Your new word for today is: Bioswale.
A bioswale is a landscaped area designed to remove toxins and silt from rainwater as it sinks down into the water table. The drainage course looks like a little valley with sloped sides and is filled with vegetation and compost.
Read more about the bioswales at Pomona College in this article. Here are some photos from the bioswale next to the parking structure/lacrosse field along 1st St.