The Lake Pontchartrain Causeway, or the Causeway, consists of two parallel bridges crossing Lake Pontchartrain in southern Louisiana. The longer of the two bridges is either the longest or second-longest in the world depending on definitions, measuring at long. The Bang Na Expressway, a viaduct in Bangkok, is longer at , but is excluded from most lists of longest bridges because it crosses water for only a minimal portion of its length.

The bridges are supported by 9,500 concrete pilings. The two bridges feature bascule spans over the navigation channel south of the north shore. The southern terminus of the Causeway is in Metairie, Louisiana, a suburb of New Orleans. The northern terminus is at Mandeville, Louisiana.

History

The idea of a bridge spanning Lake Pontchartrain dates back to the early 19th Century and Bernard de Marigny, the founder of Mandeville. He started a ferry service that continued to operate into the mid-1930s. In the 1920s, a proposal called for the creation of artificial islands that would then be linked by a series of bridges. The financing for this plan would come from selling homesites on the islands. The modern Causeway started to take form in 1948 when the Louisiana Legislature created what is now the Causeway Commission.

The original Causeway was a two-lane span, measuring in length, that opened in 1956 at a cost of $30.7 million. A parallel two-lane span, 1/100th of a mile (15 m) longer than the original, opened on May 10, 1969 at a cost of $26 million. The Causeway has always been a toll bridge. Until 1999, tolls were collected from traffic going in each direction. To alleviate congestion on the south shore, toll collections were eliminated on the northbound span. The standard tolls for cars changed from $1.50 in each direction to a $3.00 toll collected on the North Shore for southbound traffic only.

The opening of the Causeway boosted the fortunes of small North Shore communities by reducing drive time into New Orleans by up to 50 minutes, bringing the North Shore into the New Orleans metropolitan area. Prior to the Causeway, residents of St. Tammany Parish had to go around the lake, either the east side via the Rigolets Bridge on U.S. Route 90 near Slidell, Louisiana or on the west side via U.S. Route 51 through Manchac, Louisiana.

After Hurricane Katrina on August 29 2005, videos collected showed damage to the bridge, but the damage was mostly on the unused turnaround on the older southbound span; the structural foundations remained intact. The Causeways have never sustained major damage of any sort due to hurricanes and other natural occurrences, a rarity in the causeway community. The existing fiber optic cable plant was blown out of the tray but remained intact per optical time domain reflectometer (OTDR) analysis. With the I-10 Twin Span Bridge severely damaged, the Causeway was used as a major route for recovery teams staying in highlands to the North to get into New Orleans. The Causeway reopened first to emergency traffic and then to the general public, with tolls suspended, on September 19, 2005. Tolls were reinstated by mid-October.

The Lake Pontchartrain Causeway is one of six highway spans in Louisiana that have a total length of or more. The others are, in order from longest to shortest, the Manchac Swamp bridge on I-55, the Atchafalaya Basin Bridge on I-10, the Bonnet Carré Spillway bridge on I-10, the Chacahoula Swamp Bridge on U.S. 90, the Lake Pontchartrain Twin Spans on I-10, and the Destrehan Swamp Bridge on I-310. The Maestri Bridge comes close, but runs short two tenths of a mile at roughly in total length. In a few years the Leeville-Port Fourchon Bridge on Louisiana Highway 1 at over in total length will join this list. Louisiana is also home to the Norfolk Southern Lake Pontchartrain bridge, which at is one of the longest railway bridges in the United States.

It should be noted that the southern end of the Manchac Swamp bridge is the western end of the Bonnet Carré Spillway bridge and the northern end of the Destrehan Swamp bridge is the eastern end of the Bonnet Carré Spillway bridge, so these three bridges by name are in fact one contiguous bridge. The combined driving distance is over .

Major barge accidents

The Causeway has been struck by barges on three occasions that have caused structural damage resulting in the collapse of portions of the roadway.

• January 17, 1960, an empty barge struck the bridge in heavy fog in the morning. Two of the Causeway's spans collapsed and a third was damaged. There were no fatalities.
• June 16, 1964, a tugboat pushing two barges collided with the bridge in the early morning causing four spans to collapse into the lake. A Continental Trailways bus fell into the lake killing six people.
• August 1, 1974, several barges collided with the new northbound span collapsing several spans and sending several vehicles into the water, killing three people.

Regulations

• Currently both spans have a speed limit during the day barring fog, rain or high wind. This was increased from in 2004 in order to increase safety on the span and reduce travel time by 4 minutes. However, the southbound span has night time sight line problems at the span's rises, requiring a speed limit of over the humps. The Causeway Commission is studying the expense of lighting the rises on the southbound and possibly the northbound span.

Third span plans

In 2002, the Causeway Commission discussed the construction of a third span before ultimately deciding to renovate the existing spans as studies showed traffic growth leveling off. The third span was estimated to have cost $400 million, which by 2006 had risen to $800-900 million. In the aftermath of Hurricane Katrina, traffic has grown to 40,000 vehicles per day as the population of North Shore parishes have rapidly increased. A 1992 traffic study predicted the traffic capacity of the current spans would be exceeded in 2007; an estimate that was later revised to an earlier date and rendered useless by Katrina related population shifts.

In early March 2006, General Manager Robert Lambert acknowledged that the Commission may revisit the plan for a third span. Lambert cited the increase in traffic and the need for better evacuations routes to the north as the leading reasons for reexamining the need for a new span. The proposed third span would be east of the current northbound span and include two travel lanes and a full right-hand shoulder. The current southbound span would also be fitted with a full shoulder. The current northbound span would then be used as a one lane with full shoulder reversible roadway to correspond with peak travel hours.

See also

• List of bridges in the United States
• List of bridges by length
• Megaproject
• Prestressed concrete

References

1. PILE RESTORATION OF THE LAKE PONTCHARTRAIN CAUSEWAY
2. Hazardous crossings - Graphics - Times-Picayune - NOLA.com
3. http://www.nola.com/newslogs/tpsttammany/ "Nighttime speed limit going up on southbound Lake Pontchartrain Causeway" NOLA.com

External links

• The Causeway website
• Google Maps satellite image