An informative and beautifully designed interpretative sign educates the public on the effects of stormwater runoff, the impacts on water quality and aquatic life, the beneficial uses of "rain gardens" or natural stormwater treatment areas, and the role individuals can play in cleaning-up our watersheds and preventing pollutants from entering our waterways. 

The Carlos Street rain garden in Moss Beach collects and filters stormwater from the street, Post Office parking lot, and adjacent private properties and businesses. By placing small rain gardens in strategic locations, pollution going to local water bodies is reduced, resulting in improved water quality in the Fitzgerald Marine Reserve and designated Area of Special Biological Significance (ASBS).

When it Rains

Stormwater runoff occurs when rain falls on hard surfaces such as roads, driveways, parking lots, and rooftops.  These surfaces are considered impervious because they prevent water from soaking into the ground and significantly increase the volume of runoff flowing into storm drains. Stormwater runoff picks up and carries pollutants including vehicle-related pollutants such as oil and metals from tires and brake pads, and other common pollutants like pesticides, trash, and animal/pet waste that are harmful to streams, estuaries, and the ocean.

Why Do We Care?

Pollutants in stormwater negatively impact water quality and aquatic life.  The James V. Fitzgerald Marine Reserve, a designated Area of Special Biological Significance (ASBS), is sensitive to these water quality impacts due to its function as habitat to a diversity of native plant and animal species.  The State prohibits anyone from discharging pollutants into these special areas.  The County of San Mateo is therefore implementing education programs and installing rain gardens like this one in an effort to reduce pollutant discharges to the ocean and protect the Fitzgerald Marine Reserve and ASBS.

Natural Stormwater Treatment

Bioretention areas or “rain gardens”, such as this one along Carlos Street, are designed to naturally remove pollutants from stormwater as well as slow down and detain stormwater.  The plants and specially designed soil mix act as a filter as stormwater collets and infiltrates through the layers of the rain garden. The filtered water then percolates into the ground or leaves the rain garden through a perforated underground drain pipe that connects to the storm drain system and eventually discharges into the Fitzgerald Marine Reserve and ASBS.

The Garden

Only native plants were used in this rain garden. They require very little water and no additional fertilizer, are drought- and pest-resistant, and need limited maintenance.  Rain gardens improve habitat, attract birds, butterflies, and bees while also increasing aesthetics in the neighborhood. Native plants in this rain garden include yarrow, blue-eyed grass, beach strawberry, yerba buena, rush, and field sedge.

How Can You Help?

Each of us can play a role in cleaning-up our watersheds and preventing pollutants from entering our waterways.  Here are some easy ways to help:

  • Wash cars at a commercial carwash
  • Cleanup and properly dispose of pet waste
  • Reduce residential pesticide and fertilizer use
  • Plant native species
  • Install a rain barrel or rain garden

For more information visit


Associated Staff: 
Programs and Focus Areas: 
Clean Water Program
Environmental Informatics Program
Design and Communications
Location Information
General Project Location(s): 
Moss Beach