CHAPTER 1.The Beginning

Designs of the main dam (L'Energia Elettrica Fasc. XII Vol.2 1925)

The story of the disaster of Molare begins at the end of 1800 and takes place in South Piedmont, near Liguria (click here to see the map), in the Orba Valley . The Orba torrent has its source in the Ligurian Alps (Beigua and Rama Mounts), positioned behind Genoa and forming the watershed sepataring the Ligurian Sea and the Adriatic Sea . After a tortuous course northwards, the Orba torrent flows into the Bormida River, just north of Alessandria . Molare village is on the left bank of the Orba torrent and its origins go back to the Roman times. Its territories extend entirely inside the Orba Valley , from the small cluster of Olbicella, on the border of Liguria, to the little town of Ovada .

Cross section Main Dam

Cross section Main Dam

At the end of the XIXth century, a Genoese Society, called “Forze Idrauliche della Liguria”, in the person of Mr. Luigi Zunini, an Engineer, proposed a set of feasibility projects in order to build a large barrage in Ortiglieto, a place 6 km far up from Molare .These projects aimed at using water exclusively for hydropotable purposes in favour of Genoa, which at that time was growing rapidly.
Both Molare and Ovada Municipalities, located downstream the hypothetical dam, opposed strongly to this plan, appointing a Vigilance Commitee, too. At this point, Mr. Zunini submitted some new further projects, taking into account both the hydroelectric production for the “disobedient” Municipalities and as well the potable use in favour of Liguria.

Realization of the siphons

This embarassing situation went on for some years till 1906, when Mr. Zunini succeeded in obtaining from the Regia Prefettura of Alessandria, a first concession to exploit the torrent water, being this now a good reason for the electricity requirements of the railway line Ovada-Acqui Terme and not only for the Ligurian hydropotable needs. Later, this agreement was declared anyway of no effect due to some unfulfilments of Mr. Zunini's Company. Actually, the Italian Government looked unfavourably on Mr. Zunini, since he was frequently working in collaboration with some German hostile Companies. In 1916, the Officine Elettriche Genovesi (O.E.G) were granted the concession and previous agreements in favour of Molare and Ovada Municipalities were declared invalid. Same year, a new concession demand was submitted, relating to a fresh project, involving a sensible increase of the storage capacity (14 met more), keeping anyway unchanged in the main both location and positioning of the original project elements of Mr. Zunini.

The Main Dam (L'Energia Elettrica Fasc. XII Vol.2 1925)

The “new project” was made by the engineer Mr. Gianfranceschi. It is easy to suppose that during the first period, working was strongly hindered by money difficulties and as well by hard finding of skilled labour and raw materials, due to the outbreak of the First World War. Anyway, since 1922 and in the following two years, working operations went on readily, thanks also to a new management of the O.E.G.

The Orba torrent was barred in Ortiglieto through an arch-gravity dam (200 mt about radius), 47 mt. height (34 mt. were initially designed), equipped with 4 different outflow systems (12 siphons, an overspill surface type overflow, a bottom outlet and a half-deep discharger fitting a bell shaped valve), enabling to discarge 855 cubic meters/sec. This wide hydraulic work was completed in 1925 and named Main Dam of Bric Zerbino.

CHAPTER 2.The Lake and the Secondary Dam