The Howard Street Tunnel has been a headache from the day its opened in 1895. It drove the railroad that built it into bankruptcy. It's been obsolete for decades. A derailment and chemical fire in 2001 showed it to be a bottleneck for East Coast freight rail traffic.
And it's likely to remain that way for a long time. Alternatives have been proposed, but any of them would be costly and take decades to build. CSX Transportation, the tunnel's owner, seems in no rush to replace it.
"For the foreseeable future, that tunnel is an important part of our network," said railroad spokesman Bob Sullivan.
Marylanders received a rude reminder of the tunnel's vulnerability last weekend when 12 cars of a CSX train derailed just south of the tunnel's portal near M&T Bank Stadium.
Three of the cars were carrying hazardous materials, but there was no release of toxic substances and no injuries. Unlike in 2001, there was no prolonged paralysis of rail traffic and no evacuation of downtown buildings.
Nevertheless, the second serious CSX derailment in or near the tunnel this decade brought expressions of concern from city leaders about the safety of transporting hazardous substances on a rail route through central Baltimore.
The tunnel itself is an accident of history and geography.
Back in the 1890s, the Baltimore & Ohio Railroad wanted to run an elevated line heading east from Camden Station near the Inner Harbor to complete a connection between Washington and Philadelphia. The catch was that downtown Baltimore was in the way.
So the ancestor of today's CSX Transportation settled for building a 1.4 mile-long tunnel under Howard Street to bypass downtown. The construction costs escalated to a then-whopping $2.2 million, landing the B&O in bankruptcy court.
Slow, steep century
For 112 years since then, the tunnel has been a challenge to operate - with its too-steep inclines, too-curvy route and single-track capacity.
After the 2001 fire, Sen. Barbara A. Mikulski and then-Sen. Paul S. Sarbanes got an earmark for a study of Baltimore's rail tunnels into a federal appropriations bill.
Superimposing a new railroad line on a built-up urban area is no easy undertaking, however. A Federal Railroad Administration report, released in 2005, looked at more than a dozen theoretical routes for a new freight tunnel and winnowed the alternatives down to three options the agency considered viable. The estimated cost of the three options ranged from $865 million to $3.1 billion.
Two of the options would roughly follow existing rail lines through Southwest Baltimore to what would be called the Great Circle Freight Tunnel, to be bored deep underneath the current Amtrak Northeast Corridor line.
The third, and most expensive, proposal would be a tunnel under Baltimore Harbor between Marley Neck and Sparrows Point. The study said the cost would be three times that of the other alternatives but noted that the long-term benefits would have to be weighed against the short-term costs.
The authors proposed a tunnel large enough to accommodate the double-stack trains that have become standard in the freight rail industry. The current tunnel is not high enough to accommodate such trains - putting the port of Baltimore at a disadvantage to its rivals in Norfolk, Va., New York and Philadelphia.
The study set a goal of reducing the steepness of the incline of the tracks - known as the grade.
Also hampering traffic flow on the CSX line through Baltimore is the curvature of the track in the tunnel and on the northern and southern approaches - with one especially sharp curve at the site where some of the cars derailed last weekend. Partly because of those curves, freight traffic in the area operates under severe restrictions that limit speeds to 25-30 mph. The study calls for a route that reduces the curves and allows greater speeds.
The working assumption is that the federal government, Maryland and the privately owned railroads operating in the corridor would all contribute - but nobody has come up with a formula for sharing the costs.
"That's probably more daunting than the technical challenges," said Dave Ganovski, director of the Maryland Department of Transportation's Office of Freight Logistics. "We don't have an easy answer for that."
A study, soon to be launched by the state and federal governments, is expected to weigh the issues of who benefits and who should pay.
Among the potential beneficiaries of a new tunnel would be the Maryland Transit Administration, which this year released a long-term plan that envisions using a freight-free Howard Street Tunnel to extend MARC commuter rail operations on the Camden Line to Johns Hopkins Bayview Medical Center by 2035.
But achieving that faraway goal will not be easy. There will be environmental hurdles to clear. Federal and state lawmakers would have to be persuaded to spend money on a project few constituents would ever see. Government officials would have to negotiate deals with railroad executives who might be more worried about the next quarter than the next century.
Even if everything falls into place, freight likely will be moving through the 1895 tunnel well into the 2020s.
"People would generally say a project of this magnitude is a 20-year project," Ganovski said. "Everybody's trying to figure out what's the next move to make."