One-tenth of an inch of rain over an hour is all it takes for the region’s sewers to overflow.
That’s according to the Allegheny County Sanitary Authority (ALCOSAN), which has already issued two Combined Sewer Overflow (CSO) alerts this season. The Authority is hoping that as the river recreation season takes hold more recreational users will take note.
The alerts, which are communicated by email, text messages and orange flags along the three rivers, notify swimmers, boaters and other recreation river-users if the water has been contaminated by raw sewage after heavy rain clogged treatment facilities.
ALCOSAN spokeswoman Jeanne Clark said the authority is able to send out alerts as soon as an overflow is detected at the water treatment plant.
“As soon as we see the level come up of the flow coming into the plant, once we reach a certain level, we know there’s an overflow and we send the information out,” Clark said.
The alerts, which can last anywhere from a few hours to several days or weeks, do not prohibit river use. River-goers are asked to limit direct contact with the water during an alert, especially for those with open cuts or sores.
“If you do wind up in the river and we’re in a CSO situation, you should make sure if you’ve got a cut or anything you need to scrub it really well and probably put some ointment on it,” Clark said. “You need to try to avoid having your eyes or face in the water in those circumstances.”
Clark said, since raw sewage is being diluted into the rivers during an alert, river-goers run an increased risk of being exposed to harmful bacterium, such as E. coli.
ALCOSAN also issues intermediate alerts, which go into effect 48 hours after the high CSO alert. At that point, Clark said boaters and kayakers should be safe on the rivers, but direct contact with the water should still be avoided.
“People should have as much fun on the rivers as possible and enjoy the spring, summer and fall, just be careful,” Clark said.
The number and frequency of CSO alerts has varied every year since their implementation by the Allegheny County Health Department in 1995. Last year, ALCOSAN issued 50 advisories.
Those interested in electronic alerts can sign up on the ALCOSAN website. The authority has also introduced an overflow hotline where anyone can call in and check the status of the rivers at 412-734-6249.
CSO alerts are scheduled to end Oct.31.