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Geofagtca(Technirs Inc <br />Groundwater Monitoring Repoit <br />Project No 724 2 <br />November 13, 2001 <br />Page 3 <br />Vertical gradient calculation formulas are as follows <br />• vertical correction for gradient [(gw gradient slope) x (distance) = vertical correction] <br />• vertical head [(head of deep well) - (head of shallow + correction) = vertical head] <br />• vertical gradient [(vertical head) / vertical distance) = vertical gradient] <br />For the September 17, 2001 event, the vertical gradient for the MW-4/MW-104 pair was <br />negative (downward) In well pair MW-6/MW-106 the vertical gradient was positive <br />(upward) and of greater magnitude than the horizontal gradient These data are consistent <br />with previous events In well pair MW-7/MW-107 the vertical gradient was positive <br />(upward) and approximately one third the horizontal gradient The directions of these <br />gradients are consistent with past events <br />1.2 Groundwater Sampling Procedure <br />On September 17, 2001, Del -Tech Geotechnical Support personnel arrived on-site, opened <br />the wells, and measured the depth to water with an electrically actuated sounding tape The <br />water level reading was recorded to an accuracy of 0 01 foot In wells where free-floating <br />product was suspected, a clear disposable bailer was used to gauge the interface No free- <br />floating product was observed during this monitoring event <br />Stagnant water in the well casing was purged using a dedicated Wattera pump as recorded <br />in the field logs (Appendix C) The rate of well purging was monitored The wells were <br />purged of at least three casing volumes until the groundwater parameters (temperature, <br />conductivity, and pH) had stabilized (Appendix C) This indicated that water, <br />representative of actual aquifer conditions, was entering the well Groundwater parameter <br />stabilization was characterized by three successive readings within 10% <br />Before a sample was collected, the water level was allowed to recharge to at least 80% of <br />the initial level All water removed from the monitoring well and not used as a sample was <br />placed in a 55 -gallon DOT (Department of Transportation 17-H) approved container that <br />was properly labeled and is temporally stored on-site <br />A dedicated Wattera pump was used to collect each sample <br />Extreme care was exercised while collecting samples to prevent agitation of the water <br />contained in the bailer Water samples were transferred into 40-m1 VOA vials preserved <br />with hydrochloric acid in a manner that minimizes sample aeration during transfer of the <br />sample All samples were checked for headspace bubbles, labeled, inserted into foam <br />holders and placed in an ice chest cooled to 4°C for transport to the laboratory <br />The sampling technician, while collecting all samples, wore disposable gloves <br />