State scientists are trying to find the cause of a jump in nitrogen levels in an unexpected source -springs on the north side of the Snake River Canyon.

One spring that feeds fish farms run by Clear Springs Foods north of Buhl has tested above state and federal nitrate limits of 10 parts per million, leaving state and company officials working to figure out where the spike came from and what its effect might be.

Overall, levels in the facility's springs are still low, said Randy MacMillan, Clear Springs vice president of research and environmental affairs. But in early October, one water source fed by several combined springs tested at 13.14 ppm, while two others tested between 6 and 7 ppm. Levels in the springs have steadily increased over the past few years - the highest one tested just below 10 ppm in October 2007.

The company, which tests its springs monthly, brought the results to the attention of the Idaho Department of Environmental Quality. The agency is now doing its own tests in an attempt to determine what caused the spike, said Bill Allred, regional administrator.

Officials said they think the measurements just show an isolated spike and aren't a sign of a larger problem. But they still seemed surprised by the increase in an area that traditionally hasn't been an issue.

State officials largely focus on 32 nitrate priority areas considered the bigger problem, said Joe Baldwin, a hydrogeologist with DEQ's state technical services division. The agency doesn't have the budget to regularly test the springs, he said, and leaves those to the fish hatcheries and other spring users.

The agency is putting the Clear Springs readings and others taken from the Springdale area in Cassia County through extra tests that look for various drugs and chemicals in the water, hopefully allowing investigators to tell if the nitrogen came from human, animal or other sources, Allred said. If the tests work, he said, DEQ may begin using them more often - though they are slightly more expensive.

"There's a lot of promise in this," he said, describing how both sites are also areas where DEQ stands a good chance of pinpointing the source of the contamination.

State reports on nitrate problems already point to irrigated farmland, confined-animal feeding operations, septic tanks and nutrient-rich wastewater as the main sources of contaminants. But pinpointing exactly what source caused a certain reading is harder in the maze of groundwater under Idaho.

Most of southern Idaho east of the Thousand Springs area is served by the Lake Erie-sized Eastern Snake Plain Aquifer. But smaller aquifers also sit higher up in the ground, formed from irrigation runoff and other sources over the years.

No one's sure yet which aquifer feeds the problem spring at Clear Springs, though MacMillan said it sits higher up the canyon wall than the others. By the time the water is measured, it's mixed in with several other springs - meaning the actual source of the spring may test even higher. The actual water that flows into Clear Springs' raceways only tests at 6 ppm.

At that level, the company isn't sure what effect the springs are having on its product. Nitrogen tests measure both nitrite and nitrate, one nitrogen atom paired with either two or three oxygen atoms, respectively.

High nitrate levels are linked to health issues in humans and animals, including a condition that prevents blood cells from carrying oxygen around the body. Nitrite, on the other hand, is dangerous to fish, MacMillan said. It can cause a condition similar to nitrate, and can also build up in the gills, potentially causing health problems down the line, he said. Though humans can convert nitrate to nitrite, it's not clear whether fish can, a skill that would exacerbate the problem.

"We're working to try to see if it's had an impact," MacMillan said. "We just don't know yet."

Nate Poppino may be reached at 208-735-3237 or npoppino@magicvalley.com.