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For questions about the Conveyence System Improvement Program, please contact Mark Buscher 

Wastewater Treatment Division
King Street Center
201 S. Jackson St., Suite 505
Seattle, WA 98104-3855

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Initial CSI basin planning, 1999-2003

Hidden Lake planning area

The Hidden Lake Service Area includes all sewered areas that drain to the County's Hidden Lake Pump Station and all downstream neighborhoods that drain to the Boeing Creek Trunk and Richmond Beach Pump Station located in the western part of the City of Shoreline. As the sewered population has grown over the past 40 years and the sewer infrastructure has aged, a number of wastewater conveyance concerns have arisen:

  • The pumping capacity of the Hidden Lake Pump Station and the hydraulic capacity of the Boeing Creek Trunk are insufficient to convey peak wet weather flows to the County sanitary sewer standard of one overflow per 20 years.
  • Sulfide-related corrosion and odors have been a problem at the Hidden Lake Pump Station and in the downstream piping.
  • There have been backups into the local system from the Boeing Creek Trunk.

Planning was completed in the Hidden Lake basin in 2000. Wastewater planning for the service area is driven more by the need to address the immediate concerns of alleviating the operational difficulties at the Hidden Lake Pump Station, managing peak wet weather flows while anticipating the effects of future sewer deterioration, and controlling odor, rather than accommodating future growth.

Any wastewater service improvement plan must also include enough flexibility to work with the results of the County's Brightwater Project and its Regional Infiltration and Inflow (I/I) Reduction Programs. These will help refine the projected peak design flow, the costs and feasibility of I/I reduction, and the most efficient means of wastewater routing.

Working alternatives for this basin include constructing a new Hidden Lake Pump Station with an upstream storage facility and pipeline replacement along the Boeing Creek Trunk and targeting infiltration and inflow reduction as part of the District and the County's Regional I/I Reduction Program. Predesign for this project was completed in February 2003 and final design should be completed in spring 2004.

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