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Investigations into Plumstead ground collapse continue

Brickfield collpase

Hexagon Housing has said that the cause of a ground collapse below recently completed houses in Plumstead is underway as the hole is backfilled with concrete.

The ground below two houses at Brickfield Cottages collapsed on Monday into what has been described as a sinkhole.

London Fire Brigade has reported the hole to measure 5m by 5m but did not confirm he depth. It said that a cordon of 25m had been placed around the collapse.

The houses are reported to have been completed in the last couple of years and were built on a site formerly used by a soft drinks factory. British Geological Survey (BGS) records suggest that the geology at the site is formed from the Thanet Sands.

Hazard mapping specialist Groundsure has told GE that historic maps of the area show the cottages to be located within the site boundary of a former brick works. Groundsure’s records also indicate that BGS’s non-coal mining hazards classify the site as a “likely” location of a hazard and the PBA mining cavities database has three records within 100m of the site.

Residents from 40 properties were evacuated following the incident but 30 households have now been allowed to return to the housing association properties but access has been restricted to pedestrians only. No date has been set for when residents living in properties closest to the collapse will be able to return.

Historic maps demonstrate site hazards

Brickfields map 1888

Historic map from 1888

Brickfield map 1897

Historic map from 1897

Brickfields hazard map

Location of hazards held on databases by Groundsure

 

Readers' comments (1)

  • In my experience, if drainage conditions are changed the Thanet Sand can be transported into open joints in the underlying Chalk - most often associated with soakaways.

    Mike Stephen, CEng MICE.

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