Sir Francis Drake Rehabilitation Project
3.0 Project Description
Figures and Overview
Sir Francis Drake Boulevard (SFDB) is an east-west arterial roadway located in Marin County that commences just west of the Richmond-San Rafael Bridge and ends at the Point Reyes Lighthouse. A section of SFDB located about one mile west of the Town of Lagunitas between Shafter Bridge and Platform Bridge Road contains segments of severely deteriorated pavement that has exceeded its design life. The Marin County Public Works Department in association with the Board of Supervisors and the Transportation Authority of Marin has commenced studies to develop a strategy for the rehabilitation of this 5.2 mile long segment of roadway.
A majority of the roadway exhibits distress including cracking and dislocations of the pavement. Prior maintenance by Public Works has included removal and replacement of damaged sections of roadway and overlays of asphalt concrete. However, these repairs are no longer effective as the pavement’s structural section has failed. Without major rehabilitation, the roadway’s condition will likely further deteriorate as cracks in the pavement allow water to infiltrate weakening the sub grade and creating additional distress.
SFDB contains critical environmental resources including Lagunitas Creek, vegetative communities of redwood and oak, native plants, and habitats suitable for protected species. Additionally, the roadway bisects both Samuel P. Taylor State Park and the Golden Gate National Recreation Area.
Topographic, geotechnical, and environmental studies of the Project Area have been completed and used as a basis to develop a strategy for rehabilitation of SFDB. Factors that have been considered include environmental resources, physical site constraints, cost, construction feasibility, and roadway design standards. Various alternatives were explored and a proposed rehabilitation strategy was selected that will extend the roadway’s design life and enhance safety while preserving environmental resources.
3.2 Existing Roadway Conditions
The section of SFDB between Platform Bridge Road and Shafter Bridge (Project Area) as shown in Figure 1 was constructed in the 1929 as a two lane arterial roadway. Along a majority of the Project Area, there is limited recorded right of way. While SFDB bisects both a federal and state park, the County of Marin has historically maintained the roadway. For reference to specific features, a station line as shown in Figure 2 is provided along the roadway. Each station indicates an interval of 100 feet and commences at Station 5+60 (Platform Bridge Road) and ends at Station 279+50 (Shafter Bridge).