But a rainstorm can quickly overwhelm the sewers’ capacity. An inch of rain falling on the entire three square miles of the Portland peninsula can generate about 50 million gallons of rainwater. If that water falls on city parks or forests, it will slowly sink into the soil. But much of that rain falls on rooftops, streets, and parking lots, from where it takes a short trip to the nearest storm drain and into the city’s combined sewers. Along its way, it picks up the same sort of street grime and garbage that’s currently frozen inside the glaciers.
Millions of gallons of raw residential and commercial sewage mixing with tens of millions of gallons of stormwater runoff can quickly overtax the capacity of the sewer pipes. When this happens, the sewers are designed to overflow the toxic mixture of excrement and runoff into the nearest body of water — which could be Capisic Brook, Back Cove, or under the wharves on the waterfront — before the sewage begins to back up into bathtubs and streets.
These “combined-sewer overflow” sites act as relief valves for Portland’s sewers. They’re marked by small green signs (and sometimes, by foul smells as well) at various points along Commercial Street, Baxter Boulevard, and the Fore River.Even when sewage manages to make it to the East End, the treatment plant is sometimes forced to dump semi-treated wastewater into the Bay if the pipes are delivering more than the plant can handle. These overflows, which usually occur during or after sustained periods of wet weather, can sometimes cause the city to shut down the East End Beach due to dangerous levels of fecal coliform bacteria (see “What If ...” by Alex Irvine, January 9, 2004).
Sewer overflows happen fairly often in Portland. According to Maine’s Department of Environmental Protection, Portland’s sewers discharged 1.8 billion gallons of untreated sewage into Casco Bay and its tributaries in 2006 alone. If it were frozen, that amount of liquid could produce about 300 sewage icebergs the size of the existing Bayside glacier.
The city recently approved a new round of sewer upgrades that will reduce overflows by separating storm sewers from the so-called “sanitary sewers” that handle sewage from the city’s buildings (see sidebar, “Separating Pollution”). But while these projects will help ensure that raw sewage goes only to the treatment plant, without mixing with stormwater or overflowing into local water bodies, the polluted runoff that goes down the city’s storm drains will still flow more or less straight into Casco Bay and its tributaries during heavy rains.
In the meantime, the winter gives us a relative respite from overflowing sewers and runoff pollution. As long as the snow stays above ground, it can’t overwhelm sewer pipes or the treatment plant. As spring arrives, though, that thawing ice, and an entire winter’s worth of pollution trapped inside of it, is beginning to drain towards Casco Bay.
Twilight for the Bayside Glacier
The city’s glaciers typically melt away by June. As the top layers melt in the coming weeks, more and more of the winter’s flotsam will surface, and the glaciers will look less like piles of snow and more like piles of filthy trash..
By the end of May last year, the melting Bayside glacier had left behind a swampy terminal moraine that was so strewn with garbage that some Portlanders apparently mistook it for a landfill, and deposited their old mattresses and computer monitors there during heavy-trash collection week.
When the ice is completely gone and only garbage remains, the DPW conducts a cleanup of the snow-dump sites by carting the trash to the ecomaine incinerator (just across the street from the outer Congress glacier) and delivering truckloads of sand and gravel to the Riverside recycling center.
Before that happens, though, much of the glaciers’ effluvia will already have made its way downstream. When the first big rainstorm of the springtime hits, the glaciers’ grimy top layers will melt and wash away, taking with them a heavy dose of concentrated pollution.
At the snow-dump on outer Congress, “there are devices called ‘downstream defenders’ that the runoff goes through,” says Payne. “It traps the sediment, and some of the oil and grease and other [pollutants] that come out of the meltwater.”
The Bayside glacier has no such protection, though. Some of its filth will merely sink into the ground before it reaches a gutter. But much of its meltwater will flow into street drains on Somerset and Chestnut streets. From there, if it’s raining, it will probably mix with household and commercial sewage and overflow into Back Cove in an unusually toxic discharge.
Like many other glaciers of the temperate latitudes, though, the Bayside glacier may soon disappear for good.
Last month, the City Council’s Community Development Committee agreed to negotiate individually with three developers who want to replace the glacier’s empty lot with office buildings, housing, and a parking garage for 700 cars.
If and when that happens, “We’ll be forced to haul all of the snow out to outer Congress,” Early says.
