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1 CieologfCal Teehatcs kc Page 3 Groundwater Monitoring Report Project No 723 2 June 15, 2004 1.1 Hydrogeology of Site ' A site-specific groundwater gradient and bearing were calculated from computer-generated contours The groundwater was flowing N72°E at a gradient of 0 0049 tt/if The average elevation of groundwater at the site was 23 66 feet below mean sea level or approximately ' 33 5 feet below grade surface (bgs) This represents an increase of 3 42 feet since the November 2003 monitoring event ' Figure 2 is a groundwater gradient map for the March 21, 2004 event Figure 3, Groundwater Gradient Rose Diagram, includes the 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 immaterial 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) u 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 piezoinetric 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 Vertical gradient calculation formulas are as follows ❑ Vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] ' ❑ Vertical head [(head of deep well) - (head of shallow + correction) = vertical head] ❑ Vertical gradient [(vertical head) /(vertical distance) = vertical gradient]