Closed Asturian coal shaft in the urban centre of El Entrego, the first vertical shaft sunk in the central Asturian coalfield, retaining its surviving headframe.
Pozu Entrego, located in the urban centre of El Entrego in the concejo of San Martín del Rey Aurelio, was the first vertical bituminous coal shaft profundised in the Central Coalfield of Asturias, with sinking works carried out between 1905 and 1909 by the company Nespral y Cía. A wooden headframe and simple winch served the shaft until 1926, when struts were added. In the 1940s an iron riveted-lattice headframe housing a modern steam-powered extraction engine was installed, later replaced by an electrical engine and, subsequently, by a new welded headframe fitted with one of the first Koepe winding pulleys in Asturias, supplied by GHH and Siemens.
A small washery was added from 1958. The shaft was integrated into Hunosa in 1969, operated until 1993, and was the last of the original Nespral shafts to cease production. The winding engine house was subsequently demolished.
A business centre for technology enterprises was installed at the site. The surviving headframe, standing 26 metres in height, remains at the urban site.
The origins of the Pozu Entrego lie in the mining enterprise of the Nespral family, who had been engaged in coal extraction in the area of San Martín del Rey Aurelio since at least the mid-nineteenth century. Vicente Fernández Nespral founded the family firm Nespral y Cía in 1897, which operated mountain mines — exploiting seams above valley level through horizontal galleries — in the Socavón de Bédavo and in other concessions, before committing to the larger investment of a vertical shaft.
Between 1905 and 1909 Nespral y Cía profundised the vertical shaft at the site in El Entrego. This made the Pozu Entrego the first vertical coal shaft in the Central Coalfield of Asturias, a distinction it holds in competition only with the Pozu Fondón in Langreo; some sources note that archival evidence for the Sorriego shaft's sinking pre-dates the Entrego, but the Entrego is conventionally held as the first to enter production. The shaft was sunk in the urban centre of the settlement, a siting that came to typify the intimate relationship between collieries and their communities in the Nalón valley.
Until 1926 the shaft was served by a wooden headframe and a simple winch. In that year struts were added to reinforce the headframe structure without replacing it. The headframe was properly replaced in the 1940s with an iron riveted-lattice frame, which accommodated a modern steam-powered extraction engine. A decade later the steam engine was replaced by an electric one. A subsequent modernisation replaced the headframe again with a new welded-steel structure fitted with one of the first Koepe winding pulleys in Asturias, supplied by the companies GHH and Siemens. From 1958 the mine was complemented by a small washery, which was modernised during the 1960s.
The Entrego shaft exploited the upper seams of the stratigraphic series of the Central Coalfield, with its galleries defining the Sinclinal de El Entrego, the largest geological structure in the basin. The shaft was the main extraction point of the Nespral group, with the Sorriego shaft serving as its auxiliary. By the 1950s the shaft was employing hundreds of miners.
In 1969 Nespral y Cía was integrated into Hunosa, and the Pozu Entrego continued operating under state ownership. It was the last of the original Nespral shafts to close: extraction ceased in February 1993, at which point the workforce was redeployed to other mines. After closure, the winding engine house was demolished. The shaft site was subsequently used for a business centre for technology enterprises. The surviving headframe, 26 metres tall, stands at the urban location. Hunosa undertook various activities at the installations after closure, though the transfer to local administrations remained pending as of the consulted sources.