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Stattec <br /> Interim Remedial Action Plan <br /> Former ARCO Service Station No. 443 <br /> July 10, 2008 <br /> drilling equipment will be decontaminated with high pressure steam following the completion of <br /> each soil boring. Down-hole sampling equipment will be decontaminated between samples <br /> using an Alconox detergent solution and a tap water rinse. <br /> The brass or steel sample tubes will be removed from the split-spoon sampler and retained for <br /> possible laboratory analyses. One sample tube from each five-foot interval will be sealed on <br /> each end with Teflon tape and plastic end caps. The soil samples selected for chemical <br /> analyses will be based on visual observations and PID measurements with a minimum of two <br /> soil samples analyzed from each boring. The selected soil samples will be placed on ice in an <br /> insulated cooler until relinquished, under documented chain-of-custody control, to a certified <br /> analytical laboratory. Selected soil samples will be analyzed for GRO by Environmental <br /> Protection Agency (EPA) Method 8015B(M) and BTEX, MTBE, TBA, di-isopropyl ether, ethyl <br /> tert-butyl ether, TAME, ethanol, 1,2-dichloroethane, and 1,2-dibromoethane by EPA Method <br /> 8260B. Historical soil and groundwater analytical data are summarized in Tables 1 and 2, <br /> respectively. <br /> At the terminal depth of each boring, a well will be installed within the annulus of the auger. <br /> Each well will be constructed using two-inch diameter, flush-threaded, schedule 40 poly vinyl <br /> chloride (PVC) well casing and 0.020-inch factory-slotted well screen. The wells will be <br /> screened from approximately 40-60 ft bgs for MW-5 through MW-7, 105-120 ft bgs for MW-8; <br /> however, the final total depth and screen interval will be determined in the field based upon z ios 12� <br /> observed conditions. The total depth of the well and screened interval will be placed such that l ^�1 <br /> the potentiometric surface is within the screened interval. A sand filter pack will be placed in the f W7. <br /> annular space surrounding the entire screened interval and will extend approximately two ft <br /> above the top of the screened interval. A bentonite annular seal will be placed above the filter <br /> pack and hydrated. The remainder of the annular space will be filled with cement and/or grout <br /> from the top of the bentonite seal to within 12 inches of the surface. The well will be secured <br /> with a locking well cap, and completed with a watertight traffic-rated well box installed at grade. <br /> Soil boring and well construction details are summarized in Table 3. <br /> 2.4 Well Development <br /> After a minimum of 48 hours following well construction, the newly constructed monitoring wells <br /> will be developed to clean the filter pack and stabilize the aquifer materials around the slotted <br /> well casings. Development will be accomplished by alternately surging each well with a vented <br /> surge block followed by bailing to remove accumulated sediment. Final purging will be <br /> performed with either a submersible pump or bailer, and pH, temperature, and conductivity will <br /> be measured at regular intervals during purging. Development will be considered complete <br /> when either 1) eight well volumes have been removed and physical-chemical parameter trends <br /> have stabilized over three consecutive measurements (<0.05 pH, 3% conductivity, and 10% <br /> temperature), 2) ten well volumes have been removed, or 3) until the well has been purged dry <br /> (if the well does not sustain flow or is slow to recover). <br /> 2.5 Surveying <br /> Upon completion of well installation activities, a licensed surveyor will locate all wells within the <br /> California state plane coordinate system, within 1/1000 vertical control, and latitude-longitude <br /> (degree, minutes, seconds) to meet the State of California Water Resources Control Board <br /> 4 <br /> 443 IRAP.doc <br />