 During 2012 there was some concern from some residents of a possible mine subsidence risk in Ohai, due to several old mining tunnels under the Northern part of the township dating from pre-World War II, the old Wairaki 3 mine works.In July, a man had called the council claiming his drainage system was affected by subsidence, but an engineer had concluded it was not the case.Solid Energy had told the council the risk of subsidence from the old Wairaki 3 mine works, which lie under the northern side of the township, was "very minimal", he said, since subsidence normally occurred in the first few years, but they would continue working together to examine it.