ARCHIVED REPORTS_XR0007450 CASE 1

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' k4 KLEINFELDER 4 GROUNDWATER SAMPLING Groundwater samples were collected quarterly in 2002 in January, June, September and during this fourth quarter sampling event on December 13, 2002 The groundwater samples were collected from four onsite monitoring wells MW-1 through 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 round for each quarterly event, prior to purging and sampling of the wells The depth-to-water was measured in each well according to the protocol described in Appendix B, Section B-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 resulting groundwater elevations were 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 Water levels were measured prior to each of the 2002 quarterly sampling events The depths to ' water at the four wells, measuring from the north side of the nm of the PVC pipe in 2002 has ranged from 34 95 feet below top of casing (approximate ground surface) at MW-1 (January 2002) to 38 34 feet in MW-3 (September 2002) Groundwater elevations in 2002 have ranged- from angedfrom 1 34 feet at MW-2 (September 2002) to 4 73 feet from MW-4 (January 2002) In 2002 the groundwater flow direction has been consistently towards the southwest with a groundwater ' gradient ranging from 0 003 to 0 004 ft/ft (Table 1) The depths to water at the four wells for the fourth quarter 2002 ranged from 36 56 to 37 58 ft ' Groundwater elevations ranged from a high of 3 17 feet at MW-4 to a low of 2 10 feet at MW-2 Groundwater flow direction was calculated approximately to the southwest at a gradient of approximately 0 003 ft/f during the fourth quarter 2002 (Plate 2) 4 2 COLLECTION OF GROUNDWATER SAMPLES A total of four groundwater samples were collected from monitoring wells MWA through MW-4 during the fourth quarterly sampling event conducted in December 2002 The wells were purged and sampled using disposable bailers and as generally described in 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 petroleum odor, 18748 T02/ST03RO81 Page 7 of 12 ©2003 Klein€elder,Inc January 23,2003