4.3 Water Quality
Goal 3 - Water Quality
Preserve, maintain and improve aesthetic, physical, chemical and biological composition of surface waters and groundwater within the District.
The HHPLS used an extensive public input process to establish water quality goals for the primary receiving waters in the District, focusing primarily on identifying target total phosphorus concentrations. This plan identifies those plus additional goals related to water quality. This plan sets forth a set of actions the District will undertake to reduce pollutant loading in the subwatershed and achieve and maintain water quality goals. The achievement of these water quality goals is not only necessary to meet state and federal water quality requirements and to prevent future TMDLs, but also to meet this plan’s ecological integrity goals.
Lake Minnetonka is a complex system of bays and channels. Modeling has been limited to individual bays, and there is an incomplete understanding of the dynamics of the lake. A whole-lake model is needed to accurately model water quality that takes into account the relationships between the bays.
Desired Outcomes: Achievement of in-lake nutrient concentration goals through achievement of nutrient loading reductions.
- In-lake nutrient concentrations/Trophic State Index Scores (TSI) for Lake Minnetonka bays and the lakes of the subwatershed
- Nutrient loading goals (lbs) for Halsteds, Jennings, and Stubbs Bays
Goal 3.1 - Lake Minnetonka
Achieve in-lake total phosphorus concentration goals as identified in this plan.
- Conduct diagnostic studies of internal or unknown phosphorus loading in Jennings Bay, Stubbs Bay, and Halsteds Bay, prepare feasibility studies, and implement improvements to reduce internal or unknown loading.
- Consider amending existing or establishing new District rules requiring greater than 50 percent phosphorus removal on new permitted developments within the Lake Minnetonka subwatershed.
- Develop a whole-lake water quality model of Lake Minnetonka.
- Provide assistance to LGUs and developers to foster low impact development and redevelopment that minimizes new phosphorus and sediment loading.
- Develop and distribute model ordinances and design standards that incorporate low impact design principles.
- Sponsor educational opportunities for LGU staff, developers, elected and appointed officials and other interested parties to provide practical information and opportunities for sharing experiences.
- Promote the general application of BMPs across the subwatershed.
- Consider developing a small grant program to provide financial assistance to property owners desiring to retrofit their property with BMPs to reduce phosphorus and sediment loading.
- Continue regular water quality monitoring in the lakes to assess progress toward achieving the in-lake phosphorus goals.
- Require LGUs to maintain or reduce phosphorus loading from developed uses as set forth in Section 5.6.1 of this plan within 10 years.
- Provide education and training opportunities, technical and planning assistance for property owners and LGUs on methods to reduce phosphorus and sediment loading by incorporating BMPs into landscaping, infrastructure maintenance, and reconstruction.
Goal 3.2 - Lake Minnetonka
Prevent degradation of existing water quality in other Lake Minnetonka Bays and lakes in the subwatershed.
- Obtain baseline water quality data where none is available and update every three years.
- Develop a water quality index which encompasses the District’s broader definition of water quality.
Goal 3.3 - Lake Minnetonka
Achieve and maintain other state lake water quality standards including >1.4 m Secchi clarity and 14 ug/L chl-a for deep lakes, and >1.0 m Secchi clarity and 20 ug/L chl-a for shallow lakes.
- Achieve and maintain in-lake total phosphorus goals.
- Manage aquatic vegetation in accordance with vegetation management plans that take into account water clarity goals.
Goal 3.4 - Lake Minnetonka
Minimize pollutant loading contribution to Lake Minnetonka from upstream subwatersheds and Classen Creek.
- Meet the water quality goals for subwatersheds and water resources upstream of Lake Minnetonka.
- Assess sources and potential reductions of Classen Creek sediment and nutrient loading as part of the Stubbs Bay Internal Load Management proposed project.
- Inspect erosion-prone areas Classen Creek at least annually to identify new erosion areas,
- Work cooperatively with the City of Orono to repair identified erosion in Classen Creek and to prevent future erosion and sediment transport.
- Continue to monitor water quality in Classen Creek.