By PETER BODLEY
Work continues on the Coon Rapids Dam rehabilitation project, despite recent sub zero temperatures.
Plans were originally to complete the project on the Anoka County side of the dam by November of last year.
But contractor Edward Kraemer and Sons got a late start because of high river flows. Then another problem arose when unexpected debris was found: pile driving problems, according to Jason Boyle, state dam safety engineer, Minnesota Department of Natural Resources.
With the five new gates installed and operational on the Anoka County riverbank, the scour hole fixed and the coffer dams built, completion was pushed back until the end of January 2014.
“All five gates for the new dam on the Anoka County side – there will be nine gates in the overall project – are in place, but the hydraulic cylinders to operate them have not yet been installed,” Boyle said. “The new gates have to be operating in time for the spring runoff.”
In addition, concrete work continues on the apron of the dam.
That had to be done, despite the recent frigid temperatures, through tenting and heating the area where the concrete was to be poured, according to Boyle.
“The cold weather has not stopped work, but it has certainly slowed it down,” Boyle said.
And precautions have to be taken to ensure worker safety, he said.
Plans remain to start phase two of the dam rehabilitation project on the Hennepin County side of the Mississippi River this spring.
“That will involve creating new coffer dams where crews can work, putting in place the remaining four gates of the new dam and installing the hydraulic cylinders to make them work,” Boyle said.
But there is less concrete apron work needed on the Hennepin County side.
“The project remains on pace to be completed on schedule in late 2014,” Boyle said.
The existing rubber dam is being removed and replaced with the nine new steel gates.
A contract for the steel gates manufacturing and delivery was awarded by the state last fall to the low bidder, Rodney Hunt Company, Orange, Mass. The contract totaled $3.5 million.
The work on the Anoka County side has also involved building a new concrete apron to replace the concrete apron downstream of the dam where a scour hole was found in 2009.
It was the discovery of the scour hole that resulted in the decision to replace the existing rubber gates not only to extend the life of the dam, but also to make the dam a more effective barrier to the migration of invasive fish species, like Asian carp.
The project is being funded by $16 million that was allocated in the 2011 state bonding bill approved by the Minnesota Legislature and signed by Gov. Mark Dayton.
With the contracts awarded for the new steel gates and the reconstruction work plus the $900,000 contract with Stanley Consultants, Minneapolis, to do the design and engineering, the project is within its budget, Boyle said.
Under a joint powers agreement with Three Rivers Park District, which owns and operates the Coon Rapids Dam, the DNR is solely responsible for the reconstruction of the dam as well as maintaining it as a fish barrier.
The work on the Anoka County side this year has meant the walkway over the dam as well as the Anoka County boat launch have been closed.
The walkway will remain closed until the entire project is completed next year, but the boat launch is scheduled to be back open in 2014, Boyle said.
The water level in six-mile pool above the dam will stay at the summer level permanently, not only throughout the project’s construction period but in the years beyond once the project is completed.
The Coon Rapids Dam was built in 1913 by Northern States Power Co. to generate hydroelectric power. When power generation stopped in the 1960s, the power company donated the dam and surrounding land on both sides of the river to the park district.
Anoka County now owns all the park property on the Anoka County side of the dam.
Peter Bodley is at firstname.lastname@example.org