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C,eohgieal Technics Inc. Page 2 ' Groundwater Monitoring Report Project No. 1030.2 May 7, 2003 ' 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site On January 29, 2003, the depth to groundwater was measured in all of the monitoring wells ' prior to purging. Depths to groundwater ranged from a high of 12.22 feet below the top of casing to a low of 12.71 feet below the top of casing. The average groundwater elevation for the January 2003 event was 64.10 feet above mean sea level (MSL). This average corresponds with historical groundwater elevation measurements recorded at this site. Site-specific groundwater bearing and slope were calculated and found to be N42°E @ 0.0033 ft/ft. These results are consistent with historical groundwater bearing and slope for this site. ' Vertical groundwater gradients were calculated for the site using the MW-I/MW-101 well pair and found to be positive. The site-specific vertical groundwater gradient is 0.0006 ft/ft. MW-1 is screened from 5 to 20 feet bgs and MW-101 is screened from 29.5 to 34.5 feet ' bgs. Vertical groundwater gradient calculations have been performed at regular intervals since the installation of MW-101 on April 12, 2002. The vertical gradients are approximately one order of magnitude less than the horizontal gradients. Groundwater elevation bearingd slope anp were calculated using data gathered from MW-2, ' MW-3 and MW-4 during the January 29, 2003, monitoring event and the results are summarized in Table 1 of Appendix A. Table 2 of Appendix A summarizes the vertical groundwater gradient calculations. ' 1.2 Groundwater Sampling Procedure ' On January 29, 2003, Del-Tech Geotechnical Support personnel arrived on-site and cleared the roots from MW-3. Del-Tech personnel then 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. If free floating product had been suspected, a clear disposable bailer would have been used to gauge the interface. No floating product was observed during this sampling event. ' Stagnant water in the well casing was purged using a Waterra pump and dedicated tubing. The rate of well purging was monitored. The well was purged of at least three casing voluines 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 Ieast 80% of its initial level. All water removed from the monitoring well and not used as a sample was placed in a 55 gallon DOT approved container that is properly labeled and ' temporarily stored on-site.