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CIO ologual TechluCS Inc Page 3 Groundwater Momtonng Report Project No 770 2 March 31,2004 aquifer displays highly variable shifts in groundwater direction It is noted that groundwater direction has been predominantly to the southeast since additional wells were installed in ' May 2002 The deeper aquifer flow had been consistently to the east for the previous seven sounding events But on April 28 and May 23, 2003, the gradient reversed 180°from an easterly direction to a westerly direction The direction reversed again to the east for the , ' remainder of the 2003 sounding events 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 ' s 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-105) and the mid- point between the groundwater elevation and the bottom seal in the shallow well (MW- 5) 0 Measure the head in both wells used in the calculations a 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 Figures 2A & 2B show the location of the well clusters MW-51105 and MW-61106 used g � s for calculating vertical groundwater gradient in this report Table 1 includes Summary of Water Level and Gradients Water Table Wells, Table 2 includes Summary of Water Level and Gradients Deep Wells, Table 3 shows the calculated vertical gradients, and Table 6 contains the well construction details 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] Vertical gradients were calculated for the MW-51105 & MW-61106 well pairs for the 4t' quarter 2003 monitoring events The vertical gradient was negative (a downward direction) for the MW-51105 well pair on October 20 and November 25, 2003 and zero on December 16 The MW-61106 well pair vertical gradient was positive (an upward direction) on October 20, and zero on November 25 and December 16 1