Apply for a Rain Garden Rebate

Applicants can receive a rain garden rebate at a rate of $2.00/square foot up to $600. The City of Palo Alto partners with Valley Water to offer cost sharing for Stormwater Rebates. Each property has City Stormwater Rebate lifetime maximum and Valley Water Rebate lifetime maximum. The City Stormwater Rebate lifetime maximum is the total amount of funding that one property can receive across that property’s lifetime specific to Stormwater Rebates offered by the City. The rebates included in the Stormwater Rebate lifetime maximum are:

• Rain Barrel Rebate
• Cistern Rebate
• Pervious Pavement Rebate
• Rain Garden Rebate

The Valley Water Rebate lifetime maximum is the total amount of funding that one property can receive across the property lifetime and includes all rebate types offered by the City of Palo Alto and Valley Water (Landscape Conversion, Irrigation Equipment, and Stormwater Rebates). For more information on rebate lifetime maximums please visit Valley Water's Program Overview webpage. 

Rain gardens are a relatively low-cost, effective, and beautiful way to reduce the amount of stormwater that runs off your property. Rain gardens capture and treat rainwater that runs off impervious surfaces like driveways and roofs. Runoff is directed towards a depression in the ground, which is planted with drought-resistant (and typically native) plants.

Rain gardens keep roof runoff from reaching the storm drain. When water flows from our roofs during storms, it runs off into storm drain inlets (or curb openings). During large storms, the storm drain system carries this polluted water to our local creeks and the San Francisco Bay.

Rain Gardens can also provide attractive habitat for birds, butterflies, and other animals, especially when planted with native plants (Source: BASMAA 2012(PDF, 798KB) ).

Per Valley Water and the City of Palo Alto, the following requirements must be met to receive a rain garden rebate:

1. A minimum of 100 square feet of contributing roof area must divert to the rain garden.
2. Rain garden size must be at least 24 square feet and in proportion to the calculated roof area. See “How should I size my rain garden?” below for details.
3. The deepest part of the rain garden must be located at least:

   • 10 feet from the building foundation

   • 3 feet from public sidewalks

   • 5 feet from private property lines

4. The garden should not be located over shallow utilities (water, gas, electric) or septic systems or near large trees. Locate utilities before digging by calling Underground Service Alert at 811 or (800) 227-2600.
5. The rain garden must not block walkways and pathways, and not impede window egress or safe passages for travel.
6. Simply diverting water into a garden does not qualify for a rebate. Nor does replacing a downspout with a “rain chain”. You must create a designated rain garden.
7. An overflow area should be incorporated downslope of the rain garden. This should move excess water away from the building's foundation and should not flow to any neighboring property. The rain garden should not overflow directly into a creek or natural waterway.
8. Rain garden area must be excavated to a minimum depth of 6 inches for puddling.
9. An additional 12 inches of soil beyond the 6-inch excavation must be amended with 3 inches of compost. These 3 inches can also be replaced with a bioretention soil mix (a mixture of fine compost and mineral aggregate) for heavy clay soils. To maintain an even 6-inch depth, consider using a string level.
10. The excavated rain garden should be covered with at least 2-3 inches of dense mulch or a combination of gravel/river rock. This prevents erosion and minimizes weeds.
11. If water enters the garden quickly, include at least 3 feet of gravel or river rock at the entry points to prevent erosion. 
12. A licensed contractor is required to install the rain garden.

The ideal size of a rain garden is based on the size of the roof area flowing into the garden. Only the roof area from where rainwater is diverted should be considered. This area can be calculated by using a bird’s eye view of the roof. To view an aerial image of your roof, use a web navigation tool like Google maps.

Rendering Created by Valley Water

After you determine your roof area, use the following table to determine the ideal rain garden size: 

NOTE: Projects diverting roof or other impervious areas larger than 2,000 square feet should add 20 square feet of rain garden surface area per every 500 square feet of additional roof/impervious area. Sizing is based on the guidelines prepared by BASMAA (2012).

Rescape Qualified Professionals Directory
Rescape regularly updates a directory of local contractors that have completed their qualifying trainings. These trainings use a sustainable, holistic approach to the design and management of a landscape. They work with nature to conserve water and soil, reduce waste, and prevent pollution. You can find a Rescape Qualified Professional near you in this directory. The City is not responsible for any damage or construction mistakes caused by a contractor, landscape professional or any other individual.

Most rain gardens will not require any City of Palo Alto building permits. However, projects that require moving more than 100 cubic yards of soil may need a grading permit. This is a large quantity of soil, and most residential rain gardens will not meet this requirement. If you have any questions, contact the City's Development Center at (650) 329-2496 and select Option 3 for Building Plan Check Team when prompted.

The Bay Area Stormwater Management Agencies Association (BASMAA) has published a guide to understanding, installing, and maintaining rain gardens. Applicants can access this Rain Garden Guide online. The guide suggests these following steps to maintain a rain garden:

• Rain gardens should be irrigated during dry months, especially while plants are getting established. Plants should be inspected for health regularly, and weeds should be removed as often as possible
• Apply about 2-3 inches of mulch and replace as needed. Mulch with a material that will not float away such as compost or a larger sized hardwood mulch (avoid microbark, for example)
• Areas of erosion should be repaired. Stabilize the eroding soil with ground cover, or use energy dispersion techniques (e.g., splashblock or cobbles) below downspouts
• Avoid using synthetic fertilizers or herbicides in your rain garden. These chemicals are water pollutants
• Standing water should not remain in a rain garden for more than 3 days. Extended periods of flooding will kill vegetation and may attract mosquitos or other pests

• Ideally, the rain garden location should be a flat or gently sloped area downslope from the building.
• Avoid locating the rain garden in areas that stay soggy or have poor drainage. Avoid large tree roots.
• For clay soils, increase the area of the garden. Consider adding soil amendments, such as compost or pumice, 6-24 inches below the ponding area. Do not use mason or ballfield sand.
• Soil type also affects the water infiltration rate. Soil should be amended or replaced as needed.
• Drought and flood resistant native plants are highly recommended. A variety of species should be planted. Avoid invasive plants. Follow the Valley Water Rain Garden Qualified Plant List for recommendations. A list of invasive species can be found at the California Invasive Plant Council website (www.cal-ipc.org).

• Rain Garden Rebate Requirements, Valley Water.
  Rain Garden rebates must meet the specifications published here by Valley Water.
• Rain Garden Fact Sheet, SCVURPPP, 2012
  This resource, provided by the Santa Clara Valley Urban Runoff Pollution Prevention Program, details additional information on the design and maintenance of rain gardens.
• Coastal California Rain Gardens, University of California, Agricultural and Natural Resources, 2015.
  This guide explains more about the design of rain gardens, as well as information on choosing which plants to use.