North Creek Storage Facility

Construction on the King County North Creek Storage Facility was completed Spring 2004. The 6-million-gallon underground storage facility is now online to manage excess wastewater and reduce overflows in Bothell, Kenmore and nearby communities north of Lake Washington.

Construction began in November 2001 at 18707 North Creek Parkway South at the same site as the King County's North Creek Pump Station built in 1999.

The storage facility, which is designed to temporarily contain potential wastewater overflows, particularly during peak storms, will help to eliminate overflows into Lake Washington near Kenmore.

In April, the Construction Management Association of America (CMAA) honored King County and Vanir CM, Inc, with its 2004 Project Achievement Award for the project's outstanding construction management practices. The project was completed on schedule and within budget.

The North Creek project includes architecture that blends into the surrounding Bothell Business Park. In partnership with King County, the City of Bothell is considering building a park on top of the storage tank, doubling the use of the site.

The project is part of King County's North Creek Diversion Project, which was developed in 1986 to divert excess flows away from existing wastewater facilities that could not contain the flows. The North Creek Storage Facility is the last component of the diversion project, which also includes the North Creek Pump Station and the upgraded York Pump Station and conveyance pipelines. (For more information on the planning/design of the North Creek Diversion Project, refer to service area planning documents of the Conveyance System Improvement Program.)

Construction summary

The storage facility was constructed in the field directly in front of the North Creek Pump Station. It is about 200 feet wide parallel to North Creek Parkway, 330 feet into the property and 15 feet underground.

Construction occurred in phases, which included:

• Shoring and excavation of the site throughout the project
• Construction of the reinforced-concrete structure and overflow pipe work in several phases
• Backfilling and removal of the shoring as phases were completed
• Final site restoration and landscaping.

Shoring and excavation were undertaken primarily during the first six months of construction and but also in various phases throughout the project as portions of the facility were completed. Construction of the reinforced-concrete portions of the facility followed over the next 18 months.