The Gowanus Canal in Brooklyn, NY is one of the nation’s most polluted waterways. Toxic sludge lines the bottom of the canal, designated a Superfund site, and used condoms, human feces and tampons bob on the surface. Every time it rains, wastewater treatments plants inundated with storm water flush sewage and run-off into the Gowanus (check out this crazy video) in a process known as combined sewer overflow. Earlier this week, Hurricane Sandy caused the Gowanus to overflow its banks, and the foul waters crept into parking lots, spread over sidewalks and lapped against doorways.
Of course, Hurricane Sandy is only the latest extreme weather event to call attention to a problem that has been around forever. Many aging sewers are designed to carry both sewage and storm water to a treatment plant in a single pipe. This works well until it rains or snow melts, when water gushes into drainpipes and overflows the system. When this happens, wastewater treatment plants discharge raw sewage and storm water directly into nearby rivers, streams and harbors. The Environmental Protection Agency estimates that 850 billion gallons of untreated water pours into waterways each year from roughly 772 communities with combined sewer systems, mostly concentrated in the Northeast and Midwest. In the West, Oregon and Washington have the vast majority of combined sewer systems, with three and eleven respectively. The effects of such spills are varied, but include contaminated shellfish and fish kills, beach closure, gastrointestinal illness in swimmers and general unpleasantness.
Guidelines for combined sewer overflows, or CSOs, vary by state, but in Washington wastewater districts are limited to one overflow event per drainpipe per year. This is easier than limiting the volume of the flow, said Mark Henley, with the Washington Department of Ecology’s water quality program. When the state passed its first CSO law in the late 1980s, it required each of its eleven cities with combined sewers to create a plan to control their overflows. The cities could choose how to get their CSOs under control, whether by building underground storage tanks to hold excess storm water until it can be treated, separating the sewer and storm water pipes, or building mini-treatment systems at the discharge points. While each city’s CSO situation is different, storage is a popular solution, Henley said. Treatment plants are expensive and only make sense for large volumes of discharge, whereas separating sewer and storm water pipes means ripping up streets, something that is politically unpalatable.
In recent years solutions limiting the amount of storm water that makes it to the drains have become popular. Usually this involves "green" solutions that reduce the amount of nonpermeable surfaces, like pavement and concrete, that exacerbate stormwater runoff problems. Portland, Ore., for example, is installing more than 500 “green streets” with permeable pavement in the Willamette River watershed. The $81 million project also involves building various structures that absorb and filter precipitation, like rain gardens and green roofs, and will hopefully help the city avoid enlarging existing storm water pipes, which could cost an estimated $144 million.
But, as a team of Pacific Northwest reporters from Earthfix, Investigate West and Ecotrope points out, it’s harder to get the private sector on board in reducing runoff because developers aren’t legally required to integrate storm water management systems into new construction. And some local officials worry a smattering of green roofs and gardens will be harder to maintain than one centralized sewer system, albeit one that doesn’t work very well.
Last summer, when I was still living in Portland, Maine, I biked to the beach for an afternoon swim. There weren’t many people in the water that day, except those retrieving Frisbees their distracted dogs had abandoned. Later that night I found out the drainage pipe at the beach had dumped sewage the night before, due to a thunderstorm. Although I didn’t get sick, I scrubbed extra hard in the shower and vowed to pay more attention to the weather before swimming. Obviously there are more severe effects of CSOs than ruining my afternoon at the beach, but I think people shouldn’t have to think twice about going for a swim on a hot day, even if that fecal matter floating in the water is covered by a discharge permit.
I put this question to Henley, who said it’s impossible to expect cities to keep every drop of sewage out of their waterways at all times. “I think it would be considered impractical from a rate payer perspective and physically it would be very hard to do because you’d be designing these control facilities for the largest storm that you have on record.” Think of all the CSOs happening in New York City right now, he said. “They might not even be able to build tanks big enough to store those flows.”
Still, it doesn’t seem unreasonable to expect CSOs to occur only during those once in a generation storms, like Hurricane Sandy, not once a year. But until then, shit happens.
Emily Guerin is an intern at High Country News.