COMPLIANCE INFO_1993-1994 - Laserfiche WebLink

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City of Stockton TL# 394-0027-02 March 10, 1994 Page 3 4.0 PROPOSED FIELD ACTIVITIES Proposed field activities are summarized in the following subsections. Standard operating procedures (SOPs) , relevant to the field activities, are described in Appendix A. 4. 1 Gas Probe Installation Twining proposes to drill 13 soil borings to a depth of 20 feet BSG using 6-5/8-inch diameter hollow-stem augers. The number of borings is based on the spacing of probes at approximately 1,000 feet along the perimeter of the landfill. Soil samples will be collected at five-foot intervals beginning at five feet BSG for lithologic purposes only. A Twining geologist will log the soils in accordance with the Unified Soil Classification System. Drill cuttings will be stored in California Department of Transportation (DOT)-approved 55-gallon drums. Soil disposal will be the responsibility of the client. The gas probes will be constructed of 1-inch diameter schedule 80 polyvinyl chloride (PVC) well casing and 0.02-inch machine slotted well screen. Casing and well screen will be flush threaded. Each gas probe will be screened from approximately 13 to 18 feet BSG. Rubber stoppers will be placed at the top of the screened section and at the top of the casing. Teflon04 tubing will extend through the rubber stoppers from approximately one foot below the bottom stopper to approximately one foot above the top stopper. Samples will be obtained through the Teflon TM tubing. Coarse-grained sand or pea gravel will be placed from the bottom of the boring to approximately two feet above the top of the machine slotted casing. Approximately one foot of bentonite pellets will be placed on top of the filter pack, and the remaining annular space will be filled with a sand-cement grout. The bentonite pellets will be hydrated prior to the placement of the grout. Steel standpipes will be installed to approximately 1 .5 feet above ground surface, secured in place with concrete, and the lid will be secured with a lock. Drilling and well installation activities will be supervised by a Twining geologist. The Twining geologist will be working under the direct supervision of a California registered geologist. Twining understands that the SJCEHD requires oversight of grouting activities and that no charge will be applied for one hour or less per well. Twining anticipates completing the grouting for well abandonment and installation within the specified time frame. 4.2 Soil Gas Sampling Methane levels in the gas probes will be measured using a methane calibrated meter following installation. The results will be logged and included in the report.