STEVENS POINT, Wis (WSAU)  It's been several days since some Stevens Point residents started seeing grey and black sediment in their water. The city says it's an excess of manganese, which isn't harmful to humans. Manganese is naturally occurring, and the water is safe to drink. It could cause some discoloration when doing laundry. The city's water works says it's a temporary situation that was first reported last week. They'd expected the problem to clear up by now. Anyone with questions can call the city at 715 345-5260.