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3. <br /> 171-90 <br /> GROUNDWATER GRADIENT <br /> Following the installation and development of the monitoring wells, the depth to <br /> groundwater was measured from the top of the well casing on the north side. On <br /> I February 11991, the monitoring well casing was surveyed from a temporary bench <br /> w mark to an elevation measurement of within 0.01 feet. The coordinates and elevations of <br /> ° the monitoring wells, as well as, the depth to groundwater measured on January 25, <br /> 1991 are as follows: <br /> Ia <br /> Depth To <br /> Well Northing Easting Elevation Groundwater <br /> i � FT <br /> f Designation (FT) (FT) (FT) ( ) <br /> ga MW 1 995.9681 1054.3306 99.97 17.79 <br /> EI3 <br /> MW 2 1025.0000 1000.0000 99.95 17.54 <br /> k.:..,: MW 3 950.5782 1014.6358 100.57 18.13 <br /> The Northing and Easting coordinates are measured relative to a baseline through the <br /> ? Set-up pont. From the set-up point, located approximately 32 feet south of cashiers <br /> booth, a backsight to Monitoring Well MW2 was taken and assumed North for the purpose <br /> 4-i <br /> i of generating the coordinate system. The set-up paint is the location from where the <br /> instrument used for measuring distances and angles was positioned. <br /> i <br /> t- <br /> l ` The temporary bench mark was the top of curb at the southwest corner of the cashiers <br /> booth island. An elevation of 100.88 feet was assumed at this temporary bench mark. <br /> f ° <br /> The groundwater gradient was established using the three point triangulation method <br /> between Monitoring Wells MW1, MW2, and MW3 (FIGURE 3). The gradient was <br /> calculated to be 0.005 feet per foot to the northeast. <br /> 14 <br />