Southern Nevada’s federal delegation are calling on the federal government to prohibit mining on public land in the fragile Amargosa River watershed, an effort pushed by locals in the area for months.

On Tuesday, Sen. Catherine Cortez Masto sent a letter to federal land managers, urging the Department of the Interior to implement a 20-year ban on new mining operations on public land surrounding the Ash Meadows National Wildlife Refuge, a critical wetland habitat that supports a dozen endangered and threatened species.

Sen. Jacky Rosen and Reps. Dina Titus, Steven Horsford, and Susie Lee also signed the letter.

The 20-year ban is supported by the Timbisha Shoshone Tribal Council, the Nye County Board of Commissioners, the Nye County Water District, and both the town boards of Amargosa Valley and Beatty, according to Nevada Current.

Under federal law, the Department of the Interior has the authority to withdraw lands from mineral extraction for up to 20 years by approving an application for mineral withdrawal submitted by the managing agency. Mineral withdrawals can also be permanently secured through legislation passed by Congress and signed by the president. 

A federal mineral withdrawal would not dissolve previous mining claims, but it would greatly reduce mining companies’ interest in developing the area, say supporters of the 20-year ban.

In the letter, the lawmakers representing Southern Nevada ask Interior Secretary Deb Haaland to formally initiate a 20-year mineral withdrawal on about 276,000 acres of public lands researchers say is most vulnerable to groundwater depletion from mining activities. 

“Drilling for exploration or mining could puncture the highly pressurized underlying aquifer, resulting in artesian flow that could reduce spring flows and water levels at Devils Hole, and would have widespread catastrophic effects on this fragile landscape. Pit mining activities would require dewatering that would draw down groundwater levels, reducing spring flow in the Refuge and affecting the water supply for local communities,” the lawmakers wrote.

The Amargosa River travels just under the surface for most of its 185-mile course. In the stretches of the river that reach the surface — like the Ash Meadows National Wildlife Refuge — the river supports endemic species that depend entirely on springs fed by groundwater aquifers. 

However, some of those aquifers are extremely close to the surface, meaning even shallow drilling in the Amargosa Basin groundwater system can have severe, unpredictable, and far-reaching impacts.

The request comes after Canada-based Rover Critical Minerals’ (formerly Rover Metals) announced a new plan last year to drill as many as 21 boreholes less than a mile from the refuge — at depths of up to 150 feet — in search of valuable lithium deposits. The proposal included plans to drill within a few thousand feet of Fairbanks Spring, a critical habitat for the endangered Ash Meadows Amargosa pupfish and the Ash Meadows speckled dace.

“Recent proposals for exploratory mineral drilling and extraction near the Refuge boundary pose an immediate threat to the integrity of this fragile ecosystem,” reads the letter.