Labyrinth Weir Design
Spillways & Energy Dissipaters
The Theun Hinboun Expansion Project (THXP) Huoai Phadang Retaining Dike will collect, store and release any potential seepage from the Nam Gnouang (NG) reservoir that may seep through the limestone formation along the high water line on the southern rim of the NG reservoir. Figures below show the locations of the NG Dam, the Retaining Dike and the maximum NG reservoir pool level. Depending on the amount of seepage through the limestone ridge, the Nam Gnouang Saddle Dam (NGSD) will maintain the water surface behind the Saddle Dam at levels equal to the NG reservoir level to prevent any loss of water from the reservoir.
DSI was contracted by the dam design engineers (Geotech) to provide the hydrologic and hydraulic design for the Saddle Dam. A range of design storms were determined and the spillway crest and capacity was set using the PMP. A Labyrinth Weir was used for the spillway to minimize the spillway width. The low level outlet (LLO) was designed to act in stages during the leakage assessment and subsequent dam construction.