Stormwater Engagement

This engagement project covers areas within Milton-Freewater City Limits, the Urban Growth Boundary (UGB), and regions outside the UGB in Umatilla County—specifically the Highway-11 (S-1) and Nichols Canyon (S-2) drainage areas. The Walla Walla Basin Watershed Council (WWBWC) has previously been contacted by one resident of the S-2 drainage with concerns about stormwater runoff in this area. This concern was twofold; 1) it causes mild flooding within the drainages and 2) water quality in the Walla Walla River is affected. While stormwater runoff is not necessarily a year-round threat in our location, water quality impacts do approximately align with various lifecycle stages of critical species within our basin. The region is anticipated to receive more precipitation as rainfall and the snow that may still fall is likely to melt more quickly; both factors will lead to an increase in runoff events. This project will focus on engaging with the home and landowners, relevant local and state agencies, and other project partners within S-1 and S-2 drainages regarding green stormwater infrastructure (GSI) possibilities within the area. Efforts will include outreach events, educational materials, and one-on-one and group meetings with landowners to discuss the need for and potential benefits of GSI installation.

While this engagement will lead to restoration of Instream and Riparian areas, the estimated cost of that habitat restoration could not be anticipated at proposed.

The proposed project will initiate the necessary engagement with landowners and other partners to result in the implementation of GSI treatment(s) within the area. The S-1 and S-2 areas contain two stormwater outfalls into the Walla Walla River, which is utilized by summer steelhead, bull trout, and spring Chinook salmon. Numerous aspects of untreated stormwater negatively impact water quality, subsequently negatively impacting the health of all organisms within it.



Studies have shown that steelhead and Chinook salmon are the second and third most sensitive salmonid species in the Pacific Northwest to untreated stormwater. Research suggests this is due to the presence of the compound 6ppd-quinone as a result of tire particle contamination. This occurs when stormwater events wash over highways such as Highway-11, which slopes rapidly into the southern boundary of Milton-Freewater, and carries substances into nearby waterways. In addition to the microscopic tire particulate, other chemicals that have leaked from vehicles as well as fluid and solid applications (deicers) are washed into the system during these events as well. Undesirable metallic particles can increase in presence after runoff events not only from particles shorn from brake pads washing in, but metals can be mobilized through reactions between deicing components with the surrounding ground. Lastly, there are nearby fields and areas of soil without cover which allows for mobilization of soil, allowing excess sediment to enter the river.



Ultimately, treatment of stormwater from this area will reduce sediment, copper, and other toxic contaminants entering the mainstem Walla Walla River while enhancing infiltration into the groundwater system, slowing water down, and retaining it within the system. The proposed project will develop relationships with landowners and relevant entities necessary to follow through with GSI design and installation.