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1' Gjeolog:caCTechnws Inc Page 3 Groundwater Monitoring Report Project No 724 2 April 11,2001 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 March 15, 2001 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) and approximately double the magnitude of the horizontal gradient These data are consistent with the January 2001 event 1.2 Groundwater Sampling Procedure On March 15, 2001, Del-Tech Geotechnical Support personnel arrived on-site, opened the I 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 tempot ally stored on-site A dedicated Wattera pump was used to collect each sample Extreme care was exercised while collecting samples to prevent agitation of the water contained in the bailer Water samples were transferred into 40-ml VOA vials preserved with hydrochloric acid in a manner that minimizes sample aeration during transfer of the sample All samples were checked for headspace bubbles, labeled, inserted into foam Iholders 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