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Geological Technics!nc Page 4 Groundwater Monitoring Rtport Project No 723 2 April 24,2006 water table between the wells The calculation considers the slope of the water table and ' the distance in a down-gradient direction between the two wells used in the calculations Figure 2 shows the location of the well pairs used for calculating vertical groundwater ' gradient in this report MW-3/MW-201, MW-8/MW-108 and MW-108/MW-208 Tables 1 - 4 show Summaries of Water Level and Gradients Slope and Bearing and Table 6 shows the calculated vertical gradients The information used in the calculations is shown below ' Vertical gradient calculation formulas are as follows ❑ Vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] ❑ Vertical head [(head of deep well) - (head of shallow + correction) = vertical head] ❑ Vertical gradient [(vertical head) / (vertical distance) = vertical gradient] For the 1" Quarter 2006 event o The vertical gradient for the MW-3/MW-201 pair was negative (or downward) at - 0 00 l ft/ft o The vertical gradient for the MW-8/MW-108 pair was positive (or upward) at 0 004 ft/ft o The vertical gradient for the MW-108/MW-208 pair was positive (or upward) at 0 002 ft/ft o Previous calculations have revealed both positive and negative gradients at the site but additional monitoring is needed to determine long-term trends especially in the CMTTM well sets 1.2 Groundwater Sampling Procedure On January 17, 2006, 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 readings were recorded to an accuracy of 0 01 feet In wells where free-floating product is suspected, a clear disposable bailer is used to gauge the interface During this monitoring ' no free product was noted (this procedure is not exercised in the CMTTM wells due to their limited diameter) ' Stagnant water in the well casing was purged using a Waterra pump as recorded in the field logs (Appendix C) The rate of well purging was monitored The wells were purged of approximately three casing volumes and until the groundwater parameters (temperature, ' conductivity and pH) had stabilized (Appendix C) indicating that water representative of actual aquifer conditions was entering the well Well MW-108 purged dry before three well volumes were removed 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 the initial level The purge water was placed in a properly labeled SS-gallon DOT (Department of Transportation 17-H) approved container and temporarily stored on-site