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f�alogfcal hechnf fnc. Page 4 Groundwater Monitoring Report Project No. 1030.2 October 22,2004 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-' ft/yr. Laver 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 the average hydraulic gradient (i) across the site is approximately 0.0038. Based on the equation v = K iln, 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. Laver 3 ' The average hydraulic conductivity (K), estimated from typical K values for clay (Driscoll, 1986), 0.12 to 0.012 ftlyr, and the average hydraulic gradient (i) across the site is ' approximately 0.0038. Based on the equation v = K i/n, 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 10-4 to 9.12 X 10-' ft/yr. 1 2.0 GROUNDWATER MONITORING 2.1 Groundwater Sampling On July 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 an ISCO©peristaltic 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 C) 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 a recharge to t Ieast 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. ' An ISCO© peristaltic pump and dedicated tubing were used to collect each sample. Extreme care was exercised while collecting samples to prevent agitation of the water contained in the Waterra pump. With minimal sample aeration, water samples were transferred from the 1