HomeMy WebLinkAboutPN_Project 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
March 6, 2026
TO: Jill Ding, Senior Planner, City of Renton Planning
FM: Katie Simpson, Environmental Scientist III, King County River and Floodplain Capital Unit, Water
and Land Resources Division, Department of Natural Resources and Parks
RE: Cedar River Trail 1 Emergency Repair Project Narrative
LOCATION
The existing Cedar River Trail 1 revetment is north of State Route (SR) 169 and on the left
(south) bank of the Cedar River between RM 5.93 and RM 6.03. The southern portion of the
facility is partially 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 Cedar River Trail 1 revetment emergency repair project (Project)
is within Section 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 rock and riprap within the Cedar River and in the revetment
prism to stabilize the revetment. The project included removal of concrete debris from the
revetment; placement of approximately 320 cubic yards of 4-man rock mixed with light loose
riprap along an approximately 200 linear foot section. Of this rock and riprap placed, 210 cubic
yard of rock were placed above the ordinary high water mark (OHWM) and 110 cubic yards of
rock were placed below the OWWM.
To repair the revetment, approximately 9 Maple trees (<8” diameter at breast height [DBH]), 10
Douglas Fir trees (<4” DBH), and 1 6-stem Maple Tree (<12” DBH) were removed and placed in
the Cedar River. Immediately following the repair, 30 cubic yards of topsoil, grass seed, and
straw were spread in disturbed areas. In the near-term, project related ground disturbance
associated with the repair will be restored through a native vegetation re-planting plan
designed to stabilize soils, improve habitat function, and support long-term site resilience.
Below the OHWM, the repair did not change the character, scope or size of the original design.
Large rocks and riprap are present both upstream and downstream of the repair site that
stabilize the riverbank (Photos 1-4).
Photo 1. The CRT1 revetment was damaged during the December 2025 flood. Damage extents
highlighted in the white box required emergency repair.
Photo 2. CRT1 2021 bare earth model. The yellow line indicates the CRT1 facility length and the
pink line approximates the facility toe.
Photo 3. Post December 2025 flood CRT1 facility condition after vegetation clearing, prior to
repair. The yellow line indicates the CRT1 facility length and the pink line approximates the
facility toe.
Photo 4. Completed 2026 emergency repair at CRT1. The yellow line indicates the CRT1 facility
length and the pink line approximates the facility toe.