An inch of rain falling on a 100-car parking lot causes runoff of about 20,000 gallons. For a mall with 5,000 parking spaces, that number swells to a million.
There are thousands of acres of parking lots, driveways, roofs, streets and other impervious surfaces in lower Fairfield County, and rainwater flowing off these expanses of asphalt and concrete causes water quality problems for streams, rivers, ponds, lakes and even Long Island Sound.
But there are solutions, and a new website, www.reducerunoff.org, aims to educate residents, businesses and municipal officials on what can be done.
"The website teaches people how they can reduce the amount of rainwater that flows off their property, such as creating rainwater collection sites, installing rain barrels or by using paving materials that can absorb water," said Kierran Broatch, creator of the site for two environmental groups, Save the Sound and the Connecticut Fund for the Environment.
He said homeowners can opt for permeable driveways and patios that help recharge groundwater levels, improve soil moisture and maintain vernal pools in the spring, an important habitat of amphibians. Rain barrels, he said, can save water for summertime dry spells, and rain gardens collect runoff and allow it to percolate back to the soil.
"One of the areas that we're focusing on are the parking lots of the big box stores in the Quinnipiac River watershed, which can be helped by creating `bioretention' areas," he said. "Basically, these are large rain gardens."
For example, the practice of allowing -- even requiring -- stores to build parking for the expected maximum number of shoppers has created a landscape dominated by parking lots, rather than the buildings they serve. And often city planning regulations call for a minimum parking lot size, but no maximum, effectively allowing developers to pave over as much real estate as they wish.
These "seas of asphalt," NEMO experts say, "raincoats the earth, allowing a rich bouillabaisse of polluted runoff that is ultimately fed into unsuspecting rivers and streams."
There is some progress being made. In 2007 the city of Bridgeport installed a series of rain gardens along upper Main Street that collect runoff from the street and sidewalks, allowing it to soak harmlessly into the soil.
"Those gardens still look good," Broatch said, "and we're glad to see that Bridgeport is making headway on this issue."
firstname.lastname@example.org; 203-330-6403; http://twitter.com/johnburgeson