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Geo(ogualTec(rnics 2nc - - - - Page 2 - - - Groundwater Monitoring Report Project No 724 2 June 4, 1999 • ' 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site A site-specific groundwater gradient and bearing was calculated from the depth to water ' measurements taken during the groundwater monitoring The gradient was 0 0034 ft/ft flowing N89°E The average elevation of groundwater under the site was 67 88 feet above mean sea level This is the second highest water level recorded at the site The water level ' has risen over 22 feet at the site since October of 1992 Depths to water were approximately 32 feet bgs Figure 2 is a groundwater gradient map for the January 25, 1999 event Table 1 in Appendix A contains the groundwater elevations for all events back to October 1992 and gradients for the last two events This table will be updated to include all groundwater gradient data for the site 12 Groundwater Sampling Procedure On January 25, 1999, 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 is used to gauge the interface During this monitoring no free product was noted IStagnant water in the well casing was purged using a stainless steel bailer 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 and 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 wells' water level was allowed to recharge to at least 80% of the initial level All water removed from the monitoring well and not used as a sample, was placed in a 55 gallon DOT (Department of Transportation 17-H) approved container that is properly labeled and temporally stored on-site A stainless steel bailer was used to collect each sample Bailer cleanliness was assured by collecting a bailer blank (pouring distilled water through the bailer and collecting it in a VOA Ivial) prior to collecting the analytical sample I