Images of Carson Park Causeway in Eau
Claire, Wisconsin
Widening the causeway means
dredging sediment – almost 11,000
cubic yards – and adding rock riprap to
support the causeway and armor the
lake banks to reduce erosion. Dredging
and filling in the navigable waters of
Half Moon Lake involved the U.S. Army
Corps of Engineers and Wisconsin
Department of Natural Resources
(DNR). The Wisconsin Department of
Transportation (WisDOT) is involved
because it is administering the project,
and the U.S. Fish & Wildlife Service
had a permitting role because of
migratory birds and the threatened
Northern long-eared bat.
The DNR supported improving the
lake but had concerns about the
sediment and fill. “That was very much
scrutinized by the permitting branch
of the DNR even if the recreational
branch was fully supportive,” Solberg
said.
Ayres structural engineer Dan Sydow
said to receive a DNR permit, the City
needed to sample and test the lakebed
material. Tests found a low level of
heavy metals in the sediment, likely
from past algae-control treatments.
That discovery added complexity –
and more permitting – to the project.
Instead of simply having the contractor
dispose of the sediment, the material
now would need to be hauled to a
permitted disposal site or landfill,
which would increase project costs.
“From a permitting perspective this
was unique,” Sydow said. “We now
were dealing with the low-hazard
waste disposal process in addition to
doing all this filling into the lake.”
An unused site near the City’s
wastewater treatment facility had
been approved for low-hazard material
for a different project. DNR solid
waste staff worked with WisDOT to
determine how to use the previous
permit for this new project, following a
different process.
“It’s an example of what can get done
when you get not only regulatory
agencies but recreational and resource
agencies and multiple divisions of
government together to brainstorm
what can happen,” Solberg said.
“When it’s all done we’ll have a better
resource and better access to that
resource.”
DNR resource staff asked for
larger pipes under the causeway
in addition to the larger bridge to
improve water exchange. Solberg
said accommodating that request
helped relieve agency anxieties over
additional fill. “They were pragmatic
on their side, and we were pragmatic
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