Design and construction of the north ward sewer system Kisoro municipality, Kisoro district.

Abstract

This report documents the work done by the author during the planning, designing and construction supervision of the Kisoro North Ward Sewer System Under National and Sewerage Corporation in Kisoro District, Western Uganda. The project consists of design and construction of Northward sewer system. The construction of the project started in March 2017 and was completed in January 2018. The North Ward Sewer System Project was developed with the aim of improving the health and living conditions of the North ward Community. Entailed in the Report is a detailed presentation of the water demand and waste water projections, the hydraulic analysis and pipeline sizing, and the choice of materials, among others, adopted in designing the project, together with the project management approaches used to ensure the effective execution of the project. The sewer system was designed as an extension to the Kisoro Sewerage system. An assessment of Seseme Waste water treatment plant revealed that the Plant had capacity of treating 70m3 /day of waste water of which the daily influent was about 20m3 /day, and could as such accommodate surplus discharge of up to 10.0m3 /day. This was found to be sufficient for Seseme Treatment Plant design waste water flow computed at 22m3 /day. As part of the design process, a socio-economic survey was conducted in the project area, on the basis of which the design parameters were refined. The current population was established as 3,100 using the UBOS population figures, giving a design population of 4,800 over the 15year design horizon. This translated into a design daily wastewater flow of 22m3 /day. A hydraulic analysis of the sewer mains was carried out using the Gauckler-Manning equations and PC based simplified Sewer design software respectively, on the basis of which the pipes were sized, taking into consideration the investment costs, system operation and maintenance costs, and hydraulic and topographical considerations, among others. From the hydraulic analysis, a Sewer main of 2.0km of DN 150 PN6 uPVC pipe was adopted. The water and sewer mains intensification lines/service connections were on the other hand designed to serve all the villages within the project area, with the targeted population about 50meters for water and 60meters for sewer on average from the designed service lines in order to reduce the consumer connection costs. As part of the Project, an Environmental and Social Impact Assessment (ESIA) Project Brief was prepared, revealing that the potential environmental impacts were minimal and the mitigation measures provided therein were sufficient to preserve the local environment. Further, a cost estimate for the Project based on the system components was prepared, resulting into an engineering estimate of 275 Million Uganda shillings. Upon completion of the detailed designs, the works were advertised following the PPDA procurement procedure and works done at a total contract sum of UGX 268,435,250. The construction contracts commenced in March 2017 and the works were substantially completed in January 2018. The Total Project cost at completion was UGX 276,433,789 which was within the engineering Estimate mentioned above.