Pollution Prevention & Reducing Runoff

When it's home-and-garden project season, how about some that improve watershed health and look good at the same time?

You can incorporate Low Impact Development (LID) measures into your property to slow, spread or sink runoff. While your individual projects may seem like isolated efforts, collectively, these LID techniques can produce substantial water quality benefits.

  • Minimize impervious surfaces. If you’re thinking about extending your driveway, adding a walkway, or paving a sideyard, consider using permeable pavers or gravel instead of pouring a concrete driveway.
  • Disconnect your downspout. If you have a downspout connected to a drainpipe that directs rainwater from your roof directly to the street gutter, disconnect it. Instead, direct the rainwater to a nearby vegetated area other permeable surface like pavers or a gravel bed.
  • Amend your soil. Soil amending is an important low impact development technique. It is essential where there is clay soil, which has a very slow infiltration rate. Add compost or other organic material to your soil, which is often compacted during construction. This will restore the soil’s health and its ability to infiltrate rainwater.
  • Create a bioretention cell or “rain garden.” A rain garden is a simply a strategically-located, shallow depression that captures and soaks up storm water runoff from your roof or other impervious areas around your home like driveways, walkways, and even compacted lawn areas. Rain gardens are attractive and are a good alternative to traditional lawn landscapes. Once established, they also need less maintenance than lawns as they do not need to be mowed, fertilized, or watered.

 Carefully choose the location of your rain garden. It should be at least 10 feet from the house, so infiltrating water doesn’t seep into the foundation. Rain gardens flourish in full or partial sun, and should not be placed directly under a big tree. If there isn’t already a naturally low area in your landscape, excavate an area about 6 inches deep. Amend the soil in the excavation with a blend of 20% organic matter such as compost, 50% percent sandy soil, and 30% percent topsoil, which will promote good drainage and help break down pollutants. Clay content should not exceed 10% of the soil mixture. The proper soil mixture will ensure that there is rarely standing water in your rain garden for more than a few hours, or a few days at most—too short a time to breed mosquitoes, which require about a week of standing water to reproduce.
In the depression, plant native, non-invasive species that are resistant to the stress from both brief periods of pooling as well as dry periods between rainfall events. For a list of plants, trees and shrubs suited to rain gardens in California, check out the Brooklyn Botanical Garden's list of rain garden plants, or this list of trees and shrubs for California rain gardens at Native Rain-Garden.com, or this Rain Garden How-To Manual for Homeowners from the Santa Barbara Clean Water Project.

Once the rain garden is established, maintenance generally includes only periodic mulching, pruning and thinning, and plant replacement. Be sure to inspect your rain garden periodically during and/or immediately after rainfall events to be sure the rain garden is working as designed.

For more information regarding the responsibilities of businesses to reduce the discharge of pollutants, pollution prevention methods and BMPs, and available guidance material, please contact Public Works at 707-588-3300 or email Public Works Management Analyst