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excavation area nearly impossible ssible by acting as conduits to the estimated high transmissivity B zone ' Workplan Revision I The need to handle the pumped groundwater generated during excavating of contaminated soils will need to be addressed WEGE proposes that a wastewater discharge permit be obtained from the City of Stockton that would allow for one week of continuous pumping from R 1 A and the proposed excavation The following has been presented to the City of Stockton Municipal Utilities Department, see Appendix A -FUWING PLAN C1 Description- One week prior to excavation activities a 4 inch diameter Grundfos electrical submersible pump will be placed into groundwater recovery well RIA, 4 inch PVC 0 01 slot from 12 to 17 feet below the: surface Current top of groundwater is at 9 98 feet below top of well casing (January 15, 2002) RIA will be pumped at 10 gpm to lower the groundwater in the area to be excavated The excavation will be advanced to a depth where groundwater starts entering the excavation, but not deeper than 20 feet below the surface Once groundwater is observed entering the excavation, the excavator will dig a sump along the western edge of the excavation to the 20 foot depth and a dewatering point(s) will be installed into the sump (4 inch diameter 0 04 slot Sch 40 PVC with bottom plug) A 2 inch diameter suction hose attached to a gasoline centrifugal pump capable of pumping at 10 gpin will then be used to pump the water from the excavation to a Baker Tank (sediment control) From the Baker Tank the water will be pumped into two (in series) 180 lbs activated water carbon units prior to being metered and discharged to the sewer Pumping will continue until the excavation has been backfilled with 1/2 inch clean pea gravel to 7 feet below surface Geofabric will be placed ontop of the pea gravel prior to backfilling the remaining excavation with compacted clean road base Prior to resurfacing, all pumping points (i e groundwater recovery, vapor recovery, air sparging) risers will be connected and subsurface routed to the treatment compound Resurfacing will be hotpatch asphalt C2 ]Pretreatment- The pumped groundwater will be placed into a open top Baker Tank, (sediment removal), prior to discharge through 4 (in series) activated carbon canisters that each contain 180 pounds of activated carbon Prior to discharge to the sewer clean-out, the treated water will pass through a meter that accurately accounts the amount of treated water dumped to sewer C3 Pollutant removal efficiencies - The carbon treatment system is expected to maintain a greater than 90% efficiency in gasoline range hydrocarbon removal 4 Sanchez Rev WP 2-02