The Pego do Altar Dam Railway

Agricultural hydraulic engineering and the Sado Valley

In 1930 the Junta Autónoma das Obras de Hidráulica Agrícola was established to study ways of irrigating some 400,000 hectares of Portuguese territory. Five years later, an initial programme provided for 16 irrigation schemes. In 1937 a more ambitious plan provided for 20 dams, capable of irrigating 106,000 hectares and generating electricity.

Among these schemes were the Lower Sado Valley Works. The programme included the Vale do Gaio Dam on the River Xarrama and the Pego do Altar Dam on the Santa Catarina stream. Estimated investment exceeded 116,000 contos and was intended to provide irrigation for more than 8,000 hectares as well as electricity generation.

The Pego do Altar Dam

The irrigation scheme for the area covered by the Santa Catarina stream basin and the marginal strip between Alcácer do Sal and the Marateca stream pre-dated the creation of the Junta. The new body was nevertheless responsible for developing the studies that led to the preliminary reservoir scheme, presented in 1933 by civil engineer Afonso Zuzarte de Mendonça.

The study envisaged a rockfill dam[1], built with porphyry[2] available in the region. Outcrops at Biscainha, Romeiras, Gafanhões and Moinho da Ordem were assessed.

The engineer also considered an alternative: if the proposed Iberian broad-gauge line between Casa Branca and Alcácer do Sal were completed in time, only a branch of approximately four kilometres to the construction site would be required. This would reduce the cost of carrying stone and allow other materials to be delivered directly to the works.

The final scheme was submitted in 1935 and approved on 10 January 1936 by Minister Duarte Pacheco, who ordered the immediate opening of the tender. The contract was awarded on 20 August 1936 to Manuel Xavier Ramalho Rosa, who subsequently transferred it to the Sociedade Portuguesa de Empreitadas, established in May 1937.

Studies carried out in the Moinho da Ordem area meanwhile showed that the available stone was neither of the required quality nor present in sufficient quantity. A new source was therefore selected: the Corte Pereiro quarry.

Construction proceeded with difficulty. The contract with Sociedade Portuguesa de Empreitadas was terminated in November 1940 and Bastian & Costa took over. Despite technical and administrative problems, that firm completed the dam, spillway, water intake, the Gachinha–Palma–Marateca canal tunnel and the associated canals.

The Pego do Altar Dam was inaugurated on 30 May 1949. At 63 metres high and 192 metres long, with a reservoir capable of storing about 94 million cubic metres of water, it was then presented as the largest rockfill dam in Europe.

The scheme included a hydroelectric power station equipped with a turbine rated at 2,720 CV (metric horsepower), together with an irrigation network almost 39 kilometres long. The final cost of the Lower Sado Valley Works reached about 270,000 contos, far above the 116,000 originally estimated.

The railway

The industrial railway was essential to the success of the project. Over almost a decade it carried some 648,672 tonnes of stone for the crest and body of the dam.

Approximately ten kilometres long, the railway began near the village of Pego do Altar, where the workshops for maintaining the locomotives and other rolling stock were located. It then ran northwards, skirted Monte das Mourarias and approached Santa Susana.

From there the line followed the right bank of the Ribeira de Remourinho for several kilometres. After crossing a tributary, it curved towards the Corte Pereiro quarry.

Locomotives, wagons and many questions

Research into small industrial railways is almost invariably hampered by a shortage of documentation. In the case of Pego do Altar, the chronology, the origin of the locomotives and the fate of the equipment after closure remain partly uncertain.

The railway appears to have been built in 1939 or 1940, as it is already mentioned in a 1940 scheme to alter the stream diversion gallery. After the dam was completed, the railway was dismantled.

Roberto Joaquim Pombo Consciência, who as a child witnessed the construction works and the inauguration, recalled that the metal bridge deck remained stored for many years in the former railway workshops, beside the restaurant later run by his family.

According to the same testimony, the locomotives were said to have come from Morocco. This has never been confirmed. The total number of engines is likewise uncertain — although there were at least two — as is their fate after 1949.

The photographs support only a few cautious conclusions. The locomotives appear to have been tramway-type steam engines, probably of standard gauge. The wagon fleet included low-sided platform wagons and twin-hopper wagons. A separate Decauville system also operated around the construction site, using small hand-propelled tip wagons.

A surviving railway landscape that can still be explored

Although the track has disappeared, the route remains largely traceable. Some sections are used as public tracks, embankments survive, the tunnels remain accessible and the bridge piers still stand.

The Pego do Altar Reservoir Management Plan, approved in 2005, sought to strengthen the area’s tourism potential. The document itself allows for the creation of walking, equestrian and cycling routes using existing tracks and paths.

What can still be seen

Decades after the track was lifted, the remains are surprisingly well preserved. The former trackbed is intact in several places, considerable ballast survives, the bridge piers appear to await a new deck, and at least one of the tunnels still seems structurally sound.

Restoring the route as a greenway could create a new visitor attraction for the municipality of Alcácer do Sal while also giving greater prominence to the history of the dam and the railway that made its construction possible.

Text adapted and revised from the original article by Ricardo Barradas, published in O Foguete, No. 24, in 2010.