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Geologual Tec/t�cccslKc Page 3 <br />' Groundwater Monitoring Report <br /> Pio,ect No 425 2 <br /> May 20, 2002 <br /> 1.1.2 Vertical Groundwater Gradients <br />' Vertical groundwater gradients were calculated using MW-2/MW-102 <br /> (shallow/intermediate well pair) and MW-102/MW-202 (intermediate/deep well pair) <br /> During the February 2002 event the vertical groundwater gradient in the <br /> rshallow/intermediate well pair was in an upward direction with a magnitude of 8 times that <br /> of the horizontal gradient The vertical gradient in the intermediate/deep well pair was <br /> ' upward at a magnitude of appioximately 21 times that of the horizontal gradient <br /> This site has experienced both negative (downward) vertical gradients and positive <br /> ' (upward) vertical gradients Typically, the negative vertical gradients are 1 75 to 2 tines <br /> greater than gradients in a horizontal direction and the positive vertical gradients are an <br /> order of magnitude gieater than horizontal The relationship of upward and downward <br /> vertical gradients in the shallow/intermediate well pair is plotted in Figure 8 It should be <br /> noted from Figure 8 that the depth to groundwater has been on a steady decline since project <br /> start, with annual late summer temporary rises in 1998, 1999 and 2000 and a significant <br /> ' increase in the winter of 2002 <br /> Refer to Table 3 of Appendix A for a summary of the vertical gradient calculations <br /> 1.2 Groundwater Sampling Procedure <br /> P g <br /> ' On February 22, 2002, Del-Tech Geotechnical Support personnel arrived on-site, opened <br /> the wells, and measured the depth to water with an electrically actuated sounding tape The <br /> water level reading was recorded to an accuracy of 0 01 foot In wells where free-floating <br /> product was suspected, a clear disposable bailer was used to gauge the interface Free = <br /> product (sheen) was evident in well MW-2 <br /> Stagnant water in the well casing was purged using a Centnfugal pump as recorded in the <br /> field logs (Appendix C) The rate of well purging was monitored The wells were purged <br /> ' of at least three casing volumes or until the groundwater parameters (temperature, <br /> conductivity, and pH) had stabilized (Appendix C) indicating that water representative of <br /> actual aquifer conditions was entering the well Groundwater parameter stabilization was <br /> ' characterized by three successive readings within 10% <br /> Before a sample was collected, the well's water level was allowed to recharge to at least <br /> 80% of its initial level All water removed from the monitoring wells and not used as a <br /> sample was placed in a properly labeled 55 gallon DOT (Department of Transportation 17- <br /> H) approved container and temporarily stored on-site <br /> A stainless steel bailer was used to collect each sample Extieine care was exercised while <br /> collecting samples to prevent agitation of the water contained in the bailer Water samples <br /> 1 <br />