The Orange Animas

Last week, an estimated three million gallons of mine sludge poured from the dormant Gold King Mine, north of Silverton, Colorado, into Cement Creek, sending an orange plume of acid mine drainage down Cement Creek into the Animas River, through Durango, into New Mexico, where it met the San Juan River and flowed into Utah—the plume is still en route to the Colorado River. Officials estimate about three million gallons of wastewater were released after a U.S. Environmental Protection Agency crew accidentally breached a dam while investigating how to stop existing leakage from the mine on August 5. From the EPA:

The intent of the investigation was to assess the on-going water releases from the mine and to treat mine water and to assess the feasibility of further mine remediation. The plan was to excavate the loose material that had collapsed into the cave entry back to the timbering. During the excavation, the loose material gave way, opening the adit (mine tunnel) and spilling the water stored behind the collapsed material into Cement Creek, a tributary of the Animas River.

Abandoned mine drainage is nothing new for old mining communities, or the Animas.  It occurs when surface water comes into contact with rocks and minerals that contain sulfur—in this case, pyrite—and oxygen, resulting in sulfuric acid and dissolved iron. This often happens in old abandoned mines—prior to the 1977 Surface Mining Control and Reclamation Act,  mine reclamation was unregulated. From a KUNC story:

For years, miners were not required to do anything with this water. In fact, most of them would dump it right into a creek, or put it in ponds with their tailings, where it became even more acidic.

“In the old days there was very little control and not much attention paid to control [of acidic water from mines],” said Cohen [Ronald Cohen, an environmental engineer at the Colorado School of Mines].

Fast forward to 2015, and the state of Colorado is dotted with abandoned mines — 22,000, according to the state’s Division of Mining, Reclamation and Safety — filling up with water that runs into its streams. And the mines outside of Silverton? They’re some of the worst.

The resulting sulfuric acid can release naturally occurring heavy metals contained in rocks such as manganese, lead, cadmium, copper and zinc, leaching those metals into the water and resulting in a toxic fluid. That contaminated water then flows out of the mine adits, but many have been blocked off or reclaimed (and some, though blocked, are leaking, as the Gold King Mine was).

What did this release of three million gallons of acid mine drainage do to the river? Find the EPA’s initial report of water samples collected after the breach here.  It shows elevated levels of iron, manganese, zinc and copper below the mine breach. By the time the plume reached Durango, the levels of those metals were lower, but still elevated. The Mountain Studies Institute has also been collecting samples, which are still being processed. From a High Country News article: 

A test by Colorado Parks and Wildlife, in which trout in cages were placed in the river prior to the plume’s arrival, has so far shown no acute effects: Only one of 108 fish had died during the first 24 hours in contaminated water. Meanwhile, the Mountain Studies Institute has been monitoring macro-invertebrates, and their results have been similarly positive.

The flowing mine water is being treated in a series of settling ponds near the mine portal by raising the pH through the addition of lime and sodium hydroxide and adding flocculant to increase sedimentation, this is effective, according to the EPA. Long-term impacts on the river, economy, agriculture and other affected sectors are still unknown.

In the Animas River’s drainage, the Animas River Stakeholders Group, which formed in 1994,  just after the last mine in the area had closed, works to improve water quality in the basin. The group, a collaboration between concerned citizens and representatives from industry and agencies, formed to fend off  Superfund designation. Although Superfund comes with the cash and assistance to remediate  such environmental problems, locals feared that such designation would destroy tourism. The group began with a lot of work to do, from a recent blog post on the Animas River Stakeholders Group:

In its first years of operation, the group sampled some 200 abandoned mine sites, then prioritized 33 in need of the most work. The group directly sponsored close to 20 mine remediation projects in the upper Animas River watershed and was indirectly involved in 40 more, considerably improving the water quality in several tributaries to the Animas River, including Mineral and Cement creeks. They also developed recommendations for a number of site-specific water quality standards that were ultimately adopted by the Colorado Water Quality Control Commission.

Because of the liability stemming from the Clean Water Act that is associated with directly treating polluted mine drainage, most of the Animas Stakeholders’ remediation projects have focused on prevention through isolation of reactive mineralized material from water, either by removing tailings and waste rock from a drainage (and in a few cases reprocessing it at a local mill), capping it with an impermeable material, or diverting water that previously fed into old mine workings and tailings piles to minimize metal-loading.

An unplugged tunnel at the Gold King mine in the upper Cement Creek drainage

A turning point in the Animas River Stakeholder Group’s mission came after the last mining company to operate in Silverton, Sunnyside Gold Corp., built three massive bulkheads inside the vast underground workings of the Sunnyside Mine in the upper Cement Creek drainage starting in 1996 as part of an agreement with the State of Colorado that released the mine company from environmental liability.

The bulkheads were intended to act as corks, simply preventing water from draining out of the mine. The first one worked well, but when two more were added downstream in the tunnel six years later, the bulkheads collectively ended up functioning more as a bathtub plug, causing the water table inside the mountain to rise and eventually gush out of other mine adits—horizontal passages leading into a mine for the purposes of access or drainage—higher in the upper Cement Creek drainage.

As of March, mine drainage water poured out of a group of adits on the same slope—the American Tunnel, the Red and Bonita, the Mogul…and the Gold King—in an amount equal to the contributions of the 33 most-polluting mines the Animas Stakeholders group identified during its initial study 15 years ago. From that same blog post:

Collectively, these leaky adits have created one of the largest untreated mine drainages in Colorado, a festering sore oozing a toxic cocktail of heavy metals including zinc, cadmium, copper, manganese, iron, aluminum and lead.

But of course, as of last week, contaminated waters poured from the Gold King. As reported by KUNC, when the spill occurred, the Gold King was not the object of the EPA’s cleanup:

The agency had planned to plug a mine just below it, the Red and Bonita Mine, with the goal of reducing acid runoff from that mine.

Since mines are interconnected, however, and a plug in one can lead to more water flowing out the other, the agency planned to “remove the blockage and reconstruct the portal at the Gold King Mine in order to best observe possible changes in discharge caused by the installation of Red and Bonita Mine bulkhead.”

That project began July 2015. The Gold King Mine released its toxic load at 10:30 a.m. August 4, 2015.


Today, emotions of anger, fear and frustration and running strong, as reported by the New York Times. The U.S. EPA has published information about its claims process for compensating citizens who have suffered injury or property damage caused by the U.S. government’s actions.

While others have refocused that frustration, from an editorial in Parting the Waters: 

All development of the natural environment carries risk to our water resources. I suppose it’s human nature to ignore that fact and instead focus on the bright orange river staring you in the face.


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