The objective of this project was to demonstrate Low Impact Development (LID) stormwater practices in Yakima County.
In addition to the demonstration project, a Regional LID Manual (PDF) was developed. Both are funded by a grant from the Washington state Department of Ecology with 25% matching funds from Yakima County.
LID is a stormwater management approach to minimize collection, runoff, and end-of-pipe treatment. The goal of using LID is to mimic a site's predevelopment hydrology by choosing design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source. LID practices include vegetated swales, permeable pavements, “green roofs” and “rain gardens.”
Design guidance and examples of LID methods are limited in semi-arid areas with dry summer - cold winter climates. Research shows that LID benefits are most effective in low and moderate rainfall conditions like those in Yakima. Demonstrating the effectiveness of LID infiltration practices such as porous pavements and amended soil bioswales would provide tangible evidence that LID is achievable in the local climate. These practices will help improve water quality problems of fecal coliform and elevated metals in an area with ESA listed fish species.
This demonstration project will validate the use of infiltration practices in the Yakima area, thus reducing stormwater runoff pollutant loading, and improving water quality. This project will be implemented from January 1, 2010 and completed December 31, 2014.