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GeologicalTecluucsl�cc Page 3 Groundwater Monitoring Report Project No 724 2 May 15, 2003 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 I & 2 show a Summary of Water Level and Gradients Slope and Bearing and Table 3 shows the calculated vertical gradients The information used in the calculations is shown below ' Vertical gradient calculation formulas are as follows • vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] ' • vertical head [(head of deep well) - (head of shallow + correction) = vertical head] • vertical gradient [(vertical head) / (vertical distance) = vertical gradient] For the March 13, 2003 event, the vertical gradient for the MW-4/MW-104 pair was negative (downward) In well pair MW-6/MW-106 the vertical gradient was essentially zero or horizontal flow conditions In well pair MW-7/MW-107 the vertical gradient was positive (upward) These data are consistent with previous events, although the MW- 6/MW-106 well pair usually exhibits a positive vertical gradient 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 1.2 Groundwater Sampling Procedure 1 On March 13 2003 Del-Tech Geotechnical Support personnel arrived on-site, opened the p p 1 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 C) The rate of well purging was monitored The wells were purged of at least three casing volumes until the groundwater parameters (temperature, conductivity, and pH) had stabilized (Appendix C) This indicated that water representative of actual aquifer conditions was entering the well Groundwater parameter stabilization was characterized by three successive readings within 10% van ance