Here's a little story about a city going green, right in its own parking lot. The City of Southfield's tagline is “The Center of it All.” So it was a problem for City officials to invite the public to the City’s municipal complex where the roads surrounding the complex had badly deteriorated.
Being progressive types, City adminstrators took the lead in environmental stewardship. An environmentally sensitive way to manage parking lot storm water runoff is to use porous asphalt pavement in the design. Porous pavement is a permeable pavement surface. Here's how it works. Under the pavement, a reservoir temporarily stores surface runoff before infiltrating it into the subsoil. This process reduces water contamination by providing some water quality treatment. It also reduces the amount of storm water run off into the drainage system and provides some groundwater recharge.
So how quickly can porous pavement absorb rain water?
After installing the porous pavement, municipal workers demonstrated the porous pavement’s ability to absorb water by spraying 1,000 GPM from a fire-hose. The water quickly disappeared with no trace of ponding.
Okay, so porous pavement makes for less runoff to streams. How does it work long term?
Porous pavement requires more frequent maintenance than traditional impervious paved surfaces. Over time, the voids that encourage infiltration fill with dirt and debris, reducing its effectiveness. The Michigan Asphalt Paving Association recommends that porous pavement be cleaned with a vacuum sweeper at least twice a year to maintain proper function.
For more information on porous pavement and other going green elements of the City of Southfield's project, check out the presentation below. (P.S. This project won ASCE's Quality of Life award and APWA's Project of the Year award.)
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