The Machupicchu hydroelectric scheme of EGEMSA (Electricity Generating Company Machupicchu SA) is considered the most important plant of Peruvian heritage. It is located close to the Inca ruins, in the province of Urubamba, in Cusco and uses the water of the Vilcanota River. The expansion of the HPP (Phase II) with an additional 100 MW to reach a total capacity of 190 MW approx is currently ongoing. Main characteristics of the HPP (Phase I): - Conventional Intake; - 4 desander chambers (Q = 30 m³/s); - Headrace tunnel (L=3.3 km S=16-27 m² free surface); - Conventional forebay; - Steel Penstock (D=2.9 to 2.1 m); - Cavern powerhouse equipped with 3 Pelton units P=30 MW each. Main characteristics of the HPP (Phase II): - Conventional intake (close to intake of Phase I); - 4 desander chambers (Q = 30 m³/s); - Headrace tunnel (L=3.3 km S=16-27 m² free surface, the same of Phase I); - Conventional forebay (close to the one of Phase I); - Steel penstock D=2.8 (into the rock mass); - Cavern powerhouse equipped with 1 Francis unit P=100 MW. The tunnel was excavated by drill and blast. The invert as well as the side walls were lowered and lined with concrete. Lombardi was asked to carry out a complementary technical evaluation of the adduction system capacity, including the works of new desanders and forebays in order to define the maximum hydraulic capacity of the tunnel taking into account the restricted boundary conditions.