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C*[4gkal rech=s lac. Page 3 <br /> Groundwater Monitoring Report <br /> Project No 724 2 <br /> August 27,2004 <br /> ' Figure 5C shows that the dee aquifer gradient was to the east for the two events following <br /> p q g g <br /> the installation of four additional deep wells in December 2003 <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 <br /> The following procedure is used to calculate the vertical groundwater gradient <br /> • Determine vertical distance between the two measuring devices by the distance from the <br /> ' rrud-point between the top and bottom seal of the deep well (MW-104, MW-106, MW- <br /> 107) and the mid-point between the groundwater elevation and the bottom seal in the <br /> shallow well (MW-4, MW-6, MW-7) <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 /> Figures 2 -- 4 show the location of the well pairs used for calculating vertical groundwater <br /> gradient in this report MW-4/MW-104, MW-6/MW-106, and MW-7/MW-107 Tables 1, 2 <br /> & 3 show a Summary of Water Level and Gradients Slope and Beanng and Table 4 shows <br />' the calculated vertical gradients The 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 April 2004 event, the vertical gradient for the MW-4/MW-104 parr was negative <br />' (downward) In well parrs MW-6/MW-106 and MW-7/MW-107 the vertical gradient was <br /> positive (upward) The trend of a negative gradient in MW-4/MW-104 and a positive or no <br /> gradient in the other pairs is consistent with the historical data It is noted that the vertical <br />' distance to the deep well screen in the MW-4/MW-104 well pair is double the distance of the <br /> other two well pairs <br />' 1..2 Groundwater Sampling Procedure <br /> On April 29, 2004, Del-Tech Geotechnical Support personnel arrived on-site, opened the <br />' wells and measured the depth to water with an electrically actuated sounding tape The water <br /> level reading was recorded to an accuracy of 0 01 foot In wells where free-floating product <br /> 1 <br />