Your home and garden can help protect San Francisco Bay by minimizing pollution from storm water during rainy winter months.
The rainy season brings a surge of pollution into the Bay. During storms, roofs, paved driveways, sidewalks, roads, and parking lots send rainwater rushing into gutters and storm drains. Along the way, the rain collects trash, oil, pesticides, fertilizers, and other pollutants. In most Bay Area communities, water that flows into storm drains doesn’t get treated at a wastewater treatment plant. Instead, storm water, laden with all the pollution it collects, gets emptied directly into creeks and sloughs that flow into the Bay, or into the Bay itself.
Storm water pollution is one of the largest sources of contamination in the Bay. It is also difficult to control, because it comes from so many places and picks up so many different kinds of pollutants.
Keeping rainwater from leaving your property and picking up pollution on its way to the Bay is a small step. But with seven million people living in the Bay Area, small steps add up. The home and garden projects below all help reduce rainy-season pollution in the Bay, and they also help conserve water and prevent flooding.
1. Install a rain barrel. Rain barrels are easy, low-cost ways to collect and use rain water to irrigate a garden. Rain runs from roof gutters to a pipe that empties into a barrel. A screen keeps the barrel free of leaves, debris, and mosquitoes. Near the barrel bottom, a hose is attached for irrigation. Roofs are an amazing source of water. In an average rainfall year, a 1,000 square-foot roof in San Francisco can collect over 13,000 gallons of rain. Rain barrels typically hold 50 to 100 gallons; you can install more than one. Larger storage tanks, called cisterns, can be installed above or below ground.
2. Install a rain garden. A rain garden is a landscaped area planted with wild flowers and other native vegetation that soaks up rain that flows off a roof, driveway or other impermeable surface. In a storm, the rain garden fills with a few inches of water that slowly seeps into the soil, where pollutants are filtered naturally. Rain gardens absorb 30% more water than the same area of lawn.
3. Install a rain patio. Rain patios work similarly to rain gardens. Baykeeper Executive Director Deb Self has a backyard patio with a permeable surface of layered gravel that absorbs rain that falls on the roof of her home. The roof drain pipe, which used to send water into the street, now leads to the patio. Once the rain reaches the patio, it sinks into a gravel-filled hole below. From there, water percolates into the soil for natural pollutant filtering.
4. Repave your sidewalk or driveway to absorb rain. If your sidewalk or driveway needs replacing, consider new paving materials that keep rain from running off into the gutter. A special kind of concrete called pervious concrete allows rain to pass through into the soil below. Another option is interlocking concrete pavers separated by joints filled with small stones. The small stones provide habitat for beneficial microorganisms that break down pollutants in rainwater.
5. Put in a graywater system. Graywater systems are a way to go beyond capturing rainwater, and irrigate a garden with used water from washing machines, showers, and sinks (but not toilets). Graywater systems vary, but most have a valve that can be switched to direct the graywater into a garden or back to the sewage system. Using biodegradable soaps—without bleach, boron, dye or salts—keeps graywater safe and fertilizes plants. Graywater can be used to water fruit trees and other edible plants, as long as it doesn’t come into contact with the edible parts. Harvesting graywater keeps relatively clean water out of sewage treatment plants, so less treated water is released into the Bay. A home with a graywater system also needs less piped water, and can save as much as tens of thousands of gallons of freshwater.
Resources for Bay-Friendly Home and Garden Projects
Urban Farmer Store
Rainwater harvesting equipment and training workshops at stores in San Francisco, Richmond and Mill Valley. Richmond store has discounted rain barrels for Oakland residents.
Sonoma County Master Gardeners
Information on building rain gardens.
A demonstration home and garden with a graywater system, rainwater cistern, plus many more ecological features; offers classes and tours.
Interlocking Concrete Pavement Institute
Information on local contractors who install paving that absorbs rain.
Information on systems for using water from washing machines, showers and sinks to irrigate plants. Classes for do-it-yourselfers and listings of Bay Area trained professional installers.
Photo by kierkier (Flickr/CC)