What Lies Beneath

Digging boreholes for straw bale build at Holy Trinity Tulse Hill


  1. Dando Terrier rig arrives on site. They will be digging 3 or 4 boreholes today, in different parts of the site, and going down to 6m.
  2. This is the first metre's sample. You can see some brick or ceramic in the mix, and there was also a small amount of root material.
  3. These things mixed in with the clay are because this is "made-up" ground, containing elements of the old hall, demolished in 1984.
  4. The rig works by screwing on extra one-metre shafts each time. The bottom shaft is hollow and contains a plastic sleeve. When it comes up, they pull the plastic sleeve out of the shaft, and peel it away from the soil sample.
  5. Here is the second metre. It looks a different colour, but it's not because it's sandy land. This is solid London clay - no elements of the made-up ground here, which is good. When they dug the second borehole, where the sycamore trees were, there was root material in the second metre also - unsurprising, since sycamores have fairly deep roots.
  6. Metres 2, 3, and 4 - all seem to be solid clay to me, but the engineer takes several samples of each bit away.
  7. Digging deeper. To get the shaft in and out, each metre has to be unscrewed by hand every time.
  8. The fifth metre out was wet. It seems we might have found a natural water level - but maybe not. A closer examination will reveal more. At the end of the dig, they insert a stand pipe in the hole, then they come back a couple of times to measure the water level.
  9. Here are metres 1-6. (No.1 is in the background). You can see how the engineer has taken them apart. The sixth metre also looked wet at one end, but when the engineer looked inside the sample, it was dry and solid. Most likely there was a pool of water underground which got disturbed by the drilling and simply covered the outside of part of the sample. Good news for us!
  10. Now here's a question - do I secretly hope we'll find oil? That would solve our finances, but we might not get the hall built for a while!