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Middleton Road Bridges
Canyon Highway District #4
OVERVIEW
This $3 million project on Middleton Road, south of the City of Middleton
in Canyon County, Idaho included the replacement of two bridges and
about 0.5 miles of roadway improvements.
CHALLENGE
Because of the limited number of Boise River crossings in the region,
the design required that traffic be maintained across the existing
bridges during construction. Accommodating fluctuating flows in the
Boise River required addressing floodplain issues with overflow channels.
There were concerns regarding potential water quality and wetland
impacts.
SOLUTION
The new bridges were offset from the existing bridges to address
construction traffic control concerns. Bridge design included a new
5-span 430-foot bridge over the Boise River and a 92-foot single
span bridge over 15 Mile Creek. This design significantly reduced
the number of piers in the waterway, resulting in no change to river
flood elevations, and minimized permanent in-water and wetland impacts.
Complex Boise River and overflow channel modeling was conducted to
analyze scour and assess flood elevations. This allowed the Keller
Associates’ design engineers to optimize roadway grades while
maintaining clearance over flood elevations. |
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