Production in the mine was idled on Thursday last week while a recently sealed area was being monitored, allowing new 120 pound per square inch seals to cure to full strength. The curing is expected to be reached by October 6.
The seals protect active areas of the mine in the event of an explosion or other event in sealed areas of the mine.
The area in the Buchanan mine being sealed was the same part where a roof fall resulted in the mine being idled for nearly nine months last year.
Idling of the mine is mandatory under federal safety requirements from the Mine Safety and Health Administration regarding the sealing of mined-out areas.
No production is permitted by MSHA and the mine is being ventilated and regularly inspected by Consol.
The company has requested MSHA holds an expedited hearing on the matter.
The last of 89 seals in the mine were completed on September 15, and will take several weeks to reach their maximum strength.
Of the 89 seals installed, 81 were at or exceeded the current 120psi standard for strength.
Once all seals in the area reach their rated strength all provisions of the new seal regulations will have been met and production is expected to resume, the company said.
Consol issued force majeure letters to its customers with coal delivery contracts from the mine. Once production resumes, force majeure will be lifted.
The new seals were made from a specialised concrete material, which meets the highest strength standard required by federal regulation.
Last week the US coal producer cut its production guidance for the third quarter, citing roof falls and longwall delays.
The coal giant downgraded its production guidance from 16.4-18.4 million tons for the quarter to around 15Mt.
The Buchanan mine produces about 14,300t a day of low-volatile metallurgical grade coal.
Consol has 17 bituminous coal mines across the US and its annual revenue is $US3.8 billion.