Underground Cities Planning – Streetsblog USA

Asal Bidarmaghz, Senior Lecturer in Geotechnical Engineering at the University of New South Wales in Sydney, discusses underground infrastructure and its importance for the future of cities, including underground climate change, coordination between projects at long term and appropriate land use.

For those of you who hear your news through your eyes and not your ears, there is an edited transcript below the audio player. If you want a full, unedited transcript (with a few typos!), click here. If you want to listen, it’s here:

Jeff Wood: So the paper that I wanted to discuss with you, because I was super fascinated by the paper, was published by the University of New South Wales about your work on the plans for underground city. Why would a city want to create a plan for underground infrastructure? I mean, we have city plans for the surface, but why would they want to go and think about the basement?

Asal Bidarmaghz: That’s a very good question. I guess it’s kind of getting to the new trend in some big populated cities that we’ve gone up and out enough, and then it’s now to go underground. It’s about the fact that premium land is limited and already taken. If you want to live in a city, there is definitely a way down. Maybe years ago, decades ago, there was another reason for this, for example, because of wartime security or because of weather conditions in cold climate regions. But these days if you look at Singapore, for example, thinking of their underground city, the main reason for that is that they think they need to accommodate a huge amount of residents, a certain number of residents in the future , to maintain the economy.

[It’s a] small island and they have to go underground. This will happen in many other cities. If you look at New York, it’s also kind of congested, and in Australia, we might not have that problem yet because Australia is a huge island. We don’t suffer from space limitations yet, but we will because cities won’t grow as fast as before. As the population in cities is growing rapidly, not just in Australia, but around the world. So the main reason nowadays to go underground is space. That’s why we buried our tunnels. The same reason can [justify] put our retail and entertainment spaces underground.

Wood: It’s really interesting. You mentioned Singapore. One of the interesting things about what they did is they reformed their land use laws specifically to remove property under their basements, which I found very interesting. Our mining and land rights specifically [are] major obstacles to underground politics in many places.

Bidarmaghz: Absolutely. Yes. That’s one of the things that needs to be addressed early on, for example, in the UK it’s like you own heaven in hell, and that needs to change if they’re actually going to use the route underground more than they used to. These are the first of these policies that need to be changed to just avoid some private land issues and so on.

Wood: How would a municipality or city go about making these changes? Is it just a simple change in zoning or land use law, or is it even more complicated because it’s underground and it’s kind of a surveying issue and people probably don’t know really what the underground rocks are, or these geological problems are, etc. .?

Bidarmaghz: From the point of view of land rights, I don’t think it will be very complicated. I’m no expert, it’s not my forte, but I don’t think it’s going to be a very complicated thing. It only prevents some over-excavation and over-use by the private sector, as happened before. For example, in London, we used to see basements up to 20 meters below the surface, private basements with parking lots, with tennis courts, with lots of entertainment areas. So it will definitely stop. But from there, for example, from an engineering point of view or what’s happening underground, as I mentioned earlier, I think we can certainly classify the most important challenges into three [or] four categories. One is urban planning or underground, urban-underground planning issues.

You have to first know what’s going on underground right now — it’s dynamic — and then have a good idea of ​​what’s going to happen. What are the future scenarios, to be able to properly map the subsoil in major cities and then come up with sustainable planning when we have no idea what our various assets are, what are the utilities? What exactly is happening? What are the high voltage cables or the sewer network? We can’t really think of an overall urban basement plan for many years to come as a long-term plan. It’s something to settle.

The other thing is that from an engineering perspective. So far, when we want to build a tunnel or any underground structure, the most important thing is this. So of course the tunnels mainly go under the transport tunnels under the city. Also, as long as the ground is stable enough, it’s doable and we can dig and we can have a stable structure. That’s it. However, this is not the only thing we should consider. You have to think about what the plan will be like in 50 years, in 100 years. If I build my tunnel here today, will it prevent other sustainable developments in the future? It’s something that we don’t look at, not in Australia or anywhere else that I know of. In some countries like the United States or the United Kingdom, they have started to take an interest in it with considerable help, for example, from the British Geological Survey which comes into play to map the subsoil. But in many big cities, that hasn’t happened yet.

The other thing, which may not be of interest to engineers as much, but from an environmental perspective, what do we really do with the environmental aspects of this groundwater? What happens if the temperature of the water table rises significantly? What will happen to all the species living in this water table under the cities? Is that something, or what will happen to the safety of that groundwater? If it is drinking water, what are the chemical reactions that could occur due to the increase in temperature? There are so many aspects we can look at. It’s definitely beyond engineering. It is town planning. It’s environmental. It’s policy development.

Bonny J. Streater