The Colorado Sun originally published this story on August 3, 2025.
On a cloudy day in late July, Anthony Edwards looked out at where Cement Creek meets the Animas River in Silverton, a town in southwestern Colorado. Nearly 10 years prior, he stood in the same spot watching as millions of gallons of acid mine drainage gushed past, turning the water a sickly yellow-orange.
“We all knew that this was going to change everything,” recalled Edwards, who was San Juan County’s spokesperson during the spill.
On Aug. 5, 2015, contractors for the Environmental Protection Agency inadvertently unleashed 3 million gallons of wastewater trapped behind the collapsed entrance of Gold King mine while doing excavation work in remote San Juan County. The yellow, heavy-metal-laden water impacted communities from Colorado to Utah. It drew national and international attention, forcing the ongoing impacts of historic mine pollution into the spotlight.
At the time, people hoped the Gold King mine spill would pressure the federal government and communities to finally reckon with the legacy of mining in southwestern Colorado and its impact on water and aquatic life. The EPA quickly set up an interim treatment plant to catch contaminated water from Gold King, but other mines in the Bonita Peak Mining District are still draining right into the rivers and streams. And 10 years later, some local advocates and experts are frustrated with the slow pace of action.
“The EPA has done nothing to significantly improve water quality,” said Peter Butler, a leading expert on Animas River water quality. Even though they’ve spent somewhere near $140 million in the last decade, he added.
Acid mine drainage is a global issue. In the United States, the drainage comes out of coal and metal mines across the country. In 1994, a few years after the last gold mine in Silverton closed, the Forest Service estimated there were about 20,000 to 50,000 mines leaking onto Forest Service lands in the West.
The lead-up
Silverton, a small town tucked away in the San Juan Mountains at 9,300 feet in elevation, is tied closely to its mining legacy. Tourists talk about finding gold. The historical society touts its “world class” museum and underground mining exhibit, which has been recognized by the Smithsonian Institution. The community knew about the drainage — how could you not when the orange-brown Cement Creek still runs right through town?
In the 1990s and early 2000s, Silverton residents and local groups, like the Animas River Stakeholders Group, did sampling, weighed treatment options and debated seeking federal Superfund status. But while they debated, acidic water built up in the web of mine shafts, drifts and tunnels cut into the innards of Bonita Peak north of town.
That build-up continued until 2015, when 3 million gallons of water spilled out of the Gold King mine opening. The acidic water was thick with copper, zinc, aluminum, lead, iron, arsenic and other metals.
The water didn’t kill off sensitive fish and insect species mainly because they were already dead and gone after years of naturally mineralized runoff and prior acute mining-related releases, Scott Roberts, aquatic ecologist for the Mountain Studies Institute, said in an interview in July.
He studies insects and aquatic ecosystems in the Upper Animas River watershed and tracks acid mine drainage to assess its impacts on aquatic life.
“The Gold King was not the first, and not even the last, unplanned mine release that’s happened in this watershed,” Roberts said.
Within months of the spill, the EPA set up a temporary treatment plant to catch Gold King’s drainage. Lawsuits abounded and distrust of the feds reached a fever pitch. The EPA took charge, establishing a Superfund site in 2016 called the Bonita Peak Mining District. The Superfund site includes 48 historic mines or mining-related sources of acidic drainage.
“This event really shook the EPA,” said Butler, who led the Superfund community advisory group for years. “The EPA ended up being called a potential responsible party under Superfund law. That was a first.”
Now, years of data-gathering are about to transition into big decisions and action on how to treat pollution from the Bonita Peak Mining District, said Chara Ragland, the community group’s new chairperson.
The main focus is on addressing drainage from the “big three” polluters: tailings piles at Mayflower Mill and Howardsville northeast of Silverton that drain into the Animas, and mines that drain into Cement Creek.
But the Trump administration’s staffing and funding cuts at the EPA are slowing down some work. Some projects have been done, but the main polluters still degrade water quality. The work to heal the bleeding mountain is years from completion. After that, the state will take over ongoing monitoring and maintenance, Ragland said.
“It’s not like you can ever just totally walk away. Unfortunately, that’s just sort of the reality of hard rock mining,” Ragland said. “They have successfully remediated close to half of the sites in the mining district. So we have progress.”
The first 72 hours
Edwards, the San Juan County spokesman, remembered getting a text saying there was a problem up near Gold King. People knew the EPA was up at the Gold King mine site trying to figure out what to do about the contaminated water. He was waiting for 45 minutes before the plume surged into Silverton. They had no idea what was coming into town with it.
“I was just trying to figure out what happened, wondering, ‘is everybody OK?’” he said.
Upstream, the EPA contractors watched as murky orange-brown water leaked out of the rubble at the collapsed Gold King mine opening on the morning of Aug. 5.
What started as a trickle quickly turned into a torrent. Orange-yellow water rushed down the mountainside into Cement Creek. The erosive force of the water coming out of the mine’s entrance picked up metal-laden sediment that was outside of the mine and carried it downstream.
The EPA estimated that 99% of the metals were actually from waste rock outside of the mine that were picked up by the gushing water, Roberts said.
The SunnyD-colored plume would eventually travel over 100 miles downstream. It gushed down the Animas River, which runs north to south near U.S. 550 (the scenic Million Dollar Highway).
Butch Knowlton, then La Plata County’s emergency manager, quickly started doing the math to determine how long it would take for the plume to flow past the Animas Valley Irrigation Ditch north of Durango. The plume reached the firmly shut headgate at around 6 a.m. Aug. 6.
The city of Durango stopped pumping raw water from the river. State wildlife officials put cages of small fish into the river to try to see if the murky water was dangerous enough to kill. People rushed to grocery stores to buy bottled water.
Butler remembered about 150 people gathered at 32nd Street Bridge to wait, he said.
“It was kind of fearful. Eerie and quiet,” Butler said. “I remember seeing somebody’s kids playing in the water, and somebody screaming, ‘Get them out of the water!’”
The plume flowed into Durango around 8 p.m. Aug. 6.
It went south to the San Juan River then west into Utah and, eventually, Lake Powell, one of the main storage reservoirs for the 40 million people living in the Colorado River Basin.
In Farmington, New Mexico, Calvin Yazzie, a Navajo farmer and rancher, watched the sickly yellow-colored water flow into the San Juan River. Yazzie drew water from the San Juan to grow alfalfa and raise cattle on a small farm and ranch.
Everything was chaotic, even panicky. The rivers have spiritual significance in Navajo culture. They prayed to the river for forgiveness, Yazzie said.
“I didn’t understand. Why? Why did they allow this to happen?” Yazzie said.
A legacy of mining
The legacy of mining in Silverton and San Juan County made it difficult, maybe even impossible, to tell where exactly the water came from and who was at fault.
Silverton was the mining town that wouldn’t quit. Mining was the town’s heartbeat since its birth in 1874. Within a few decades, Silverton was a thriving community, with schools, shops and families brought together by their shared ties to the mining industry.
For Tom Horton, who works at the San Juan Historical Museum, it’s a living history. He remembered hearing about heists, gold disguised in paint cans ($165,000 per can), and talking with miners from the town’s first days. One miner said he was 12 years old when he and his dad hiked over the steep terrain of the San Juan Mountains from Mancos to Rico to Silverton to work in the Old 100 Gold Mine near Howardsville, Horton said.
In its early years, Silverton was a wild place, with people coming from far and wide to try to strike it rich and ending their days in its saloons.
Olaf Arvid Nelson was one of those people. In 1887, he located the original Gold King claim on the slopes of Bonita Peak, but died before he could make his fortune.
For years, the largely unregulated mining companies came in, went bankrupt and sold off mines, including Gold King and its competitors like the Sunnyside and Mogul mines. Miners kept burrowing into Bonita Peak, eventually blasting an 11,000-foot-long tunnel through the mountain, called the American Tunnel. Gold King stayed dry as water flowed deeper into the mountain.
The mountain’s once-untouched rock turned into a honeycomb of tunnels that more closely resembled Swiss cheese.
After Gold King closed in the 1920s, the Sunnyside mine was the biggest on the mountain. It lasted until 1991 when it was closed for good.
The mine’s owner Echo Bay, a Canadian company doing business as Sunnyside Gold Corporation, had been treating the mine drainage. As it prepared to shut down the water treatment plant, the company plugged the American Tunnel, adding three bulkheads and creating a pool of water deep inside the mountain.
After that, drainage from the “dry” Gold King mine started to increase. By 2009, the state Division of Mining Reclamation and Safety called the Gold King “one of the worst high quantity, poor water quality draining mines in the state of Colorado,” according to Jonathan Thompson, author of “River of Lost Souls.”
By the time the water burst through Gold King’s collapsed entrance, the property boundaries inside the mountain and how water passed between them was an ownership labyrinth. Sunnyside Gold, which denied that plugging the American Tunnel caused the spill, paid out millions of dollars in settlements.
10 years later
A decade later, details of the spill are clearer even if the water coming out of the mines around Silverton remains murky.
The Gold King spill hardly had any environmental impact, according to research before and after the incident. Aquatic ecosystems were already reduced by natural forces tied to a long-ago collapsed volcano and the mineralized rocks in the San Juans. Some waterways were already aquatic dead zones. Fish and insects already faced reproductive challenges.
Mining just exacerbated those conditions, but in some cases, treating mining drainage helped bring aquatic species back, Roberts said.
“The canary in the coal mine was already absent,” Roberts said. “Therefore, we couldn’t detect the change.”
In New Mexico, Yazzie lost about $10,000 worth of alfalfa and had to sell off his cattle. The irrigation canals were shut down too long, and customers didn’t want produce grown next to the San Juan River.
In 2018, he joined a lawsuit against the EPA alongside about 300 other Navajo farmers. Seven and a half years after the spill, he received a payout from the $7.5 million settlement package.
He never ranched again.
“We sold out,” Yazzie said. “If you wanted to see the face of a heartbroken man, that’s how I was. I did my best to not allow that to happen, but …”
In Silverton, Edwards said the county and town staff are still sometimes swamped with Superfund work tied to the Bonita Peak Mining District.
The EPA focused on gathering data and tackling low-hanging projects, like stabilizing waste rock piles and cleaning up lead-contaminated soils, at over 20 of the mining district’s 48 sites, Ragland said.
The interim treatment plant built after the spill is still treating drainage from Gold King. But the other main pollution sources — like the American Tunnel, Mogul Mine and the Red & Bonita Mine — are still sending acidic, metal-heavy water into the rivers and streams of the Upper Animas watershed.
“EPA is on track to propose key source control remedies for public comment next year,” Cyrus Western, the agency’s regional administrator, said. “Doing things right takes time, but we’re committed to long-term results.”
A plan to go inside the mine to treat acidic water in the maze of tunnels is up in the air. The EPA’s Office of Research and Development was supposed to manage that, but the office has been thrown into turmoil by budget and staffing cuts ordered by the Trump administration, Ragland said.
In May, the EPA expected to wrap up work on a new repository site for sludge — the thick mixture of minerals, metals and water that remains after treatment — from Gold King. Federal staffing cuts caused delays for the project which will hopefully wrap up in the fall, Ragland said. In the meantime, more sludge is piling up in big, nearly full geotextile bags at the treatment facility.
Locals and some people in the Community Advisory Group, or CAG, want the work to go faster. They want to see progress on improving water quality. They want a more detailed timeline for whether and how the EPA plans to treat all of the drainage running into Cement Creek.
They want to make sure another spill like Gold King never happens again.
Superfund law, established in the Comprehensive Environmental Response, Compensation, and Liability Act, can be expensive and complex, Edwards said.
“Am I concerned and disappointed how long things take? I would say, yes,” Edwards said. “But understanding the CERCLA process, the scrutiny and requirements take a long time.”
The CAG is advising the EPA on a treatment plan and staying in touch on big decisions about other sites in the mining district at Mayflower Mill and Howardsville, Ragland said.
Everyone is worried about long-term funding once settlement money runs out, she said. The Superfund’s goal is to improve water quality, so they’d face tough decisions if they don’t have enough money to address all of the big problem areas.
“If that’s all we have, how are we going to prioritize, if we have Howardsville and Mayflower and the Gold King mine?” Ragland said. “Are we not going to do one of those and be left with significant contamination in this area?”
Looking ahead, Yazzie wants farming and fresh produce stands to return to roads along the San Juan River. Butler wants to reduce metal concentrations and help aquatic life in the river systems. Roberts just wants to make sure that the solutions are based on science.
Ragland described herself as an optimist but also a realist. People can never completely fix things once they mess them up, she said.
“Sometimes there’s just no going back,” she said, “but I don’t see that that gives me a pass to not keep on trying.”
