The Gere HPP was conceived in previous design phases as a traditional high-head scheme with a nearly horizontal, approx. 2 km long low-pressure headrace and an 800 m long buried penstock. The low-pressure headrace was designed as a tunnel with an exposed pressure line inside, as the tunnel was also intended to be used as access to the headworks during winter.
During the offer preparation for engineering services including tender, detail design, site supervision and commissioning, Lombardi as a member of the JV IGSL proposed a scheme modification with a 2.6 km long inclined tunnel from the powerhouse area up to the desander facilities and the Tirolean intake. The winter access function of the tunnel was maintained as in the original layout. The project was awarded to IGSL adopting this layout optimization.
Drill-and-blast underground excavation is carried out from the d/s portal only. The tunnel portal is located close to the powerhouse, easily accessible and just approx. 300 m from the designated dumping area. After excavation completion, the GRP-line is installed in the tunnel from u/s to d/s. It was possible to optimize and dramatically simplify site logistics compared to the original project layout: the two cableways for conveyance of the excavation material to the dumping area and for penstock installation are no more needed and the project environmental impact are further reduced.
Lombardi has been in charge of all conceptual and design project issues whereas our JV partner is responsible for project management and site supervision.