Eighty-five percent of Atlanta’s sewers are separate sanitary sewers.
Beyond the 19-square-mile combined sewer area, in the separate sanitary sewer system, sewage
flows in its own pipe to the City’s water
reclamation centers (WRCs) for treatment, and stormwater
flows in a separate pipe to a receiving stream. However,
like many older cities, much of Atlanta’s sanitary
sewer system is aged and in need of rehabilitation. Cracked
and leaking pipes, built to handle sanitary sewage alone,
and storm water as well, increasing the volume of flow in the
pipes. In addition, as a result of Atlanta’s growth,
the sewers are receiving sanitary sewage volumes greater
than anticipated when they were originally constructed.
Improper connections at residences and businesses also allow
stormwater to enter the sanitary sewer system. Consequently,
these sanitary sewer systems are strained beyond their capacity
and experience sanitary
sewer overflows – or SSOs.
During SSOs, a mixture of untreated sewage, groundwater
and stormwater overflows from the pipes or from manholes
connected to the pipes. Many sewer lines run alongside creeks
and streams. When SSOs occur, the overflow goes directly
into those creeks and streams, which may cross private property.
Excess sanitary sewer flows also stress other pipes, pump
stations and manhole covers, and wastewater treatment facilities.