D.C. Director of the Environment Christophe Tulou is standing on a special type of concrete called pervious concrete. It lets water go through it instead of run off it.
"We're standing right at that junction between a pervious alley and a traditional alley," says Tulou. "We had a big rain storm last night... on the traditional alley you've got water standing, on the pervious alley it's all gone."
The point of this is to prevent water from gushing into the city's storm water and sewer systems, causing backups, and scouring pollution into the Chesapeake Bay. In this case, it helps with flooding says D.C. resident Laura Taylor.
"It's much better, you can park, walk through it and everything.... it's nice out here," she says.
This type of alley costs double what a traditional alley would, and was paid for by federal stimulus money. The city hopes to get costs down to the same as a regular alley so pervious paving can become the norm.