Baltimore and Potomac Tunnel


The Baltimore and Potomac Tunnel is a double-tracked, masonry arch railroad tunnel on the Northeast Corridor in Baltimore, Maryland, just south of Pennsylvania Station. Opened in 1873, the tunnel is used today by about 140 Amtrak and MARC passenger trains and two freight trains every day.
The tunnel, which passes under the Baltimore neighborhoods of Bolton Hill, Madison Park, and Upton, consists of three tunnels —Gilmor Street Tunnel, Wilson Street Tunnel, and John Street Tunnel—separated by two open-air cuts: Pennsylvania Avenue Opening and John Street Opening.

History and operations

Constructed by the Baltimore and Potomac Railroad under Winchester Street and Wilson Street in Baltimore, the tunnel opened on June 29, 1873. The B&P tunnel allowed the Pennsylvania Railroad direct access to Washington, D.C., for the first time by connecting its Northern Central Railway affiliate to the Baltimore and Potomac's new spur, which ran to Washington.
Between 1916 and 1917, the PRR expanded the tunnel to accommodate larger trains. The railroad lowered the floor of the tunnel about feet, underpinned the side walls, installed a concrete invert slab, and rebuilt the track structure. The bases of the tunnel walls were chipped away to improve horizontal clearance.
Before the PRR's electrified its New York City-to-Washington main line in 1935, the poorly ventilated tunnel filled with smoke from steam locomotives. The smoke also was a nuisance to the residential neighborhoods above the tunnel.
In preparation for electrified operation, the tunnel was lined with gunite to waterproof the arch and prevent icicles from shorting out the catenary wires.
Financial considerations prevented the PRR from constructing a new passenger tunnel on the Presstman Street alignment, for which it previously had acquired rights. The PRR's plan had envisioned using the new Presstman Street tunnel and the original bores of the Union Tunnel for passenger operations, while the old B&P Tunnel and the newer bores of the Union Tunnel would have been used for freight operations.
In the late 1950s, the tunnel became a hindrance to the growth of PRR's Trailer-on-Train service, which required additional vertical and horizontal clearance to accommodate semi-trailers on top of railroad flatcars. The curve at Pennsylvania Avenue was the biggest constraint. The PRR modified the tunnel walls and ceiling for a distance of to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs. Additionally, a gauntlet track was installed on southbound Track 3 to route trains closer to the middle of the tunnel. However, the gauntlet track effectively created a single-track tunnel. No trains could run on Track 2 while the gauntlet was in use; a broken-down train on the gauntlet closed the tunnel to traffic until it could be moved.
Even with the gauntlet, cars that were taller than or with a loading gauge in excess of could not use the tunnel.
In the early 1980s, the tunnel underwent rehabilitation as part of the Northeast Corridor Improvement Project. The repairs included replacing the existing invert, repairing the tunnel lining, upgrading the track structure, installing a new gauntlet track, and rehabilitating the tunnel drainage system. No fundamental change was made in the tunnel's difficult geometry. Eventually, the gauntlet track was removed due to changes in freight traffic patterns.

Problems

The tunnel has long been one of the worst bottlenecks for rail traffic along the Northeast Corridor and maintaining it is costly:
Collectively, the tunnel's height, speed, and capacity limitations threaten the ability for the Port of Baltimore to be competitive with increased shipping volumes.

Plans for improvements

In June 2008, the U.S. House of Representatives voted to support a study of the environmental impacts of different possible replacement tunnels. On January 28, 2010, $60 million in funding was awarded under the American Recovery and Reinvestment Act to conduct the study, but not the money that will be required for a replacement tunnel. Estimates in 2013 put the cost around $1.5 billion.
An outgrowth of the ARRA funds, the B&P Tunnel Project is an environmental and engineering study by the FRA, MDOT, and Amtrak to evaluate potential improvements to the tunnel. The study has held multiple open houses in 2014-2015 to share information and solicit public input.

Preliminary Alternatives

In December 2014, the study published the Preliminary Alternatives Screening Report, in which four alternatives from a total of 16 were selected to be carried forward for further consideration and study:
Among the criteria used to evaluate the alternatives was the ability to accommodate double-stack container cars.
The 12 eliminated alternatives included those with alignments that varied greatly from the existing alignment and bypassed Pennsylvania Station entirely, those that reused one or more of the three existing tunnel sections, and one that would have utilized the former I-170 "Highway to Nowhere" right of way.

Final Alternatives

In October 2015, the study published the Alternatives Report, in which two of the preliminary alternatives—Alternative 2 and Alternative 11 —were eliminated from further consideration due to concerns such as their greater impact and disruption to the community, greater disruption to existing train service, and greater cost. The two remaining alternatives—Alternative 1 and Alternative 3 —will be carried forward, studied, and evaluated further in the next milestone, the Draft Environmental Impact Statement.

Selected Alternative

In November 2016, Alternative 3B was specified as the preferred alternative in the Final Environmental Impact Statement over Alternative 1 and two other variations of the Great Circle Alternative. Highlights of Alternative 3B are:
The Federal Railroad Administration released its Record of Decision on the new tunnel, the final step in the NEPA process, in March 2017.