The Fort McHenry Tunnel is an 8 lane tunnel complex where I-95 crosses underneath Baltimore Harbor, which is the tidal part of the Patapsco River. The tunnel was named after the historic Fort McHenry, which the tunnel passes almost directly beneath. At its time of construction, the Fort McHenry Tunnel was the most expensive single project in the entire Eisenhower Interstate System, and cost an extimated 750 million dollars to construct when it opened in 1985. Total costs of completing I-95 through Baltimore came to nearly 1 billion dollars, including the approach roadways that were yet to be completed by 1981. Since then its size and scope has only been exceeded by the huge Boston Central Artery Project, known as the Big Dig.


The Fort McHenry Tunnel was designed to complete a major gap in the interstate highway system where it crossed Baltimore Harbor. The new tunnel would also ease severe traffic congestion on the Baltimore Harbor Tunnel Thruway, which opened in 1957 but was only a 4 lane roadway. In 1970 a plan to build a bridge to cross Baltimore Harbor was stopped by residents, who objected by the bridge on grounds it would ruin the aethetics of historic Fort McHenry, and the Locust Point neighborhoods. The commission decided that despite the additional expense, that a tunnel was a viable alternative, and would have advantages over a bridge. After a decade of planning, holding hearings, and getting necessary approvals, construction commenced in 1980.


The Fort McHenry Tunnel was constructed using by using the Sunken Tube method. In a nutshell, what this means is that a large trench was dredged in the bottom of the harbor, and precast sections of the tunnel were sunken in place in the trench. Once sunk, the sections were joined and sealed, and the water pumped out. Once the water was pumped out, the roadbed and all of the mechanical systems were installed. Simple you think, until you consider that each tunnel section was 320 feet long and 82 feet wide, and had to be placed within inches of its target by sinking it into the cloudy turbulent water of Baltimore Harbor. A massive amount of spoil was created during the dredging process. This dredged material was not wasted, it was pumped ashore by slurry pipeline, and became 140 new acres of land near Canton. After the dredging was complete, this land became the new Seagirt Marine Terminal.

Construction Timeline:

May 7,1980: Contract to do the trench tunnel portion was awarded to a Joint Venture of Kiewit-Raymond-Tidewater, a joint venture of several companies, for $425 million. The work included moving a 42 inch water main that passed under the harbor, the manufacture of the 320 foot tunnel sections at Port Deposit, dredging, and laying the sections in place. Each of 32 sections was built and delivered to the construction site and placed about once every 3 to 4 weeks, and this work continued until 1983

November 1981: Contract for the 2,300 foot Western approach was awarded to Lane Construction for $64 million. The original estimate for this work was $126 million, but the recession made contractors hungry for work. In addition to the approach roadway, the contract also included relocation of railroad tracks near Locust Point, cut and cover concrete tunnel structures, and the west ventilation building, in addition to the roadbed.

June 1982: Contract for the Eastern Approach was awarded to S.J. Groves and Sons Company for $37 million, 26 percent under the estimated cost.

1983: Contracts for Mechanical Systems were let to Howard P. Foley Company of Baltimore. The centerpiece of this work was the ventilation systems. This composed of a total of 48 9 foot diameter fans capable of moving 6.7 million cubic feet of air per minute. The work also involved installing pumps to drain 44,000 gallons of water per minute from the tunnel. Other work included lighting, surveillance, and firefighting equipment.

1985: Tunnel opens November 23, 1985, nearly on time and $75 million dollars under budget.

1986: The Baltimore Harbor Tunnel Thruway gets a well-deserved rest, and work begins on a 2 year $40 million reconstruction project. Baltimore commuters and I-95 travellers rejoice!

2003: On a typical Friday afternoon, both the Fort McHenry Tunnel, as well as the Baltimore Harbor Tunnel Thruway are backed up for miles.

Tunnel Facts:

Location: I-95 crossing under Baltimor Harbor Western end descends near Locust Point, and emerges near Canton. Part of Interstate 95
Year Completed: 1985
Length: 8,800 feet of below sea level roadway
Lowest point of Roadbed: 115 feet below sea level
Number of Lanes: Eight
Number of Bores: Four
Superlatives: The largest sunken tube highway tunnel in the world. Another unique feature is that the roadway is curved, unlike most tunnels which use straight roadways underground or underwater.
Amount of Concrete used: 904,000 cubic yards
Amount of Structural Steel: 101,659,000 pounds
Reinforcement material: 42,000,000 pounds
Capacity of Ventilation Fans: 6.7 million cubic feet per minute
Amount of Dredged Material: 3.5 million cubic yards, creating nearly 140 acres of usable land.
Yearly Traffic Volume: 44,000,000 vehicles, or about 120,000 vehicles per day
Toll: Cars are $1.00, Trucks are $1.00 per axle. EZ Pass Commuter rates are available