King County, Washington

Lake Hills Interceptor Sewer Project

Project Overview:

The Lake Hills Interceptor Sewer collects and transports wastewater from homes and businesses in Bellevue to the South Treatment Plant in Renton, Washington. Like many agencies, King Couty has an aging infrastructure with many pipes beyond their useful service life. The Lake Hills sewer is over 50 years old. Based on CCTV and other inspection reports, the Lake Hills sewer was identified as having major corrosion that could compromise the structural integrity of the pipe. King County determined that this pipe needed to be repaired immediately to prevent overflows, service disruption or worse a pipe failure. King County identified a 7,200-foot section 48” and 54” pipe that would be repaired. Rehabilitation using trenchless technologies was preferred over dig and replace construction as trenchless methods provided a more cost-effective solution and could extend the service life of the existing sewer for at least 50 years. Many trenchless methods were initially considered.

However, due to the location of the project and concerns about disrupting businesses and residences, rehabilitation methods that required access pits or large construction footprints were eliminated from consideration. King County contacted SEKISUI SPR Americas to learn more about our Spiral Wound liners. Over the course of several months, SEKISUI worked with the design team to review the condition assessment reports, understand the objectives of the rehabilitation including hydraulic capacity requirements as well as conduct site visits to identify the location of the manholes and how the project would be sequenced. SEKISUI also obtained the agency’s flow monitoring reports to identify flow conditions in the 48” and 54” pipes during the dry season to determine if there was a window of low flow where crews could perform the lining function without flow management or by-passing. Unfortunately, the flows within this crucial interceptor consistently exceeded the 50% threshold. Thus, the agency decided that a full bypass plan would be required.

After completing our detailed review of the project, SEKISUI recommended that our SPR RO 91-22 ROS profile liner be used for this project. The SPR RO profile not only met the structural design requirements for the project but also met the post rehabilitation hydraulic capacity requirements. As a result, King County sole sourced this project to use only SPR RO.

Project Challenges and Solutions:

As the project was scheduled to go to bid and construction during the COVID pandemic, King County was concerned about the material being delivered on time as the liner was manufactured in Australia. Even though a bypass system would be set up, the county still wanted construction done during the dry weather season. Therefore, instead of waiting for the contractor to get a Notice to Proceed before they would issue a purchase order to SEKISUI, King County opted to purchase the material in advance of the bid and warehouse the spools of profile until the contractor who was awarded the project could begin construction.

Bid and Construction :

The project was advertised and bid on January 31,2023. James W. Fowler of Dallas, Oregon was the low bidder. After their successful installation of SPR RO on the Carolina Trunk Sewer for the City of Portland, OR., J W Fowler decided to train an additional crew for their Washington location. Training was done by Sekisui Rib Loc Australia and Sekisui SPR Americas. A technician from Sekisui was on site to support the contractor as needed during the training and lining operation. The project was scheduled to start in May 2023. However, the project was delayed for a few weeks until the bypass system was tested and operational. Once the bypass was up and running, the contractor was able to start the lining operation. The 54” diameters were first lined, then the 48” diameters. Weekly look ahead schedules were provided by the contractor and daily production reports were prepared by Sekisui technicians which kept the project on track. Once the project was up and running, the contractor made excellent progress and was able to meet the original production schedule and close out date required by the contract documents. The project was completed in October 2023 on schedule and on budget.

About Our Spiral Wound Installer

JW Fowler is a General Contractor based out of Dallas, OR. They provide heavy civil and tunneling construction solutions for municipalities, agencies, and private owners across the West Coast and beyond. Their capabilities include alternative delivery, tunneling and trenchless, industrial, utilities, and transportation, but at the end of the day, every project is a JW Fowler project.

Lake Hills Interceptor Case Study: