Three Permeable Parking Lots

400 Derby St., Oakland Map
Park Ave. at Holden, Emeryville Map
Bay St. at Papazian, Fremont Map

Above, parking lots at Oakland Boathouse Lofts and Park Street art gallery in Emeryville look ordinary until you notice the pebbly surface of the concrete. Omitting fine particles from the mix leaves voids. Water can percolate through to a base of sand and crushed rock, which can act as a reservoir, delaying peak flows, filter pollutants, and let some runoff soak into soil. Underdrains usually are needed to take heavy flows to storm drains.

Permeable asphalt has been used since the 1930s to improve traction on highways, but use in permeable parking is relatively new. As with permeable concrete, fine particles are omitted. The Bay Street Demonstration Parking Lot, in Fremont, is being monitored for performance. Click here for background and technical information.