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Ge0t0gccal T41mcs Inc Page 2 Groundwater Monitoring Report Project No 724 2 March 11, 2003 1.4 GROUNDWATER MONITORING 1.1 Hydrogeology of Site Site-specific groundwater gradients and bearings for water table and intermediate wells were calculated utilizing computer generated contours On December 20, 2002, the gradient in water table wells MW-4, MW-5, MW-6 and MW-7 was flowing S61°E at 0 0042 ft/ft Figure 2 illustrates the water table groundwater gradient map for the monitoring event The average elevation of groundwater under the site was — 21 36 feet (below mean sea level) MSL and this represents a decrease of 2 69 feet since March 2002 The water level has iisen significantly at the site since October of 1992 when ' groundwater was—39 feet MSL Figure 3 is an intermediate well groundwater gradient map for the December 2002 event In ' the interinediate wells (water above the screened interval of the well) MW-1 through MW- 3, MW-106 and MW-107, groundwater flowed S89°E at a gradient of 0 0014 ft/ft Deep well MW-104 is not sci eened across similar elevations so a deeper gradient was not calculated for the event (Table 6) 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 in Appendix A contains the historical intermediate/deep groundwater elevations ' The rose diagram included in Figure 4A shows that the water table groundwater gradients at this site are consistently towards the east The rose diagram included in Figure 4B shows that the interinediate aquifer gradients at this site range from northeast to southeast The gradients were consistently to the east for the last three events ' 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 of 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 the vertical groundwater gradient ' • Determine vertical distance between the two measuring devices by the distance from the mid-point between the top and bottom sea] of the deep well (MW-104, MW-106, MW- 107) and the mid-point between the groundwater elevation and the bottom sea] in the ' shallow well (MW-4, MW-6, MW-7) • Measure the head in both wells used in the calculations 1