The Maryland National Guard airlifted equipment Wednesday to repair a broken sewer line in Ellicott City that has sent millions of gallons of sewage into the Patapsco River after Saturday's storm.
An estimated 5 million gallons per day have flowed into the Sucker Branch tributary of the Patapsco River, according to Jay Apperson, a spokesman for the Maryland Department of the Environment.
The overflow is one of several reported in the Baltimore area after Saturday's torrential rain that caused flooding in the Howard County town and parts of Baltimore.
The break in Ellicott City was not discovered until Tuesday, Apperson said, and crews have struggled to make repairs because a road washed out. Crews hoped to stop the overflow by Wednesday night.
Officials urged residents to avoid direct contact with the water after several jurisdictions reported large sewage overflows.
Anne Arundel County issued a warning against swimming and other activities involving direct contact with the Patapsco from the Howard County line to the Baltimore City line, along River Road, in Patapsco Valley State Park, and Belle Grove Road.
Anyone who comes in contact with the water should wash well with soap and warm water immediately, and wash clothing.
The MDE will also oversee any work needed to restore and stabilize the stream channel and flood plain, Apperson said.
In Baltimore County, officials reported four sewer overflows, two of which dumped more than 50,000 gallons of sewage into Patapsco tributaries.
Officials said the pumps at the Frederick Road Pumping Station in Catonsville continued to operate during the storm, but the inflow from stormwater exceeded the pumps' capacity, releasing 25,130 gallons into a tributary about a half-mile from Patapsco Valley State Park.
About 31,200 gallons were dumped into the Mardella Branch in Randallstown, Baltimore County officials said. The failure at the Kings Point Pumping Station was caused by debris. Crews were called to the pumping stations by automatic alarms but had difficulty responding because the road to the facility was flooded.
In Baltimore City, officials said about 5.8 million gallons were released. Most went into the Jones Falls, while about 10,000 gallons went into the Gwynns Falls.
Alice Volpitta, a water-quality manager for Blue Water Baltimore, said a sewage stench was noticeable Wednesday along the Middle Branch of the Patapsco. Tests for bacteria in samples collected by the water-quality advocacy group will not be completed for a couple of weeks, she said.
Baltimore Sun reporters Kevin Rector and Scott Dance contributed to this article.