New LID Stormwater Regulations for Washington State

New stormwater regulations have been coming to the forefront for many states, counties and municipalities throughout the United States.  These regulations are intended to help prevent stormwater pollution from entering streams, lakes, wetlands and waterways.

In Washington State, newly revised stormwater regulations will require many future developments to incorporate certain LID (Low Impact Development) methods.  Western Washington cities and counties are scheduled to have all codes in place by the end of 2016.  Eastern Washington is scheduled to have their codes updated by December 31, 2017.  

What is LID?
In a nut shell, LID (Low Impact Development) is a more natural approach to land development that helps minimize hydrologic disturbance to a site.  LID methods are designed to mimic rainfall absorption into the ground by means of a natural process.  Unlike traditional drainage techniques that collect and quickly transport water to streams and waterways,  LID methods slows water infiltration causing less damage to stream channels, wetlands, lakes and waterways.

LID methods frequently used by Landscape architects:
Rain gardens
Green roofs
Bio-filtration swales
Permeable pavements

What are the threasholds?
As stated in Washington State Department of Ecology’s Catching Rain Series, Western Washington LID measures are based on the size of development.  “In Western Washington most new developments that create 2,000 square feet of hard surface area or disturb more than 7,000 square feet of land will have some LID requirements.  Limited circumstances such as projects that discharge directly to large water bodies may reduce or eliminate the need for LID.  Projects in Western Washington will have two options for complying with LID requirements:  choose from a prioritized list of LID Best Management Practices (BMPs), or meet the Low Impact Development Performance Standard.  Projects of 5 acres or greater located outside urban growth areas must meet the LID performance standard.”

Bottom Line
The bottom line is, if you think your project will create 2,000 square feet of impermeable surfaces or disturb over 7,000 square feet of land, know your LID requirements.  Discuss your project with your local permitting officer or landscape architect in the early planning stages.  For more information, see Washington State Department of Ecology’s “2012 Stormwater Management Manual for Western Washington as Amended in December 2014”.  

Susan Combs Bauer, president of BauerCombs & Associates, Inc. - Landscape Architecture and Land Planning.  Located in North Bend, WA serving the greater Puget Sound areas and beyond. www.bauercombs.com