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Geological TecluucsInc Page 2 Groundwater Monitoring Report Project No 770 2 April 30, 2003 t 1 0 GROUNDWATER MONITORING 1 l H dro eolo of Site Y g gy ' The site exhibits a primarily silty/clayey geology with minor sand layers/lenses, pebbles, black organics and iron staining occasionally present The water table well groundwater elevation on November 19, 2002 averaged —41 05 feet mean sea level (MSL) or —65 feet below grade surface (bgs) On December 18, 2002 the averaged depth to groundwater in the water table wells was approximately 64 feet bgs and elevation averaged —40 39 feet ' MSL This represents a cumulative decrease of approximately 0 06 feet since the September 2002 monitoring event Groundwater gradient calculations indicate that the flow in the water table wells was S65°E with a slope of 0 001 ft/ft on November 11, 2002 On December 18, the water table well gradient was SWE with a slope of 0 001 ft/ff The groundwater gradient in the deeper aquifer monitored by wells MW-104, 105 & 106 was also calculated for the two sounding events On November 11 the deeper aquifer giadient was N84°E with a slope of 0 0014 ft/ft, and on December 18 it was N82°E with a slope of 0 0013 ft/ft Groundwater elevation and gradient data are summarized in Tables I and 2, Appendix A Water table well gradient directions are shown on Figure 2A & 3A for the November and December events, respectively Wells MW-4 and MW-5 are excluded from the contouring ' due to anomalous values that contort the contours in the central portion of the site The deep well gradient diiections for the two events are illustrated in Figures 2B and 3B i The historical water table gradients are illustrated in Figure 4A & 4B Groundwater Gradient Rose Diagrams for Water Table and Deep Wells, respectively The site's shallow ' aquifer displays highly variable shifts in groundwater direction while the deeper aquifer flow has been consistently to the east for the four events it has been monitored ' Vertical Groundwater Gradients Under vertical groundwater flow conditions, the water level in a monitoring well is a function of the length of the well screen and its depth or vertical position in the aquifer As ' with horizontal flow conditions, the diameter of the well or piezometer is immaterial The following procedure is used to calculate vertical groundwater gradient ' 0 Determine vertical distance between the two measuring devices by the distance from the mid-point between the top and bottom seal of the deep well (MW-105) and the mid- '