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"04kal Teewa MC Page 3 Groundwater Monrtonng Report Project No 425 2 August 6,2004 ' 1.1.2 Vertical Groundwater Gradients Vertical groundwater gradients were calculated using groundwater-monitoring wells MW- 2/MW-102 (shallow/intermediate well pair) and groundwater monitoring wells MW- 102/MW-202 (intermediate/deep well pair) (Table 5) The site-specific vertical groundwater gradient for the MW-2/MW-102 pair is 0 0325 ft/ft The site-specific vertical groundwater ' gradient for the MW-102/MW-202 pair is 0 0142 ft/ft The site does not show a trend toward downward contaminant migration between the ' intermediate and deep monitoring wells MW-2 is screened from 5 to 20 feet bgs, MW-102 is screened from 45 to 47 5 feet bgs and MW-202 is screened from 79 to 815 feet bgs ' Vertical groundwater gradient calculations have been performed at regular intervals since August 25, 1997 ' 1.2 Groundwater Sampling Procedure On April 27, 2004, Del-Tech Geotechnical Support (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 Stagnant water in the well casing was purged using a Honda® centrifugal pump or a Waterra® pump with dedicated tubing as recorded in the field logs (Appendix Q 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 MW-7 and MW-8 exhibited very poor recharge and recharged to 66%, and MW-101 recharged to 77% of their initial level before sampling All water removed from the monitoring wells and not used as a sample was placed in a properly labeled 55 gallon DOT (Department of Transportation 17-H) approved container and temporarily stored on-site A 1-foot stainless steel bailer and stainless steel wire line or a Waterra®pump with dedicated tubing was used to collect each sample Extreme care was exercised while collecting samples to prevent agitation of the water contained in the bailer Water samples were transferred ' from the bailer into 40-m1 VOA vials preserved with hydrochloric acid using a bottom- emptying device that minimizes sample aeration during transfer of the sample. All samples were checked for headspace bubbles, labeled, inserted into foam holders and placed into a ' cooled ice chest for transport to the laboratory The sampling technician wore disposable gloves while collecting all samples