The Animas River turned a brownish-yellow this week, giving some La Plata County residents a flashback to 2015 when the river turned a mustard-yellow after the Gold King Mine spill north of Silverton.
Thursday’s discoloration is likely the result of increased sediment in the river from summer rain showers, according to the National Weather Service.
“I think it is very safe to say this is nothing more than soil runoff from a good, heavy rainstorm in the last 12 to 24 hours,” said Ty Churchwell, mining coordinator for Trout Unlimited.
Churchwell is also vice chairman of a citizens’ group addressing Superfund activities affecting the Animas River basin, called the Bonita Peak Mining District Community Advisory Group. Churchwell was not informed about any mining incident or release, he said.
Sandstone and limestone rock formations in Hermosa Basin have led to yellow or gold coloration in the Animas River. Red Mountain is high in iron oxide.
“That’s nothing more than rust,” Churchwell said. “When we get rain on the mountain, we get sediment in the creeks and the Animas.”
Marcel Gaztambide, Animas riverkeeper with the San Juan Citizens Alliance, said he was investigating the matter, but the coloration is “almost certainly a result of storm runoff moving sediment from the highly mineralized upper watershed.”
Erin Walter, a meteorologist at the National Weather Service, said recent, steady rain has caused an uptick in the Animas River’s flow, which could cause some extra sediment in the water.
Storm cells moved over Silverton and the Animas River drainage in the last 24 hours. Lower elevations saw about 0.1 inch of precipitation, while higher elevations saw about 0.5 inch.
“That could be the case again this evening. We’re still expecting a decent amount of storms to form over the San Juans,” she said Thursday.
Showers on Thursday afternoon and evening are forecast to bring another 0.5 to 0.75 inches of rain to higher elevations.
“We’re kind of in the thick of it here with the monsoon surge,” Walter said.
The Durango area is just shy of its normal rainfall for this time of year, according to data recorded at the Durango-La Plata County Airport.
The area normally receives 6.24 inches of precipitation from January through July 21, according to 30 years of data. So far, it has received 4.96 inches, Walter said.
From June 1 to July 1, the normal precipitation is 1.18 inches. The area has received 1.04 inches, based on historic data.
“We’re approaching our normal for the season but still a little far off because we didn’t have the best winter (precipitation),” Walter said.