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Stantec <br /> Addendum to Interim Remediation Action Plan <br /> Former ARCO Service Station No. 443 <br /> October 17, 2008 <br /> with high pressure steam following the completion of each soil boring. Down-hole sampling <br /> equipment will be decontaminated between samples using an Alconox detergent solution and a <br /> tap water rinse. <br /> At the terminal depth of the boring, a well will be installed within the annulus of the auger. The <br /> well will be constructed using four-inch diameter, flush-threaded, schedule 40 poly vinyl chloride <br /> well casing and 0.020-inch factory-slotted well screen. The well will be screened from <br /> approximately 105-120 ft bgs; however, the final total depth and screen interval will be <br /> determined in the field based upon observed conditions. A sand filter pack will be placed in the <br /> annular space surrounding the entire screened interval, and will extend approximately one to <br /> two ft above the screen interval. A two to three-foot thick bentonite annular seal will be placed <br /> above the filter pack and will be hydrated. The remainder of the annular space will be filled with <br /> neat cement and/or grout from the top of the bentonite seal to within 12 inches of the surface. <br /> The well will be secured with a locking well cap, and completed with a watertight traffic-rated <br /> well box installed at grade. The well construction diagram for MW-8 is presented as Figure 1. <br /> 443 IRAP Addendum 10-08.doc 2 <br />