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G¢afogical7"eclueirslru. Page 2 Groundwater Monitoring Report Project No. 750.2 May 14,2002 '-" consistent with past events (see Figures 2 & 3). Depth to groundwater at the site was approximately 62 feet below ground surface (bgs) for both events. A vertical groundwater gradient calculation was made for the January 2002 groundwater- monitoring event. The vertical gradient was found to be in a downward direction with a slope that is approximately 1.3 times greater than the water table horizontal gradient. This y is consistent with past events. A vertical groundwater gradient calculation was made for the March 2002 groundwater- monitoring event. The vertical gradient was found to be in an upward direction with a slope that is approximately 1.6 times greater than the water table horizontal gradient. The internal �. combustion engine (LC.) was set in operation on February 5, 2002. Mechanical problems with the I.C. unit caused it to be down for approximately 6 weeks. It is now back in operation and the problems appear to have been fixed. Vacuum from the I.C. system may +� have influenced the vertical groundwater gradient. 1.0 GROUNDWATER MONITORING 1.1 Hydrogeology of Site The dominant soil type in the upper 75 feet of subsurface geologic soils investigated is sand with fine to coarse-grained texture. Varying amounts of silt, silty sand and laterally discontinuous clay lenses were encountered from borehole to borehole. A thick clay layer was encountered starting at 95-feet in SB-101/MW-101 and continues to at least 115-feet. The average groundwater elevation on the January 14, 2002, event was about 55.49 feet above mean sea level, which is consistent with previously measured average elevations at the site. The groundwater elevation represents an increase of approximately 0.53 feet since the monitoring event of November 16, 2002. '-� The average groundwater elevation on the March 14, 2002, event was about 55.95 feet above mean sea level, which is consistent with previously measured average elevations at the site. The groundwater elevation represents an increase of approximately 099 feet since the monitoring event of November 16, 2002. Groundwater gradients were calculated for the January 2002 and March 2002 events. Groundwater was flowing N891W at 0.0019 ft/ft and N8PW at 0.0018 ft/ft respectively. MW-1, MW-2 and MW-3 were used for the gradient calculations. The elevation, gradient and bearing data are summarized in Table 1, Appendix A. The gradient direction is illustrated on Figure 2: Gradient Map January 2002 and Figure 3: Gradient Map March w.