Nitrate levels hit record highs in 2 D.M. rivers
Nitrate levels at record highs in the Des Moines and Raccoon rivers over the past three months have forced the Des Moines Water Works to again use its nitrate removal facility, the agency said Thursday.
"Des Moines Water Works staff has employed extensive efforts to mitigate nitrate levels, but ... we were left with no alternative but to activate the nitrate removal facility," said Bill Stowe, CEO of Des Moines Water Works, in a statement.
Nitrate levels in September, October and November were the highest ever experienced in those months and "have required extraordinary efforts," the agency said. "Use of the nitrate removal facility is the last step available to maintain safe drinking water."
RELATED: Raccoon River nitrate level peaks
Higher concentrations of nitrates are more common in the spring, when excessive rain washes unused fertilizer from farm fields into streams.
The agency used the nitrate removal facility for 74 days in 2013, an effort that cost consumers about $900,000 in treatment costs and lost revenues.
Untreated high levels of nitrates in drinking water have been linked to blue baby syndrome, when a baby's blood can't carry sufficient oxygen, as well as to various cancers and miscarriages. The federal limit is 10 milligrams per liter nitrate in drinking water.
Current nitrate levels in the Raccoon River are 12.62 milligrams per liter, the agency said, and 11.63 milligrams per liter in the Des Moines River. With extensive treatment, the city's finished drinking water currently has a nitrate level of 8.79 milligrams per liter, the agency said.
Nitrates occur naturally in the soil but can spike in water when manure and other fertilizers drain off lawns and farm fields and into waterways.
Stowe said the state's voluntary Nutrient Reduction Strategy, designed to reduce the amount of nitrogen and phosphorous that leaves farm fields, isn't working.
The state has pledged to reduce by 45 percent the nitrogen and phosphorous that enters waterways and contributes to high nitrates in cities such as Des Moines and to the dead zone in the Gulf of Mexico. But the effort is voluntary, and there's no timetable to reach the goal.
"Continued but unfounded insistence from state leaders that the voluntary approach of the Iowa Nutrient Reduction Strategy is working does not give solace to the 500,000 central Iowans who must now pay to remove pollution from their drinking water," Stowe said.
"Further, the persistent argument that 'weather is to blame' for this situation is wrong," he said. "Science proves weather and other natural conditions do not create excessive nitrate concentrations. Intensive land use and extensive agricultural drainage systems are the source of the high nitrate in our source waters."
But the Iowa Farm Bureau said the weather did contribute to the high nutrient levels in state waterways.
Iowa had above average rainfall amounts in September and October, a state report shows. It was the 40th wettest September in 142 years of records, and the 35th wettest October.
The weather delayed harvest and limited how much nitrogen was applied to fields this fall, said Rick Robinson, an Iowa Farm Bureau environmental policy adviser.
"It is most likely that the wetter, milder temperatures this fall have contributed to the unusual movement of nitrates in the Raccoon and Des Moines rivers from a variety of sources," he said. "Most reports from agronomists and co-ops are that only 25-50 percent of planned fall fertilizer was applied."
Despite the recent spikes, Robinson said nitrate levels are trending downward in the Raccoon and Des Moines rivers in the past 15 years.
Craig Hill, the group's president, told members this week at an annual convention that the Nutrient Reduction Strategy is working, with a "record number of conservation practices put in place."
"It's only the
beginning of a new effort, and it's an enormous investment by farmers," he said.
Officials have said the $4 million nitrate-removal plant, installed in 1992, costs about $7,000 a day to run. The Environmental Protection Agency had ordered Des Moines to act to remove nitrates after the contaminant exceeded the federal limit in tap water during the early 1990s.
Before starting up the facility Thursday, the agency said employees managed high nitrates by blending various water sources, including from a shallow groundwater collector system, Maffitt Reservoir, Crystal Lake, and aquifer storage and recovery wells.
In 2013, nitrate levels reached 24 milligrams per liter in the Raccoon and 17.87 milligrams per liter in the Des Moines.
Recent levels
The nitrate levels in the Raccoon and Des Moines Rivers this fall are unprecedented for this time of the year, Des Moines Water Works says. The monthly averages are as follows:
Raccoon RiverDes Moines River
September 11.61milligrams per liter 7.20 milligrams per liter
October 2014 13.23 milligrams per liter 11.15 milligrams per liter
November 2014 13.25 milligrams per liter 11.88 milligrams per liter