By CAP Water Control Manager Brian Henning
On Friday, August 7, there was an accidental spill of sediment and metals from a shuttered Colorado gold mine into the Animas River, a tributary of the San Juan River in Farmington, NM, which is a tributary to the Colorado River. CAP is not expecting impacts to its water supply due to this spill. The heavy metals and any other contaminants will be reduced by dilution and absorption to sediments and settling in Lake Powell, if not in the upstream rivers as the plume travels toward Lake Powell.
The estimated spill volume is 3 million gallons, or 9 acre-feet, of water, and the current storage volume at Lake Powell is about 13 million acre-feet, so the dilution factor is enormous and contaminant concentrations could be rendered undetectable. As of Thursday, August 13, the water quality at the spill site has returned back to pre-event conditions. The plume is flowing in the San Juan River and, as expected, the heavy metal concentrations have diluted or settled by 50%.
CAP is closely monitoring the situation and information is being widely shared among agencies involved. We have been in communication with Southern Nevada Water Authority (SNWA) as they step up their water quality sampling procedures at Lake Mead. If any residuals of the spill contamination are detected, SNWA will notify CAP and other affected water providers and agencies.
In addition, as a precautionary measure, CAP maintenance and operations crews have been taking additional water samples to ensure the quality and safety of our Colorado River water supply. In accordance with our normal water quality sampling program, if any contaminants or other constituents are detected, we will contact our customers to prepare them in advance to make any necessary adjustments in their water treatment systems.