Lake Okonoka
Funding Agency: U.S. Environmental Protection Agency, administered through the National Oceanic and Atmospheric Administration (NOAA)
Project Budget: $6,500,000
Start Date: August 2014
End Date: July 2020
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. Recognized as 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 island’s canals and lakes. Pumps were installed to circulate the water but were costly to maintain and operate, and they fell into disrepair.
Manipulation of the island's internal waterways contributed to the degradation of the wet-mesic flatwoods forest 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 lake with several forested islands, providing diverse terrestrial and aquatic habitat. However, the system was 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. SmithGroup 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.) Feasibility and preliminary design for habitat restoration at Lake Okonoka.
The hydrology assessment was a prerequisite to developing a 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 more than $7 billion annually.
Final engineering for Lake Okonoka involved developing plans for the fish passageways in and out of the lake, which include a road bridge over the connection between Lake Okonoka and Blue Heron Lagoon and a culvert connection from the lake to the Detroit River. These structures 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. Water level fluctuation in the lake is anticipated due to the free-flowing hydraulic connections to the river, which is known to go up and down with the cyclic change in water level associated with the entire Great Lakes system.
The road bridge opening to the Blue Heron Lagoon was completed in the spring of 2019. During this same time, water levels in the entire Great Lakes Basin rose to near record highs. Torrential, mid-April rains caused water in Lake Okonoka to over-top its banks, flooding the flatwoods forest, Woodside Drive, and most of The Strand. The unprecedented flood conditions persisted throughout the summer, stopping work on all remaining elements of the project including removal and restoration of Woodside Drive, finishing the wet meadow between the lake and flatwoods forest, and installing the 10’-square box culvert where fish passage between the lake and river was planned.
High water and frequent rain events delayed the culvert installation until the winter of 2020. With high water persisting, the project team worked during the spring of 2020 to develop temporary measures to restrict river water from entering Lake Okonoka, allowing the lake water to be pumped down enough to construct the remaining project elements. A water-filled, rubber bladder will serve as a temporary cofferdam at the 50’ wide bridged opening, and the box culvert will be equipped with a removable, stop log panel. After lowering the lake level, construction of the remaining project elements will follow, with anticipated completion by summer of 2020. Assuming water levels will recede to within the “normal” range sometime soon, the DNR will remove the temporary water control measures. Habitat monitoring will be conducted throughout 2020 and 2021 to document any early changes in the ecosystem resulting from the new habitat enhancements.
Project Output/Outcomes: This project included restoration of Lake Okonoka (45 acres) and the island’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 island’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 and around Belle Isle. The lake is now 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 are large enough to survive in the Detroit River. People will benefit from this project as well. The new bridge on Lakeside Drive and portage structure at Nashua Canal allow paddlers to easily pass from Nashua Canal, through the lake into Blue Heron Lagoon, and out to the river. In addition, birding, hiking and fishing experiences will be enhanced by the increase in fish and wildlife populations.
Project Data
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