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Table 4

Levels of severities (Japan Sewage Works Association 2014)

Levels Sewer conditions
ABC
Whole length assessment Corrosion of pipes Steel reinforcement visible Aggregate visible Surface roughness 
Deformed in vertical direction (Inner diameter) less than 700 mm 100 % or greater of inner diameter 50 % or greater of inner diameter less than 50 % of inner diameter 
(Inner diameter) between 700 mm and 1,650 mm 50 % or greater of inner diameter 25 % or greater of inner diameter less than 25 % of inner diameter 
(Inner diameter) between 1,650 mm and 3,000 mm 25 % or greater of inner diameter 12.5 % or greater of inner diameter less than 12.5 % of inner diameter 
Levels Sewer conditions
abc
Local (pipe-wise) assessment Breakage/longitudinal crack Reinforced concrete pipe, etc. Collapsed Longitudinal crack 2 mm or greater in width Longitudinal crack less than 2 mm in width 
Longitudinal crack 5 mm or greater in width 
Clay pipe Collapsed Longitudinal crack less than 50 % of pipe length – 
Longitudinal crack 50 % or greater of pipe length 
Circumferential crack Reinforced concrete pipe (RC) etc. Circumferential crack 5 mm or greater in width Circumferential crack 2 mm or greater in width Circumferential crack less than 2 mm in width 
Vitrified clay pipe (VC) Circumferential crack two-thirds or greater of the circumferential length Circumferential crack less than two-thirds of circumferential length – 
Displaced joints Extruded joints Reinforced concrete pipe etc.: 70 mm or greater Reinforced concrete pipe etc.: less than 70 mm 
Vitrified clay pipe: 50 mm and over Vitrified clay pipe: less than 50 mm 
Infiltration Gushing Running Seeping 
Extrusion of lateral 50 % or greater of inner diameter 10 % or greater of inner diameter Less than 10 % of inner diameter 
Attached deposit, grease Blockage of 50 % or greater Blockage of less than 50 % of inner diameter – 
Roots intrusion Blockage of 50 % or greater Blockage of less than 50 % of inner diameter – 
Attached deposit, mortar Blockage of 30 % or greater Blockage of 10 % or greater Blockage of less than 10 % 
Levels Sewer conditions
ABC
Whole length assessment Corrosion of pipes Steel reinforcement visible Aggregate visible Surface roughness 
Deformed in vertical direction (Inner diameter) less than 700 mm 100 % or greater of inner diameter 50 % or greater of inner diameter less than 50 % of inner diameter 
(Inner diameter) between 700 mm and 1,650 mm 50 % or greater of inner diameter 25 % or greater of inner diameter less than 25 % of inner diameter 
(Inner diameter) between 1,650 mm and 3,000 mm 25 % or greater of inner diameter 12.5 % or greater of inner diameter less than 12.5 % of inner diameter 
Levels Sewer conditions
abc
Local (pipe-wise) assessment Breakage/longitudinal crack Reinforced concrete pipe, etc. Collapsed Longitudinal crack 2 mm or greater in width Longitudinal crack less than 2 mm in width 
Longitudinal crack 5 mm or greater in width 
Clay pipe Collapsed Longitudinal crack less than 50 % of pipe length – 
Longitudinal crack 50 % or greater of pipe length 
Circumferential crack Reinforced concrete pipe (RC) etc. Circumferential crack 5 mm or greater in width Circumferential crack 2 mm or greater in width Circumferential crack less than 2 mm in width 
Vitrified clay pipe (VC) Circumferential crack two-thirds or greater of the circumferential length Circumferential crack less than two-thirds of circumferential length – 
Displaced joints Extruded joints Reinforced concrete pipe etc.: 70 mm or greater Reinforced concrete pipe etc.: less than 70 mm 
Vitrified clay pipe: 50 mm and over Vitrified clay pipe: less than 50 mm 
Infiltration Gushing Running Seeping 
Extrusion of lateral 50 % or greater of inner diameter 10 % or greater of inner diameter Less than 10 % of inner diameter 
Attached deposit, grease Blockage of 50 % or greater Blockage of less than 50 % of inner diameter – 
Roots intrusion Blockage of 50 % or greater Blockage of less than 50 % of inner diameter – 
Attached deposit, mortar Blockage of 30 % or greater Blockage of 10 % or greater Blockage of less than 10 % 
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