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Geolog"'Technics Inc Page 3 4''Quarter 2001 Groundwater Momtonng Report Project No 507 2 January 17,2002 ' 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 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-109) and the mid- point between the groundwater elevation and the bottom seal in the shallow well (MW- 9) • 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 rFigure 2 shows the location of the well cluster used for calculating the vertical groundwater gradient in this report, MW-9 and MW-109 Table 1 shows Summary of Water Level and M Gradients Slope and Bearing, and Table 2 shows the calculated vertical gradients The information used in the calculations is shown below Vertical gradient calculation formulas are as follows G Vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] 0 Vertical head [(head of deep well) - (head of shallow+ correction) = vertical head] • Vertical gradient [(vertical head) /vertical distance) = vertical gradient] 1 For both of the December 2001 monitoring events a vertical gradient was calculated for the MW-9/MW-109 pair In both cases the vertical gradient was negative (a downward direction) and larger in magnitude than the horizontal gradient of the water table ' 1.2 Groundwater Sampling Procedure 1 On December 4, 2001, Don Light of Del-Tech mobilized to the site to conduct groundwater monitoring of the eleven existing monitoring wells Before sampling was attempted the wells were sounded for depth to water and then a clear disposable bailer was used to determine if floating product was present The wells were purged of at least three well volumes of stagnant water using a dedicated Waterra check-ball assembly and '/z inch tubing Purging continued until the temperature, conductivity, and pH of the groundwater stabilized (<10% variation between three readings), indicating that