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Geofaytca1_TecFtn:cs Inc Page 2 <br /> Groundwater Monitoring Report <br /> Project No 425 2 <br /> February 17, 2000 <br /> domestic water wells in the immediate area of the tanks were tested and found to be non- <br /> detect for all analytes Free phase product was observed in MW-2 <br />' A summary of findings include <br /> 1 Hydrogeology <br />' • For the past year and a half, the shallow groundwater gradient has moved increasingly <br /> towards the NE However, the predominate flow direction over the course of the <br /> project has been to the N, with slight variation to the NW and NE <br />' • Vertical groundwater gradient does exist at approximately the same slope as the <br /> horizontal gradient At times the site has experienced both a negative and positive <br /> vertical gradient <br /> 2 Groundwater Contamination <br /> • Floating product has routinely been detected in MW-2 (located in the area of the <br /> former USTs) during late fall and winter months <br /> • The contamination observed in MW-102 during 1997 and early 1998 has attenuated <br /> • The contamination observed in MW-202 has steadily decreased from the initial <br />' concentration observed after installation and was non-detect for all analytes during <br /> the December 1999 event <br /> o The domestic well at 1600"A" Durham Ferry Road detected trace concentrations of <br /> Benzene during the April 1999 event It was non-detect for both the September and <br /> December events <br /> It is recommended that <br /> G Future monitoring should include a complete natural attenuation parameter analysis <br /> o This site should be evaluated for the need of source removal to provide needed protection <br /> to public health and the environment <br /> 10 GROUNDWATER MONITORING <br />, <br /> ' 1.1 Hydrology of Site <br /> 1.1.1 Horizontal Groundwater Gradients <br /> Water Table Wells <br /> The average water table elevation at the site in September was 74 36 feet above mean sea <br /> level and the water table groundwater gradient was 0 0023 ft/ft flowing NI VE The average <br /> water table elevation at the site in December was 72 59 above mean sea level and the water <br /> table groundwater gradient was 0 0015 ft/ft flowing N57°E The groundwater gradient for <br /> the December 1999 event was calculated using MW-3, MW-4 and MW-7 because MW-6 <br /> was plugged with tree roots Usually MW-3, MW-4 and MW-6 are used This may be a <br /> cause of the increased easterly gradient during the December event <br />