Coon Rapids dam project running behind schedule

The Coon Rapids Dam rehabilitation project is behind schedule.

Dewatered downstream apron at the Coon Rapids Dam where a scour hole was discovered in 2009, which resulted in the rehabilitation project now underway at the dam. Photo: Minnesota Department of Natural Resources website

Dewatered downstream apron at the Coon Rapids Dam where a scour hole was discovered in 2009, which resulted in the rehabilitation project now underway at the dam. Photo: Minnesota Department of Natural Resources website

The reason is the high river flows in May, June and July and unexpected debris found upstream of the dam, according to Jason Boyle, state dam safety engineer, Minnesota Department of Natural Resources.

That has forced the contractor, Edward Kraemer and Sons, Inc., to work on Saturdays from 7 a.m. to 3 p.m. for the last two months.

But the contractor is still about 30 days behind the schedule to complete the Anoka County side of the rehabilitation project by the end of November, Boyle said.

The state has requested and the city of Coon Rapids has approved continued Saturday work, but with the ability to drive pile on that day as well, Boyle said.

Up to now the drive piling work has been confined to weekdays to minimize the impact on park users, he said.

“The Coon Rapids Dam Regional Park is heavily used on Saturdays,” Boyle said.

“The pile driving will be noticed in the park.”

According to Coon Rapids City Manager Steve Gatlin in a report to the Coon Rapids City Council, he has given permission for the contractor to keep working on Saturdays as well as adding the drive piling.

The Saturday pile driving is expected to start after the Labor Day weekend and be completed by late October, Gatlin told he council.

“It will begin no earlier than 8 a.m. Saturdays,” he said.

According to Gatlin, the piling under the stilling basin needs to driven prior to the concrete pours and the contractor is on a critical path in terms of scheduling to complete the stilling basin by mid- to late-November so that the coffer dams can be removed and the new gate system on the Anoka County side can be put into service in December.

The underwater debris found in the area of the dam reconstruction was not unusual, but it was more than had been anticipated after soil borings had been taken, Boyle said.

“When you do soil borings, you can’t hit everywhere,” he said.

Boyle remains optimistic that the Anoka County side of the rehabilitation project can be completed by the end of November, he said.

“We should be able to pour cement until the end of October,” Boyle said.

Once it gets cold, then the cement pouring process becomes slower because more precautions have to be taken, according to Boyle.

Removing the coffer dams is not dependent on the weather, Boyle said.

The coffer dams have been built above and below the dam to divert the river and allow construction crews a dry place in which to do their job, he said.

Under the two-year project timetable, work is taking place on the Anoka County side of the dam this year, moving to the Hennepin County side in 2014.

Edward Kraemer and Sons, Inc, which is headquartered in Plain, Wis., but has a Minnesota office in Burnsville, was awarded the dam reconstruction contract in the amount of $10.80 million.

The existing rubber dam is being removed and replaced with nine new steel gates.

A contract for the steel gates to be manufactured and delivered was awarded by the state last fall to the low bidder, Rodney Hunt Company, Orange, Mass. The contract totals $3.5 million.

The first spillway gate components arrived on site May 24, according to the DNR website.

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 should 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, according to Boyle.

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 peter.bodley@ecm-inc.com

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