A copy of the study’s synopsis was obtained by the The Washington Post, which reports that of 73 tests conducted on slurry walls around seven sites in West Virginia, only 16 met the required standard.

The Department of the Interior mining agency ordered the 2011 study, which is in draft form and has not been publicly released.

According to the study’s synopsis, the department’s engineers noticed companies were using coarse refuse that would not stay compacted except “within a narrow range” of moisture conditions.

It added these conditions were not monitored and bulldozers were used to compact the soil, a task for which they are poorly suited.

OSM spokesman Chris Holmes told The Washington Post that it was examining a “potential issue” with compaction of dams but that it had “not found any indication that any coal slurry impoundment is in imminent danger of failure”

“Had it done so, OSM would have taken action immediately,” he said.

Coal slurry impoundments can pose a serious threat to mine workers, communities and the environment when at risk of collapsing.

Last December, 58-year-old Markel Koon was working at the Nolan’s Run slurry impoundment at Consol Energy’s Robison Run preparation plant in Harrison County when an upstream slope failure occurred.

The victim, a 37-year mining veteran, had been grading the upstream slope of the pond on November 30 when the tragedy occurred.

The bulldozer was carried into the pool area during the slide and sank with the victim on board.

After several days of rescue efforts, Koon’s body was recovered.

Another slurry spill, into the Tug Fork of the Big Sandy River in October 2000, has been called the worst inland environmental disaster in American history.

The Martin County Slurry Spill contaminated the water supply of more than a dozen communities and killed aquatic life in local waterways.

According to Mine Safety and Health Administration data, there are 596 coal slurries across the country and 114 of those are in West Virginia.