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} Geotogicaf?ecfini-s 2nc. Page 3 Groundwater Monitoring Report 1 Project No. 770.2 I January 10,2002 For the December 7, 2001 monitoringevent a vertical gradient was calculated f g or the MW- 5/MW-105 W-5/MW-105 pair. The vertical gradient was negative (a downward direction) and approximately 3 times greater magnitude (0.0012) than the horizontal gradient of shallow wells MW-1 through MW-3- (0.0004). The vertical gradients calculated for previous events are: negative on August 28, 2000, June 27 and September 19, 2001; and positive on December 29, 2000 and March 15, 2001. Similar to the historical lateral directions, the direction of groundwater in:the vertical plane also fluctuates at the site. The magnitude of vertical groundwater flow ranges from—0.0012 to—0.0236 in the negative direction. I 1.2 Groundwater Sampling Procedure On December 7, 2001 Don,Li ht of Del-Tech Geotechnical Support Services mobilized g pp ob ed to the site to conduct groundwater monitoring of the seven monitoring wells. Before sampling was attempted the wells were sounded for depth to water and then a clear 1 disposable bailer was used to determine if floating product was present. The wells were i t purged of at least three well volumes of stagnant water using a dedicated Waterra check-ball assembly and '/2 inch tubing: Purging continued until the temperature, conductivity, and pH of the groundwater stabilized (<10% variation between three 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 Waters 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 foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory. All non-disposable sampling equipment was decontaminated using a hot water washer and detergent before and between uses. Disposable gloves were used by the technician to collect all samples and were changed with each sample collection. A chain of custody document, listing all samples collected, accompanied the samples from field to laboratory, thereby 'providing a means to track their movement and insure their L integrity. All water purged from each monitoring well and not used as a sample, was placed in a 55 gallon DOT approved container, properly labeled and stored on site until its proper disposition can be arranged. Groundwater monitoring field logs are included in Appendix C. k