“You have marine impacts, ecosystem impacts, and public health impacts,” said David Beckman, co-director of the National Resource Defense Council’s national water program. “It’s really a multiplicity of problems. Pollutants in urban settings are many and of a wide variety, and all of them - if you don’t treat and successfully reduce the pollution - are getting into the receiving water, be it a river or lake or the ocean.”
In a natural system, rainwater doesn’t travel very far. It soaks into the soil and is taken up by plants. The quick infiltration prevents the water from transporting contaminants and keeps waterways from eroding.
But the concrete and asphalt of the urban jungle is anything but natural. Instead of soaking into the ground, rain runs across impervious surfaces, picking up contaminants along the way. By the time it reaches a stream or lake, the runoff can be full of metals, oil, grease, bacteria and other contaminants.
Stormwater also picks up speed. When it hits a stream it scours sediment, dislodges benthic invertebrates and erodes banks, effectively demolishing the natural habitat.
“When you put an impervious surface down it becomes a really good delivery system.” said Roger Bannerman, an environmental specialist with the Wisconsin Department of Natural Resources. “We see that in the bottom sediments, we see it in the water quality itself, we see it in the kinds of chemicals we find in the fish.”
Michigan’s Little Black Creek has long been tainted by industrial runoff. An old refinery, a metal-plating company, a wastewater treatment plant and a landfill all contributed to its pollution problems. All those facilities, however, have been shut down.
Today, the biggest continuing threat to the creek comes from the streets around Muskegon.
“Historically, when we developed areas we used gutters and storm drains as our way of channeling that stormwater,” said Al Steinman, director of Grand Valley State University’s Annis Water Resources Institute in Muskegon, who has been studying Little Black Creek’s stormwater problem since 2007. “We looked at the water as something that needed to be gotten rid of as quickly as possible, as efficiently as possible, and the engineers went about doing that.”
The state and local governments have been taking steps to reduce the runoff. The Muskegon Conservation District and Mona Lake Watershed Council planted a buffer strip of native vegetation to absorb stormwater runoff from a park. And an education campaign discouraged residents from dumping waste in storm drains that lead straight to the creek.
No one knows if their efforts are paying off with cleaner water, said Alyssa Merten, a project manager for the Muskegon Conservation District. “It is not an easily documented thing,” she said.
Experts say with careful design, 100 percent of stormwater can be infiltrated into the ground or recycled.
Developers can use infiltration basins, green roofs, rain barrels and rain gardens to capture runoff. They can also reduce impervious surfaces by constructing narrow roads and using porous pavement.
These low-impact development techniques can do a perfect job controlling stormwater, said Donald Carpenter, an associate professor of civil engineering and director of the Great Lakes Stormwater Management Institute at Lawrence Technical University in Southfield, Mich.