Ground and surface water flows in but much of it is lost to the air at abandoned mine pit lakes. As a result, the state’s most important resource is being wasted and legislators should do something about it according to Great Basin Resource Watch Executive Director John Hadder.
“We think that any new mine needs to have a plan for post-mining use of the pit lake,” he recently told the Mining Oversight and Accountability Commission. “What is going to be the beneficial use of that water? Establishing a beneficial use will provide clarity for what is the pit lake water quality to be required and the standard to be met.”
Under current mine plans, about 1.4 million to 1.5 million acre-feet of water could end up in pit lakes, Hadder said. That’s “almost three times the Las Vegas annual consumption.” Rye Patch Reservoir in Pershing County can hold up to 213,000 acre-feet of farm irrigation water, he said.
“There’s evaporation from this pit lake water as well,” he said. “We’re estimating that to be about 13,000 acre-feet per year and that’s gone forever.”
Hadder recommended the commission hold public hearings to help regulators determine beneficial uses for pit lakes “so the directly affected community can provide their top uses.”
“How do they want to see the pit water used? Do they want the mining pit water to be drinking water quality? Do they want it to be for irrigation or recreational use? What are the needs of the community and the people where the mine is located? The public process is very critical.”
After mining stops, the Nevada Department of Environmental Protection requires revegetation and contouring to minimize soil erosion but pits can remain on the land.
Pit walls exposed to air may contaminate any water in the pits and years of treatment are required to neutralize the acidity. Pit lakes are mostly abandoned as the water evaporates.
An exception is the Sparks Marina, an old gravel pit that is now a recreation area with sailing, windsurfing, swimming, scuba diving, fishing, trails, waterfront apartments and restaurants. The Helm’s Pit required years of cleanup due to underground leaks from an oil tank farm. Now, millions of gallons of clean groundwater flow daily into one of Sparks’ primary attractions.
“Here’s an example of a pit lake that is of use,” Hadder told the commission. “This is the Helm’s Pit, now the Sparks Marina. This was a gravel pit, not a hard rock mine pit so the water quality issues were not as significant early on but it’s an example of a post-mining use of a pit lake.”
The Sleeper Pit Lake is salty but could be considered safe for fish, wildlife and water-loving humans with the potential for recreation or other beneficial use, according to Hadder.
“Today, treatment has been done on the Sleeper Pit Lake and it possibly could be used for a recreational reservoir,” he said. “Maybe other uses are possible for this one.”
Lime and trona treatments continue at the Lone Tree Mining Pit Lake due to high acidity as a result of pit walls. Good water quality and beneficial use could be a number of years away.
“This one started to fill and, within a year, the water became very acidic. This is not an uncommon problem,” Hadder said. “The Lone Tree Pit Lake could eventually come around and be non-acidic. Pit lakes can start out very bad but over time they can improve.”
If mining goes below the water table at Relief Canyon Mine in Pershing County, a new pit lake could eventually appear when reinjection wells are removed and the pit fills with groundwater.
Backfilling mine pits, now required in California, can threaten groundwater quality, Hadder said.
“When you backfill a pit, that backfill will infiltrate with groundwater and there’s the potential that water could flow into that backfill and flow out and actually degrade groundwater. This is the reason why NDEP is not allowing Lithium Nevada up at Thacker Pass to go below the water table because of water flowing through the backfill and contaminating the groundwater.”
In an unusual alliance, Pershing County farmers agreed with GBRW years ago that pit lake water should be governed by water rights laws that require beneficial use. The Pershing County Water Conservation District has water rights for Lovelock Valley farm irrigation, a beneficial use.
Hadder argued that beneficial use for pit lakes would allow state regulators to set minimum pit lake water quality standards for mining companies to achieve with long-term water treatment.
“If there’s a beneficial use established for water in the pit lake, then the commission can approve a specific numerical standard to satisfy the beneficial use and that’s the standard the mining company must meet,” he said. “We think it provides more regulatory clarity.”
Hadder asked the commission to clarify a state statute that calls for public access to pit lakes but allows private landowners, and federal land managers, to deny public access anyway.
“We feel the statute doesn’t do much and there’s still a problem with reclaiming pit lakes,” he said. “It doesn’t address use of the water and, if it’s tied to the land, Nevada is unable to completely control what’s going on because we can’t tell the federal government whether to allow public access or not.”
Land owners and land managers control the land but Nevada’s water is a public resource.
“A mining company may own part of the land and they may say no to public access. But, the water is public and Nevada can control that which is why we think beneficial use is the way to go,” Hadder said. “How do we address the water in pit lakes that is of no use to the public?”
Hadder hopes the commission will draft “a beneficial use requirement for mine pit lakes.”
“We are one organization that’s willing to help with this process to develop, with industry and public input, criteria for post-mining uses of pit lakes, including how to provide safe access, beneficial uses, how is it funded and what is the schedule for attainment of that beneficial use?”
The commission may do a “deep dive” into NRS 519A.230 to reconsider pit lake reclamation. NDEP, the mining industry and the public may be asked for input on “how we can do better.”