Story highlights

The wastewater that contaminated the Animas and San Juan Rivers is an old problem

Local officials and the EPA have worked for years to try to reduce pollution

CNN  — 

One week after an Environmental Protection Agency cleanup effort at a dormant mine turned into a disaster, the agency announced it is halting all EPA field work in mines.

More than 3 million of gallons of wastewater from the Gold King Mine spilled into the nearby Animas River, turning it an alarming mustard hue.

The photos of the yellow-orange river were widely shared and have brought attention to a longstanding challenge that many were unaware of: how to regulate, treat and pay for the upkeep of abandoned and dormant mines in Colorado and across the country.

Here are some key points to understanding the issue:

How many mines exist in the United States that are similar to the Gold King Mine?

The Gold King Mine hasn’t operated since 1923.

The EPA has been overseeing abandoned mine lands – which can include bodies of water and surrounding watershed – for many years. The mines can pose “serious threats to human health and the environment,” the EPA says on its website, so the agency initiates and supervises the examination of these sites and tries to maintain or clean them up. The agency lists more than 15 case studies it has conducted of abandoned mines across the country, mostly in the West in states such as Colorado, Montana and California, but also in Vermont and Tennessee.

Earthworks is a Washington-based nonprofit environmental group that works with communities near mines. The scientists and activists who work for the group have been concerned since the 1990s about contamination leaking from old, inactive or abandoned mines.

The group wrote a report in 1993 which said that there were more than half a million abandoned hardrock mines in 32 states.

How dangerous could these mines be?

Those half a million mines, Earthworks says, have produced 50 billion tons of untreated, unreclaimed mining wastes on public and private land. The report notes that wastes can include arsenic, asbestos, cadmium, copper, cyanide, iron, lead, mercury and sulfur, among other material, and produce airborne pollutants.

In Colorado this week, leading toxicologists say there could be health effects for many years from heavy metals such as mercury and lead that spilled into the water of the Animas River. Exposure to high levels of these metals can cause many health problems, including cancer and kidney disease, and also lead to developmental problems in children.

“Oh my God! Look at the lead!” said Joseph Landolph, a toxicologist at the University of Southern California, after looking at the amount of lead in the Animas River, which was nearly 12,000 times higher than the acceptable level set by the EPA.

“This is a major, major problem,” said Jonathan Freedman, a toxicologist at the University of Louisville.

River toxic spill: ‘This is a real mess’

In its latest statement, however, the EPA predicted the water would not have harmful effects on the health of people or animals.

“Based on the data we have seen so far, (the EPA doesn’t) anticipate adverse health effects from exposure to the metals detected in the river water samples from skin contact or incidental (unintentional) ingestion,” the agency said. “Similarly, the risk of adverse effects to livestock that may have been exposed to metals detected in river water samples from ingestion or skin contact is low.”

How did the leak happen and how did the EPA initially respond?

On August 5, Environmental Protection Agency workers were trying to place a pipe into the opening of the mine to collect wastewater and prevent it from polluting Cement Creek and the Animas River. Before the spill, water carrying “metals pollution” was flowing into a holding area outside the mine.

Though it’s unclear still exactly how the mistake was made, the EPA said the spill occurred when one of its teams was using heavy equipment to enter the mine near Durango, Colorado.

EPA Administrator Gina McCarthy apologized Tuesday for the spill and said, “I don’t have a complete understanding of anything that went on in there. If there is something that went wrong, we want to make sure it never goes wrong again.”