Once construction of each wetland is complete there will be ongoing regular maintenance and periodic capital improvement expenses that are necessary for the wetland to continue to function as intended.
The plants in the Cullen Park and Grassy Island wetlands will be selected based on certain qualities, such as ability to absorb phosphorous, and they will be planted after construction is complete. This vegetation will need to be managed just like the vegetation in any garden does. This can include such things as mowing, thinning, replanting, and changing the vegetation types.
There is a limit to how much phosphorous a plant can store. Once this limit is reached, they stop removing phosphorous from the water or sediment allowing it to pass straight through the wetland. For the wetland to continue functioning well plants that have reached their limits need to be removed and replaced.
Like perennials in a garden, many of the plants will die off each fall and regrow in the spring. When they die off, they decompose in the water. As they decompose, they release stored phosphorous back into the water supply. This is one of the reasons no wetland can have an annual 100% efficiency. The decomposition process also creates the noxious odor associated with wetlands.
INVASIVE AND AGGRESSIVE SPECIES MANAGEMENT.
Phragmites and American Lotus are two plant species that are prevalent in the local areas. Once they are established, they can be virtually impossible to control. ODNR, MetroParks Toledo, The Nature Conservancy, and the City of Toledo have all been unable to prevent the establishment and spread of Phragmites in the areas they manage.
These wetlands will be constructed in a densely populated urban environment. One will be on the north side of Cullen Park Causeway and one will be on the south side. Cullen Park and the Causeway are prone to litter. The wetlands built around them will be no different. This litter will need to be removed on a regular basis.
These wetlands are also being built in the open waters of the Maumee Bay. During high northeasterly wind events, the force of the waves will throw drift wood, including full size tree trunks, onto the outside walls of the wetlands. It will also get stuck in the culverts that allow the water to flow into and out of the wetlands. Heavy equipment will need to be used to remove this debris.
In Toledo mosquitoes are monitored and managed by the Toledo Area Sanitation District.
TASD monitors mosquitoes because it needs “to determine whether the population is under control and whether mosquito born diseases such as West Nile Virus and LaCrosse Virus are present in the population.” Wetlands are one of the breeding habitats that TASD routinely monitors and treats.
The budget for mosquito control in 2021 is almost $4 million. This cost is assessed against homeowners and is included in their real estate tax bill. Property owners in Toledo are already paying to control the existing mosquito problems in their neighborhoods. They neither need nor want new mosquito breeding grounds built to increase the problem they are already paying to address.
For more information about wetland mosquito breeding and its impacts, including mosquito borne diseases, click Here.
PERIODIC AND COSTLY CAPITAL IMPROVEMENTS
The Grassy Island and Cullen Park wetlands are being engineered and designed with different levels to simulate a natural wetland. However, as the lake levels adjust, the wetlands will not naturally adapt to the new levels. They will need to be redesigned and engineered to function at the new level.
To illustrate, the wetlands will have a sedimentation zone, which is a shallow area designed to capture the sediment that settles out as the water slowly flows over it. To function properly this zone should be 6 to 18 inches below the water line.
As initially designed, the Cullen Park wetland sedimentation zone was set at an elevation of 572 feet. For the sedimentation zone to function properly, the lake level needs to be 572.5 to 573.5 feet. The following is a table of average annual water levels from 1940 to 2020. The numbers in red are the years that a sediment zone of 572 feet would have been above the water line, dry and unable to function.
As soon as the currently high water levels return to the more typical levels, the wetland will need to be recontoured. This means vegetation will need to be removed, the top layers of the sediment and possibly other zones removed, layers reformatted and shaped, and the vegetation replanted.
We don’t have estimates of these costs, but as anyone who has done remodeling knows, it is often more expensive and time consuming to remodel something than it was to build it in the first place.
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