Baltimore and Potomac Tunnel

The Baltimore and Potomac Tunnel (or B&P Tunnel) is a double track, masonry arch railroad tunnel beneath Baltimore, Maryland. It now serves Northeast Corridor rail service operated by Amtrak and MARC Train passenger railroads with an average of 135 trains per weekday traversing the tunnel. [cite web|url= http://www.baltimoresun.com/news/traffic/bal-md.rail12jun12,0,3502173.story|title= House OKs funds for tunnel study;Alternative sought to outmoded passage that runs under city|accessdate= 2008-06-13|author= Brown, Matthew Hay|date= 2008-06-12
work= baltimoresun.com|publisher= Baltimore Sun |language= English|quote= The House voted yesterday to authorize $60 million in federal funding to study a way around a 135-year-old rail tunnel that imposes speed and height restrictions on modern passenger and freight trains as they pass through Baltimore.
Lawmakers approved the money as part of a $14.9 billion bill to reauthorize Amtrak for the next five years]

Whether considered a single convert|7669|ft|m|sing=on bore punctuated by two short open cuts, or thought of as a tunnel with three sections, the facility is collectively referred to as the B&P Tunnel and constitutes the southern approach to Pennsylvania Station. It passes under the Baltimore neighborhoods of Bolton Hill, Madison Park and Upton, and is a bottleneck for rail traffic along the Northeast Corridor. [cite web|url=http://www.baltimoresun.com/news/traffic/bal-md.rail12jun12,0,3502173.story|title= House OKs funds for tunnel study; Alternative sought to outmoded passage that runs under city|accessdate= 2008-06-13|author=Brown, Matthew Hay|date= 2008-06-12|work= baltimoresun.com|publisher= Baltimore Sun|language= English|quote= The 7,700-foot passageway, which runs under the neighborhoods of Bolton Hill, Madison Park, and Upton, is considered a choke point for rail traffic along the Northeast Corridor.] A sharp curve at the south portal of the tunnel prevents southbound trains from exceeding convert|30|mi/h|km/h|abbr=on while in the tunnel.http://www.fra.dot.gov/downloads/RRDev/brn1.pdf Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives, November 2006, Page 2.16 ]

An uphill, mile-long, 1.34 percent grade further constrains train performance.

Construction and Modifications

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 (PRR) direct access to Washington, D.C. for the first time by connecting its Northern Central Railway affiliate (which arrived in Baltimore from the north) to the Baltimore and Potomac's Pope's Creek branch, which connected Baltimore to Washington, D.C.

Between 1916 and 1917, the PRR lowered the floor of the tunnel approximately 2-1/2 feet to accommodate larger trains. The work included the underpinning of the side walls, installation of a concrete invert slab, and reconstruction of the track structure. The bases of the tunnel walls were chipped away to improve horizontal clearance.

Prior to the electrification of the PRR's New York City to Washington main line in 1935, the poorly-ventilated tunnel easily filled with smoke from the steam locomotives then in use. The smoke also was a nuisance to the residential neighborhoods above the tunnel.

The tunnel was lined with gunite to waterproof the arch and prevent icicles from shorting out the catenary wires prior to the initiation of electrified operation. However, 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 (completed in the 1930s) would have been used for freight operations.

In the late 1950s, the B&P 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 convert|2200|ft|m to improve clearance and enable high cars and piggyback trailers to traverse the tunnel without damaging their roofs. Additionally, a convert|928|ft|m|sing=on long gantlet track was installed on southbound track 3 to route trains convert|17|in|mm closer to the middle of the tunnel. However, trains could not operate on track 2 while track 3 and the gantlet were being used. The gantlet track effectively created a single-track tunnel when in use; if a freight train broke down while using the gantlet, the tunnel was closed to traffic until the train was moved.

Even with the gantlet, cars with a loading gauge in excess of [http://www.greatnorthernempire.net/index2.htm?GNE_AARCarCodes.htm Plate C] or in excess of convert|16|ft|3|in|m in height were prevented from using the tunnel.

The tunnel underwent rehabilitation as part of the Northeast Corridor Improvement Project in the early 1980s. The repairs included replacing the existing invert, repairing the tunnel lining, upgrading the track structure, installing a new gantlet track, and rehabilitating the tunnel drainage system. No fundamental change, however, was made in the tunnel’s difficult geometry. Eventually, the gantlet track was removed due to changes in freight traffic patterns.

Proposed Replacement

In June 2008 the U.S. House of Representatives voted to support a study of the environmental impacts of different possible replacement tunnels. [ cite web|url= http://www.baltimoresun.com/news/traffic/bal-md.rail12jun12,0,3502173.story
title= House OKs funds for tunnel study; Alternative sought to outmoded passage that runs under city|accessdate= 2008-06-13
author= Brown, Matthew Hay|date= 2008-06-12|work= baltimoresun.com|publisher= Baltimore Sun |language= English
quote= The House voted yesterday to authorize $60 million in federal funding to study a way around a 135-year-old rail tunnel that imposes speed and height restrictions on modern passenger and freight trains as they pass through Baltimore.
Lawmakers approved the money as part of a $14.9 billion bill to reauthorize Amtrak for the next five years] If legislation requiring the study becomes law, the bill only provides the $60 million to conduct the study, not the estimated billions of dollars that will be required for a replacement tunnel. [cite web|url= http://www.baltimoresun.com/news/traffic/bal-md.rail12jun12,0,3502173.story|title= House OKs funds for tunnel study; Alternative sought to outmoded passage that runs under city|accessdate= 2008-06-13|author= Brown, Matthew Hay|date= 2008-06-12
work= baltimoresun.com|publisher= Baltimore Sun |language= English|quote= The bill would authorize $60 million over the next five years for environmental studies of possible rail realignments through Baltimore. Congress could begin appropriating installments next year.
Rerouting rail lines through Baltimore is anticipated to cost billions of dollars.]

References

See also

*Pennsylvania Station (Baltimore)
*Union Tunnel (Baltimore)

External links

"Report To Congress: Baltimore's Railroad Network, Challenges and Alternatives", November 2005
* [http://www.fra.dot.gov/downloads/RRDev/brn1.pdf Part 1: Challenges] , discussing the history and recent state of Baltimore rail infrastructure.
* [http://www.fra.dot.gov/downloads/RRDev/brn2.pdf Part 2: Alternatives] , discussing possible replacement tunnel alignments along Presstman Street (see page 7-7) or US Route 40, among others (see page 7-9).