Arroyo De La Laguna Bridge Project

Project Information:

Caltrans proposes to replace the Arroyo de la Laguna Bridge (Bridge No. 33-0043) to address scour and seismic concerns and meet current design standards for safety.

The proposed project would take place on State Route (SR) 84, locally signed as Niles Canyon Road (hereafter referred to as SR 84) at post mile (PM) 17.2 in the town of Sunol in unincorporated Alameda County.

Project Public Meeting:

A virtual public meeting was held August 24, 2021 at 6:00 pm.

Final Environmental Document

Link to Final Environmental Document (DED)

Environmental Document (DED) Appendices

Project Purpose:

The purpose of the proposed project is to maintain connectivity and provide an improved highway facility for the traveling public along SR 84 by replacing the existing bridge over Arroyo de la Laguna.

Project Need:

Structural maintenance inspections completed in October 2013 identified scour at piers 4 and 5 of the bridge. Scour, a condition where the bed and bank material from around the piers is washed away by stream flows, is undermining the footing at Pier 5. The bridge is currently classified as “scour critical,” which means it has pier foundations that are rated as unstable due to scour. Additionally, in 2016, the Office of Earthquake Engineering Analysis and Research identified the bridge to be seismically vulnerable and a candidate for seismic retrofit.

The bridge railings, built in 1939, do not offer the structural integrity of modern railings and do not provide the capability to redirect vehicles back onto the roadway in the event of a collision.

Furthermore, the alignment of the existing bridge and approach directs eastbound traffic into the path of the Sunol Water Temple entry gates on the south side of SR 84, a potential hazard to travelers on the roadway and the historic structure. The curvature, lane alignment, shoulders, slope of the bridge, and the western and eastern approaches no longer meet Caltrans design standards. Caltrans establishes and supports the consistent application of highway design standards to ensure optimal safety for the traveling public and for those who work to construct, operate, and maintain the State Highway System.

Build Alternative:

The Build Alternative would replace the existing 310-foot-long and 38-foot-wide Arroyo de la Laguna Bridge with a new 310-foot-long and 64-foot-wide bridge consisting of two through lanes, one in each direction. The new bridge would either be flat (as the existing structure) and box-shaped, or it would contain an arch. The bridge profile would be raised by 1 to 3 feet to improve the existing non-standard stopping sight distance, which is the distance a driver needs to be able to stop before colliding with an object in the roadway. At completion, the finished structure would provide 12-foot-wide lanes, a 14-foot-wide shared east-west pedestrian path on the south side of the bridge, standard 42-inch-high barriers, 9-foot-wide shoulders to accommodate 6-foot-wide bicycle lanes, and a 2-foot-wide painted median rumble strip. The shared sidewalk would be protected from the roadway by concrete railing. The Build Alternative would also add sidewalks to the eastern side of the SR 84 and Main Street intersection and at the SR 84 and Pleasanton Sunol Road intersection.

No Build Alternative:

Under the No Build Alternative, no scour remediation or safety improvements would be made to the Arroyo de la Laguna Bridge. Structural, safety, and operational deficiencies would persist along SR 84 in the project area.

Link to Final Environmental Document (DED)

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