Well that is the full set of 8 holes done, all at 37-38m or so, and they all hit 'voids' (meaning abrupt loss of return water) at 32-39m. In all cases they hit harder rock-like material first, which returned fragments of what looked like creamy-white limestone. After this the drillers went on a few metres using a fire hydrant as a water supply to allow for no returning water! For these last few metres drilling was mostly clay-like in terms of resistance to drill, with intermittent rock-like resistance. The void holes if any were not so apparent except insofar as the drilling water flowed away at a considerable rate.
Anyway we have enough pipe in the ground and they have 'grouted' it with some sort of sloppy 'bentonite' material that apparently semi-hardens.
The drillers (Geocore) were as good as their word in terms of leaving the site clean and tidy - the plastic sheet is very effective at containing the mess. And they were polite and sensible always.
Slight glitches (apart from the voids!) were the eventual need for 3 skips (some extra cost), partly to clear the drive for the intermediate weekend and partly because the 2nd skip got full of unwanted pump water. This caused some fun for the skip driver when he later stopped quickly and covered his lorry in clayey water!
But basically OK so far. The picture is a fisheye, and boards cover pipes cut off a bit lower to allow drive usage. We expect the builder late next week to start cutting trenches and connecting the ground loop up, using a new manhole. The pipes and bits (but not the insulation needed) were supplied by the heat pump supplier and seem all here.
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