Can the 97-year-old Coon Rapids dam over the Mississippi River serve as Minnesota's barrier to the northward migration of unwanted fish, including the notorious Asian carp?
Stanley Consultants, an international firm with an office in Wayzata, has a $164,087 contract with Three Rivers Park District to answer that question by the first of next year.
The west-suburban park district, which owns and operates the dam, will be reimbursed by the Minnesota Department of Natural Resources from a $500,000 fund set up by the Legislature to create a fish barrier on the Mississippi.
Although the dam at St. Anthony Falls in Minneapolis, the Ford Dam in St. Paul and the Hastings Dam are taller and therefore better blocks to the invasive fish, they all have locks that allow fish to move upstream with boats, said Luke Skinner, DNR supervisor of the state's invasive species program. "Coon Rapids dam is the first dam on the river that does not have a lock."
Several Asian carp were caught last year in the Mississippi River near Winona.
An aggressive, unwanted species, they out-compete native fish for food and take over the habitat, Skinner said. Asian carp can jump 10 feet out of the water, even striking people in boats, discouraging recreational use and negatively affecting surrounding properties and businesses, he said.
After considering sound and bubble barriers, the DNR has decided that a tall physical barrier that is already in place would best stop the fish, Skinner said.
Under the contract with Three Rivers, Stanley Consultants will report on what would have to be done and how much it would cost to make the Coon Rapids dam a more effective fish barrier. The investigation will include measurements of how high the fish can jump and how much distance separates the top of the dam and the water level when the water is at its high point, Skinner said.
Stanley's report, due by January, is expected to deliver recommendations on improvements, repairs and preventive maintenance to extend the life of the dam another 50 years. "We want to make sure that what we do also maintains the dam," Skinner said.
If the report finds that it is feasible to make the dam a more effective fish barrier and legislators set aside money for the work, its operation as a fish block would take priority over operating it for recreation, said Director of the DNR Division of Waters, Kent Lokkesmoe. That might require keeping inflatable gates -- now used to raise the level of water above the dam only during warm-weather months -- inflated year-round, he said.
The Coon Rapids dam now is used to back up the river to create a six-mile pool for recreation between Hennepin and Anoka counties. Current practice is to deflate the gates and lower the water level of the pool in the winter to prevent ice damage to private docks and boathouses along the river.
Dam is a money drain
Keeping the old dam in good operating condition has become a money drain for Three Rivers, which is supported by suburban Hennepin County taxpayers.
Looking to shift that growing financial burden, Three Rivers last fall asked the DNR to take over the dam. The agency refused, saying it didn't want to take on more operating costs, either. There were suggestions that the dam might even be removed.
Then last March, Lokkesome issued a finding that the dam is valuable as a fish barrier and should be kept in place. "Preventing the spread of invasive species is a major concern," he said at the time. That ended speculation about the possibility of removing the dam to reduce operating costs.
Refashioning the dam as a fish barrier would not settle the question of who should own and operate it in the future. During the 2010 legislative session, lawmakers established a 15-member commission to study that question.
The panel is scheduled to begin meeting in late September to arrive at a recommendation to present to the Legislature by March 2011.
Membership of the commission will include representatives from Three Rivers, Hennepin County, Anoka County, the DNR, the state Legislature, the Mississippi National River and Recreation Area, the Army Corps of Engineers, the U.S. Fish and Wildlife Service and others.
Laurie Blake • 612-673-1711