Ayres did a great job
of taking on the project.
Their willingness to
jump in at a time
when we thought we
were facing a really
substantial cost increase
was so important.
been out of operation for more than 20
years. But in the early 1980s, Dakota
County officials restored the dam’s
electrical-generating capacity.
“The facility was gutted and kind
of put back in the most simple, basic,
cheapest way possible,” Petersen said.
But that proved to be merely a
stopgap measure.
In May 2011, Ayres submitted its
proposal for how Dakota County could
satisfy an order from the Federal Energy
Regulatory Commission to upgrade the
capacity of the Byllesby Dam to deal
with problems of water “overtopping”
the dam at times of peak river flow.
According to FERC’s modern safety
standards, Byllesby Dam is classified as a
“high-hazard dam.”
Pete Haug, Ayres’ project manager
for the dam project, explains the “high-
hazard” classification means that, with
the City of Cannon Falls lying just a
mile downstream, “there is a very good
chance people will die if the dam fails.”
While the dam has never experienced
such a catastrophic failure, “the safety
standards are so much higher now than
when the dam was built” in 1910,
Haug says.
To bring the dam up to today’s
standards, the Ayres team planned
and supervised the resurfacing of the
original concrete dam, which is 60 feet
high and more than 1,100 feet long.
The biggest improvement involved
adding two 65-foot-wide by 14-foot-tall
hydraulically operated floodgates to a
spillway created just to the south of
the dam.
Multiple systems were put in place
to control the rate of river flow through
the floodgates; now water can pass
through at a rate of 37,500 cubic feet
per second when the gates are fully
open. “We added 80 percent more flood
capacity to the dam,” Haug said. “That’s
an incredible increase.”
The project was completed between
May 2013 and July 2014. During that
time, construction crews contended
with extreme weather conditions,
ranging from 99-degree heat that
summer to -24-degree cold and 70
inches of snow that winter.
“This was a unique project for the
County,” Petersen said, explaining that
its sheer size and complicated nature
required a broad range of expertise that
was well beyond the scope of County
staff.
All challenges met
From creating engineering design
– Josh Petersen,
Senior Resources
Engineer,
Dakota County
Environmental Resources
TRENDS
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