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Completed – July 2012

This I/I reduction project, completed in July 2012  , replaced side sewers serving 332 residential properties; repaired or replaced public sewer mains and manholes; and disconnected improper storm drainage connections to the sanitary sewer. King County and Skyway Water and Sewer District would like to thank all of the project neighborhoods for their patience! Their tolerance and flexibility throughout the project have been greatly appreciated by all who have been involved with and/or are benefited by this important improvement.

This project was managed and funded by King County in partnership with the Skyway Water and Sewer District  . There was no cost to property owners and participation was voluntary.

Not all properties in the project area were included in I/I rehabilitation work. Only properties where I/I rehabilitation was technically feasible and cost-effective were included.

Project schedule

In 2010, property owners that were eligible and willing to participate in the sewer rehabilitation project were asked to sign a Right of Entry (ROE) agreement for construction. To limit the amount of excavation in neighborhoods, King County used less invasive trenchless rehabilitation techniques whenever possible.

  • Public meetings were held in early 2010 and 2011 to provide information about the project and answer questions.
  • King County conducted an environmental review of the project under the State Environmental Policy Act (SEPA) in Summer 2010.
  • Construction began in April 2011 and was completed in June 2012.

Map: Final Planned Comprehensive Properties for Skyway I/I Reduction Project - click for larger versionSkyway project area – Final Planned Comprehensive Properties  , March 2011

Construction highlights

Construction began in mid-April 2011 and was completed in June 2012.

Construction included replacement of approximately 21,400 ft of sewer main in the right-of-way, replacement of 99 manholes and replacement of side sewers on 298 properties. During construction, King County maintained a 24-hour project hotline and worked closely with the project construction team to address noise, dust and other community concerns.

King County used a less invasive technique to replace side sewers called pipe bursting. Here is how it works:

  • Excavation pits are dug at connection with sewer main and near house
  • Possible excavation of additional pits if there are multiple bends across the yard
  • Side sewer is replaced using pipe bursting technique. Existing pipe is burst apart by a bursting head and new pipe is pulled into place behind the bursting head.
  • Yard improvements disturbed by pipe bursting are repaired, including landscaping and patching of driveways and sidewalks
  • Installation of cleanout capped at grade
  • Photo log of original improvements required to verify restoration

Here is how the sewer main replacement process works:

  • Access pits are dug and covered with steel plates
  • After side sewers are replaced sewer main is replaced and laterals reconnected
  • New manholes are installed
  • Access pits are filled and areas are restored


You can download and view documents (PDF files) using a PDF Reader.

PitAtHouse_250 Example of excavation pit dug near house

PipeBursting_250Example of pipe bursting

ReplacementProcess_250Replacement process. For more information, view the preconstruction meeting presentation, March 30, 2011 (1.4 MB,  ).

Now posted: Skyway Infiltration and Inflow Reduction Demonstration Project Evaluation Report, March 2014 (Link redirects you to the Regional Infiltration and Inflow Control Program.)

This report summarizes the history of the Skyway Infiltration and Inflow (I/I) Reduction Project, the work performed, follow-up investigations, and findings about the project’s effectiveness in reducing I/I. It describes lessons learned from the project that can be applied to similar work in the future and outlines additional steps needed in order to use the project results for future decision-making.