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1,eofogicaI Techxirs lae Page 2 Groundwater Monitoring Report Project No 723 2 March 15,2002 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site ' A site-specific groundwater gradient and bearing were calculated from computer software generated contours The gradient was 0 0056 ft/ft flowing N87°E The average elevation of groundwater under the site was 22 09 feet below mean sea level Depths to water in the ' shallow wells ranged from 31 45 --32 34 feet bgs f Figure 2 is a groundwater gradient map for the December 11, 2001, event Figure 3, ' Groundwater Gradient Rose Diagram, includes historical groundwater directions and gradients Table 1 in Appendix A contains the groundwater elevations and gradients for the site Vertical Groundwater Gradients Under vertical groundwater flow conditions, the water level in a monitoring well is a function of the length of the well screen and its depth or vertical position in the aquifer As with horizontal flow conditions, the diameter of the well or piezometer is imiriaterial A vertical gradient was calculated for well pair MW-3/MW-201 These wells are located approximately 5 feet apart The following procedure is used to calculate vertical groundwater gradient • Determine vertical distance between the two measuring devices by the distance from the ' mid-point between the top and bottom seal of the deep well (MW-201) and the mid- point between the groundwater elevation and the bottom seal in the shallow well (MW- 3) • Measure the head in both wells used in the calculations • If the lateral distance between the well pair is greater than a few feet, then calculations ' must be made to correct the down-gradient piezometric head to account for the sloping water table between the wells The calculation considers the slope of the water table and the distance in a down-gradient direction between the two wells used in the calculations Figure 2 shows the location of the well pairs used for calculating vertical groundwater gradient in this report MW-3/MW-201 Table 1 shows a Summary of Water Level and ' Gradients Slope and Bearing and Table 3 shows the calculated vertical gradients The information used in the calculations is shown below 1 1