Harrow Council Letter To Parents

Closure of Pinner Wood School site at end of school day today
Dear parents and carers,

The site of Pinner Wood School is closing at the end of the school day today after a joint decision by Harrow Council, the governors and the leadership team of Pinner Wood School.

The reason for the closure is that geotechnical surveys have this week reported an unacceptable risk that the ground beneath the school buildings and playgrounds could become unstable and unsafe, due to the condition of very recently discovered chalk mine tunnels below.

The professional advice provided to us and the joint view of the Council and the school is that immediate closure of the site is prudent, reasonable and proportionate.
Pupils will not return to the site until further notice. The Council is locating appropriate educational settings elsewhere in Harrow, where Nursery to Year 5 classes will relocate in time for the start of the Summer Term. Year 6 classes will relocate to Whitefriars School and resume on Monday 27 March. For details of current plans for the relocation of classes and transport of pupils, see the accompanying letter from head teacher Deb Spruce.

For a summary of the findings leading to today’s decision, and the next steps for making the school site safe, please see overleaf.

The Council would like to invite parents and carers to one of three briefing and information evenings where you can find out more details and discuss our next steps. They are:
Today, Thursday 23 March, 6pm-7.30pm at West Lodge School Hall, Pinner
Today, Thursday 23 March, 8pm-9.30pm at West Lodge School Hall, Pinner
Tomorrow, Friday 24 March, 5pm-6.30pm at West Lodge School Hall, Pinner

We would like to stress that the imminent risk to the school buildings is believed to be small. The structure of the buildings is not showing any areas of concern. Regular full assessment and inspections by structural engineers have found no anomalies.

With the evidence to hand, we are certain that this is the right decision. The Council would never ask or permit any school to operate when there is a known risk, however small, to the safety of the site or the staff and children within it.

We acknowledge that closing the school site will cause huge disruption to the lives and schooling of local people, and we apologise for the great inconvenience this decision will inevitably cause.

Yours sincerely

Michael Lockwood


A summary of the findings leading to today’s decision and next steps
During the summer holidays of 2015, a hole unexpectedly opened up in the tarmac of the staff car park at Pinner Wood School. The hole was roughly 3 metres wide and 1 metre deep.
The Council and school made the area safe and commissioned specialist geotechnical engineers, structural engineers, environmental engineers, surveyors, geophysicists and health and safety professionals to analyse the causes of the hole. They determined that the hole was situated on top of an old, disused shaft. The material used historically to backfill that shaft, they concluded, had only been loosely compacted and had subsided – creating a hole.

In the light of that discovery, we undertook to continue our investigations to make certain of the condition of the ground under and all around Pinner Wood School.

Over the past 21 months, extensive studies including probing and drilling had given no reason to believe there is any risk to the stability or safety of the school’s buildings or the site.

Our latest surveys, however, deploying the most modern laser-imaging techniques and deployed from targeted boreholes, have in recent days revealed previously unknown and uncharted chalk mines beneath the school estate, located roughly 20 metres below the surface. Some of these mine tunnels stretch directly underneath the school’s main buildings.

Furthermore, our latest surveys indicate that at least two of the tunnels underneath the school have partial roof collapses. There is also evidence that spoil (largely made up of clay and sand) has fallen from above, into the voids below. It is not known when these collapses occurred.

The professional advice provided to us is that these roof collapses are likely to migrate through the ground and open up new surface holes under or near the school at some point in the future. This could put staff and children at risk or even compromise the structure of the school building.

Furthermore, our work, though extensive, is not exhaustive. It now appears likely from the information we have that there may be further as-yet-undiscovered tunnels, collapses and shafts in other parts of the school estate.

As a result of the professional advice provided to us, the joint view of the Council and the school is that immediate closure of the site is prudent, reasonable and proportionate.

More extensive testing of the ground throughout the site is now essential, to assess the site’s condition and safety. Such a survey is an extremely intrusive process involving rigs, drills and probes and is likely to take months, once the site is vacated.

Our hope and expectation is that, following that comprehensive survey, we will be able to stabilise the ground and return the site to a safe condition – probably by pumping a quantity of material underground to fill the mines themselves. The school would then, subject to a full structural assessment, be able to return to its current site and buildings.

It may, however, be the case that it is not economically feasible to restore the ground and that the school may never reopen in its current form on its current site.

All our investigations have been limited to the school site and although the full extent of the workings are yet to be determined, currently we know of no reason to suggest that the tunnels we have discovered to date stretch under neighbouring properties.