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EPA update on Bonita Peak Superfund site water treatment plant and sampling data

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U.S. EPA (
New Mexico Environment Department (

DENVER -- Today, EPA released preliminary water quality sampling data related to the temporary shutdown of the Interim Water Treatment Plant at the Bonita Peak Mining District Superfund site at Gladstone, Colorado. EPA’s analysis confirms that there were no adverse impacts to downstream drinking water or agricultural users associated with the short-term shutdown of the plant based on data that indicate minimal to no changes in water quality at sampling points downstream of Silverton in Durango. There were no observed impacts to aquatic life. Any impacts to aquatic life would be limited to the Animas River near Silverton.

The water treatment plant went offline on the evening of March 14 due to extreme weather conditions resulting in a power surge that tripped critical circuit breakers at the facility. The same weather event triggered an avalanche and several snow slides across the county road and prevented access to the plant. After a period of less than 48 hours, EPA brought plant back on line and resumed normal operations on the afternoon of March 16.  

“EPA appreciates the efforts of our partners in San Juan County Colorado and the water plant operators for working quickly to minimize the length of time the facility was out of operation and limit any localized impacts to water quality,” said EPA Regional Administrator Doug Benevento.

“During and after the treatment plant shutdown, real-time measurements of turbidity, pH and electrical conductivity from sondes in the Animas River provided no indication that downstream water users would be adversely impacted,” said New Mexico Environment Department Chief Scientist Dennis McQuillan.  “EPA’s laboratory test results confirm the interpretation of real-time sonde data.”

EPA collected water samples at four locations along the Animas River from Cement Creek to Durango from March 15 to March 21. A preliminary analysis of the sampling data from March 15 to March 20 shows a measurable elevation of metals concentrations, particularly copper, at the confluence of Cement Creek and the Animas River, about six miles below Gladstone. Levels of metals were slightly elevated at a location on the Animas River approximately one mile south of Silverton. 

Heavy metal concentrations in the Animas River at two sampling locations in Durango were well within the range of concentrations previously observed when the treatment plant is operating. The detections of low concentrations of metals in the Animas River may be associated with the temporary closure of the plant, but they may also be related to several other factors that should be considered when evaluating these data. These include snow and avalanche debris being deposited in Cement Creek, the Animas River and local waterways which potentially introduced metals-containing soils and sediments. There is also the potential for the ongoing rain and runoff at lower elevations to mobilize metals-containing sediments from the 416 fire at locations below the confluence of Hermosa Creek and the Animas River.  

Preliminary data can be viewed at  Data from samples collected on March 21 will available on this website later this week.