Confusion Hill Bridges
Encyclopedia
The Confusion Hill Bridges (aka. Confusion Hill Realignment, Confusion Hill Bypass or South Fork Eel River Bridges) are a pair of high bridges carrying two lanes of U.S. Highway 101 over the South Fork Eel River
in Mendocino County in the U.S. state
of California
. The bridges were constructed to reroute approximately 1.7 miles (2.7 km) of the highway away from a massive landslide area on the south bank of the river. The north bridge was finished in July 2009 and the south bridge completed in September 2009; the whole bypass was officially opened to traffic in October of that year.
The bridges were designed by the California Department of Transportation
(Caltrans), and the contractors were MCM Construction Inc. and the Finley Engineering Group. The north bridge was begun on July 26, 2006 and it was completed in November 2008. Before the south bridge was finished, the north bridge was used to carry construction debris out of the realignment site on the opposite bank. The south bridge was begun in November 2006 and its two piers were completed by November 2008.
While the north bridge was opened in July 2009, the south bridge, which was also finished in July 2009, was opened in September 2009 and the Confusion Hill Realignment project was completed in October 2009. The total cost of this project is estimated at $67 million.
The bridges are collectively named after the nearby roadside attraction Confusion Hill
. The two individual bridges were named after two pioneers, Elizabeth Jane Rosewarne and Mignon Stoddard Lilley.
. The site is located at a bend in the South Fork Eel River that takes it from a north-flowing course to turn east, north and west. The original path of Highway 101 follows the outside curve of this bend, while the realignment consists of two bridges, a north and south span, on opposite sides of the bend. The realigned portion of the roadway follows the bank of the South Fork opposite from the current bank the roadway follows. The northern bridge is 140 feet (42.7 m) high and has three spans totaling 531 feet (161.8 m) in length. The southern bridge is larger, at 253 feet (77.1 m) above the river and 1395 feet (425.2 m) long. Both bridges are concrete beam bridges with two piers and three spans.
The north bridge (39.5540°N 123.4548°W) has two slanted piers that are supported on the hills surrounding the river. Each pier measures 17.5 feet (5.3 m) by 6.9 feet (2.1 m). The south bridge (39.5516°N 123.4549°W) has three spans that are 348 feet (106.1 m), 571 feet (174 m), and 436 feet (132.9 m) in length, while its deck is 43 feet (13.1 m) wide. It has two straight piers that support the side spans that extend out towards the center using cantilever
s. The center span rests on these two cantilevers. The spans are actually slightly arched with a maximum depth of 31.4 feet (9.6 m) and a minimum of 11.5 feet (3.5 m).
South Fork Eel River
The South Fork Eel River is the longest and largest tributary of the Eel River, in the north-central part of the U.S. state of California. The river flows north from Laytonville to Dyerville/Founders' Grove where it joins the Eel River on the left bank...
in Mendocino County in the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
. The bridges were constructed to reroute approximately 1.7 miles (2.7 km) of the highway away from a massive landslide area on the south bank of the river. The north bridge was finished in July 2009 and the south bridge completed in September 2009; the whole bypass was officially opened to traffic in October of that year.
History
The Confusion Hill realignment bypasses the "Confusion Hill slide", a reach of unstable hillside about 1000 feet (304.8 m) long and 3000 feet (914.4 m) wide. Prior to the realignment this slide would shift during heavy rains, causing damage to the roadway and delays to traffic.The bridges were designed by the California Department of Transportation
California Department of Transportation
The California Department of Transportation is a government department in the U.S. state of California. Its mission is to improve mobility across the state. It manages the state highway system and is actively involved with public transportation systems throughout the state...
(Caltrans), and the contractors were MCM Construction Inc. and the Finley Engineering Group. The north bridge was begun on July 26, 2006 and it was completed in November 2008. Before the south bridge was finished, the north bridge was used to carry construction debris out of the realignment site on the opposite bank. The south bridge was begun in November 2006 and its two piers were completed by November 2008.
While the north bridge was opened in July 2009, the south bridge, which was also finished in July 2009, was opened in September 2009 and the Confusion Hill Realignment project was completed in October 2009. The total cost of this project is estimated at $67 million.
The bridges are collectively named after the nearby roadside attraction Confusion Hill
Confusion Hill
Confusion Hill is a roadside attraction in Piercy, California. The attraction includes what is dubbed as a "gravity house," a structure built to give the interior visitors tilt-induced optical illusions, similar to the perspective on a gravity hill...
. The two individual bridges were named after two pioneers, Elizabeth Jane Rosewarne and Mignon Stoddard Lilley.
Description
The two spans of the Confusion Hill Realignment are located about 8 miles (12.9 km) north of LeggettLeggett, California
Leggett is a census-designated place in Mendocino County, California. It is located on the South Fork of the Eel River northwest of Laytonville, at an elevation of 984 feet . It is home to some of the largest trees in the world...
. The site is located at a bend in the South Fork Eel River that takes it from a north-flowing course to turn east, north and west. The original path of Highway 101 follows the outside curve of this bend, while the realignment consists of two bridges, a north and south span, on opposite sides of the bend. The realigned portion of the roadway follows the bank of the South Fork opposite from the current bank the roadway follows. The northern bridge is 140 feet (42.7 m) high and has three spans totaling 531 feet (161.8 m) in length. The southern bridge is larger, at 253 feet (77.1 m) above the river and 1395 feet (425.2 m) long. Both bridges are concrete beam bridges with two piers and three spans.
The north bridge (39.5540°N 123.4548°W) has two slanted piers that are supported on the hills surrounding the river. Each pier measures 17.5 feet (5.3 m) by 6.9 feet (2.1 m). The south bridge (39.5516°N 123.4549°W) has three spans that are 348 feet (106.1 m), 571 feet (174 m), and 436 feet (132.9 m) in length, while its deck is 43 feet (13.1 m) wide. It has two straight piers that support the side spans that extend out towards the center using cantilever
Cantilever
A cantilever is a beam anchored at only one end. The beam carries the load to the support where it is resisted by moment and shear stress. Cantilever construction allows for overhanging structures without external bracing. Cantilevers can also be constructed with trusses or slabs.This is in...
s. The center span rests on these two cantilevers. The spans are actually slightly arched with a maximum depth of 31.4 feet (9.6 m) and a minimum of 11.5 feet (3.5 m).