Pozu Barreo Mieres · Asturias · Spain

The origins of the Pozo Barredo lie in the Mina Mariana, a mountain coal mine on the western flank of the Polio massif operated by Fábrica de Mieres S.A. through a system of fifteen levels served by external inclined planes descending to the Barredo area at the base of the valley. The Socavón Barredo, the lowest-level adit of the Mariana system, marked the deepest point accessible by gallery, and from 1931 Fábrica de Mieres began considering the sinking of a vertical shaft to access reserves below this level. The designated site lay in the area known as Barredo or Barreo, on land already occupied by Fábrica de Mieres' mining plant.

Sinking of the shaft began in 1937, during the Spanish Civil War, though only 12 metres were driven that first year. The shaft reached 200 metres depth by 1940. The winding machinery — supplied by Siemens, Germany — came into service in September 1941.

A riveted-iron lattice headframe was erected in 1941, standing 25 metres high to the wheel axis with a further six metres of visor, for a total height of 31 metres. The headframe was constructed by Fábrica de Mieres using riveted lattice profiles — one of the last such structures built before welded construction superseded riveted work. A distinctive structural feature of the headframe is that its diagonal tornapuntas are taller than the vertical pies (feet), due to the engine house being located at a lower elevation than the external embarque level, requiring the pulleys to be placed at different heights.

The engine house is a building of 29 metres by 14 metres and 9 metres high, built in masonry and brick; it was originally the boiler house supplying steam to the turbines of an adjacent thermoelectric plant. The shaft served two cages, each capable of carrying four wagons on a single deck, operated by a double-drum disengageable extraction machine. In 1944 the Estación Central de Salvamento Minero del Caudal was established by companies including Fábrica de Mieres, building its operational base on Fábrica de Mieres land adjacent to the shaft; this rescue station was dissolved in 1970 and merged with the Nalón station to form the Agrupación de Salvamento Minero.

When HUNOSA was constituted in 1967, the Pozo Barredo was contributed to the new state company as part of the Fábrica de Mieres portfolio. In 1969, exploitation of the sector between the third level (20.7 metres above sea level) and the fourth level (50.0 metres below sea level) commenced, accessed by a 283-metre inclined plane at 15 per cent gradient. In 1981 the shaft was deepened from the third to the fifth level, reaching 355 metres total depth, with the fifth level at 135 metres below sea level.

During the Christmas period of 1991, thirty-six trade union leaders of the SOMA-UGT and the Sindicato Regional de la Minería de CC.OO., led by José Ángel Fernández Villa and Antonio González Hevia, occupied the shaft's fourth level in protest against HUNOSA's industrial restructuring plan. The occupation lasted from 23 December 1991 to 3 January 1992, receiving visits from the national secretaries general of the UGT and CC.OO., and ending with the emergence of the occupants to a mass demonstration in Mieres. The occupation of Barredo is considered a defining moment in the history of Asturian mining trade unionism.

Productive activity at the shaft ceased on 31 July 1995. From the same year, the interior of the shaft — particularly the fourth and fifth levels — began to be used for mine safety research by the Gobierno del Principado de Asturias, later extended to external facilities and to training and capacity-building activities. In 2001 the Fundación Barredo was established to manage these functions.

Drainage works continued until December 2007, owing to the underground connection between the Barredo shaft and the Pozo San Inocencio of Minas de Figaredo — later the Pozo Figaredo of HUNOSA — via their respective fifth levels and additional connections at higher levels. From December 2007 the shaft was allowed to flood. By summer 2009 the water had risen to the 150-metre safety level and pumping was resumed using submersible pumps installed in the shaft.

In 2011 HUNOSA began extracting the pumped mine water as a geothermal energy source for climate control of two university campus buildings at Mieres — the Centro de Investigación and the Residencia de Estudiantes — in a pilot project conducted with the Instituto Geológico y Minero de España and the Universidad de Oviedo. The district heating project was subsequently expanded. In 2019 the International Energy Agency awarded the Pozo Barredo district heating project recognition as one of the six most innovative and efficient projects of its type in the world, co-financed by FEDER funds.

The principal surviving structures of the Pozo Barredo — the headframe, the engine house with its largely intact Schalker Eisenhütte extraction machinery, the chimney, the bocamina of the Socavón Barredo (bearing the inscription 'Grupo Mariana 1920'), the compressor building, and the electrical substation — were rehabilitated as part of the Parque Temático sobre la arqueología industrial minera de Mieres under a project approved by the Consejo de Gobierno del Principado de Asturias on 14 February 2007, with a budget of 2,364,430 euros. The former lampistería was demolished during these works. The Campus Universitario de Barredo (Campus de Mieres) was constructed on the former madera (timber yard) of the colliery.