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News January 03, 2002
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If there is one prevailing maintenance concern for any city, county or state transportation authority - it's the pothole

If there is one prevailing maintenance concern for any city, county or state transportation authority - it's the pothole. New York City is no different. In fact, potholes were so bad in "The Big Apple" that Mayor Rudolph Giuliani declared a comprehensive citywide Pothole Repair Blitz in December of 2000. The New York City Department of Transportation responded by repairing more than 70,000 potholes since the declaration. Recent polls have indicated that the New York metropolitan area now ranks 16th in potholes/related-car-repair-costs out of the 50 largest metropolitan areas. Though there is a lot of progress to be made, this is a valiant effort considering New York's vast transit system, huge traffic numbers and 14.4 million people.

The New York City DOT receives most of the credit for this pothole progress, but another agency's efforts that should not be overlooked is Metropolitan Transportation Authority Bridges & Tunnels (MTAB&T). Bridges & Tunnels is a constituent agency of the Metropolitan Transportation Authority, which also manages the New York City Transit Authority, the commuter railroads (MetroNorth and Long Island Railroad) and all of the major toll bridges and tunnels within the city.

It is MTA's Bridges and Tunnels that deserves considerable credit for maintaining and reducing the pothole concerns for some of the most heavily traveled areas of New York City. MTA's seven bridges and two tunnels carry nearly 300 million vehicles annually, which is more than any bridge and tunnel authority in the nation. The bridges include the Triborough, Throgs Neck, Verrazano-Narrows, Bronx-Whitestone, Henry Hudson, Marine Parkway-Gil Hodges Memorial and the Cross Bay Veterans. The two tunnels overseen by MTA are the Brooklyn-Battery and the Queens Midtown. As with any other road surface, bridges and tunnels suffer from the same pothole plague and formation process. As with any pothole, first there is an infiltration of water under the road surface, followed by subsequent freeze/thaw cycles and constant traffic. But what makes the pothole problem different with bridges and tunnels is the unique maintenance challenge these structures present.

No other way

With other metropolitan side streets and thoroughfares, there are alternatives. If one particular street is in need of major pothole repair, there are usually other streets in which traffic can be detoured. Though an annoyance to the traveler, the option is at least feasible. But in the case of bridges and tunnels, the demands are much greater. Completed in July of 1936, the Triborough Bridge has seen more than 2.8 billion vehicles cross its 65-year-old surface. Last year alone, more than 64 million vehicles crossed the Triborough, and it currently boasts an average daily traffic of 170,000 vehicles. When major potholes crop up, there is no simple detour for the Triborough Bridge and the 170,000 people driving across it each day would not readily accept lane closings and/or major delays to repair potholes. Thus, MTA Bridges and Tunnels has implemented a quick, yet effective method of pothole repair for its most demanding structures - spray injection pothole patching.

Spray injection pothole patching involves a four-step process. First, using a high-volume blower, the pothole is cleaned, removing rocks, debris and moisture. Next, a tack coat of hot emulsion is applied to the area in need of repair. Third, a mixture of aggregate and hot emulsion is dropped into the hole to fill the depression. Lastly, a top layer of dry aggregate is applied and traffic can flow immediately. Though one of the fastest and cheapest pothole repair methods available, a study conducted by the Strategic Highway Research Program (SHRP) in 1992 found it to be one of the most effective and long-lasting techniques as well. In fact, some state DOT research councils have found spray injection pothole patches to last up to five years - or three to five times longer than traditional methods.

MTA Bridges and Tunnels currently has two Rosco RA-300 spray injection pothole patching trucks dedicated to maintaining their seven bridges, which includes two of their most demanding structures - the Verrazano-Narrows and Triborough Bridges.

Named after Giovanni de Verrazano, who, in 1524, was the first European explorer to set sail into New York Harbor, the Verrazano-Narrows Bridge spans from the historic Fort Hamilton in Brooklyn to Fort Wadsworth in Staten Island. When it opened in 1964, the Verrazano was the world's longest suspension span and today is only surpassed by the Humber Bridge in England. It's large 693-ft high towers are 1 5/8 in. farther apart at their tops than at their bases because the 4,260 ft distance between them makes it necessary to compensate for the earth's curvature. Whereas the Triborough's main challenge involves traffic, the Verrazano requires a mobile pothole solution that can easily cover its incredible distance.

For more on the story, read the January issue of ROADS&BRIDGES.

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