The Allegheny County Health Department issued the year's first combined sewer overflow alert today.
The Health Department advises those who have weakened immune systems or open wounds to avoid contact with waterways during these alerts, due to a higher risk of infection.
ACHD spokesman Dave Zazac says the CSO alert doesn't mean people have to cancel their river outings, but they should be aware of the high level of sewage and rainwater that has flowed into the area's rivers and streams.
Zazac says a CSO alert is common during extensively rainy weather, like what the region has experienced over the past week. He says it results from sewage system overflow that spills into waterways.
"If the very largest sewage treatment plant, which is our ALCOSAN plant, is in what we call 'bypass,' or in CSO, then there's a good chance that other, smaller sewage treatment plants along the rivers are also discharging their sewage into rivers and streams," says Zazac.
Marinas, docks, and other riverside sites will fly orange flags with the letters "CSO" on alert days. There are 30 such sites in the county: 16 on the Allegheny River, seven on the Monongahela River, six on the Ohio River, and two on the Youghiogheny River.
Zazac says it's common for the alerts to last several days. There were nine combined sewer overflow alerts in 2010.