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C,eologwol Tecluurs lftc Page 3 Groundwater Monitoring Report Project No 770 2 September 24,2003 ' 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 ' June 2003 sounding event 1 Vertical Groundwater Gradients Under vertical groundwater flow conditions, the water level to 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 ' • Detennine 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) • 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 to a down-gradient direction between the two wells used in the calculations Figures 2A & 213 show the location of the well clusters, MW-51105 and MW-61106, used ' 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] ' • Vertical gradient [(vertical head) / vertical distance) =vertical gradient] Vertical gradients were calculated for the MW-51105 & MW-6/106 well pairs for the 2nd ' quarter 2003 monitoring events The vertical gradient was zero for the MW-51105 well pair on April 28 and negative (a downward direction) on May 23 and June 18 The MW-61106 ' well pair vertical gradients were zero on April 28, positive (an upward direction) on May 23, and negative (a downward direction) on June 18