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Geologica(Tacfvnws Inc Page 2 ' Groundwater Monitoring Report Project No 770 2 October 15,2002 ' On June 21, 2002, the wells were re-surveyed in accordance with the Geotracker requirements by Thompson-Hysell Engineering of Modesto, CA Groundwater gradient calculations show that groundwater flow in the water table wells was S8°E with a slope of 0 013 ft/ft-"'The deeper aquifer groundwater flow was N88°E with a ' slope of 0 0016 ft/ft Based on a previous consultant's data this site has a history of variable groundwater flow direction GTI's monitoring efforts confirm that groundwater direction / vanes from quarter to quarter at the site ' 1.0 GROUNDWATER MONITORING 1.1 Hydrogeology of Site ' The site exhibits a primarily silty/clayey geology with minor sand layers/lenses, pebbles, black organics and iron staining occasionally present The groundwater elevation on June ' 7, 2002, averaged —36 54 feet mean sea level (MSL) or —60 feet below grade surface (bgs) This represents a decrease of about 1 5 feet since the March 2001 monitoring event On June 21, 2002, the wells were re-surveyed in accordance with the Geotracker requirements by Thompson-Hysell Engineering of Modesto, CA The above data are normalized to these new data Groundwater elevation and gradient data are summarized in Tables 1 and 2, Appendix A - ' Water table well gradient direction is shown on Figure 2A. and deep well gradient direction is illustrated in Figure 2B IThe historical water table gradients are illustrated in Figure 3 Groundwater Gradient Rose Diagram Water Table Wells The site displays highly variable shifts in groundwater direction 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 ' • 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- point between the groundwater elevation and the bottom seal in the shallow well (MW- 5) _ • Measure the head in both wells used in the calculations • If the lateral distance between the well pair is greater than a few feet, then calculations must be made to correct the down-gradient piezometric head to account for the sloping