Tests by the farm industry group Agriculture’s Clean Water Alliance found that more than half of the 45 monitoring sites on the Raccoon River had the highest nitrate level of the past decade. The Boone River also had high levels, the group reported. The association noted that several conservation projects are underway along the Raccoon to attempt to reduce pollution. High nitrate levels, which can suffocate babies and have been associated with other illnesses, have forced Des Moines Water Works to run a nitrate-removal system it is looking to expand. The utility this year sued three northwest Iowa counties, contending that their drainage district should be subject to federal permitting requirements.