"The cumulative effort of everybody doing a little bit of something would help our water to stay clean. It takes all the storm water runoff. It takes it into the patio and infiltrates it and allows it to return back to the soil," according to Riordan. Sorbera told us pesticides, dog waste, litter, chemicals from your lawn treatment plus oil and gas from the driveway, all that will enter the storm water sewer system. With a permeable patio or permeable driveway, the water would end up clean when it goes into the overflow."
To show you the difference we set up an experiment. There's what happened when we dumped water on an ordinary driveway. You can see the water carried dirt down the street. Here's the same amount of water dumped on permeable pavement patio. The water soaked right in. "It filters all the roof water, the fertilizers the pesticides and by the time it gets to the base of this, is should supposedly be 100% filtered through."
There are other small steps you can take to help cut-down on runoff. Installing a raingarden is just one example. "A rain garden accepts water from your downspouts. You can channel the water directly and it's normally a depressed area with good filtering soil. That water runs through the layers of soil and comes out clean at the end."
Cities could save big money by using permeable pavement on large projects like roads and parking lots. That's because water treatment plants are cheaper to run if they're treating cleaner water.