But all 34 blocks of the project (eventually 1,600 units) have also been turned into a natural drainage system, the largest in the U.S. The object: to protect Longfellow Creek, Seattle's most productive salmon-spawning stream. In the old neighborhood, gutters and big drainage pipes carried storm water — including spilled oil, pesticides and other pollutants — from the streets directly into the creek.
In the carefully engineered new High Point, streets tilt slightly toward one side, where shallow swales, planted with a variety of native and drought-tolerant shrubs and trees and grasses, mimic traditional sidewalk planting strips. Layered by crews with about three feet of compost, much like the floor of a forest, the swales function as a natural filter for toxins.