The contract value is US$282M, 95% as Astaldi share, the company said in a statement.
The 106MW Chacayes project will be built in the Cachapoal river catchment and calls for excavation of more than 6km of tunnels. The construction work is to be completed by 2011.
Astaldi added that it had also entered into an agreement with the Australian power company to develop further hydro power resources in the Cachapoal area. Proposed projects include Nido de Aguila and Las Lenas, which would have combined installed capacity of 282MW.
The other planned projects in the scheme have a total value of US$600M, said Astaldi, which has an exclusivity agreement to negotiate other contracts next year.