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Geological Tecltatccs lits Page 3 ' Groundwater Monrtonng Report Project No 425 2 July 26,2002 gradient The vertical gradient in the intermediate/deep well pair was upward at a ' magnitude of approximately 8 times that of the 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 Refer to Table 3 of Appendix A for a summary of the vertical gradient calculations 1.2 Groundwater Sampling Procedure On June 5, 2002, 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 Free product (sheen) was evident in well MW-2 Stagnant water in the well casing was purged using a Centrifugal pump as recorded in the field logs (Appendix C) 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 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 its initial level 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 tA stainless steel bailer 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-mi 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 an ice chest cooled to VC 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 field to the laboratory, thereby providing a means to track the movement and insure the integrity of the samples