Laserfiche WebLink
Metadata
Document management portal powered by Laserfiche WebLink 9 © 1998-2015 Laserfiche. All rights reserved.
1 <br /> Geokglcal rec&t&-s lncc. Page 3 <br /> Groundwater Monitoring Report <br /> Project No 723 2 <br /> October 29,2004 <br /> 0 0073 ft/ft The average elevation of groundwater at the site was 27 43 feet below mean sea <br /> level or approximately 37 feet below grade surface (bgs) This represents a decrease of 3 71 <br /> ' feet since the May 6, 2004 monitoring event <br /> Figure 2 is a groundwater gradient map for the August 2004 event Figure 3, Groundwater <br /> Gradient Rose Diagram, includes the historical groundwater directions and gradients <br /> Table 1 in Appendix A contains the groundwater elevations and gradients for the site <br /> Vertical Groundwater Gradients <br /> Under vertical groundwater flow conditions, the water level in a monitoring well is a function <br /> of the length of the well screen and its depth or vertical position in the aquifer As with <br /> horizontal flow conditions, the diameter of the well or piezometer is immaterial A vertical <br /> gradient was calculated for well pair MW-3/MW-201 These wells are located approximately <br /> 5 feet apart <br /> The following procedure is used to calculate vertical groundwater gradient <br /> ❑ Determine vertical distance between the two measuring devices by the distance from the <br /> mid-point between the top and bottom seal of the deep well (MW-201) and the mid-point <br /> between the groundwater elevation and the bottom seal in the shallow well (MW-3). <br /> ❑ Measure the head in both wells used in the calculations <br /> ❑ If the lateral distance between the well pair is greater than a few feet, then calculations <br />' must be made to correct the down-gradient piezometnc head to account for the sloping <br /> water table between the wells The calculation considers the slope of the water table and <br /> the distance in a down-gradient direction between the two wells used in the calculations <br />' Figure 2 shows the location of the well pairs used for calculating vertical groundwater <br /> gradient in this report MW-3/MW-201 Table 1 shows a Summary of Water Level and <br />' Gradients Slope and Bearing and Table 3 shows the calculated vertical gradients The <br /> information used in the calculations is shown below <br />' Vertical gradient calculation formulas are as follows <br /> ❑ Vertical correction for gradient [(gw gradient slope) x (distance) =vertical correction] <br />' ❑ Vertical head [(head of deep well) - (head of shallow+correction) =vertical head] <br /> ❑ Vertical gradient [(vertical head)/(vertical distance) =vertical gradient] <br /> For the August 6, 2004 event, the vertical gradient for the MW-3/MW-201 pair was negative <br /> (or downward) at -0 009 ft/ft Previous calculations have revealed both positive and negative <br /> gradients but additional monitoring is needed to deternune long-term trends <br /> t <br /> I <br />