Critical Sewers

Published: October 30, 2017 | Last updated: July 5, 2023

What Does Critical Sewers Mean?

Critical sewers refer to those sewers, which in the event of failure, will incur high costs in terms of repair and traffic delays. It also refers to those sewers that are considered to be strategically important. Critical sewers can be determined by assessing the consequences that failure of a sewer can cause in terms of cost of rehabilitation and economic loss caused by traffic disruption.

Trenchless rehabilitation methods, such as robot mounted closed-circuit television cameras (CCTV), can be used for the purpose of determining the condition of sewers.


Trenchlesspedia Explains Critical Sewers

Identifying critical sewers is important especially if they lie in zones of high traffic or environmentally sensitive areas. Critical sewers can be broadly classified into two categories.

Critical Sewers Category A Includes:

  • Brick sewers 2-meters or more deep or sewer pipes of other materials that are installed more than 6-meters deep in good ground or more than 5-meters deep in bad ground
  • Sewers with a diameter greater than 1,500-mm
  • Sewers under critical traffic flows exceeding 7,500 vehicles per day
  • Sewers under railways, rivers, motorways and canals

Critical Sewers Category B Includes:

  • Brick sewers up to 1-meter deep and sewer pipes of other material more than 3-meters deep
  • Sewers with diameter 600 to 1,500-mm
  • Sewers under critical traffic flows exceeding 5,000 vehicles
  • Sewers within high risk installation areas, industrial sites, or where failure of a critical sewer can lead to pollution of environmentally sensitive areas or water bodies

Old sewer systems that have deteriorated or crossed their expected life expectancy should be replaced, especially those falling under Category A or B mentioned above, to prevent potential harmful consequences resulting from failure, before failure occurs. Trenchless construction and rehabilitation methods have made it easier to install, replace or repair pipes easily, quickly, and without causing disruption to traffic flow.


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