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' Gecfvgwa(TecFinws Inc Page 2 Groundwater Monitoring Report Project No 723 2 • January 19,2000 ' 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 0029 ft/ft flowing N66% This is the third event where a site specific groundwater gradient was calculated The 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 36 feet below mean sea level Depths to water ranged ' from 28 4 to 29 2 feet bgs Figure 2 is a groundwater gradient map for the December 16, 1999 event ' This is the second event where the deep discretely screened well, MW-101, was monitored A shallow well was not installed next to MW-101 so a vertical gradient cannot easily be calculated The groundwater head in MW-101 is equal to the head in nearby MW-3 so it appears there is not a significant vertical gradient at this time The previous event appeared to show a downward vertical gradient 1 Table 1 in Appendix A contains the groundwater elevations and gradients for the site ' 1.2 Groundwater Sampling Procedure ' On December 16, 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 ' Stagnant water in the well casing was purged using a Waterra pump as recorded in the field logs (Appendix Q 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 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 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