Quick Note: How Much Tunnels Really Cost

New York is currently building a 3-kilometer tunnel between Brooklyn and Staten Island, using the same EPB method that Madrid uses to build subway tunnels. The cost of the single-bore tunnel is $250 million, and the project will be completed by 2014.

Of course, this is a water tunnel rather than a train tunnel. The diameter of the tunnel is somewhat smaller than that of a single-track train tunnel. Double-track tunnels, even ones built to high-speed rail standards, are substantially wider, but the amount of concrete lining required is proportional to radius rather than to cross-sectional area. For example, the double-track Seikan Tunnel is 9.7 meters wide, little more than single-track HSR tunnels in Europe, as Japanese construction tries to minimize tunnel clearances to cut costs and instead equip Shinkansen trains with elaborate aerodynamic noses. While 9.7 is more than 2.5 times the diameter of the water tunnel in question, 250 million times 2.5 is still far below the construction cost of any recent tunneling project in New York.

The expensive part of tunneling, then, is not the actual tunnel. It’s everything else, especially the station caverns. Both ARC and East Side Access included multilevel deep caverns in Manhattan with full-length mezzanines; of course they’d be more expensive.

For what it’s worth, an 8-kilometer long, 9.7-meter wide tunnel from Staten Island to Manhattan would cost $1.75 billion at the same per-km, per-meter cost of this water tunnel. Of course stations at St. George and especially Lower Manhattan would add much more, forcing a lot of difficult choices about location, but the basic infrastructure is not all that expensive.


      • Adirondacker12800

        Yes those evil people at the MTA didn’t want to share space with those evil people from the MTA so the MTA spent billions because the MTA wouldn’t let them something cheaper.

          • Alon Levy

            Judging by the resistance of both the LIRR and Metro-North to merge the two railroads, I don’t think it is.

          • Adirondacker12800

            For them to resist, someone, other than rabid foamers who think it would be a good idea, has to suggest they merge. And they are both divisions of the MTA. They both play nice with Amtrak and NJTransit. Why would it be a good idea?

          • Alon Levy

            Play nice? The LIRR clings to its own fiefdom at Penn Station, and would rather build the Harold Interlocking separation than use the southern tunnel pair and the middle tracks at rush hour. Metro-North restricts Amtrak to very slow speeds in order to simplify its dispatching.

          • Adirondacker12800

            Yes the LIRR tells Amtrak what it can do with Amtrak property….

          • Adirondacker12800

            Cuomo has been in office 15 months. Amtrak dusted off plans that had been filed away.

          • anonymouse

            I’m confused by how the LIRR moving to the south pair of tunnels will fix anything. Wouldn’t that just move the point of conflict from east of Penn to just west of it at A interlocking? The LIRR trains going to and from the West Side Yard would have to cut across the paths of Amtrak trains coming from the North River tunnels, as well as any NJT trains that would be going to Sunnyside, since they’d be displaced into the northern pair of East River Tunnels by the extra LIRR trains in the southern pair. This is even more of a conflict, because at least with the current layout at Harold, the only conflict is with the 1-2 tph of Amtrak service to Boston. I also have to wonder to what extent East Side Access will fix the problem as many LIRR trains get diverted via a grade-separated junction to the new line, leaving considerably fewer trains for Amtrak to conflict with. And any future Metro North service to Penn would actually use the facilities as intended, with trains from the Hell Gate Line ending up in the north pair of tunnels and possibly heading to the West Side Yard. So I guess what this means is that the Harold grade separation is probably just unnecessary entirely and the product of capital expenditures for their own sake, rather than some product of a turf war.

          • Adirondacker12800

            Whenever he says “south pair” I try to figure out what he means and I give up. On the Queens side the tunnels, going from north to south, in normal service, are
            On the Manhattan side they are
            There’s a flying junction underground in Long Island CIty. So the two tracks that are on the south side in Queens, in Manhattan, are between the tracks they were south of in Queens. Or the tracks on the south side in Manhattan, when they get to Queens are between the tracks they were south of in Manhattan.

            When East SIde Access was proposed it would have meant less trains to Penn Station. Today, to relieve overcrowding during rush hour there won’t be much of drop. The trains that now go to Brooklyn will instead go to Grand Central and Brooklyn will be served by a dedicated shuttle with it’s own separated platforms.

          • Alon Levy

            South pair is the the south pair on the underwater portion and the Manhattan side. In Queens it feeds into the southernmost westbound tracks and the southernmost eastbound tracks. Because the junction with the NEC is not grade-separated, avoiding conflicts means that NEC trains feed into the north pair, i.e. the higher-numbered tracks at Penn, and LIRR trains into both the north pair and the south pair, i.e. middle-numbered tracks. Current practice is for NEC trains to use the south pair.

          • Adirondacker12800

            Wouldn’t that just move the point of conflict from east of Penn to just west of it at A interlocking?

            Probably. And who knows where the trains to and from Grand Central are going to be.

          • Nathanael

            Adirondacker, the MTA under Walder’s administration (or was it the one before?) proposed the merger of “MTA Rail”, and LIRR and Metro-North resisted. Look it up.

          • Adirondacker12800

            It comes up every five years or so. The usual suspects make the same weak arguments on both sides, everybody else yawns and things remain as they are.

      • Stephen Smith

        Would they really not have had to build any caverns for East Side Access if the LIRR and Metro-North could work together, do through-running service, etc.?

        • Nathanael

          They would have had to build tunnels still, to get from 63rd St. to Grand Central Lower Level, and they would have had do some fancy renovations of the third rail contact system (“flip shoes”) — but they would not have had to build any caverns.

          • Alon Levy

            “Fancy renovations,” or just separate platforms. Grand Central doesn’t have a shortage of platforms.

          • Adirondacker12800

            The foamer froth is that the LIRR would take over the lower level. No need for fancy third rail shoes that switch from under running to top running or vice versa because the train would never go to the tracks that have the “other” kind of third rail.

            The cog railroad bits they would have to put under the LIRR cars would probably be more of a problem. The lower platforms on the F train are 100 feet below the street at 63rd and Lexington according to the information on nycsubway.org. The LIRR tunnel is under that. 140 feet below street level.

            Click to access CM009%20Handout_101807.pdf

            “Excavation of the Manhattan tunnels by
            the TBMs will be at a depth of about 140
            feet below street level entirely in Manhattan
            schist. The new tunnels will curve from 63rd
            Street and Second Avenue to Park Avenue around
            57th Street,”

            The interlocking north of the platforms in Grand Central Station extends all the way up to 57th street. Those skyscrapers that line Park Ave are over the tracks.

          • anonymouse

            But the platforms on the lower level of Grand Central are pretty far down too. The upper level is probably some 20 feet from the street, and the lower level is at least 30 feet below there, given that the platforms are below the level of the lower concourse. Going from 50 feet to 140 feet at a 2% grade would take 4500 feet, or about 17 Manhattan blocks, coincidentally just about the distance available from the end of the 63rd Street tunnel to 47th Street. The grade would help to slow down trains coming up from the tunnel as the approach the station, and conversely speed up departing trains as they leave the station.

          • Alon Levy

            The LIRR uses fairly high-performance EMUs. There’s no need to stick to a 2% ruling grade; those trains can do 3% or more if need be.

          • Adirondacker12800

            The bumper blocks are at 43rd street. 12 car trains need 1000 foot platforms So the end of the platform would be at 47th. Your arriving train would be moving across an interlocking, uphill. Or downhill as it left.

  1. modorney

    I seem to remember an early engineering study being done for the Chunnel that proposed drilling the three bores (and the middle one would have been full size) for a cost of only 1 Billion Pounds. But the single tunnel bore machine would have taken eight years to do all the tunnels. By using eleven borers, the tunnel was done quicker, but the boring cost eight times as much. Politically, the window of opportunity for the chunnel was small, and over a decade, it could have been killed.

  2. Alan Robinson

    A water tunnel is cheaper than a subway tunnel for several other reasons, especially over a long distance underwater. One needs an escape route, ventilation and drainage.

    • Alon Levy

      For a tunnel of a few kilometers, no escape route is needed (I think the cutoff is 6 miles, but I’m not sure). Ventilation is also not necessary for an electrified rail tunnel – electric trains do not generate point-source pollution.

      • Richard Mlynarik


        Plus end-point only evacuation of an urban rail tunnel (in which multiple crush-loaded trains may occupy simultaneously) isn’t going to fly anywhere, least of all the fire safety obsessed (by international standards) US.

        Note that there are operational restrictions to allow only a single train into some longer mainline tunnels in Germany.

        Check out, say, the Stockholm Citytunneln for the elaborate and extensive evacuation routes being constructed. (your Swedish search keyword of the day is “säkerhet”)

        The ventilation and supervision systems for any contemporary underground structure occupied by humans are extensive and are by no means cheap.

          • Andre Lot

            Well, I don’t know about FTA, but FHWA assess the “value” of a human life at around US$ 5 million when deciding which vehicular safety improvements can be mandated. But usually they just ignore it, as in – for instance – cameras of rear end of large cars, which is estimated to be on the US$ 22 million per extra life saved.

            At the end of the day, transportation or other infrastructure operated on a different league when it comes to assess the “feasibility” of new safety devices. Fatal train accidents (or air crashes, for that matter) are usually large carnage scenes with multiple people killed/maimed so there is just enormous public pressure to deal with it, even if providing vouchers for gyms would save 100x more lives… just different issues.

            As others pointed, another reason to have proper safety on tunnels is to avoid the tunnel itself being damaged.

          • Richard Mlynarik


            I don’t disagree with you that there are more cost-effective ways of improving overall human quality of life. (I’d start with education and contraception myself, and I’d start in sub-Sharan Africa, not Stockholm.)

            But the political reality is that hundreds of asphyxiated charred middle class (because that’s who benefits from expensive urban train tunnels) bodies being pulled from a hole in the ground just isn’t the done thing.

            Elaborate evacuation and safety systems are an unavoidable cost of doing business. (Which of course doesn’t mean the beyond-outrageous US Transit-Industrial Complex construction costs are justifiable in any way.)

          • Anon256

            Middle class train-riders seem about the same as middle-class health care patients, so I don’t see why taxpayers’ willingness (in e.g. the UK or Sweden) to spend on saving the life of the former should be so much greater than on the latter.

            (I agree that contraceptives and bednets for Sub-Saharan Africa obviously give the best value for money if we’re talking about what sort of charity is most worthwhile, but I can sort of understand why it’s politically infeasible to devote lots of tax revenues to that in the West. Anyway, at the public policy level, free immigration to the West would help people in Sub-Saharan Africa a lot more on average than feasible amounts of foreign aid, and would help people in the West too.)

          • Nathanael

            Anon256, it’s just a fact that people are willing to spend more money to prevent some types of death than others. Nobody seems to know why. One phenomenon is that people are willing to spend more to prevent deaths which are perceived as “out of their control” (so, stopping infectious diseases, genetic diseases, airplane crashes) than “in their control” (smoking-related diseases, car crashes)….

        • BBnet3000

          The BART transbay tube is 3 miles long or so and has no evacuation other than by the ends, doesnt it?

          • anonymouse

            It has an evacuation walkway down the middle, between and below the two train tunnels. It’s shown in the handy evacuation diagram in every BART car.

        • Adirondacker12800

          Even if the tunnel was shuttling freight on remote controlled trains you’d still want extensive fire detection and suppression, probably ventilation too – so the firefighters could fight the inevitable fire. A fire can take your very very expensive tunnel out of service for months.

        • EJ

          True, Europe didn’t used to be obsessed with fire safety in tunnels. How well did that work out for them?

          • Richard Mlynarik

            These things aren’t rational. Most of the world is surprised by US domestic electrical standards. Or the US gun murder rate. The inconceivably bad health care situation. Or US building energy efficiency standards. Or US obesity, which kills orders of magnitude more people than fires.

            If I had to make an uneducated guess, I’d say it’s a cultural-historical legacy of the Triangle Shirtwaist Factory fire, and the later Cocoanut Grove fire. Culturally, more the US pays more attention to fire safety and less attention to other, more effective, human quality of life issues. And there’s thing firefighting unions (AMERICAN HEROES AMERICAN HEROES 9/11) demanding and getting everything they ask for, even beyond the fire safety officials making demands that can’t be questioned and aren’t subject to comparative analysis.

            This is no different other nations over-spend in some culturally/historically specific ways. All that money frittered away on homeopathy isn’t doing anything for Germans’ life expectancy, you know.

          • EJ

            Maybe it was because the Europeans noticed that things kept on catching fire in their tunnels (Montblanc, St. Gotthard, Simplon, the Channel tunnel (twice so far)), they figured it was time to take it more seriously.

          • orulz

            Richard, this is completely off topic, but I’m interested in hearing more about comparisons between the NEC and international electrical standards. Do you have links to any documents, papers, articles, etc? I’m guessing based on context that the general consensus is that the NEC is comparatively primitive somehow?

          • Richard Mlynarik

            Orulz, off-topic: I mean “domestic” as in “house wiring”. US wiring and appliances and plugs and cords and outlets are flimsy (and half-voltage!) by some others’ standards.

            EJ: Nice to have a new pet troll. There is lots of heavily developed Alpine terrain in the version of the USA in your version of reality, I take it. The primary explanation for tunnel safety records anywhere in the first world is “good fortune”. And long may it continue, on both your planet and mine.

          • orulz

            I fully understand what you mean when you say “domestic”. When I say “NEC” I mean “National Electrical Code,” not “Northeast Corridor.” Is it just the perception that cords here on appliances are flimsy, when in fact it’s just that less shielding is needed at 110v than 220v? That to me seems like a matter of perception with no real substance behind it. Or is there some professional/academic consensus that the US National Electrical Code, which mostly applies to how things are wired within the walls, is somehow unsafe, lacking, or otherwise out-of-date?

          • Adirondacker12800

            North America standardized on NEMA 1-15 back in the 20s. You can plug your NEMA 1-15 plug into a NEMA 5-15 or 5-20 plug, It was designed that way.
            Up until recently in most of the rest of the world when you went out and bought an appliance it was a chance for the saleman to upsell a plug. Because the appliance didn’t have one. You and the salesman would look over the display of plugs they had and you’d pick the one that matched the outlets in your house. Which had a good chance of not matching the outlets in your neighbor’s house. Or any outlet in the next country over except maybe in hotels catering to people from your country.
            Special rules in the UK where they have this really bizarre arrangement called a ring circuit. It can carry 30 amps at 240 volts. The circuit you plug your reading lamp and radio or tv into. So in the UK the plugs have fuses in them to protect the wiring to things plugged into the outlets. Fuses that need to be replaced. So if all your appliances have plugs on them that were installed by a craftsman at the retail outlet you bought it at of course they look sturdy. They have to be big enough to be handled by a human with a screwdriver, not an injection molding machine. And in the UK big enough to hold a fuse.

            … the thermoplastic insulation on your stuff is probably good for at least 600 volts. Mechanical strength along with electrical insulation.

          • Adirondacker12800

            … NEMA 1-15 plug into a NEMA 5-15 or 5-20 outlet…..

          • anonymouse

            In particular, it’s all too possible and really all too easy to grab the plug in such a way that the prongs are still energized and also making contact with your fingers. I’ve inadvertently done that a few times myself while fumbling around trying to plug something in or out without looking. It’s rather an unpleasant surprise to get 110 volts across your fingers. Also, it’s rather an unpleasant surprise to discover that in normal operation, the power cord of your electric kettle gets quite warm, and a bit of a disappointment that kettles in the UK are twice as fast as they are in the US.

          • Nathanael

            Standards aren’t changeable easily, because of the phenomenon known as “installed base”. Compatibility has *inherent* value. Europe’s been able to modernize its electrical standards because, as Adirondacker said, they started with an incoherent mess of incompatible stuff — and in some cases it was ludicrously unsafe, such as the old Italian “standards”.

            The US standardized electrical stuff relatively early, and we haven’t had any potential improvements which are valuable enough to outweigh the value of compatibility. This is another case of “the US did it right 100 years ago, and now we’re falling behind”. Heck, we even managed to switch away from the Edison screw socket for everything but light bulbs back then — that was the original “standard interface” and don’t underestimate how hard it was to get people to switch away from it.

          • Adirondacker12800

            If he wants big clunky plugs he’s free to go down to electrical department at the hardware store or the big box stores and replace all of his plugs with big clunky things. There’s even ones that are reminiscent of BS1363 plugs.

            No one sells 2000 watt electric kettles like they do in the UK because 2000 watt electric kettles would need NEMA 5-20 plugs on them. Almost no one has NEMA 5-20 outlets. They wouldn’t sell.

            …and using an Edison screw base at the standard wasn’t all that hard to change. Same electrical departments that have the big clunky plugs have a selection of adapters that have NEMA 1-15 outlets that screw into and Edison base and vice versa.

          • Richard Mlynarik

            I don’t “want” anything changed. I have no opinion whatsoever on US household wiring codes. The original, entirely minor and throw-away illustrative point, is that different nations apply different amounts of regulation to different potential safety hazards. In Australia they think the electrons are going to jump out of the wall and bite you. In America they have above-ground fire hydrants. In Denmark they fret about trains running head-on into each other. etc. Phew.

  3. Tsuyoshi

    OK, so if the tunnel itself is not such a big deal, what’s the problem with just building a tunnel to connect the subway (the J, perhaps) to the Staten Island Railway? It would not require building any new stations.

    • Nathanael

      Political will.

      Plus, you can’t actually “just” build a tunnel; I believe the current location of the SIRT terminal doesn’t allow for direct extension into a tunnel, so you’d have to rebuild it.

      • jim

        The original plan was for the BMT 4th Ave line to connect to a tunnel to SI linking in to the SIRT somewhere between Stapleton and St. George. There are, apparently, stub tunnels off the BMT 4th Ave line (around 59th St. IIRC) built with that extension in mind.

        Even though tunnels aren’t as expensive as they used to be, a subway tunnel across the Narrows would still run on the order of a coupla billion dollars. There’s higher priorities that are cheaper: Triboro RX, for example.

  4. jim

    Material cost may increase with radius, but I doubt labour costs do. The muck to be cleared out will increase with cross-sectional area, for example. And the size of the TBM will increase probably by more than cross-sectional area (it probably gets longer as well) so manipulating it gets more than linearly harder.

    Still, the point holds. The cost of the tunnel isn’t what drives project costs so much as the cost of excavating ancillary structures (stations, switch caverns etc.). I believe the estimated cost of the ARC tunnels themselves was on the order of $2.5B.

    • Nathanael

      In fact, TBMs are cheap enough to run that they’re preferred over cut-and-cover for most projects these days, even those projects where cut-and-cover would not generate substantial disruption. TBMs are a fairly impressive engineering accomplishment.

  5. Andre Lot

    Something many people forget when evaluating tunneling costs is the cost of relocating utilities. Today, the “near underground” of many streets is a big maze of cables, pipes and ducts – situation far different than that of the beginning of 19th Century.

    So cut-and-cover in urban areas is, on that basis alone, very expensive because you can’t just say “hello, dweller, we’ll keep you without electricity/water/gas for a whole week while we dig stuff here”. We didn’t even go to the much lower acceptance of street-level disturbance.

    The actual digging of tunnels is not that expensive when the terrain above is favorable with TBMs. Just look at costs of very deep Alpine tunnels, for instance. Even dealing with complicated water tabled and geological faults, and all the safety systems a 10+ km tunnel 1000-2000m below ground entices their cost per km is dirty cheap.

    • Alon Levy

      Of course. I don’t disagree, or expect urban subways with stations to cost as little as other kinds of tunnels. That said, the big commuter tunnel projects in New York do not go to the near underground; because of what you say, they prefer to do things deep underground, and this means hugely expensive caverns under Penn Station and Grand Central.

      • Nathanael

        Y’know, I wish that most cities had the level of mapping of urban utilities that the best examples have; apparently everything built underground since the early Victorian era in the old “Metropolitan Board of Works” district has been pretty much accurately mapped in London. New York has such maps dating from roughly the Commissioners’ Plan, but not before (so Lower Manhattan is tough), the outer boroughs weren’t subject to the same mapping rules until they were annexed, and the process of digitizing the maps has been slow, and the maps turn out not to be entirely accurate.

        Many other cities are in far worse shape; places like Cleveland really have no idea what’s under their streets.

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