THE 151-foot midriff section of Third Avenue Bridge swings open at a 90-degree angle, allowing oversize barges plying the Harlem River to pass beneath it. Dubbed ``2-40069'' by inspectors, it juts into a New York City skyline cut by the humped double arches of the Triborough Bridge, the steel latticework of the Willis and Madison Avenue bridges, and the blue towers of the Metro North railroad bridge. On the third day of a two-week inspection, Richard Nyman stands in a cherry picker illuminated by three generator-powered lamps and pounds away with a chip hammer at an 18-inch crack scarring the underside of the bridge. Mr. Nyman, leader of a three-man inspection team, is carving out bits of encrusted rust to measure the extent of corrosion in the steel stringers that support part of the superstructure.
Using an ultrasonic testing device, he discovers that the decay warrants a ``flag,'' indicating the imminent failure of a major structural component. After photographing the trouble spot, he adds another detailed entry to a growing 49-page inspection report.
Bridge inspectors work in anonymity, among the shadows cast by abutments and girders. But since cracks in a floor beam forced last month's closing of the Williamsburg Bridge, diverting 240,000 commuters who depend on it for daily passage between Brooklyn and Manhattan, the city's inspectors have been pushed into the public spotlight.
``When a patient dies, they bury him,'' says Salomon Bokman. ``But when a bridge dies, they bury the inspector.''
Mr. Bokman and his bridge inspection teams from the consulting engineering firm Hardesty & Hanover are on the front lines of a battle to chart the condition of New York City's battered bridges.
Transportation officials say the closing of the Williamsburg Bridge illustrates dramatically the ills of New York's bridge system. They warn that years of neglect have left nearly half of the city's 2,098 bridges in need of major reconstruction or rehabilitation.
New York City's bridges span rivers, bays, canals, rail lines, and roadways to form a metropolis. The city's transportation department estimates that more than 160 million trips are made daily across New York's bridges. Yet 371 city-owned bridges are rated structurally deficient, and 32 bridges are completely or partly closed, according to the transportation department's 1987 condition report on bridges and tunnels.
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