CHARLESTON, W.Va. -- Federal regulators on Tuesday stepped up enforcement action against another West Virginia coal mine for what they said was a pattern of serious safety violations.The U.S. Mine Safety and Health Administration issued a "pattern of violations" notice for Coal River Mining LLC for what MSHA said were repeated safety problems at the company's Fork Creek No. 1 Mine in Lincoln County.In a press release, MSHA said that an agency audit revealed that Coal River Mining had failed to report miner injuries equivalent to 239 days of lost time during a one-year review period that ended on Aug. 31.MSHA also said that it had cited 158 "significant and substantial" violations at Fork Creek No. 1 from September 2012 to August 2013. Those included 14 violations for roof and rib hazards, 21 for ventilation hazards, and 21 for explosion hazards.Fork Creek's rate of serious violations was nearly nine per 100 inspection hours during the review period, compared to just less than four per 100 inspection hours for all underground coal mines."While it took an MSHA audit to discover the extent of unreported injuries at the mine, Coal River was also aware of the compliance issues it was experiencing and did not take sufficient action to make necessary safety improvements," said MSHA chief Joe Main. Coal River Mining officials declined to comment on the MSHA action.The pattern of violations notice at Fork Creek is the latest in MSHA's renewed effort to make use of stepped-up enforcement tools to compel mine operators to improve safety performance.Last month, MSHA issued similar notices to three coal mines, for the first time using a new pattern of violations rule written in the wake of the 2010 Upper Big Branch Mine Disaster.The new rule eliminates a preliminary warning letter for operators. It also allows MSHA to count citations and orders toward a mine's violation history even if those enforcement actions remain under appeal by the company.Congress gave MSHA the pattern of violations, or POV, authority in 1977, after finding that repeated citations by inspectors weren't enough to prevent a series of explosions that killed 23 miners and three inspectors at the Scotia Mine in Kentucky in March 1976.Under the POV program, mines with a history of safety problems are kicked into a tougher enforcement bracket. Each time an additional serious citation is issued, that part of the mine is closed. Mines can have the pattern-of-violations designation lifted only if they go an entire quarterly inspection without a serious violation.But MSHA for years delayed in writing rules to implement the POV program. When it did write rules, critics say they had far too many loopholes. And screening of mine operators to look for repeat violators was sporadic.The National Mining Association and other industry groups are challenging the new MSHA POV rule through a lawsuit filed in the 6th U.S. Circuit Court of Appeals.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.