top of page


Ship Canal Water Quality CSO Pump Station 

Seattle Public Utilities

Seattle, Washington
Estimated Cost:
$31.5 million
Value Analysis
Market Sector:
Facility Specialty:
Combined Sewer Overflow - CSO


The main components of the Ship Canal Water Quality Project include the storage tunnel and appurtenances, conveyance facilities to convey SPU and Department of Natural Resources and Parks Combined Sewer Overflow flows into the tunnel, the tunnel effluent pumping station (TEPS), and a tunnel pumping effluent line to drain flows away from the tunnel.  A deep storage tunnel was constructed between the Ballard and Wallingford CSO areas, on the north side of the Ship Canal for offline storage. ​The total control volume for both SPU and DNRP CSO basins is 15.24 MG.

MENG Analysis developed $31,846,000 worth of cost saving proposals.


The TEPS drains the stored combined sewage from the SCWQP Storage Tunnel after a combined sewage storage event. The TEPS is located at the West Shaft site, at the western end of the Storage Tunnel, and will be constructed within the shaft used to construct the tunnel.

The configuration of the TEPS contains a single shaft layout with construction of a circular dry well within a larger circular wet well. The wet well is the annular space between the exterior wet well wall and the dry well shaft. 

The below-grade dry well accommodates, from the bottom to the top, the Grit Pump Level, Tunnel Dewatering Pump Level, Flow Meter Level, and the Odor Control Level. The two-story TEPS building above-grade is located on top of the TEPS underground structure. The building accommodates the solids and grit handling bay, utility water system, dry well access and equipment lifting area, electrical and control room, standby generator room, and HVAC and other building mechanical support systems.

The tunnel pumping station effluent line consists of an approximately 1,900 lf force main to discharge the stored tunnel CSO flows directly into DNRP’s existing Ballard Siphon wet-weather barrel forebay.

bottom of page