LOS ANGELES — The scene was apocalyptic: a torrent of water from a ruptured pipe valve bursting through Sunset Boulevard, hurling chunks of asphalt 40 feet into the air as it closed down the celebrated thoroughfare and inundated the campus of the University of California, Los Angeles. By the time emergency crews patched the pipe, 20 million gallons of water had cascaded across the college grounds.

The failure of this 90-year-old water main, which happened in July in the midst of a historic drought, no less, was hardly an isolated episode for Los Angeles. Instead, it was the latest sign of what officials here described as a continuing breakdown of the public works skeleton of the second-largest city in the nation: its roads, sidewalks and water system.

With each day, it seems, another accident illustrates the cost of deferred maintenance on public works, while offering a frustrating reminder to this cash-strained municipality of the daunting task it faces in dealing with the estimated $8.1 billion it would take to do the necessary repairs. The city’s total annual budget is about $8.1 billion.

Los Angeles’s problems reflect the challenges many American cities face after years of recession-era belt-tightening prompted them to delay basic maintenance. But the sheer size of Los Angeles, its reliance on the automobile and, perhaps most important, the stringent voter-imposed restrictions on the government’s ability to raise taxes have turned the region into a symbol of the nation’s infrastructure woes.