Normandale Lake is a shallow, 100-acre lake located along Nine Mile Creek in Bloomington, Minnesota. The lake is an important amenity within Normandale Lake Park, which includes a popular trail around the lake and an amphitheater. Poor water quality, frequent algal blooms, and an abundance of invasive curly-leaf pondweed and other aquatic plants in Normandale Lake prompted strong public support for improvements. A 2017 study conducted by Barr for the Nine Mile Creek Watershed District (NMCWD) concluded that internal phosphorus loading and the presence of dense aquatic vegetation, specifically curly-leaf pondweed, were degrading water quality and the health of the aquatic communities. A 2018 fishery survey identified a large population of carp, a bottom-feeding fish that stirs up lake bottom sediments and contributes to poor water clarity. To fix the problems, the NMCWD has embarked on a holistic lake management program that includes drawing down the water to freeze the lake bottom sediments and kill invasive curly-leaf pondweed, treating with alum to prevent the internal release of phosphorus from lake bottom sediments, and tracking carp movement for future management.
In late-summer of 2018, the NMCWD began drawing down the lake by pumping and installing a permanent bypass pipe. With Nine Mile Creek flowing through the lake, the full drawdown of water levels posed a significant challenge. The lake was fully drawn down by early-November, and by mid-February 2019 the top 15-24 inches of lake sediment were frozen. The effectiveness of the drawdown in reducing curly-leaf pondweed will be assessed throughout the summer of 2019; preliminary results indicate a significant decrease in the presence of curly-leaf pondweed throughout the lake. The NMCWD also conducted an alum treatment in spring 2019 to prevent internal loading from phosphorus in the lake bottom sediments. The DNR restocked the lake with fish in the spring of 2019 in hopes of re-establishing the population of predator fish, and our client conducted a fishery population survey and carp tracking.
Senior Water Resources Scientist
Vice President Senior Water Resources Engineer
Vice President Senior Environmental Scientist
Water Resources Engineer