Bridge Projects

View of HPS Girder - Construction Phase

One of our many projects that demonstrate Quincy Engineering's commitment to quality and innovation, this project was designed to eliminate the impacts of an active landslide on a major roadway (Sir Francis Drake Boulevard) between inland urban Marin County and the Point Reyes National Seashore. Since its construction over 60 years ago, Sir Francis Drake Boulevard has been under attack by a landslide that had caused continuous movement and settlement of the roadbed, requiring continual maintenance.

Maintenance efforts had included constant repaving that resulted in the accumulation of a 30-foot deep asphalt concrete roadbed and the eventual realignment of the road in an attempt to avoid the slide. This realignment resulted in poor sight distance through the site and lead to numerous traffic accidents over the years.

Because the slide is over 100' deep and 300' wide, a 380' long, single-span bridge made of High Performance Steel (HPS Grade 70W) girders spans the slide completely. This bridge is the longest of its kind and the first to use HPS girders in California. Quincy Engineering also identified and assisted the County in obtaining a $500,000 grant from the Federal Highway Administration’s Innovative Bridge Research and Construction Program for the use of the HPS steel girders. Other project issues include an aesthetically sensitive project setting that lead to the design and construction of a retaining wall that was sculpted to look like the natural rock outcroppings in the area. Another noteworthy project feature is the construction of a bike path below the bridge that is part of the Bay Area Ridge Trail, a heavily used facility that encircles the entire San Francisco Bay Area. Preliminary design included an extensive bridge feasibility study, Caltrans oversight and approval, and a fast-track schedule to prevent the County from losing a large portion of the project's funding.

In recognition of the innovative use of High Performance Steel, this project was awarded a Consulting Engineers and Land Surveyors of California (CELSOC) 2003 Engineering Excellence Honor Award.

Client:  Marin County Department of Public Works