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k" KLEINFELDER f' 4 ACTIVITIES CONDUCTED Kleinfelder conducted the groundwater sampling for the fourth quarter 2002 groundwater monitoring. Kleinfelder measured water levels in all of the monitoring wells , and sampled the monitoring wells (MW-DIS-11s, MW-DIS-11d, MW-DIS-12, MW-DIS-13, MW-DIS- 14s, and MW-DIS-14d). 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. 4.1 MEASUREMENT OF WATER LEVELS In order to assess the groundwater gradient at the time of sampling, water level measurements were made in each of the 20 monitoring wells and 3 piezometers at the beginning of the sampling round, prior to purging and sampling of the wells (see the attached Record of Water Levels). 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 a surveyed benchmark by subtracting them from the surveyed casing l elevations. J 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 theoundwater monitoring e gr g w lls. Groundwater elevations for the monitoring wells ranged from —33.54 feet (MW-$d) to -34.19 feet (MW-13). A groundwater gradient and direction was calculated based on depth-to-water data collected from these wells on December 9, 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 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. 12280.MON/ST03R225 Page 6 of 12 2003,Kleinfelder,Inc February 5,2003