Lake Winona TMDL

The Clean Water Act (CWA) requires states to publish, every two years, an updated list of streams and lakes that are not meeting their designated uses because of excess pollutants. The list, known as the 303(d) list, is based on violations of water quality standards and is organized by river basin. For each pollutant that causes the failure of a water body to meet state water quality standards, the CWA requires the MPCA to conduct a Total Maximum Daily Load (TMDL) study. A TMDL study identifies both point and nonpoint sources of each pollutant that fails to meet water quality standards. Water quality sampling and computer modeling determine how much each pollutant source must reduce its contribution to assure the water quality standard is met. The Minnesota Pollution Control Agency (MPCA) is the state agency responsible for protecting Minnesota’s water quality. The TMDL process involves four phases: 1) assessment and listing, 2) TMDL study, 3) implementation plan development and implementation, and 4) effectiveness monitoring.

Following the determination of excess nutrient impairment for Lake Winona as measured by in-lake concentrations of phosphorus, chlorophyll a and water clarity, a TMDL plan was prepared in 2010 that will result in an allocation of nutrients allowed for all sources within the watershed of Lake Winona. The city of Alexandria, Alexandria Lake Area Sanitary District (ALSAD) and non-point source locations are anticipated to be affected by the implementation plan for waste load reductions. It is expected that the restoration of Lake Winona will be challenging and take a relatively long period of time. Final approval of the TMDL and other related studies is pending with an unknown timeframe for approval. The responsibility for the reduction goal for mercury on the remained of impaired lakes lies with the federal government as over 90% of the mercury deposition in the state originates beyond the boundaries of Minnesota.

While progress has been made in some areas toward improving water quality as point source discharges of conventional pollutants have been drastically reduced, the concerns associated with the proposed phosphorus limits have presented legal and economic impact concerns. Decisions regarding responsibilities and requirements are being studied with no absolute resolution to date.

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