Sub-Basin 29.3 and 34.1 Watercourse Stabilization
Project Status
To help keep area residents informed of our construction progress, we will post project updates to this site on a regular basis. Click here to see status updates.
Project Details/Neighborhood
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SW0112 8200 Block of West Mercer Way, Project is along open watercourse from West Mercer Way to Lake Washington
SW0114 6200 Block of West Mercer Way, Project is along open watercourse from SE 65th Street to West Mercer Way
Background
Stream banks have eroded over time, causing significant sedimentation downstream.
Description
SW0112 (Sub-Basin 34.1) – channel restoration and outfall protection.
SW0114 (Sub-Basin 29.3) – stream restoration and bank stabilization with use of stream boulders, cobbles, and logs.
Project Timeline
Planning/Preliminary Design 2024
Final Design/Construction 2025
Estimated Budget
SW0112 (Sub-Basin 34.1) - $25,000 for assessment and initial design in 2024
SW0114 (Sub-Basin 29.3) - $50,000 for assessment and initial design in 2024
Contact
Elayne Grueber, P.E, Capital Project Manager: elayne.grueber@mercerisland.gov
Status Updates
September 2024
The City hired Natural Systems Design (NSD) to complete the design work for Sub-basin 29.3. The initial kick-off project meeting with the NSD design team and City staff was completed. The design team is planning field and survey work, which is expected to take place over 2 to 3 days in mid-October. The City has also notified residents in the vicinity of the upcoming work to keep them informed.
August 2024
Based on the condition assessment report from the consultant, Northwest Hydraulic Consultants, the City has determined to begin remediation efforts at Sub-Basin 29.3. Sub-basin 34.1 will continue to be monitored but no remediation work will be undertaken at this time.
The City is in the process of selecting a consultant to begin the design phase for the remediation of Sub-Basin 29.3.
June 2024
NHC submitted a condition assessment with recommendations for watercourses in Sub-Basin 29 and Sub-Basin 34.
Sub-Basin 29, NHC reported that the watercourse appears to be actively incising with ongoing erosion of the channel bed. NHC recommended the implementation of a Capital Improvement Project aimed at stabilizing the channel. The City is currently in the process of procuring the services of an engineering firm to design improvements for this watercourse.
Sub-Basin 34, NHC reported minimal change in watercourse conditions compared to previous investigations. NHC recommended continued monitoring and assessment of this watercourse.
May 2024
The consultant, Northwest Hydraulic Consultants (NHC), completed an assessment of the watercourses in April. Their assessment included fieldwork to survey the condition of the watercourse. NHC is currently completing a condition report to summarize their findings. The report for both basins is expected in June.
February 2024
Northwest Hydraulic Consultants has been contracted to complete a condition assessment to confirm the current watercourse condition and verify project needs.
SW0112 project location (234 KB) SW0114 project location (197 KB)