P.O. Box 33a
1000 Wilkes-Barre Street
Wilkes-Barre, PA 18703
570.820.9872 (office)
570.825.5039 (fax)

Combined Sewer Overflows

What is a Combined Sewer Overflow?

The sewer collection system of the Wyoming Valley Sanitary Authority, like many older systems, carry both wastewater (used water and sewage that goes down the drain in homes and businesses) and storm water (rain or snow that washes off streets and parking lots).  In many parts of the Wyoming Valley, the mixed waste water and storm water flow together in a single pipe.  This is called a Combined Sewer System.  During a heavy rain, the pipes may get too full and start to overflow into the Susquehanna River or local creeks. When this happens, it’s called a Combined Sewer Overflow (CSO). This provides a “safety valve” that prevents back-ups of untreated wastewater into homes and businesses, flooding in city streets, or bursting underground pipes.

The Combined Sewer System was built as the Wyoming Valley grew during the early 1900s, as an economical way to handle wastewater and storm water. One advantage of this system is that, most of the time when rainfall is low to moderate, both the storm water and wastewater go to the treatment plant before being discharged to the Susquehanna River.

Are CSO’s a new problem?

No. When the combined sewer system was designed over 100 years ago, it was less expensive than building two entirely separate systems of pipes and tunnels to carry storm water and wastewater. Before the sewage treatment plants were built, all sewage and storm water was discharged into the nearest body of water.

The CSO locations were left in place when the present sewer system was updated to act as safety valves when the pipes get too full to handle the high volume of water during heavy rains. The advantage of a combined sewer system is that both storm water and wastewater are treated most of the time. The disadvantage is that during heavy rains, untreated storm water and wastewater may be discharged at CSO locations. In fact, there are far fewer overflows now than in the past due to construction projects to control the overflows.