Leonard P. Zakim Bunker Hill Memorial Bridge

Zakim Bunker Hill Bridge
Zakim Bunker Hill Bridge
	; Zakim Bunker Hill Bridge
Official name	Leonard P Zakim-Bunker Hill Memorial Bridge
Carries	Interstate 93 and U.S. Route 1
Crosses	Charles River
Locale	Boston, Massachusetts
Maintained by	Massachusetts Turnpike Authority
Design	Hybrid Steel and Concrete Cable-stayed bridge
Longest span	745 ft (227.1m)
Total length	1432 ft (436.5m)
Width	183 ft (55.7m)
Height	270 ft (98.4m)
Clearance below	40 ft (12.2m)
Opening date	March 30, 2003 (NB); December 20, 2003 (SB)
Coordinates	42°22′07.5″N 71°03′47.5″W / 42.36875°N 71.063194°WCoordinates: 42°22′07.5″N 71°03′47.5″W / 42.36875°N 71.063194°W
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The Leonard P. Zakim Bunker Hill Memorial Bridge is a cable-stayed bridge across the Charles River in Boston, Massachusetts. It replaced the Charlestown High Bridge when it opened, and is the world's widest cable-stayed bridge. The main portion of the Zakim Bridge carries four lanes each northbound and southbound of the Interstate 93 and U.S. Route 1 concurrency between the Thomas P. "Tip" O'Neill Jr. Tunnel and the elevated highway to the north. Two additional lanes are cantilevered outside the cables, which carry northbound traffic from the Sumner Tunnel and North End on-ramp. These lanes merge with the main carriageway north of the bridge. I-93 heads toward New Hampshire as the "Northern Expressway" and US 1 splits from the Interstate and travels northeast toward Massachusetts' north shore, crossing the Mystic River via the Tobin Bridge.

The bridge and connecting tunnel were built as part of the Big Dig, the largest highway construction project in the United States. Finished in 2003, the bridge's unique styling quickly became an icon for Boston, often featured in the backdrop of national news channels to establish location, and included on tourist souvenirs. The bridge is commonly referred to as the "Zakim Bridge" and as the "Bunker Hill Bridge" by residents of nearby Charlestown.

The Leverett Circle Connector Bridge was constructed in conjunction with the Zakim Bridge, allowing some traffic to bypass it.

[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.

The bridge concept was developed by Swiss civil engineer Christian Menn and its design was engineered by American civil engineer Ruchu Hsu with Parsons Brinckerhoff. Boston-based architect Miguel Rosales was the lead architect/urban designer and facilitated community participation during the design process. Neither Hsu nor Rosales served as the designer of record for the project. The engineer of record is HNTB/FIGG. The lead designer from HNTB was Theodore Zoli; and W. Denney Pate from FIGG. The bridge follows a new design in which two outer lanes are cantilevered outside of the wires another eight lanes run through the towers. It has a striking, graceful appearance that is meant to echo the tower of the Bunker Hill Monument, which is within view of the bridge, and the white cables evoke imagery of the rigging of the USS Constitution.

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] While the highest wind gusts recorded in Boston were 110 MPH (175 km/h), the bridge is overengineered and is designed to withstand 400 MPH (640 km/h) winds.^[4]

The MBTA Orange Line tunnel lies beneath the bridge.

[edit] Name

Image of the dedication plaque for the bridge

The bridge's full name commemorates both Boston civic leader and civil rights activist Leonard P. Zakim, who championed "building bridges between peoples,"^[5] and the Battle of Bunker Hill. Originally Massachusetts Governor A. Paul Cellucci sought to name it the "Freedom Bridge," however in 2000 local clergy and religious leaders, including Cardinal Bernard Francis Law, requested the Zakim name shortly after Mr. Zakim's death from myeloma. Gov. Cellucci agreed to the naming, however community leaders from the insular community of Charlestown objected to the name as they felt that since the design reflected the nearby Bunker Hill memorial, it should be named the "Bunker Hill Freedom bridge". Allegations of antisemitism were leveled against members of the mostly white, Christian community as reasons for resistance to the Zakim name after questionable quotes appeared in an article in the Boston Globe. However, several community leaders spoke out against the allegations in a press conference, stating that the claims, made by Professor Jonathan Sarna, were his alone and not reflected in the Jewish community at large.^[6]

Eventually a compromise between the Boston City Council, the state Massachusetts State Legislature and community activists brought about the current name. However like the Hoover Dam, different communities will call the bridge by different colloquial names. Many people in the Charlestown area refer to it as the "Bunker Hill bridge," while most, including the local press and traffic monitoring services, refer to it as the "Zakim Bridge."

At the time of the naming and sponsoring of the Boston Garden an article discussing appraisals of the other Boston landmarks suggested the probable amount that the naming of the bridge would have cost a sponsor would have been US$100,000,000.^{[citation needed]}

[edit] Pachyderm Test

On 14 October 2002, elephants from the Ringling Brothers and Barnum & Bailey Circus crossed the new Leonard P. Zakim Bunker Hill Memorial Bridge to demonstrate the bridge's structural integrity. The 14 elephants proved that the bridge supports 112,000 pounds. The Boston elephant march resembled tests of the 1800s when bridge engineering was more questionable. Elephants were used to demonstrate the sturdiness of the St. Louis Bridge in 1874 and the Brooklyn Bridge in 1884. According to folklore, elephants are used for such shows of strength because they are widely believed to have uncanny instincts and will not cross unsafe structures.^[7]

[edit] Notes

Although the bridge was completed in 2002, it 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 Bunker Hill cable-stayed bridge has been widely seen as an improvement; it acts as a complete replacement for the previous three-lane, dual height steel bridge, the Charlestown High 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 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.^[8]
The Travel Channel ranked the Zakim Bridge 9th in their list of the World's Top Ten Bridges. The article also points out that the bridge is the widest cable-stayed bridge in the world and boasts a total of 10 lanes for traffic.^[9]

[edit] Gallery

Northbound from Clinton Street in Boston	Detail of the cabling and tower on the bridge	Traveling south on the Zakim-Bunker Hill Bridge	The bridge during its construction
The bridge with Boston in the background