SALMON FALLS CREEK RESERVOIR -- There's something in the water here.

And, in the air.

You might expect to find high levels of mercury in water bodies near mining operations -- not at a remote reservoir southwest of Twin Falls near the Nevada border.

But state and federal tests at Salmon Falls Creek Reservoir reveal mercury at levels 180 times greater than what is considered relatively normal. Mercury is a pollutant that causes neurological damage in humans and poses an elevated threat to pregnant women and infants.

Idaho has no major sources of mercury emissions -- a fact that has raised a lot of questions among the state agencies and environmentalists even though mercury can occur naturally in soil.

Air quality monitoring at the reservoir is giving officials a short list of potential sources.

It's in the water

"These are some of the highest numbers we've seen," said Michael McIntyre, surface water program manager for the Idaho Department of Environmental Quality, of mercury concentration levels in the water.

DEQ, together with the U.S. Environmental Protection Agency, are involved in a comprehensive mercury testing program at Salmon Falls Reservoir. Between the two agencies, mercury levels in water, air and soil will be sampled.

In September and October, water samples at various spots along the reservoir came back with mercury concentrations ranging from 0.54 nanograms per liter to 2,926 nanograms per liter. Somewhere around 16 ng/L begins to be a concern for McIntyre.

"It's elevated relative to aquatic and human health," he said.

In November, the department also will test for methylmercury, the chemical that mercury can transform into in the water. The toxin becomes a concern to humans when they eat fish with high concentrations of methylmercury. Two reservoirs in southern Idaho -- including Salmon Falls Creek Reservoir -- contain levels of mercury high enough to warrant fish advisories, warning residents to limit fish consumption.

Mercury transforms into methylmercury ingested by fish at different rates depending on the water body, said Don Essig, also with IDEQ. While the levels of mercury at Salmon Falls are admittedly high, the agency isn't sure yet if those concentrations show up in the fish.

"We're trying to figure it out," Essig said.

Results from testing the tissue of fish taken from the reservoir are expected shortly.

It's in the air

Preliminary results from two weeks of air quality monitoring near Salmon Falls show that the source of mercury in the reservoir just might be gold mines in northern Nevada.

"When the wind is blowing out of northern Nevada, it shows we're getting elevated levels of mercury," said Mike Dubois, an air quality specialist with the DEQ.

During those episodes, Dubois said, testing shows levels of mercury four times the normal background level of mercury in the air.

"We're feeling pretty confident about that correlation," Dubois said.

But two weeks' worth of air pollutant testing isn't nearly enough to definitively link the two. The EPA wants to see testing of mercury near the Nevada mines, said Madonna Narvaez, an environmental engineer and air toxics specialist with EPA's Region 10. If testing at the mines reveals only the long-lived form of mercury -- a form that generally floats in the atmosphere for long periods of time -- then the agencies will need to start looking for another source. However, if the type of mercury is one that deposits quickly, then the mines will remain the chief suspect.

"It's possible there are other sources," Narvaez said.

Mercury emissions from gold mines are not regulated under the Clean Air Mercury Rule, Narvaez said. The federal law, currently up for reconsideration, imposes limits on coal-fired power plants such as the 600-megawatt facility proposed by Sempra Generation for Jerome County.

Continued testing, questions over funding

EPA has provided funding for some aspects of the program while DEQ provides the manpower. Together the agencies will study mercury levels for a year in the soil, water and air at Salmon Falls.

"We don't know what happens during the season," Dubois said. "We're trying to capture every possible input."

Last year, the Idaho Conservation League threatened to sue the EPA if the agency did not begin regulating mercury emissions from gold mines. The environmental group suspects that mercury emissions from the mines blanket southern Idaho, creating elevated mercury levels in Salmon Falls Creek Reservoir.

The Conservation League remains in a "wait-and-see" mode regarding the lawsuit, said Justin Hayes, program director. The state of Nevada is drafting a plan to address mercury emissions from gold mines.

In the meantime, the DEQ, the Idaho Department of Health and Welfare, the Idaho Department of Fish and Game, the EPA and the U.S. Geological Survey collaborate on the state's fish advisory program.

"We usually try to look at sources that have never been tested," said Tom Shanahan, spokesman for the health department.

In the near future, the health department will be testing fish from American Falls Reservoir and Priest Lake for the first time, he said. However, there are water bodies in southern Idaho and around the state that go untested for mercury.

"The program doesn't have any funding for it," Shanahan said.

Times-News reporter Michelle Dunlop can be reached at 735-3237 or by e-mail at mdunlop@magicvalley.com.

How mercury emissions from power plants threaten humans: * Concentrations of mercury in the air tend to be low and pose little concern. * When mercury enters the water, it can become a more soluble form of mercury, called methylmercury. * Fish consume the methylmercury through their gills, allowing the chemical to accumulate in fish tissue. * The danger to humans comes in eating contaminated fish. * Commercial fish generally have lower levels of methylmercury than do noncommercial fish. * Fish that feed off of other fish -- such as bass -- accumulate greater concentrations of methylmercury, thus posing a greater risk to humans. * Exposure to high levels of mercury has been associated with serious neurological and developmental effects in humans. * These effects can include: subtle losses in sensory or cognitive ability, tremors, inability to walk, convulsions and death. * Developing fetuses and young children are especially susceptible to the effects of methylmercury. Source: U.S. Environmental Protection Agency

Mercury advisories for Magic Valley water bodies * C.J. Strike Reservoir -- The Idaho Department of Health and Welfare advises young children, nursing or pregnant women to consume weekly no more than one meal of fish caught from this reservoir. However, there is no restriction on fish consumption for the general public. * Salmon Falls Creek Reservoir -- Young children and nursing or pregnant women should limit fish consumption to no more than one meal per month from any species -- except rainbow trout --caught from this reservoir. Rainbow trout are safe to eat. The general public should limit consumption to no more than two meals a week of bass or walleye. * Note -- Health and Welfare considers four ounces of uncooked fish a meal for children under the age of 7. For everyone else, a meal constitutes eight ounces of uncooked fish. Source: Idaho Department of Health and Welfare