The area then appeared stable until July 2021, when there was a further minor collapse. Ground investigations proved there was a 3.5 metre diameter shaft, which had been plugged with concrete between 4.5 metres and 6 metres below ground level by the National Coal Board in the 1970s   Safety works have been completed by the Mining Remediation Authority to protect residents in Arley Lane, Wigan, from ground collapses caused...