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Geo(oguafTechnus Inc Page 2 Groundwater Monitoring Report Project No 425 2 August 15,2400 ' • Verticalg roundwater gradients do exist at the site and range from 2 to 20 times the magnitude of the horizontal gradient At times' the site has experienced both a ' negative and positive vertical gradient 2 Groundwater Contamination a Floating product has routinely been detected in MW-2 (located in the area of the former USTs) during late fall and winter months However it has not been observed in the last few years • The TPH-G & BTEX contamination observed in MW-102 during 1997 and early 1998 have attenuated The TPH-G & BTEX contamination observed in MW-202 during 1998 and early ' 1999 have attenuated and were non-detect for all analytes during the December 1999 and March 2000 events i The domestic well at 1600"A" Durham Ferry Road detected trace concentrations of Benzene during the April 1999 event The well has been non-detect for all other monitoring events, including the last four monitoring events The benzene contamination found in April 1999 was most likely due to cross contamination from the sampling technician or laboratory It is recommended that G Future monitoring should include a complete natural attenuation parameter analysis C This site should be evaluated for the need of source removal to provide needed protection ' to public health and the environment A remedial action alternative evaluation is being prepared and will be submitted shortly 1.0 GROUNDWATER MONITORING ' 1.1 Hydrology of Site 11.1 Horizontal Groundwater Gradients ' Water Table Wells The average water table elevation at the site on June 20, 2000 was 73 69 feet above mean sea level and the water table groundwater gradient was 0 0021 ft/ft flowing N18°E A review of the groundwater gradients shows that the dominant groundwater flow is to the north with the ' slope ranging from 0 0012 up to 0 0289 ft/ft Table 1 of Appendix A summarizes the water table groundwater gradients and levels to date Intermediate & Deep Wells The average groundwater elevation in the intermediate depth wells (MW-102, MW-105 & le MW-107) for June was 73 52 feet above mean sea level and the intermediate depth ' groundwater gradient was 0 0031 ft/ft flowing N85°E