This is kind of cool. The city of Chicago is embarking on a process to re-pave its 1900 miles of alleys with a new type of concrete that is better for the environment, according to CNN. This concrete is porous, allowing rainwater to seep through to the soil underneath and, eventually, to an aquifer that feeds into Lake Michigan. Better still, the concrete is created in such a way that it filters the water, cleaning out pollutants as it makes its way back into the environment. Embedded in the concrete are microbes that feed on fertilizers, oil, and other substances.
In addition, the concrete has a higher albedo than normal, reflecting some of the sun's light back instead of absorbing it. That will allow the 3500 acres of paved alleys in Chicago absorb less heat, allowing the city to be somewhat cooler in the summer. And if that's not enough, the pavement of the alleys is made from recycled materials and new lighting in the alleys is designed to direct light downwards to reduce light pollution.
So far the city has completed 40 of the alley makeovers, with 48 more scheduled to be completed this year.