Sewer condition assessment as a design input
Author(s): A. Goyns
Paper category: workshop
Book title: Performance of cement-based materials in aggressive aqueous environments – characterization, modelling, test methods and engineering aspects
Editor(s): Nele De Belie
Print ISBN: none
Publisher: RILEM Publications SARL
Pages: 108 - 115
Total Pages: 7
Abstract: As sewers are reliant on gradient to ensure their hydraulic effectiveness and efficiency they are placed below other services and sometimes at significant depths. If a sewer fails the remedial action required could have serious implications for the services placed above it at shallower depths. It is therefore essential that the choice of pipe material for a particular sewer is based on the actual conditions to which it will be subject. The theoretical models for choosing pipe properties and materials are based on assumptions about the sewer’s operating conditions.
The condition assessment of sewers starts by inspecting them with high resolution CCTV cameras and the capturing this visual data in digital format. The whole length of a sewer can then be studied by the investigator on a computer screen to determine whether there are any problems and if so their location and extent. This approach can also indicate the severity of any problems.
However establishing the severity of the problems requires access to the sewer to measure wall thicknesses. To determine the causes and propose remedial action where necessary needs further information on the effluent properties. By combing the information from these sources the investigator is able to obtain a very good understanding of condition inside the sewer in question.
By adjusting the theoretical analysis with the output from the condition assessment of the same sewer provides the designer with a very powerful tool that can be used for determining the remaining life of an existing sewer and its rehabilitation requirements, or for selecting the most appropriate pipe material for a new sewer operating under similar conditions to the one assessed.
There are many good reasons why concrete is the most frequently used pipe material for large diameter outfall sewers. However, very serious problems can arise due to concrete corrosion resulting from mechanisms, such as the biogenic formation of sulphuric acid on the pipe crown and acidic effluent from industrial waste. Investigation at design stage will identify these problems so that the necessary preventative measures taken by modifying or protecting the concrete pipes will ensure they are adequate for these operating conditions.
Online publication: 2008
Publication Type: full_text
Public price (Euros): 0.00
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