Environmentally Friendly Concrete

Vol. XVIII No. 2 - SUMMER 2007

Perhaps you noticed the construction last fall. The City of Chicago began tearing up two alleys, one between Berwyn and Summerdale at the east end of the block and the other a full block long north of the 1400 block of Catalpa. The project was completed before the cold winter descended upon us.

CDOT (Chicago Department of Transportation) built the two green alleys in the 48th ward as pilots. The alley between Berwyn and Summerdale used a permeable concrete, a mixture of cement and gravel that looks like rice crispy squares in profile. The rainwater drains through the porous surface into an underground bed of gravel ranging from 3-5 feet deep. From this gravel bed water is free to migrate into the sandy soils below, eventually ending up in the underground aquifer.

The alley north of Catalpa uses ecolock pavers by Unilock. These compressed concrete pavers have one inch square voids that are filled with gravel. This makes them permeable so that run off water goes down through the gravel layer and reaches the sandy soil. This is one solution to the problems of storm water runoff, backed up basement sewer drains and winter-time alley “iceponds”.

These pilot programs for green alleys will continue in the 48th ward because they are good for the environment as they regenerate our aquifers and are a more reflective surface than the black asphalt in place throughout the ward. At the end of each alley is a marker that indicates this is a Green Alley. It is shown below but if you are out for a walk be sure to stop by and see the future.

Thanks to Ernie Constantino in the office of Alderman Mary Ann Smith for the information on our new green alleys.