Green infrastructure: Sewage, sewage, go away

You know the song: “Rain, rain, go away/Come again some other day.”

Heavy rain in places with older sewer systems (Michigan and elsewhere), often results in combined sewage overflows. But it doesn’t have to be that way. And the solution doesn’t have to cost billions of dollars.

First off, combined sewage systems are problematic because they take in sanitary sewage (toilet) in the same pipes as stormwater runoff (manhole). When it rains, water that runs off of impervious surfaces like rooftops and parking lots can overwhelm combined systems.

Combined systems use retention basins to hold excess flow during storm events. The idea is that wastewater treatment plant operators may be able to pump the basin contents back to the plant, so the dirty water can be fully treated.

But sometimes they can’t keep up, which undoubtedly happened recently in areas of Michigan, which saw 2+ inches of rain during the weekend of April 24-26, 2009.

Which brings us to a solution: Green infrastructure. When areas are developed, they can lose their natural capacity to drain water during storms. But building with drainage in mind can help alleviate the problem.

The idea is to treat the stormwater runoff BEFORE it enters the sewer system. Newer sewage systems, by the way, are separated, with sanitary and stormwater flowing in separate pipes. While that can eliminate overflows, it means the stormwater is sometimes not treated at all before it’s discharged to a waterway.

Examples of green infrastructure include green roofs, rain gardens and permeable pavement, according to the U.S. Environmental Protection Agency. These practices can start on a small scale, in neighborhoods, and be expanded to watersheds.

Not only does green infrastructure reduce water pollution, it can help sequester carbon dioxide, improve air quality and provide wildlife habitat.

A 2007 evaluation of 17 case studies throughout the United States found that green infrastructure, also called low impact development, can cost more upfront. But savings of up to 80 percent can be realized due to reduced costs for site grading and prep, stormwater infrastructure, site paving and landscaping.

And what price can you put on public health?

Courtesy City of Bloomington, Ind.