Laying the groundwork
According to Alliant Energy’s Jon Austin, when people
lease their land for wind energy, they generally “have no
idea how much activity will be occurring on their property.”
Just what is all that “activity”?
In the case of the Bent Tree Wind Farm project, which
stretches across 80 square miles of southern Minnesota,
consider these facts: 540 cubic yards of concrete will be
poured, 79,000 pounds of reinforcing steel will be required
for each of the more than 120 turbine foundations, and
several thousand tons of aggregate will be used for the
access roads. Several miles of crane paths are required
between sites and miles of underground collector system
conductors will be trenched in between turbines.
All that construction requires significant civil/site
engineering. Alliant Energy selected Ayres Associates to
lead this phase, which included design of access roads,
assembly areas, crane pads, and public intersection
improvements. The access roads needed to be completed in
time for the foundations to be constructed before delivery of
wind farm components, which made for an aggressive
schedule. In less than 45 days, Ayres Associates worked
closely with Alliant Energy to design 26.5 miles of access
roads, 38 public road improvements, and assembly areas
for the 122 turbines.
Alliant Energy’s goal is to minimize the wind farm’s
impact on the land. Proper civil/site design can play an
integral role in preventing long-term soil erosion.
“Maintaining the natural flow of water on the site is
crucial in terms of road maintenance and crop production
for the landowners,” Austin said.
Alliant Energy was also concerned with county-owned
drainage ditches and tiles. Real estate and right-of-way
staff worked with Ayres Associates, along with
environmental consultants and geotechnical consultants,
to ensure the wind farm met the requirements for state
and local permitting. By using wetland delineations and
property maps, layout and design of the access roads and
crane paths were done with special care to maintain the
integrity of the drainage ways.
Bruce Ommen, Ayres Associates’ project manager,
noted that the project area’s topography influenced key
site design decisions. “Small modifications, even of
25 feet, in access road or turbine location can reduce
earthwork and save thousands of dollars in construction
costs,” he said.
Upper and lower left photos: Access roads on a wind farm.
Right photo: Portion of Blue Sky Green Field Wind Energy
Center in northeastern Fond du Lac County, Wisconsin.
TRENDS
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