Rain gardens are non-engineered, shallow, landscaped depressions with compost-amended soils and adapted plants. The depression ponds temporarily store stormwater runoff from adjacent areas. A portion of the influent stormwater passes through the amended soil profile and into the native soil beneath.
New state regulations and a decades-old interlocal agreement are spurring Thurston County’s urban jurisdictions to innovate and collaborate on reducing stormwater runoff, the leading contributor of pollution of Washington’s urban waterways.
The state Department of Ecology’s newly revised municipal stormwater permit requires Thurston County, Lacey, Olympia, Tumwater and other urban municipalities across the state to review their development codes and identify changes that support a low-impact development (LID) approach to new construction and reduce water pollution. Put simply, LID mimics the natural water cycle of the landscape by minimizing impervious surfaces, maximizing native vegetation retention, and filtering stormwater on site as much as possible.
Per a 1995 memorandum of understanding, Thurston County’s development code must reflect Olympia, Lacey and Tumwater standards for the unincorporated urban growth area (UGA) that each city plans to annex. To comply with the local MOU and state permit, the four jurisdictions embarked on a unique partnership in 2014 to coordinate their LID code-review efforts. Municipal planners, engineers and other technical experts attended training jointly and met up at TRPC periodically to share progress reports and information resources.
The collaboration is beginning to bear fruit. The Thurston County Planning Commission recently completed a review of draft LID code changes for the unincorporated UGAs and rural parts of the county. The Board of County Commissioners is slated to consider the LID code changes by the end of 2016.
“The Low Impact Development Code changes are a step forward to enhancing our county’s water quality,” said Thurston County Commissioner Sandra Romero.
Reducing stormwater runoff will help the region achieve the Sustainable Thurston priority goal of protecting and improving water quality, including groundwater, rivers, streams, lakes and Puget Sound.
Within Sustainable Thurston’s Investment chapter, Action WI-3.6 calls for encouraging “innovative and creative solutions for addressing stormwater runoff.”
Toward that end, Thurston County and the cities have proposed code changes, such as reducing the aisle width in parking lots, requiring native or drought-tolerant landscaping, and allowing more pervious materials that enable rain to soak in where it falls.
To learn more about the project and explore an interactive map of some of the region’s LID projects, visit www.trpc.org/LID.