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' cwto kol Tedwa i= Page 4 g g Groundwater Momtonng Report Project No 723 2 February 28,2005 ' For the October 2004 event, the vertical gradient for the MW-3/MW-201 pair was negative (or downward) at -0 002 ft/ft Previous calculations have revealed both positive and negative ' gradients but additional monitoring is needed to determine long-term trends 1.2 Groundwater Sampling Procedure On October 21, 2004, 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 CMTrm wells due to their ' limited diameter) CM rm wells MW-7 &MW-8 were dry and not sampled 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 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 55-gallon DOT ' (Department of Transportation 17-H) approved container and temporarily stored on-site The dedicated Waterra pump was used to collect each monitoring well sample Care was t exercised while transferring the sample into 40-m1 VOA vials preserved with hydrochloric acid All samples were checked for headspace bubbles, labeled, inserted into foam holders and placed into an ice chest cooled to 4°C for transport to the laboratory ' The sampling technician wore disposable gloves while collecting all samples ' A chain of custody document, listing all samples collected and their intended analyses, accompanied the samples from the field to the laboratory, thereby providing a means to track the movement of the samples and ensure their integrity 1.3 Laboratory Analyses ses ' The groundwater samples collected on October 21, 2004, were delivered to Sherwood Labs of Hilmar, California (certification#1400) for analyses of ' ❑ Benzene, Toluene, Ethyl Benzene, and Xylene (BTEX), MTBE, by EPA method 8020 ❑ Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 5030/8015(M) 1