14 ms·

Why we stopped building cut and cover

190 points by jseliger 3y ago

mc32 3y ago
As far as I understand it, and this may be outdated, cut and cover is way cheaper than boring. And you only bored tunnels if you had no other choice --like Big Bertha in Seattle. BaRT was mostly cut and cover as obviated by going under Market and Mission streets. Maybe new boring machines are faster and cheaper and break down less than before.
- gumby 3y ago
  Yes, cut and cover is cheaper to execute than using a boring machine in most cases and when possible. But the externalities of cut and cover can be very expensive (blocks streets, and hurts nearby businessen even to the point of going out of business). Those second order effects, even if transient on a long term scale, can cause expensive hold ups. Other externalities are the need to get around existing infrastructure, some of which could have over a century of continuous use. So for example in NY it is almost impossible (look at the 2nd ave subway, which is mostly pretty shallow) while in LA cut and cover was no problem at all.
  - BobaFloutist 3y ago
    I wonder if the price difference between boring and cut and cover is greater than the cost to just...cover business's expenses (rent, loan interest, payroll) for the time it takes to get cut and cover done on that block. Could we just pay them off?
    - actionfromafar 3y ago
      That sounds like it could be cost effective if one only includes the individual businesses and cover their losses, but it can still cause second order effect harm, like customers changing habits and not returning to the original place. Something to think about. Suboptimal infrastructure is also costly, of course...
      - BobaFloutist 3y ago
        Honestly I'd be fine with it if the public agencies just used it as a justification for a eminent-domain style "We're going to do this project this way in the interest of the public, we're giving you some cash to cover your immediate costs, and that's that."
      - immibis 3y ago
        The justification for business owners making profits is that it's payment for taking risks. Why then are we trying to shield them from risks while still allowing them to make profits?
        bluGill 3y ago
        Because we want business to take those risks. In the end I benefit from those businesses - not all of them, but some of them. Businesses should take risks. However government should not add extra risk without careful consideration.
        samatman 3y ago
        Business owners making profit needs no justification, that's entirely backward. Anywhere there are people, there are goods for sale. The ones who need to justify themselves are the ones who propose to restrict this. It can be done, I consider the restrictions on the nuclear weapons and slave markets eminently justifiable. But in a free society, the default is freedom.
    - gumby 3y ago
      For private sector projects people do get bought off (in a non-corrupt sense of that phrase) but that seems to be unacceptable for public projects for some reason. I'm talking about the US here -- no idea elsewhere.
      - BobaFloutist 3y ago
        I assume the second private was supposed to be public?
        gumby 3y ago
        Yes, thanks. I was still in the edit window so I fixed it.
  - hinkley 3y ago
    I wonder how many different ways people have tried cut and cover over the years. I'm talking here of the horizontal part of the project, not the vertical. It seems like you usually have one, or maybe two, moving work sites, and they go block by block removing the street, and replacing it behind them at some point. Any business near the sites is choked off from foot traffic for a while, even if the site isn't in front of their door yet. Is it more or less disruptive if you do a checkerboard pattern instead? Instead of n months of construction around your favorite coffee shop, would it be better to have n/2 months of construction now, and n/2 months of construction in July? Maybe that depends on where you are on the street. If, for instance, you start at both ends, then the businesses in the middle of the cut have construction sites boxing them in for almost twice as long as anyone else does. Or maybe that just means more people of means mad at elected officials.
    - bluGill 3y ago
      The problem is the street overall is blocked off for the duration. Sure it looks like only one block is stopped, but in reality people who have to travel that block are backed up all the way, and so they will look for alternate routes for the duration. If you could build the entire thing in 2 weeks (per year) people would be happy with a full road closure - they would all take vacation for those two weeks. This is for the entire city - close all roads to non-emergency traffic for two weeks, fix them all up - everyone not involved in road work or essential services would just go on vacation. You cannot do this of course, but that is what people really want.
      - hinkley 3y ago
        I thought about that too. The problem with trains is that they always need to run in the primary direction of traffic. So you can't really build them on cross-streets and avoid disrupting the main thoroughfares. Otherwise you'd often end up with a train to nowhere. The main exception being when traffic is curved, going around some obstruction that the train can cut across. I recall when South Lake Union got its trolley, one of the things they pointed out was that property values next to a trolley drop, but property values 1 block away go up more. Everyone wants to be a couple blocks from transit, not living above it. So even if you avoided the main road going parallel to it, you're probably tearing up even more desirable real estate and commercial zoning.
  - asdff 3y ago
    What people often forget about modern cut and cover is that it is only disruptive for a short period of the project because they can put a temporary road deck over the cut and do most disruptive work overnight. Its how LA metro built a subway station in the middle of Beverly Hills.
    - bluGill 3y ago
      There are several options to make cut and cover less disruptive. Other options are dig in the sidewall supports, then build the cover over the current road surface, finally dig out underneath. It is still tunneling, but it uses most of what makes cut and cover cheaper than a TBM.
- kdmccormick 3y ago
  Did you read? Article states that cut and cover is still much cheaper technically, but can end up being practically more expensive due to the political/legal ramifications of the surface disruption.
  - mc32 3y ago
    Depends, Gaoxiong did a C&C and they were able to mostly mitigate the second order effects of C&C. Yes, in some sections some traffic was affected more, but apparently it wasn't widely disruptive. It can be done. It helps when you can complete the project in a few years and not take a decade to build out a single line. So politics does have an impact on feasibility and practicality of C&C.
- masklinn 3y ago
  > As far as I understand it, and this may be outdated cut and cover is way cheaper than boring. When you ignore all the side effects, sure (especially if you also ignore the risks of blowing the timeline). Trenchless tech is spreading fast even in small-ish (street utility scale) construction. > Maybe new boring machines are faster and cheaper than they used to be. I'm not sure that's even the case, AFAIK TBMs are still custom-built for the job, highly geology-dependent, and require a ton of babysitting. If you hit an unexpected patch of really different geology things can get really dicey.
  - bluGill 3y ago
    > TBMs are still custom-built for the job This is semi-true. They are built for the job, but the design is standard. What is custom is the exact size of the tunnel, and thus all the supports. TBMs generally last a lot longer than the job, so a city could save a lot of money if they planed to keep using their TBM, constantly digging tunnels. Start with a north-south line, then use the same TBM to build an east-west line (or southeast/northwest), and so on. However most cities are unable to find the continuous budget to do that and so when they are ready for the next one the old TBM is no longer worth using, and in any case they no longer have trained crew to run it. > highly geology-dependent, Soft water logged earth needs different machines from hard rock. There are combination machines, but if you can determine which you need you save a lot of money ordering the geology specific machine. Get this wrong and you end up with a TBM and partial tunnel under the city. > require a ton of babysitting. 12 people per shift is the number I've heard (NYC uses double which is one of the smaller reasons things cost so much there). The work is mostly routine though. However the TBMs do break once in a while and they everything stops while you repair them.
- matthewmacleod 3y ago
  The article discusses this extensively.
- hinkley 3y ago
  There's the construction cost, and there's lost income from the people who voted for you. Not all of the money spent on construction is tax dollars. Think about every time you've been stuck in traffic because there are 3 roads that get you from A to B, and some jackass at city hall thought it would be a good idea to permit road work on 2 of them on the same day. We are used to highway on-ramps being replaced in days to weeks, but removing an entire street, digging up everything under it, being careful not to nick the utility lines and pipes, then packing dirt back in around them without tearing them, then rebuilding the street on top, that's a lot. Especially for the businesses on that road. We end up with transportation solutions that are suboptimal because we don't have the political will to tear off the bandaid. This on-ramp is in the wrong place because the old one was in the right place, but was built in a terrible way and had to be removed for safety while still handling daily commutes.
epistasis 3y ago
I'm very grateful for those posting and upvoting interesting construction articles on HN, this is a key area of our economy that is stagnant and could really use some improvement. Traditional media do a terrible job of coverage, and spreading articles like this helps get better mainstream coverage. A lot of the bad things about construction come down to incumbent players being able to force extremely costly methods on anybody who wants to improve the world. So a lot of the challenge is political. Solving political problems is really hard, but when technology can sidestep the problem, there's a lot that becomes possible. For those in the Bay Area, we are seeing aversion to cut and cover be a huge hassle for our stations. The depth of some of the new transit stations will be a huge inconvenience for generations of transit users, all to satisfy a short term disruption of a far smaller number of people. This problem could have been solved with money, for those affected, if it were not for the politics.
- theluketaylor 3y ago
  Deep stations are also unbelievably expensive. Deep tunnels are not that bad, but the resulting stations explode the budget for transit to the point getting the project green lit in the first place is nearly impossible. Plus with the same set of dollars you are building a lot less transit.
  - hinkley 3y ago
    The deepest station in Seattle has smelled like someone tried to make cheese from moldy gym socks since the day it opened. I believe it opened and immediately shut again so they could try to deal with the water problem [though responder says no]. I went through when it was briefly open and again after. They made it less bad, but it was still pretty awful. A club I belonged to met at a library near the station so it was easiest for me to just hop on the light rail after work and then take it back to the bus terminal after but gods did I want to hold my breath the entire time.
    - oasisbob 3y ago
      > The deepest station in Seattle has smelled like someone tried to make cheese from moldy gym socks since the day it opened. Maybe it's just a matter of opinion, but I never found the Beacon Hill light rail station to smell like anything other than raw concrete, similar to DC metro or any other deep tunnel system. I lived in the neighborhood at the time, and don't remember the station shutting down due to water ingress. Opening was delayed due to issues with overexcavation, but that threat was with sinkholes opening to the public above, not issues with the tunnel itself.
yawnxyz 3y ago
If you're ever in Sydney, go to the St. James station (I think) and you'll see lots of historical photos of using horse and carriage to build the first Sydney metro stations. Very very cool!
- hinkley 3y ago
  I hear there's a museum in Tokyo as well. When I was there in the 90's they were excavating a station that was found by a construction crew. The plan was to turn it into a subway history museum. I was told that the line was abandoned after an earthquake, and they lost track of the location of some of the stations (or at least, this one). It was on a green strip of undeveloped land, so I have a small suspicion that a landslide may have been involved. I mean how else do you 'lose' a building?
  - bobthepanda 3y ago
    It is highly doubtful that anyone in bubble-era Japan “lost” a piece of property. The rail companies in particular are keen, savvy property developers. During the bubble, the Imperial Palace grounds had a higher real estate valuation than all of California.
    - hinkley 3y ago
      I feel like you might be underestimating the age of subway lines. 2027 will be the centennial anniversary of the Ginza Line, and that's a baby compared to Paddington Station, which had its sesquicentennial a decade ago. Apparently the Tokyo postal service had a private line in 1915. I kinda wonder if that's the one they 'found'.
tareqak 3y ago
I think we should find ways to get ahead of the disruption that construction creates. I know people and cities do not at all work in the way that I am about to describe, but imagine being able to shift the population of a city and all its necessary infrastructure to a second backup city so as to minimize disruptions. All the necessary modifications could be made to the first city without affecting people living there because they would be living and working elsewhere until the work was complete. Once the work is complete, everyone would go back to whatever address they previously had in the first city, and then work could start on improving the now vacant second city. Obviously, there are lots of issues that I have not described like how this works when many places already have a housing shortage, and having to build that second city in an “empty” area that can be provisioned with the same quantity and quality of resources enjoyed by people of the first city. In addition, I think a large complicating factor in construction today is something that I have not seen people talk about: when is it a good time to tear down existing structures. The lack of a “best before”/“expiration date” means structures stay up until failure or until the current owner wants to build something new in its place. The building stays up with possible inefficiencies (heating, cooling, energy use) that might be too expensive to remedy because of the age of structure.
- asdff 3y ago
  Its amazing disruption is even relevant to the discussion at all. Cities should not be so brittle that having two lanes on a single road go down for a cut would make a dent. In reality they aren't, but people are emotional beasts, they don't want to have to detour their longstanding commute for reasons they don't see themselves benefiting from. So they dig in, and decide this couple block stretch of road surface is the hill I die on, and local politicians better be damn sure to listen because no one else votes in local elections but these emotionally driven pissed off people. The whole time the press is pandering to them with false equivalency two sides reporting, when really the story is often about suburban car driving wealthy people being mildly inconvenienced for maybe 20 months so that the working class can see a generational improvement in mobility, and this is somehow an unacceptable tradeoff to make because of the status of these people.
  - 3y ago
givemeethekeys 3y ago
Hear me out: tunnels for cyclists. If tunnels are cheap, and I'm guessing small tunnels are cheaper than big tunnels, then we should have tunnels for cyclists - maybe even right under the sidewalks.
- syndicatedjelly 3y ago
  This is pretty common in Denver. There are lots of pedestrian/bicycle-only tunnels under many main roads just in my area. They recently spent a few million dollars improving an intersection nearby, and in the process added another cyclist tunnel underneath. It makes me really happy to see the city prioritize cyclists.
  - deleted 3y ago
    [deleted]
  - wolverine876 3y ago
    The tunnels are ways to cross the road - rather than a stoplight and crosswalk - or they follow the road and are essentially the bike lane?
    - drivers99 3y ago
      My guess would be underpasses like along the Cherry Creek trail, but I wouldn't call those tunnels. It's also not very usable when it floods. Skip to 8:50 https://www.youtube.com/watch?v=M2z76dDcT8c https://www.youtube.com/watch?v=M2z76dDcT8c
      - syndicatedjelly 3y ago
        Up in Westminster/Broomfield, there are several actual bike tunnels that go underneath a main road e.g. on Big Dry Creek bike trail underneath Wadsworth Blvd. The tunnels do get a bit wet/impassable if it has rained or snowed heavily, or if the nearby creek is running heavily (which is rare). But people dont typically bike in downpours. It doesn’t really matter, the point is that cyclists are totally separated from car traffic.
Night_Thastus 3y ago
Fascinating post! I had no idea about this transition from cut-and-cover to TBMs. It's always interesting to see how approaches change as technology advances and the ratio of cost to benefit changes.
- onthecanposting 3y ago
  The author paints with too broad a brush. There is significant differences in markets that drive these decisions. Cut-and-cover is standard in my state, but the land cost, density, and regulatory environment allow this. Directional drilling and jack-and-bore is very common for small diameter excavation, though.
  - Affric 3y ago
    > the land cost, density, and regulatory environment Cheap land, low density, lax environmental regulation?
    - onthecanposting 3y ago
      Correct. A major cut and cover in downtown Dallas would be insane. Bringing a TBM to put in a tunnel for bikes in Springdale Arkansas would be insane.
LegitShady 3y ago
Depending on how dense the urban area the cost of moving utilities even before construction is astronomical. If it can be done to coincide with cut and cover it can still be financial effective. It is highly disruptive to the entire area so it really depends on where the tunnel is being placed. Appropriate traffic and pedestrian accommodation plans are essential.
renewiltord 3y ago
Interestingly, the existence of TBMs has made SF Bay Area transit impossible to construct. Because TBMs exist, cut-and-cover is impossible since it can be pointed to as an alternative mechanism. However, they are hopelessly expensive here and consequently nothing gets built. Fascinating outcome. I think that's a cool outcome in a coordination problem, where added technology makes neither technology workable. This article was wicked sick, by the way. Great use of illustrations etc. This is free? Incredible. It's like the old web.
- mike_d 3y ago
  The tunnel itself (regardless of method) isn't the expensive part. Dense urban environments have a ton of stuff underground that was never accurately mapped. People don't like a city block bursting into flames because you hit a 4" gas line or the building they are in collapsing because it has an unmarked piling. Building up is actually a cheaper solution, we just need to get the NIMBYs under control. Imagine how nice it would be with 101 and 280 being double deckers the whole way.
  - fritzo 3y ago
    Let's not forget 1989 Loma Prieta quake that caused the top deck of the bay bridge to collapse. https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
    - mike_d 3y ago
      Which was actually a lot less dramatic than how people seem to remember it. A 70 foot section disconnected at one end. https://en.m.wikipedia.org/wiki/File:Bay_Bridge_collapse.jpg https://en.m.wikipedia.org/wiki/File:Bay_Bridge_collapse.jpg Freeway construction has changed a lot since the 70s and 80s. We now use ductile concrete that can flex without breaking, do extensive soil analysis for footings, and add seismic isolation systems in high risk areas.
      - sbuttgereit 3y ago
deleted 3y ago
[deleted]
SoftTalker 3y ago
What's wrong with elevated trains?
- gattr 3y ago
  They still make a lot of noise.
  - bluGill 3y ago
    Newer ones make less noise. The old steel structures in Chicago make a lot of noise. The sky train in Vancouver isn't silent, but it is not loud: they knew noise could be an issue and so built to make it not a problem.
    - NoNameHaveI 3y ago
      I for one, would much rather live in Elwood Blues's room than next to ANY interstate.
- steveBK123 3y ago
  They are very loud, they bathe streets/sidewalks/buildings in permanent shade, etc.
  - JoshTriplett 3y ago
    > They are very loud Loud and sometimes vibration-inducing. But this seems potentially feasible to mitigate through sound insulation (both on the train and on the buildings; frankly, our buildings should have a lot more sound isolation than they do). https://news.ycombinator.com/item?id=39401709 https://news.ycombinator.com/item?id=39401709 mentions newer elevated trains generating less noise, by designing for that requirement. > they bathe streets/sidewalks/buildings in permanent shade And permanent rain-cover. Seems like it'd often be a feature for many, though a bug for others.
    - steveBK123 3y ago
nox101 3y ago
> We used to dig up roads to put trains underneath – cheaply. Ever-better tunnel boring machines have made the disruption this causes unnecessary. What? Sure, tunneling machines make less disruption but unnecessary? You still have to build the stations, entrances, and venting systems. All of those breach the surface and the space needed to facilitate the construction still causes lots of disruption. But yes, more public transportation please. Lots of it!
- s1artibartfast 3y ago
  They didn't say disruption free. The quantity of disruption reduced is the part which is no longer necessary.
thimkerbell 3y ago
Dang and others, would it make sense to change the HN posting workflow such that a one-paragraph ChatGPT-produced summary was the first visible comment? Or otherwise make a summary easy to find. Also, ask the poster if the title could be improved, and suggest a possibly better one? Maybe it'd be unwise, of course.
- 93po 3y ago
  The decision makers over HN as a software platform are pretty resistant to any sort of change, which is likely a mixture of deliberate intention but also lack of incentive to mess with what's already working.
- s1artibartfast 3y ago
  I think automated summaries encourage shallow engagement and poor(er) comment quality. A summary is not the article, and the map is not the territory. What do you think they would add, and why do you think that is a good thing?
- bluGill 3y ago
  What I want is something that says does the article actually say anything interesting beyond the headline. all too often I've clicked on a link and discovered the headline said it all - good for the headline, but bad for in-depth understanding - often the commenters know far more than the article. In this case the article is worth reading. However it also is ignoring some important factors and so we still need to read the comments.
kfarr 3y ago
It's not that simple as "TBM is better" as others also have chimed in to say here. Real life example underway now: there's an SFPUC project in SF Mission district to improve stormwater drainage. City proposes TBM but this will result in years of having a huge tunnel entrance work facility in a residential neighborhood. Cut and cover would affect specific blocks but only for months and then move on to the next. Which is better? PS. To all the OpenAI folks, this project is happening around all your offices!
- Affric 3y ago
  To me this sounds like TBM to would still be better. You’re pissing off one set of residents immensely rather than every resident in the area sequentially. The marginal harm you do to yourself by pissing off residents is diminishing. Better to piss off fewer voters.
  - arcticbull 3y ago
    > You’re pissing off one set of residents immensely rather than every resident in the area sequentially. The marginal harm you do to yourself by pissing off residents is diminishing. Better to piss off fewer voters. This is the kind of thinking that leaves us mired in the past, unfortunately. As soon as these projects are completed everyone loves them and completely forgets about any minor transient misery a couple of restaurants were caused. Compensate them and move on. The billions of dollars saved using cut & cover vs. a TBM sets up a heck of a compensation fund. There's this real unstated mindset now where nobody should ever be inconvenienced, ever, no matter how mildly. It really holds back urban development. People will get over it.
    - msie 3y ago
      I have developed this feeling that the govt is so stingy with small amounts to compensate businesses yet are willing to waste great amounts in other cases. I guess that's politics for you.
    - bluGill 3y ago
      Robert Moses ran rough over New York for a decade or so and they are still paying the price for his roads. We have gone too far for sure, but there is a reason we did.
jlhawn 3y ago
Recently in the SF Bay Area, there's been a lot of displeasure by transit activists that object to VTA's BART to San Jose extension (it's being built by VTA not BART) who had the choice between two tunneling options: 1. Two small-bore TBMs ~2 stories underground, one for rail in each direction. This would require cut and cover for the stations only 2. One large-bore TBM ~7 stories underground, with technically enough space to fit an entire station platform inside but displaces a HUGE amount of soil/rock along the entire line, and require very deep stations that take a long time for riders to enter/exit. VTA consultants went with option 2 because they didn't want to disrupt the surface (again, only for the few blocks where the stations would be built) even though it costs $$ billions more. Many transit activists (including me) are upset because it makes the project both take much longer and cost more. We could save money by literally just giving billions of dollars to the businesses on the affected blocks. There's no geo-technical reason to go with the large-bore option. This has also led to a lot of recent VTA-negativity among these activists.
- Cerium 3y ago
  I have the same reaction. It seems to me that we could pay every business impacted by the work and come out ahead financially AND ahead on quality of service.
- viewtransform 3y ago
  Seems like VTA has so much money to play with they can't be arsed to save a few million here and there. https://www.youtube.com/watch?v=_pGUE1drr7A https://www.youtube.com/watch?v=_pGUE1drr7A
jbarham 3y ago
There's a short cut & cover freight railway "tunnel" near me in Footscray, Victoria, Australia (just west of central Melbourne). Here's the Google street view: https://www.google.com/maps/@-37.8035409,144.9065655,3a,75y,112.96h,76.11t/data=!3m6!1e1!3m4!1sRAtD3Q8cBLHJq2b7e6klyg!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@-37.8035409,144.9065655,3a,75y,... I used to walk over it almost every day when I worked at a coworking space in the old Lonely Planet HQ building. I think a lot of locals drive over it without ever realizing it's there.

190 points by jseliger 3y ago

mc32 3y ago

As far as I understand it, and this may be outdated, cut and cover is way cheaper than boring. And you only bored tunnels if you had no other choice --like Big Bertha in Seattle. BaRT was mostly cut and cover as obviated by going under Market and Mission streets. Maybe new boring machines are faster and cheaper and break down less than before.

gumby 3y ago
Yes, cut and cover is cheaper to execute than using a boring machine in most cases and when possible. But the externalities of cut and cover can be very expensive (blocks streets, and hurts nearby businessen even to the point of going out of business). Those second order effects, even if transient on a long term scale, can cause expensive hold ups. Other externalities are the need to get around existing infrastructure, some of which could have over a century of continuous use. So for example in NY it is almost impossible (look at the 2nd ave subway, which is mostly pretty shallow) while in LA cut and cover was no problem at all.
- BobaFloutist 3y ago
  I wonder if the price difference between boring and cut and cover is greater than the cost to just...cover business's expenses (rent, loan interest, payroll) for the time it takes to get cut and cover done on that block. Could we just pay them off?
  - actionfromafar 3y ago
    That sounds like it could be cost effective if one only includes the individual businesses and cover their losses, but it can still cause second order effect harm, like customers changing habits and not returning to the original place. Something to think about. Suboptimal infrastructure is also costly, of course...
    - BobaFloutist 3y ago
      Honestly I'd be fine with it if the public agencies just used it as a justification for a eminent-domain style "We're going to do this project this way in the interest of the public, we're giving you some cash to cover your immediate costs, and that's that."
    - immibis 3y ago
      The justification for business owners making profits is that it's payment for taking risks. Why then are we trying to shield them from risks while still allowing them to make profits?
      - bluGill 3y ago
        Because we want business to take those risks. In the end I benefit from those businesses - not all of them, but some of them. Businesses should take risks. However government should not add extra risk without careful consideration.
      - samatman 3y ago
        Business owners making profit needs no justification, that's entirely backward. Anywhere there are people, there are goods for sale. The ones who need to justify themselves are the ones who propose to restrict this. It can be done, I consider the restrictions on the nuclear weapons and slave markets eminently justifiable. But in a free society, the default is freedom.
  - gumby 3y ago
    For private sector projects people do get bought off (in a non-corrupt sense of that phrase) but that seems to be unacceptable for public projects for some reason. I'm talking about the US here -- no idea elsewhere.
    - BobaFloutist 3y ago
      I assume the second private was supposed to be public?
      - gumby 3y ago
        Yes, thanks. I was still in the edit window so I fixed it.
- hinkley 3y ago
  I wonder how many different ways people have tried cut and cover over the years. I'm talking here of the horizontal part of the project, not the vertical. It seems like you usually have one, or maybe two, moving work sites, and they go block by block removing the street, and replacing it behind them at some point. Any business near the sites is choked off from foot traffic for a while, even if the site isn't in front of their door yet. Is it more or less disruptive if you do a checkerboard pattern instead? Instead of n months of construction around your favorite coffee shop, would it be better to have n/2 months of construction now, and n/2 months of construction in July? Maybe that depends on where you are on the street. If, for instance, you start at both ends, then the businesses in the middle of the cut have construction sites boxing them in for almost twice as long as anyone else does. Or maybe that just means more people of means mad at elected officials.
  - bluGill 3y ago
    The problem is the street overall is blocked off for the duration. Sure it looks like only one block is stopped, but in reality people who have to travel that block are backed up all the way, and so they will look for alternate routes for the duration. If you could build the entire thing in 2 weeks (per year) people would be happy with a full road closure - they would all take vacation for those two weeks. This is for the entire city - close all roads to non-emergency traffic for two weeks, fix them all up - everyone not involved in road work or essential services would just go on vacation. You cannot do this of course, but that is what people really want.
    - hinkley 3y ago
      I thought about that too. The problem with trains is that they always need to run in the primary direction of traffic. So you can't really build them on cross-streets and avoid disrupting the main thoroughfares. Otherwise you'd often end up with a train to nowhere. The main exception being when traffic is curved, going around some obstruction that the train can cut across. I recall when South Lake Union got its trolley, one of the things they pointed out was that property values next to a trolley drop, but property values 1 block away go up more. Everyone wants to be a couple blocks from transit, not living above it. So even if you avoided the main road going parallel to it, you're probably tearing up even more desirable real estate and commercial zoning.
- asdff 3y ago
  What people often forget about modern cut and cover is that it is only disruptive for a short period of the project because they can put a temporary road deck over the cut and do most disruptive work overnight. Its how LA metro built a subway station in the middle of Beverly Hills.
  - bluGill 3y ago
    There are several options to make cut and cover less disruptive. Other options are dig in the sidewall supports, then build the cover over the current road surface, finally dig out underneath. It is still tunneling, but it uses most of what makes cut and cover cheaper than a TBM.
kdmccormick 3y ago
Did you read? Article states that cut and cover is still much cheaper technically, but can end up being practically more expensive due to the political/legal ramifications of the surface disruption.
- mc32 3y ago
  Depends, Gaoxiong did a C&C and they were able to mostly mitigate the second order effects of C&C. Yes, in some sections some traffic was affected more, but apparently it wasn't widely disruptive. It can be done. It helps when you can complete the project in a few years and not take a decade to build out a single line. So politics does have an impact on feasibility and practicality of C&C.
masklinn 3y ago
> As far as I understand it, and this may be outdated cut and cover is way cheaper than boring. When you ignore all the side effects, sure (especially if you also ignore the risks of blowing the timeline). Trenchless tech is spreading fast even in small-ish (street utility scale) construction. > Maybe new boring machines are faster and cheaper than they used to be. I'm not sure that's even the case, AFAIK TBMs are still custom-built for the job, highly geology-dependent, and require a ton of babysitting. If you hit an unexpected patch of really different geology things can get really dicey.
- bluGill 3y ago
  > TBMs are still custom-built for the job This is semi-true. They are built for the job, but the design is standard. What is custom is the exact size of the tunnel, and thus all the supports. TBMs generally last a lot longer than the job, so a city could save a lot of money if they planed to keep using their TBM, constantly digging tunnels. Start with a north-south line, then use the same TBM to build an east-west line (or southeast/northwest), and so on. However most cities are unable to find the continuous budget to do that and so when they are ready for the next one the old TBM is no longer worth using, and in any case they no longer have trained crew to run it. > highly geology-dependent, Soft water logged earth needs different machines from hard rock. There are combination machines, but if you can determine which you need you save a lot of money ordering the geology specific machine. Get this wrong and you end up with a TBM and partial tunnel under the city. > require a ton of babysitting. 12 people per shift is the number I've heard (NYC uses double which is one of the smaller reasons things cost so much there). The work is mostly routine though. However the TBMs do break once in a while and they everything stops while you repair them.
matthewmacleod 3y ago
The article discusses this extensively.
hinkley 3y ago
There's the construction cost, and there's lost income from the people who voted for you. Not all of the money spent on construction is tax dollars. Think about every time you've been stuck in traffic because there are 3 roads that get you from A to B, and some jackass at city hall thought it would be a good idea to permit road work on 2 of them on the same day. We are used to highway on-ramps being replaced in days to weeks, but removing an entire street, digging up everything under it, being careful not to nick the utility lines and pipes, then packing dirt back in around them without tearing them, then rebuilding the street on top, that's a lot. Especially for the businesses on that road. We end up with transportation solutions that are suboptimal because we don't have the political will to tear off the bandaid. This on-ramp is in the wrong place because the old one was in the right place, but was built in a terrible way and had to be removed for safety while still handling daily commutes.

epistasis 3y ago

I'm very grateful for those posting and upvoting interesting construction articles on HN, this is a key area of our economy that is stagnant and could really use some improvement. Traditional media do a terrible job of coverage, and spreading articles like this helps get better mainstream coverage. A lot of the bad things about construction come down to incumbent players being able to force extremely costly methods on anybody who wants to improve the world. So a lot of the challenge is political. Solving political problems is really hard, but when technology can sidestep the problem, there's a lot that becomes possible. For those in the Bay Area, we are seeing aversion to cut and cover be a huge hassle for our stations. The depth of some of the new transit stations will be a huge inconvenience for generations of transit users, all to satisfy a short term disruption of a far smaller number of people. This problem could have been solved with money, for those affected, if it were not for the politics.

theluketaylor 3y ago
Deep stations are also unbelievably expensive. Deep tunnels are not that bad, but the resulting stations explode the budget for transit to the point getting the project green lit in the first place is nearly impossible. Plus with the same set of dollars you are building a lot less transit.
- hinkley 3y ago
  The deepest station in Seattle has smelled like someone tried to make cheese from moldy gym socks since the day it opened. I believe it opened and immediately shut again so they could try to deal with the water problem [though responder says no]. I went through when it was briefly open and again after. They made it less bad, but it was still pretty awful. A club I belonged to met at a library near the station so it was easiest for me to just hop on the light rail after work and then take it back to the bus terminal after but gods did I want to hold my breath the entire time.
  - oasisbob 3y ago
    > The deepest station in Seattle has smelled like someone tried to make cheese from moldy gym socks since the day it opened. Maybe it's just a matter of opinion, but I never found the Beacon Hill light rail station to smell like anything other than raw concrete, similar to DC metro or any other deep tunnel system. I lived in the neighborhood at the time, and don't remember the station shutting down due to water ingress. Opening was delayed due to issues with overexcavation, but that threat was with sinkholes opening to the public above, not issues with the tunnel itself.

yawnxyz 3y ago

If you're ever in Sydney, go to the St. James station (I think) and you'll see lots of historical photos of using horse and carriage to build the first Sydney metro stations. Very very cool!

hinkley 3y ago
I hear there's a museum in Tokyo as well. When I was there in the 90's they were excavating a station that was found by a construction crew. The plan was to turn it into a subway history museum. I was told that the line was abandoned after an earthquake, and they lost track of the location of some of the stations (or at least, this one). It was on a green strip of undeveloped land, so I have a small suspicion that a landslide may have been involved. I mean how else do you 'lose' a building?
- bobthepanda 3y ago
  It is highly doubtful that anyone in bubble-era Japan “lost” a piece of property. The rail companies in particular are keen, savvy property developers. During the bubble, the Imperial Palace grounds had a higher real estate valuation than all of California.
  - hinkley 3y ago
    I feel like you might be underestimating the age of subway lines. 2027 will be the centennial anniversary of the Ginza Line, and that's a baby compared to Paddington Station, which had its sesquicentennial a decade ago. Apparently the Tokyo postal service had a private line in 1915. I kinda wonder if that's the one they 'found'.

tareqak 3y ago

I think we should find ways to get ahead of the disruption that construction creates. I know people and cities do not at all work in the way that I am about to describe, but imagine being able to shift the population of a city and all its necessary infrastructure to a second backup city so as to minimize disruptions. All the necessary modifications could be made to the first city without affecting people living there because they would be living and working elsewhere until the work was complete. Once the work is complete, everyone would go back to whatever address they previously had in the first city, and then work could start on improving the now vacant second city. Obviously, there are lots of issues that I have not described like how this works when many places already have a housing shortage, and having to build that second city in an “empty” area that can be provisioned with the same quantity and quality of resources enjoyed by people of the first city. In addition, I think a large complicating factor in construction today is something that I have not seen people talk about: when is it a good time to tear down existing structures. The lack of a “best before”/“expiration date” means structures stay up until failure or until the current owner wants to build something new in its place. The building stays up with possible inefficiencies (heating, cooling, energy use) that might be too expensive to remedy because of the age of structure.

asdff 3y ago
Its amazing disruption is even relevant to the discussion at all. Cities should not be so brittle that having two lanes on a single road go down for a cut would make a dent. In reality they aren't, but people are emotional beasts, they don't want to have to detour their longstanding commute for reasons they don't see themselves benefiting from. So they dig in, and decide this couple block stretch of road surface is the hill I die on, and local politicians better be damn sure to listen because no one else votes in local elections but these emotionally driven pissed off people. The whole time the press is pandering to them with false equivalency two sides reporting, when really the story is often about suburban car driving wealthy people being mildly inconvenienced for maybe 20 months so that the working class can see a generational improvement in mobility, and this is somehow an unacceptable tradeoff to make because of the status of these people.
- 3y ago

givemeethekeys 3y ago

Hear me out: tunnels for cyclists. If tunnels are cheap, and I'm guessing small tunnels are cheaper than big tunnels, then we should have tunnels for cyclists - maybe even right under the sidewalks.

syndicatedjelly 3y ago
This is pretty common in Denver. There are lots of pedestrian/bicycle-only tunnels under many main roads just in my area. They recently spent a few million dollars improving an intersection nearby, and in the process added another cyclist tunnel underneath. It makes me really happy to see the city prioritize cyclists.
- deleted 3y ago
  [deleted]
- wolverine876 3y ago
  The tunnels are ways to cross the road - rather than a stoplight and crosswalk - or they follow the road and are essentially the bike lane?
  - drivers99 3y ago
    My guess would be underpasses like along the Cherry Creek trail, but I wouldn't call those tunnels. It's also not very usable when it floods. Skip to 8:50 https://www.youtube.com/watch?v=M2z76dDcT8c https://www.youtube.com/watch?v=M2z76dDcT8c
    - syndicatedjelly 3y ago
      Up in Westminster/Broomfield, there are several actual bike tunnels that go underneath a main road e.g. on Big Dry Creek bike trail underneath Wadsworth Blvd. The tunnels do get a bit wet/impassable if it has rained or snowed heavily, or if the nearby creek is running heavily (which is rare). But people dont typically bike in downpours. It doesn’t really matter, the point is that cyclists are totally separated from car traffic.

Night_Thastus 3y ago

Fascinating post! I had no idea about this transition from cut-and-cover to TBMs. It's always interesting to see how approaches change as technology advances and the ratio of cost to benefit changes.

onthecanposting 3y ago
The author paints with too broad a brush. There is significant differences in markets that drive these decisions. Cut-and-cover is standard in my state, but the land cost, density, and regulatory environment allow this. Directional drilling and jack-and-bore is very common for small diameter excavation, though.
- Affric 3y ago
  > the land cost, density, and regulatory environment Cheap land, low density, lax environmental regulation?
  - onthecanposting 3y ago
    Correct. A major cut and cover in downtown Dallas would be insane. Bringing a TBM to put in a tunnel for bikes in Springdale Arkansas would be insane.

LegitShady 3y ago

Depending on how dense the urban area the cost of moving utilities even before construction is astronomical. If it can be done to coincide with cut and cover it can still be financial effective. It is highly disruptive to the entire area so it really depends on where the tunnel is being placed. Appropriate traffic and pedestrian accommodation plans are essential.

renewiltord 3y ago

Interestingly, the existence of TBMs has made SF Bay Area transit impossible to construct. Because TBMs exist, cut-and-cover is impossible since it can be pointed to as an alternative mechanism. However, they are hopelessly expensive here and consequently nothing gets built. Fascinating outcome. I think that's a cool outcome in a coordination problem, where added technology makes neither technology workable. This article was wicked sick, by the way. Great use of illustrations etc. This is free? Incredible. It's like the old web.

mike_d 3y ago
The tunnel itself (regardless of method) isn't the expensive part. Dense urban environments have a ton of stuff underground that was never accurately mapped. People don't like a city block bursting into flames because you hit a 4" gas line or the building they are in collapsing because it has an unmarked piling. Building up is actually a cheaper solution, we just need to get the NIMBYs under control. Imagine how nice it would be with 101 and 280 being double deckers the whole way.
- fritzo 3y ago
  Let's not forget 1989 Loma Prieta quake that caused the top deck of the bay bridge to collapse. https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
  - mike_d 3y ago
    Which was actually a lot less dramatic than how people seem to remember it. A 70 foot section disconnected at one end. https://en.m.wikipedia.org/wiki/File:Bay_Bridge_collapse.jpg https://en.m.wikipedia.org/wiki/File:Bay_Bridge_collapse.jpg Freeway construction has changed a lot since the 70s and 80s. We now use ductile concrete that can flex without breaking, do extensive soil analysis for footings, and add seismic isolation systems in high risk areas.
    - sbuttgereit 3y ago

deleted 3y ago

[deleted]

SoftTalker 3y ago

What's wrong with elevated trains?

gattr 3y ago
They still make a lot of noise.
- bluGill 3y ago
  Newer ones make less noise. The old steel structures in Chicago make a lot of noise. The sky train in Vancouver isn't silent, but it is not loud: they knew noise could be an issue and so built to make it not a problem.
  - NoNameHaveI 3y ago
    I for one, would much rather live in Elwood Blues's room than next to ANY interstate.
steveBK123 3y ago
They are very loud, they bathe streets/sidewalks/buildings in permanent shade, etc.
- JoshTriplett 3y ago
  > They are very loud Loud and sometimes vibration-inducing. But this seems potentially feasible to mitigate through sound insulation (both on the train and on the buildings; frankly, our buildings should have a lot more sound isolation than they do). https://news.ycombinator.com/item?id=39401709 https://news.ycombinator.com/item?id=39401709 mentions newer elevated trains generating less noise, by designing for that requirement. > they bathe streets/sidewalks/buildings in permanent shade And permanent rain-cover. Seems like it'd often be a feature for many, though a bug for others.
  - steveBK123 3y ago

nox101 3y ago

> We used to dig up roads to put trains underneath – cheaply. Ever-better tunnel boring machines have made the disruption this causes unnecessary. What? Sure, tunneling machines make less disruption but unnecessary? You still have to build the stations, entrances, and venting systems. All of those breach the surface and the space needed to facilitate the construction still causes lots of disruption. But yes, more public transportation please. Lots of it!

s1artibartfast 3y ago
They didn't say disruption free. The quantity of disruption reduced is the part which is no longer necessary.

thimkerbell 3y ago

Dang and others, would it make sense to change the HN posting workflow such that a one-paragraph ChatGPT-produced summary was the first visible comment? Or otherwise make a summary easy to find. Also, ask the poster if the title could be improved, and suggest a possibly better one? Maybe it'd be unwise, of course.

93po 3y ago
The decision makers over HN as a software platform are pretty resistant to any sort of change, which is likely a mixture of deliberate intention but also lack of incentive to mess with what's already working.
s1artibartfast 3y ago
I think automated summaries encourage shallow engagement and poor(er) comment quality. A summary is not the article, and the map is not the territory. What do you think they would add, and why do you think that is a good thing?
bluGill 3y ago
What I want is something that says does the article actually say anything interesting beyond the headline. all too often I've clicked on a link and discovered the headline said it all - good for the headline, but bad for in-depth understanding - often the commenters know far more than the article. In this case the article is worth reading. However it also is ignoring some important factors and so we still need to read the comments.

kfarr 3y ago

It's not that simple as "TBM is better" as others also have chimed in to say here. Real life example underway now: there's an SFPUC project in SF Mission district to improve stormwater drainage. City proposes TBM but this will result in years of having a huge tunnel entrance work facility in a residential neighborhood. Cut and cover would affect specific blocks but only for months and then move on to the next. Which is better? PS. To all the OpenAI folks, this project is happening around all your offices!

Affric 3y ago
To me this sounds like TBM to would still be better. You’re pissing off one set of residents immensely rather than every resident in the area sequentially. The marginal harm you do to yourself by pissing off residents is diminishing. Better to piss off fewer voters.
- arcticbull 3y ago
  > You’re pissing off one set of residents immensely rather than every resident in the area sequentially. The marginal harm you do to yourself by pissing off residents is diminishing. Better to piss off fewer voters. This is the kind of thinking that leaves us mired in the past, unfortunately. As soon as these projects are completed everyone loves them and completely forgets about any minor transient misery a couple of restaurants were caused. Compensate them and move on. The billions of dollars saved using cut & cover vs. a TBM sets up a heck of a compensation fund. There's this real unstated mindset now where nobody should ever be inconvenienced, ever, no matter how mildly. It really holds back urban development. People will get over it.
  - msie 3y ago
    I have developed this feeling that the govt is so stingy with small amounts to compensate businesses yet are willing to waste great amounts in other cases. I guess that's politics for you.
  - bluGill 3y ago
    Robert Moses ran rough over New York for a decade or so and they are still paying the price for his roads. We have gone too far for sure, but there is a reason we did.

jlhawn 3y ago

Recently in the SF Bay Area, there's been a lot of displeasure by transit activists that object to VTA's BART to San Jose extension (it's being built by VTA not BART) who had the choice between two tunneling options: 1. Two small-bore TBMs ~2 stories underground, one for rail in each direction. This would require cut and cover for the stations only 2. One large-bore TBM ~7 stories underground, with technically enough space to fit an entire station platform inside but displaces a HUGE amount of soil/rock along the entire line, and require very deep stations that take a long time for riders to enter/exit. VTA consultants went with option 2 because they didn't want to disrupt the surface (again, only for the few blocks where the stations would be built) even though it costs $$ billions more. Many transit activists (including me) are upset because it makes the project both take much longer and cost more. We could save money by literally just giving billions of dollars to the businesses on the affected blocks. There's no geo-technical reason to go with the large-bore option. This has also led to a lot of recent VTA-negativity among these activists.

Cerium 3y ago
I have the same reaction. It seems to me that we could pay every business impacted by the work and come out ahead financially AND ahead on quality of service.
viewtransform 3y ago
Seems like VTA has so much money to play with they can't be arsed to save a few million here and there. https://www.youtube.com/watch?v=_pGUE1drr7A https://www.youtube.com/watch?v=_pGUE1drr7A

jbarham 3y ago

There's a short cut & cover freight railway "tunnel" near me in Footscray, Victoria, Australia (just west of central Melbourne). Here's the Google street view: https://www.google.com/maps/@-37.8035409,144.9065655,3a,75y,112.96h,76.11t/data=!3m6!1e1!3m4!1sRAtD3Q8cBLHJq2b7e6klyg!2e0!7i16384!8i8192?entry=ttu https://www.google.com/maps/@-37.8035409,144.9065655,3a,75y,... I used to walk over it almost every day when I worked at a coworking space in the old Lonely Planet HQ building. I think a lot of locals drive over it without ever realizing it's there.