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r GeologiCal TOChgiCS 14C Page 3 Groundwater Monitoring Report Project No 425 2 June 25,2003 The verticalg radient in the intermediate/deep well pair was upward, positive, at a magnitude of approximately 10 7 times that of the intermediate horizontal gradient This site has experienced both negative (downward) vertical gradients and positive ' (upward) vertical gradients Typically, the negative vertical gradients are 1 75 to 2 times greater than gradients in a horizontal direction and the positive vertical gradients are an order of magnitude greater than horizontal Positive vertical gradient dominates and may be the main reason for preventing these contaminants from impacting the deeper aquifer Refer to Table 3 of Appendix A for a summary of the vertical gradient calculations 1.2 Groundwater Sampling Procedure On June 6, 2003, 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 reading was recorded to an accuracy of 0 01 foot In wells where free-floating product was suspected, a clear disposable bailer was used to gauge the interface Floating sheen product was evident in well MW-2 Stagnant water in the well casing was purged using a Honda® centrifugal pump 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-3, MW-4, MW-7 and MW-8 exhibited poor recharge and recharged to 65% 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 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-ml 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 lee chest for transport to the laboratory