A bridge crossing a channel in Grey Cloud Island Township has blocked the river’s flow, creating an unhealthy slough that sevral agencies are working to correct.
, Regents of the University of Minnesota. Used with permission of the Metropolitan Design Center
Rich Mullen, longtime clerk for Grey Cloud Island Township, says the Mississippi River’s flow around the island has become a problem relatively recently. “There always used to be a kind of gentle flow through there,” he said, “Fifteen years ago, we never had a weed there.”
Jim Gehrz, Star Tribune
Changing a channel in Grey Cloud Island Township
- Article by: JIM ANDERSON
- Star Tribune
- November 30, 2012 - 7:00 PM
Experts call it "maintaining meander." In Grey Cloud Island Township, it's a longstanding problem awaiting a solution. The big roadblock is figuring out a way to pay for it.
An estimated $1.1 million is needed to unclog a blocked channel of the Mississippi River that has created an unhealthy and unsightly slough. Local, state and federal agencies have made the restoration project a priority and are trying to pull together the funding needed to get it done.
Clearing the channel and restoring the river's flow would not only get rid of the slough and restore water quality, but it is hoped the waterway will be reopened to boaters and anglers in one of the more picturesque areas of Washington County.
With 125 households in about 10 square miles, Grey Cloud Island Township is the smallest township in Minnesota. It's bound on the west by the Mississippi, from which the channel breaks off and loops around on the north and east, widening on the south into two small backwater lakes -- Baldwin and Mooers -- before reconnecting with the river.
But the channel has become choked off by one of two bridges linking the small portion of the township on the mainland and the north part of the island. Culverts that once allowed the river to freely flow under the roadway have become clogged and broken.
As a result, a once-pristine channel became an unhealthy slough, with stagnant water and heavy algae blooms and muck.
"There always used to be a kind of gentle flow through there," said Rich Mullen, the township clerk and longtime resident. "Fifteen years ago, we never had a weed there."
The township has been looking at resolving the issue for about 10 years, he said, but with the township's annual budget of about $200,000, "it's something that has to be done with funding from the outside."
Known locally as "first fill," the channel crossing dates to the early 1900s, when a wooden bridge spanned the slough. In 1923 -- "the same year I was born," Mullen said -- the bridge was replaced with culverts and filled over, then paved as part of the County Road 75.
The culvert crossing worked well until a massive flood in 1965, followed by another in 1969. To keep residents from being isolated by the floodwaters, emergency work was done to raise the road. But as a result, the culverts became blocked.
As the water level dropped in recent years, the problem has worsened, Mullen said.
The South Washington Watershed District, which has taken the local lead on the project, commissioned an engineering study, completed last spring, to come up with alternatives and rough cost estimates to solve the problem. The study identified four options:
•Do nothing. Conditions in the slough would neither improve nor deteriorate much more than they have since 1965. It would cost nothing, but neither would it solve the problem. However, the stability of the roadway embankment would continue to be an issue and, given the condition of the corroding culverts, would eventually collapse.
•Install a small culvert. This would entail installing a concrete box culvert 8 feet wide and 6 feet high under the roadway, which would be the minimum size needed to meet only the goal of improving the slough's water quality. Cost: $450,000.
•Install a large culvert. This would involve installing a much larger concrete box culvert, 16 feet square, that would meet the goal of improving water quality, but also accommodate recreational boats. Cost: $760,000.
•Build a bridge. Even though constructing a bridge at the site poses some challenges, this is the solution preferred by the U.S. Army Corps of Engineers and the National Park Service. The study recommends a bridge design that would amount to a large bottomless culvert that best meets all the goals of ecological restoration, fish passage, water quality benefits and recreational navigability. The only drawback, the study notes, is cost: $1.1 million.
The watershed district is focused on pulling together the funding for the bridge option, said Matt Moore, the agency's administrator. The effort will draw on local, state and county sources. The Minnesota Department of Natural Resources, which has made improving the stretch of Mississippi River through the Twin Cities a priority, will help with the effort, he added, and Washington County could be involved as well.
Both Mullen and Moore said it's likely to take a couple of years before work actually begins on the project.
Jim Anderson • 651-925-5039 Twitter: @StribJAnderson
© 2015 Star Tribune