DES MOINES, Iowa (AP) — Two rivers that supply water to 500,000 people in the Des Moines area show nitrate levels spiking to levels that make it unsafe for some to drink, a concentration experts haven't before seen in the fall that likely stems from especially wet weather in recent months.
The utility that supplies Des Moines and most of its suburbs had workers blending river water with other sources to lower the nitrate levels, but the situation may be nearing the point at which the city starts a process that costs about $7,000 a day to remove them. If that happens, the utility has threatened to sue the state.
On Friday, the nitrate level in the Des Moines River was at 12.8 parts per million and the Raccoon River was at 13.7. The U.S. Environmental Protection Agency requires officials to inform the public about safety risks at 10 parts per million.
Iowa and other states often have problems with nitrates in the spring, when rain washes unused fertilizer from farm fields. But it's unheard of to have spikes so high in November, said Des Moines Water Works CEO Bill Stowe. Scientists believe the current problem is caused by wet weather in the late summer and fall, which sent nitrogen remaining in the soil washing downstream.
"What we're seeing are numbers late into the fall and into the early winter like we've never seen before," Stowe said.
Stowe said so far workers were keeping the drinking water at just over 8 ppm. Water above 10 ppm can be deadly to children younger than 6 months because the chemical can reduce the amount of oxygen carried in their blood. Pregnant women and adults with reduced stomach acidity are advised not to drink water above the EPA limit.
In spring 2013, nitrate levels hit all-time highs on both rivers when a wet spring washed nitrogen from fields after a severe drought. Water Works mechanically cleaned the water at a cost of $900,000 until nitrate levels subsided more than two months later. If it happens again, Stowe said the utility likely will sue, alleging the state is violating the Clean Water Act by failing to reduce the nitrogen levels in rivers.
Monitors in rivers throughout the nation show no other sites with such high nitrate levels. But the issue is especially severe in parts of Iowa given the intense farming and tiling of land. More than 2 million acres in west-central Iowa drain into the Raccoon River, most of it cropland or livestock farms. An estimated 78 percent uses man-made drainage tiles to quickly move water downstream.
Although Iowa began a voluntary program in May 2013 that encourages farmers to make changes to reduce runoff, Stowe and environmental groups argue that strategy is toothless and lacks measurable benchmarks or a timeline for improvement.
For years, environmental groups have called for the state to regulate livestock farms, much as they already do for city wastewater treatment plans, which must have permits that limit release of contaminants into rivers. They're also seeking ways to measure and limit the release of nitrates from fields where tile has been laid underground.
Iowa DNR spokesman Kevin Baskins said the state acknowledges the need to improve its waterways, but that it will take time for voluntary efforts to work. He said farmers are beginning conservation practices and government grants are giving them incentives.
"This isn't something where you just get instant results," Baskins said. "We didn't get into the kind of situation we have today in terms of excess nutrients overnight and we won't get out of it overnight."
Significantly reducing nitrogen levels likely requires slowing the flow of water into rivers by setting up wetlands or planting grasses or other cover crops on harvested fields, allowing the plants to retain water and consume excess chemicals.
"We have millions of acres on which we need to implement this stuff," said Chris Jones, an environmental scientist with the Iowa Soybean Association who has studied the Raccoon River. He said fixing the problem would cost billions of dollars.