Magazine article American Forests

A Solution to Mine Drainage?

Magazine article American Forests

A Solution to Mine Drainage?

Article excerpt

When the U.S. Forest Service acquired land for the 607,000-acre Daniel Boone National Forest in Kentucky, a multitude of water-quality problems came with the deed.

Located in the mineral-rich foothills of the Cumberland Mountains, much of the land that now comprises the Daniel Boone has been mined for coal over the last 100 years. Once the rich seams of high-sulfur-content coal were depleted, however, owners simply walked away, leaving many of the abandoned mines to pollute nearby watersheds for decades to come. Although the mine abandonment occurred in the era prior to enactment of state or federal reclamation laws, little has been done until recently to fix the tremendous environmental damage.

In the southern tip of the national forest along the Kentucky-Tennessee border, portions of Rock Creek have suffered particularly heavy damage from acid mine drainage (AMD). Several abandoned mines have been pouring contaminated water into the watershed of this state-designated wild river for as long as 50 years. But this is not unusual--it is estimated that between 1 and 2 percent, or 10,000 to 20,000 acre-feet, of all water originating on the forest is contaminated by AMD.

Officials of the Daniel Boone, charged with improving the forest's water quality, working with the U.S. Forest Service's Berea Research Center in Kentucky, decided in the mid-1980s to pursue a relatively new technology that uses manmade wetlands to treat AMD-tainted water. Following the old adage that a drop of tainted water is cleansed once it flows over several stones, the new method for purging waterways of AMD consists of using swamplike conditions as a filter. It's not that simple, of course, but that's the basic idea.

Historically, the principal methods for treating acid mine drainage have been to seal the portals of unused mines or to add lime (an alkali) to help neutralize the acid in the discharge. In both instances, however, adequate treatment can be costly. In fact, Robert Kleinman, a research supervisor for the U.S. Bureau of Mines, has estimated that the nationwide cost to the mining industry for chemical treatment of AMD alone is $1 million per day. Sealing mine portals (usually with concrete) is not only expensive but often the water inside usually finds another way out.

In the spring of 1988, the U.S. Forest Service, searching for ways to solve the AMD pollution problem affordably, constructed its first manmade wetland for the purpose of treating AMD. The facility was created near the opening of the worst-polluting mine along Jones Branch in the Rock Creek watershed. Funding for the $161,000 project ($75,000 for the wetland and $86,000 for roads) was generated jointly by the U.S. Forest Service, the Kentucky Division of Abandoned Mines, and the U.S. Office of Surface Mining. Howard Halverson, a research scientist from the Berea Research Station who is an expert on this treatment method, was named project leader.

The Rock Creek wetland, as the project is called, consists of two shallow ponds that have a total surface area of 11,000 square feet. In this case, two ponds were required because there wasn't enough level land near the mine for a single facility (the wetland's size is determined by the amount of flow from the mine).

The ponds were built by leveling the floor of the two existing depressions, which are about three feet deep. The flat, compacted floor was treated with bentonitic clay to minimize see page, and then a layer of crushed limestone was placed on top. An additional 18-inch layer of mushroom compost was added to allow the growth of cattails and other aquatic vegetation vital to the cleansing process. …

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