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Geological nchttks Inc P age 2 Groundwater Monitoring Report Project No 723 2 December 17,2002 ' in the shallow wells ranged from 34 02 — 35 81 feet b s It is noted that the water table g g exceeded the screened interval of all of the site's eight wells m the September 9 2002 event Figure Figura 2 is a groundwater gradient map for• p , 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 iminatenal A vertical gradient was calculated for well pair MW-3/MW-201 These wells are located approximately 5 feet apart iThe 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 Beanng 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 headl ' • Vertical gradient [(vertical head) / (vertical distance) = vertical gradient] For the September 2002 event, the vertical gradient for the MW-3/MW-201 pair was0 01 ft/ft , in a negative (or downward) direction This is the third consecutive event in whi negative vertical gradient was recorded for this well pair In December 2001 the gradient y