A mineshaft not listed on any plans has been found underneath the Spindles Town Square site during redevelopment.

According to the council, some changes have been made to the approach towards the demolition works on the TJ Hughes building, with risks being managed.

The council said there was no reason to believe the discovery of the mineshaft was going to cause any delays to the overall development, which is hoped to be completed by the end of 2023.

A geological survey analysing several boreholes found two coal outcrops, locations where an entrance to a coal seam – a bed containing a profitable amount of coal – is close to the surface.

Additionally, one entrance to the mine, with a diameter of 2.5 metres (8.2 ft), was found underneath the TJ Hughes building.

Another two mine entrances were found close by.

Oldham Council said staff would be moving into Spindles offices from Monday, October 3, for trials on the working space which will eventually replace the Civic Centre, ready for redevelopment.

The onsite mine shaft was recorded as an ‘Old Coal Pit’ in 1851 maps, the earliest maps available.

No other coal mining features were noted on the site or within close proximity.

The Coal Authority has no records of the shaft being ‘treated’ – for example, filled in or grouted.

No information on the depth of the shaft was available for the shaft on site or one of the shafts nearby, but another shaft nearby, which had been filled in, was found to be 15 metres (49ft) deep – or roughly the height of a five-storey building.

The survey says a ground stability risk is ‘considered moderate to high for the site,’ recommending that intrusive work be undertaken to determine the exact position, size, and depth of the mineshaft prior to re-development to mitigate the risk.

After completion, the building will become the new home of Tommyfield Market – with the former site becoming part of a new public park.

Council leader Cllr Amanda Chadderton said: “The redevelopment of Spindles Town Square Shopping Centre is currently underway, with plans to turn the existing retail-only site into a multi-purpose centre of leisure, retail, office space for hybrid working and new business enterprise centre for the borough.

“We continue to work with the Coal Authority with regards to understanding the nature of the mineshaft under the existing building. 

“With knowledge and awareness of the void, this has changed the approach to the demolition programme of works for the TJ Hughes building - which has started with an internal strip out rather than external demolition; however, the risks are being managed and the overall programme remains on track.

“Updates on the new market hall, timescales and layout plans were recently shared with the market traders and the feedback was very positive about the move to the heart of town centre.”