How to build a rain garden — a creative, pollinator-friendly way to keep pollution out of Puget Sound

Vintage Pacific NW: We’re revisiting some of our favorite stories from some of our favorite former magazine contributors. Check back each week for timeless classics focusing on food, fitness, gardening and more.

Originally published April 12, 2017 
By Ciscoe Morris, former In the Garden writer

THE POPULATION OF the Puget Sound region is steadily increasing. Predictions are that by the year 2040, the number of households in our area will increase by nearly 30%. As population has expanded, forests and meadows have been replaced with rooftops, driveways and other hard surfaces that emit or collect pollutants, at the same time restricting the ability of rainwater to soak into the soil. 

According to many regional experts, runoff from these impervious surfaces is Puget Sound’s greatest source of pollution. Studies have shown that a high percentage of cadmium, zinc and arsenic found in the Puget Sound comes from runoff from roofing materials. 

At the same time, current climate models predict our region will experience more frequent and severe winter storms. With more households and more rain, we also can expect more polluted runoff. During a downpour, excess water from downspouts runs across lawns treated with pesticides and fertilizers; into an oily street; and, finally, down a storm drain that dumps the polluted water into streams, rivers or directly into the Sound. 

Storm water can overwhelm combined sewer and storm-drain systems, causing thousands of gallons of untreated raw sewage to flow directly into the Sound. All of this pollution endangers fish and other sea creatures, and jeopardizes the water quality. 

Homeowners can play a key role in helping to prevent this problem by installing rain gardens. Rain gardens are shallow, 3-foot-deep depressions featuring well-drained, spongy soil at the base, surrounded by a berm. The depression is planted with attractive, easy-to-maintain plants that can withstand having their roots submerged for short periods during and after rainstorms, while a variety of attractive trees, shrubs, perennials and annuals is planted up the berm and surrounding garden space. 

Polluted storm water from rooftops, driveways and other hard surfaces is diverted into the rain garden, where it is captured and cleaned. Pollutants are filtered out and absorbed by plant roots as the water percolates through the soil in the basin. 

In addition to preventing polluted runoff from entering our waterways, rain gardens create habitat for birds and butterflies and other pollinators. The reduction in runoff decreases flooding, recharges groundwater supplies, and prevents erosion in creeks and streams. 

Whether you build your own rain garden or hire someone to do the work, there are plenty of outstanding resources that can help you get started. The book “Rain Gardens for the Pacific Northwest,” written by renowned landscape designers Zsofia Pasztor and Keri DeTore and illustrated by Jill Nunemaker, contains all the information you’ll need to build your own rain garden from start to finish in any kind of soil condition. 

It also contains lists of spectacular plants and great design ideas. Stewardship Partners and WSU Extension have teamed up on the “12,000 rain gardens” project. Their goal is the creation of 12,000 rain gardens in our region. The website offers a wealth of information, including the indispensable “Rain Garden Handbook,” containing detailed information on how to plan, build, plant and maintain a rain garden. 

The site features information on free neighborhood workshops, trainings and opportunities to volunteer on community projects, and it lists competent professional contractors. Finally, the website offers information about rain-garden incentives, such as grants and rebate programs offered by local governments. If you build or have a rain garden constructed, definitely record it on the “12,000 rain gardens” site.