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' C�eoloAAical�"ecF=nics Znc. Page 2 Siaclazr Truckulg-QMR Project No. 320.2 February 11,2000 ' It is recommended that: 1. That testing for MTBE and the other OFCs should be discontinued. 2. A work plan for the further definition of soil and groundwater contamination has been submitted. This work should be implemented as soon as cost pre-approval from the fund ' is received. ' 1.0 GROUNDWATER MONITORING 1.1 Hydrology of Site ' On December 20, 1999, Del-Tech Geotechnical Support personnel measured the four monitoring wells for depth to groundwater. The average depth to water was measured to be approximately 12.4 feet from the top of casing measuring point. The groundwater gradient ' and bearing of flow were calculated to be 0.0038 ft/ft, flowing N43°E, respectively. This hydrologic behavior is consistent with previous.groundwater_gradients.measured at this site. Figure 2 is a map showing both the water table and intermediate groundwater gradients. Appendix D shows an example of the mathematical calculations used to obtain the ' groundwater gradient. 1.2 Groundwater Sampling Procedure On December 20, 1999, Dei-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 was used to gauge the interface. Stagnant water in the well casing was purged using a Centrifugal pump 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 or 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 well's water level was allowed to recharge to at least 80% of its 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 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 vial)prior to collecting the analytical sample. ' - Extreme care was exercised while collecting samples to prevent agitation of the water contained in the bailer and to minimizes sample aeration during transfer of the sample into the bottles. Water samples were transferred from the bailer into 40-m1 VOA vials preserved with hydrochloric acid. All samples were checked for headspace bubbles, labeled, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory. 1