Water Quality and Human Contact

Public perception of water quality varies. One man I asked said “there’s nothing wrong with this water; this is fresh clean water. I have been swimming here my whole life.” while another person at the river said “This water quality is so polluted if you try to swim the police will arrest you.” Neither of these views are completely true; at times our rivers are very clean and other times they are terrible, but it is never illegal to swim in the rivers.

Risks to public health and environmental quality result from inadequately treated sewage treatment plant effluent; failure to properly monitor discharge quality; inadequate sludge treatment and final disposal; inadequately trained operators; lack of effectively updated and implemented municipal plans; and sewage systems that are overloaded and poorly maintained with resultant chronic overflows… Many communities are already plagued with discharges to streets, hillsides, and streams with no relief in sight until [better] public sewers become available.

-Allegheny County Health Department http://trfn.clpgh.org/achd/sewage.html

Most people are not aware of our sewage problem; most people believe that water quality issues are about industrial toxins. These kinds of hazards are an issue, particularly in the sediment at the bottom of the river, but they do not compare to the wide spread sewage system failures which affect surface waters. The rivers are able to flush themselves out over time as long as the source of contamination is not constant.

Sewage has high amounts of coliform and ecoli that are the main indicators of smaller bacteria that are a threat to humans. Open wounds can become infected and ingestion of sewer water can give a person gastrointestinal illnesses, which has similar symptoms as food poisoning1. Because the symptoms are so close to food poisoning there have been few proven sicknesses related to the rivers.

A lot of people swim in the rivers during wet weather when the water quality is at its worst. I have been swimming for 8 years and have not experienced gastrointestinal illness. That said older people, young children and those with weak immune systems are at a greater risk, and should take care.

To be able to understand when water quality is at a swim able state we must first understand the affect of aging sewer system on our rivers. Allegheny County has Combined Sewer Overflows (CSO); sewage and stormwater are mixed together in this older design typical of aging cities. It works like this: first it rains and water runs off roofs, streets and parking lots into the sewer pipes. These pipes then run along side the rivers into ALCOSAN where our sewage is treated. Because storm water is combined with sewage, ALCOSAN’s 200 million gallon tanks fill up and pump stations and holding tanks alongside the river open, releasing raw sewage into the rivers at specific locations2. When sewage is dumped into the river there is a dramatic hike in bacteria counts. The sewage is then carried downriver with the current.

Areas along the shore and directly down river of the overflow or stream mouth are the most effected. A stronger current in the middle of the rivers keeps the center less contaminated. Eventually the sewage is swept away but the time it takes to do so depends on the water current and the amount of rain that continues to fall1. By knowing the approximate amount and duration of rain, or better yet knowing when the a combined sewer overflow is open or closed a regular river user can estimate that within 3 days of closing overflows the bacteria levels are back to public water quality standards.

The most important factor to water quality in Pittsburgh’s rivers is location. Two swimming spots on the same side of the river near each other could have completely different bacteria levels. For instance the slow moving water of Washington’s Landing back channel has bridges pilings that create a still pocket of water and rarely gets flushed out. A few hundred meters down river from this the main channel moves faster and has a quicker recovery rate.

When comparing two locations at the same point in time during dry weather a faster current is usually better because the sewage is more likely to be flushed out. When the water level rises it is either from a storm, long durations of rain or melting snow. These are the same wet weather conditions that cause the combined sewer system to overflow. So when water levels are high, the current is faster but more sewage is being dumped.

It is imposable to have real time water quality data for a specific location due to the time needed for testing; only a few locations are infrequently tested and the data is usually not accessible to the public. Because water quality data is so scarce and incomplete the Allegheny County Health Department (ACHD) established the River Water Advisory in 19953.

Many of the factors discussed above are not taken into account in the advisory. You can use the 3 Rivers Wet Weather website to see specific rain data in real time which will give some sense of whether the sewers have been overflowing. Even this gives incomplete information because we do not know exactly how much rain determines an overflow (somewhere around .5 inches per hour).

Instead of relying on complex data sets or water advisories I usually just use my natural senses. If I see an overflow open and I know it has been raining for days I will assume that there are high bacteria counts in the water. If I come upon a spot after a series of dry days and the water looks clear and moving I will assume the water to be okay. But if there is a similar location on that sunny day that has still water and smells like sewage (or anything else I don’t want to swim in) I will assume the quality to be bad, even if the rest of the river is clear and moving.