America’s earliest urban sewers were pretty simple: We piped human waste directly from neighborhoods into rivers.
We changed that in the second half of the 20th century with treatment plants that basically processed human poop into sludge, leaving cleansed water to be piped into rivers.
Despite that, raw sewage occasionally still gets into public waters, due to (a) the way that many older sewer systems were set up and (b) hard rains.
These older systems take in both sewage (which generally comes from toilets) and stormwater (which generally comes from rain on city streets and other impervious surfaces). These arrangements are called combined sewer systems.
With these disposal methods, when rains fall particularly hard -- as is increasingly occurring -- stormwaters can overwhelm sewage plants to the point where both stormwater and raw sewage wind up going straight into public waters. There’s a term for that. It’s called “combined sewer overflows” -- CSOs for short.
The problem is big enough to justify holding conferences about it. The other day I attended a conference put on by the Massachusetts-based Merrimack River Watershed Council that focused solely on the problem.
CSOs don’t happen everywhere. Some cities have set up ways to send stormwaters directly into rivers, leaving sewer plants to handle waste alone. The photo accompanying this posting, which was taken on the campus of Keene State College in Keene, New Hampshire, indicates a municipal system that has two parts: an arrangement of pipes that sends stormwater directly into a local river and a separate arrangement of pipes that sends waste to the local sewer plant.
That two-part system means that hard rain storms won’t overwhelm Keene’s sewage treatment plant. Enlightened. An added bonus in Keene is the prevalence of rain gardens in public and private places that soak up rainfall , thereby reducing the volume of stormwater that winds up flowing across pavements, into storm grates (picking up contaminants along the way) and then going into the river that flows through Keene.
There are other ways to avoid -- or reduce the frequency of – CSOs, some of them pretty dramatic. Among other cities, Portland, Maine, which in most cases sends both sewage and stormwater to its treatment plant, has taken to building huge stormwater retention tunnels and other underground storage facilities to store stormwater until it can be gradually sent to the city’s wastewater treatment plant and thereby avoid overwhelming it.
Here’s a collection of photos of a such a tunnel in Portland.
You can imagine that these tunnels don’t come cheap. For example, Washington DC is planning to spend $2.7 billion on three stormwater storage tunnels to avoid combined sewer overflows.
The enormous cost of such projects has put some communities into a panic. One result: Congresswoman Lori Trahan, whose district includes the Merrimack River area, has asked that the EPA’s budget for the new year include $500 million for federal grants to help out; she’s so focused on the matter that she’s come to be known in the halls of Congress as “the sewer lady.”
Another result: cities have lobbied the current administration to delay spending on CSO-avoidance schemes, leaving untreated sewage to flow into public waters for years to come as hard rains increasingly hit city streets. According to The New York Times, they’re finding a receptive ear in the Trump administration.
A lesson in all this is that not all problems around fresh water go away entirely; some problems simply change. Where once we intentionally piped raw sewage into rivers, now we’re unintentionally letting that happen when stormwaters run strong. That calls for new solutions, which in time might lead to new problems — and then yet newer solutions — that we can’t imagine today.