“Periodically we can get voids forming under the roads”

A short iol report sums it up – “Belfast street fall[s] into large hole”. The BBC report includes this explanation

Roads Service spokesman Colin Brown said the city is built upon a deposit of soft clay, silt and mud known as “Belfast Sleech”. “Periodically we can get voids forming under the roads,” he said. “Sometimes it’s very clear what has caused it, other times it’s quite a mystery. “It could be a substantial hole in the road but we’ll know more later.”

Although you’d have to suspect there might be a connection with this

The depression in the road is above a storm-water tunnel in the multi-million pound Belfast Sewers Project.

Work has been ongoing since 2005 on constructing a six-mile network of tunnels running underneath the city.

The key junction in the sewerage network is located at Cromac Street, in the area of the collapsed road.

Updated here.

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  • iluvni

    Great job again.
    Congratulations to all involved.

  • Traveller

    I know Colin from his work in the roads service. Excellent worker and excellent knowledge.

  • The usual unit of measurement for these things (at least in London) is the ddb.

    So, there was a recent event in Hampstead Heath Street. The shop-owners reported to Thames Water unwonted liquidity in their basements. They were assured all was well, and, if it wasn’t, it was all their own problem. Minutes later, the entire road surface disappeared downwards leaving a cavity measured at between one and two double-decker buses.

    Then, just a week or so ago, the Times used a new scale of dimension for the Heritage Coast (used to be Dorset, before the re-branding) pliosaur: a bendy bus.

    When I mentioned all this, the Pert Young Piece of the family told me all these measurement scales were defined on wikipedia. She failed to quantify Wales in terms of ddbs, however. So I declared that one a draw.

  • Comrade Stalin

    Mystery my ass, I’ve never heard of a road collapsing on itself in recent memory like this. It’s bound to be related to the water upgrade.

  • “Road collapses in Belfast – Water Service looking into it”

  • LGO

    Yes, but half the city is built on that sleech. And given the full extent of these works, and other building works happening on down at Custom House Square, where it’s all sleech underneath, I am truly surprised it doesn’t happen more often.

    But sure, doesn’t it give a great opportunity to give the public sector a bit of a kick?

  • igor

    What a metaphor for our beloved administration. A thin veneer of tarmac over hollowed out sleech.

  • wild turkey

    ‘A thin veneer of tarmac over hollowed out sleech. ‘

    nice one igor.

    something similar came to mind but it involved the by now tedious reference to scatalogical terms.

  • John Laurie

    It was caused by a black hole popping into existence from the vacuum and eating a chunk of earth before going back to whence it came.
    We’re all doomed, I tell you, doomed.

  • igor

    Hasnt there always been a void in the Markets?

  • igor

    I hope that Martin will be straight onto Gordon Brown to complain

  • I had some issues about believing this one: yeah, there’s a hole there, but “sleech”? I await being assured by all the usual suspects of Sluggerdom that I was uniquely unaware of the word.

    Thanks to the OED I am now reconciled to the word’s existence, so it will rarely be far from my thoughts:

    Mud deposited by the sea or a river; soil composed of this.
    1587 FLEMING Contn. Holinshed III. 1540/1 Wher the slub or sleech is fifteene foot deepe at the least, and the maine rocke immediatlie vnderneath it.

    But why is “Belfast sleech” different? Was it only invented (or named) in the 1970s (when it appears in an engineering abstract about a Harland and Woolf project)? Hold on a mo’: here it is earlier, around 1955, in another document about an Extension of the Runway at RN Air Station, Belfast.. I assume that’s the later RAF Sydenham , en route to be Belfast City, before its latest manifestation as George Best.

    The best definition I’ve found so far was about the Victoria Square development in New Civil Engineer (I take it for the lonely-hearts column, © Kenneth Horne):

    ‘Eight metres of sleech is something you only find in Belfast, ‘ says Farrans design co-ordinator Stephen McCaffrey.

    Sleech is the local term for soft estuarine quasi-thixotropic deposits that underlie both banks of the River Lagan in the heart of the city.

    Up to the end of the 19th century the entire centre of the city was supported on a forest of timber piles, most of which are still performing their original function.

    Which left me a lot wiser. It still seems wide open to mis-interpretation by Finbarr Saunders

  • Comrade Stalin

    I used to work in a building near the custom house. Every time it rained really hard, the basement (which was used as a carpark) flooded, sometimes quite seriously.

    It turned out that during heavy rain, the nearby river (Farset) which runs under High Street burst its banks. The building, along with other buildings in the area (as Malcolm has just said) was built on timber piles which rotted over the years and caused the foundations to deteriorate to the point where the water got in. I imagine that underpinning works, like those done under the Albert Clock, will be necessary for some of the old buildings in the area.

    The runway at the city airport is also sinking, and apparently the big BMI planes they use for their Heathrow flight are accelerating this process.

  • joeCanuck

    You’re right. There’s no such thing as Belfast sleech.
    In my early career I was responsible for having many miles of trenches dug to lay cables all over Belfast, later over the whole of N.I. In contracts, we specified 3 types of soil conditions for which different excavation rates were paid; earth, rock and sleech, sleech being paid the most.
    It was awful stuff to excavate, almost impossible to shore up the sides of the trenches; they just oozed away too fast. Ended up with some extra wide trenches. Luckily enough, although the whole city centre is built on the stuff, we didn’t come across it much at the depths we were digging, usually 3 feet.
    Never heard anyone call it Belfast sleech.

  • Dev

    Damn you quasi-thixotropic deposits!!

  • Moochin Photoman

    Found an article in issue 11 of the vacuum Under Belfast by Ian Mitchell which references

    “Red laminated clay, which occurs in the Belfast area and was formerly used in the manufacture of bricks, was also deposited in the late to post-glacial lakes. Lastly the Holocene (10,000 years to present) deposits that occur under Belfast were mainly deposited on the flood plain of the River Lagan. However, in addition to that alluvium much of central Belfast is underlain instead by a deposit of soft grey mud, silt and fine sand with numerous sea shells, in particular oysters. This was deposited at a time of elevated sea level in the estuary of Belfast Lough and is graphically known as “sleech”. It is over 15m thick in the docks area of the city and 3-10m in the commercial and inner city areas”