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004gual7'ecWaInc, Page 3 Groundwater Monitoring Report Project No. 750.2 May 14,2002 " 2002. Historical groundwater directions and gradients are presented in Figure 4: Groundwater Gradient Rose Diagram. 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. i. 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-101) and the mid- point between the groundwater elevation and the bottom seal in the shallow well (MW- 1). • 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 W 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. ,rte Figure 2 shows the location of the well cluster used for calculating vertical groundwater gradient in this report, MW-1 and MW-101. 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] V For the January 2, 2002, groundwater measurement, the vertical gradient was calculated for the MW-I/MW-101 pair. The vertical gradient was negative (a downward direction) and �. approximately 1.3 times greater than the water table horizontal gradient. For the March 2, 2002, groundwater measurement, the vertical gradient was calculated for �. the MW-1/MW-101 pair. The vertical gradient was positive (an upward direction) and approximately 1.6 times greater than the water table horizontal gradient. 1.2 Groundwater Sampling Procedure On March 2, 2002, Don Light of Del-Tech mobilized to the site to conduct a groundwater- monitoring event. The wells were first sounded for depth to water and then they were purged of at least three well volumes of stagnant water using a dedicated Waterra pump. w