The Summer drought of 2022. W is a wet week. D is a dry week. The green line is when the adit collapsed. The lowest level seen so far at 7.20m. The main drainage adit would clear at roof level around 8m ( maybe this year ? )
The initial part of the adit was cut and cover the latter part of which had collapsed way prior to 1950. The adit then entered a fairly stable area of hard marl which you see here as uncovered by the digger nealy seven metres down. This could be followed some 50 metres to a capped ventilation shaft following which Triassic Sandstone was encountered which after another ten metres the water issued from a roof collapse. About five cubic metres of rocks and gravel were removed from here followed by ominous rumblings. The five cubic metres removed translated to a surface collapse of the same volume bringing a speedy halt to the adit choke excavation without gaining any forward progress. It seems likely that the cut and cover restoration has helped with the outflow but any more progress upstream is unlikely nay impssible.