Peeling back the Pavement - POLIS Water Sustainability Project

introduction
A Tale of two cities
Picture two cities. Now, picture that it is raining. In one city, you see rain falling on
your standard urban landscape of concrete, asphalt, and roofs. The city is primarily
constructed of impermeable surfaces and water is flowing down the street and
into storm sewers. Once there, it is quickly piped away to a receiving body of water,
whether it is a local creek, a lake, or the ocean. In the second city, the picture is
different. There is less concrete and asphalt and very little water is washing down the
storm drains.
Why?
Because green infrastructure is visible everywhere: downspouts connected to rainwater
cisterns, rain gardens, green roofs, deep-soiled lawns, sidewalks with planter
boxes, permeable pavement, and bioswales. In this city, rain is a valuable resource. It
is not a threat to be dealt with, but a resource to be harnessed to recharge aquifers,
support functioning streams and watersheds, and provide important services in our
homes, such as flushing toilets, cleaning laundry, and watering our green spaces. Rain
is managed to mimic the natural water cycle and its capture and reuse are part of
everyday urban life.
In the first city—the Stormwater City—rain and snowmelt pick up pollutants from
the urban landscape as they sweep over roofs, streets, and parking lots. In the
process what was simply rain becomes stormwater. This contaminated water is
conveyed through storm sewers at high speeds and volumes into the surrounding
lakes and rivers. Stormwater runoff is one of the biggest water pollution challenges
facing the city, and it is the main source of toxic chemicals entering urban streams. 1
Runoff channelizes and destroys urban fish-bearing creeks, taints shellfish, prompts
beach closures, and prevents groundwater recharge. In stormwater runoff, a valuable
resource—fresh water—literally runs down the drain. 2 The pipe-and-convey
approach to managing wet weather in this city also comes at a financial cost to taxpayers,
and prompts expensive maintenance and expansion of hard infrastructure.
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