PBA was appointed to assess Pinner Wood School after a hole opened in the staff car park in 2015. Harrow Council commissioned specialist engineers from PBA to conduct further analysis which showed the school buildings and playgrounds were sitting on top of a disused chalk mine. The analysis also showed that some of the tunnels had partially collapsed, leading to a risk of further holes opening on the surface. The findings led the council, the school governors and the Pinner Wood leadership team to close the school on 23 March 2017.
Since then PBA, and geospatial engineering consultancy, Geoterra, have been conducting in depth surveys of the site to determine the extent of the mines and ensure they are made safe.
The school is now open to all pupils and Dr. Clive Edmonds, PBA Project Director, and Stuart Chandler, PBA Project Manager, together with site engineers Natasha Withers and Harry Gordon, were welcomed to the school by the headteacher, Sarah Marriott, to help the children understand what had happened.
Clive explained that the mine likely dates from at least the early 1800s. As is common for chalk mines of this age there are no mine abandonment plans so PBA had to discover the extent and state of the mine workings. This was confirmed by 3D-laser surveys, above and below ground, using the most up-to-date technology available.