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1 Gtologual7erluiccslac Page 3 ' 3d Quarter 2005 Groundwater Monitoring Report Project No 507 2 . October 31, 2005 ' 10 in May 2001, the direction has been redorninantl to the northeast The site is quite close p Y to the San Joaquin River and tidal fluctuations may contribute to some of the observed changes 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 the vertical distance between the two measuring devices by the distance from the mrd-point between the top and bottom seal of the deep well (MW-109) and the mid- point between the groundwater elevation and the bottom seal in the shallow well (MW-9) ' • 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 piezometnc 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 cluster used for calculating the vertical groundwater gradient in this report, MW-9 and MW-109 Table 1 shows Summary of Water Level and Gradients Slope and Bearing, and Table 2 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 August 19, 2005 monitoring event a vertical gradient was calculated for the MW- 9/MW-109 pair The vertical gradient was negative (a downward direction) at 0 0045 ft/ft, and this is consistent with the historical negative gradients at the site 1.2 Groundwater Sampling Procedure On August 19, 2005, Don Light of Del-Tech mobilized to the site to conduct groundwater ' monitoring of the site's eleven monitoring wells Before sampling was attempted, the wells were sounded for depth to water and then a clear disposable bailer was used to determine if floating product was present No free product was noted for this event, however, white ' foamy water was noted in MW-9 The wells were purged of at least three well volumes of stagnant water using a dedicated Waterra check-ball assembly and i/2 inch tubing or centrifugal pump Purging continued until the temperature, conductivity, and pH of the