DAVID PITTAssociated PressDES MOINES, Iowa - The general manager of Des Moines Water Works said Tuesday the agency might be forced to sue the government if state regulators and the U.S. Environmental Protection Agency fail to limit the nitrate levels that enter rivers from farm field fertilizer runoff.Bill Stowe joined members of the citizen activist group Environment Iowa at the Capitol to call for legislation that would set state standards to limit farm field runoff and fine violators.The group presented Iowa Sen. Dick Dearden with a petition including 5,000 signatures from Iowa residents calling for legislative action to reduce the amount of nitrate and other pollutants in the state's rivers and streams. Dearden is chairman of the Senate Natural Resources Committee.The Des Moines Democrat said it's important for the Legislature to provide funding for environmental programs including conservation measures that help filter out contaminants. He said it is unlikely that a bill including mandatory restrictions on runoff would pass."I don't see it happening but we can keep the issue out in front of the voters," Dearden said.Stowe, who manages the Des Moines-based municipal water treatment plant that serves about 500,000 residents, said he has spent $500,000 in the last two months to run a system that removes nitrate from water. It continues to run at a cost of about $7,000 a day.The EPA says drinking water should remain below 10 milligrams per liter of nitrate to be safe but the Des Moines and Raccoon rivers, which Des Moines Water Works draws from for source water, have exceeded that level for two months. The Water Works plant is struggling to keep the drinking water delivered to taps at between 7 and 9 milligrams per liter, Stowe said."Our ability to meet the drinking water standard is perilously close to being violated," he said. "Unless nitrate levels drop we're going to reach a point where the demand frankly outstrips our ability to treat it safely and that's a huge issue for us."The EPA requires city water systems that go over 10 milligrams per liter to inform the public about the safety risks. Water above that level can be deadly to children younger than 6 months old 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.Stowe said such a notification to the public would be devastating because it would erode residents' confidence in their drinking water. He said it would be "a serious economic and a long-term issue for us that we simply won't tolerate."He said if Iowa policymakers fail to regulate farm runoff and the EPA doesn't enforce the Clean Water Act in Iowa, Des Moines Water Works might have to file a lawsuit seeking the establishment of standards limiting runoff and enforcement of them.The nitrate in the rivers comes largely from the fertilizer and hog manure applied to farm fields to grow corn.Kris Lancaster, EPA spokesman for the Midwest region that includes Iowa, said the agency believes the state's new nutrient reduction strategy enacted May 29 will yield measurable reductions in runoff of chemicals from farms and other sources including wastewater treatment plants.He said the EPA supports states leading efforts to reduce pollution from rivers and streams, and is not mandating specific practices or solutions."The people of Iowa know best what practices will reduce nutrients to waters while maintaining an economically viable ag industry," Lancaster said in a statement.Iowa Department of Agriculture spokesman Dustin Vande Hoef said it's unfortunate that some critics continue to attack rather than try to work with agriculture to improve water quality."Lawsuits and more government regulations don't reduce nitrates and phosphorus," he said in a statement. "This has been a record-setting spring for precipitation in Iowa and we have more work to do and we look forward to continuing to work with partners on this important issue."