Project Spotlight: New bridges link to improved safety

Shoulders widened, seismic elements modernized on State Route 1 in San Luis Obispo County

Caltrans provided enhanced safety and modernized engineering this past June by completing a $17.9 million project to demolish and replace the Toro Creek Bridge on northbound State Route 1, north of Morro Bay in San Luis Obispo County.

The project included $16.3 million in funds generated by Senate Bill (SB) 1, the Road Repair and Accountability Act of 2017.

The shoulders of the old Toro Creek Bridge, which date from the early 1940s, did not allow for bicycle traffic to pass over the bridge without sharing the outside lane with traffic.

In addition to the nonstandard shoulder widths, structural and geotechnical investigations revealed that the bridge’s foundations were seismically deficient. Correcting this deficiency was required to accomplish the widened shoulders over the bridge. Replacing the bridge railing ensured compliance with what is specified in the Manual for Assessing Safety Hardware.

The old bridge measured approximately 130 feet long by 32 feet wide. It consisted of six spans, five piers and 35 supporting pile extensions. The new project created a wider three-span bridge, using fewer piers than the previous one. Eight new piles were installed in the creek channel. The inside shoulders now measure 5 feet wide and the two 12-foot-wide lanes now have a right side shoulder width of 10 feet.

The new bridge profile was slightly increased to accommodate the anticipated sea-level rise from climate change. The new abutments and installed rock slope protection (RSP) safeguards the abutments from erosion.

Construction began in May 2022 and included a traffic shift with one lane in each direction for travelers. Initially, the new configuration featured two lanes in the northbound direction with traffic flowing over the new bridge and one lane in the southbound direction. In early summer, a second southbound lane opened.

Caltrans landscape planners anticipate that the surrounding, newly planted vegetation will take about two years to attain a mature appearance.

The new bridge complies with current earthquake, geometric, hydraulic and structural standards and represents an important upgrade to the state transportation system’s infrastructure. The prime contractor was Souza Construction of San Luis Obispo.

Elsewhere in San Luis Obispo and also on State Route 1, Caltrans demolished and replaced the 82-year-old Old Creek Bridge near Cayucos. The project’s need was similar to the Toro Creek Bridge as original shoulders were insufficiently wide by today’s standards and the seismic engineering was outdated.

The $9.3 million Old Creek Bridge project was mostly funded by SB 1.

The new structure consists of a three-span bridge, supported by concrete columns at the piers (the original bridge had five spans and four piers founded on reinforced concrete pile extensions). Inside shoulders now measure 5 feet wide, and the two 12-foot-wide lanes now have a right shoulder width of 11 feet, 6 inches – which exceeds the 10 feet minimum.

Similar to the Toro Creek Bridge replacement, the bridge’s height was slightly increased to accommodate the anticipated sea-level rise.

Construction began this spring with a 24/7 closure of the northbound/ southbound number 1 (left) lane to install protective barriers for highway workers during the daytime hours, followed by a traffic switch where travelers headed northbound on Highway 1 were diverted onto the southbound lanes with two-way (north/south) traffic maintained with a center median.

This traffic switch allowed for the demolition of the bridge on northbound State Route 1.

Papich Construction of Arroyo Grande served as contractor for the project, which was completed this summer.

Sources: Carla Yu, District 5 senior transportation engineer and project manager for both the Toro Creek and Old Creek projects; and Jim Shivers, District 5 public information officer