On Aug. 5, about 3 million gallons of contaminated water burst out of an abandoned mine above Silverton and sent a plume of cloudy, orange water down Cement Creek to the Animas River, through the heart of Durango, and on into the San Juan River in New Mexico, the Navajo Nation and Utah. Downstream: Lake Powell.

The plume of acidic orange water, containing arsenic, lead and other toxic heavy metals, had built up as a result of “wild west” mining activity dating back to the 1870’s, as well as work to plug some mines, which ultimately redirected contaminated water into other mines. The massive plume was set loose by workers for the US Environmental Protection Agency attempting to assess and remediate the source of an ongoing trickle of pollution from the Gold King mine.

Immediate impacts appear to be less dramatic than the appearance of the water suggested. Colorado Parks and Wildlife held fish in cages in the Animas River to see if exposure to the plume would kill them, and it didn’t. The Mountain Studies Institute reports that the small bugs that live in the stream bed and make up the base of the aquatic food chain are holding on at sampling sites in the Durango area.

In terms of human health impacts, drinking water intakes on the Animas and San Juan Rivers for Durango, CO, Farmington, NM and other communities were shut off before the plume arrived. These communities relied on stored water and other sources until they were cleared to begin diverting and treating from the rivers again.

Medium-term, irrigators forced to forego irrigation from the rivers for over a week could face crop damage. Rafting companies took a hit as people were kept off the river during the peak rafting season and may still be wary. People are still being advised not to eat fish from the rivers, pending the results of testing for levels of contaminants that may have accumulated in their tissues.

Long-term impacts are harder to assess, since health impacts to both people and wildlife depend on the level and duration of exposure to the contaminants. It’s clear that the heavy metals will settle out into the sediments on streambeds and the bottom of Lake Powell, but it’s not clear how concentrated the contaminants will be and to what extent they will move back into the water column in response to storms and floods.

In assessing how this catastrophe fits into the overall regional water picture, it is instructive to zoom out geographically and look back in time. The 3 million gallons of contaminated water from the spill translate to a little over 9 acre-feet of water. This quantity is dwarfed by the approximately 13 million acre-feet currently in Lake Powell, despite the fact that it is only 54 percent full. Particularly given that the heavy metals will increasingly drop into the lake floor as the water slows down, impacts to the Grand Canyon and downstream water users should be minimal.

Looking back in time, Jonathan Thompson points out in a web article for High Country News (“When our river turned orange”) that pollution of the Animas River from mines has been a problem for over 100 years, with previous dramatic blow-outs, and waxing and waning impacts to fish as remediation efforts have gained and lost ground.

Looking ahead, this latest catastrophe may stimulate more comprehensive solutions to this long-standing problem, in the Animas Watershed and around the region.

The Colorado Geological Survey inventoried abandoned and inactive mine sites on National Forest lands across Colorado between 1991 and 1999. Of the 18,000 mine features they inventoried, 900 presented environmental problems significant enough for future study. About 250 of those were found to be causing significant or extreme environmental degradation. Priority watersheds were identified in the Animas, Uncompahgre, Arkansas and Rio Grande headwaters.

Fortunately for the Grand Valley, the inventory did not identify any mine features on the Grand Mesa National Forest that were causing environmental degradation. The Grand Mesa National Forest is the source of most of our drinking water. However, problematic sites do exist in the Gunnison National Forest.

Cleanups of leaking abandoned mines have been hampered by the fact that many of the companies that established and worked the mines no longer exist. Nonprofit watershed groups often take on these problems, but are hampered by a lack of resources and liability concerns — which the Gold King blow-out demonstrates are not just hypothetical. Additional federal government resources can come with “Superfund” designations, but communities often shy away from the stigma associated with such a designation, which had previously been proposed for the upper Animas. Communities may now reassess the dangers of the potential stigma of a Superfund designation in light of the flood of publicity that has attended the orange plume descending the Animas and San Juan Rivers.

This is part of a series of articles coordinated by the Water Center at Colorado Mesa University in cooperation with the Colorado and Gunnison Basin Roundtables to raise awareness about water needs, uses and policies in our region. To learn more, go to http://www.coloradomesa.edu/WaterCenter. You can also find the Water Center on Facebook at https://www.facebook.com/WaterCenter.CMU or on Twitter at https://twitter.com/WaterCenterCMU