Apr 28 2017

Pinner Wood School – Progress Report, April 26, 2017

Dear resident,

This is the second 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 last week, our priority has been to survey the school field, the courtyard and the tunnels we already know about.

Two of the rigs have focused exclusively on the school playing field and they are almost finished there. As you will see from the chart, the rigs have found numerous soft patches under the field and a small number of boreholes indicated broken ground or voids at depth. We would like to stress that there a great many reasons for a “yellow circle” reading of soft ground, and that even the “red circle” readings of potential voids underground should not be interpreted as showing further chalk mine tunnels below ground.

We will be receiving further expert interpretations of the findings in the coming weeks, but until we deploy the laser scanner, it will be very difficult to make specific inferences about the further extent of underground works on the site. We expect to bring back the (very expensive) laser scanner once all our boreholes are drilled – perhaps in early June.

Once the playing field has been fully drilled, one rig will move to the field west of the school, while the other will move to the car park east of the school. Progress will probably slow slightly at that point, as it is harder to drill through tarmac than in an open field.

The courtyard mini-rig has made slower progress due to a mechanical issue which has now been resolved. It has discovered no further issues underground so far.

The final rig has moved to investigate the area around the tunnels that we already know about. As you will see from the chart, it is has discovered further indicated voids or significant broken ground in the area that may prove consistent with existing tunnel finds. Boreholes under the school building were made by drilling diagonally from outside the walls – we have not entered the building or drilled down through floors. Again, until the laser scanner is deployed, it will be very difficult to get a full picture of what is happening underground.


We are also now considering participating in a pioneering satellite-imaging program on the site, which draws on more than 20 years of historical imaging data from the European Space Agency. It would help us measure any slight movements in ground level in the past and in coming weeks, which will in turn help us interpret and analyse the results of our ground surveys. We are also drawing closer to a decision about where to site Pinner Wood School temporarily from September 2017. The current dual-site solution in Wealdstone will come to an end and we
are looking for a single site close to Pinner Wood that can host the whole school. We are currently evaluating more than 20 potential options. We must make a decision on this by the end of May and we hope to have much more information about our progress on this issue in our next bulletin, due on Wednesday 10th May.

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

    I can’t really see red and pink in this view.

    1. Someonewhocares

      LB: It is marginally better/larger on the original:


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