The Foresthill Bridge is structure which carries Foresthill Road over the North Fork American River near Auburn of Placer County. This 2,428-foot-long structure is one of the most famous bridges in California due to it carrying a road deck height of 730 feet. The Foresthill Bridge was completed in 1973 amid construction of Auburn Dam. The ultimate failure of the Auburn Dam construction project has ensured the bridge remains the highest in the state.
Part 1; the history of the Foresthill Bridge
The Foresthill Bridge is named after the Gold Rush era community of Foresthill. The community of Foresthill is located in Todd Valley on a ridge between the North Fork and Middle Fork of the American River. The community was plotted in the Spring of 1850 during at a trail junction between Yankee Jim's and Coloma. Mining activity in Foresthill began to take off during 1853 after discovery of gold in a nearby canyon after a landslide.
Foresthill can be seen as Todd Valley on the 1857 Britton & Rey's map of California. The community is shown to be connected by road to Yankee Jim's, Coloma and Auburn. The road to Auburn is shown to cross the North Fork American River near the confluence with the Middle Fork.
As mining activity increased during the late 1850s Foresthill would begin to grow into one of the largest communities in Placer County. The community appears on the 1882 Bancroft's map of California. The road connecting Foresthill to Auburn via the North Fork American River is shown prominently.
The 1891 United States Geological Survey map of Sacramento displays location of the North Fork American River Bridge on the original alignment of Foresthill Road (blue pin). An alternative route is shown branching east from Auburn underneath the future site of the 1973-era Foresthill Bridge.
Foresthill Road is shown as a major local highway east of California State Route 49 on the 1935 Division of Highways map of Placer County.
The crossing of the North Fork American River along the original alignment of Foresthill Road has had numerous bridges over the decades. This truss structure was removed in 1955 and replaced with the current steel span. The vintage of the truss span pictured below is not known to this page, please leave us a comment if you know when it was constructed.
During the 1950s Auburn Dam was proposed to be constructed downstream from the North Fork and Middle Fork of the American River. The selected dam design was a 680-foot-high concrete gravity structure which broke ground on October 19, 1968. The planned reservoir would have flooded the original location of Foresthill Road which required a new alignment be constructed.
Foresthill Road was planned to be realigned over new road which crossed the then planned reservoir along the course of the North Fork American River. The planned bridge was to be located 730 feet above the river which made it the highest in California. In 1971 the Foresthill Bridge was fabricated and brought to the new alignment of Foresthill Road. The structure would be completed in 1973 and opened to traffic as an expressway.
The 1973-era Foresthill Bridge (blue pin) can be seen north of the 1955 river-level span on the below 1975 era aerial image of Auburn. The then new alignment of Foresthill Road began at what is now Interstate 80 Exit 121 in Auburn. The new alignment crossed the over North Fork American River and intersected the Old Foresthill Road alignment approximately mile to the east.
During 1975 a 5.7 magnitude earthquake occurred in the Sierra Nevada near Oroville Dam. Work on Auburn Dam was halted to access the vulnerability of the planned structure. Auburn Dam was found to be on the site of a previous unknown fault line which could cause the concrete gravity design to fail. Controversy about a modified design continued during the late 1970s. Ultimately the dam foundations were completed by April 29, 1979.
A new proposed design for Auburn Dam was submitted in 1980. The cofferdam for the structure ultimately failed on February 18, 1986, when heavy flooding on the North Fork American River caused it to erode away. The flooding destroyed much of the dam construction site and caused waters to rush downstream into Folsom Lake. Ultimately Folsom Lake was able to be drained before major flooding occurred in the city of Folsom.
The site of Auburn Dam remained contentious during the 1980s and 1990s as numerous proposals were brought forth for the structure to be completed. Ultimately all modified water project bills were rejected, and the United States Bureau of Reclamation abandoned their water rights on November 11, 2008. The abandonment of the Auburn Dam project ensured the Foresthill Bridge would remain the highest span in California. The bridge would go through a $74,400,000 seismic retrofit circa 2011-2015.
Part 2; a visit to the Foresthill Bridge
The 1973 era Foresthill Bridge can be seen from the 1955 era span at the North Fork American River. The 1955 structure is now where the popular Lake Clementine Trailhead can be located. The site was annexed into the Auburn State Recreation Area in 1966. The recreation area had been created in anticipation of Auburn Dam being constructed.
The 1973 era Foresthill Bridge is visible to traffic along northbound California State Route 49 on the descent to the North Fork American River.
The Foresthill Bridge carries a four-lane Foresthill Road as an expressway atop the structure. A sign at the top of the 2,428-foot-long bridge notes it to be the highest in California. The structure was further popularized when it appeared in the 2002 film XXX which featured a C5 Corvette being driven off of it.
Photos from the northern and southern sides of the Foresthill Bridge.
This photo faces south from the Foresthill Road to the confluence of the North Fork and Middle Fork of the American River. The 1955 bridge carrying Old Forest Hill Road is easily observed.
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