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CeofogicafTechnecs 2ne Page 2 ' Groundwater Monitoring Report Project No 507 2 March 12, 2001 A groundwater gradient was calculated for the event and found to be flowing N36°E at 0 003 ft/ft Gradient direction for the January 2001 monitoring event is shown in Figure 2, and the historical groundwater directions and gradients are shown in Figure 3, Groundwater Gradient Rose Diagram The groundwater elevation data are summarized in Table 1, Appendix A The groundwater gradient is relatively flat and the direction of groundwater has varied during the course of the investigation As evident in Figure 3, groundwater has a strong bifurcated flow regime, trending predominantly to the southwest or northeast at approximate 180-degree direction reversal The site is quite close to the San Joaquin River and tidal fluctuations might be responsible for the observed changes in groundwater direction 1.2 Groundwater Sampling Procedure On January 5, 2001, Don Light of Del-Tech mobilized to the site to conduct groundwater monitoring of the eight existing monitoring wells Before sampling was attempted the wells were sounded for depth to water and then a clear disposable bailer was used to determine if floating product was present The wells were 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 (C10% variation between three readings), indicating that formation water representative of aquifer conditions was entering the wells These water quality parameteis were measured at intervals of each well volume purged ' Once purging was complete, a water sample was collected from the Waterra 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 Iabeled with a unique designation, inserted into a foam holder 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 ' Ac pain 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 integrity • i