'The Cell' ballpark in Chicago getsnation's largest permeable parking lot

More than 527,000 interlocking permeable pavement blocks make up parking lot L at US Cellular Field on Chicago's South Side. The 265,000-sf lot is the largest permeable pavement surface in the nation and can absorb 920 gallons of water a minute.

“This surface will naturally collect and treat the stormwater that passes through it and save the city and taxpayers the cost of treating it later,” said Perri Irmer, CEO of the Illinois Sports Facilities Authority, which owns US Cellular Field, the home of the Chicago White Sox.

Irmer said the $3.5 million project would have cost at least an additional $400,000 if it had been done with traditional asphalt. Permeable paving allows water to pool on the surface and then absorbs it through a network of openings in the paving rather than running off its side into storm drains. The permeable material also outlasts traditional concrete and asphalt materials because it holds up better under the assault of weather, oils, gasoline, and salt. ISFA and Unilock, the locally based supplier of the pavement blocks, estimated that the lot would not need resurfacing for at least 40 years. Rose Paving of Bridgeview, Ill., began the project last summer and completed it in December.

Permeable pavement is recognized as green by the EPA and contributes to the stormwater credit in the USGBC's LEED standard. The Unilock pavers are made of recycled brick and also reduce the urban heat island effect because of their light color.

ISFA officials said that the system was selected in part because of a new Chicago stormwater ordinance that went into effect January 1 that requires new developments or large redevelopments to capture the first half-inch of runoff from all impervious surfaces.

“It's for conservation,” said James Balcer, alderman of Chicago's 11th ward, where US Cellular Field is located. “Oil is number one right now but somewhere along the line, water will be.”

—Jeff Yoders, Senior Associate Editor