A wastewater facility on Colorado's Western Slope is resuming operations more than a year after it was shut down for causing a sizable earthquake in 2019.
The Bureau of Reclamation's Paradox Valley Unit in rural Montrose County, Colo. pumps salty groundwater into a well to keep it from seeping into the Dolores River and loading it with salt. A higher salt content in the Dolores River, a main tributary of the Colorado River, makes it more difficult to use in cities and on farms throughout the southwestern watershed.
A Bureau of Reclamation spokesperson said the project is once again pumping water deep underground at a lower rate as part of a six-month experiment. The injection of brine into the well will be reduced by about 32%. If pressure begins to build within the well, threatening more earthquakes, then the agency will shut it down again.
The project has been idle since March 4, 2019, when a magnitude 4.5 earthquake shook communities across a broad swath of western Colorado and eastern Utah.
In the 13 months since then, Reclamation spokesperson Justyn Liff said the agency has been monitoring the pressure within the rock formations that the well injects into, as increased pressure is linked to increased likelihood of earthquakes. Pressures have been decreasing, Liff wrote via email.
"Based on our analysis of data gathered after the March 4 earthquake, we believe it is prudent to restart injection operations at the unit at a decreased rate," said Reclamation's Western Colorado area office manager Ed Warner in a statement. "By continuing to operate the well at the decreased rate we are ensuring we get the full life and value from the well."
Meanwhile, the agency is exploring other options to dispose of the salty groundwater. A draft environmental impact statement released December 2019 laid out several alternatives to the earthquake-prone well:
- Retire the Paradox Valley Unit, and discontinue salinity control activities in the Paradox Valley.
- Drill a new well in a different geologic formation less likely to induce earthquakes.
- Construct evaporation ponds in the valley, which would allow water to evaporate from the brine. The remaining salts would be collected for either landfill disposal or for sale as a commodity.
- Build a Zero-Liquid Discharge Technology facility, which would treat the brine using thermal crystallizers. Leftover salts would be stored in a 60-acre landfill in the valley.
A final environmental impact statement on the future of the Paradox Valley Unit is expected this summer. Its release will trigger a 30-day comment period, with a final decision expected late summer.
This story is part of a project covering the Colorado River, produced by KUNC and supported through a Walton Family Foundation grant. KUNC is solely responsible for its editorial content.