An approach for the selection of renewal technologies to remedy structural problems in gravity sewers

Sewer pipelines are renewed by replacement or rehabilitation. Replacement options include replacement with same size diameter or with larger size diameter. Rehabilitation options include non-structural, semi structural or full structural rehabilitation. Several renewal technologies available in the market are capable of providing different replacement or rehabilitation options. The process to select renewal technologies generally proceeds in three steps. In the first step, the problems within the sewer are identified. Rehabilitation or replacement option/s capable of rectifying the problem are proposed (e.g. full structural rehabilitation or non structural rehabilitation) in the second step. Finally, technologies capable of addressing the problem are listed and evaluated against selection criteria. Technologies are selected based on their performance against the selection criteria. The main selection criteria used in the evaluation involve an assessment or costs and benefits. Costs are calculated in term of direct and indirect cost. Benefits are calculated in terms of service life prolongation.;This study proposes a new methodology to select renewal technologies to remedy structural problems in sewers. The proposed methodology improves the current selection process by considering the expected future structural deficiencies in the sewer. the condition of the sewer prior to renewal. the rehabilitation or replacement option used in renewal (e.g. full structural rehabilitation or non structural rehabilitation) and expected traffic disruption cost during renewal work. Selected technologies are then evaluated based on their overall costs and benefits. The proposed methodology was implemented in a software system to facilitate its practical application.;In the literature, the flow of the selection process typically provides a logical sequence, however this paper identities several gaps which were identified in each step of the commonly used selection process. For example, the current problem definition does not provide an indicator of future structural deficiencies in the sewer and the main cost/benefit evaluation criteria do not consider the current condition of the sewer or the rehabilitation or replacement option used in the renewal. In addition, the costs calculated do not consider all the cost borne by the public due to traffic disruption during renewal.