ACID MINE DRAINAGE - Everyone’s Problem

One of the most visible problems left behind by pre-regulatory mining is Acid Mine Drainage (AMD).  The term AMD might be unfamiliar, but any time you see a stream flowing with orange water or lined with an orange scum, that is evidence that the stream is polluted with AMD.

Found mainly in regions where mining has taken place but mining activity has ceased, AMD is a pollutant that if not treated can render any stream unable to support aquatic or plant life. Pyrite (iron disulfide) is the main ingredient of AMD and is an acid-generating rock mineral.  It is frequently found in underground mine workings or mountains of coal waste material, called culm.

AMD is typically produced when groundwater comes into contact with rocks that contain acid-bearing minerals, like pyrite.  Such rocks are especially commonplace in mining regions.  Typically, mine water contaminated with pyrite reaches the surface through abandoned mine shafts or other underground openings. Water that comes into contact with pyrite becomes contaminated with iron and sulfur.  Once at the surface, the metals in the contaminated water undergo a chemical change, becoming “heavy” and drop out of the water, or more exactly, drop to the bottom of the stream bed. When it reaches the surface, AMD develops an orange or yellowish-orange color and smells like rotten eggs.  The orange color is created when oxygen interacts with the dissolved iron.  The bad smell is caused by the sulfur compounds.

Culm banks and mine-scarred sites may look inactive and harmless, but they are actually a constant source of pollution and contribute to the AMD problem. Each time it rains or snows, water seeps through, and rolls off these areas carrying metals and other contaminants contained in this coal waste into the ground and nearby waterways.

In Pennsylvania alone, an estimated 5,000 miles of waterways are AMD-impacted.¹  A large percentage of those damaged creeks, streams, and rivers are in the minefields of Northeastern Pennsylvania.  The prevalence of the AMD problem there is a direct result of the extensive anthracite mining that occurred between the mid-1800s through the mid-1900s.

While the mines were operating, water that seeped into the mine voids was pumped back to the surface.  However, pumping ended when the mines closed in the 1950s and 1960s.  The mine voids soon filled with water, and vast underground pools of contaminated mine water developed.  Those pools, which exist today, are not stagnant. Water enters from the surface, flows through the underground voids, and reappears in various other locations.

Perhaps the largest source of AMD pollution into waterways is through boreholes, which are vertical shafts drilled into the ground to relieve water pressure built up within the mine pools. In some cases, the mine pool actually began to flood the basements of homes and other structures.  While the boreholes successfully relieved the flooding, their flow is often directed into nearby streams, creeks and rivers. While solving the flooding problem, this “solution” caused many major waterways to be degraded by AMD.

Aside from contamination caused by AMD, mining has affected the flow and structure of otherwise clean streams in Northeastern Pennsylvania.  When streams pass into areas that have been mined, they enter zones where the bedrock has been broken.  The original streambed may also be blocked by deposited culm material.

The result is that the water in the stream seeps downward into underlying rock layers, entering the mine pool. Because of that loss, the original channel remains dry, except during periods of heavy rain or snowmelt.

What AMD Does to Our Waterways

Acid mine drainage that enters streams and creeks damages those systems in several ways. The most visible effect is that it turns everything in its path orange, including rocks, trees, plants, and even wildlife that frequent affected sites.

However, there are more harmful and damaging effects, which vary depending on the size of the stream and the total amount of pollution that enters the water.

AMD damages aquatic ecosystems and reduces water uses in affected watersheds.  Plants and algae, which form the critical energy link for aquatic systems, cannot photosynthesize well when AMD concentrations are high.  Aquatic insects cannot live in AMD-impacted streams because the slimy thick iron deposits create an unsuitable substrate or “home” in which the insects can move and burrow.

The iron or aluminum particles clog their delicate gill structures, preventing the insects from getting enough oxygen. Because aquatic insects are normally important food items for fish, amphibians, and reptiles, those creatures then also find it difficult to live in streams that contain AMD.  Thus, AMD impacted streams are often biologically dead.

Pollution to Solution

Although the problem wasn’t created by the current generation, the AMD problem in Northeastern Pennsylvania is one that must be dealt with by those living here now.

The first important step is awareness.  Often, people living in AMD-impacted areas are so accustomed to seeing the orange water that they begin to ignore it.  Some people believe that no remedies are possible, or that cleaning up affected areas may take too much time or cost too much money. Everyone living in an area with AMD must be made aware of its presence and the damage it causes.  The second step is action.  Residents must get involved in solving the problem. After all, a clean, healthy environment benefits everyone.

In fact, much can be done to solve the AMD problem.  Many agencies, groups, organizations, and private individuals are currently working to reduce the effects of AMD.  In Northeastern Pennsylvania, many volunteer initiatives are underway that people can get involved in. Check out the Links page for environmental agencies and organization that work to improve the health of the regional watersheds.

Follow the links Acid Mine Drainage pop-out links to read about our current watershed enhancement projects.