User:Mliu92/sandbox/Rio Vista Bridge

The Helen Madere Memorial Bridge, commonly called by its former name, the Rio Vista Bridge after its location, is a vertical-lift bridge which carries California State Route 12 across the Sacramento River at Rio Vista, California. The present bridge was completed in 1960 and is one of several moveable bridges spanning rivers in the Sacramento–San Joaquin River Delta. the bridge carries approximately 21,000 cars per day.

1919 bascule bridge
The original bridge spanning the Sacramento River was built in 1918 and opened in January 1919 at a cost of US$260000 1919. From west to east, the 1919 bridge consisted of a 70 ft concrete tied arch, the 343 ft Strauss double-leaf bascule, three 120 ft concrete tied arches and 1670 ft timber A-frame trestle spans.

1960 tower bridge
The 1919 bridge was replaced during seventeen years of piecewise construction. The finished 1943–1960 bridge consists of thirteen steel Warren truss spans (with one of those being the 306 ft vertical-lift chorded Warren truss main span) carried on twelve piers. Total bridge length is 2890 ft, including 441 ft of concrete slab approach spans on the west end of the bridge. Upon completion, the Rio Vista bridge won an American Institute of Steel Construction class IV (movable bridges) prize bridge award in 1960.

The main lift span weighs 750 ST, with an equal amount in counterweights, so the lift mechanism operates 1500 ST using two 30 hp electric motors, one in each tower. In the event of electrical failure, backup electrical power is provided by a 167 hp diesel generator set. The main lift span can be raised to its full height in less than 90 seconds, although the total operating cycle can disrupt road traffic for 8–25 minutes. Clearance under the raised lift is 135 ft to the highest anticipated water level, and the navigation channel is 270 ft wide between the timber fenders protecting the tower piers. With the lift down, vertical clearance is only 18 ft.

Construction 1943–1960
Less than thirty years after being completed, the eastern timber trestles of the 1919 bridge were in poor condition, and construction of replacement steel trusses began in 1943. Construction of the 1300 ft eastern steel truss section, consisting of seven 180 ft truss spans, was completed in 1945 at a cost of US$730000 1945, and traffic was diverted from the timber trestles onto the steel trusses with a crossover. The US Corps of Engineers authorized replacement of the remaining portion of the bridge on 2 February 1950, with contracts awarded for US$960000 1960 to Lord and Bishop for the substructure and US$2410000 1960 to Judson Pacific Murphy for the superstructure, with an additional US$124000 1960 contract to Pacific Murphy for the concrete slab approach spans.

The substructure was constructed from 4 April 1957 through 30 October 1958, and consists of the concrete piers and pilings. The first part of the superstructure erected was the east tower, which began on 4 December 1958. The superstructure was assembled in prefabricated segments at Pacific Murphy's Richmond yard and barged upstream to the construction site, where they were raised into place by a 100 ST capacity barge crane. The sheaves at the top of each tower were lifted in place during high tides in order to reach the necessary height. The 1960 superstructure

The construction of the bridge overlapped the planning process for the Sacramento Deep Water Ship Channel. When plans for the Deep Water Channel were complete, the eastern truss section of the new bridge were already complete, and the Channel rerouted ship traffic from its then-current course near the western bank (through the 1919 bascule) to a point 575 ft east. A new crossover from the 1919 bascule bridge to the 1945 steel truss spans was built to avoid interference with substructure construction, and after the new lift portion was built, another crossover was built to reroute road traffic from the 1919 bascule to the 1960 bridge. Once the new bridge was complete, removal of the old structure was completed by July 1960.

1967 Ilice crash
On 15 January 1967, the Italian freighter Ilice missed the raised draw while underway in heavy fog and crashed into the bridge just east of the draw, destroying an entire 144 ft, 400 ST) truss span. No one was injured in the crash, although two youths who were stopped on the bridge while the freighter passed were tossed into the river and were subsequently rescued. Once Ilice was freed from the wreckage, she proceeded upriver to Sacramento to take on its scheduled load of rice. The remnants of the destroyed span were cut free from the bridge and dropped into the water. A temporary repair consisting of a steel trestle and two 72 ft steel girders was erected after three weeks, with a ferry carrying traffic across the river while the temporary span was erected.

The Marine Boss crane barge, built for the heavy girder lifts during the construction of the 1967 San Mateo Bridge, erected a permanent 370 ST replacement span (which included a 36 ft cantilevered section to replace damage in the adjacent truss span) in June 1967 and removed both the wreckage from the original bridge and the temporary span at the same time.

Renamed for Helen Madere
In 1998, the Rio Vista Bridge was officially designated the Helen Madere Memorial Bridge after Helen Madere, a former vice-mayor of Rio Vista who served as that city's representative to the Solano Transportation Authority. The legislative act also cited her instrumental role in improving driver safety on California State Route 12.

Proposed replacement
The bridge opened 200 times for ship traffic during peak months in 2004 (nearly seven times per day); peak queues reached 200 vehicles extending 0.75 mi and caused travel delays of up to 30 minutes. With ship traffic projected to increase to require as many as 400 openings by 2035, and traffic on State Route 12 also projected to increase, the City of Rio Vista, the Solano Transportation Authority, and Caltrans have all studied potential replacements for the Helen Madere Bridge. Two goals were first, to remove the drawbridge or at least reduce the necessity of raising the bridge and second, to expand the existing roadway from two lanes to four.

The first study was performed from 1991 through 1994 at the request of the City of Rio Vista, which proposed eight alternatives for crossings at, north of and south of the current SR-12 alignment. Fixed high-level bridges of various designs would require longer approaches to accommodate the required height with reasonable road grades, and resulted in the proposed alternative crossings north and south of the existing SR-12 alignment. Both a mid-level moveable bridge (with approximately 50 ft of clearance with the draw down) and tunnel crossings were proposed for the existing alignment, with the mid-level bridge being named the preferred alternative in 1992.

In 2010, the Solano Transportation Authority expanded on the 1991–94 studies by carefully considering a subset of the proposed alternative crossings, with the tunnel at the existing SR-12 alignment now becoming the preferred alternative. Rio Vista businesses along the existing SR-12 alignment urged no change to the route, worried that moving SR-12 traffic could result in business closures. One of the proposed measures to raise funds would have imposed a toll on the existing bridge, and was met with similar resistance.

Caltrans performed a 2012 study for the entire SR-12 corridor, which concluded the cost of a replacement high-level bridge would be close to US$1000000000 2012. Ultimately, the 2012 study concluded a fixed high-level bridge or a tunnel are the preferred alternatives to allow passage of both ship and road traffic, calling it "the single most important investment that can be made to improve SR-12." The City of Rio Vista dropped its support for the north (Airport Road) alternative alignment in 2012.