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' G eafog tca(Technws Inc Page 3 Groundwater Monitoring Report Project No 724 2 August 20,2001 1 Vertical gradient calculation formulas are as follows ' • vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] 6 vertical head [(head of deep well) - (head of shallow + correction) = vertical head] vertical gradient [(vertical head) /vertical distance) = vertical gradient] For the June 21, 2001 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 positive (upward) and ' of greater magnitude than the horizontal gradient These data are consistent with previous events In well pair MW-7/MW-107 the vertical gradient was positive (upward) and approximately equal to the horizontal gradient The directions of these gradients are consistent with past events 1.2 Groundwater Sampling Procedure On June 21, 2001, 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 was suspected, a clear disposable bailer was 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% Before a sample was collected, the water level was allowed to recharge to at least 80% of the initial level All water removed from the monitoring well and not used as a sample was placed in a 55-gallon DOT (Department of Transportation 17-H) approved container that was properly labeled and is temporally stored on-site I� A dedicated Wattera pump was used to collect each sample Extreme care was exercised while collecting samples to prevent agitation of the water f' contained in the bailer Water samples were transferred into 40-m1 VOA vials preserved with hydrochloric acid in a inanner that minimizes sample aeration during transfer of the 4 sample All samples were checked for headspace bubbles, labeled, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory The sampling technician, while collecting all samples, wore disposable gloves f��