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Section 2 2-16 Ramsey County Multijurisdictional Hazard Mitigation Plan | July 2012 difference in water level between wells in the Prairie du Chien-Jordan and wells in the Franconia Ironton- Galesville, which ranges from 20 to 80 feet (Fig. I), demonstrates the effectiveness of the St. Lawrence confining unit. The difference in a particular area can be estimated by comparing the two maps. The Franconia-Ironton-Galesville aquifer is little used in the county. In the northwestern part of the county the aquifer is used in a few multiple-aquifer wells drilled into the deeper Mt. Simon aquifer. EAU CLAIRE CONFINING UNIT The Eau Claire Formation consists of siltstone, shale, and silty sandstone and is about 60 to 110 feet thick. It has low hydraulic conductivity and thus hydrologically separates the Franconia- Ironton- Galesville aquifer from the Mt. Simon aquifer. MT. SIMON AQUIFER The Ml. Simon aquifer underlies all of Ramsey County. It is composed of fine- to coarse-grained sandstone with many thin beds of siltstone and shale in the upper part. and ranges in thickness from 250 to 330 feel. Nearly all high-capacity wells in the aquifer are located either in the south-central or the northwestern part of the county. Data on ground-water movement are very limited, but the pattern of flow in the Mt. Simon aquifer apparently differs greatly from the pattern in the overlying aquifers. The general movement of ground water is from east to west toward the cone of depression formed by the major pumping centers in Hennepin County. The location of the 650-foot contour is extrapolated from information compiled for the Hennepin County geologic atlas (Minnesota Geological Survey Atlas C-4, 1989). In general, the Mt. Simon aquifer has no hydraulic connection with cither the shallow ground-water system or the major streams. Much of the water in the aquifer is derived from leakage from the overlying aquifer system, although lateral movement from outside the county also occurs. The difference in the hydraulic head in the Franconia Ironton-Galesville aquifer and the Mt. Simon aquifer ranges from zero in the southeast to 175 feet (Fig. 1) in the west-central part of the county. By Roman Kanivetsky and Jane M. Cleland 1992. Prepared and Published with the Support of Ramsey Soil and WATER Conservation District, Ramsey County Board of Commissioners, Select Water Management Organizations, The Minnesota Department of Natural Resources, Division of Waters, and the Minnesota Environment and Natural Resources Trust Fund.