Dissolved Oxygen Investigation Coon Rapids Hydroelectric Redevelopment Project

The Coon Rapids Dam is located in Hennepin County, Minnesota, on the Mississippi River approximately four miles downstream from the City of Anoka and approximately twelve miles upstream from the downtown section of Minneapolis. The hydropower redevelopment at Coon Rapids will send between 1,000 and 8,000 cfs (the range of discharge for the turbines), which previously passed over the spillway, through the turbine units. The purpose of this project is to assess the impact of hydropower redevelopment on dissolved oxygen concentrations, as related to the survival and growth of fish. In order to satisfy this general goal, the following studies have been performed, and form the core of this report: measure D. O. and temperature upstream of the Coon Rapids Dam on August 25, 1987; measure D. O. and temperature at 12-20 locations over depth from the dam and river banks on ten dates in August and September 1987; measure the dissolved oxygen concentrations at three stations downstream of the abandoned powerhouse one day in January, February, and March; compare the D. O. measurements with those already obtained from the U. S. Geological Survey eight-year record period and evaluate the effectiveness of the various spillway sections as aerators.