an “exceptional event” caused by Belfast’s “unique clay geology”

It looks like that suspicion about a connection between the road surface collapse on Cromac Street and work on the Belfast Sewers Project was probably correct. From the BBC report

The collapse of one of Belfast’s busiest roads was caused by an air pocket rising to the surface, an NI Water spokesman has said. Bill Gowdy said the rupture in Cromac Street damaged an old Victorian sewer about four metres under the road. He said the air pocket was probably disturbed a year ago during work on the Belfast Sewers Project. It will take a week to repair the road, and talks about minimising traffic disruption have been taking place.

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  • joeCanuck

    Someone’s talking through their hat.
    Air pockets don’t rise to the surface; it’s an illusion. An air pocket forms underground, say from the collapse of an old sewer, earth from above falls into it creating the illusion.

  • Sean

    Sounds like what we call “loon shit”

  • aquifer

    Nothing at all to do with contractors failing to consolidate the ground under the big new pipes then.

    Thats a relief, as contractors laying gas mains used to just throw the clay back in around the pipes in one go. creating a risk of road surface cracking later.

  • joeCanuck

    Aquifier,
    When I was involved we would backfill like you say and put a temporary tarmac surface on. But we were required by the Roads Service to do a resurfacing approximately 6 months later since there would invariably be some sinkage.

  • Coll Ciotach

    Cannot see how you can possibly blame the Sewers Project for lack of backfill in Cromac.

  • aquifer

    Joe

    Thanks for ‘filling in’ the detail on this. And after 6 months we just hope that the sinkage does not continue.