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rwologual recti ttrs Inc. Page 4 Groundwater Monitoring Report Project No. 1030.2 November 18,2004 • K= average hydraulic conductivity • i = average hydraulic gradient(site-specific average is 0.0038 ft/ft) 0 v= average horizontal groundwater velocity Layer 1 ' The average hydraulic conductivity (K), estimated from typical K values for silt and clay mixtures (Driscoll, 1986), 0.12 feet per year (ft/yr), and where n is effective porosity ' estimated at 0.45 (Driscoll, 1986), the average horizontal groundwater velocity (v) of Layer 1 is estimated to be approximately 1.0 X 10-3 ft/yr. Layer 2 The average hydraulic conductivity (K), estimated from typical K values for sand with some fines (Driscoll, 1986), 11.98 to 119.75 ft/yr, and where n is effective porosity estimated at ' 0.35 (Driscoll, 1986), the average horizontal groundwater velocity (v) of Layer 2 is estimated to be approximately 0.13 to 1.30 ft/yr. ' L&yer 3 The average hydraulic conductivity (K), estimated from typical K values for clay (Driscoll, 1986), 0.12 to 0.012 ft/yr, and where n is effective porosity estimated at 0.50 (Driscoll, 1986), the average horizontal groundwater velocity (v) of Layer 2 is estimated to be approximately 9.12 X 104 to 9.12 X 10.5 ft/yr. 2.0 GROUNDWATER MONITORING ' 2.1 Groundwater Sampling On October 14, 2004, Del-Tech Geotechnical Support Service (Del-Tech) 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. If free floating product had been suspected, a clear disposable bailer would have been used to gauge ' the interface. No floating product was observed during this sampling event. Stagnant water in the well casing was purged using a centrifugal 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 from each well, the 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 1