The company said that the US$6.2M contract was won by its wholly-owned subsidiary Cavico Bridge and Tunnel Construction.
Works involve excavation of a 1000m long tunnel plus a 45m deep dismantling shaft. The new hydro power facilities will add 280MW (plants of 60MW and 220MW) to the existing Theun HinBoun facilities, and calls for construction of a 70m high RCC dam.
Italian firm Cooperativa Muratori e Cementisti-CMC di Ravenna awarded the contract to Cavico for the tunnelling works.
At the end of last year andritz was awarded the complete electro-mechanical equipment package for the expansion project, which is to be completed by 2012.
The new plant is being developed by the Government of Lao PDR, GMS Power of Thailand and Nordic Hydropower.
Owner and operator of the main plant is Theun HinBoun Power Co (THPC). The plant was inaugurated just over a decade ago.
Earlier this month, in Vietnam, Cavico was also awarded tunnelling work on the Song Giang 2 project.