goal of avoiding or minimizing impacts to the Iowa River Greenbelt was
pursued aggressively throughout the planning of the Iowa River Bridge
project. The placement of the project, the construction methods used,
and the post-construction program all fit the desire to tread as gently
as possible through the Greenbelt.
the three locations considered for the bridge, the final location
required the least amount of Greenbelt land and impacted the smallest
possible area. The crossing also avoids better-quality forest areas.
bulk of bridge construction activity took place within the footprint
of the bridge's permanent location. The "launching" of pre-constructed
bridge sections across completed piers from the east side of the valley
further minimized activity on the valley floor. Environmental impact
boundaries were clearly marked throughout the construction site.
piers straddles the river; none were located in the water.
Runoff from the bridge is channeled into an enclosed system
of drainage pipes, then to silt basins off either side of the bridge.
The basins are located away from the river.
Impact: The steel
I-girder design is slender; longer spans reduce the number of piers
needed, which minimizes visual obstructions at river level. Differences
can be seen in the various bridge
concept designs proposed for this project.
Erosion: Soil is
loose and highly prone to erosion by wind and water. Contractors
were required to keep the amount of land cleared at any one
time to a minimum. Extensive erosion control measures were
put in place during clearing and grading, to minimize soil
loss and siltation into the waterway.
biologist monitored construction activities at the site to ensure
they did not present a threat to the Iowa River and its plant, animal
and aquatic populations.
- Post-Construction: Disturbed
areas were restored to pre-construction contours and re-seeded/replanted.
Project impacts are monitored 3 to 5 years after construction
Click to see still photos of environmental
conditions and mitigation steps.