Monona City - WI issued the following announcement on May 12.
Crews have begun the spring flushing of water mains throughout the City. When flushing, crews open fire hydrants to flush water through the water mains which causes the water to appear cloudy or discolored from the release of minerals. The water is safe to drink, but if the water is cloud, residents are advised to run their COLD water tap nearest their water meter until the water runs clear.
Crews flush the mains as time permits. If you notice that your water is discolored, visit mymonona.com/hydrants to see if they've been flushing in your area.
Original source can be found here.