Abandoned mines cause environmental devastation
June 18, 2007
SUMMIT COUNTY – Prospectors began hacking at Colorado’s mountainsides 150 years ago in search of gold, silver and any other kind of profitable metal that might have been nestled deep inside the rock. Soon mines peppered the landscape. And while most of them were abandoned nearly a century ago, their consequences on the region’s ecology and human health will continue to thrive long after our own generation has withered. The Environmental Protection Agency estimates that 500,000 abandoned mines exist in the U.S., the majority of which lie out West. Colorado is home to about 23,000 of them, according to the Colorado Division of Reclamation Mining & Safety. Not all of the mines emit pollutants, but enough of them do to cause a host of problems.Perhaps the most obvious are the physical dangers. Last year, 22 people died nationwide from falling in abandoned mine shafts, inhaling deadly odorless gases or being crushed in cave-ins. Those dangers represent just a small piece of the problem these old mines create.Ecological devastationAbandoned mines can wreak environmental havoc, especially on aquatic ecosystems. Most of the metals mined in Colorado, such as gold, lead and copper, are found in deposits with metal sulfides. Hardrock mining processes disturb the rock, leaving behind waste rock piles filled with metal sulfides, such as pyrite, and exposing greater surface areas of those rocks to water and air. When sulfides are exposed to oxygen from water and air, they oxidize, just as iron turns rusty when exposed to air. When the oxidation occurs, lead, copper and other metals are released into drainage water as it trickles over the rocks, spiking the water’s acidity level. The acidic water then runs into rivers and streams, often, but not always, turning them a ruddy, orange color.
This process, known as acid mine drainage, can be devastating for all kinds of organisms living in water, such as fish, invertebrates and plants.”Forty percent of watersheds in Colorado are to some degree impaired by abandoned mine runoffs,” said Timothy Brown, a research associate at the Center of the American West at the University of Colorado at Boulder.Although oxidation of the minerals happens naturally, surface area exposure from mining operations accelerates the process by a million times, said Joseph Ryan, a professor of civil and environmental engineering at the University of Colorado at Boulder.Unfortunately, the acid mine drainage problem often grows worse instead of better over time as more and more rock surface becomes exposed. In fact, many of the mines dug during the Roman Empire still create acid drainage.”It’s a problem on the order of thousands of years,” Ryan said.Some minerals pose threats to human health, but many more are lethal to fish and other aquatic life.For example, humans can tolerate copper fairly well. According to the EPA, we can ingest up to 5,000 micrograms of the metal per liter of water without adverse consequences. Fish, on the other hand, can only tolerate about 65 micrograms of it per liter of water.Up in Summit County, a region laced with mining history, there is no shortage of acid mine drainage or the downspiraling effects it produces on an ecosystem.
This summer, for example, several government agencies, including the EPA, U.S. Forest Service and U.S. Geological Survey, are working together to test water samples from the Snake River in an effort to develop a plan to restore its watershed. Peru Creek carries waters polluted with zinc, cadmium and other toxic metals in the run-off from the Pennsylvania Mine into the river. Preliminary data suggest that fish cannot survive in Snake River, due to high metal concentrations from acid mine drainage and other sources of pollution, according to an e-mail from USGS researcher Stan Church to the Snake River Task Force.Disturbed economics follow disturbed aquatic ecosystems, especially in an area like Summit County, ripe with a burgeoning recreation industry – one that includes plenty of fishing. “As Colorado makes the transition from extraction industries, such as mining and timber, to recreation, the health of the those watersheds is going to be ever more important,” Brown said. “We need municipal drinking water, and we need to have healthy ecosystems for visitors and citizens.”Human health effectsBy the time most water polluted from acid mine drainage flows down the mountains into a drinking water system, such as the Dillon Reservoir, it has typically been cleaned up naturally by more pristine water downstream. The cleaner water not only decreases the acidity level, causing many of the dissolved metals to precipitate out of the water and fall to the streambed, but it also dilutes the concentration of toxic metals in the polluted water. If the natural process fails to clean the water, multimillon-dollar treatment plants typically pick up the slack to bring drinking water up to federal standards.But in Colorado, rapid development means less water to go around.”As water becomes more and more scarce, we need to be more concerned with it’s quality,” Ryan said.
And as development moves higher into the mountains, homes are being constructed closer to abandoned mines than they previously were.”The only good thing right now is that a lot of these [abandoned mine] areas are pretty wild,” said Susan Griffin, an EPA toxicologist. “If you don’t have people up there coming into contact with material, you don’t have a risk. But as soon as you have people coming into regular contact with it – living there or drinking it – then you have a risk.”Griffin suggested that people moving very near an abandoned mine may want to have their soil and water tested for toxic metals but otherwise do not need to worry.It’s true that humans tolerate many types of metals from mine waste better than aquatic life does. But several metals in this region exposed by abandoned mines through acid mine drainage or piles of exposed mine waste, such as lead and arsenic, can be harmful to humans when inhaled or ingested.Lead, a well-known human toxin, is common in this area. Children under about 7 years old are particularly susceptible to its dangerous effects, as are developing fetuses. The stomach treats lead just like calcium, absorbing it rapidly, Griffins said. Lead then absorbs into the bones.”Neurosystems are rapidly forming connections, and lead can zap and mess up those connections,” she said.The substance can cause ADHD, problems with hand-eye coordination and focus, and decreased I.Q. In adults, lead exposure can produce increased blood pressure and infertility.Arsenic, also commonly found in mine run-off and waste piles in Summit County, produces deleterious effects in humans, as well. Studies based on inhalation and ingestion through drinking water have shown arsenic to cause lung, bladder and skin cancer, among other health problems, Griffin said.
Those two metals are driving a major cleanup effort this summer in Summit County in conjunction with the EPA. Tests revealed that piles of mine waste on the National Forest Claimjumper parcel held high concentrations of both lead and arsenic. According to benchmarks the EPA uses to determine safe levels of exposure, the concentrations found are unsafe for humans. Children from a nearby condominium had even been seen playing on the waste piles, Griffin said. The danger of children inhaling or ingesting soil containing the toxic metals was unacceptably high. So trucks hauled the waste to a repository in French Gulch where it will be capped and monitored.So who is responsible for the cleanup? The majority of abandoned mines lie on private land, and many land owners aren’t even aware of their presence. Some of the mines were willed down several generations to family members who don’t know they hold the rights – and responsibilities – associated with them, according to a report from the Center for the American West. Although the federal Clean Water Act implores landowners to ensure mines on their land are not leaking toxic metals, enforcement is nearly impossible.Several federal agencies, such as the EPA and the U.S. Forest Service, are responsible for abandoned mines remediation on public land. They’re working along steadily, trying to clean up the most hazardous mines and watersheds in the country.But, of course, money is tight and politics abound.Regardless, recognition in recent years of the severity of the ecological and health problems abandoned mines can generate has sparked cleanup efforts on both federal and individual levels.”Mining has been and continues to be so fundamental to the prosperity of region, to the quality of life we enjoy,” Brown said. “But it’s time to start paying the true cost of what those mining communities are, and that includes starting to pay for the ecological impact the mining legacy has left us with. It comes with an environmental price tag that has now come due.”