It’s Easy to Waste Money

As we’re finalizing edits on our New York and synthesis reports, I’m rereading about Second Avenue Subway. In context, I’m stricken by how easy it is to waste money – to turn what should be a $600 million project into a $6 billion one or what should be a $3 billion project into a $30 billion one. Fortunately, it is also not too hard to keep costs under control if everyone involved with the project is in on the program and interested in value engineering. Unfortunately, once promises are made that require a higher budget figure, getting back in line looks difficult, because one then needs to say “no” to a lot of people.

This combination – it’s easy to stay on track, it’s easy to fall aside, it’s hard to get back on track once one falls aside – also helps explain some standard results in the literature about costs. There’s much deeper academic literature about cost overruns than absolute costs; the best-known reference is the body of work of Bent Flyvbjerg about cost overruns (which in his view are not overruns but underestimations – i.e. the real cost was high all along and the planners just lied to get the approval), but the work of Bert van Wee and Chantal Cantarelli on early commitment as a cause of overruns is critical to this as well. In van Wee and Cantarelli, once an extravagant promise is made, such a 300 km/h top speed on Dutch high-speed rail, it’s hard to walk it back even if it turns out to be of limited value compared with its cost. But equally, there are examples of promises made that have no value at all, or sometimes even negative value to the system, and are retained because of their values to specific non-state actors, such as community advocacy, which are incorrectly treated as stakeholders rather than obstacles to be removed.

In our New York report, we include a flashy example of $20 million in waste on the project: the waste rock storage chamber. The issue is that tunnel-boring machines (TBMs) in principle work 24/7; in practice they constantly break down (40% uptime is considered good) and require additional maintenance, but this can’t be predicted in advance or turned into a regular cycle of overnight shutdowns, and therefore, work must be done around the clock either way. This means that the waste rock has to be hauled out around the clock. The agency made a decision to be a good neighbor and not truck out the muck overnight – but because the TBM had to keep operating overnight, the contractor was required to build an overnight storage chamber and haul it all away with a platoon of trucks in the morning rush hour. The extra cost of the chamber and of rush hour trucking was $20 million.

Another $11 million is surplus extraction at a single park, the Marx Brothers Playground. As is common for subway projects around the world, the New York MTA used neighborhood parks to stage station entrances where appropriate. Normally, this is free. However, the New York City Department of Parks and Recreation viewed this as a great opportunity to get other people’s money; the MTA had to pay NYC Parks $11 million to use one section of the playground, which the latter agency viewed as a great success in getting money. Neither agency viewed the process as contentious; it just cost money.

But both of these examples are eclipsed by the choice of construction method for the stations. Again in order to be a good neighbor, the MTA decided to mine two of the project’s three stations, instead of opening up Second Avenue to build cut-and-cover digs. Mined stations cost extra, according to people we’ve spoken to at a number of agencies; in New York, the best benchmark is that these two stations cost the same as cut-and-cover 96th Street, a nearly 50% longer dig.

Moreover, the stations were built oversize, for reasons that largely come from planner laziness. The operating side of the subway, New York City Transit, demanded extravagant back-of-the-house function spaces, with each team having its own rooms, rather than the shared rooms typical of older stations or of subway digs in more frugal countries. The spaces were then placed to the front and back of the platform, enlarging the digs; the more conventional place for such spaces is above the platform, where there is room between the deep construction level and the street. Finally, the larger of the two station, 72nd Street, also has crossovers on both sides, enlarging the dig even further; these crossovers were included based on older operating plans, but subsequent updates made them no longer useful, and yet they were not descoped. Each station cost around $700 million, which could have been shrunk by a factor of three, keeping everything else constant.

Why are they like this?

They do not care. If someone says, “Give me an extra,” they do not say, “no.” It’s so easy not to care when it’s a project whose value is so obvious to the public; even with all this cost, the cost per rider for Second Avenue Subway is pretty reasonable. But soon enough, norms emerge in which the appearance of neighborhood impact must always be avoided (but the mined digs still cause comparable disruption at the major streets), the stations must be very large (but passengers still don’t get any roomy spaces), etc. Projects that have less value lose cost-effectiveness, and yet there is no way within the agency to improve them.


  1. Joe Wong

    Alon – what does the MTA really stand for ??? Answer – Money Thrown Away of More Trouble Ahead !!! They really should rebuild the 38 Street Yards in Brooklyn to help ease the two existing yards at Coney Island, and Jamaica which are straining at overcapacity as well. That’s why trains are stored on the BMT’s 4th Avenue lines Express Tracks, as well as the IND’s Queens Blvd lines Express tracks as well.

  2. Eric2

    > They do not care. If someone says, “Give me an extra,” they do not say, “no.”

    This doesn’t follow. More likely they have in the back of their mind that no project is guaranteed to succeed (“succeed” in the sense of be completed without cancellation), and if they can add one more ally supporting the project at the cost of some money, that ally is more likely to help the project succeed than the extra money is likely to hurt.

    • Alon Levy

      This is likely what they have in their mind, and this is wrong. As a matter of legal realism, it’s not possible to sue the state. One can go through the motions but in practice the lawsuit will fail regardless of any technical consideration. NIMBY lawsuits fail whenever the state fights back (e.g. in California for HSR), and high-consensus projects like Second Avenue Subway are resilient to the loss of local political support.

      • Eric2

        “high-consensus projects like Second Avenue Subway are resilient to the loss of local political support”

        Everything looks more definite from the outside. Only when you’re on the inside do you see all the potential weaknesses in your project.

        • Alon Levy

          The insiders at no point said “this group was a veto point and the governor told us we must accommodate them.” In GLX, yes, there was an order from the Patrick administration to waste money in order to avoid antagonizing anyone who had met a city councillor or state legislator once, but not SAS, nor was there any significant call for cancellation after money was appropriated.

  3. Matthew Hutton

    I think you could solve it if a different political party took office in New York City. Then you could blame the wasteful democrats for the overspend and insist on better value for money going forward. I think that’s what Labour should do with HS2.

    The other issue in the UK and most likely in American is that the government is poor at dealing with the public. That HS2 had to build the pointless chilterns tunnel rather than funding the Aylesbury-Milton Keynes line and perhaps the Bourne End-High Wycombe line shows poor strategy. And worse too many in the rail industry don’t understand the need for win-wins with the public.

    Honestly not sure what the win-win for the second avenue subway is. Probably with that you just have to hold fire and say the project itself is the win – and that it needs to be cheap so you can build the whole thing.

    • Borners

      Everyone in the UK clearly just thinks ridiculously expensive costs are the price of doing business for railways in general. Advocates are convinced that its just because HMG doesn’t spend enough (which is stupid since we spend about as much as the Japanese do per year on capital projects) and any complaints are because somebody doesn’t believe enough (see Gareth Dennis).

      The problem is that Civil Service reform (i.e. stop moving people around the ministries and reward expertise) is not a rabble rousing issue with the public, the Tories are a nihilistic pensioner cult that seeks only to ruin everything and Labour is still pining for a Future that never happened (i.e. the British Industrial working class will bring about Socialist paradise on earth).

      Yeah the cannibalising the Aylesbury-East-West line is a very stupid idea that’s only possible because the toxic nexus of Treasury Brain and NIMBY Brain. The hilarious thing is that Buckinghamshire is the least populated corridor out of the Home counties so it should be easier.

      • Matthew Hutton

        When Labour wins here is a list of rail projects they will want to do:
        * West Midlands Metro.
        * Rail improvements between Liverpool and Hull
        * East West rail beyond Oxford-Milton Keynes
        * Crossrail 2
        * HS2 to Leeds and north of Manchester.

        If you can get costs down by a factor of 4 it might actually be possible to do all of them. With current costs – LOL!

        And yeah no swing voters are going to be excited by civil service reform, but neither are they going to be strongly against it either.

        Plus well educated politically aware people who have run teams are likely in favour – and they are the sorts of people who are councillors, and who run Labour’s campaigning on the ground.

        • Borners

          Oh no Labour has no ideological reason to not do it. Its more they are unlikely to think about it. If you read the Resolution Foundation website there is very little on state capacity and a ton on welfare. The latter plus human rights stuff is the bread and butter of Labour party rank and file. Outrider intellectuals aren’t especially interested either. And the only country they bother to learn from is the US which has just as many ideological blinders to this.

          And they totally want to build railways. The question is how to do you do it. And so far looking at the plans they are pretty mediocre. Building a brand new tunnel across the pennines before completing electrification of the existing lines and learning how to do timed overtakes properly? Rubbish just rubbish. What I would give to take those idiots to Kansai and bash their little brains into the Keihan or Hankyu lines. Organisation, Electronics before concrete etc. And then their ideas for leveraging housing to fund railways, right idea, totally moronic about how you do it.

          • Matthew Hutton

            Do you think the existing lines across the pennines could support 200km/h tilting trains without changing the track alignment too much?

            And what’s wrong with their approach to leveraging housing to fund railways?

          • Borners

            They need to learn how to do timed overtakes and learn how to use shoulder stations to get terminal capacity on the cheap. Seriously they are nowhere near capacity, they are incompetent whiners who need to be tied to the front of a JR West Special Rapid service from Tsuruga to Ako-Banshu so they learn how regional rail for a polycentric urban area separated by mountains is actually done, with top speeds of 130km because JR West has narrow guage problems. But the North of England makes New York look modest, its that level of dysfunctional series of policy cultures up there.

            Seriously a 200km high speed new build tunnel through the damned Pennies before the Picc-Vic tunnel? This is inane prioritisation. When Manchester has 4 million people like a proper city it can ask for it, but I suspect the good people of Wigan and Ashton would go full Fash rather than let enough undesirables to make their city something than a mediocrity

            Housing won’t work if costs are where they are now remember the taxes/infra levies from new development have to shoulder a lot of other costs (water, electricity etc). Or rather it won’t work outside of very very expensive areas. If costs can be brought down then pretty much everything south of Birmingham that hasn’t been electrified. In the North only Southern Lancashire/Cheshire, Central Manchester and the Leeds-York-Harrogate loop are really viable for this.

            Furthermore they are basing this on what TFL thinks happens in Hong Kong….which is not a useful standard for England. They need to learn from Japan (this is literally my masters dissertation). Which means operations cost control, Station-area land development tools and also developing in-house expertise at the County level on how to do this. You need make legible to the public that development is giving them something.

          • Matthew Hutton

            Also costs are getting to the point where projects are going to have a cost-benefit ratio below one.

            The politicians would be destroyed by the tabloids if they did that. So the choice is, do the low cost option or do nothing.

          • Borners

            They are not doing the “low cost” option. A 20km plus tunnel through the Pennines is not the “cheap option”. They don’t care, because Northern politics are all about bluster, patronage, spending other people’s money and finding new and creative ways to fuck up.

          • Matthew Hutton

            I think quite a bit of that is because the conservatives are in power. Once Labour win the press will start holding the government to account again.

          • Borners

            Media conspiracy theories are British left cope concepts, a lot of false consciousness escapism from the reality of human society being default small c-conservative*. The right wing press is 1. overrated its TV that’s no.1 followed by social media 2. Its power comes from its readership not the other way round (see Daily mail following a Murdoch style ideological strategy without a Murdoch and the long decline of the Daily Mirror are the tells). 3. New Labour was perfectly fine with spending money on incompetent project management with the best of intentions (see Overground). 4. British socialism/Labourism is fundamentally a romantic utopian sect that hates confronting details of governance or trade-offs. That’s a big reason why a program like rolling electrification has never happened, its too boring and incremental for a Holy Cause.

            * I’d also add my hobby horse that and making the English 2nd class citizens via West Lothian Question/Barnett Formula in the 1990’s was a really stupid way to make society better. But England is evil in Labour circles because if its not then Labour is evil for spending 100 years trying to abolish England (conversion therapy and deadnaming are bad).

    • Alon Levy

      It’s not impossible – they evidently did build it. It’s just not too useful for the cost, which involved some hilarious items like a tunnel under Holland farmland. The Netherlands has this really good intercity rail network, but HSL Zuid is peripheral to it, used mainly by expensive international trains to Belgium and France, which don’t have high average speed because of slowdowns in Belgium; the bulk of the Dutch network is a Swiss-style mesh of medium-speed lines with timed connections.

      • Matthew Hutton

        One of the reasons HS2 is expensive is because it’s being built to spec to take 400km/h trains. Even though you’d gain like 12 minutes at best over 200 miles (this is assuming non stop service and 7% padding).

        This means you land up with 900m bridges over a 5m wide river and stuff because to do anything else requires too much vertical curvature.

        • Alon Levy

          Yeah, that’s pretty silly, especially in a country the size of the UK. India, sure, I get building for a higher standard as in China, but Britain is smol. Even for international trains it’s silly – London is in the south of the country and not-London benefits more from having better transfers in London (and, FFS, from getting rid of the security theater) than from 5 fewer minutes of in-vehicle time.

          • Matthew Hutton

            Even for a country the size of China. One has to seriously question as to whether those ugly long Chinese viaducts would attract too much opposition from moderate older homeowners in a Western democracy.

            And then you’re back in mitigation hell.

          • Alon Levy

            The viaducts are common all over Asia, to reduce land requirements. In India they do the same, at very high cost, and so far the opposition doesn’t highlight the high costs of privatizing the state to the ADB and JICA but instead doubles down and complains about the few land takings that are there; Borners will be delighted to hear that even English-language papers, who represent the more educated opposition to Modi and Hindutva, are complaining about impact on farmers (which would be magnified if India built on earthworks as in Europe).

          • Borners

            Everybody in Indian politics plays the farmer card when it suits them and then forgets at the nearest opportunity. Yet they still haven’t figured out the route to agricultural reform is by allowing farmers to commercialise into diverse labour intensive gardening like in East Asia while keeping the crappy safety net as is.

            You’re not gonna hear defences of JICA from me. They are screwing up big time and it will blow up in their faces.

          • Richard Gadsden

            The only case for very high-speed is if you are expecting to be eventually joining a large number of other lines together.

            The day that the UK government took the HS2-HS1 link out of the plan is the day they should have descoped the speed to 300 or 320 km/h.

            Even if we could build for a reasonable coast, no passenger-dedicated, long-distance-dedicated high-speed line is going to go north of Scotland’s Central Belt; that makes the longest likely trips on a network that has been fully built out to be Glasgow or Edinburgh to London, both of which are about 400 miles/ 660 km. If we briefly pretend that this could be done non-stop at maximum speed, the difference between 300km/h and 400 km/h is ~33 minutes. In any realistic scenario where large fractions of the journey are at speeds below that (slowing for stations, accelerating out of stations, intermediate stops, infrastructure that can’t be built to 400 km/h, etc), it’s not going to be much more than 20 minutes difference in a three hour journey. That’s just not going to affect passenger numbers all that much.

            If there were going to be limited-stop high-speed trains from Glasgow to Italy or Spain, and every segment could be 400 km/h, then that would make a big difference (you’d be able to do a normal overnight sleeper rather than needing to leave at 6pm or arrive after lunch). But that sort of joined-up service is decades away at best and is always going to be a very small fraction of services compared to running normal city-to-city services every 20-30 minutes.

            The argument that is actually made is “we need it to be this fast because we’re going to Leeds the long way around and it has to be fast to get there enough ahead of the normal line to get passengers to switch”. But the reason they’re going to Leeds the long way around is because it’s too expensive to build a separate direct line to Leeds (and beyond to Newcastle) as well as one to Birmingham and Manchester. And that’s the case because they’ve overbuilt the line and can’t afford to have two lines into London.

          • adirondacker12800

            A very quick glance at the destinations served from Glasgow or Edinburgh’s airports, doesn’t have very many flights to Italy or Spain. Why would people who don’t want to fly there take a train?

          • adirondacker12800

            Or Amsterdam or Frankfort? Or maybe they are kayaking to Bilbao and hitchhiking to Madrid?

          • Alon Levy

            Priorities for speeding up travel from Britain north of London to Amsterdam:

            1. Getting rid of security theater and immigration controls
            2. Improving the connections in London
            3. Reducing fares to the norm for domestic trains and integrating them with British fares
            4. Building high-speed rail between Brussels and Antwerp
            5. Speeding up the trains through Brussels
            6. Speeding up the train on HSL Zuid

            666. Raising the top speed in Britain

            9001. Raising the top speed in Britain when the baseline is already 300 km/h

      • Matthew Hutton

        To be fair the Amsterdam-Brussels IC trains, and the Amsterdam-Rotterdam internal IC trains also use HSL Zuid. It’s not just Thalys/Eurostar.

        • Russell.FL

          Yes but those Amsterdam-Brussels IC trains currently top out at 160 kph, and will only top out at 200 kph once all the ICNG trains are on line in the next few years. I think going 300 kph saves the Thayls/Eurostar trains 6 minutes at best between Ams and Rott? Netherlands should have gone the Swiss route with their Mattstetten–Rothrist line and built HSL Zuid to 200 kph max, and used the remaining for other projects. HSL zuid is a vanity project which ultimately was not necessary in its present configuration.

  4. Spencer Dean

    One case that strikes me as a particularly bad case of preexisting commitment is with CalHSR’s Prop 1A speed commitments. It requires *average* speeds between San Jose and Los Angeles that are essentially as fast as anything, except they have to deal with huge mountains and tunnels at each end. A relaxation of this requirement so that they could do more like 110 Mph through the mountain passes and avoid a great deal of tunnelling seems to make a lot of sense.

    • Richard Mlynarik

      Again, I was there then.

      I saw how this went down, in detail.

      This was and is all about cost maximization. Nothing else.

      Parsons Brinckerhof, the private contractor that fully and completely controlled the “public” CHSRA agency, wrote those “commitments” to ensure that only the worst and most expensive route was chosen, with maximum interfactions with existing highway and railroad corridors, and the very worst and most expensive and inutile and decades-late (Pacheco, Palmdale) primary CBD approaches, and then iced the cake with end-to-end run time requirements that transformed the truly awful route requirements into absolute madness levels of concrete.

      CHSRA — which is now and then simply a zombie husk host body providing sweet sweet nutrients for the private consultant parasites — complaining about being “forced” to do terrible stupid wasteful things because of some “preexisting commitment” that was imposed upon it is entirely backwards. This is Br’er Rabbit lamenting about having been thrown into the briar patch.

  5. adirondacker12800

    Neither agency viewed the process as contentious; it just cost money.

    It’s perfectly reasonable for the Parks Department to ask who is going to replant the grass if it’s going to get chewed up. And whose budget that is going to be on. If nobody does that, within a few years the muddy rutted plot grows a thicket of trees that become impassable a few years later.

      • adirondacker12800

        If I want someone to scrape the weeds off what passes for my lawn and replace it with sod, I don’t have to file paperwork and neither does the contractor. Or put out requests for proposals, have community and stakeholder meeting, defend lawsuits, entertain multiple bids and publish them… ad infinitum. They probably wanted a few trees too and large ones aren’t cheap. Or putting that out to bid etc.

        • Matthew Hutton

          Big plants really aren’t that expensive either. They might cost a few hundred dollars rather than ten dollars, but they aren’t earth shatteringly expensive either.

          Honestly the best plan is probably to just get the old women from the neighbourhood to sort it out, give them expenses for the plants they buy within reason, give them access to some water – and tell them they’ve got to look after the them.

          • adirondacker12800

            They cost tens of thousands of dollars installed and that doesn’t include the cost to have community stakeholder meetings where they decide they want maples instead of oaks.

          • Henry Miller

            While everyone wants big trees, small trees that mature into large trees over time are the way to go. You have to break too may roots of big trees to make them viable. As such small cheap trees are the way to go. If you want big trees, then plant a mix of fast growing trees (a big tree in 4 years, but will die in 100 years) and slow growing ones (100 years to be a nice tree). You want the variety of trees anyway for diversity reasons.

    • Alon Levy

      Yeah, this is not how the Parks Department was thinking about this at all. It was not about restoration costs; they explicitly told us they were trying to maximize outside funding.

      • adirondacker12800

        I’m sure they dug out the unfunded plans for rehabbing the run down park. It would be stupid to tear out run down stuff and replace it with worn out stuff. It shifted the rehab plans from 2025 to much earlier.
        It came out of the taxpayer’s pocket labeled “MTA” and went into the taxpayer’s pocket labeled “Parks Department”. And all sorts consultants all over rejoiced because there would be lots of paperwork.

          • adirondacker12800

            And what did comparable rehabs in the same time cost? I’m sure they did more than one during that period. There’s a really nice, new, quarter billion dollar one at 14th and West Streets.

          • adirondacker12800

            This gets better. It’s not a park. The Board of Education graciously allows the Park Department to treat it like a park. Which is causing great amounts of consternation and lawsuits. Unrelated to the MTA.

  6. Tom M

    Probably a noob question, but what are the back of house functions they’re placing in the stations. Would it not be cheaper just to place them in a normal building above ground than expensive station space?

      • Matthew Hutton

        I bet the reason they need so many break rooms is because the state won’t pay for Nespresso machine, a dishwasher, some nice $1500 sofas (like an IKEA VIMLE) and a cleaner for their staff in the communal break rooms.

        So you land up in a bizarre world where it’s easier to spend $100m on a new break room than $10k a year per break room maintaining it and keeping it nice and comfy with a decent selection of drinks.

        • Alon Levy

          At least from what we’ve heard, the complaint isn’t “the existing break rooms are poorly-maintained,” but “we want our own space separate from the other departments.”

          • Matthew Hutton

            I think the question to go back to them is *why* do they want space separate from other departments?

            Because to me standard public sector tightness on perks sounds makes having separate department-by-department break rooms much more appealing than they’d otherwise be.

      • adirondacker12800

        If you dig a hole it’s cheaper to fill it with air than it is to haul dirt back in. Air is a lot lighter than dirt and the structure can be a bit less brawny.

  7. Tunnelvision

    Regarding your comments on why TBM’s operate 24/7 but muck was removed only during the day.

    First of all there’s these things called Noise Ordinances that restrict noise between certain times of day. Secondly I’m pretty sure that the Environmental Impact Statement for 2nd Ave probably indicated that noise, dust etc. would be controlled so as not to disturb the neighbors. Operating a mucking system 24hrs a day without the noise/dust enclosures would keep everyone near it awake all night. Even if you use rubber lined dump trucks, which exist, the noise far exceeds the allowable noise between 10pm and 6 am. Oh and this is not unique to New York, night time trucking of rock and muck from projects is limited almost anywhere that the project sponsors give a crap about the neighbors, back in the 1990’s we built noise barriers with storage muck bins for a wastewater tunnel project in Hong Kong for the exact same reason. So before you trash New York, this is pretty common practice wherever you are. For soft ground tunnels its a little easier as the muck handling is a lot quieter but local ordinances still have to be followed with regard to truck movements…. wherever possible you try to locate the main drive site away from residential areas but that’s not always possible…

    Modern TBM’s do not break down all the time, most of them have availability rates over 90%, which is generally measured as when a TBM is available for use. In fact most contracts between the TBM manufacturer and the Contractor have target availabilities with penalties should these not be met. Then there is TBM Utilization which is the % of time the TBM is actually excavating and depending on how its defined, installing the permanent lining in the case of segments and potentially the temporary rock support in a rock tunnel. Utilization can vary between 35 to 65% depending on a multitude of factors of which unplanned downtime (breakdowns) is generally not a major element. Because tunneling is a cyclical activity there are various activities that have to happen at some point in the cycle that contribute to lowering the utilization for example: extending the temporary rail system, extending the compressed air/construction water and pump discharge lines for which the various systems have to switched off, lines broken, new length of line installed and systems repressurized and yes flexible lines are used where possible but they still have to be extended at some point. THe 12kV feed has tpo be extended on occasion and the ventilation ducting cassette has to be changed. That’s the basic stuff. For a hard rock TBM you will need to inspect the cutterhead tools every couple of strokes, meaning a miner has to go into the cutterhead and perform the inspection, not very time consuming although there’s a risk of burns from the discs as they get rather hot, then if needed discs have to be changed once the wear exceeds the permissible. A disc cutter weighs around 300lbs and despite significant advances in handling systems still requires human muscle to effect this. And yes you can plan the frequency but there’s no telling exactly how the cutters will wear in the ground until you are mining. Add in probe drilling and possibly advance ground treatment to cut off ground water there are many activities that can detract from the advance of the TBM, none of which are breakdowns.

    Similarly for soft ground TBM’s. One major difference here is cutter tool changes which require face stabilization measures to enable access to the cutterhead and are less frequent than on hard rock TBM’s but can stop the TBM for days while you get into the cutterhead under say compressed air which then restricts your efficiency.

    Modern TBM’s have an array of sensors that monitor everything from the amount of metal debris in the hydraulic systems to cutter tool wear and their PLC and control systems are designed to minimize breakdowns as the manufacturer is often on the hook for their performance.

    You can get TBM’s that can speed advance rates significantly, these are double shield TBM’s. On the Channel Tunnel the UK side used such TBM’s and achieved 3-400m a week as you can excavate and build segments at the same time with such a TBM. But the chalk marl was perfect tunneling rock, no water and expanded segments were used which could be built and installed without the need to grout them in place. But these are more complicated machines and not often used especially in soft ground as the articulation joint can be problematic between the shield sections.

    Anyway, the choice to use noise enclosures for the TBM’s has little to do with their operation capabilities and more to do with complying with local ordinances.

    • Alon Levy

      Hong Kong practice is not persuasive authority given its very high costs. Ditto Singapore, Canada, or the UK. You want to tell me that they do this in Italy, go talk to Marco about it. (Sweden doesn’t use TBMs, so it can actually shut down trucking muck overnight.)

      Modern TBM’s do not break down all the time, most of them have availability rates over 90%, which is generally measured as when a TBM is available for use. In fact most contracts between the TBM manufacturer and the Contractor have target availabilities with penalties should these not be met. Then there is TBM Utilization which is the % of time the TBM is actually excavating and depending on how its defined, installing the permanent lining in the case of segments and potentially the temporary rock support in a rock tunnel. Utilization can vary between 35 to 65% depending on a multitude of factors of which unplanned downtime (breakdowns) is generally not a major element.

      So, the tunneling engineers we’ve spoken to in a lot of different countries treat 65% as unachievable and 35% as average to high end. This includes New York – New York isn’t somehow unusually efficient.

      • Tunnelvision

        Who said Hong Kong is persuasive, it was simply an example. My point is that there are noise ordinances in most countries and cities that have to be complied with. If the Italians run trucks all night and annoy any local residents good for them. As for Stockholm I’m assuming they have some form of noise ordinance which prohibits blasting overnight? Also if you look at the math, its more efficient to run the trucks during the day only, if its organized properly they can easily get rid of the muck produced on night shift. Your also then not paying the night shift premium in Unionized areas for the truck drivers. The other thing to consider is whether the disposal location is open at night, I mean if you can’t dump the muck somewhere what’s the point moving it??? Minimizing the number of times muck is handled is a cost driver. Now on East Side Access no noise control measures were needed for muck disposal, but that’s because there were 9 miles of conveyor belt from Manhattan to Queens, and a vertical belt took the muck out of the bellmouth, across Northern Boulevard and then the muck was stockpiled in Queens in Sunnyside rail yard and then moved on day shift. At the end of the day the muck quantity and the number of trucks remains the same whether its moved on day or night shift, so I’m not sure how you work out there was additional cost for only trucking during day shift. The noise control measures would have likely been needed anyway on 2nd Ave to allow 24 hr. operation, vent fans are extremely noisy for example. They may have been smaller but stockpile facilities would still be needed to provide a buffer between TBM production and muck disposal. Interestingly when 2nd Ave and ESA were in planning we ran a feasibility study to see if the 2nd Ave muck could be disposed of through the ESA belt system in the 63rd St tunnel. The conclusion was that it was practically feasible, but would have required complete reconfiguration of the existing vent shaft at 63rd St/2nd Ave but was cost and schedule prohibitive.

        Rock is harder to manage than soft ground so it very much depends on where your drive and mucking shaft is and your chosen methods of spoil removal. If you can use a vertical belt in the shaft and then transfer to a spoil stockpile then that’s the ideal, but you still need a stockpile and that stockpile needs managing, it will need watering down to avoid dust blowing everywhere for example, so drains, sumps and pump’s are also required. Planning the logistics is critical no matter where you are. Being able to get the TBM to the site and get the muck away are the two critical components you normally have to consider alongside power availability and water discharge. On a project in Atlanta the TBM’s were delivered to the port of Savannah and then trucked 75 mile to the project site, Georgia DOT had to inspect the various bridges and culverts along the route and the Contractor had to shore a couple of structures even though a multi axle vehicle was used. Took three days to deliver the main drive units to the project site. These things add cost. Now those were hard rock TBM’s and the main drive units weighed if I recall correctly around 120 tons.

        As for TBM utilization 35% utilization should be easily achievable these days and 65% while being high end is achievable with the right TBM in the right ground, how do you think the Channel Tunnel TBM’s achieved 430m a week back in the 1980’s. But it depends how you measure it. For soft ground TBM’s if you consider the critical path activities are excavation and ring erection, then the % should be higher, it its just excavation then the utilization drops. I mean the math is quite easy. Assuming a 1.2m stroke/ring width on a typical metro tunnel of say 7m diameter the stroke time will likely be in the order of 30 minutes, ring build will be dependent on the number of erector tables and how automated it is but in any case the hydraulics govern, so lets say 30 to 45 minutes to retract rams, builds, engage rams and be ready for the next stroke. Best case 1 hr for a complete cycle, more likely 90 minutes. In an 8 hr. shift using the 90 minute number that’s 5 cycles or 6m per shift say 18m per day on average with 3 shifts, which a lot of projects achieve on a routine basis. Assuming excavation and ring build are included in utilization then planned best case utilization would be 62% in this example. Either way breakdowns tend to be less commonplace and have less impact and its the logistics that govern, as tunnels get longer it takes more time to deliver segments to the TBM which then becomes the limiting factor especially if your using rail transport for muck and segments. Having said that I was on a project where the drive shaft on a 12ft diameter Atlas Copco Jarva TBM shattered over a mile into a 3 mile drive. That took 157 days to dismantle the TBM, remove the drive shaft, find, mill and deliver the replacement drive shaft from another mothballed TBM, install it and rebuild the TBM, through a 450ft deep shaft and a mile and a bit under a harbor……so when they do go wrong!!!

        • Alon Levy

          You’re not paying the night shift premium to the truck drivers, but you are paying the morning congestion premium. And the contractor told us the morning trucking was imposed by noise regulations and not by the availability of the disposal site.

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