Chicago redefined the urban nightmare last Monday when a section of abandoned tunnel ruptured and the Chicago River poured into downtown, wreaking hundreds of millions of dollars in damage.
Could such a disaster occur in Baltimore, with its own century-old underground rail tunnels and aging system of water and sewer lines?
Civil engineers contemplating such doomsday scenarios answer simply: No, the Chicago River doesn't come within 500 miles of here.
In fact, the exact circumstances facing the Windy City are unique and unlikely to be duplicated elsewhere.
But that doesn't mean Baltimore is in the clear. Experts say that below the surface of city streets there are potential crises lying in wait.
The culprit: infrastructure neglect. For too long, Baltimore, like most other communities across the country, has allowed its infrastructure -- its networks of highways, bridges, underground pipes and sewage plants -- to deteriorate.
"The older and the bigger the city, the more problems that you'll have," warned Max Whitman, president of the Chicago-based American Public Works Association. "Decaying underground facilities pose one of our greatest problems."
Mr. Whitman and others believe the country has deferred routine maintenance for too many years. Government investment in public works has declined from 20 percent of total expenditures in 1950 to 7 percent by 1984, according to the association.
As a whole, the United States spent about 0.3 percent of its gross national product on infrastructure between 1980 and 1989. Canada spent six times as much, Germany 12 times that amount and Japan invested 5.7 percent of its GNP, or 19 times what the United States did.
Baltimore, like other communities -- particularly in the older Northeast -- has seen its share of water and sewer spillages, power outages, leaking underground gas tanks and other small-scale catastrophes. There are water lines that are 80 or 90 years old, and engineers can only marvel that they've lasted as long as they have.
"Water doesn't run uphill"
But the primary reason the city is unlikely to experience Chicago-size flooding is a simple matter of physics: Water runs downhill. The city is built above sea level, and excess water would drain toward the harbor.
"Water doesn't run uphill yet," said George G. Balog, Baltimore's public works director.
Beneath Baltimore is a veritable web of structures that make the city work: pipelines, steam lines, utility conduits and tunnels.
The newest of the tunnels belongs to Metro, which operates three miles of track underground and is tunneling 1.5 miles more with an extension to Johns Hopkins Hospital.
Perhaps the most significant Metro-related problem developed in November 1990 when workers digging underneath Orleans Street caused a water main to break. The gushing water swept away tons of soil, and the resulting cave-in severed utility lines and left behind a 25-foot-wide, 12-foot-deep crater.
But the incident was isolated. Finished tunnels have posed no such problems, and the normal water seepage can be easily accommodated by the Metro's system of sump pumps, said Peter J. Schmidt, who oversees Metro construction for the Mass Transit Administration.
"It's extremely unlikely that we could get flooded, and even if we did, we couldn't affect anyone else," Mr. Schmidt said.
The oldest tunnels
The oldest of Baltimore's tunnels serve railroads: the mile-long Baltimore and Potomac Railroad tunnel, which runs into Penn Station from the west; the half-mile-long Union Tunnel, which runs from Penn Station to the east; and the Howard Street Tunnel, which carries CSX trains underground from Mount Royal Station south to Camden Station.
Officials with Amtrak and CSX Transportation Inc. insist that the tunnels are in good shape despite their age, that they undergo regular inspections and that they pose no danger to the public.
The Baltimore and Potomac, for instance, dates to 1873 but is constructed of limestone walls 4 to 6 feet thick and is an average of 25 feet above sea level.
"Even if there was a rupture of a city water main, the Howard Street tunnel is so large and the grade is straight down toward the Patapsco [River], it's not possible for it to flood," said Lynn Johnson, a CSX spokesman.
Concern for Roland Dam
One of the only city-owned projects that could approach the scale of Chicago's disaster, if it broke, is Lake Roland Dam in Robert E. Lee Park, just over the northern city line in Baltimore County.
The dam, built in 1862, for years has been showing signs of age, and its weakness has concerned city and state officials, especially during heavy storms.
If it collapsed, it would send a wall of water roaring down the Jones Falls Valley, with 2,000 residents in its immediate path.
A state dam official recently termed the structure "a major disaster waiting to happen."
"The dam has to be fortified," Mr. Balog said, noting that the first phase of repairs is already under way.