COMPLIANCE INFO_1993-1994 - Laserfiche WebLink

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City of Stockton TL 394-0027-02 March 10, 1994 Page 8 A-2 Decontamination: Decontamination procedures will be implemented to reduce the potential for cross-contamination between soil borings . Before, during, and following drilling operations, the augers and associated drilling and sampling equipment will be thoroughly cleaned using a high pressure hot water (steam) washer. The hot water washer has a pressure of approximately 1,200 pounds per square inch and a water temperature of approximately 100 degrees Centigrade ( OC) . The sampler and brass sleeves will be washed in a Alconox* detergent solution, rinsed with clean tap water, and air-dried prior to initial use and between each sampling event. The augers will be steam cleaned prior to the drilling of each soil boring. Prior to construction of monitoring wells, all casings will be cleaned in the same manner as the drilling equipment. A-3 Soil Gas Probe Installation: Twining is a C-57 licensed water well drilling contractor (Contractor's License No. 506159) . The soil gas probes will be installed under the direction of a California-registered geologist or -certified professional engineer. Soil borings for gas probes will be drilled and sampled according to Twining's "Standard Operating Procedures for Drilling and Soil Sampling" . Equipment used for drilling, sampling, and constructing wells, and well construction materials will be thoroughly cleaned according to Twining's "Standard Operating Procedures for Equipment Decontamination" . Soil gas probes will be constructed of Schedule 80 polyvinyl chloride (PVC) casing. Screen will be machine-slotted. Teflon TM tubing will extend from approximately one foot below the bottom stopper to approximately one foot above the top stopper for sample collection. Casing and well screen specifications may depend upon project objectives, site conditions, and project budgets. The well screen and casing sections will be joined by factory-made flush- threaded connections. The well filter pack material will consist of appropriately-sized pre-washed sand or pea gravel . The filter material will be placed in the annulus between the boring wall, from the bottom of the boring to approximately 2 feet above the top of the screen. Approximately one foot of bentonite will be placed on top of the sand pack. The bentonite may consist of 1/4- or 1/2-inch pellets, or may be in the form of a slurry. If pellets are used, they will be hydrated prior to grouting the well, by adding at least one gallon of water for every bucket of pellets. The thickness of the