Total US coal production decreased about 15% from 2008 to 2014.

Surface production fell about 21%, and mountaintop removal, one type of surface production, decreased 62% over this period.

The EIA said lower demand for US coal, primarily used to generate electric power – driven by competitive natural gas prices, increasing use of renewable generation, flat electricity demand, and environmental regulations – contributed to lower US coal production.

The EIA’s total US coal production figures include both surface and underground mining activity, while types of surface mining techniques include contour strip, area, open pit, and mountaintop removal.

In mountaintop removal, entire coal seams running through the upper portion of a mountain are mined by removing all of the overburden, the rock or soil overlying the coal, creating a level plateau or gently rolling contour. This type of mining is sometimes considered a variation of contour mining.

A permit must be granted to conduct MTR operations and the EIA said that by identifying the mines with MTR permits it was possible to estimate MTR production using mine production data.

“However, quantifying the amount of coal produced from mountaintop mining is difficult, because there are a variety of mining techniques that can be performed on a mountaintop in addition to mountaintop removal,” the EIA added in analysis published on Tuesday.

“These techniques include contour mining, where coal is mined on a hillside, and area mining, where coal is mined from relatively flat terrain.

“Some of these non-MTR methods may be used in conjunction with or following the use of MTR, making attribution of coal production by mining method less obvious.

“Consequently, production data in this article refer to total surface production at mines with MTR permits and provide an upper bound of MTR production.”

MTR is prevalent mostly in Central Appalachia, specifically West Virginia, Kentucky, Virginia, and, in the past, Tennessee.

In 2013, Tennessee legislators proposed bills banning permits for specific coal mining operations more than 2000 feet above sea level.

While Tennessee has yet to pass legislation definitively banning MTR operations, the EIA reported there had been no active MTR permits in Tennessee since at least 2007.

West Virginia accounts for most domestic MTR production, and MTR production makes up most of the surface production in the state – 61% in 2013.

If the mining operation includes a valley fill, which allows the overburden to be deposited in intermittent or perennial streams, an additional permit must be granted.

On May 27 the US Environmental Protection Agency and the US Army finalised the controversial Clean Water Rule that more precisely defined waters protected under the Clean Water Act.

The Office of Surface Mining Reclamation and Enforcement is also working with EPA and the US Army Corps of Engineers to develop an environmental impact statement analysing environmental impacts of coal surface mining in the Appalachian region.

OSMRE expects to release an EIS along with a proposed stream protection rule this US summer.