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HomeMy WebLinkAboutPN_TCB-Emergency-Repair-NarrativeWater and Land Resources Division Department of Natural Resources and Parks King Street Center 201 South Jackson Street, Suite 600 Seattle, WA 98104-3855 206-477-4637 TECHNICAL MEMORANDUM January 28, 2026 TO: Jill Ding, Senior Planner, City of Renton Planning FM: Grace Brennan, Environmental Scientist III, King County River and Floodplain Capital Unit, Water and Land Resources Division, Department of Natural Resources and Parks RE: Tabor-Crowall Emergency Repair Project Narrative LOCATION The existing Tabor-Crowall revetment is southwest of State Route (SR) 169 and on the right (north) bank of the Cedar River between RM 2.75 and RM 2.85. This facility is within the Renton (City) city limits, the Cedar-Sammamish Watershed Resource Inventory Area 8, and the Hydrologic Unit Code 171100120107 – Madsen Creek-Cedar River watershed subbasin. The Tabor-Crowall emergency repair project (Project) is within Sections 16 and 21 of Township 23N, Range 5E, Willamette Meridian. PROJECT DESCRIPTION The completed emergency repair project addressed damage sustained during the recent December 2025 flooding event. Scour and bank erosion in this revetment resulted in immediate, emergency risk to SR 169 and associated utilities, including a fiber optic line, that could have resulted in catastrophic failure. The project consisted of placing geotextile and rock within the Cedar River and in the revetment prism to stabilize the revetment. The project was done following BMPs, including installing silt fences after the site was cleared and covering stockpiles of topsoil with plastic sheeting. Once BMPs and safety measures were installed, geotextile was placed over the exposed soil in the erosional scarp. After geotextile placement, 307.93 total tons of 3 to 5 man-sized rock was placed on the revetment where erosion scour was occurring. Of this rock placed, 175 cubic yards were placed above the ordinary high water mark (OHWM) and 55 cubic yards were placed below the OHWM. Once the large rock was in place, 4-8” quarry spalls were spread over the top. Fifteen cubic yards of quarry spalls were placed above the OHWM, and 5 cubic yards were placed below. The site was then stabilized; topsoil and seed were spread and coir matting was installed above the revetment where lawn was impacted to reduce erosion risk. Below the OHWM, the repair did not change the character, scope or size of the original design. Large rocks and rip-rap are present both upstream and downstream of the repair site that stabilize the riverbank. Above the OHWM, the revetment is vegetated with English ivy (Hedera helix) and Himalayan blackberry (Rubus bifrons). This vegetation is rooted in soil, which may be underlain with large rock and quarry spalls. A larger project is in development at this location that includes the installation of dolosse and woody material on both the left and the right bank of this project, a habitat bench on the left bank, and the installation of native riparian vegetation. This emergency repair will be integrated into this larger project, which will result in increased habitat and ecological function at the site. Plans for integration into the next project are still in development, and King County intends to keep the City of Renton involved as it progresses.