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1 C7eologicd Techmcs lxc Page 3 Groundwater Monitor mg Report Project No 724 2 November 17,2003 1 The following procedure is used to calculate the 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-104, MW-106, MW- 107) and the mid-point between the groundwater elevation and the bottom seal in the shallow well (MW-4, MW-6, MW-7) 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 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 Figure 2 shows the location of the well pairs used for calculating vertical groundwater ' gradient in this report MW-4/MW-104, MW-6/MW-106, and MW-7/MW-107 Tables 1 & 2 show a Summary of Water Level and Gradients Slope and Bearing and Table 3 shows the calculated vertical gradients The infonnation used in the calculations is shown below tVerticalg radient calculation formulas are as follows • vertical correction for gradient [(gw gradient slope) x (distan(,e) = vertical correction] • vertical head [(head of deep well) - (head of shallow + correction) = vertical head] ® vertical gradient [(vertical head) / (vertical distance) =vertical gradient] 1 For the September 26, 2003 event, the vertical gradient for the MW-4/MW-104 pair was negative (downward) In well pairs MW-6/MW-106 & MW-7/MW-107 the vertical ' gradient was positive (upward) The trend of a negative gradient m MW-4/MW-104 and a positive or no gradient in the other pairs is consistent with the historical data It is noted that the vertical distance to the deep well screen in the MW-4/MW-104 well pair is double the distance of the other two well pairs, which may contribute to the apparent opposite flow direction ' 1.2 Groundwater Sampling Procedure ' 4n September 26, 2003, Del-Tech Geotechnical Support personnel arrived on-site, opened the wells and measured the depth to water with an electrically actuated sounding tape The water level reading was recorded to an accuracy of 0 01 foot In wells where free-floating ' product is suspected, a clear disposable bailer is used to gauge the interface No free- floating product was observed during this monitoring event Stagnant water in the well casing was purged using a dedicated Wattera pump as recorded in the field logs (Appendix Q The rate of well purging was monitored The wells were purged of at least three casing volumes until the gioundwater parameters (temperature,