Regional Infiltration and Inflow Control Program

Program history

The King County Regional Infiltration and Inflow (I/I) Control Program was created in 1999 as part of the Regional Wastewater Services Plan (RWSP) to explore the feasibility of I/I control.

In response to the RWSP I/I Control Program policies, WTD staff, working in a consensus-based approach with local sewer agencies, conducted a comprehensive 6-year, $41 million I/I control study. The study began in 2000 and culminated with the Executive's recommendation for a regional I/I control program. The following work was completed as part of this study:

• Defined current levels of I/I for each local agency tributary to the regional system through extensive flow monitoring and modeling program (2001-2002).
• Selected and constructed 10 pilot projects in 12 local agency jurisdictions to demonstrate the effectiveness of collection system rehabilitation projects and to test various technologies and gain cost information (2003-2004).
• Developed final draft model standards, procedures, policies, and guidelines for use by local agencies to reduce I/I in their systems. These will remain draft pending completion of the
  recommended initial projects (October 2004).
• Completed a thorough benefit-cost analysis to determine the cost-effectiveness of I/I reduction (November 2005).
• Developed a long-term regional I/I control plan, approved by the King County Council (May 2006).

Next steps

Beginning in 2007, King County began working with the local sewer agencies to conduct an I/I reduction feasibility analysis in order to select and implement 2-3 initial I/I reduction projects.

More information

• For questions about the I/I Control Program Web site, please contact Maryann Petrocelli at 206-263-7321 or maryann.petrocelli@kingcounty.gov.
• Archived news releases.

» Resource Center and Document Library

Department of Natural Resources and Parks
Wastewater Treatment Division
201 S. Jackson St.
Seattle, WA 98104-3855
Fax: 206-684-1278

Updated: July 3, 2008

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