Determination of capital costs for conventional sewerage systems (collection, transportation and treatment) in a developing country

Unit construction costs expressed as ranges of values are useful in most preliminary studies, in which detailed designs are not available in order to support specific cost estimates. This paper presents ranges of values for capital costs related to conventional sewerage systems in Brazil. The data were based on published references or information from consulting firms and sanitation companies and comprised budgets made at the design stage or after completion of the works. All cost data were converted to the common date of April 2010. The unit costs were expressed as: collection system (US$/m and US$/inhabitant), transportation system (US$/m and US$/inhabitant) and treatment system (US$/inhabitant). Total costs for the implementation of the overall sewerage system (collection, transportation and treatment) ranged from around US$170 to US$770/inhabitant, depending on pipe diameter and on pipe-laying conditions (percentage of rocks and pavement), as well as on the treatment process employed. In all cases, approximately 60% of the total capital costs were represented by the collection system. The influence of the transportation (interceptor) costs was also investigated and found to indicate that, for small populations, the construction costs associated with the interceptors may be larger than those linked to the treatment plants.