Remediating Acid Mine Drainage: History and Techniques in Appalachia

Two waterways meet in a surreal junction at Vale Summit, a small low streambed in the Appalachian forests of Maryland, surrounded by high sandy banks and the faint sound of passing traffic.

Bright orange coal mine drainage from the Hoffman tunnel washes iron oxides and sulfates over rocks and tree limbs and completely distorts the little brown flow of Braddock Run, a smaller, slower but rich stream, providing a home to benthic invertebrates and young fish that the drainage cannot.

Braddock Run exhibits all the attributes of a healthy stream: neutral pH, low iron levels and a diverse scatter of mayfly, stonefly and caddisfly larvae. The rushing waters from the Hoffman tunnel are unable to support any benthic life aside from persistent species of algae.

This is the legacy left by coal mining from over a century ago, and one of many such examples of acid mine drainage (AMD) in Western Maryland.

The Hoffman drainage tunnel was built in the early 1900's when Consolidated Coal built a shaft to drain the deep mines, pumping the excess into Georges Creek. Back in the 1930's, the water was dangerously acidic, hovering around the pH of strong hydrochloric or sulfuric acid.

Despite the neon orange appearance of the drainage, the waters downstream from Hoffman Braddock Run support a healthy brook trout population. However, this is not the case for most waterways affected by AMD; they often require remediation to halt the movement of contaminants downstream. Hoffman is affected because legislation regulating AMD and coal mining in general were virtually nonexistent when the problem began.

I wanted to take some of the information I've gained while living in the area about AMD and some of the more interesting ways scientists are remediating the damage in recent years. I even had the pleasure of speaking with Geologist Barry Maynard from the University of Cincinnati, who shared some information on creating wetlands to remediate the damage of AMD. It's all a bit Maryland-focused, and I eventually want to get some more information about Georgia and its history with coal and AMD.

Coal mining has a long history in Western Maryland. It began in the early nineteenth century with underground mining, men digging by shovel and candlelight, transporting coal in horse drawn carts. Technology improved over the next century, and subsequently coal production peaked around 1910, in support of burgeoning industry and the First World War. In 1977, federal legislation was passed addressing abandoned mines, as the aftereffects of pre-law mining practices were becoming a public safety issue. The federal standards required mining companies to reclaim the land by covering the mined area with soils and rocks, and planting grasses trees and shrubs. Those standards were accepted in Maryland in 1982.

AMD, however, wasn't specifically addressed until 1992. Water was lumped in with other environmental problems and given a lower priority. Only then was AMD given direct funding to apply to the techniques and technology used to clean up the mess.

The cheapest and easiest way to clean up AMD in a waterway is by using a "doser"; giant silos filled with limestone set up to dose the affected stream at set intervals, raising the alkalinity. Using the doser for treatment leaves an uninhabitable stretch of the waterway just downstream where the lime or limestone mixes chemically with the acid mine drainage and prevents full recovery of the living resources until the chemical dissolves at some point downstream. Beyond this "dead zone" or "mixing zone" however, the waters are much improved, and able to support life.

Passive systems like the Successive Alkalinity Producing System (SAPS) are less invasive. These systems filter AMD through successive layers of microbe rich soil and limestone to precipitate metals and cut the acidity, creating a more healthy stream downstream. The SAPS are expensive, costing about $150,000 to $200,000 to construct. Some streams need more than one system and require frequent maintenance, an expense that the federal government has been historically hesitant to fund.

University of Cincinnati Geologist Barry Maynard, a leading researcher in AMD remediation in the Appalachians, points out another problem with the SAPS.

"[M]ost suffer from clogging," he says. "That is, minerals precipitate out of the mine drainage and fill the pore spaces in the drains."

Maynard has studied the detoxification capacity of natural wetlands and found that by building an artificial wetland or strengthening an existing one in an AMD affected area, sulfates and other minerals can be converted into less harmful substances by the natural population microbes within the wetland.

But how to build a wetland?

"It's actually pretty easy," says Maynard. "Some drainages have naturally low wet spots that can be augmented by building a series of small embankments. All that this requires is a backhoe or a bulldozer and is relatively inexpensive."

The whole system is much less expensive than chemical remediation, according to Maynard, and can be used in conjunction with passive systems like SAPS for a greater effect.

In fact, that's what most states end up using, but in certain areas that need remediation, especially mountainous regions like Western Maryland, it's much more difficult terrain to work with.

It's amazing to me how these companies were able to ignore--both politically and ethically--the damage they were doing to these streams. AMD is not like global warming where it is not immediately apparent; it's in your face and obviously unhealthy.

More to come on the subject in the future. I need to find some good books about Appalachia and its coal history.