Agenda - Council Work Session - 02/23/2021

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aquifer generally has moderate to low yield; wells completed within this aquifer may be capable of producing up to several hundred gallons of water per minute. Many wells within the LRRWMO utilize this source (MDNR, 2016), including some municipal wells. • Mt. Simon -Hinckley Aquifer — This aquifer underlies all of Anoka County and is composed of fine- and coarse -grained sandstone. Groundwater flow is generally south towards a cone of depression formed by pumping in Hennepin County. The aquifer has moderate to high yield, low vulnerability to contamination, and is used in the watershed for municipal drinking water supplies. The MDNR has placed restrictions on the placement of wells within the Mt. Simon in the Metropolitan Area. The Metropolitan Council completed the Regional Water Supply, Enhanced Groundwater Recharge, and Stormwater Capture and Reuse Study for the Northwest Metro Study Area in 2018. Groundwater modeling performed as part of the study estimates future impacts to local aquifers from continued development of groundwater sources, including up to 30 feet of decline in the Tunnel City-Wonewoc aquifer by 2040 that may limit the availability of groundwater resources in the future. Users of groundwater meeting certain use criteria are required to obtain a water appropriations permit from the MDNR; more information is available from: https://www.dnr.state.mn.us/waters/watermgmt section/appropriations/index.html Additional information about the aquifers within the watershed is available from the following sources: • Regional Hydrogeologic Assessment (RHA) of the Anoka Sand Plain (MDNR, 1993), available at: https://www.dnr.state.mn.us/waters/programs/gw section/mapping/platesum/rha asp.html • Anoka County Geologic Atlas, Part B — Hydrogeology (MDNR, 2016), available at: https://www.dnr.state.mn.us/waters/programs/gw section/mapping/platesum/anokcga.html • Metropolitan Council Water Supply Planning, available at: https://metrocouncil.org/Wastewater- Water/Planning/Water-Supply-Planning.aspx .. 1 Groundwater Recharge Recharge to groundwater occurs throughout the watershed. The local surficial geologic characteristics affect the rate, volume, and distribution of recharge. Water infiltrates most rapidly into sandy deposits and flows easily through sandy materials; clay deposits tend to slow and impede infiltration and subsurface flows. Relative to natural conditions, impervious surfaces (e.g., buildings, streets, parking lots) in developed areas have reduced the amount of open space and decreased the amount of land available to infiltrate runoff and recharge groundwater. Surficial aquifers usually have higher static water levels than deeper aquifers, indicating that water flows downward into the aquifer system and that surficial aquifers help recharge deeper aquifer systems. Deeper bedrock aquifers are recharged through bedrock valleys, leakage through confining layers, fractures in tills and confining layers, improperly constructed wells, and other areas where good hydraulic connections and unforeseen flowpaths exist with upper aquifer units. 2-15