Draining the Lake

On the 20 October 1928 the Head of Government, accompanied by the Undersecretary of the Interior and the ministers of Education and Public Works started the pumps for the draining of the lake after having carried out a rapid examination of the work completed up to that point.
The water sucked out of the lake was carried in four large pipes which in turn emptied into a huge header tank situated at the entrance of the Roman conduit which cut through the hillside from the lake to the surrounding countryside. The four deafening gouts of water thus united in the header tank and then quickly passed into the conduit to emerge on the other side of the volcanic crater, to then pass down a purpose built canal down to the sea. The great enterprise had at last begun!

As related by Guido Ucelli in his book Le Navi di Nemi:-

"In the glory of the Roman sunset a fire seems to burn in Nemi, the tower of the Orsini, and even higher up still, in the burning sky, the trees of Monte Cavo blaze around the deserted altar of Giove Laziale: portentous vision that then, suddenly, is extinguished. The evening shadows invade the crater, the mirrorlike water becomes immediately grey and is ruffled by a light breeze: it seems that a spell is being broken; but the work that has been started is not interrupted; the humming of the rotating machinery continues apace, as does the rush of the water through the conduit in its race to the sea.

Even those who were not present had a sensation of an unrepeatable hour having passed. Much later, at the distance of several months, Ugo Ojetti while addressing the Head of Government publicly on the problems of art, cited the commencement of work on the draining of the lake as one of the events worthy of being remembered in the teaching of art.

The days pass slowly in wait: on the banks of the lake, along the path which leads from the Fishermen's House to the pumphouse, nothing changes. The lake seems immoveable: only the water gauge registers the immperceptible, continuous, drop in the water level. The regular and constant flow of the water spewed out by the pumps enlivens the ancient gallery, rushes through the dark earth of Ariccia and descends by slopes and waterfalls to the sea.

There are those who predict disastrous earthquakes as a result of the emptying of the lake!

On 16 October, just as the first tests were being carried out, a small harmless tremor took place, that some wanted to interpret as a warning: thus the order to keep in contact with the geophysical observatory at Rocca di Papa, but fortunately, after this false alarm no other phenomenon of this type was registered and the work could continue without obstruction."

The Prima Nave appears.

In the middle of February 1929, a second pumphouse was set up between the original one and the level of the lake which by this time had dropped by 4 metres.
On the 28 March 1929, as the level reached -5.52 metres from the original, the first parts of the ship appeared from the waters of the lake.
The event created great interest which reached the world press and the positive and scientific nature of the undertaking was affirmed against the troublesome polemics of those who continued to doubt even the existence of these antique curiosities.
The second pumphouse did not last long. Despite attempts to stabilise the terrain the platform at the second pumping station subsided and a plan which had already been prepared for a floating pumping station, now became indispensible. Two great pumps were mounted on a floating pontoon from the military engineers and connected to the rigid pipes on the shore by huge flexible tubes of armoured rubber. This plant was put into operation in the middle of May and this configuration which proved to be excellent, was retained, with necessary modifications, until the end of the operation. This is the setup as seen in the photograph below.

This photograph shows clearly how the pumping station kept up with the falling level of the water by extending the pipes leading down to the lakeside. This however had limits and after a certain point, instead of simply extending the pipes, a floating platform with pumps on it, was used as the water intake and eased the strain of the vertical lift of the water to the shoreside pumphouse.

The pumping operation thus had three distinct phases as can be seen in original plans.

Single pumphouse.
Second pumphouse added at mid point to the water level.
In the wake of subsidence of the terrain at the second pumphouse, institution of a floating pumping platform which remained in operation to the very end.

Here we see the floating pumping platform at a more advanced stage of the draining operation.