COMPLIANCE INFO_1991-1997 - Laserfiche WebLink

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City of Stockton November 14, 1995 Sediments containing fresh groundwater are largely unconsolidated silts and sands which were derived from river channel, flood plain, and alluvial fan deposits of Pliocene to Recent age (Davis and others, 1959). First encountered groundwater in the vicinity of the site occurs under unconfined (water table) conditions at a depth of approximately 85 feet BSG. Regional groundwater flow is directed to the southeast, however, in the vicinity of the landfill groundwater flow is to the northeast. The northeast flow direction may be the result of groundwater extraction from wells located along Austin Road north of the landfill. 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 Monitoring Well Installation Twining proposes to drill a soil boring to a depth of 105 feet BSG using 7 -5/8 -inch diameter hollow -stem augers. 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 transported to the landfill where they will be incorporated into the soil used for daily cover. Soil disposal will be the responsibility of the client. The soil boring will be converted to a groundwater monitoring well by installing 2 -inch diameter schedule 40 polyvinyl chloride (PVC) well casing and 0.01 -Inch machine slotted well screen. Casing and well screen will be flush threaded. The screened section will extend from 80 feet BSG to 105 feet BSG. Lonestar #3 washed sand, or its equivalent, will be placed from the bottom of the boring to approximately 10 feet above the top of the machine slotted casing. Three to five feet 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 containing three to five percent bentonite. The well will be sealed with a PVC slip cap. Steel standpipes will be installed to approximately 2 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