2020 Watercourse Stabilization Project
Project Status
Click here for the latest updates on the project.
Project Details/Neighborhood 
Schedule A: West of West Mercer Way near 6110 Block
Schedule B: East of 3990 92nd Place SE
Project Type
Watercourse Stabilization
Description
The 2020 Watercourse Stabilization Project combined two separate capital improvement projects into a single contract for construction. The two individual projects as adopted in the 2017-2018 Capital Budget for initial design, and in the 2019-2020 Capital Budget for permitting, design development and construction are:
Sub Basin 29.2 Watercourse Stabilization Project (as Schedule “A”)
Sub Basin 3b.4 Watercourse Stabilization Project (as Schedule “B” )
A brief description of the work is outlined below:
Schedule “A” – Stabilize and control bank and severe channel erosion at downstream end of a broken culvert off West Mercer Way, for approximately 100 LF with streambed materials, logs, and native vegetation. The broken culvert section will be repaired and reconnected.
Schedule “B” - Stabilize and control bank and channel erosion at downstream end of the existing storm pipe outfall for approximately 80 LF with streambed materials, logs, ecology blocks, and native vegetation.
Project Timeline
Construction to begin in mid-July 2020. All in-water works shall be completed within 40 days for both sites. Replanting work will take place in early October for optimal planting weather condition.
Estimated Budget
Total project budget including design, permitting, project management and construction is set at $309,594.
Project Status
On-going.
Impact to Residents
During equipment and material transfer to the staging area off the roadway, temporary traffic disruption may occur. One lane of traffic may be closed for short periods of times. Most of the works occur off the roadway, no other utilities are expected to be affected.
Note
Please be cautious when driving by the construction sites.
Background
The City assesses our watercourse condition on regular basis. CIP project needs are prioritized accordingly to ensure erosions (as pollutant) are minimized while streambeds are stabilized which indirectly prevent future soil movements. Due to anticipated in-water work, the project is required to obtain permit approvals from the United States Army Corps of Engineers (“USACE”) and Washington State Department of Fish and Wildlife (“WDFW”). A condition of the HPA is that in-water construction can only occur between June 16 and September 30 (also known as the approved fish-window).
Contact
Fred Gu, CIP Project Manager: (206) 275-7803 or fred.gu@mercergov.org
Status Updates
September 8, 2020 Update: All in-water works are completed last week at Site B, right before the Labor day weekend. Work completed there include installing energy dissipating blocks at the pipe outfall, more than 80 LF of boulder cascade, streambed material and logs with rootwads. Green Earthworks Const. Inc. will return in October to complete re-planting for both Site A and B.
A few photos are included here.
August 3, 2020 Update: With in-water work mostly completed at Site A, this week, Green Earthworks Const. Inc. will switch their focus to Site B. Materials will begin to delivery to the staging area north of Mercerwood Drive by 9300 block.
Work completed at Site A include repairing of the cross-culvert end piece. This work is crucial to the stability of West Mercer Way. Also, more than 140 tons of streambed material and two logs with rootwads have been installed in this highly eroded channel. The contractor was able to construct the project by safely maneuver their small equipment in this steep and narrow channel. A few photos are included here.
July 20, 2020 Update: This week, Green Earthworks Const. Inc. will begin mobilizing and setting up at Site A. Streambed materials will be transferred to the staging area off West Mercer Way near 6110 block
2020 Watercourse Stabilization Map (829 KB)