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GENESIS ENGINEERING&REDEVELOPMENT <br /> Ms. Amy Terrell <br /> August 21, 2006 <br /> Page 4 <br /> bottom. Ten-foot long well screens will be installed at an approximate depth interval of 30 feet <br /> to 40 feet below ground surface ("bgs'). The annular space around the well screen will be <br /> backfilled with clean, Monterey sand by placing the sand through the augers as they are removed <br /> from the boring. The well will then be surged to settle the sand pack prior to sealing the annular <br /> space. Additional sand will be added as needed to ensure the sand pack extends to at least 2 feet <br /> above the top of the well screen. At least 2 feet of hydrated bentonite will be placed above the <br /> sand pack. The remaining annular space will be sealed with cement grout. The wellhead will be <br /> completed below grade and will be protected by a traffic-rated monitoring well vault with a <br /> watertight lid. <br /> Deeper Monitoring Wells <br /> Two monitoring wells will be installed to a depth no greater than 200 feet at locations shown on <br /> Figure 1 and Figure 3. These wells will be screened to target the depth intervals corresponding <br /> to the screened intervals of adjacent City of Ripon water supply wells. The corresponding depth <br /> intervals vary from 165 to 196 feet bgs. These wells will allow the groundwater chemistry to be <br /> determined in the deeper saturated interval in the immediate vicinity of the Site. <br /> To reduce the possibility of cross-contamination between the shallow and deeper aquifers, <br /> conductor casing will. be installed into the aquitard above the proposed screened interval for the <br /> deeper monitoring wells. Based on a review and interpretation of lithologic information in the <br /> vicinity of the Site, the conductor casing will be set to an approximate depth of 145 feet bgs. <br /> The conductor casing will be installed using a truck-mounted drill rig equipped with cable-tool <br /> or mud rotary equipment. The monitoring wells will be installed through the conductor casing, <br /> using a truck-mounted drill rig equipped with hollow-stem augers. Continuous soil samples will <br /> be collected The wells will be constructed of 4-inch diameter, schedule 80, poly vinyl chloride <br /> casing, and machine slotted 0.010-inch screen at the bottom. Twenty-foot long well screens will <br /> be installed at the target intervals. The annular space around the well screen will be backfilled <br /> with clean, Monterey sand by placing the sand through the augers as they are removed from the <br /> boring. The well will then be surged to settle the sand pack prior to sealing the annular space. <br /> Additional sand will be added as needed to ensure the sand pack extends to at least 2 feet above <br /> the top of the well screen. At least 2 feet of hydrated bentonite will be placed above the sand <br /> pack. The remaining annular space will be sealed with cement grout. The wellhead will be <br /> completed below grade and will be protected by a traffic-rated monitoring well vault with a <br /> watertight lid. <br /> i <br />