Pozo Barredo Mieres · Asturias · Spain

The surface area around Pozo Barredo had been an established industrial zone of Fábrica de Mieres since the nineteenth century. The company operated Mina Mariana, a mountain coal working on the western slope of the Macizo Polio with fifteen working levels, whose output was transported down inclined planes to the Barredo area and from there by a mineral railway inaugurated in 1882, designed by company engineer Jerónimo Ibrán y Mulá, through Mieres to the company's smelting works at Ablaña. A thermoelectric power station was established at Barredo in 1916. A coal washing plant was commissioned in March 1922.

As Mina Mariana's reserves declined, Fábrica de Mieres deepened exploitation through the Socavón Barredo, a drainage and haulage adit put into service in 1923, seven metres above the Adanero-Gijón road, whose entrance portal still survives bearing the inscription GRUPO MARIANA – 1920. A balance shaft connected the adit to the first working level. A further mountain working, Mina Coruxas (also known as Corujas), lying to the south of Mariana at a higher altitude, was served from 1926 by a 1,800-metre tricable aerial ropeway with 21 iron towers carrying output to the Barredo washing plant.

By the mid-1930s the combined output of Mina Mariana and Mina Coruxas had fallen sharply from a peak of 480,000 tonnes to approximately 194,000 tonnes annually, and the exhaustion of the yacimiento at accessible levels was acknowledged as critical. In 1935 the president of the bondholders' committee announced an investment of 3 million pesetas over four years to sink a vertical shaft at Barredo. Sinking of the new shaft began in 1937 during the Civil War, with only 12 metres profundised in that year. By 1940 the shaft had reached 200 metres. The extraction machine, a Schalker Elsenhütte double-drum unit with 4-metre drum diameter, powered by a Siemens motor, was acquired in Germany; its delivery was delayed by the outbreak of the Second World War and it did not enter service until September 1941. The riveted-iron lattice headframe, 31 metres in total height including the visor, was installed in the same year. The frame is notable as one of the last examples of its construction type, as electric welding rapidly displaced riveted lattice construction for headframes immediately afterwards. Its design is distinctive: the bracing struts are substantially taller than the four main legs, because the headframe foundation is set at the level of the winding house, which is considerably lower than the external loading platform that connected with the Mariana workings above.

At the formation of HUNOSA (Hulleras del Norte, Sociedad Anónima) in 1967 under the Instituto Nacional de Industria, Pozo Barredo was absorbed into the new state enterprise as one of the principal contributions from Fábrica de Mieres. From 1969, the shaft began to exploit the working level between the third and fourth platforms (between 20.7 metres above sea level and 50 metres below sea level), access to the fourth level being via an inclined roadway of 283 metres at a 15 per cent gradient, since the third level had previously been the lowest working point of the shaft. In 1981 HUNOSA commenced reprofundisation of the shaft from the third to the fifth level, ultimately extending the depth to 355 metres, with the fifth level at 135 metres below sea level. At peak output the shaft produced approximately 131,000 tonnes annually with a workforce of around 700 miners.

On 22 December 1991, thirty-six union executives of SOMA-UGT and the Sindicato Regional de la Minería of CC.OO., led by José Ángel Fernández Villa and Antonio González Hevia, occupied the fourth working level of the shaft in protest at HUNOSA's Plan de Reconversión Industrial, which proposed large-scale workforce reductions and pit closures. The occupation lasted until 3 January 1992, during which time the general secretaries of UGT and CC.OO. visited the mine in solidarity. The Barredo encierro is regarded as a defining moment in Asturian mining trade unionism.

Extraction at Pozo Barredo ceased in March 1995, and formal closure was recorded as 31 July 1995. The shaft continued in use for maintenance, drainage, and ventilation functions owing to its underground connection with the Pozo San Inocencio (later Pozo Figaredo of HUNOSA) at Cortina. From 1995 the fourth and fifth levels were also used for mining safety research projects by the Gobierno del Principado de Asturias, with this activity subsequently extending to the surface installations as well. In 2001 the Fundación Barredo was constituted to manage training, professional development, and research activities on the site.

In December 2007, following the closure of the Pozo Figaredo with which Barredo was directly connected underground through both fifth levels, the progressive flooding of both shafts began. By the summer of 2009 the water had reached the safety level of 150 metres above sea level, at which point pumping recommenced using submersible pumps installed in the shaft casing.

From 2011, HUNOSA has utilised the pumped mine water as a source of geothermal energy in a pilot project developed with the Instituto Geológico y Minero de España and the Universidad de Oviedo. The water, drawn from a subterranean flooded reservoir formed by the worked-out voids of the Barredo and Figaredo shafts and maintained above 20°C by geothermal exchange, is used for heating and cooling. Two buildings on the Campus Universitario de Barredo (also known as the Campus Universitario de Mieres) — the Centre for Research and the Student Residence — were the first recipients in 2011. The Hospital Álvarez Buylla, two kilometres away, was added in 2014, and the building of the Fundación Asturiana de la Energía (housed in the rehabilitated former compressor building of Pozo Barredo itself) in 2016.

The surface heritage complex was rehabilitated under the project Rehabilitación del área industrial del Pozo Barredo y Mina Mariana, approved by the Consejo de Gobierno del Principado de Asturias on 14 February 2007 with a budget of 2,364,430 euros. Surviving structures incorporated into the Parque temático sobre la arqueología industrial minera de Mieres include the 1941 headframe, the winding house (which retains most of the original Schalker Elsenhütte extraction machinery), the thermoelectric chimney, the Socavón Barredo bocamina with its inscribed portal, the compressor building (now housing the Fundación Asturiana de la Energía), and the electrical substation. The lampistería (lamp room) was demolished during the rehabilitation works. The former timber yard of the shaft is now occupied by the Campus Universitario de Barredo. The winding house was also rehabilitated in the early twenty-first century to house offices of the Fundación Barredo and the Fundación Asturiana de la Energía, retaining its 20-tonne overhead crane.