwater samples will be analyzed for TPHg by EPA Method 8015M, BTEX by EPA Method 8021B, and gasoline oxygenate additives by EPA Method 8260B. Water generated from well development and sampling will be filtered, to remove sediments, and run through the groundwater treatment system. Silt filtered from the water will be stored in properly labeled DOT approved steel drums until disposal can be arranged. G:%GROUNDZEITULEBURGIReports10709 FS rein enhanrcment.doc