Regional Infiltration and Inflow Control Program

Why is I/I a problem?

Extra water in the sewer system is a problem because:

It takes up capacity in the sewer pipes and ends up at the regional wastewater treatment plants where it must be treated like sewage, resulting in higher treatment costs.
Requires new and larger wastewater facilities to convey and treat larger volumes of flow, resulting in higher capital expenditures.
I/I flows contribute to sewer system overflows into local homes and the region's waterways, negatively impacting public health and the environment.

Protecting the environment and decreasing wastewater treatment costs are the benefit of a regional I/I control program.

We estimate that inflow and infiltration makes up 75 percent of peak flows during winter, and much of this comes from private property.

» Finding Infiltration and Inflow (I/I)

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

Department of Natural Resources and Parks
Wastewater Treatment Division

Updated: July 3, 2008

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