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GeolagI"I rteknlrs lKc Page 3 4'h Quarter 2004 Groundwater Monitoring Report Project No 507 2 February 22,2005 The following procedure is used to calculate vertical groundwater gradient • Determine the 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-109) and the nud- 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 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 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 December 2004 monitoring event a vertical gradient was calculated for the MW- 9/MW-109 pair The vertical gradient was negative (a downward direction) at 0 0060 ft/ft ' 1.2 Groundwater Sampling Procedure ' On December 29, 2004, 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 The wells were purged of at least three well volumes of stagnant water using a dedicated Waterra check-ball assembly and 1/2 inch tubing or centrifugal pump Purging continued until the temperature, conductivity, and pH of the groundwater stabilized (C10% variation in three consecutive readings), indicating that formation water representative of aquifer conditions was entering the wells These water quality parameters were measured at intervals of each well volume purged ' Once purging was complete, a water sample was collected from the Waterra tube Care was taken to minimize sample agitation Once the sample container was filled and capped, the bottle was inverted, tapped and checked for headspace bubbles The sample container was ' identified and labeled with a unique designation, inserted into a foam holder and placed into an ice chest cooled to 4°C for transport to the laboratory