Detroit River AOC - Lake Okonawa Habitat Restoration
Design: $389,692 (Federal - $319,692 Local Match - $70,000)
Final Engineering: $265,000
Funding Agency: NOAA
Design: August 2014
Final Engineering: October 2016
Construction: August 2017
End Date: December 2019
Belle Isle is positioned at the "gateway" to the Detroit River. Here, the river's water quality is at its best, clear and fast flowing from Lake St. Clair. In addition to being the City of Detroit's most popular open space, the island's unique, 200-acre, wet-mesic flatwoods forest along with its interconnecting lakes and canals provide a significant framework for fish and wildlife habitat. However, most of the island's internal waterways are isolated from the river and the Great Lakes. This project makes advancements in reconnecting Belle Isle's internal waterways to the river and restoring the wet-mesic flatwoods forest to enhance habitat for a great diversity of animal and plant species.
Water bodies on Belle Isle include three lakes, a lagoon and over two miles of canals, totaling 106 acres of open surface water. Historically, these waterways were connected to the Detroit River, providing aeration and circulation for fish habitat. In the 1950's, the waterways were closed off from the river, creating stagnant conditions and eliminating the ability for Great Lakes fish to migrate into the Isle's canal / lake system. Pumps were installed to circulate the water but are costly to maintain and operate and are no longer functioning.
Manipulation of the island's internal waterways has contributed to the degradation of the wet-mesic flatwoods community and Lake Okonoka. The canal system routes through the wet-mesic flatwoods community, which is rated according to the Heritage Methodology as "vulnerable to be imperiled globally and imperiled within the state". This rare plant community on Belle Isle is, by far, the largest remaining example in Michigan. The canal system also routes through Lake Okonoka, a linear-shaped lake with several forested islands providing a diversity of terrestrial and aquatic habitat. However, the system is blocked from flowing into the Blue Heron Lagoon and Detroit River at the lake's east end by a stoplog structure, which also precludes fish passage.
Project Scope: In late summer of 2014, FDR received Great Lakes Restoration Initiative funding from the National Oceanic Atmospheric Administration (NOAA) to conduct a two-part design project on Belle Isle. SmithGroupJJR was engaged to assist FDR in accomplishing the work outlined below.
1.) A hydrologic assessment and pre-design of Belle Isle's interconnected lakes / canals and wet-mesic flatwoods forest.
2.) A hydrologic assessment and pre-design of Belle Isle's interconnected lakes / canals and wet-mesic flatwoods forest.
The hydrology assessment was a prerequisite to developing a final design for Lake Okonoka's restoration and for further design work to improve the hydrology of the flatwoods forest. Significant positive recreational and economic impacts are anticipated as a result of these projects that will enhance southeast Michigan's quality of life and further strengthen the Great Lakes fishery worth $4-7 billion annually.
Final engineering for Lake Okonoka involved developing plans for the fish passageways, which include the road bridge over the connection between Lake Okonoka and Blue Heron Lagoon and the culvert connection from the lake to the Detroit River. These are designed and engineered in accordance with the Michigan Department of Transportation (MDOT) standards for construction.
The plans were issued for competitive bidding in August of 2017. Z Contractors, Inc. was selected to do the work and mobilized on-site the following month. Construction began by draining the lake to allow efficient excavation of deep pools and channels. These are designed to insure healthy space for fish movement regardless of any water level fluctuations in the lake. Some water level fluctuation is anticipated, because the lake will be on-line with the river once the hydraulic connections are complete.
Engineering for the road bridge and culvert is nearly complete, and construction of these structures is anticipated to begin before the end of 2018. Habitat monitoring will be conducted throughout 2019 to document any early changes in the ecosystem as a result of the new habitat enhancements.
Project Output/Outcomes: This project includes restoration of Lake Okonoka (45 acres) and the isle's south, nearshore area (3 acres). Lake Okonoka's enhancements combined with the recent opening of Blue Heron Lagoon (41 acres) to the Detroit River will total 89 acres of calm spawning and nursery habitat for Great Lakes fish protected by a narrow landmass. The project's completion could lead to further restoration work throughout the i sle's forested wetland and internal water bodies, totaling over 280 acres of restored habitat for fish and wildlife within a dense urban area.
A variety of habitat design elements are incorporated to provide multiple niche habitats in support of existing fish and wildlife species. These include:
- 3,800 linear feet of deep channel excavation for fish passage through Lake Okonoka
- 3.2 acres of deep water pool excavation within Lake Okonoka
- 1.5 acres of mudflat creation for shorebirds
- .18 acres of spawning bed creation
- 45 tree snags and basking logs
- 2 acres of wet meadow for pollinators and herpetofauna passage between the flatwoods forest and Lake Okonoka
Making Lake Okonoka more accessible to spawning fish is a major step in improving fish habitat at Belle Isle. The lake will be linked to Blue Heron Lagoon on one end and the Detroit River on the other, allowing Great Lakes water and fish to pass freely. Lake Okonoka will likely become a high-quality haven for young fish to find shelter until they're large enough to survive in the Detroit River. People will benefit from this project as well; the new bridge on Lakeside Drive will allow paddlers to easily pass between the lake and Blue Heron Lagoon.
Lake Okonoka and the Blue Heron Lagoon are a new passage for Great Lakes water and fish.
The wet-mesic flatwoods forest includes many vernal pools providing rich herpetofauna habitat.
Lake Okonoka becomes connected to the Detroit River.
Lake Okonoka becomes connected to the Detroit River.
Construction began by draining the lake in preparation for excavating channels and deep pools in the fall of 2017.