Restoration work for a rail-to-trail with a lift—elevated 18 ft to 20 ft on an abandoned trestle—is called “an engineer’s dream,” even though parts of the 71-year-old steel structure, not used for commerce since 1980, were in “terrible condition,” says the structural engineer charged with preserving the section of the trestle that slices through, between and above 10 blocks of buildings and streets on Manhattan’s West Side. It is a dream because the elevated rail line, renamed the High Line in its reincarnation as a linear urban park, was designed for a 10,000-psf live load during its active years, when trains hauled food from the city’s meat-packing district toward markets to the north.
For the park elements, the live-load requirement is only 300 to 600 psf, depending on plantings, so for the most part, “we could leave the steel in its deteriorated state” and simply clean it with power tools and paint it, says Joseph F. Tortorella, a vice president with Robert Silman Associates, the local engineer charged with historic preservation for the eventual 20-block-long High Line, which opened in early June. Only a few areas required reinforcement with steel plates welded to the surface, he adds.