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-1� I The excavation pit recharge water (since.the pit will be advanced below groundwater) will be properly treated and disposed. One of two possible approaches may be used: the water will be sent through a carbon filtration system, to a storage tank and tested to ascertain that contaminants have been removed. The water would then be discharged into the sanitary sewer with the approval of City of Tracy Public Works Department. Alternatively, the water may be pumped by a licensed hazardous waste hauler and taken directly to a treatment facility. The pit will be pumped out one time (one pit volume of groundwater). Field Activities Exploratory Soil Boring and Well Construction One exploratory soil boring will be advanced to shallow occurring groundwater for monitoring well replacement installation (see Figure 1). The boring will be drilled with a hollowstem flight auger drill rig under approved permits of the PHS-EHD. The boring will be sampled to collect lithologic data, for aquifer contact identification and screen placement. The drilling and sampling will.be done using the attached Wright soil and groundwater sampling protocols. All drilling and lithologic logging. will be done under the supervision of a certified engineering geologist, using the Unified Soil Classification System and geologic observations. k Replacement. Monitoring Well Installation One monitoring well will be installed using the attached Wright Protocol. The well will be cased will Sch. 40 PVC casing, threaded together; glues will not be used. The slotted interval will be a 0.020 inch slot and the annular space around the slots will be backfilled will a 2/12 size sand. Previous experience has shown this to be a reliable well design in fine grained and/or stratified depositional environments. Final well design will be modified to the site specific conditions encountered in the borehole during drilling. Once the aquifer strata has been defined, the casing will be lowered to the bottom of the borehole, leaving a slotted interval above the .occurrence of groundwater to observe for floating product. The sand pack will be placed to a point about two feet above the top of the slots. A bentonite seal will be placed atop the sand pack, and a cement grout seal placed atop the bentonite using a tremie line, filling from the bottom to top of the borehole. A traffic rated well head access box and security device will complete the well. Well Head Survey All wells will be surveyed to mean sea level using the site datum. This will allow accurate measurements and groundwater gradient to be calculated. i Monitoring Sampling Well Sam lin and Development The monitoring well will be developed to remove the drilling muck, grade the sand pack and provide a more complete hydraulic connection to the aquifer. The well volume will be calculated and a number of those columns will be removed until the water becomes clear and the amount of sand pumped is minimal. The well will be allowed to recover for at least 72 hours prior to sampling. A log of the development � will be kept for each well.