A draft of the SR-167 watershed characterization was completed in May, 2005 by WSDOT's watershed characterization technical team, the largest and most exciting to date. Reports for the other characterization projects can be found on the
watershed characterization page.
The SR-167 Draft Watershed Characterization Report is in Adobe Acrobat .pdf format and designed for double-sided printing. Some pages are intentionally left blank for correct printing.
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Addressing impacts (and potential watershed-based mitigation for those impacts) of future projects in the Green / Duwamish Watershed, these projects include a proposal to widen SR-167 from the intersection with I-405 in Renton, south to the SR-512 interchange. The highway lies almost entirely on floodplains and historic wetlands, and the basin is rapidly urbanizing.
This document presents the results of the SR-167 watershed characterization, serving several purposes.
- Providing options to consider for SR-167 project management teams when fulfilling regulatory requirements to treat stormwater flow control and to avoid, minimize, and compensate for unavoidable natural resource impacts of the transportation project.
- Providing technical information to the SR-167 team with for environmental documentation.
- Serving as a valuable mitigation resource to other management teams having transportation projects in the 350 square mile study area.
- Presenting a prioritized list of natural resource restoration sites which could be of great value to any group involved in restoration in the watershed.
- Documenting the continued development and refinement of watershed characterization methods.
At a landscape scale, the condition of natural systems generally transitioned from “not properly functioning” within the Kent / Auburn valley on the western or commercial / urban portions of the study area to a more “at risk” condition in the eastern parts of the study area. At the project scale, the SR-167 project will have substantial stormwater impacts and likely wetland and habitat impacts that will require compensation or mitigation.
In the study area, we evaluated nearly 4,000 riparian areas, over 1,700 wetland areas, 67 floodplain areas, and 10 stormwater retrofit sites for mitigation potential and environmental benefit. Of these sites, 1,026 potential wetland, floodplain and riparian restoration sites met our minimum criteria for potential use for mitigation.
This list serves as an initial screen for prioritizing each candidate site's potential to provide environmental benefits at both the site and landscape scales, however, additional site-specific work will be needed before selection of sites for restoration.
For more information visit contact:
Dick Gersib
(360) 705 7477
gersibd@wsdot.wa.gov