King County is developing a new treatment plant to service a growing area of King and Snohomish Counties, Washington. To convey flows to the Brightwater treatment plant, the influent pump station (IPS) and a series of new tunnels and interceptors are being constructed. The plant IPS is located approximately 2.5 miles upstream and connected to the treatment plant via a tunnel containing the influent force main and other pipelines. The new 170 mgd, 90-foot deep IPS has six centrifugal, two-stage, raw sewage pumping systems that utilize two different sized pumps. Upstream of the wet well is an 80-foot deep, 75-foot diameter influent structure that combines flows from two tunnels and includes a rock box to remove 3-inch and larger rocks before they are pumped.