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I kNj KLEINFELDER i 1 I I ' 4 ACTIVITIES CONDUCTED t' Kleinfelder supervised the activities conducted for the February2002 groundwater monitoring. I; Del-Tech Geotechnical Support Services of Oakdale, California measured water levels in, and sampled the existing monitoring wells (MW-DIS-1, MW-DIS-2, MW-DIS-4, MW-DIS-7s, MW- DIS-7d, MW-DIS-9, MW-DIS-Ils, MW-DIS-11d, MW-DIS-12, MW-DIS-13, MW-DIS- 14s, MW-DIS-14d, SVE-North, SVE-South, NPI-70', NP1-80', and NPI-90'). All of the wells were previously surveyed by Kjeldson, Sinnock, Neudeck, Inc. (KSN, Inc.) of Stockton, California so groundwater gradients could be calculated. Data obtained from the wells was used to evaluate groundwater flow, groundwater impacts and the need for additional assessment. i 4.1 MEASUREMENT OF WATER LEVELS j In order to assess the groundwater gradient at the time of sampling, water level measurements I were made in each of 17 monitoring wells at the beginning of the sampling round, prior to purging and sampling of the wells. The depth-to-water was measured in each well according to the protocol described in Appendix A, Section A-4.1. The.depth-to-water measurements were then converted -to relative groundwater elevations with respect to mean sea level or a local benchmark by subtracting them from the surveyed casing elevations. The resulting pertinent groundwater elevations were used to assess the direction of the groundwater flow and gradient at the time of sampling. This information was then used to assess which wells represent upgradient and which wells represent downgradient groundwater conditions. See Table 1 for the groundwater elevation data. Plates 2 shows the location of the groundwater monitoring wells. Groundwater elevations for the monitoring wells ranged from —30.11 feet (MW-DIS-7s/d) to -30.82 feet (MW-DIS-13). A groundwater gradient and direction was calculated based on depth-to-water data collected from these wells in February 2002, and by data collected during a survey produced by KSN Inc. on February 14, 2002. The groundwater flow direction is estimated to be towards the southeast at a f relatively flat gradient of approximately 0.0005 ft./ft. A groundwater contour map is included as ` Plate 3. In areas of flat groundwater gradients such as this site, groundwater flow directions may significantly fluctuate due to rainfall, groundwater recharge, groundwater pumping, etc.. Therefore, changes in groundwater flow directions may vary at this site with time, however, past data consistently has suggested a similar groundwater gradient and flow direction. I 12280.MON/2002R394 Page 7 of 15 { ®2002,Kleinfelder,Inc May 10,2002 I