DES MOINES, Iowa (AP) – Des Moines Water Works has filed a lawsuit against three northern Iowa counties, alleging they are violating federal law by running drainage systems that contribute to high nitrate levels in rivers the utility uses for source water. Details of the lawsuit against Buena Vista, Calhoun and Sac counties were released Monday. The Des Moines Register reports  the lawsuit was filed Friday and seeks reimbursement after spending $540,000 to operate a nitrate removal facility for 97 days this winter.

Water Works officials say the counties’ 10 drainage districts allow excessive nitrate levels into the Raccoon River, a primary central Iowa water source. In the lawsuit, the utility alleges such systems limit the area’s drinking supply. The law firm representing the counties didn’t immediately respond to a message seeking comment Monday.