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Geologccot Teckwccs Inc Page 3 Groundwater Monitoring Report Project No 724 2 March 11,2003 • 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 forinulas 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 December 20 2002 event, the vertical gradient for the MW-4/MW-104 pair was negative (downward) In well pairs MW-6/MW-106 and MW-7/MW-107 the vertical gradient was positive (upward) These data are consistent with previous events 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 On December 20, 2002, 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 groundwater parameters (temperature, ' conductivity, and pH) had. stabilized (Appendix Q This indicated that water representative of actual aquifer conditions was entering the well Groundwater parameter stabilization was chaiacterized by three successive readings within 10% variance iBefore a sample was collected, the water level was allowed to recharge to at least 80% of the initial level All purge water removed from the monitoring well was placed in a ' properly labeled 55-gallon DOT (Department of Transportation 17-H) approved container and is temporarily stored on-site