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Geologkal7echnkslrcc Page 4 Groundwater Monitoring Report Project No 723 2 June 20,2005 ' Tables 1 —4 in Appendix A contain the groundwa ' ter 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 the well pair MW-3/MW-201 and for the second time the MW- 8/MW-108 and MW-108/MW-208 well pairs ' 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) ❑ 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, MW-8/MW-108 and MW-108/MW-208 Tables 1 - 4 show Summaries of Water Level and Gradients Slope and Bearing and Table 6 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] o Vertical gradient [(vertical head)/ (vertical distance) = vertical gradient] ' For the 2nd Quarter 2005 event o The vertical gradient for the MW-3/MW-201 pair was negative (or downward) at - 0 001 ft/ft ' o The vertical gradient for the MW-8/MW-108 pair was negative (or downward) at - 0 005 ft/ft o The vertical gradient for the MW-108/MW-208 pair was positive (or upward) at ' +0 004 ft/ft o Previous calculations have revealed both positive and negative gradients at the site but additional monitoring is needed to determine long-term trends especially in the CMTTM well sets