The expansion of the 6.5 billion-gallon Alpha Natural Resources Brushy Fork impoundment in West Virginia was approved by the Mine Safety and Health Administration this week.
The impoundment will be permitted to hold as much as 8.5 billion gallons and, when fully expanded, will reach a height of 740 feet, higher than the Hoover Dam.
Alpha calls MSHA’s approval an incremental development in what has long been part of the construction plan, according to the Associated Press.
The impoundment was built in the 1990s by Marfork Coal Co., which was a subsidiary of Massey Energy before Alpha bought Massey in 2011.
The expansion is not without opposition, with environmental groups and local residents claiming that the impoundment was unsafely built and it is only a matter of time before it fails.
But Alpha says past state and federal reviews found no deficiencies and that the company is “committed to designing, building and operating facilities safely.”
“We make the safety of our impoundments among the highest priorities in our company because we recognize the responsibility that comes with impoundment ownership,” an Alpha spokeswoman told the AP.
“If safety is ever in doubt, we won’t hesitate to stop working and shut down a mining operation.”
The West Virginia Department of Environmental Protection previously ruled there was no reason to believe the impoundment was improperly built or unsafe.
The department is still reviewing Alpha’s expansion application but required MSHA approval before it could act on any decision.