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GeolagrcaCTechnus Inc Page 2 Groundwater Monitoring Report Project No 425 2 • November 17, 1997 1.0 GROUNDWATER MONITORING 1.1 Hydrology of Site Horizontal Groundwater Gradient The average groundwater elevation at the site was 90 15 feet above mean sea level This represents a decrease of approximately 12 feet since the last monitoring event in May of 1997 Table 1 of Appendix A summarizes the groundwater level measurements to date Groundwater gradient calculations show that the dominant groundwater flow is in a northern direction with the slope ranging from 0 0017 up to 0 0289 ft/ft Vertical groundwater gradients were calculated using MW-2 and MW-102 and found to be in a downward direction The gradients were the same order of magnitude as that of the horizontal gradients, however they were 1 75 to 2 times greater, Table 2 of Appendix A Vertical Groundwater Gradient Under vertical groundwater flow condition, 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 o Determine vertical distance between the two measuring devices by the distance from the mid-point between the top and bottom seal of the deep wells (MW-101 & 102) and the mid-point between the groundwater elevation and the bottom seal in the shallow well (MW-1 & 2) o Measure the head in both wells used in the calculations a 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 water table between the wells The calculation considers the slope of the water table and the distance in a down-gradient direction between the two wells used in the calculations Vertical gradient calculation formulas are as follows Io vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] o vertical head [(head of deep well) - (head of shallow+correction) = vertical head] 0 vertical gradient [(vertical head /vertical distance) =vertical gradient] 1.2 Groundwater Sampling Procedure On September 19, 1997, Del-Tech Geotechnical Support personnel arrived on-site, opened the wells, and measured the depth to water with an electrically actuated sounding tape The I