The Dolores and Colorado rivers could face lower water quality according to a recent decision by the Bureau of Reclamation that could cause the closure of the Paradox Valley Salinity Control Project.
The bureau has decided on a no-action alternative after an environmental analysis to find solutions for a brine injection that has neared its capacity and caused earthquakes.
Engineers installed the project in 1996 on the lower Dolores River in Southwest Colorado to remove natural salt deposits and improve water quality in the nearby Colorado River for millions of people and farms downstream.
But an unintended consequence of pumping briny fluid deep underground has been thousands of human-induced earthquakes. The largest one was a 4.5 magnitude quake on March 4, 2019, that was felt in Moab, Dove Creek, Cortez and Towoac.
After the record-breaking earthquake for that area, the Bureau of Reclamation salination-injection well facility was shut down temporarily to allow for more study. It restarted at a lower injection rate, but earthquakes still occurred, including a 3.7 magnitude quake on Dec. 8.
Well pressure is reaching permit threshold standards, indicating the total capacity of the Leadville formation site storing the brine has been reached, said Lesley McWhirter, environmental planner for the Bureau of Reclamation.
In December 2019, the Bureau of Reclamation released a draft environmental impact statement outlining potential alternatives to the project.
The impact statement proposed several alternatives, including no action, a new nearby injection well, a surface evaporative system and a zero-liquid discharge brine crystallization system. Alternatives have a goal to last 50 years. The proposed new systems were each priced at $99 million and up.
On Dec. 11, Bureau of Reclamation released the final impact statement for the Paradox Valley Unit.
The benefits and impacts of the alternatives for salinity control were analyzed, and the “no action alternative was selected as the best means to avoid environmental harm while maintaining compliance with the Salinity Control Act,” a press release said.
“After considering public comments, Reclamation determined the no-action alternative achieves the best balance among the various goals and objectives outlined in the environmental impact statement,” said Ed Warner, manager of Reclamation’s Western Colorado office. “The no-action alternative is in the best interest of public health and safety.”
The Paradox Valley Unit is one element of Reclamation’s broader Colorado River Basin Salinity Control Program, which is a partnership among Reclamation, several federal agencies and seven basin states. This partnership developed measures that prevent an estimated 1.22 million tons of salt from entering the Colorado River system each year and contribute to long-term water quality goals.
According to the impact decision, the Paradox salt injection well would continue to operate until no longer feasible.
“Once the existing well is no longer operable, there would be no salinity control in the Paradox Valley unless a feasible alternative is identified in the future,” the report says. Any future feasible alternative would be subject to analysis under the National Environmental Policy Act.
According to the final impact statement, after the injection well has ceased for two years, the well would be plugged and abandoned in accordance with the Environmental Protection Agency injection-control permit, and the area reclaimed.
The pipelines and existing brine production wells might be capped or plugged and abandoned. The buildings would be assessed for possible future use. Reclamation would retain its land associated with the Paradox Valley Unit until a future date when the land would be re-evaluated for other uses. The agency would also retain its water right.
Monitoring for seismic events via the Paradox Valley Seismic Network would continue until Reclamation determines it is no longer necessary, the report says.
How it worksAt the Bureau of Reclamation facility near Bedrock, a series of nine wells draw up the briny groundwater prevalent in the Paradox Valley, known for salt deposits left over from an ancient shallow sea.
The water is piped to a nearby injection well, which sends the salt water 2.9 miles underground to the Mississippi Leadville Formation.
The Dolores River is a tributary of the Colorado River. By removing natural salt loading in the Dolores River, water quality is improved on the Colorado for an estimated 40 million people downstream, including municipalities, 5.5 million acres of farms, industry and for communities in Mexico.
The facility has been intercepting and injecting about 95,000 tons annually of brine into the injection well. The proposed alternatives are seeking comparable amounts to be removed, to be funded by the federal government.
The injected brine fluid is known to cause earthquakes by adding lubrication and pressure to fault lines. An estimated 6,000 mostly smaller earthquakes are thought to have been caused by the Paradox injection well since the 1990s, according to government reports and seismologists.
The final environmental impact report and decision is available online.