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' Geologwaf?echnics 2nc Page 3 f - Groundwater Monitoring Report Project No 425 2 June 9, 2000 ' Table 2 of Appendix A summarizes the intermediate depth groundwater gradients and levels to date Table 2 also summarizes the groundwater level data from the deep well, MW-202 ' Figure 2 is a map showing both the water table and intermediate groundwater gradients ' 1.1.2 Vertical Groundwater Gradients Vertical groundwater gradients were calculated using MW-2 / 102 (shallow/intermediate well pair) and MW-102 / 202 (intermediate/deep well pair) During the March 2000 event the vertical groundwater gradient in the shallow/intermediate well parr was in an upward direction with a magnitude of 18 Mmes that of the horizontal gradient The vertical gradient in the intermediate/deep well pair was also upward at a magnitude 9 times that of the horizontal gradient ' This site has experienced both negative (downward) vertical gradients and positive (upward) vertical gradients Typically the negative vertical gradients are 1 75 to 2 times greater than ' gradients in a horizontal direction and the positive vertical gradients are an order of magnitude greater than horizontal Refer to Table 3 of Appendix A for a summary of the vertical gradients calculated 1.2 Groundwater Sampling Procedure On March 31, 2000 Del-Tech Geotechnical Support personnel arrived on-site, opened the wells, and measured the depth to water with an electrically actuated sounding tape The water level reading was recorded to an accuracy of 0 01 foot In wells where free floating product was suspected, a clear disposable bailer was used to gauge the interface Stagnant water in the well casing was purged using a Centrifugal pump as recorded in the field logs (Appendix C) The rate of well purging was monitored The wells were purged of at least three casing volumes or until the groundwater parameters (temperature, conductivity, and pH) had stabilized (Appendix Q indicating that water, representative of actual aquifer conditions, was entering the well Groundwater parameter stabilization was characterized by ' three successive readings within 10% Before a sample was collected, the well's water level was allowed to recharge to at least 80% of its initial level All water removed from the monitoring wells and not used as a sample, was placed in a 55 gallon DOT (Department of Transportation 17-H) approved container that is properly labeled and temporally stored on-site 1