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s ' 1444 MARIPOSA ROAD • WKA No 2307 02 ' December 4, 1992 Page 4 tgasoline using EPA method 8015/Purge d Trap and BTEX using EPA method 8020 Laboratory detection limits will be 0 5 mg/kg for TPH as gasoline and 0 005 mg/kg for BTEX. Samples will be ' selected for laboratory analysis based on conditions encountered during drilling and field screening. Subsequent to drilling, the soil borings will be sealed to the surface by pumping a slurry of Portland ' Cement and bentonite into the boring through a tremae pipe Soil generated during drilling activities will be placed on the existing soils stockpiles and covered with plastic Drilling equipment will be steam cleaned between borings, steam cleaning rinsate will be contained in the steam cleaning rack/collection ' system, transferred to sealed 55-gallon drums and stored on site If soil contamination appears to extend to the ground water surface, we would convert one of the soil ' borings to a ground water monitoring well The wells would be installed by drilling one of the soil borings to a depth of approximately 10 feet below the static ground water level The boring would then ' be converted into a ground water monitoring well using two-inch diameter, flush-jointed, Schedule 40 PVC casing, 0 02-inch slotted casing would be used for the screened interval Number 3 Lonestar sand would placed in the well annulus as a filter pack using the tremae method The filter pack would extend ' ! from the bottom of the screened interval to approximately two feet above the top of the screened interval A minimum two-foot thick bentonite seal would be placed in the well annulus above the filter pack A grout seal consisting of a Portland Cement and bentonite slurry would tremied into the well ' annulus above the bentonite seal The well would be completed with a locking well cap and a flush- mounted, traffic-rated well cover An as-built well diagram for the proposed well is shown on Plate 3. ' The well would be developed with a vented surge block and pumped until relatively free iof sediment and/or until stabilized pH, temperature and conductivity readings were attained The water purged ' during development would be placed in labeled 55-gallon drums stored on site After installation and development of the monitoring well, a water sample would be obtained from the ' well Prior to sampling, water level measurements in the well would be recorded with an electronic well sounder to the nearest 0 01 foot, and the well would be checked for the presence of free product using ' a clear bailer The well then would be purged of at Ieast three well volumes of water until stabilized pH, temperature and conductivity readings were attained, purge water would be stored in sealed 55- gallon drums as described above Subsequent to purging, a water sample would be obtained with a ' disposable bailer and decanted into 40-milliliter amber VOA vials containing hydrochloric acid as a preservative The bottles would be sealed with caps containing teflon septae 11 The water sample would be stored on ice and submitted under chain-of-custody to a California-certified laboratory for analysis of TPH and BTEX Laboratory detection limits would be 50 pg/L for TPH as o 000� ' WALLACE-KUHL Regcl d(weer &ASSOCIATES INC