Bridge culvert could fix Mississippi River channel problem on Grey Cloud Island
Grey Cloud Channel is stagnant and choked with milfoil. Zebra mussels have also taken hold and the fish population, and number of species, has gone down.
"First fill," the road from the St. Paul Park mainland to Grey Cloud Island Township on County Road 75, is blocking the water from a Mississippi River side channel.
Getting water from the north side of first fill into the channel to move the weeds and mussels out, revitalize fish populations and open it to boating may be harder than it appears.
Around 1920, a wooden bridge was built from the township to the mainland. The best solution to getting the water moving again, officials have concluded, is to return to the bridge concept.
But water level, before the Hastings Lock and Dam opened in 1930, was much lower than it is today. When the wooden bridge was no longer safe, several small culverts were put in and filled with dirt and gravel.
During record flooding in 1965, township officials needed an immediate solution to keep flood water from topping the road, isolating the township and halting the hauling of sand, gravel and limestone from Shiely mines. So material from the mines was used to raise the road.
Over time, the culverts filled with debris. Residents along the channel said water was moving, though very slowly, until about 10 years ago when it became completely blocked.
The deterioration was quite rapid, according to township resident Denny Hanna who also serves as one of the members of the South Washington County Watershed District.
Nearly the entire township is located in the Critical River Area and within the Mississippi National River and Recreation Area. Jurisdictions include the National Park Service, Minnesota Department of National Resources, Corp of Engineers and Washington County.
County officials have been sympathetic to the channel problem, but first fill improvements are not in the county's transportation plan.
The DNR, Park Service and Corps of Engineers were interested in finding a solution but had no funding.
When the township joined the subwatershed, it opened the possibility to the watershed district becoming the lead agency to find and fund a solution.
The watershed approved a tax levy for the subwatershed two years ago along with two other projects. Then over the past year a subcommittee of interested agencies looked to planners and engineers. The result was the engineering plan that got a recent nod of approval from the watershed board of directors.
After soil borings, three solutions were presented at the August watershed meeting by consultants Mark Lawrence and Mike Deutschman.
A small 6-by-8 box culvert 8 feet long could be built for $500,000 that would affect water quality only. Boats and canoes would not be able to navigate it because it would be blocked with grates. Also, channeling the water through the small space would mean a very rapid rate of flow, possible erosion, debris collection and a safety hazard.
A larger culvert would have a slower flow, allow boats through with a clearing of 8 feet during average summer flow, but engineers found unstable soil on the banks and the cost of road replacement, including raising it, would increase.
It didn't take long for directors to choose the third plan for a total cost of approximately $1.2 million, but that wouldn't require raising the road. Pre-cast concrete bridge abutments would be anchored on each side and leave a natural river channel bottom. Less maintenance would be required.
Lawrence and Deutschman said permits from the Corps, the Park Service and DNR would not be a problem.
Watershed Administrator Matt Moore said that with a plan in place grants and other funding can be sought from various organizations.
The tax levy, collected over three years, means the watershed has about $700,000 for the project. The township will also have to contribute.
Gathering the additional funding means at least another year of stagnant water before possible construction beginning in the fall of next year or spring of 2014.