Paul Woods is a USGS limnologist and has been employed with the U.S. Geological Survey for more than thirty years. He began his initial studies on Coeur d’Alene Lake in 1987 and is currently involved in a three year study that started in 2004.
Q: Why does Coeur d’Alene Lake fascinate scientists?
A: Coeur D’Alene Lake has two fairly unique situations: It has a lot of metal contamination from the Silver Valley Superfund site; and it has a lot of nutrient input from development in the water shed. We’re looking at how those two processes interact into the future; and as cleanup in the basin goes on, whether that’s going to be a really good thing or there are some unanticipated problems that might occur because of those cleanups. Our sampling and modeling of the lake is directed toward answering those questions.
Coeur D’Alene Lake is the most fascinating lake I’ve ever worked on because of this interaction of metals contamination and nutrient enrichment, and just the level of studies that we’ve been able to participate in here, and the type of mathematical models we’re developing. It’s an exciting lake for a limnologist to be working on.
Q: What is the thing that should concern folks the most about this lake?
A: The main problem that the environmental groups are worried about is if the lake receives a lot more nutrient inputs so that the metals that are now stored in the lake bed sediments would be released back into the water column, and the lake would end up being high in metal content just like the Coeur d’Alene River is.
"There’s about $300,000,000 worth of silver sitting in the bottom sediments in this lake."
The contaminated sediments are basically throughout about 85% of the lake, fairly evenly distributed, very high concentrations, as high as some of the most polluted rivers and lakes in eastern Europe. But mostly the sediments and the metals in them are sitting there and not doing too much. There is metal leaching out of the lake bed into the water column, but it’s not going very far into the water column.
Q: But the lake looks so clean.
A: Right. That’s been a difficulty of getting the public to support cleanup of Coeur d’Alene Lake because it does look so good; and actually in the water column for humans, it is clean. There are no metal concentrations that are human health issues; but, again, the bottom sediments are some of the most contaminated in the world. That means there’s not a fishery down on the bottom or the organisms that fish eat.
But part of what people need to understand is that with what has gone on in this lake, having problems years ago, those problems could come back if the lake isn’t managed to keep its nutrient income at a safe level. And that’s what a lot of these studies are about, is letting people know what levels of prevention and maintenance are needed to maintain the lake’s water quality.
Q: How many dollars worth of metals are at the bottom of this lake?
A: We know what the mass of the metals, the amount of the metals are, in the lake bed sediments. And in the case of silver, which is what the Silver Valley was all about, there’s about $300,000,000 worth of silver sitting in the bottom sediments in this lake. Of course you’ve got to understand, to recover those metals would cost way more than the money you could get for it, but it’s just interesting that there is that much in the bottom.
Q: What’s the worst case scenario?
A: One of the central issues in maintaining the lake’s water quality is to make sure there’s enough oxygen dissolved in the water column, especially near the bottom, because there are chemical reactions with lots of oxygen that keep the metals and the nutrients in the bottom sediments.
The worst case scenario would be if something were to cause those oxygen levels to drop dramatically, that would remove that suppressive effect that is keeping the metals and nutrients in the bottom sediments. That’s what a lot of our studies and the lake model we’re developing are aimed at, is determining how we can make sure that oxygen is maintained in the lake bottom area.
"It is the most fascinating lake I’ve ever worked on because of this interaction of metals contamination and nutrient enrichment."
I’ve worked on lots of lakes that have numerous problems, and it’s always more expensive to fix them if it’s possible than to do little things to prevent them from happening in the first place. And this lake has a history of nutrient problems. Back in the mid 1970’s this lake had algae blooms and low oxygen content, lots of water quality problems that we’re trying to prevent now. And again, that’s what this whole idea of lake management is about, to maintain the lake’s current water quality at the high level that it is at.
Q: What agencies are working on this problem of nutrient levels in the lake?
A: The Coeur d’Alene Tribe is just one of many groups involved in the lake. The Tribe now owns the southern third of the lake, officially and they are pretty aggressive in maintaining water quality there. Of course, the state of Idaho through the Department of Environmental Quality is responsible for the lakes water quality; so is the Environmental Protection Agency, Fish and Wildlife Service, and Fish and Game. So there’s a whole group of agencies that are responsible for various aspects of the lake’s water quality and management.
Q: Is part of the problem too much development around the lake?
A: One of the important things that is being developed here in the Coeur d’Alene Lake Basin is a Lake Management Plan. And that requires a fair amount of money, probably some new ordinances, things like that to probably put a little bit of a check on development. Maybe we have people quit doing some things that they have done in the past; and that has produced a fair amount of friction between environmental groups and development, because there is a lot of money being made here. That doesn’t preclude the opportunity for those groups to work together; and what has happened at Lake Tahoe is a great example of folks having a common vision about saving their lake, and maintaining their lake. That’s something that still hasn’t evolved here in Coeur d’Alene at the level that it has at Tahoe, but I think it slowly is doing such.
Q: What is the relationship between the EPA and Coeur d’Alene Lake?
A: One thing that has been a bit confusing for folks is, how does Coeur d’Alene Lake itself fit in with the Superfund site that has been designated here in the Coeur D’Alene Basin? Actually, the lake is part of the Superfund site; but the remedy that has been selected for the lake is basically the development of a lake management plan. So EPA is hoping that the state and the Tribe can come together to have an institutional control program for managing the lake and keeping the metals in the lake bottom sediments. So that’s basically where the lake fits into the Superfund site.
Q: How complicated is the research that’s going on in this lake?
A: I’ve been working with some Australians from Perth,and they are just fascinated with Coeur D’Alene Lake from a scientific standpoint. They’ve worked on lakes all over the world; but they’ve made a huge commitment to work here and help us develop a model. And part of it is the history and the interaction and just how complex this lake is. That’s been very gratifying, to be working on a lake that has attracted so much interest.
One of the reasons I haven’t retired when I could have is the mathematical model that is being developed for the lake by the US Geologicalal Survey and the Idaho Department of Environmental Quality and the Australians. It’s probably going to be one of the more complex water quality models ever developed for a water body; and that’s been very exciting to be allowed to work on that; and we’re actually getting contacts from scientists throughout the world asking about what’s going on in Coeur d’Alene Lake.
So in some ways we could even turn Coeur d’Alene Lake into an international research site beyond the metal contamination issues – just about development of sampling methodologies to support these types of models we are developing. So that’s probably the main reason I’ve stayed working.
Selling this complex water quality model has been difficult with some groups because it is so complex, it’s hard for people to understand the mathematics. It’s even challenging to myself and the Australians who are working on it.
One of the big issues is this: as the metals are cleaned up in the Superfund site and upstream of the lake, the metal concentrations in the lake will become less. But those metal concentrations in the lake right now are one of the reasons that the lake’s biological production is being held down. There’s actually a slight poisoning effect.
So the scenario is, as the metal concentrations come down, and that lid on productivity is lifted, is the lake going to bloom into this much more productive system like we had in the mid ‘70’s? And a lot of the model is oriented toward determining, if you reduce metals by 50%, do you have to reduce nutrients or can you leave them where they are?
And this model is designed to be able to look at that and guide people on what management decisions are going to work.
Q: Ten years from now, do you think this will still be one of the world’s beautiful lakes?
A: Yes. The contamination in the bottom sediments will still be there; but if we are careful about lake management and keeping nutrient inputs to the lake in check, I think we’ll still have the metals sequestered in the bottom sediments where they belong.