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r G¢otogicaITeckhicsInc. Page 6 Groundwater Monitoring Report Project No.750.2 November 10,2004 Layer 2 The average hydraulic conductivity (K), estimated from typical K values for sand with some r clasts (Driscoll, 1986), 1,200 to 5.9E105 ft/yr, and the average hydraulic gradient (i) across the site is approximately 0.0019. Based on the equation v = K i/n, where n is effective porosity estimated at 0.40 (Driscoll, 1986), the average horizontal groundwater velocity(v) of Layer 2 is estimated to be approximately 5.7 to 2,850 ft/yr. Laver 3 r The average hydraulic conductivity (K), estimated from typical K values for silt (Driscoll, 1986), 0.1198- to 11.98-feet per year (ft/yr), and the average hydraulic gradient (i) across the site is approximately 0.0019. Based on the equation v = K i/n, where n is effective porosity estimated at 0.40 (Driscoll, 1986), the average horizontal groundwater velocity(v) of Layer 3 is estimated to be approximately 5.6E 104 to 0.057 ft/yr. Layer 4 The average hydraulic conductivity (K), estimated from typical K values for medium to coarse grain sand mixtures (Driscoll, 1986), 119.8- to 11,975-feet per year (ft/yr), and the average hydraulic gradient (i) across the site is approximately 0.0019. Based on the equation v = K i/n, where n is effective porosity estimated at 0.30 (Driscoll, 1986), the average horizontal groundwater velocity (v) of Layer 4 is estimated to be approximately 0.758 to 75.8 ft/yr. r 3.0 GROUNDWATER MONITORING r 3.1 Monitoring Well—Groundwater Sampling Procedure On August 12, 2004, Del-Tech mobilized to the site to conduct a groundwater-monitoring event. Del-Tech personnel 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. No floating product was detected during the monitoring event. Stagnant water in the well casing was purged using a Waterra© pump and dedicated tubing. The rate of well purging was monitored. The well was purged of at least three casing volumes 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 well and not used as a sample was placed in a 55 gallon DOT approved container that is properly labeled and temporarily stored on-site. L