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Thursday, Aug. 11, 2011 01:51 pm

Going against the flow

Need Springfield gag on stormwater?

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The $129 million Spring Creek Wastewater Treatment Plant is under construction north of Veterans Parkway at Eighth Street Road.
PHOTO BY DAVID HINE

My advice is, don’t ever invite the executive director of the Springfield Metro Sanitary District and a carp to the same party. Springfield, you see, is one of dozens of Illinois cities and towns that have a combined sewage system in which the same pipes that carry untreated sewage to the treatment plant also are connected to the storm sewers. Usually that’s no big deal; the brew of human waste and stormwater that pours out of the end of a combined sewage pipe after a rain gets treated in the plant as if it were ordinary sewage. Thus are the city’s bowels occasionally flushed clean.

However, even a moderate gush of sewage-laden water can overwhelm the treatment plant’s capacity. (Think of Sangamon Avenue during the fair.) To prevent flooding the plant, the mess is diverted around the plant and dumped directly into streams. As the SMSD put it on its website, “This of course made for some rather unpleasant conditions.” (For a more detailed account of the overflow problem, see our Rachel Wells’s “The flushing factor,” July 21, 2011.)

The State of Illinois naturally disapproves of the SMSD, in effect, pooing in its streams. The EPA sent 27 warnings to the district in 2010 about overflows polluting local waters, and so far this year another 11. The expansion of the Springfield Creek treatment plant, nearing completion, will help only a little. The district has until year’s end to file with the state its long-term plan to stop the dumping.

The problem is less how we build sewer systems than the way we build cities. Springfield’s natural drainage system has long since been ditched, straightened, piped or simply plowed under. More and more of its land is covered by hard surfaces such as shingled roofs and asphalt or concrete roads and parking lots. (New houses in the 1950s featured driveways surfaced with crushed rock, for instance, while today driveways are usually paved.) Water that used to collect and stand in low spots is now rushed into pipes. Thus concentrated, ordinary rains are turned into floods.

Bad enough. But what if extraordinary rains become as common an occurrence as indigestion among five-year-olds at the fair? In a recent column I remarked that the recent extreme summer “weather events” such as half the Gulf of Mexico being dumped on the city in a matter of hours, are consistent with what climatologists’ models say are the likely effects of global warming. (“It’s not the heat, it’s the corn,” July 21, 2011.) Among those effects is a doubling of intense storms such as the one that pelted the city in May of 2010 at a rate of three inches an hour. Some stormwater professionals now wonder whether these crucial bits of urban infrastructure might prove to be dramatically undersized.

Further expanding the city’s conventional pipe-and-pump system to accommodate the resulting overflows is probably neither affordable nor wise. One solution would be to adopt “green” or “soft” measures to slow the movement of heavy rains toward the pipes. These include protecting (or restoring) surviving floodplains and wetlands, installing rain gardens and rain barrels, porous pavements, green roofs, infiltration planters, trees and tree boxes. Grassy swales that carry stormwater from parking lots can not only absorb but filter such runoff. Undeveloped land most suitable as catchment areas could be protected; such opportunities are probably plentiful in ill-drained New Springfield, which is not yet fully built out.

And of course good design can be encouraged by thoughtful regulatory incentives. Code requirements that allow narrower streets and sidewalks and driveways with planted center strips can, it has been estimated, reduce the environmental impact of paved development by anywhere from 30 to 50 percent. Requiring a minimum percentage of a parking lot’s surface area to be opened as planting islands would have similar effects. In some parts of the country local governments now require people remodeling their houses to offset runoff if the work expands hardened surfaces on the lot. (The owners choose how.) Philadelphia’s updated stormwater regulations require new development to retain the first inch of every rainfall on site; a single square mile of such retrofits would save $170 million in capital alone over the cost of storing the same water in a tank or tunnel.

More than money, such expedients require more imagination and intelligence – which, admittedly, can be even harder to find in the public sphere than money – and can be done in bits and pieces. As an approach to wet weather management, sayeth the U.S. EPA, such approaches are “cost-effective, sustainable, and environmentally friendly.” And you get recreation and green space and wildlife habitat to boot. Springfield Green indeed.

I am obliged to add, however, that turning an entire city into a rain barrel will take some persuading. Developers won’t like the cost in land, of course. Nor will most property owners, who’ve come to expect that stormwater can just disappear down a hole in the ground, the way other unwelcome things can be flushed down a toilet – unless the alternative is another quadrupling of sewer charges.

Contact James Krohe Jr. at KroJnr@gmail.com.

CORREX: Former State Journal-Register columnist Toby McDaniel is alive, contrary to my statement of last week. The same cannot be said of my memory. Sorry.

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