For the handful of major communities along the Animas and San Juan Rivers in southwestern Colorado, it appears that the most visible, immediate effects one might expect to see from last week's toxic-mine-water blowout failed to materialize.
At Durango, a trout-fishing mecca, for example, no large fish kills have appeared, either for adult trout or fingerlings. Insect populations on which the trout and other fish depend appear no less abundant that before. The once-opaque, mustard-color wastewater – laden with large concentrations of arsenic, as well as cadmium, lead, zinc, and other toxic metals – runs clearer, although with a faint yellow tint. Water quality reportedly is returning to pre-blowout levels.
The apparent lack of acute effects from the spill "is very promising," says Ty Churchwell, a conservation specialist with Trout Unlimited and coordinator for the San Juan Clean Water Coalition in Durango.
But, he cautions, "We're not out of the woods yet."
Now comes the more challenging task: monitoring the rivers and those who rely on them to track potential long-term effects from the accident, triggered when a crew working for the US Environmental Protection Agency accidentally released a torrent of toxic wastewater from the Gold King Mine, near Silverton, Colo., on Aug. 5.
Of key concern is the fate of heavy metals the wastewater carried.
The EPA has set up a free water-quality testing program and is working with local officials to provide alternate sources of drinking water for people who live along the rivers and rely on well water, according to a statement from EPA Administrator Gina McCarthy.
For some, heavy reliance on San Juan River water for irrigation and uncertainty about the blowout's long-term influence on water quality alone elevate the accident to a disaster.
"When EPA is saying to me it’s going to take decades to clean this up, that is how long uncertainty will exist as we drink the water, as we farm the land, as we put our livestock out there near the river," Russell Begaye, president of the Navajo Nation, told the Associated Press. "That is just, to me, a disaster of a huge proportion."
The uncertainties also touch on vital river-ecology issues. Where the metals remain in solution in the water, fish can take them up. Depending on the species and metal, the fish can build up reservoirs of toxic metals in their tissue to be passed up the food chain.
Along slow-moving stretches of river, the metals collect in sediments and gravel along river bottoms, which harbor fish eggs and larvae from aquatic insects. Surface waters may be clean enough for juvenile and adult fish, but levels in the sediment can be fatal to fish eggs and bug larvae.
"Some of the unseen impacts can be the most devastating," says Eddie Kochman, who served as the aquatic manager within what once was the state's division of wildlife, now the division of parks and wildlife.
Aquatic invertebrates in particular, which provide food for fish, "are much more susceptible to being killed" by events like the Gold King Mine blowout than fish, he says.
Pulses of water from spring snowmelt or intense summer storms can stir up the contaminants to travel farther downstream.
Indeed, the EPA has warned that the Animas could run yellow again for brief periods, says Sinjin Eberle, spokesman for the southwest regional office of American Rivers, a river-conservation group.
The effluent from the Gold King Mine flowed down Cement Creek, which joins the Animas at Silverton. As it flowed, it left residue behind along the creek banks. Heavy rains are likely to mobilize that residue, sending it down to the Animas as well. This could force environmental officials to temporarily close portions of the river to fishing, kayaking, or rafting.
"Will all of this ever flush out? Who knows?" says Mr. Churchwell of Trout Unlimited. "At least there are numerous events during the year where our river level rises, flow increases dramatically."
That will help move contaminants down river, he notes. That may be of little comfort to communities downstream, but such events also tend to further dilute the contaminants as they move past creeks that flow into the main stem, he says.
The blowout represents a public relations disaster for the EPA, and to a lesser extent for the tourism-dependent region.
Several years ago, the EPA gained access to the Gold King Mine and other nearby sites, says Todd Hennis, president of San Juan Corp., which owns Gold King. The properties showed elevated levels of cadmium, copper, lead, and zinc, in addition to hosting mine openings that leaked acidic water bearing contaminants at levels known to be toxic to aquatic organisms.
The EPA had planned this summer to install a bulkhead in a nearby mine, the Red and Bonita Mine, to stem the flow of contaminated water that it was releasing.
In anticipation, the agency last year began to rebuild the entrance to the Gold King Mine higher up the mountain. The agency wanted ready access to Gold King to see what impact the new bulkhead might have in backing water up into Gold King.
But the work season is short at those elevations. The contractors "felt like they didn't have time to finish the job, so they backfilled the portal," Mr. Hennis says. In the process, the team may have inadvertently blocked a discharge pipe that state mine-reclamation representatives had installed a few years earlier.
The end result: A huge amount of water gathered in the mine, he says.
In picking up where it left off last year, the work crew accidentally triggered the release that fouled the Animas.
"In defense of the EPA, the guys on the ground were good, experienced people," Hennis says. Given the large number of variables involved in the overall operation, "it could have happened to anyone."
The release represents a 3-million-gallon insult to an already-injured river system – an exclamation point to what Mr. Eberle describes as the real disaster. He calls it the disaster of a thousand cuts.
The Gold King Mine and many others located high in the regional watershed "have been putting highly contaminating metals and arsenic into the water for decades," says Eberle of American Rivers.
By some estimates, some 30 abandoned mines empty varying amounts of contaminated water into the upper Animas River.
This pollution comes on top of acidic, metal-enriched water that occurs naturally as snowmelt and rainfall percolate through metal-rich formations in the San Juan Mountains.
Even before the blowout occurred, a 20-mile stretch of the Animas River beginning at Silverton was in serious decline, a result of contaminated water moving down Cement Creek and into the river, Churchwell says.
According to the EPA, over the years surveys by the Colorado parks and wildlife agency have found no fish in the Animas River for the first two miles below Cement Creek. The agency has also found a precipitous decline in fish since 2005 along an additional 18 miles of river.
Cement Creek itself probably has never sustained fish, Churchwell adds.
Durango, some 50 miles downstream from Silverton, has managed to avoid such heavy contamination because along the way a number of pristine creeks dilute the contaminants.
But even at Durango, where a stretch of the river has been on the state's Gold Medal list for water quality since 1999, wildlife managers stock the river with a significant number of trout to ensure enough trophy-sized fish to anglers.
One reason: residual heavy metals in the river.
"The trout are trying to reproduce," Churchwell says. But even accounting for typical survival rates for eggs, a very small percentage hatch.
"Most of those eggs are dying because of the heavy metals in the water," he says.
For all the criticism the EPA has received in the wake of the blowout, Mr. Kochman, the retired state wildlife official, cuts the agency some slack, as do some others.
"The EPA may have made a mistake, but they were dealing with a very big problem," he says. "The bottom line is that they were trying to do something, probably with the blessing of state agencies.
"I would not be overly critical," he continues. "From a long-term perspective, Colorado's leadership, not just this administration, but with previous administrations, has been mediocre at best" in dealing with mine wastewater problems.
Piecemeal efforts to clean up mine wastewater have yielded some successes, Eberle acknowledges.
But, he adds, the Gold King Mine blowout highlights how much remains to be done throughout the West not just to clean up mining's legacy, but to see that no new mines are located near the headwaters of the region's increasingly precious waterways.