DES MOINES, Iowa (AP) – Des Moines Water Works plans to double the size of the nitrate removal facility that treats drinking water from the Raccoon and Des Moines rivers. The Des Moines Register reports the utility’s board this week approved an $800,000 design contract. The utility expects to spend $15 million on the project, and officials say the new equipment and the cost to operate it will require bigger future rate increases.

The utility had sued three northern Iowa counties, accusing them of allowing agricultural drainage districts to send nitrate pollution into the rivers. The lawsuit sought damages for the money the utility has spent to remove the nitrates.

A federal judge dismissed the lawsuit March 17, saying Iowa’s water quality problems were an issue for the Iowa Legislature.