GreenTown Los Altos

Let It Rain: Bioswales at Rosita Park Help Slow It, Spread It, Sink It


Apr 2012


by Gary Hedden, GreenTown Volunteer


The recent storms have been handled with ease along Rosita Ave in Los Altos.  The newly rebuilt Rosita Park has a lot of impervious surface so storm water runoff was a big concern.  With three tennis courts and a big parking lot, water could have surged down the street into the storm drain, carrying with it lawn chemicals, oil from cars, and other pollutants that harm our creeks and Bay and the wildlife in them.

Curb cuts along Rosita Ave. help direct stormwater to a bioswale. Photo credit: Gary Hedden

But it didn’t. Instead curb cuts cleverly directed the water to infiltration areas filled with a special soil, slowing the flow and allowing the water to sink into the subsurface.  These planted areas that slow and help sink water are sometimes referred to as bioswales.  Pipes buried 18 inches deep eventually carry excess water to the storm drain.


According to Larry Lind, Senior Engineer with the City of Los Altos, this approach will “slow the flow into the storm drain and allow micro-organism treatment of the water.”  So we get both flood control and cleaner water in our creeks.  Denise Welsh, who lives at the corner of Rosita and Campbell, says she and her husband are “extremely pleased” with how well the system works.


Three cheers to the City of Los Altos for a job well done.

Rocks and special soil in the swale help to slow and sink the stormwater. Photo credit: Gary Hedden

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