The Willamette Water Supply Program (WWSP) is a $1.5 billion drinking water infrastructure program that will provide Tualatin Valley Water District, the City of Hillsboro, and the City of Beaverton with a seismically resilient water supply to meet future demands and provide redundancy in case of an emergency event. It is the first seismically resilient water supply system in the State of Oregon and in the Pacific Northwest, designed to be operational for the magnitude 9.0 Cascadia Subduction Zone earthquake and 2,475-year Maximum Considered Earthquake events. The program includes more than 30 miles (48 km) of transmission pipelines (48 to 66 inches [1,220–1,675 mm] in diameter), a new Water Treatment Plant, and two terminal reservoirs.
Delve Underground has been working on this program extensively over the past 10 years. We have assisted the owners in the planning and routing study (2012); participated in preliminary design as geotechnical and trenchless leads (2013?2015); and since 2015 have been involved in numerous project elements as design lead or technical advisor. These services include trenchless crossing design; seismic design; determination of seismic risk of soil liquefaction and ground deformations; multiple geotechnical explorations; characterization of subsurface conditions; FLAC numerical modeling to evaluate seismic liquefaction, lateral spreading hazards, ground deformations; ABACUS modeling of soil-pipe interaction.
We also assembled a group of national experts on seismic resiliency and pipeline seismic analysis and design and developed a program-wide Seismic Guidelines and Minimum Design Requirements. This guideline set up the program’s level of service goals and provided a practical design solution/procedure to achieve the required seismic resiliency. This is the first detailed seismic design guideline in the Pacific Northwest Region and has been adopted by other agencies, such as Tualatin Water District, City of Hillsboro, Joint Water Commission, and latest by the City of Portland Water Bureau.