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Building a PNW Rain Garden: Your Complete Guide

The Puget Sound is beautiful, but it is fighting a constant battle against pollution. Polluted water compromises the habitats of fish, waterfowl, and other marine life.

Threats to our watershed affect all of us, which is why we’re going to use this post to talk about one thing you can do to improve water quality in our PNW community: build a rain garden. Keep reading for a breakdown of how pollution makes its way into our waters, how rain gardens can help address the problem, and how to build one of your own.

What’s the Problem?

Seattle and its surrounding municipalities are covered in something called “impervious pavement.” Sidewalks, roads, driveways and other paved surfaces prevent rainwater from filtering directly into the ground. Instead, the rain washes across the pavement until it can make its way to a stream or river. Along the way, it carries with it any pollutant it comes into contact with: car oil, sediment, chemicals, etc. Once these pollutants make it into the watershed, they are carried into the Puget Sound.

The solution is to counteract the effect of impervious pavement and find ways to filter water into the ground instead of allowing it to rush into our waters. One way you can do this at home is to build a rain garden.

What’s a Rain Garden?

Structurally, a rain garden is a shallow indent in your garden that is filled with porous soil and native plants that can withstand heavy water. You direct water from your drain pipes into the rain garden, allowing the garden to filter water for you. Soil acts as a natural filtration system, which means rain gardens are a great way to keep nasty pollutants out of the Puget Sound.

There are several benefits to building a rain garden in your backyard:

  • You divert pollution from streams, rivers and the Puget Sound

  • You prevent water from pooling or swamping other parts of your garden

  • Rain gardens provide habitat for friendly critters

  • Rain gardens allow native plants to flourish in your space

How to Build a Rain Garden

Here, we’ll outline the basic process of planning one of your own. To build a rain garden, you need to select a part of your garden that can collect water when it rains. If there is a section of your yard that sits downhill from your house, this is the best location. That way, gravity does the work!

You’ll need to dig a depression in the ground and add porous soil. Surround the indent with a berm, and construct piping or rockways that will allow water to funnel from your house toward the rain garden. The plot itself doesn’t have to be big — a rain garden one-tenth the size of your roof will do the trick.

Plant water-loving native plants in the soil. They will absorb the most water and will flourish in a wet environment. This will help water filter into your soil more quickly.

For more guidance and instruction, check out WSU’s guide on building a rain garden. This is also a great resource for rain garden maintenance tips!

Make a Difference in Your Watershed

By using this guide as a starting point, you are well on your way to building a rain garden in your own backyard. Our regional waterways, including the Puget Sound, will directly benefit from this action.

What are some other home projects that take care of our planet? Let us know in the comments!

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