ARCHIVED REPORTS XR0006103 - Laserfiche WebLink

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+i ! Of interest at this site are the two-groundwater zones that have been contaminated by gasoline hydrocarbons The two zones are A-Zone, a silty sand from 12 to 18 feet below the surface and B-Zone a clean sand from 21 to 27 feet below the surface A clay layer that forms an aquitared between the two zones The presence of the two groundwater zones A-Zone and B-Zone and the presence of the morntor wells MW1 through NW5 which are screened across both zones_ complicates the de-«atering of this site Of major concern is the location of hfW 1 in relation to RW 1 and RW I B With monitor wells completed across both zones, pumping from one zone will cause flow up or down the cross zone well from the non-pumped zone This necessitates pumping from both A- Zone and B-Zone even if you plan to de-water only A-Zone Because of the difficulties presented by the presence of MWI, MW2 and MW3 close proximity to the planned excavation, we plan to destroy MW 1 MW2 and MW3 prior to attempting to de- water the area to be excavated In order to de-water the area to be excavated «e plan to pump water from RW 1 A the Zone A recovery Well This water will be pumped with a down hole pump The pumping will be performed at a rate sufficient to de-water the upper ground water zone, estimated at 5 gpm The water will be treated by passing it through carbon prior to discharge to the sarutary sewer 13 PUMPING DURING EXCAVATION During excavation, a surface centrifugal pump will be used to maintain the water level The pump rate needed to do this has yet too be determined (pending the results of the pump test) Also the effects of the excavation widening the exposed surface of the water bearing zone is not yet luioxvii Currently we expect the rate to be approximately 10 gpm total The water will be treated by pumping it to a sediment drop out tank, prior to passing it through carbon for discharge to the sanitary sewer 2 SECTION C2, PRETREATMENT PRIOR TO DISCHARGE 21 TREATMENT SYSTEM The recovered groundwater shall be treated by passing through an activated carbon system prior to discharge to the sanitary system The system shall consist of a 55 gallon sediment dropout tank followed by four 55 gallon carbon canisters in series Drop-Out Tank size will need to be greatly increased for water pumped from the excavation while digging is in progress 2 PART C PUMPING PLAN 1875 COUNTRY CLUB BLVD