The Mengkubau dam was built to supply water to the Treatment Works, which supply the Brunei Muara area. The impounding reservoir is created by a 29 m high concrete faced rockfill dam. It was completed in 1999 and first filled later that year. The existing raw water pumping station was designed for 30 Mld capacity.
The raising of Mengkubau Dam involves heightening the existing dam by 3.7m, raising of 2 draw-off towers, extension of draw-off culvert and modification of spillway. A new Labyrinth spillway is constructed on top of the existing Ogee weir in order to lower the flood rise level.