LMRWMO WRAPS Internal Phosphorus Loading Control: Lake Augusta and Sunfish Lake
Projects and Practices 2016: Laws of MN 2015 First Special Session Chapter 2, Article 7, Section 7
This project targets internal phosphorus loading to the identified water resources. Using alum treatments, this project proposes to reduce internal phosphorus loading to Lake Augusta and Sunfish Lake by 252 lbs/year and 129 lbs/year, respectively.
LOCAL LEVERAGED FUNDS
Lake Augusta and Sunfish Lake are deep lakes located in the Lower Mississippi River Watershed Management Organization. Both lakes are approximately 40 acres in size and surrounded by watersheds with moderate to low imperviousness. Both lakes are included on the MPCA's 303(d) list as impaired for aquatic recreation due to excessive nutrients. Lake Augusta and Sunfish Lake were included in a watershed restoration and protection strategies (WRAPS) study and total maximum daily load (TMDL) performed from 2012 to 2014. The WRAPS study identified internal loading as the primary source of phosphorus to each lake and recommended in-lake alum treatments to improve water quality in each lake to achieve MPCA water quality standards. The goal of the Lake Augusta and Sunfish Lake alum treatments is to reduce internal phosphorus loading in each lake by at least 80 percent, resulting in phosphorus load reductions of 252 lbs/year in Lake Augusta and 129 lbs/year in Sunfish Lake. These reductions will meet the load reductions identified in the WRAPS and TMDL report and are essentially the only feasible options to achieve MPCA water quality standards in these lakes. The watersheds to these lakes are not densely developed and stormwater best management practices are already present, reducing phosphorus loading to the lakes from external sources. In addition to the alum treatment, the LMRWMO will implement a voluntary rain barrel program, a shoreline buffer survey on Sunfish Lake to identify potential locations for improvements, and targeted communication with residents to encourage buffer enhancement. These efforts will further reduce the phosphorus reaching the lake from external sources. Due to the very limited external load, alum treatment of these lakes is expected to be effective for 20 years or more. The Lake Augusta and Sunfish Lake alum treatment project will be completed in partnership with the Cities of Mendota Heights, Sunfish Lake, and local property owners.