The Panther Creek Bridge is a 168-ft hybrid tied arch on U.S. Route 101 near Klamath, CA. It has galvanized steel arch ribs and floor beams, combined with post-tensioned concrete tie beams. It is Caltrans’ (California Department of Transportation) first bridge project to specify hot-dip galvanizing for its primary structural members.

The bridge crosses Panther Pond, which is critical habitat for Pacific coast salmon and other wetland species. The site, on Yurok tribal land, is a highly regulated environment. Wetland and aquatic constraints prohibited the use of fixed platforms and temporary supports in the water. An unusual erection sequence satisfied constraints in the short term, but the long-term strategy is avoidance. With coastal corrosion in mind, Caltrans chose to galvanize the steel in pursuit of a 100-year service life with a low maintenance burden.

The galvanized steel is painted green to comprise a duplex coating system. The arch ribs are hollow box sections; the interior of the box is unpainted. The floor beams have very little clearance to the pond below. Galvanizing these relatively inaccessible surfaces was an important feature that won support for a steel bridge on the rainy North Coast of California.

To enhance the aesthetics of the bridge, some components were left unpainted. The bare zinc of the hangers and the pedestrian railing echo the grey concrete and generally grey skies. The overall effect is an understated grey and green color story that blends in with the scenic environment.