The pit lake challenge

What’s to be done with water left behind by mining?

Cove pit in Lander County during the early stages of filling. The lake level is higher now.

Cove pit in Lander County during the early stages of filling. The lake level is higher now.

It’s an awesome sight, even though it’s really only a hole in the ground.

An open pit mine is an injury to the Earth that, unlike some other such injuries, is not reclaimed by the planet all that easily. Roads can be overgrown in a couple of years. Open pit mines will be there for centuries.

Some of them go so deep that the mining happens below the water table, the water being constantly pumped out to permit the mining to continue. But always, sooner or later, the mining comes to an end. Then, so does the pumping. The water returns to its natural level, only now it’s a lake.

They’re called pit lakes. There’s not much to be done about them. Mining corporations are not required to replace their divots and it’s not likely the public could afford to do anything about it. Environmental scientist Glenn Miller recalls when someone told him what it would take: “It costs a buck a ton to put the dirt back into the pit. If you’ve got a billion tons of dirt—.” The thought didn’t need finishing.

The scale of the matter is huge, yet is largely unknown to the public. In a 2002 article in Southwest Hydrology magazine, Miller described it:

“Gold-mining pit lakes in Nevada, when filled, will contain more water than all of the reservoirs within the borders of this arid state. An estimated 35 pit lakes from all types of hard rock mining are expected to form, containing from less than 100 acre-feet up to about 540,000 acre-feet of water. On a statewide basis, all of the existing reservoirs within the state (excluding Lake Mead) contain approximately 600,000 acre-feet. In contrast, pit lakes in the Humboldt River Basin alone will contain 1,500,000 acre-feet, and evaporation from their surfaces is expected to remove the equivalent of five percent of the flow of the Humboldt River at Winnemucca each year.”

In a desert state, it’s simply not responsible to ignore that much water. Miller: “Thus, from a water resource perspective, pit lakes are important to Nevada, and the quality of the water in them will determine their future use, as well as their effects on the aquifer, wildlife and ecosystems.”

So, if it’s not cost effective for the pits to be filled, what’s to be done with them, and with the lakes?

Right now, the policy is simple—fence them off. That protects the public from what is, after all, an extremely dangerous aftereffect of mining.

But just doing that and no more troubles some folks.


There are perhaps 70 pit lakes in the state. Some of them are not contenders for public use because of water quality or other factors. Some, because of nearby tampering with water sources or other factors, have gone dry. And some are intermittent lakes that contain water mainly in the cold months of the year.

Scientist Glenn Miller is working to get the issue of pit lakes before the public and policy makers


But some of them could be used for post-mining purposes.

Miller is a leader in seeking new uses for the pit lakes. He acknowledges that the water is not likely to be of drinking water quality, but he doesn’t necessarily concede even that. There are a handful of pit lakes, he said, that approach that level. Nevertheless, most pit lakes will require some expensive work.

“But they’ll probably support a fishery,” he said. “Some of them will be five miles long and if you want to take a jet-ski out or some fun thing like that, or even water sports, swimming, whatever, ultimately a lot of these, maybe not all of them, but a lot of them could be turned into a positive recreational resource.”

In Tuscarora, he said, locals have already put a pit lake to recreational use. In addition, he said, if the residents could divert stream water into it, they could improve the quality of the water so it can be used for irrigation.

The quality of the water is the first thing that occurs to most people when this discussion gets under way.

Montana’s abandoned Berkeley Pit is one of the most dangerous places on Earth. Plant and all but the hardiest insect life are gone and birds that stop there die. The rising water level threatens to enter the groundwater.

But the quality of water is affected by what was mined at a site. When exposed to the air, the walls of pits release sulfate, acid and metals into the lake, and the nature of those walls is important. Berkeley was a copper mine. Not all pit mines present that kind of threat. In Nevada, the huge Kennecott copper pit near Ruth—the state’s largest—will never likely be useful for the kinds of things Miller envisions. But some of the gold mining sites in northeast Nevada can probably be used, if not for drinking water then for recreation.

And one reason the pit lakes may be less threatening than the public thinks is that in a relatively unregulated industry, one regulation that is in place is a requirement that, going in, there must be no potential for a pit lake to adversely affect avian, terrestrial or human life.

That doesn’t mean the gates can be thrown open right now. Even in some of the untroubled sites, the water needs treatment, as with lime, which can reduce the acid level. But in terms of the total dissolved solids (TDS)—a measure of the combined content of all inorganic and organic substances in the water—things are promising.

Instances of pit lakes that responded to water treatment, Miller said, are Lone Tree and Sleeper, pits on the Carlin Trend near Winnemucca. Lone Tree is a Newmont Mining property, Sleeper is held by Paramount.

“Lone Tree was [hazardous], for example, because they’ve been dumping thousands of tons of lime into that … each year and at Sleeper, which was really, really acidic, they’ve got tens of thousands of [tons of] lime into it until it comes up and then it covers all the reactive rock. And then the water turns out to be pretty good.”

Sleeper is one the few Nevada pits whose water is currently ranked by the state as “good.”

There are some uses to which the water can’t legally be put, including human consumption, irrigation or municipal/industrial uses such as power plant cooling. But fish would do nicely.


If the water can’t be used for those kinds of things, would people want to eat the fish that grew in it?

“I wouldn’t have a problem with it,” Miller said. “I mean, Pyramid Lake has a TDS of 5,000.” The normal TDS of drinking water is 500 mg/l.


One of the big problems in exploiting the resource possibilities of these sites is its low visibility, though some state leaders have been trying to bring it onto the state’s radar screen. At a hearing of a state mining oversight committee in December last year, Progressive Leadership Alliance of Nevada director Bob Fulkerson said, “Massive pit lakes containing degraded water will be left behind for centuries or longer. What are the plans for monitoring and ensuring public safety after the mining corporations have left? Are there sufficient funds to manage these sites in perpetuity?”

But even if elected officials, including the legislature, realize the potential, what are the chances that there will be the money to develop a whole new program? It’s hard to imagine a less promising time in Nevada history to launch such an initiative. At the moment, the state ranks four of the pit lakes as having “good” water. The same can be achieved at other sites through treatment, which does not come cheap.

At a meeting on pit lakes last week, Miller spoke with former state legislator Sheila Leslie, who is running for the Nevada Senate. It turned out he had found one policy maker who actually has some hands-on experience with pit lakes. She visited Tuscarora in 1989 during a dispute between a mining company and local residents.

“I remember swimming in a pit lake in Tuscarora,” she laughed. “It was a hot day and it was very refreshing. Later, I wondered if I should have gone into the water.”

She said she’s interested in pursuing legislation that would make it possible to give the public more access. “So, yes, I think there is some potential. I think it’s worth taking a look at.” It would require change in law to allow pit water to be used for irrigation, as one example.

But what approach to take in legislation will have to wait on more information and more dialogue among all the players.

The state Department of Wildlife is in much the same posture. “We are open to the idea of fisheries like these if some of the challenges can be met and overcome,” said Nevada Department of Wildlife spokesperson Chris Healy.

Many of the most promising pit lakes are in the “checkerboard” railroad lands along the Humboldt River/Interstate 80 route, which brings ownership into play. Some are on public lands, others on private. Neither Miller nor state officials see ownership as an obstacle, though they may be overly optimistic. The Abandoned Mine Reclamation Act of 1989 does require that mining sites be put to productive use after the end of mining operations and it’s difficult to imagine how many uses these punctures in the Earth can have.

“After they’re done mining, the surface rights are public land,” Miller said. “And most of these pits in Nevada have at least part of it … on public land.”

He said 32 to 40 percent of gold mining in Nevada occurs on public land and when the mining operations end, residents have a stake in what happens thereafter. Faced by fences on public lands, he said, residents will be within their rights to say, “That’s public land. I want to get down into that area. As a taxpayer, I want to be able to go onto the public land and that fence there keeps me out of it.”

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He said the U.S. Bureau of Land Management is sensitive to that argument and interested in dealing with it, but as in the legislative and NDOW forums, the issue is still uncooked.

Other factors

One asset the state has is access to expertise on pit lakes, such as Nevada Bureau of Mines and Geology hydrogeologist Lisa Shevenell, who has written on the subject for professional publications like Applied Geochemistry and Environmental Geology.

Some of the sites are not particularly close to population centers, which could suggest that they would not draw a lot of recreational use. But many relatively remote reservoirs like Rye Patch are popular recreation sites. An area in northwest Nevada near the Idaho border that was identified by Columbia University’s Center for International Earth Science and the Wildlife Conservation Society in 2005 as among the Earth’s “least imprinted by humans” is also near Wild Horse Reservoir, which has fishing and camping facilities.

There are other issues. The stability of the walls of open pit mines would need study. Some pit walls are known by technical measures to be relatively strong and safe. “There are some you can swim in,” Miller said. “You know, there are some that are stable.” He has swum in one himself.

For others, Miller said, “What we can do is we can wait for 50 years.” It’s not like these sites are going anywhere or are in demand for other uses, so where there is doubt about stability, there is time to wait. “But these impacts are a thousand-year impacts, 2,000, 5,000-year impacts,” he said at one point, putting 50 years to monitor a few of the sites in perspective.

As it happens, slides in mine pits are generally slow-moving, unlike, say, the disastrous 1983 mudslide off Slide Mountain south of Reno. But there are pits where there is serious instability. Miller visited one where a wall had slipped enough that a mine worker said, “If you touch it, it could start sliding again.”

As the years pass, people are going to find their way into the pit lakes. It would be nice if it happened in a safe, sanctioned way.

“Just leaving it fenced around is, first of all, not very productive and second, it’s also an attractive nuisance,” Miller said. “There’s going to be people throw fish in them, and there’s fish in them, people are going to get down in them. Someone was telling me—oh, Dick Chambers, a friend of mine—he said, ‘There’s something about fishermen and gold miners that they’re both pretty passionate people, and they want to get at that gold or fish, and they will stop at almost nothing to get to it.’ And that’s kind of the attractiveness of fishing.”

It would also be nice if the mining corporations that created the pit lakes were a part of any resolution. Miller has said he has heard from some mine officials that they are unwilling to be involved unless they are relieved of all liability. Industry lobbyist Tim Crowley said, “I can’t imagine that wouldn’t be a condition,” but that he has not discussed it with any mining executives.

Miller argues that the corporations, not government, are determining the future of public lands by creating the pits, causing them to be closed.

“When are you going to open up the gates and let the public recreate the public land?” Miller asks rhetorically of the mining corporations. “If you have a mining company that gets not only free minerals but can close off a big chunk of land and fence it off, they’re getting everything for free because they don’t pay any royalties. Then they will effectively have withdrawn the land from public use in perpetuity by putting up a fence. They say, ‘Hey, we’ll even put money in the bank to keep that fence operational in perpetuity.’ My response is, no, because it’s public land and the public has a right to access the public’s land. … It isn’t that expensive compared to what Barrick [Gold Corporation] is—Barrick’s what, 20, 30 billion dollars out of the Gold Strike Mine? This would probably be a few tens of millions of dollars to make it accessible.”

Articles like this normally end with resolution or the potential for resolution. That’s not possible here. This issue has not reached critical mass. It remains a matter being discussed mostly in rarified circles.

“But the bottom line,” Miller said, “is they have the potential of being a valuable resource and if you just fence them around, the fences are going to go away because this is millennium-long impact and people are going to want to get into those pit lakes.”