I am happy to say that on a recent visit to San Francisco I noticed bio retention islands in parking lots in the Bay Area.   I have noticed them recently in the Philadelphia area too.   They are nicely landscaped, and they are the kind of commonplace thing you see that you don’t “really” notice.  Often they blend in with the environment well.    This is a good thing.  But recently I began noticing them more and wondering what are they and why are they there?  I recently learned that they are not just there for ornamentation.  They are there to manage storm water that flows over impervious surfaces such as parking lots. Bio retention areas are landscaping features that are built to provide on-site treatment of storm water runoff.  Surface runoff is directed into shallow, concave depressions. These depressions are designed to incorporate many storm water management practices. During storms, runoff gathers above the mulch and soil in the system.  The remaining runoff filters through the mulch and soil mix. The runoff is collected and stored in the soil, or it is directed to perforated “under drains” and then returned to the storm drain system after the rain event has occurred.   All of this results in reducing the amount of untreated storm water run off that is directed into storm drains and ultimately into rivers and streams. BIO RETENION ISLANDS IN BURLINGAME, CALIFORNIA. LUCKILY, WE SEE A LOT OF THESE APPEARING IN THE PHILADELPHIA AREA