Ayres also recommended installing a water circulating
machine called a GridBee in the middle of the lake. The
product’s propeller blade spins slowly and creates a steady
ripple that extends to every corner of the lake.
“(The GridBee) pushes water across the surface of the lake
and then down to the bottom of the lake – so it’s washing
the shoreline basically,” Pletcher said. “That disrupts the
blue-green algae cycle, allows the lake to stay circulated so
it doesn’t get hot on the top and cold on the bottom, and
maintains dissolved oxygen levels.”
The first phase of improvements were completed in
March 2014. The second, and final, phase will address the
stormwater and pollutants coming into Lake Minnehaha
after rainfall events. This will be accomplished by adding
water quality best management practices (BMPs) to the
storm sewer system upstream of the lake, which help keep
trash, oil, and sediment from polluting the lake.
Michael Vinson of Cheyenne’s City Engineer’s office is the
City’s project manager responsible for coordinating the
storm drainage improvements.
“We anticipate the new infrastructure will address
sediment and trash mainly. However, we may also be
addressing parking lot runoff adjacent to the lake, which
would include other pollutants,” Vinson said.
What Might’ve Been…
Curious as to what might’ve happened if the City of
Cheyenne had not gone forward with suggested improvements on Lake Minnehaha? Project Manager
Chris Pletcher of Ayres Associates said the situation
would’ve ended one of two ways.
“Either the lake would’ve been filled in, which is a
loss of the aesthetic value to the City and loss of
flood control value, or we would’ve had to post
signs and fenced the lake so that no one could touch
it,” Pletcher said.
Through its remediation plan, Ayres was able to
help the City avoid both.
“The lake is now clean, clear, accessible, and smells
nice,” he said. “We don’t have to have signs saying
‘Don’t Touch. Danger. Hazardous Water,’ and that’s
been a real value to the City because this park is an
oasis in the middle of a developed, urban area – and
we don’t want to lose that value.”
– Jennifer Schmidt
“Minnehaha”
is a Dakota Sioux word
meaning “waterfall” or
“running water”
Approximately 37,000 cubic
yards of sediment was removed
from Lake Minnehaha during the
remediation process
Including all tasks, the Lake
Minnehaha remediation project
will likely cost $2 million to
$3 million, funded primarily by
state grants over three grant cycles
Finishing touches in progress
The final phase – for which Ayres is currently under
contract – also addresses embankment improvements,
including flattening steep banks and relocating an asphalt
trail that had begun to crumble from the eroding bank
beneath it.
Ayres is completing the design work on this project now,
with construction expected in early 2016. To Pletcher,
it’s been a pleasure working on a project five years in the
making – and seeing it through from beginning to end.
“I enjoyed working with the City staff and seeing a
partnership between the consultants and the various City
departments that were involved,” he said, referring to
Parks and Recreation, City Engineering, and Public Works.
“We enjoy working with all of the departments, but it’s
fun to have all of them on a project and be able to work
together toward a common goal.
“This really allows us to complete that vision that was
started in 2011,” he continued. “And based on the timeline
from when the City last did maintenance, we think it’s
going to be 40 or 50 years before anybody has to come
back into the lake to do more maintenance – so it’s really a
long-term, effective solution.”
8│TRENDS
Being able to enhance both the beauty of the lake
and the space surrounding it is particularly exciting for
Teresa Moore, planning manager for the City’s Parks and
Recreation department.
“Then I think people will really take notice,” Moore said.
“Even though it’s great to have the improved water quality,
I think once we move onto these more aesthetic type of
things, people will really go ‘Wow.’ We’re happy to move
forward with that with Ayres.”
Parish commended Pletcher and Ayres water resources
engineer Sam Lowe for an overall job well done.
“I think they had a really good understanding of the
parameters that we had to work in and the budget
constraints that we also had,” Parish said. “They were
willing to be here almost any time that we asked, and on
the construction management side, Sam was always here
on the designated days and also here on other days. I was
quite impressed and very happy with the project.”
TRENDS
│9