Seattle SEAstreet
Another example of a larger scale biorentetion project is the SEAstreet (named for Street Edge Alternatives) project in Seattle, Washington. This landmark project encompassed two city blocks in a residential neighborhood in a retrofit to improve the quality of stormwater runoff. This 660 foot long "Super block" was the prototype model upon which Seattle has modeled other such projects.
The impervious surface of the street was reduced by 11%; plantings included 100 evergreen trees and 1100 shrubs. Monitoring has shown a 98% reduction in stormwater volume. The 2.3 acre area yielded only 132 cubic feet of water post installation, while the previous year (March -July) yielded nearly 5,000 cubic feet of runoff!*
The roadway was reduced to 14 feet wide and 18 feet at intersections. While this project cost approximately $850,000 dollars, subsequent projects have been completed at a lower cost; this demonstrates that it is possible to contain stormwater in a retrofit which could conceivably add to the esthetic appeal of the neighborhood.
For more information, see: Seattle Public Utilities
See: Seattle Post Nov.20, 2002 article for overview and additional photographs