4.12 Groundwater

Goal 12 - Groundwater

Protect and maintain existing groundwater flow, promote groundwater recharge and improve groundwater quality and aquifer protection.

Discussion

Maintenance of groundwater recharge is important in the Minnehaha Creek subwatershed to maintain baseflow in the Creek and hydrology to the groundwater-fed discharge or combination wetlands as well as to recharge aquifers that supply public and private water wells.  Springs and seeps in the Mississippi Gorge are also important groundwater resources in this subwatershed.  Development, with the associated creation of new impervious surface, increases the volume of stormwater runoff and reduces the amount of stormwater that naturally percolates into the soil to recharge groundwater. 

Increased infiltration is desirable for two primary reasons: to reduce the amount of pollutant loading into Minnehaha Creek, the lakes and wetlands, and to protect the hydrology of high-value groundwater resources such as the springs and seeps and wetlands.  Much of the subwatershed has at least moderate infiltration potential.  Requiring new development and redevelopment to infiltrate some of the new stormwater generated would reduce new volumes downstream and help reduce future erosion in streams and channels; minimize new pollutant loading that would have been conveyed by that stormwater; and help maintain groundwater levels, preserving wetlands. 

Some parts of the subwatershed are areas of aquifer sensitivity or are drinking water wellhead protection areas, where care should be taken when infiltrating stormwater.  Proper design of infiltration practices is necessary to avoid groundwater contamination.  Other land use practices such as the use of private water wells or individual sewage treatment systems should be monitored to prevent contamination of groundwater resources.

Groundwater management in the Minnehaha Creek subwatershed will focus on increasing the amount of infiltration in the subwatershed and monitoring flow at high-value groundwater resources such as Camp Coldwater Spring.

Desired Outcomes:  Maintain function of existing groundwater flow, assist in the protection of drinking water supply, no degradation in surficial groundwater quantity or quality, protection of high-value groundwater resources. 

Metrics:

  • Acre-feet volume abstraction
  • Surficial groundwater levels and parameters

Goal 12.1 - Minnehaha Creek

Protect and maintain groundwater recharge and groundwater quality.

Actions

  1. Amending existing or establish new District rules requiring abstraction of the first one inch of rainfall on new permitted development and redevelopment. 
  2. Establish new District rule requiring an additional level of analysis and review of permitted development and redevelopment where there is a potential to adversely impact groundwater connected to a surface water feature.
  3. Require pretreatment of stormwater discharged to wetlands or infiltration areas in the in the areas of high aquifer sensitivity.
  4. Coordinate stormwater and groundwater management within identified drinking water management areas and wellhead protection areas with city and private wellhead protection plans.
  5. Develop infiltration strategies appropriate to wellhead protection areas and areas of groundwater sensitivity.
  6. Work cooperatively with Hennepin County, the Minnesota Department of Health, and other agencies charged with managing individual sewage treatment systems and private and public groundwater wells to assess the potential impacts of surface water management practices on groundwater quality.
  7. Provide assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new impervious surface and provides for increased infiltration.
    1. Develop and distribute model ordinances and design standards that incorporate low impact design principles.
    2. Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
  8. Identify a network of surficial aquifer monitoring wells across the entire Minnehaha Creek watershed, monitor groundwater levels and groundwater quality, and if change is detected identify strategies for addressing that change.

Goal 12.2 - Minnehaha Creek

Protect and maintain groundwater flow.

Actions

  1. Identify base level flow in Minnehaha Creek, monitor for trends, and if change is suspected identify strategies for addressing that change.
  2. Continue to monitor groundwater flow at Camp Coldwater Spring and monitor activities within its groundwatershed for potential impacts to the historic spring.