Rehabilitation of Wastewater Collection and Water Distribution ...

• Manhole diameters are much larger than most sewer pipes and hence the thicknesses of
liners necessary to resist buckling against external groundwater pressures become
significant for the more expensive polymer materials.
• Most calculations for a structural lining do not take any account of bonding with the
manhole structure although, for a sealant coating, the bond is critical in terms of the
ability of the coating to resist seepage pressures.
3.4 Other Wastewater Issues
3.4.1 Inspection and Assessment. All rehabilitation and replacement works depend on some form
of inspection and consequent assessment of the sewer line. A closed-circuit television (CCTV) survey is
the predominant method in gravity sewers. However, there are many unmet needs of utilities in terms of
equipment and data acquisition when carrying out an inspection. The main issues raised in extensive
surveys are:
For gravity pipe systems:
• Improvements in current CCTV systems
• Higher resolution and better lighting
• Tractors better able to negotiate debris, grease, pipe separation, and corrosion
• Improved cleaning procedures undertaken during CCTV work
• Cameras for lateral inspections
• A combination of CCTV and sonar to inspect partially full or surcharged sewers
• A means to determine the remaining thickness of a corroded pipe, or determine the
severity of a defect by measurement of the width and depth of a crack or hole in the pipe
wall
• The ability to measure the depth of crown corrosion in a concrete pipe
• A method to measure sediment depth in large diameter pipes with heavy flow
• A means to locate sewer laterals accurately
• A means to quantify accurately deformations and out-of-roundness
• A means to quantify joint anomalies – steps and openings
• A means to map sewers that have deviations in line and level, and translate these directly
to Geographic Information System (GIS)
• A means to locate buried manholes
• A means to locate voids on the exterior of a pipe.
For pressure pipe systems:
• A means to determine the remaining thickness of a corroded pipe, or to determine other
defects such as cracks or pitting in the pipe wall
• A means to determine the magnitude of internal corrosion in a metallic pipe
• A means to locate leakage
• A means to do all of this with the main in service.
In many cases these capabilities already exist, whether within the sewer inspection industry or in others
from which they may be adapted, but the awareness of these capabilities remains patchy. In the force
main segment, it is seldom feasible to take a main out of service for inspection. No cost-effective
technologies exist for inspecting while in service – so, as a result, there is almost no inspection of force
mains undertaken.
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