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cjeoCog,ca(Teckmes Inc Page 2 Groundwatei Monitoring Report Project No 723 2 January 29,2001 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeotogy 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 0046 ft/ft flowing due south This is the sixth event where a site-specific groundwater gradient was calculated by resolving a three-point problem using MW-4, MW-5 and MW-6 These wells were selected because they are constructed relatively similar in regards to depth of screen interval The average elevation of groundwater under the site was 18 33 feet below mean ' sea level Depths to water ranged from 28 28 —29 41 feet bgs Figure 2 is a groundwater gradient map for the December 4, 2000 event This is the fifth event where the deep discretely screened well, MW-101, was monitored A shallow well has not yet been installed next to MW-101 so a vertical gradient cannot easily be calculated The groundwater head in MW-101 is nearly equal (+0 03 feet) to the head in nearby wells MW-2 and MW-3 so it appears there was not a significant vertical gradient on December 4, 2000 Table 1 in Appendix A contains the groundwater elevations andg radients for the site 1.2 Groundwater Sampling Procedure On December 4, 2000, Del-Tech Geotechnical Support personnel arrived on-site, opened ' the wells, and ixieasuied the depth to water with an electrically actuated sounding tape The water level readings were 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 Stagnant water in the well casing was purged using a Waterra pump as recorded in the field logs (Appendix C) The rate of well purging was monitored The wells were purged of approximately 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 character ized 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 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