Interceptor Sewer

Published: | Updated: September 21, 2020;

Definition - What does Interceptor Sewer mean?

An interceptor sewer is a major sewer line that receives flows from trunk sewer lines, and sometimes, stormwater drainage systems. This combined flow is then directed to a wastewater treatment facility or another interceptor.

In a typical sewer system, sewage first flows from domestic buildings via relatively small pipelines known as laterals. These pipelines take wastewater from residential/private properties and direct it to government-owned local sewer lines that run under streets and other rights-of-way.

Local sewer lines then discharge the wastewater via gravity to trunk sewers located at various manhole locations. Interceptor sewers then take the contents of the trunk sewers, directing them to an appropriate treatment facility.

Since interceptor sewers take collective flows from laterals, local lines, and trunk sewers, they are among the largest pipes in a sewer network. Some interceptor sewer lines can be over eight feet in diameter and convey millions of gallons of wastewater per day.

Interceptor sewers are also known as interceptors.

Trenchlesspedia explains Interceptor Sewer

Interceptor sewer lines form an essential part of an area’s sewer network. They are typically the last conveying system for transporting waste to treatment facilities. As such, they need to be appropriately sized to accommodate flows from all other combined systems.

Interceptor sewers are usually found in larger cities with vast sewer systems. Typically, sewer networks consist of laterals, local or municipal sewer lines, and trunk sewers, each with increasing diameter. In these conventional systems, the regional trunk sewer acts as the final route to the wastewater treatment plant.

Interceptors, however, take this process a step further. These pipes ‘intercept’ the flow from several trunk lines, taking the combined product to the treatment plant.

How Are Interceptor Lines Installed?

Because they are the last element in a sewer system before the treatment facility, these pipes can be relatively large. As such, installing these pipes in developed areas using conventional open-trench methods can be challenging. The amount of excavation needed to accommodate interceptor pipes can result in significant disruptions and can also be costly. Trenchless methods, such as horizontal directional drilling (HDD) and pipe jacking, are, therefore, better suited for installing this type of infrastructure.

Are There Any Downsides To Having an Interceptor Sewer?

Since interceptor sewers carry a significant amount of wastewater, they need to be properly maintained to prevent failures, which can have devastating consequences. In 2016, the collapse of an interceptor sewer line in Macomb County, Michigan, resulted in a 250-ft long sinkhole and prompted the evacuation of 22 homes. The cost to repair the pipe was estimated to be $US 75 million.

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