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Geo(oguafTecfrntcs Znc Page 2 ' Groundwater Monitoring Report Project No 724 2 May 14, 2002 ' 1.4 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site Site-specific groundwater gradients and bearings for water table and intermediate wells ' weie calculated utilizing computer generated contours On March 12, 2002, the gradient in water table wells MW-4, MW-5, MW-6 and MW-7 was flowing S72°E at 0 0034 ft/ft, which is the southern most direction noted during the course of the investigation The average elevation of groundwater under the site was —18 67 feet (below) msl The water level has risen significantly at the site since October of 1992 when groundwater was —39 feet msl Figure 2 illustrates the water table groundwater gradient map for the March 12, 2002, monitoring event ' Figure 3 is an intermediate well groundwater gradient map for the March 2002 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 S55°E at a gradient of 0 0042 ft/ft Deep well MW-104 is not screened across similar elevations so a deeper gradient was not calculated for the event Table t 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 interiediate/deep groundwater elevations Historical gi oundwater gradient data are illustrated in Figure 4, Groundwater Gradient Rose Diagram Vertical Groundwater Gradients IUnder 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 diametei of the well or piezometer is immaterial ' tcalculate th vertical groundwater gradient The following procedure is used o e g ' • 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 1shallow 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