May 11 2017

Pinner Wood School – Progress Report, May 10, 2017

Dear resident,

This is the third of our regular updates on the work that our project team are undertaking at the site of Pinner Wood School. The site is currently closed after the discovery of previously unmapped chalk mine tunnels under the school building, some of which had collapsed roofs. We are currently drilling boreholes right across the site, in order to get the best possible grasp of what we might be dealing with underground. As we set out in previous updates, our first priority is to survey the school field, the courtyard and the tunnels we already know about.

The school playing field has now been surveyed in full according to the grid pattern set out. As you will see from the chart overleaf, the rigs have found indications of broken ground or voids at
depth in seven locations, along with numerous soft patches under the field. This map will now give us strong indications of the best locations to deploy the laser scanner – which we expect to bring back once all our boreholes are drilled across the site, perhaps as early as next month.

At this preliminary stage, our findings should not be interpreted as showing further chalk mine tunnels below ground. However, it is clear that significant further investigations are necessary on the playing field to determine its condition. As a result, it will not be possible to pursue the option of using the playing field as a “pop-up” site for any temporary school buildings for Pinner Wood pupils from September 2017. A decision on a temporary site for the school will be made before the end of May, so works can commence on the temporary accommodation in June.

Our first rig is now tracing its way around the southern and western edges of the school buildings, and so far has discovered no evidence of voids or broken ground. There have been a few instances of soft ground. Once its circuit is complete, it will make its way to start drilling in the playground on the west side of the school.

Our second rig is surveying the car park on the east side of the school, and has discovered further voids and broken ground consistent with the tunnels we already know about. It has also indicated some voids/broken ground at the north-eastern side of the building, opposite those discovered a month ago. Once that area is surveyed, it will further explore the areas around the known mine workings at the south-east of the site.

Our third rig has stopped drilling new boreholes, and instead has begun completing installations in selected borehole locations, which will accommodate the laser scanner when it arrives. By contrast, the courtyard mini-rig continues to make slow progress on its journey around the courtyard. After its earlier mechanical issue, this week it struggled to recover its rods from a borehole. Following that delay, it will continue its work around the courtyard this week.

By the time of our next bulletin, due on Wednesday 24th May, we are likely to have made a decision about a temporary location for Pinner Wood’s pupils and also have a clearer idea of when the laser scanner will arrive, and what it will scan, to move our investigation forwards.

Findings north of the school in the playing fields as of 10 May:

Findings in the south east corner of the school, near the entrance, as of 10 May:


  • Green Circle: Borehole with no evidence of voids
  • Yellow Circle: Borehole with evidence of soft ground
  • Red Circle: Borehole with evidence of void or significant broken ground
  • Blue Dot: Planned future Borehole
  • Red Hash: Tunnels discovered by March laser surveys
  • Grey Area: School buildings
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  1. Sunny

    Let’s hope for some good news in the next two weeks from Harrow Council for the staff, students and parents impacted by the closure of Pinner Wood School.

  2. peter day

    At long last our M.P has made an appearance, after a year of investigation he has not been near, of course he is now coming around to ask us if we have any problems with how the council is handling it all, how nice of him to have us all now in his thoughts. Could it be something to do with the up and coming General Election oh of course not, I would have thought that when the mines were discovered (a year ago ) he would have taken an interest his flock but then again the council is a red one.

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