Lake St. Clair originally was a 591 acre lake located west of the Detroit Lakes. In about 1915 the lake was drained to its present size of 140 acres because of the “awful stench” is presented to the local residents. This was caused by more than seventy years of untreated sewage from the City of Detroit lakes. A modern sewage treatment plan was constructed in 1976 which reduced phosphorus loadings to St. Clair by approximately 90%. The City continuous to discharge treated effluent wastewater on the north side of the lake.
St. Clair is prone to annual winterkill episodes and therefore does not support game fish populations. There is no public access on the lake. The lake is, however, heavily used by waterfowl. A local zoning ordinance was placed on the lake restricting the used of motorized watercraft, an effort to help preserve the efficacy of an alum treatment.
Two ditches bring water to St. Clair, including much of the City of Detroit Lakes stormwater runoff. A natural outlet from Long Lake enters from the West, which contributes only minor amount of water and nutrient load. St. Clair discharges to the southwest via Becker County Ditch 14 to the Pelican River, entering Muskrat and Sallie Lakes. Additional nutrients are picked up from the partially drained wetland which Ditch 14 flows through to the Pelican River.
Lake bottom sediments up are up to 16 feet thick in portions of the lake and are thought to be caused by the lake’s history of receiving sewage prior to modern wastewater treatment.
Developed land accounts for 43% of the land area draining to the lake. Other land uses are comprised of grassland (16%), forests (12%), cropland (13%), and wetlands (16%).
The Pelican River Watershed District applied aluminum sulfate (ALUM) to Lake St. Clair in October 1998. This treatment was a phased approach intended to reduce unacceptable phosphorus level in Lake Sallie. Following the ALUM treatment, in-lake phosphorus concentrations were reduce by over 50% from 131ppb to 72ppb with similar reduction in orthophosphate. Phosphorus level began to trend upward beginning in the early 2010’s showing that the ALUM treatments effectiveness had began to wear and that another dose will be required to maintain phosphorus level below 80ppb.
2016 had the lowest water clarity and on of the highest nutrient levels (second to 2015) recorded since the alum treatment in 1998. There has been a steady decline in water quality beginning in 2010, which is consistent with the 10-year life expectancy of an alum treatment. Additional alum treatments will be explored to determine their effectiveness of further reducing internal loading.