Southern Heights Bridge Replacement
Design for a bridge replacement, upgrading to a cast-in-place concrete bridge with a sidewalk and custom lighting to improve safety and access.
Details
Description
Mark Thomas provided preliminary engineering, environmental clearance, and final design services for the Southern Heights Boulevard Bridge Replacement project in San Rafael. The existing 162-foot-long timber bridge, built in 1981, connected two roadway segments separated by a hillside and served as a vital access point for vehicles and pedestrians. The bridge also provided direct driveway access to two homes located at either end. Over time, the structure exhibited significant deterioration, including splits and decay in the deck and railings, as well as signs of dry rot in the substructure. Replacing the bridge was necessary to maintain access to nearby homes and ensure a reliable emergency response.
The Southern Heights Boulevard Bridge was viewed by many as a neighborhood landmark, offering iconic views of Mt. Tamalpais and the surrounding ridgeline. Public outreach was extensive, allowing residents to voice their concerns and preferences, and many expressed a desire for a narrow timber bridge replacement. Because timber bridges are no longer permitted in California, the project team prioritized a design that could replicate the visual character of the original bridge through aesthetic treatments. The community also advocated for a narrow bridge profile and the inclusion of a sidewalk for safe pedestrian access.
The bridge was replaced with a cast-in-place, three-span reinforced concrete slab structure. The new structure included a 12-foot-wide deck, aesthetically pleasing painted steel “see-through” barriers with custom down-lighting, access from the bridge deck to an adjacent residence, and utility supports along the edge of deck for a 6” waterline. Lightweight cellular concrete was used as backfill at the abutments to reduce the load on the structure. A 33-foot-long steel solider pile with concrete facing was used at the west side of abutment to retain the bridge approach.
Market Sector
Awards
- 2022 ENR California Best Highway/Bridge Project Award | Northern California | Design Category
- 2022 ENR California Excellence in Sustainability Award | Northern California
- 2022 ENR California Excellence in Safety Award | Northern California – Award of Merit | Construction Category