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Stantec <br /> Addendum to Interim Remediation Action Plan <br /> Former ARCO Service Station No. 443 <br /> September 10,2008 <br /> and hydrated. The remainder of the annular space will be filled with cement and/or grout from <br /> the top of the bentonite seal to within 12 inches of the surface. The well will be secured with a <br /> locking well cap and completed with a watertight traffic-rated well box installed at grade. The <br /> well construction diagram for MW-8 is presented as Figure 1 <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. A continuous core will be collected from MW-8 <br /> in two ft long samples beginning at a depth of 100 feet bgs. The soil samples selected for <br /> chemical analyses will be based on visual observations and PID measurements with a minimum <br /> of two soil samples analyzed from each boring. The selected soil samples will be placed on ice <br /> in an insulated cooler until relinquished, under documented chain-of-custody control, to a <br /> certified analytical laboratory. Selected soil samples will be analyzed for gasoline range <br /> organics by Environmental Protection Agency(EPA) Method 8015B(M) and BTEX, MTBE, TBA, <br /> di-isopropyl ether, ethyl tert-butyl ether, TAME, ethanol, 1,2-dichloroethane, and 1,2- <br /> dibromoethane by EPA Method 8260B. <br /> 2. Volume and frequency of groundwater extraction events. <br /> A 3,000 to 5,000-gallon capacity vacuum truck will extract water from wells MW-1S, MW-2S, and <br /> MW-1D. An initial goal of 1,000 gallons of water extracted per well will be attempted. <br /> Dependant upon the yield of each individual well, extraction goals may be changed in future <br /> events. Groundwater extraction events will be performed monthly pending regulatory approval <br /> and continue for an initial period of six months. Monthly status reports will be submitted to the <br /> regulator prior to the next scheduled event. Fourth quarter 2008 monitoring and sampling will <br /> be moved up from December to November to evaluate the effectiveness of GWE. <br /> 443 IRAP Addendum.doc 2 <br />