This is a project of the installed capacity of 12.0MW with a gross head of 462m and of design flow rate of 4.5m3/s. The project uses the waters of the Siti river originated at the mount Elgon in eastern Uganda flowing down to lake Albert in south western region of the country. The project is located within the lower slopes of the mount Elgon at the elevations between 1874.0amsl at weir and 1412.0amsl at the powerhouse. The section of the river valley between weir and the powerhouse is a deep valley with very steep embankments where the project corridor had to run along within. The project’s conceptual layout that we developed featured with the following component.
- Diversion weir and water intake with bed material elimination trap.
- Head race part of water conveyance channel, which is rectangular and of reinforced concrete.
- Silt / sand settling trap including flushing arrangements. (De-sand tank)
- A GRP siphon pipe to cross a moderately deep valley.
- The forebay tank facilitating the spill function, trash removal arrangement (trash rack) and the deep chamber intake for the high pressure penstock pipe.
- High pressure, single conduit, steel penstock pipe.
- Powerhouse building and switch yard.
Over and above the general design tasks, the most challenging part was the design of the support system of the high pressure steel penstock to have an alignment that meet hydraulic and structural requirements owing to the poor geological conditions of the ground within a considerable length of the penstock. Final design consisted of a series of reinforced concrete cantilever supports anchored on to steeply sloping rock embankment with the pipe alignment running along with the rock with pipe bends designed to required hydraulic curves. There was also the risk of falling rocks from the steep rock embankment uphill of the pipe where the surface exhibits vertical and horizontal joints closer apart forming hanging rock blocks of considerable size. The pipe supported on cantilever supports were buried to form a strata to absorb shock from falling rocks..
Developer: Elgon Hydro Siti (Pvt) Ltd, Plot 02, Naguru Summit View, Kampala, Uganda
Scope: Geotechnical, hydraulic and structural design
Capacity: 16.5 MW
Project Status: Completed in 2020