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GeologtcalTechxlcs!nc Pagc.3 Groundwater Monitoring Report Project No 723 2 April 24, 2006 The ability to sound the wells resulted in changes in quarterly monitoring reports The wells have been grouped according to the aquifer interval that the screened section intercepted (see ' Figure 14 for well screen intervals) ' Shallow Wells (screened 35 — 55 feet bgs) MW-4, 5, 6, 7, 8 & 9 Intermediate Wells (screened 43 — 70 feet bgs) MW-1, 2, 3, 107, 108 & 109 Deep Wells (screened 76 —80 feet bgs) MW-207, 208 & 209 Deepest Wells (screened 94— 97 feet bgs) MW-101, 307, 308 & 309 The aquifer was divided in four horizons based on the screened intervals and groundwater ' gradient contour maps constructed for each horizon shallow, intermediate, deep and deepest 1.1 Hydrogeology of Site ' Horizontal Groundwater Gradients The calculated gradients for the January 2006 monitoring event are as follows ' Aquifer Zone Screen Interval Gradient Bearing MW No Water table 35 to 55 ft bgs 0 0030 ft/ft N490E 4, 5, 6, 7, 8 & 9 Intermediate 43 to 70 ft bgs 0 004 ft/ft N520E 1, 2, 3, 107, 108 & 109 Deep 76 to 80 ft bgs 0 003 ftJft N500E 207, 208 & 209 Deepest 94 to 97 ft bgs vanable variable 101, 307, 308 & 309 ' Figures 2A through 2D illustrate four aquifer groundwater gradient maps for the January 2006 event Figure 3, Groundwater Gradient Rose Diagram, includes the historical shallow ' groundwater directions and gradients Tables 1 —4 in Appendix A contain the groundwater 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 pairs MW-3/MW-201, MW-8/MW-108 and MW- 108/MW-208 t The following procedure is used to calculate vertical groundwater gradient Li 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-paint 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 piezometnc head to account for the sloping 1