Rain Garden Handbook

A Guide for Design, Installation, and Maintenance Rain Garden Handbook for Western WashingtonRain Garden Handbook for Western Washington Funding for this project was provided by the Washington State Department of Ecology through the Municipal Stormwater Grants of Regional or Statewide Significance program, Grant No. GG12015. Curtis Hinman, Washington State University Extension, served as the principal author. Kitsap County managed the project. A Guide for Design, Maintenance, and Installation JUNE 2013Acknowledgements Principal Author Curtis Hinman Washington State University Extension Faculty, Green Stormwater Infrastructure Specialist and Green Stormwater Infrastructure Program Lead Advisory Committee and Contributors Teresa Brooks Kitsap Conservation District Peggy Campbell Snohomish County Michael Carey City of Tacoma Mindy Fohn Kitsap County Dan Gariépy Washington State Department of Ecology Erica Guttman Washington State University Extension, Thurston County David Hymel Rain Dog Designs Marilyn Jacobs Rain Dog Designs Colleen Miko Washington State University Extension, Kitsap County Zsofia Pasztor Innovative Landscape Technologies; Edmonds Community College Mandi Roberts Otak, Inc. Bob Spencer Seattle Public Utilities Editing, Sizing Tool Development, and Graphic Design Marissa Chargualaf Otak, Inc. Cheyenne Covington Finis Ray Mandi Roberts Neil Schaner Mark Shelby Sharlene Sherwood A special thank you to Garry Anderson, AnderDesigns, who created several illustrations in the 2007 handbook that have been adapted for this edition. Sources of photographs are listed with each. Background photograph on cover is from www.istockphoto.com.David HymelTable of Contents INTRODUCTION How Rain Gardens Enhance Our Natural Environment and Quality of Life......................................................................2 What is a Rain Garden?...............................................................3 Rain Gardens As Part of the Overall Approach to Low Impact Development........................................................4 Rain Gardens Provide Multiple Benefits......................................5 Four Stages to Create & Sustain a Rain Garden.........................6 Recommended Timeline..............................................................8 1 PLAN How to Get Started....................................................................10 Check Site Drainage..................................................................11 Where to Locate Your Rain Garden...........................................12 Where Not to Locate Your Rain Garden.....................................13 Test Your Soil............................................................................15 Determine the Size of Your Rain Garden...................................18 Rain Garden Sizing Chart..........................................................21 Rainfall Regions for Western Washington............................22-23 Determine the Shape of Your Rain Garden...............................26 2BUILD Prepare for Construction...........................................................28 Locate and Design the Inflow....................................................29 Always Provide an Overflow.......................................................29 Rain Garden Cross Section.......................................................30 Lay Out.....................................................................................31 Excavate...................................................................................32 Create a Flat, Level Bottom......................................................40 01 0927 PLANBUILD INTRO David Hymel Erica GuttmanDavid HymelInstall the Inflow........................................................................41 Place the Rain Garden Soil Mix................................................41 Protect the Inflow and Overflow................................................42 Edging......................................................................................42 3PLANT Prepare to Landscape Your Rain Garden..................................44 The Benefits of Plants..............................................................45 Planting Zones..........................................................................45 Landscaping Guidelines and Suggestions.................................46 Mulch........................................................................................50 Sample Planting Plans..............................................................51 4MAINTAIN Keep the Water Flowing............................................................56 Minimize Exposed Soil and Erosion..........................................56 Provide Routine Maintenance....................................................57 Maintenance Checklist..............................................................61 APPENDICES Appendix A: Plant List............................................................A-1 Appendix B: Other Resources and Websites...........................B-1 Appendix C: Introduction to Washington State Department of Ecology’s Requirements for Rain Gardens in Western Washington........................................C-1 43 PLANT 55 MAINTAIN Tips Look for these boxes with helpful tips and information throughout the handbook. Local and State Requirements Alert This box reminds you to check local and state requirements, including Department of Ecology Stormwater Minimum Requirements, that may apply to your project. Tools and Materials Checklist These checklists are provided to help you gather the tools and materials you may need in each stage of creating your rain garden.  Erica Guttman Erica Guttman1 I n t r o D U C T I O N This handbook will guide you through the following stages: PLAN, BUILD, PLANT, and MAINTAIN. The handbook is written for conditions specific to western Washington, including appropriate plant selections and sizing recommendations based on regional soils and rainfall patterns. • How Rain Gardens Enhance Our Natural Environment and Quality of Life • What Is a Rain Garden? • Rain Gardens As Part of the Overall Approach to Low Impact Development • Rain Gardens Provide Multiple Benefits • Four Stages to Create & Sustain a Rain Garden • Recommended Timeline In this Section David Hymel Background Image: David Hymel2 Native soils and forests of western Washington absorb, store, filter, and slowly release cool, clean water to rivers, streams, wetlands, lakes, and coastal waters. The rich diversity of life in marine and fresh water, as well as on land, depends on clean water to thrive. How Rain Gardens Enhance Our Natural Environment and Quality of Life As the region grows, native forests and soils are replaced with roads, rooftops, and other hard surfaces. When it rains or snows, more water flows from these hard surfaces than undisturbed areas, carrying oil, fertilizers, pesticides, sediments, and other pollutants downstream. In fact, much of the pollution in streams, wetlands, and Puget Sound now comes from stormwater flowing off developed areas. The added water and associated pollutants from developed lands are damaging water resources and harming aquatic life in western Washington. 2 How You Can Help You can make an important contribution by reducing the amount of stormwater and pollutants coming from your property and entering our region’s waterways by installing rain gardens in your yard and other places throughout your community. iStockphoto.com iStockphoto.comiStockphoto.comiStockphoto.com Curtis Hinman3 A rain garden is a landscaped area that collects, absorbs, and filters stormwater runoff from roof tops, driveways, patios, and other hard surfaces that don’t allow water to soak in. Rain gardens are sized to accommodate temporary ponding after it rains and are not meant to be permanent ponds. Simply put, rain gardens are shallow depressions that: • Can be shaped and sized to fit your yard. • Are constructed with soil mixes that allow water to soak in rapidly, treat runoff, and support plant growth. • Can be landscaped with a variety of plants to fit the surroundings. What Is a Rain Garden? Anatomy of a Rain Garden PONDING DEPTH (6” or 12” typical) OVERFLOWGRADUAL SIDE SLOPES MULCH LAYERTOP SURFACE OF PONDING AREA INFLOW RAIN GARDEN SOIL MIXEXISTING SOILNext >

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