The Washington Suburban Sanitary Commission says crews are trying to fix a broken sewer pipe that's causing untreated wastewater to flow into a creek in Upper Marlboro.
The utility says the overflow is not affecting the drinking water supply.
The overflow was first discovered Friday night. The utility says the bed of Charles Branch Creek beneath a 24-inch sewer main deteriorated, undermining support of the pipe to the point where it ruptured.
The wastewater is flowing from the broken sewer down the creek and then going back into the sewer system through a manhole opening.
Crews are working on a pump that will bypass that section of sewer main. The rupture occurred in a remote, wooded area, requiring crews to build a temporary access road.