Today, some valley fills measure more than 100 million cubic yards, and bury two miles or more of a stream.
Overall, Fish and Wildlife found nearly 900 miles of streams buried by valley fills.
That's almost as long as the Ohio River, which winds 981 miles from the junction of the Allegheny and Monongahela rivers in Pittsburgh to where it meets the Mississippi at Cairo, Ill. It's also equal to three trips back and forth from Charleston to Morgantown for a Mountaineer football game.
In West Virginia, Fish and Wildlife scientists found at least 470 miles of streams buried or permitted to be buried by valley fills since 1986. Refuse fills accounted for 123.5 miles of that total; overburden fills made up nearly 346 miles.
The West Virginia portion of the study, however, included only mining permits issued out of the Division of Environmental Protection's Logan regional office. That office covers the coal-producing counties of Logan, Lincoln, Boone, Wayne and Mingo.
Valley fills are also burying streams in other DEP regions, especially the Oak Hill region, which includes part of the Kanawha River watershed.
The report concludes that the Mud River watershed illustrates the intensity of valley filling that can occur in single watersheds.
The Mud drains about 250 square miles. Within the upper 23-square-mile reach of the drainage, about 29 percent of the streams have been filled or approved for filling. Within the 16.5-square-mile portion of the Mud upstream, and including Connelly Branch, 39 percent of the streams have been filled or approved for filling.
Numerous fish and wildlife that are federally listed as endangered or troubled species live in the watersheds affected by mountaintop removal, the study says.
"West Virginia has also been identified as one of the largest areas of contiguous forest in the Northeast, as a core area for many of the southern-affinity species of neotropical migrant birds, and is considered a 'hot spot' for bird species of high concern in the Northeast United States," it said.
"Consequently, the loss of these streams and their associated forests may have ecosystem-wide implications."
The report also takes issue with the coal industry and state regulator view that filling in smaller streams - those with a drainage area less than 250 acres - doesn't do as much environmental damage.
Fish and Wildlife officials surveyed Pigeonroost Branch in Logan County, the potential site of a new mountaintop removal valley fill. They found that, though it drains less than 110 acres, it supports aquatic life that needs flowing waters for a continuous period of six months to survive.
The report concludes that the loss of smaller, headwaters streams and their surrounding forests to valley fills "may have ecosystem implications, particularly when considered together with other mining-related impacts in the Appalachian coalfields region.
"Moreover, the quantity and quality of water in a large stream system is a function of the watershed in which it originates," it said. "Productivity in small streams may be economically insignificant; however these streams are the basis for downstream water quality, hydrologic patterns and biological production."