Report: 9 billion gallons of sewage, stormwater overflowing into Pittsburgh’s Three Rivers

Heavier rainfall, aging infrastructure are creating more problems for the rivers

October 19, 2022

Rapid development, heavier rainfall, and aging infrastructure are combining to deliver 9 billion gallons of sewage and stormwater into Pennsylvania’s Three Rivers each year.

So says a report released by PennEnvironment on Oct. 12. Researchers explained that over the past two decades, development across Allegheny County has resulted in a proliferation of “impervious surfaces,” such as rooftops and pavement, where once stood forests that could absorb rainfall. Coupled with heavier downpours linked to climate change, the hard surfaces have meant more stormwater overwhelming the county’s sewer systems and spilling raw sewage into the Monongahela, Allegheny and Ohio rivers.

(This interactive map shows the worst sewage outfalls in the region.)

In response, the Allegheny County Sanitary Authority (ALCOSAN) has proposed a plan, but, said the researchers, it moves too slowly and still fails to stop sewage overflows. PennEnvironment is calling on ALCOSAN to invest in green infrastructure, a more resilient sewage system and open space preservation.