ARCHIVED REPORTS_XR0007387 CASE 1

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KLEINFELDER 4. GROUNDWATER SAMPLING Groundwater samples were collected during the Second Quarter 2005 sampling event ` on May 27, 2005 The groundwater samples were collected from four onsite monitoring wells MW-1, MW-2, MW-3, and MW-4 at the General Mills facility (Plate 1) 4.1 MEASUREMENT OF WATER LEVELS In order to evaluate the groundwater gradient at the time of sampling, water level measurements were made in each of the four monitoring wells at the beginning of the sampling event prior to purging and sampling of the wells The depth-to-water was f measured in each well according to the protocol described in Appendix A, Section A-4 The depth-to-water measurements were converted to groundwater elevations with respect to a local benchmark by subtracting the depth to water measurements from the surveyed casing elevations The groundwater elevations were then used to calculate the direction of groundwater flow and gradient This information was then used to evaluate which wells represent upgradient and which wells represent downgradient water conditions The depths to water at the four wells, measuring from the north side of the rim of the PVC pipe, ranged from 38 01 feet below top of casing (approximate ground surface) at MW-1 to 39 16 feet in MW-2 Groundwater elevations during the first quarter 2005 sampling event ranged from a high of 1 87 feet at MW-4 to a low of 0 51 feet at MW-2 (Table 1) Groundwater flow direction was calculated to the southwest at a gradient of f approximately 0 004 ft/ft during the second quarter 2005 (Plate 2) r4.2 COLLECTION OF GROUNDWATER SAMPLES A total of four groundwater samples were collected from monitoring wells MW-1 through MW-4 during the Second Quarter 2005 sampling event, which was conducted in May 27, 2005 The wells were purged and sampled using disposable bailers and as generally d escribed I n K leinfelder's Protocol (Appendix A) A transparent disposable bailer was partially submerged into the groundwater prior to purging each monitoring well to assess the groundwater for a potential sheen and/or floating product No t petroleum odor, floating product or sheen was observed in perimeter monitoring wells MW-2, MW-3, and MW-4 A strong petroleum odor, sheen, and approximately 1/8 inch (0 012 f eet) of f loating p roduct was observed in the groundwater purged from MW-1 ' during this sampling event Copies of the monitoring well sampling logs for the Second Quarter 2005 are included in Appendix B 28209 T09/ST05R1323/DH Iv Page 6 of 12 ©2005, Klemfelder, Inc October 21, 2005