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• 1 FIELD ACTIVITIES On September 25, 1998, Kleinfelder collected groundwater samples from three monitoring wells at the site. Mr. Doug Heard of our Stockton office did the sampling. 1.2 Measurement of Groundwater Levels Upon arrival onsite, all wells were opened and allowed to equilibrate. After approximately 30 minutes, the depth to groundwater was measured in the three wells using a conductivity-based water level indicator. The water level indicator was cleaned prior to use in each well to reduce the potential for cross-contamination. Measurements were made to the surveyed mark on the north rim of the monitoring well PVC casings. Groundwater depth measurements were converted to groundwater elevations. These elevations were plotted as shown on Plate 1, Groundwater Elevation Map. Table 1 presents a summary of water level measurements. The groundwater gradient and flow direction were calculated from the groundwater elevation data and indicates the groundwater is flowing in a southerly direction with a gradient of 0.031. Previous groundwater gradients and directions were plotted graphically and presented in a Rose Diagram as shown on Plate 2. This plot shows the overall direction and magnitude of the gradient and a mean groundwater direction. i 1.3 Collection of Groundwater Samples Following obtaining groundwater depth measurements, Kleinfelder collected samples from the three wells at the site. During the purging, field parameters such as temperature, pH, and conductivity were monitored. Copies of the Purge Characterization and Sample Log Sheets are presented in Appendix A. Groundwater samples were collected from these wells, and the sampling protocol for each monitoring well was as follows: + The volume of water in gallons standing in the well was calculated by subtracting the depth-to-groundwater measurement from the known depth to the well bottom and multiplying by the cross-sectional inside area of the well casing. • A transparent single-use disposable bailer was lowered approximately half-way into the surface of the water standing in the well and then withdrawn to check for a petroleum layer or sheen on the water. • A minimum of three well volumes of water was then purged from each well using a submersible pump. The pump was decontaminated between each well and new tubing was used for each well. Samples were collected after purging by decanting samples from the disposable disposable bailer directly into bottles provided by the analytical laboratory. s 40-327301/4018RO51 3 Copyright 1998 Kleinfelder,Inc. KLEINEELDER 790 Chadbourne Road, Suite D. Fairfield CA 94,585-964 3 (707)429-4{70 (707) 429-4162 fax