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c7cologual Technks inc Page 3 <br /> Groundwater Monitoring Report <br /> Project No 425 2 <br /> April 18,2003 <br /> This site has experienced both negative (downward) vertical gradients and positive <br /> ' (upward) vertical gradients Typically, the negative vertical gradients are 1 75 to 2 times <br /> greater than gradients in a horizontal direction and the positive vertical gradients are an <br /> - order of 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 /> 1.2 Groundwater Sampling Procedure <br /> ' On December 26, 2002, Del-Tech Geotechnical Support personnel arrived on-site, opened <br /> the wells, and measured the depth to water with an electrically actuated sounding tape The <br /> water level reading was recorded to an accuracy of 0 01 foot In wells where free-floating <br /> ' product was suspected, a clear disposable bailer was used to gauge the interface Free <br /> product was evident in well MW-2 <br /> Stagnant water in the well casing was purged using a Centnfugal pump as recorded in the <br /> field logs (Appendix C) The rate of well purging was monitored The wells were purged <br /> ' of at least three casing volumes or until the groundwater parameters (temperature, <br /> conductivity, and pH) had stabilized (Appendix C) 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 <br /> ' 80% of its initial level All water removed from the monitoring wells and not used as a <br /> sample was placed in a properly labeled 55 gallon DOT (Department of Transportation 17- <br /> H) approved container and temporarily stored on-site <br /> ' A 1-foot stainless steel bailer was used to collect each sample Extreme care was exercised <br /> while collecting samples to prevent agitation of the water contained in the bailer Water <br /> ' samples were transferred from the bailer into 40-ml VOA vials preserved with hydrochloric <br /> acid using a bottom-emptying device that minimizes sample aeration during transfer of the <br /> ' sample All samples were checked for headspace bubbles, labeled, inserted into foam <br /> holders and placed into a cooled ice chest for transport to the laboratory <br /> ' The sampling technician wore disposable gloves while collecting all samples <br />