Are Combined Sewer Overflows Causing Pollution in Your Local Waters?

March 21, 2018

TipSheet: Are Combined Sewer Overflows Causing Pollution in Your Local Waters?

Raw sewage may be going into your local river, stream or estuary more often than you think — even after it is supposedly “cleaned up.” The culprit? Combined sewers.

Case in point: The Potomac River, which flows through the nation’s capital. Much hoopla was made of the historic cleaning up of the severely polluted waterway beginning in the 1970s with the Clean Water Act.

A major share of all sanitary sewage in the Washington, D.C., metro region flows through the Blue Plains plant — the largest advanced sewage treatment plant in the world. And this in turn helps keep the Chesapeake Bay cleaner.

Yet raw sewage — including human waste — still flows into the Potomac at times today. It happens during high stormwater flows caused by unusually heavy rains or snowmelts.

Such combined sanitary-storm sewage is usually treated by metropolitan treatment plants. But when the flow exceeds the plant’s capacity, some is dumped in the receiving body, like the Potomac, where people swim, water-ski, boat and fish. … yuck.

Or worse yet, as was the case in Chicago for many years, the huge rush of storm-sanitary sewage would exceed the capacity of the pipes that were supposed to carry it away — and it would back up into people’s basements. … double yuck.

Some of the sewers in the D.C. region are combined, and despite years of steady progress, separation is far from complete. It is a big, complex, old metro region, and some of its streams, such as the Anacostia River, still receive these combined sewer overflows, or CSOs. The Anacostia flows into the Potomac. Once again … yuck.

Approaches to lessen the problem

There are many ways to mitigate CSOs.

Separation (laying a separate, new set of pipes) is only one of them — and quite expensive and disruptive. Separation may not even solve all the pollution problems, because stormwater runoff is loaded with oil, sediments, dog poop, pesticides and worse.

Many areas require new developments to include things like stormwater retention ponds, which store and delay storm flows enough that treatment plants can handle them. These also settle out sediments.

Signage for a combined sewer overflow point in Milwaukee, Wisc. Photo: Michael Pereckas, Flickr Creative Commons

These approaches help in areas that believe in zoning. Others, not so much. Are you listening, Houston?

Part of the solution D.C. has chosen, for instance, is a huge tunnel system (Chicago built a tunnel as well).

The combined sewer flow is directed through a huge underground passageway so big that it can store the excess for most big storms until Blue Plains can treat it. It is being built out in phases (it’s a network of tunnels), one of which will capture CSOs from the Anacostia. This is called “inline storage,” in sewage engineer jargon.

Getting started with your reporting

If you are writing about the environment, you will definitely want to know more about your local and regional sewer systems (whether or not they are combined), as well as what happens during heavy storms.

There are lists of cities facing these problems. That is handy, but the lists are always a little out of date.

One commonplace generalization is that most combined sewer systems are in the Northeast and Great Lakes regions — and that is somewhat true. But don’t make assumptions. Surfers sometimes find California beaches closed too because of sewage.

The best solution, in any case, is to check in with your local sewerage agency, and then to follow up thoroughly on whatever they tell you. Then make contact with the local planning and zoning agencies, developers and chamber of commerce.

And don’t forget to reach out to your local environmental groups, watershed protection fans and groups like Riverkeepers.

Tracking the problem through permits

One way we know where the CSOs are (to the extent that we really do know) is that they need discharge permits under the Clean Water Act.

The U.S. Environmental Protection Agency compiled a pretty thorough list in 2004 as part of a report to Congress, and some progress has been made since then.

Still, there are outlaw outfalls. EPA said a decade ago that there were 860 communities in the United States with combined sewers. As an alternative, you can struggle with the online searchable EPA database of water discharge permits.

Over the years, EPA’s policy has not been to jail mayors of cities with CSO problems. Even if they wanted to build new sewer systems, they would have neither the money nor the time. Instead, EPA uses the permit process to nudge the cities toward incremental improvements. You can see some possible measures (and more measures here).

It’s worth remembering that CSOs are really just a special case of a larger category of pollution problems related to high flows or “wet weather flows.”

When a real flood hits your area, it may knock out a whole sewage treatment plant, if it is in the flood plain. And the flood waters may be contaminated with known and unknown horrors.

EPA and others have in recent years been emphasizing “green infrastructure” that prevents or delays stormwater from getting into the system (and may help recharge aquifers).

Remember, too, that the important thing is the quality of the receiving water body (well, as long as you don’t have sewage in your basement).

* From the weekly news magazine SEJournal Online, Vol. 3, No. 12. Content from each new issue of SEJournal Online is available to the public via the SEJournal Online main page. Subscribe to the e-newsletter here. And see past issues of the SEJournal archived here.

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