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FARMINGTON — Despite initial concerns that acid mine waste that spilled into the Animas River could cause widespread fish and wildlife deaths, only a few fish deaths have been reported.

Officials say that could be because the fish population near Silverton, Colo., where the mine waste entered the Animas River, had already been destroyed, and dilution of the water through tributaries running into the river diluted the concentration of heavy metals to safe levels.

There have been some instances of dead fish being found, but those reports appear to be isolated so far, officials say, while none of the wildlife that lives around the river has shown definite signs of metal poisoning.

Matt Anthony of the New Mexico Department of Game and Fish said most wild animals are smart and would likely avoid toxic water.

"If it tastes funny, they don't use it," Anthony said.

Prior to the toxic plume arriving in Durango, Colo., Colorado Parks and Wildlife placed 108 caged fingerling trout in the river to test the effect of the mine waste. Department officials said one of the fish died, and the death was not necessarily caused by the mine waste.

The fingerlings were removed from the river and sent to a fish health lab, where they are being tested for high levels of metals. The division does not expect to have results back for at least another week.

While the lack of a mass fish die-off has been good news, officials warn that the situation could have been much worse, as the metals typically found in a mine like the Gold King Mine are often toxic to fish.

When it was operational, the Gold King Mine produced not only gold, but also lead, zinc, silver and copper, according to John Ridley, a geoscience professor at Colorado State University who has studied mines in the Silverton area and takes students there every summer.

While those metals were mined for their economic value, other, more dangerous metals could be found in the same rocks. These include cadmium and arsenic, which are both highly toxic.

The high levels of zinc, iron and aluminum that were part of the plume could hurt fish while not being dangerous to humans, according to Howard Ramsdell, a toxicologist at the Department of Environmental and Radiological Health Sciences at CSU who studies the impact of heavy metals on aquatic life. For example, the iron and aluminum could coat the gills of fish, causing them to suffocate, he said.

While the destruction of historic fish populations by slowly leaking abandoned mines is likely one factor that has caused people not to notice high fish die-offs, Ramsdell said the places fish live in the Animas River also probably helped.

He said the fish populations seem to be concentrated around tributaries that enter the Animas River. Those tributaries not only diluted the toxic water but also provided a place for the fish to escape. Ramsdell said he suspects the fish swam up the tributaries when the contaminants reached them.

The iron sediments also are a concern, David Charters, a scientist with the Environmental Protection Agency's environmental response team, said during a meeting Friday night at the Farmington Civic Center. He said those sediments potentially could suffocate insect populations in the river, but it does not look like that is happening.

Charters said dilution likely helped prevent major problems such as fish and insect deaths.

"We did not see the levels of metals that would cause problems for fish and invertebrates," Charters said.

Ridley said if a similar spill happened at another of the mines in the Silverton area, it could create a totally different situation.

"The whole story has taught me how little we know," Ridley said.

He said no one has data about what is coming out of all the old mines in the Upper Animas River watershed, nor do people know what is in the old mines. That lack of data means it is very hard to know what will happen if another mine produces a spill, Ridley said.

What is known is that more than 3 million gallons of mine waste was trapped inside the Gold King Mine before EPA workers accidently breached a plug at its entrance.

"You'd have to wonder if it would have blown out on its own at some point," Ramsdell said.

Ramsdell said it is also important that mine remediation continue in the Silverton area, although the EPA has halted all remediation work as it studies the Gold King Mine situation.

"If they do nothing, there will never be fish in the (Upper) Animas River," Ramsdell said.

Hannah Grover covers Aztec and Bloomfield, as well as general news, for The Daily Times. She can be reached at 505-564-4652 and hgrover@daily-times.com. Follow her @hmgrover on Twitter.

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