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A.2 MONITORING WELL DESIGN, TNSTALLATION AND DEVELOPMENT <br />Monitoring well design installation and development for the Arcady site <br />is based on several factors, some of which are summarized as follows: <br />A.2.1 Well Construction Materials <br />Because of the low levels of volatile organic compounds, PVC well screen <br />and casing are acceptable and will be used. The screen will be machine <br />slotted with slot size of 0.01 inches. <br />The filter material will be a clean, washed medium to coarse sand (Lapis <br />Luster No. 2/12). This choice is appropriate for the variety of subsurface <br />conditions expected (silty clay, peat, silty fine sand, coarse sand and <br />gravel). <br />The sealant immediately above the filter material will consist of 1/4- <br />inch diameter, Ca-rich montmorillonite clay bentonite pellets. These will be <br />dropped into the annulus and allowed to settle before the cement/bentonite <br />grout is emplaced. The sealant placed above the bentonite pellets consists of <br />a cement/bentonite mixture of one sack of Type I Portland cement with 4 1/2 to <br />8 gallons of potable water and up to 4% by volume of powdered Ca-rich <br />montmorillonite clay bentonite. <br />A.2.3 Monitoring Well Installation <br />Casings and screens are steam cleaned prior to placement in the borings. <br />Any slough or drilling debris will be removed from the borings prior to <br />placement of the well materials. The well installation sequence for shallow <br />wells follows: <br />Place a 6-inch to 1-foot sand filter bed in the hole;