Agenda - Council Work Session - 10/20/2020 - Special

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Table 9 - Bedrock Aquifers reologlo ormati Hinckley Sandstone Age Primary 1LApproximate Hydrogeologi Designation hickness . Primary Regional Lithology Pre- Cambrian ' Aquifer Not Available Quartzose sandstone overlying the Precambrian bedrock Mt Simon Sandstone Middle Cambrian Aquifer -200 to 336 ft , Quartz sandstone that contains interbedded siltstone and very fine sand. Eau Claire Formation Middle to Upper Cambrian Confining -690 ft 0 to Fine grained sandstone, siltstone and shale. Wonewoc Sandstone Upper Cambrian Aquifer - 50 to 60 ft Very fine to very coarse grained Sandstone. Tunnel City Group Upper Cambrian Aquifer / Confining - 150 to 180 ft , Lower is massivebedded vefine ly ry to fine-grained sandstone; upper is coarse grained sandstone. St Lawrence Formation Upper Cambrian Confining - 38 to 59 ft Dolomitic siltstone with interbedded very fine grained sandstone and shale. Jordan Sandstone Upper Cambrian Aquifer - 85 to 100 ft Upward sequence of fine to coarser grained sandstone. 5.1.2.1 5.1.2.2 Jordan Aquifer The Jordan Aquifer is generally considered to be hydrologically connected to the Prairie Du Chien Unit. However, as evident from the geologic bedrock map (Figure 2 in Appendix D) the Prairie Du Chien Unit was either not deposited or has been entirely eroded through much of this area. The thickness and presence of this aquifer through this area is scarce and laterally disconnected. Where present, Within the City of Ramsey, the Jordan Sandstone thickness is minimal at around 20-30 feet and appears heavily eroded. Quaternary deposits directly overlay this unit and the Jordan Sandstone is likely recharged by these deposits. Wonewoc / Tunnel City Gra! F.; The Tunnel City Group and the underlying Wonewoc Sandstone (formerly known as the Franconia -Ironton -Galesville Aquifer) supply water for much of the Northwest Metro region. Presence and thickness of the Tunnel City is depicted on Figure 6 in Appendix D and for the Wonewoc on Figure 8 in Appendix D. Areas where the Aquifer is not present primarily occur within bedrock valleys where previous streams and surface water features carved away the bedrock unit. A large unconformity of the Wonewoc Sandstone is depicted within Anoka County where heavy erosion of this unit appears to have taken place prior to the deposition of the Tunnel City Aquifer. This area is depicted where the Wonewoc aquifer thickness thins or is not present (Figure 8 in Appendix D). Potentiometric surfaces of this units are depicted on Figures 7 in Appendix D for the Tunnel City and Figure 9 in Appendix D for the Wonewoc Sandstone Potentiometric surfaces were created by the Minnesota Geologic Survey and provide a rough estimate for water elevations for a proposed well within these units and their groundwater flow direction, FEASIBILITY STUDY -DRAFT RAMSY 154354 Page 14