Zakim Bunker Hill Bridge

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**Zakim Bridge**
Leonard P. Zakim Bridge
Official name	Leonard P Zakim-Bunker Hill Memorial Bridge
Carries	Interstate 93 and U.S. Route 1
Crosses	Charles River
Locale	Boston, Massachusetts
Design	Hybrid Steel and Concrete Cable-stayed bridge^[1]
Longest span	227.1m (745 ft)
Total length	436.5m (1432 ft)
Width	55.7m (183 ft)
Clearance below	12.2m (40 ft)^[2]
Opening date	March 30, 2003 (NB) December 20, 2003 (SB)^[2]
Coordinates	42°22′09″N, 71°03′51″W
Maps and aerial photos Street map from Google Maps or Yahoo! Maps Topographic map from TopoZone Aerial image or topographic map from TerraServer-USA Satellite image from Google Maps or Microsoft Virtual Earth

The Leonard P. Zakim Bunker Hill Memorial Bridge is a cable-stayed bridge that carries eight lanes of the Interstate 93 and U.S. Route 1 concurrency, plus a two lane access ramp, across the Charles River in Boston, Massachusetts. The bridge was built as part of the Big Dig, the largest overall highway construction project in the United States. The entrance to the Thomas P. "Tip" O'Neill Jr. Tunnel, another major component of the Big Dig, is at the bridge's southern end, while north of the bridge I-93 heads toward New Hampshire and US 1 splits from the Interstate and travels northeast toward Massachusetts' north shore, crossing the Mystic River via the Tobin Bridge. The bridge replaced the Charlestown High Bridge when it opened, and was the widest cable-stayed bridge built prior to 2003. The bridge is now a major landmark and has been featured in several films recently including the 2005 version of War of the Worlds and often serves as a backdrop for interviews.

1 Design
2 Name
3 Notes
4 References
5 External links

[edit] Design

In a cable-stayed bridge, instead of hanging the roadbed from cables slung over towers, the cables run directly between the roadbed and the towers. Although cable-stayed bridges have been common in Europe since World War II, they are relatively new to North America.

On the Zakim Bunker Hill Bridge, traveling southbound

The bridge concept was developed by Swiss civil engineer Christian Menn and its design was engineered by American civil engineer Ruchu Hsu. It follows a new design in which two outer lanes are cantilevered outside the towers while another eight lanes run through the towers. It has a striking, graceful appearance that is meant to echo the towers of the Bunker Hill Monument, which is within view of the bridge, and the white cables evoke imagery of the sails of the USS Constitution.

According to the Massachusetts Turnpike Authority's web site, the bridge has an overall length of 436.5 m, a main span of 227.1 m, side spans of 81.4 m (downtown side) and 128.0 m (Charlestown side), and towers that are 82.3 m tall.^[1]

[edit] Name

The bridge's full name commemorates both Boston civic leader Leonard P. Zakim, who championed "building bridges between peoples", and the Battle of Bunker Hill, but locally it is often referred to simply as "The Zakim Bridge".

[edit] Notes

The bridge during its construction

Although the bridge was completed in 2002, the new bridge was not opened to traffic until the northbound Central Artery tunnel opened in early 2003. The southbound lanes were opened in December 2003, with the opening of the southbound tunnel, and the cantilevered northbound lanes (a two-lane entrance ramp) opened in April 2005, when the old bridge was sufficiently demolished to allow for their completion.

The Zakim cable-stayed bridge has been widely seen as an improvement; it acts as a complete replacement for the previous two-lane, dual height steel bridge. The different heights of the lanes of the I-93 elevated highway in Charlestown are the only remaining hints to the layout of the old bridge.

In March of 2005, problems arose when it became apparent that ice falling off the cables during the course of winter could land on the roadway below in large enough chunks to possibly endanger motorists, or even break windshields. Some motorists are left feeling compelled to keep one eye on the road ahead and another on the cables above while driving across the bridge.^[3]