EXISTING BRIDGE INFORMATION
The existing bridge is a nine-span, 264-foot-long bridge with a 115-foot single span pratt through truss main span. The main span is supported on concrete-filled steel cylinders. The eight approach spans are steel stringers supported on steel pile frame bents. The deck is made of corrugated steel planks with an asphalt concrete wearing surface. The south abutment is a steel pile frame (with steel back wall), and the north abutment is concrete. The approach roadway is paved and is approximately 15 feet wide. The terrain where the bridge is located is flat to rolling. The bridge has an identified average daily traffic (ADT) volume of 493 (dated 2008). Based on observation, the current traffic speed over the bridge is less than 25 miles per hour (mph).
Purpose of and Need for Project
The purpose of the proposed project is to improve public safety and address the structurally deficient bridge. The need is based on the most current Caltrans Maintenance Report (dated August 6, 2009), which indicates that the existing bridge is structurally deficient with a sufficiency rating of 15.8. An earlier Caltrans Maintenance Report (dated August 25, 2001) indicates that the bridge is functionally obsolete with a sufficiency rating of 45.9. A bridge with a sufficiency rating of less than or equal to 50 that is also structurally deficient or functionally obsolete is eligible for replacement under the federal Highway Bridge Program (HBP).
Important Physical Attributes of the Project Site
The project study area is within the Middle Fork Scenic Area and directly adjacent to the Mohawk Valley Scenic Area, as designated in the County’s General Plan. In addition, Blairsden-Graeagle Road is a County-designated scenic roadway and State Route 89 is an “Eligible State Scenic Highway.” The proposed project will be evaluated to determine consistency with applicable County land use guidelines for projects within and directly adjacent to designated scenic areas.
The Middle Fork Feather River flows northwest from the project area before it confluences with the South and North Forks at Lake Oroville in Butte County. The river was designated a part of the National System of Wild and Scenic Rivers in 1968 by the U.S. Forest Service through the Plumas National Forest, Beckwourth Ranger District. The bridge crossing is located in the portion of the river designated as a recreational zone under the Wild and Scenic Rivers Act, with fishing, boating (kayaking, rafting), and swimming as the primary recreational uses. Although the project is located on non-federal lands, the project scope will be reviewed for conformance with the Recreation Management Plan, Middle Fork Feather Wild and Scenic River, Recreational Zone, 1978 prepared by the Plumas National Forest, Beckwourth Ranger District.