Froom Ranch Way Bridge Project
Community Improvement Project
Froom Ranch Way Bridge (Froom Bridge) is a part of the larger, San Luis Ranch Development in the City of San Luis Obispo, California. The bridge provides a key access point into the San Luis Ranch community from Los Osos Valley Road, and it connects to Dalidio Way across a critical City drainage channel in the vicinity of a 100-year flood plain. It is a single-span, 142.5-foot, corten steel, vehicular and pedestrian bridge that also provides emergency vehicle access into the community.
The bridge’s horizontal and vertical geometry balance existing constraints through the following design elements:
• Ties in with the existing alignment of Froom Ranch Way,
• Keeps the eastern approach low enough to avoid encroaching or placing fill in the 100-year area of inundation, and
• Avoids disturbing or damaging the existing concrete channel structure upstream of the bridge location.
Froom Bridge has distinct structural design elements. The bridge ‘floats’ on its abutments, transferring the lateral structural load in the event of extreme hydrologic and seismic events. In other words, the bridge abutments are designed to allow one abutment to handle the entire load should the other be compromised during a flood or earthquake. The truss allows an increase in the bridge’s low chord (lowest member) elevation to reduce ramping from the road surface. It also provides a convenient location for hanging and accessing the 12-inch, City of San Luis Obispo water main and other public utility crossings, such as PG&E, Charter, AT&T, and City signal interconnection.
Finally, the truss design is also an aesthetic entrance to the development and creates an efficient solution for this crossing of Prefumo Creek. The prefabricated bridge’s single-span solution did not require use of falsework (temporary support structures) in the creek. A cantilevered 12-foot pedestrian Class I Path physically separates pedestrians and vehicular traffic, avoiding the need for a secondary pedestrian bridge. This cantilever also provides a larger clearance at the upstream edge to the 100-year water surface elevation.
The bridge is owned by City of San Luis Obispo, but most of the project was led by the developer, MI San Luis Ranch. Cannon was the primary engineering consultant for the project, and Wallace Group was responsible for hydraulic engineering. Structural engineering was provided by Cornerstone Structural Engineering Group, and Althouse & Meade was the lead environmental consultant on this project. Papich Construction served as the construction contractor.