The Gleno Dam was a multiple-arch dam

Arch dam

An arch dam is a type of dam that is curved and commonly built with concrete. The arch dam is a structure that is designed to curve upstream so that the force of the water against it, known as hydrostatic pressure, presses against the arch, compressing and strengthening the structure as it pushes...

 on the Gleno River in the Valle di Scalve in the northern Province of Bergamo

Province of Bergamo

The Province of Bergamo is a province in the Lombardy region of Italy. It has a population of 1,098,740 , an area of 2,722.86 square km, and contains 244 comuni...

, Italy

Italy

Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. The dam was constructed between 1916 and 1923 with the purpose of producing hydroelectric power. A portion of the dam failed and burst 40 days after its reservoir was full, on December 1, 1923, killing at least 356 people.

Background and construction

The dam was proposed and constructed by the Vigano family. A request to construct the dam was submitted in 1907 and initial construction began in 1916. In 1920, construction began on the dam's foundation and in September of that year, local officials were warned that contractors were not using proper cement mortar. In 1921, because of funding, the project design was changed from a gravity dam to a multiple-arch type. The design was approved and the multiple arch dam would be constructed on top of the gravity dam foundation. In January 1923, the dam was 80% complete and by October 22, it was fully complete along with its reservoir full after heavy rains. The dam's power plant had an installed capacity of 3,728 kW (3.7 MW).

Failure

At 6:30 on the morning of December 1, 1923, a buttress on the dam cracked and subsequently failed. Within minutes, an estimated 4500000 cubic metre of water gushed from the reservoir at an elevation around 1535 m (5,036 ft) above sea level to the valley below. The village of Bueggio was flooded first, followed by a partial flooding of Dezzo

Dezzo

Dezzois a river of Lombardy and is the main river of Val di Scalve. Dezzo starts its course in the mountain of Schilpario at 1800m then continues to the river Oglio. Dezzo's mouth is close to the village of Boario Terme....

 part of the municipality of Azzone

Azzone

Azzone is a comune in the Province of Bergamo in the Italian region of Lombardy, located about 90 km northeast of Milan and about 45 km northeast of Bergamo. As of 31 December 2004, it had a population of 458 and an area of 16.8 km².Azzone borders the following municipalities:...

 and complete flooding of Dezzo a frazione

Frazione

A frazione , in Italy, is the name given in administrative law to a type of territorial subdivision of a comune; for other administrative divisions, see municipio, circoscrizione, quartiere...

 of Colere

Colere

Colere is a comune in the Province of Bergamo in the Italian region of Lombardy, located about 90 km northeast of Milan and about 45 km northeast of Bergamo...

 and Corna di Darfo. The flood waters were stopped when they reached Lake Iseo

Lake Iseo

Lake Iseo or Lago d'Iseo or Sebino is the fourth largest lake in Lombardy, Italy, fed by the Oglio river.It is in the north of the country in the Val Camonica area, near the cities of Brescia and Bergamo. The lake is almost equally divided between the Provinces of Bergamo and Brescia...

 which lies at an elevation of 186 m (610 ft) above sea level. At least 356 people were killed in the disaster.

Cause of failure

The dam was originally permitted as a gravity dam with a slight curviture, but was changed to a multiple arch dam by the client to save money. The permit was not revised for this change until after the dam was completed. The failure of the multiple arch dam was attributed to many aspects of its construction, ultimately poor workmanship. The concrete in the arches was of a poor quality and it was reinforced with anti-grenade scrap netting that had been used during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. There were also indications that the dam was poorly joined with its foundation. Additionally, the concrete was believed to not be completely dry when the reservoir was filling. Reportedly, workers who complained about the construction techniques were fired. Today a memorial exists in the failed gap along with a much smaller dam and reservoir within the old reservoir zone.

The dam's failure was influential in the development of Italian dam design and risk assessment. As a result of this failure, the construction of new multiple arch dams have become disfavored.

External links

• Gleno Dam History at Scalve.it (Italian and English)