Regional Infiltration and Inflow Control Program

Out in the Field - Finding and Fixing I/I

How do you find I/I?

I/I is a result of groundwater or stormwater that flows into the sanitary sewer system due to leaky sewer lines or manholes or from situations where stormwater can flow into the sanitary sewer system through direct connections, such as catch basins or roof drain connections. While there are two general approaches to finding and dealing with I/I, there are a variety of methods to determine if and where the problems are located.

Proactive Detection - Sewer System Evaluation Surveys (SSES)

Several sewer system tests can be used to examine the condition of individual sewers and identify I/I sources. These proactive detection tests are called sewer system evaluation surveys. A few of these tests include:

	Smoke Testing
	Dye Testing
	TV Inspection
	Flow Monitoring
	Rainfall Monitoring

Passive Detection

Finding I/I through passive detection methods really is a process of observing and noting where sewer flow problems occur. A prime indicator of I/I problems can be identifying where sewage flow backs up in the sewer system, resulting in environmental or public health concerns. Such backups can occur at sewage treatment facilities or in homes or businesses through drains, toilets or sinks, because a surcharge occurs in the sanitary sewer line. A surcharge is where sewage flows full in a sewage pipe and creates a pressure condition inside the pipe. This situation can force water back upstream, including up sewer lines and out openings in homes and businesses. Sewage flows can also back up and fill manholes to overflowing, resulting in untreated sewage flows being released to the environment causing potential environmental and public health concerns. The I/I Control Program is intended to reduce the incidence of this occurring.

» Fixing 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: Jan. 15, 2008

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