Project Scope

Design of a pump station to transfer up to 8.65-mgd combined sewer overflow (CSO) to the waste water treatment plant.  The sewer system in Kirkland was under sized for the current and potential future growth of the area resulting in the potential for millions of gallons of sewage overflow into Lake Washington during large rain storm events.

Project Details 

• Structural Engineer Chad Malone was lead structural engineer for this project.
• Worked with client from concept to completion on this project.
• Dealt with challenging geotechnical conditions by proposing a single structure to house the 2000 Kw generator, chemical injection, odor controls and pumping systems in-lieu of the original proposal of four separate buildings.
• Geotechnical challenges include, an upper aquifer with ground water at 4ft below grade, 30ft of liquefiable materials, a lower aquifer located 10ft below the base of the structure with a pressure head of 8ft above grade, the potential for the lateral spreading of several feet  during a seismic event. 
• This is a 4 story structure with 1 story above grade and 3 stories below grade, for a total structure depth of 61 ft.
• Designed 80 ft diameter by 70 ft deep secant pile shoring system.
• Designed support structure for a 10 ton Bridge crane on the ground floor and for two 3 ton jib cranes at the stage one level
• Designed two 3 ton monorails and their support structures for the Stage 1 and Stage 2 levels.
• Designed the 2000 KW Generator Room which is cantilevered as far as 15ft off of the circular foundation shaft below
• Designed concrete intake and exhaust ducts that penetrated and cantilevered from the circular shoring system 15ft below grade and extended up to 4 ft above grade.