Tunnels, Channel, Tunnel, Euro, Chunnel Construction, History, Water, Soft Ground, Rock, Mountain, Underwater, River, Artery, Railway, Railroad, Engineer, Explosives, Dynamite, Angle, Big, Dig, Archaeologists, Subterranean, Statistics, Civilizations

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Tunnel Construction
History of Tunnels

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Welcome compendium website on:

Tunnel Construction and the History of Tunnels.

Scan down to learn more about tunnels in this order:
Tunnel Basics
The Tunnel Challenge
Central Artery/Tunnel Project (Big Dig)
Channel Tunnel (Chunnel)

Chesapeake Bay Bridge-Tunnel

Holland Tunnel
Hoosac Tunnel
London Underground
New York Third Water Tunnel
Paw Paw Tunnel
Seikan Tunnel
Thames Tunnel
Underground Canal
Useful links to sites about tunnels
Mysterious Tunnels
Grand Canyon Mystery
Crumf Burial Cave
Secret Underground Tunnels
The Four Corners
Hardscrabble Mountain
Archaeologists Find Ancient Israel Tunnels
Brian Nelson's Blue Box Reference Directory

Important words found on this website: Tunnels, Channel, Tunnel, Euro, Chunnel Construction, History, Water, Soft Ground, Rock, Mountain, Underwater, River, Artery, Railway, Railroad, Engineer, Explosives, Dynamite, Angle, Big, Dig, Archaeologists, Subterranean, Statistics, Civilizations
Scan down to learn more about tunnels.

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Tunnel Basics
With more than six million kilometers of highways and 240,000 kilometers of railways snaking across the United States, life above ground has become increasingly congested. Tunnels provide some of the last available space for cars and trains, water and sewage, even power and communication lines. Today, it's safe to bore through mountains and burrow beneath oceans -- but it was not always this way. In fact, it took engineers thousands of years to perfect the art of digging tunnels.

Ancient Roman aqueduct

Before cars and trains, tunnels carried only water.
Roman engineers created the most extensive network of tunnels in the ancient world. They built sloping structures, called aqueducts, to carry water from mountain springs to cities and villages. They carved underground chambers and built elegant arch structures not only to carry fresh water into the city, but to carry wastewater out.

Worsley Underground
Canal Tunnel

By the 17th century, tunnels were being constructed for canals.
Without roads or railways to transport raw materials from the country to the city, watery highways became the best way to haul freight over great distances.

Holland Tunnel

With trains and cars came a tremendous expansion in tunnel construction.
During the 19th and 20th centuries, the development of railroad and motor vehicle transportation led to bigger, better, and longer tunnels.

Tunnel boring machine

Today, not even mountains and oceans stand in the way.
With the latest tunnel construction technology, engineers can bore through mountains, under rivers, and beneath bustling cities. Before carving a tunnel, engineers investigate ground conditions by analyzing soil and rock samples and drilling test holes.

There are three steps to a tunnel's success.
Today, engineers know that there are three basic steps to building a stable tunnel. The first step is excavation: engineers dig through the earth with a reliable tool or technique. The second step is support: engineers must support any unstable ground around them while they dig. The final step is lining: engineers add the final touches, like the roadway and lights, when the tunnel is structurally sound.

Based on the setting, tunnels can be divided into three major types:

Section of Brunel's
tunnel shield

Soft-ground tunnels...
are typically shallow and are often used as subways, water-supply systems, and sewers. Because the ground is soft, a support structure, called a tunnel shield, must be used at the head of the tunnel to prevent it from collapsing.

Check out the forces that act on soft-ground tunnels!

Hoosac Tunnel interior

Rock tunnels...
require little or no extra support during construction and are often used as railways or roadways through mountains. Years ago, engineers were forced to blast through mountains with dynamite. Today they rely on enormous rock-chewing contraptions called tunnel boring machines.

Check out the forces that act on rock tunnels!

Tunnel segment,
Boston Harbor

Underwater tunnels...
are particularly tricky to construct, as water must be held back while the tunnel is being built. Early engineers used pressurized excavation chambers to prevent water from gushing into tunnels. Today, prefabricated tunnel segments can be floated into position, sunk, and attached to other sections.

Check out the forces that act on underwater tunnels!

The Tunnel Challenge

Digging tunnels is hot, dirty, dangerous work. Since ancient times, tunnel diggers have used different types of tools to carve through mountains and bore through oozing mud.

Now it's your turn. Choose a location, pick a tunnel-digging technique, and see how long it takes you to dig a mile-long tunnel! Remember to excavate the ground with a reliable tool and to support any unstable ground around you while you dig!

Diggers often face unexpected challenges -- and disasters -- so enter at your own risk!


Through Mountain	Beneath City	Under River

Learn about the tools
and techniques of tunneling

Central Artery/Tunnel Project (Big Dig)


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Vital Statistics:
Location: Boston, Massachusetts, USA
Completion Date: 2004
Cost: more than $10 billion
Length: 18,480 feet (3.5 miles)
Purpose: Roadway
Setting: Soft ground
Materials: Steel, concrete
Engineer(s): Bechtel, Parsons Brinckerhoff, Quaide Douglas
Some call the Central Artery/Tunnel Project in Boston, Massachusetts, the "largest, most complex and technologically challenging highway project in American history." Others consider it one of the most expensive engineering projects of all time. Locals simply call it the "Big Dig." By the time it's finished in 2004, the tunnel will be eight lanes wide, 3.5 miles long, and completely buried beneath a major highway and dozens of glass-and-steel skyscrapers in Boston’s bustling financial district. What does it take to dig a tunnel like this? A lot of hard work and a handful of engineering tricks.


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Today, engineers use special excavating equipment, called "clamshell excavators," that work well in confined spaces like downtown Boston. These special machines carve narrow trenches -- about three feet wide and up to 120 feet deep -- down to bedrock. In Boston, engineers are pumping liquid slurry (clay mixed with water) into the trenches to keep the surrounding dirt from caving in. Huge reinforcing steel beams are lowered into the soupy trenches, and concrete is pumped into the mix. Concrete is heavier than slurry, so it displaces the clay-water mix. The side-by-side concrete-and-steel panels form the walls of the tunnel, which will allow workers to remove more than three miles of dirt beneath the city.

As if tunneling beneath a city isn’t hard enough, the soil beneath Boston is actually landfill -- it’s very loose and soggy. Engineers had to devise a few tricks to keep the soggy soil from collapsing. Their solution: freezing the soil! Engineers pump very cold saltwater through a web of pipes beneath the city streets. The cold pipes draw heat out of the soil little by little. Once frozen, the soil can be excavated without sinking. Engineers also inject glue, or grout, into pores in the ground to make the soil stronger and less spongy during tunnel construction.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Central Artery/Tunnel Project (Big Dig) 18,480' (3.5 miles)

Fast Facts:

The project will excavate a total of 15 million cubic yards of dirt, enough to fill Foxboro Stadium -- where the New England Patriots football and Revolution soccer teams play -- 15 times.
Reinforcing steel used in the project would make a one-inch steel bar long enough to wrap once around the Earth at the equator.
Moving all the dirt in the tunnel will take more than 541,000 truckloads. If all those trucks were lined up end to end, they'd stretch 4,612 miles. That's the same distance from Boston, Massachusetts, to Brasilia, the capital of Brazil.
The tunnel will emerge next to the FleetCenter, home of the Boston Bruins hockey team, and will cross the Charles River under the widest cable-stayed bridge in the world, the Charles River Bridge.

Channel Tunnel (Chunnel)


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Vital Statistics:
Location: Folkestone, England, and Sangatte, France
Completion Date: 1994
Cost: $21 billion
Length: 163,680 feet (31 miles)
Purpose: Railway
Setting: Underwater
Materials: Steel, concrete
Engineer(s): Transmanche Link Engineering Firm
When England and France decided to link their two countries with a 32-mile rail tunnel beneath the English Channel, engineers were faced with a huge challenge. Not only would they have to build one of the longest tunnels in the world; they would have to convince the public that passengers would be safe in a tunnel this size. Tunnel fires, like the Holland Tunnel disaster, were common at this time. How did the engineers resolve this problem? They built an escape route.


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The Channel Tunnel, also called the Euro Tunnel or Chunnel, actually consists of three tunnels. Two of the tubes are full sized and accommodate rail traffic. In between the two train tunnels is a smaller service tunnel that serves as an emergency escape route. There are also several "cross-over" passages that allow trains to switch from one track to another. Just one year after the Chunnel opened, this engineering design was put to the test. Thirty-one people were trapped in a fire that broke out in a train coming from France. The design worked. Everyone was able to escape through the service tunnel.

It took just three years for tunnel boring machines from France and England to chew through the chalky earth and meet hundreds of feet below the surface of the English Channel. Today, trains roar through the tunnel at speeds up to 100 miles per hour and it's possible to get from one end to the other in only 20 minutes!

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Channel Tunnel (Chunnel) 163,680' (31 miles)

Fast Facts:

At the time it was being built, the Chunnel was the most expensive construction project ever conceived. It took $21 billion to complete the tunnel. That's 700 times more expensive than the cost to build the Golden Gate Bridge!
Many of the tunnel boring machines used on the Chunnel were as long as two football fields and capable of boring 250 feet a day.
When construction began in 1988, British and French tunnel workers raced to reach the middle of the tunnel first. The British won.
In the first five years of operation, trains carried 28 million passengers and 12 million tons of freight through the tunnel.

Chesapeake Bay Bridge-Tunnel


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Vital Statistics:
Location: Cape Charles and Virginia Beach, Virginia, USA
Completion Date: 1964
Cost: $200 million
Length: 89,760 feet (total length); 5,280 feet (length of each tunnel)
Type: Beam, Tunnel
Purpose: Roadway
Materials: Steel, Concrete
Engineer(s): Sverdrup & Parcel

Distinguished as an "Outstanding Civil Engineering Achievement" by the American Society of Civil Engineers in 1965, the Chesapeake Bay Bridge-Tunnel is nothing short of a modern engineering wonder. Dipping over and under open waters with a complex chain of artificial islands, tunnels, and bridges, the Chesapeake Bay Bridge provides a direct link between Southeastern Virginia and the Delmarva (Delaware, Maryland, and Virginia) Peninsula. The bridge-tunnel complex is 17.6 miles long from shore to shore, and it cuts 95 miles from the journey between Virginia Beach and points north of Wilmington, Delaware.


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The majority of the bridge-tunnel complex is above the water, supported by more than 5,000 piers. But due to the importance of shipping in the bay, the crossing was sunk deep beneath the bay in two mile-long tunnels, to allow the passage of ships. Four artificial islands, each with approximately ten acres of surface, provide the portals by which the road enters the tunnels. It’s quite an eerie experience to be driving along and see the road you’re on disappear into the bay. Millions of cars have crossed the Chesapeake Bay Bridge-Tunnel since it opened in 1965. It’s possible that many just crossed it for the thrill of it!

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Chesapeake Bay Bridge-Tunnel 89,760' (total length); 5,280' (length of each tunnel)

Fast Facts:

There is a picture of the Chesapeake Bay Bridge-Tunnel on the cover of "The Way It Is," the first album by Bruce Hornsby and The Range.
Following its opening in 1964, the Bridge-Tunnel was selected "One of the Seven Engineering Wonders of the Modern World" in a worldwide competition that included more than 100 major projects.
Since it opened in 1965, more than 67 million vehicles have crossed the Chesapeake Bay Bridge-Tunnel.
One artificial island actually has a gift shop, restrooms, and a parking lot to allow drivers to stretch, relax, and enjoy the scenic view.

Holland Tunnel


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Vital Statistics:
Location: New York, New York, and Jersey City, New Jersey, USA
Completion Date: 1927
Cost: $48 million
Length: 8,558 feet (north tube), 8,371 feet (south tube)
Purpose: Roadway
Setting: Underwater
Materials: Steel, concrete
Engineer(s): Clifford Holland
By the early 1920's, ferries across the Hudson River, the only mode of travel between New York City and New Jersey, strained to handle more than 20,000 vehicles a day. Fed up with the traffic congestion to and from the city, New York City officials decided to build an automobile tunnel under the Hudson River -- one that would double the daily traffic load across the river. The biggest challenge was ventilation. Without some way of eliminating all the poisonous carbon monoxide from the automobiles in the tunnel, most drivers would pass out before reaching the other side!


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Engineer Clifford Holland came up with a brilliantly simple solution: big fans. Inside four massive ventilation buildings on both ends of the tunnel are 84 powerful electric fans that draw fresh air into the tunnel and blow dirty air out. Each fan is 80 feet in diameter. That's almost as tall as a 10-story building!

Unfortunately, fans this big can also be quite dangerous. In 1949, a chemical truck loaded with 80 drums of carbon disulfide exploded in the tunnel, injuring 69 people and causing $600,000 in damage to the structure. The ventilation buildings actually fanned the flames of the fire. As a result, strict standards were established in tunnels throughout the world for the transportation of chemicals and explosives.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Holland Tunnel 8,558' (north tube), 8,371' (south tube)

Fast Facts:

When the tunnel opened to traffic in 1927, the toll was 50 cents, the trip took eight minutes, and 51,694 vehicles passed through on opening day. Today, the toll is four dollars, the trip can take up to an hour, and more than 100,000 vehicles pass through the tunnel daily.
The Holland Tunnel was one of the first major uses of a compressed air chamber for tunnel stability.
Since it was built in 1927, more than one billion vehicles have used the Holland Tunnel.
The Holland Tunnel was given special status as a National Civil Engineering Landmark by the American Society of Civil Engineers in 1984.

Hoosac Tunnel


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Vital Statistics:
Location: North Adams, Massachusetts, USA
Completion Date: 1873
Cost: $21 million
Length: 25,081 feet (4.75 miles)
Purpose: Railway
Setting: Rock
Materials: Brick
Engineer(s): H. Haupt & Company, Thomas Doane, Walter Shanly
In March 1853, one of the earliest tunnel boring machines ground 10 feet into the Hoosac Mountain and died, never to run again. It remained stuck in its hole for many years as a grim symbol of engineering failure. In fact, it would take several failed attempts, 200 lives and 20 years to complete the Hoosac Tunnel.


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When construction began in 1851, workers relied on gunpowder to blast through the mountain. Progress was slow as each blast produced only a few feet of shattered rock. In 1866, two tunnel blasting tools -- nitroglycerin and the compressed air drill -- were used in the Hoosac for the first time. Workers blasted faster than ever before, but not without risk. Nitroglycerine is an extremely unstable explosive. Hundreds of workers lost their lives in unexpected explosions.

The Hoosac Tunnel remains a landmark in hard-rock tunneling. Over the course of its construction, virtually every kind of tunnel digging device was used to bore through the Hoosac Mountain -- and virtually every kind of mistake was made. Thanks to these mistakes, engineers today can build longer tunnels in a fraction of the time.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Hoosac Tunnel 25,081' (4.75 miles)

Fast Facts:

Two million tons of rock were carved out of the Berkshire Mountain range to build the Hoosac Tunnel.
Twenty million bricks were used to line the tunnel walls.
The Hoosac Tunnel project took so long to complete that critics nicknamed it "The Great Bore."
Many tunnel diggers claimed to have been haunted by the ghosts of two workers who died in an unexpected blast. Even today, there are many reports of ghostly activity in the Hoosac Tunnel.

London Underground


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Vital Statistics:
Location: London, England
Completion Date: 1863 (first line)
Length: 19,800 feet (3.75 miles)
Purpose: Subway
Setting: Soft ground
Materials: Cast iron, brick
Engineer(s): Sir John Fowler
Shortly after the opening of the Thames Tunnel, Parliament authorized construction of the first subway system in the world, the London Underground. Work began in 1860 on the first stretch of the underground subway, the Metropolitan Railway. By all accounts, it was a royal mess. Tunnel diggers used the cut and cover method: they carved huge trenches in the streets, lined the trenches with brick, covered the trenches with arch roofs, and then restored the street above. This sloppy method paralyzed traffic and made canyons out of city avenues, but it was a huge success. The new subway carried more than nine million people in its first year!


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Soon, Londoners were craving more, and they got it. This time, with the help of James Henry Greathead's tunnel shield, London engineers could tunnel under the city without completely destroying the streets above. Greathead's round iron shield supported the soft soil as it moved forward and carved a perfectly round hole hundreds of feet below London's bustling city streets. Inside the shield, tunnel workers laid cast-iron segments end to end. These segments eventually formed a stiff, waterproof tube, perfect for subways. Following London's lead, New York, Boston, Budapest, and Paris soon boasted subways of their own.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



London Underground 19,800' (3.75 miles)

Fast Facts:

The earliest lines on the London Underground follow the direction of major streets and rarely pass under buildings. This is because many Londoners feared that the tunnel would undermine the foundations of the city's buildings.
The trains in the London Underground were the first to be powered by electric engines.
During World Wars I and II, the London Underground subway stations were used as air-raid shelters.

New York Third Water Tunnel


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Vital Statistics:
Location: New York, New York, USA
Completion Date: 2020
Cost: $6 billion
Length: 316,800 feet (60 miles)
Purpose: Water supply
Setting: Rock
Materials: Concrete
Engineer(s): Grow, Perini & Skanska; Lehiavone & Shea
Six hundred feet below the busy streets of New York City, engineers are boring a 60-mile-long tunnel -- the largest tunnel in America. This tunnel won’t carry cars, trains, or even people, but it will deliver 1.3 billion gallons of water daily to nine million area residents. New York City’s $6 billion Third Water Tunnel is one of the nation’s largest and most complex public works projects ever attempted.


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In 1954, New York City recognized the need for a new tunnel to meet the growing demand on its 150-year-old water supply system. Construction began in 1970 on the Third Water Tunnel, a tunnel designed to improve the dependability of New York City’s entire water supply system. The majority of the tunnel is being carved with a 450-ton, 19-foot diameter rock-chewing device called a tunnel boring machine. Unlike the older water supply tunnels in New York City, water control valves in the Third Water Tunnel will be housed in large underground chambers, making them accessible for maintenance and repair.

When completed in 2020, the size and length of the Third Water Tunnel, its sophisticated valve chambers, and its depth of excavation will represent the latest in state-of-the-art tunnel technology.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



New York Third Water Tunnel 316,800' (60 miles)

Fast Facts:

The equipment used to dig the Third Water Tunnel is the same that was used to dig the underwater Channel Tunnel, or "Chunnel," that connects mainland France to England.
The largest valve chamber in the tunnel, the Van Cortlandt Park Valve Chamber, is 620 feet long (longer than two football fields placed end to end), 42.5 feet wide, and 41 feet high.
The tunnel boring machine, which had to be lowered into the tunnel in pieces and assembled at the bottom, is capable of excavating 50 feet of rock per day at a diameter of 23 feet -- more than twice the rate previously achieved in tunnel construction through drilling and blasting methods.

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Paw Paw Tunnel


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Vital Statistics:
Location: Paw Paw, West Virginia, USA
Completion Date: 1850
Cost: more than $600,000
Length: 3,118 feet
Purpose: Canal
Setting: Rock
Materials: Brick
Engineer(s): Lee Montgomery
Before there were highways, railways, and subways, there were canals. Engineers built hundreds of canals in the United States between 1790 and 1855, the Canal Age, because they were the cheapest and most reliable form of transportation at the time. Canal construction inspired some of America's first tunnels, long before the invention of drills and explosives. The Paw Paw Tunnel, on the Maryland-West Virginia border, remains one of the longest canal tunnels from this era.


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In 1836, Lee Montgomery, an engineer on the Chesapeake and Ohio Canal Project, estimated that construction of a 3,118-foot tunnel through the Paw Paw Ridge of the Allegheny Mountains would shorten the waterway by six miles. He also said it would take only two years to build. He was wrong. Armed only with dynamite, shovels, and picks, workers chiseled through the mountain at a painfully slow pace -- only 12 feet per week! Historic records of the ordeal are filled with stories of frequent cave-ins, bouts of unpaid wages, cholera, violence, and even murder!

Finally, in 1850, 14 years after he began, Montgomery broke through the other side of the mountain at the price of his own bankruptcy. Countless tons of coal, farm products, and manufactured goods were carried back and forth by mules and canal boats through the tunnel until 1924, when railways and highways became a more efficient mode of transportation.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Paw Paw Tunnel 3,118'

Fast Facts:

Workers removed 82,000 cubic yards of shale to build the tunnel.
The 24-foot-high tunnel is lined with six million bricks.
The tunnel took its name from the paw paw, an exotic fruit that grows on nearby ridges.
The completed tunnel was wide enough for only a single boat to pass through at a time. When a boat arrived at a tunnel entrance, a child would be sent to place a lantern at the other end to signal to oncoming boats that the tunnel was already occupied.
Today, the Paw Paw Tunnel is maintained by the National Park Service. The Chesapeake and Ohio Canal no longer runs through the tunnel, so it is possible to investigate the tunnel by foot or bicycle. Headlamps are recommended.

Seikan Tunnel


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Vital Statistics:
Location: Honshu and Hokkaido, Japan
Completion Date: 1988
Cost: $7 billion
Length: 174,240 feet (33 miles)
Purpose: Railway
Setting: Underwater
Materials: Steel, concrete
Engineer(s): Japan Railway Construction Corporation
In 1954, a typhoon sank five ferry boats in Japan's Tsugaru Strait and killed 1,430 people. In response to public outrage, the Japanese government searched for a safer way to cross the dangerous strait. With such unpredictable weather conditions, engineers agreed that a bridge would be too risky to build. A tunnel seemed a perfect solution. Ten years later, work began on what would be the longest and hardest underwater dig ever attempted.

Engineers couldn't use a tunnel boring machine to carve the Seikan Tunnel because the rock and soil beneath the Tsugaru Strait was random and unpredictable. Instead, tunnel workers painstakingly drilled and blasted 33 miles through a major earthquake zone to link the main Japanese island of Honshu with the northern island of Hokkaido. Today, the Seikan Tunnel is the longest railroad tunnel in the world at 33.4 miles in length, 14.3 miles of which lie under the Tsugaru Strait.

Three stories high and 800 feet below the sea, the main tunnel was designed to serve the Shinkansen, Japan's high-speed bullet train. Unfortunately, the cost of extending the Shinkansen service through the new tunnel proved to be too expensive. In fact, air travel today between Honshu and Hokkaido is quicker and almost as cheap as rail travel through the tunnel. Despite its limited use, the Seikan Tunnel remains one of the greatest engineering feats of the 20th century.

Here's how this tunnel stacks up against some of the longest tunnels in the world.
(total length, in feet)



Seikan Tunnel 174,240' (33 miles)

Fast Facts:

More than 2,800 tons of explosives were used in the construction of the tunnel.
One hundred sixty-eight thousand tons of steel was used in the construction of the tunnel. That's enough steel to build four Petronas Towers!
The railway track runs 787 feet below the surface of the sea, making it the deepest railway line in the world.
During construction in 1976, tunnel workers hit a patch of soft rock with disastrous results. Water gushed into the tunnel at a whopping rate of 80 tons per minute. It took more than two months to control the flood. Luckily, no lives were lost.

Thames Tunnel


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