Report highlights Grosvenor failings in lead-up to blast
The Moranbah operation produced coal at a rate that consistently exceeded the capacity of gas drainage measures at the longwall panel involved, the Queensland Coal Mining Board of Inquiry report tabled in State Parliament this week stated.
The inquiry also found that the Queensland Mines Inspectorate did not have complete information about the conditions under which mining operations were being conducted at that longwall.
Even allowing for that, the Inspectorate did not give longwall 104 the attention it warranted, it found.
The latest and final report from the inquiry sets out the Board’s findings and recommendations regarding the serious accident that occurred at Anglo American’s Grosvenor mine on May 6, 2020, and 27 methane exceedance high potential incidents in the lead-up to that event.
The inquiry found Grosvenor mine management failed to take timely and meaningful action to control the hazard posed by methane in the lead-up to the explosion that seriously injured five men.
In its own investigations of incidents leading up to the explosion, the operation found that its gas drainage system had repeatedly failed because its design capacity could not sustain the mine’s production rate.
It was caught short, not having sufficient post-drainage capacity for its targeted rate of production, the inquiry found.
Additional infrastructure to improve goaf drainage capacity was on order, but not due until June 2020.
“Despite the emergence of high gas emissions, beyond gas drainage system capacity, no adjustment to production was made. No limit was imposed on weekly or daily production,” the report found.
High gas emission rates, absence of pre-drainage or other form of diversion of gas from surrounding seams, and a goaf drainage system whose efficiency did not match the rate of production pursued made LW 104 susceptible to methane exceedances.
The report noted that Anglo American metallurgical coal chief executive Tyler Mitchelson gave evidence that his expectation was that senior management would reduce production rates at Grosvenor where necessary, so as not to exceed the capacity of its gas drainage system.
“Contrary to Mr Mitchelson’s declared expectation, this did not occur.”
Between May 1 and 3 last year, emails exchanged between the Site Senior Executive (SSE) and senior mine leadership indicated a view that gas emissions at LW 104 had reached a critical point, and were regarded as ‘almost to the point of bordering on being unmanageable’, the inquiry report stated.
The report found the probable ignition source for the May 6 blast was the heating of coal initiated by polyurethane resin used to consolidate the face and roof at longwall 104.
The mine’s risk assessment for the change from Minova PUR to a DSI product did not address spontaneous combustion risk and concluded that there was no significant difference between the two products, it found.