Wastewater System Expansion
The King County Wastewater Treatment Division commissioned an exploration program to investigate options for upgrading the wastewater conveyance system served by the Sunset and Heathfield Pump Stations. Increased capacity is necessary to meet the demands of a growing population, and will allow King County to continue providing safe and reliable service.
King County Wastewater Treatment Division
Crux provided core drilling and sampling at nine borehole locations on the project. All work was completed within residential neighborhoods in Bellevue and Issaquah, and required significant experience working in restricted and congested areas. Close proximity to surrounding homes required additional permitting and impacted work schedules. Noise ordinances and traffic control were in effect throughout the project.
Subsurface conditions presented additional challenges, consisting of glacial outwash deposits, glacial tills, and highly fractured siltstones and sandstones. Several borings consisted of silts, sands and gravels near the surface, and transitioned to dense gravels and cobbles as drilling depth increased. Crux drilled a combined total of approximately 3,000 feet in these challenging conditions, including one 730-foot borehole that was drilled at 20 degrees from vertical.
Vibrating wire piezometers were installed in select holes, and Crux provided packer testing and downhole imaging services on as as-needed basis. All drilling was completed with minimal disturbance to nearby residents.