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Geo4tca[?echnics Inc Page 2 Groundwater Monitoring Report ' Project No 425 2 June 13, 1997 recommendations for work to completely characterize this site and evaluate the risk these chemicals pose to public health and the environment This report will also include the ' findings of the wells survey 1.0 GROUNDWATER MONITORING 1.1 Hydrology of Site The average groundwater elevation at the site was 89 57 feet above mean sea level This represents a decrease of approximately 1 5 feet since the last monitoring event in September 1995 Table 1 of Appendix A summarizes the groundwater level measurements to date Groundwater gradient calculations show that the dominant groundwater flow is in a northern direction with the slope ranging from 0 0017 up to 0 0289 ft/ft 1.2 Groundwater Sampling Procedure • On January 17, 1997, 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 Stagnant water in the well casing was purged using either a Grundfos pump or electronic bailer as recorded in the field logs (Appendix Q 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 Q indicating that water, representative of actual aquifer conditions, was entering the well Groundwater parameter stabilization was characterized by three successive readings within 10% In this case the instrument was not calibrating properly, and pH measurements were not considered reliable Before a sample was collected, the well's water level was allowed to recharge to at least 80% of it's initial level All water removed from the monitoring wells and not used as a sample, was placed in a 55 gallon DOT (Department of Transportation 17-11) approved container that is properly labeled and temporally stored on-site A 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 vial) prior to collecting the analytical sample •