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Geologccal Teclwics!nc Page 3 Groundwater Monitoring Report Project No 723 2 January 19,2004 ' 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-3/MW-201 Table 1 shows 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] Li Vertical head [(head of deep well) - (head of shallow + correction) = vertical head] ❑ Vertical gradient [(vertical head) / (vertical distance) = vertical gradient] ' For the November 26, 2003 event, the vertical gradient for the MW-3/MW-201 pair was 0 00 ft/ft , or no vertical gradient This was the third time that no vertical gradient was recorded at the site Previous calculations have revealed both positive and negative gradients but additional monitoring is needed to determine long-term trends 1.2 Groundwater Sampling Procedure On November 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 readings were recorded to an accuracy of 0 01 feet In wells where free-floating product is suspected, a clear disposable bailer is used to gauge the interface During this ' monitoring no free product was noted Stagnant water in the well casing was purged using a Waterra pump as recorded in the field logs (Appendix C) The rate of well purging was monitored The wells were purged of approximately three casing volumes and until the groundwater parameters (temperature, conductivity and pH) had stabilized (Appendix C) indicating that water representative of ' actual aquifer conditions was entering the well Groundwater parameter stabilization was characterized by three successive readings within 10% ' Before a sample was collected, the well's water level was allowed to recharge to at least 80% of the initial level The purge water was placed in a properly labeled 55-gallon DOT (Department of Transportation 17--H) approved container and temporarily stored on-site ' The dedicated Waterra. pump was used to collect each monitoring well sample Extreme care was exercised while transferring the sample into 40-m1 VOA vials preserved with ' hydrochloric acid All samples were checked for headspace bubbles, labeled, inserted into foam holders and placed into an ice chest cooled to 4°C for transport to the laboratory