Whaletail Lake-South Basin Alum Treatment

Whaletail Lake (MDNR 27-018400) is located within the jurisdictional boundaries of Pioneer-Sarah Creek Watershed Management Commission (PSCWMC). The lake is considered having two distinct basins relative to the Minnesota water quality nutrient standards with the South basin (MDNR 27-018402) classified as a deep lake (156 acres; max depth 23 feet; & 66% littoral) and the North basin (MDNR 27-0180401) classified as a shallow lake (370 acres; max depth 10 feet; & 100% littoral). The lake was listed on the MPCA's 303(d) impaired list for aquatic recreation due to excessive nutrients (South basin-2006 & North Basin-2008). Whaletail Lake was included in the Watershed Restoration and Protection Strategies (WRAPS) and Total Maximum Daily Load (TMDL) study completed by the PSCWMC in 2017. The WRAPS/TMDL studies identified internal loading as comprising approximately 80% of the total phosphorus load affecting surface water quality of the Whaletail Lake-South basin and recommended an alum treatment to achieve the MPCA water quality standards. The goal of treating Whaletail Lake-South basin with alum is to reduce the phosphorus by at least 180 pounds/year to meet the load reductions identified in the WRAPS/TMDL report. The alum treatment will reduce internal P-load (381 pounds) to achieve in-lake water quality standards for at least a 20-year period. As a secondary benefit, improvements to the in-lake phosphorus concentration for the South basin would effectively reduce the phosphorus load to the North basin by 52 pounds/year. The estimated cost of the Whaletail Lake-South basin alum treatment project is $506,250. The project will be completed as a partnership between the PSCWMC (grant applicant) ($50,313), Three Rivers Park District (TRPD-project lead) ($29,363), and City of Minnetrista ($21,575). The PSCWMC is requesting $405,000 from CWF Project & Practices Grant Program with a 25% match ($101,250) of the requested funds shared among the three project partners.