Los Angeles has a ton of alleys. More than 2,000 acres worth, in fact. Two things we don’t have a lot of are water and park space. Starting with a pilot project in South LA, the Board of Public Works is out to use that alley abundance to make a dent in both of the other two problems at once. The board is building something called “green alleys,” and, as the New York Times reports, they’re part of a city-wide project to recover an additional 41.2 billion gallons of otherwise-wasted water every year by 2035 (though we definitely have to hope this current drought will be over by 2035, right?).
Right now, when rain falls, mostly-clean water hits the pavement of all those alleys because it doesn’t have anything absorbent to land on. So instead of getting soaked down into the water table, it just runs off down the streets, collecting all types of pollutants and chemicals along the way, to a sewer system that eventually trickles out into the Pacific Ocean.
With a green alley, like the ones already in use in Chicago and elsewhere, the pavement is replaced with a porous, water-permeable concrete and the curbs are dotted with storm drains. These work together to allow water to drop through into underground containment units. A single green alley, like the one set to be finished soon between East 51st and 52nd streets along South Avalon Boulevard, might be able to reclaim 700,000 gallons or more in a year—and that’s based on current levels of precipitation, not what it might be able to collect if we ever see another rainy season.
In addition to all that water collection, the green alleys are a boon to the communities where they are installed as well. The pavement used has properties that reflect sunlight rather than absorbing it like old-fashioned asphalt, which means that it helps the surface stay cooler in the heat of the summer. Moreover, the alley networks will be operated as safe park spaces for the public, which is important particularly in communities like South LA, where the acreage of open space per person is a whopping 94.7 percent below the national average.
Anything that saves water while providing places for people to have fun seems like a great use for an otherwise bland alleyway.