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Page 3 -` -- '------`--_�__� <br /> Groundwater Monitoring Report <br />' Project No 425 2 <br /> • May 12,2003 <br />' vertical gradient in the intermediate/deep well pair was upward, positive, at a magnitude of <br /> approximately 14 5 times that of the intermediate horizontal gradient <br /> ' This site has experienced both negative (downward) vertical gradients and positive (upward) <br /> vertical gradients Typically, the negative vertical gradients are 175 to 2 times greater than <br /> gradients in a horizontal direction and the positive vertical gradients aie an order of <br /> magnitude greater than horizontal <br /> ' Positive vertical gradient dominates and may be the main reason for preventing these <br /> contaminants from impacting the deeper aquifer <br /> ' Refer to Table 3 of Appendix A for a summary of the vertical gradient calculations <br /> 12 Groundwater Sampling Procedure <br /> On March 21 2003 Del-Tech Geotechnical Support personnel arrived on-site, opened the <br /> pp p P <br /> wells, and measured the depth to water with an electrically actuated sounding tape The <br /> water level reading was recorded to an accuiacy of 0 01 foot In wells where free-floating <br /> product was suspected, a clear disposable bailer was used to gauge the interface Floating <br /> sheen pioduct was evident in well MW-2 <br /> Stagnant water in the well casing was purged using a Honda® centrifugal pump as recorded <br /> in the field logs (Appendix Q The rate of well purging was monitored The wells were <br /> purged of at least three casing volumes or until the groundwatei parameters (temperature, <br /> conductivity, and pH) had stabilized (Appendix Q indicating that water representative of <br /> ' actual aquifer conditions was entering the well Groundwater parameter stabilization was <br /> characterized by three successive readings within 10% <br /> ' Before a sample was collected, the well's water level was allowed to recharge to at least 80% <br /> of its initial level MW-3, MW-4, MW-7 and MW-8 exhibited poor recharge All water <br /> removed from the monitoring wells and not used as a sample was placed in a properly labeled <br /> 55 gallon DOT (Department of Transportation 17-H) approved container and temporarily <br /> stored on-site <br /> ' A 1-foot stainless steel bailer and stainless steel wire line was used to collect each sample <br /> Extreme care was exercised while collecting samples to prevent agitation of the water <br /> ' contained in the bailer Water samples were transferred from the bailer into 40-m1 VOA vials <br /> preserved with hydrochloric acid using a bottom-emptying device that minimizes sample <br /> aeration during transfer of the sample All samples were checked for headspace bubbles, <br /> ' labeled, inserted into foam holders and placed into a cooled ice chest for transport to the <br /> laboratory <br />