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CJeofogicalTechmcs 2nc Groundwater Monitoimg Report Project No 724 2 November 13, 2001 Page 2 of groundwater under the site was —18 70 feet (below) mean sea level (msl) The water level has risen significantly at the site since October of 1992 when groundwater was --39 feet msl ' Figure 2 is a water table well groundwater gradient map for the September 17, 2001 monitoring event Historical groundwater gradient data are illustrated in Figure 4, Groundwater Gradient Rose Diagram Figure 3 is an intermediate well groundwater gradient map for the event In the intermediate wells (water above the screened interval of the well) MW -1 through MW -3, MW -106 and MW -107, groundwater flowed S87°E at a gradient of 0 0016 ft/ft Deep well MW -104 is not screened across similar elevations so a deeper gradient was not calculated for the event Table 1 in Appendix A contains the shallow groundwater elevations and gradients for all events since the start of this project in October 1992 Table 2, Appendix A contains the historical intermediate/deep groundwater elevations 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 immaterial 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 -104, MW -106, MW - 107) and the mid -point between the groundwater elevation and the bottom seal in the shallow well (MW -4, MW -6, MW -7) • 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-4/MW-104, MW-6/MW-106, and MW-7/MW-107 Tables I & 2 show 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