The streamflow at historic Dunton Locks County Park is in for some changes: The old drydock outlet a few hundred feet south of the main channel will become a fish-friendly rock rapids with five levels.
And in a separate project, the main channel itself will see its rock rapids improved.
From 1889 to 1918, before the advent of the automobile, Dunton Locks was a hotspot for small steamboats that ran pleasure cruises on the Pelican River chain.
A lock and dam system enabled boats to move down nearly six feet from Lake Sallie to Muskrat Lake, then through to Lake Detroit, and back again. The Dunton Locks resort, with a hotel, cabins and a nightclub, was a popular destination, according to MNopedia, a Minnesota history website.
The main lock and dam at Dunton Locks was replaced by the state Department of Natural Resources with a rock arch rapids in the early 2000s, but the aging drydock outlet remains.
It consists of a pond-sized area (popular with fishermen) that receives water from the adjoining Muskrat Lake and sends it down to Lake Sallie.
Water is now flowing freely through the drydock area, but a concrete dam can control the inflow with stoplogs, and a cast-in-place concrete culvert can control the outflow the same way.
So why is this project being done now? Pressure on this secondary outlet has increased since the rock rapids replaced the lock and dam on the main channel, contributing to streambank erosion in the outlet going into Lake Sallie, and crumbling concrete on the outlet culvert, said Becker County Economic Development Coordinator Guy Fischer.
“The drydock was getting increasingly undermined, there’s a lot of water pouring over there,” he said.
Rock rapids will also make the dry docks area accessible to fish working their way upstream. They are now blocked by the nearly 3-foot drop in elevation from the culvert to the outlet streambed.
Becker County landed a DNR grant of about $46,000 for the project. A 10% match requirement is being met with $5,000 from the Pelican River Watershed District, and re-vegetation work will be done by the Becker Soil and Water Conservation District, Fischer said.
The county itself kicked in more than $14,000 for an unusual bridge across the outlet stream. It involves a “pan” that lays down in the earth spanning the water, with I-beams on top of the pan, Fischer said.
“It works really slick,” he said. “You can lay it down in marshland or wherever. It never moves.”
The bridge will have a 7-ton weight limit, enabling county workers to cross in a pickup truck to work on the dirt trails on the other side of the outlet.
The drydock pool area will also be enhanced with boulders and amenities for anglers, Fischer said.
“It will have quite a different vibe than it does now, which will be nice,” he said.
Boit Excavating of Detroit Lakes submitted the lowest of three bids (for $8,430) and was awarded the contract for the project. The county is waiting on a permit from the Army Corps of Engineers. It already has a permit from the watershed district. If things come together, infrastructure work could start as early as next month and be finished in a few weeks. The drydock area will be essentially drained during the construction process.
In a separate project, the DNR will revamp and improve the rock arch rapids in the main channel later this year. The DNR will oversee the county project as well as its own, but the work will be done at different times. “We don’t want to step on each other’s feet,” Fischer said.
The slope on the existing rock rapids in the main channel will be lessened and an extra ring of rocks will be added to the end of the channel, in Lake Sallie.
That will make it easier for fish to make it all the way up the channel -- they now tend to get stuck on the second level from the top, said Nathan Olson, DNR area fisheries supervisor in Detroit Lakes. “It was one of our first projects of that type,” Olson said, “and it has a steeper slope than we like to see on a lot of our projects.”
Another benefit to the improved channel is that it will have larger pools between rock circles, enabling larger fish to travel upstream. Lake sturgeon, for example, which were reintroduced to area waters after the original rock arches were built at Dunton Locks some 17 years ago, are now 50 or 60 inches long, and have trouble navigating the existing pool layers at Dunton Locks, Olson said.
The project on the main channel will not affect lake elevations, since the top rock level will not change, he said. The changes to the drydock outlet also will not affect lake levels, he said.
Materials for the main channel project will cost about $18,000, and labor will be done by the DNR fisheries construction crew, which works statewide, but is based in Detroit Lakes. Construction will start the third week of this month and should be wrapped up in a week or two, Olson said.