Pump Station Rehabilitation & Replacement Project
Project Status
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Project Details/Neighborhood
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Sewer Pump Stations (PS)s 19, 20, 21, 22, and 23 will be rehabilitated under this project.
- Due to the scale and complexity of the work, the City will take a phased approach, replacing one PS every two years.
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PS 20, located at 8790 85th Avenue SE at the southern tip of Mercer Island and along the Lake Washington shoreline, is in the poorest condition, so it will be the first to be rehabilitated.
Background
Mercer Island operates 18 sewer pump stations, which are located close to the shoreline (generally within 50 feet) and are used to convey flow through the City’s sewer lake line to King County’s South Pumping Station. The pump stations are constructed of concrete and are similar in design with most being a wet well/dry well configuration. There have not been substantial upgrades to the pump stations since their original construction in the 1960’s, except for pump station 4 (built in 2010), pump station 14 (rebuilt in 2014), and pump station 11 (currently being rebuilt by King County). Throughout the years the City has conducted regular maintenance of these pump stations, however rehabilitation or replacement (R&R) is imminent – some stations have capacity concerns while others have failing walls. In 2015, City staff conducted a pump station condition assessment, rating each station based on the consequence of failure. Most recently, in January of 2024, RH2 Engineering completed an assessment report which analyzed, ranked, and prioritized improvements for the five poorest condition stations. The assessment identified pump station 20 as being the most in need of rehabilitation.
Description
The work under this project includes various mechanical, structural, and electrical upgrades to rehabilitate the City’s sewer pump station 20. Replacement of existing pumps, fittings, piping, and valving, interior grating, vents, interior coatings, motor control panels, electrical service disconnect, distribution panels, circuit breakers, lighting transformers, and conductors serving the station are just a few of the improvements identified as necessary to extend the station’s service life another 50 years.
Project Timeline
PS 20: Planning/Design (May 2024 – January 2025)
Under Construction (February 2025 – July 2026)
Completed (July 2026)
PS 21: Tentative 2027-2028
PS 19: Tentative 2029-2030
PS 22: Tentative 2031-2032
PS 23: Tentative 2033-2034
Estimated Budget
$5,270,000 (PS 20)
Contact
Christopher Marks, City of Mercer Island Utilities Engineer: chris.marks@mercerisland.govs
SU0128 project location (2 MB)