Projects - Infrastructures
Bridges: Vehicular

Flagstaff Road Bridge
Boulder, Colorado

Boulder County, Colorado

The Flagstaff Road Bridge was awarded the ACEC/Colorado 1997 Engineering Excellence Award for its innovation in solving a difficult, potentially dangerous problem.

The spring of 1995 produced record rains throughout the Front Range. These rains saturated soils on Flagstaff Mountain and created a landslide on the steep embankment. The landslide undermined away a large portion of the roadway and threatened houses below.

While brainstorming with Boulder County personnel, we evaluated a bridge option in addition to conventional tied-back retaining walls. The bridge concept was selected because it was less expensive and would blend in with Boulder's mountain backdrop.

Our solution consisted of a cast-in-place cantilevered bridge deck supported on caissons drilled into bedrock. The bridge stopped at the centerline of the roadway so traffic could remain open during construction, avoiding 40-minute detours. The finished bridge was well received, with minimal complaints during construction.