Workers hired by the city halted one of the worst sewage spills in Baltimore history yesterday morning when they completed a temporary 2-mile bypass of two blocked sewer pipes in Herring Run.
The spill, discovered Monday by a passer-by, dumped an estimated 30 million gallons of sewage into the stream, said Kurt Kocher, spokesman for the Department of Public Works.
"Considering the magnitude of the blockages, I'm happy that we stopped it this quickly," Kocher said yesterday. "We're talking about very difficult material to move - large boulders that had to be lifted by three people."
Stopping the spill was the city's first priority, Kocher said, but the blockages that caused the overflow remain in place. Contracted workers will take another stab at clearing the sewer pipes tomorrow, Kocher said, adding that he hoped the pipes would be unclogged sometime this week. The bypass of the damaged lines consists of temporary above-ground pipes.
City workers discovered the first blockage in a 36-inch-wide pipe Monday and found another in a 24-inch pipe Friday.
Public Works officials believe the blockages in the Herring Run interceptor were caused by melting snow and heavy rains. Kocher said swiftly moving water probably dislodged an upstream manhole cover and damaged an "access point" that protrudes above the stream and permits workers to perform maintenance on the pipe. The damage left a 30-inch-wide hole for rocks and debris to enter the sewer pipe, he said.
A contractor will have to rebuild that access point this week, Kocher said, so it will not be vulnerable to continued melting or another major storm.
For much of its route, the 3-foot-wide sewer pipe traces the flow of the stream, and even lays on its bed under the water in some sections. A major trunk line in the city's sewer system, the pipe collects wastewater and transports it to the Back River Sewage Treatment Plant.
Though nearby homeowners and members of the Herring Run Watershed Association have expressed concerns about the environmental impact of the spill, city officials have maintained that the effects will be minimal. The spill will not taint drinking water, said Health Commissioner Peter L. Beilenson in an interview Friday.
Kocher said residents should temporarily avoid the stream and parts of Herring Run Park where workers are clearing the blocked pipe. The work is continuing near Harford Road and Argonne Drive, he said.