Colliery site regeneration provides 1,000 jobs

The reclamation and development of former industrial sites is a key plank in the Government’s regeneration policy. In this case study, Wardell Armstrong is playing a major role in the Town Road Project at Stoke on Trent, where 1,000 new jobs will be created.

The Town Road site has been associated with mining activities since prior to historic mapping records. In the 1860s Lord Granville’s Deep pit at the site was sunk to 1,530 feet and employed some 400 men and boys and reputedly was the deepest mine in the midlands.

As part of the major reconstruction works following nationalisation of the mining industry, Hanley Deep pit was connected by underground driveages to Sneyd Colliery at Moorland Road, Burslem and Wolstanton Colliery (now the Asda supermarket site). By 1961 Hanley Deep pit ceased production which switched to the adjoining Wolstanton Colliery. By the latter part of its production life the colliery had extended underground to Cobridge in the west and Northwood in the east. The workings increased in depth and exceeded 3,000 ft beneath the surface, again constituting some of the deepest workings in the country at that time.

Despite its long life and hazardous conditions the mine does not appear to have suffered from any major incident that befell many mines within the North Staffordshire coalfield. The main shafts were maintained for a while to assist ventilation for the continuing mine at Wolstanton. Upon the final abandonment of the mine, the two shafts were infilled; firstly No 2 shaft (1969) and then No 1 shaft (1972). During the course of infilling No 1 shaft metal components within the infill material struck against the shaft lining and the explosive methane mixture within the shaft resulting in a significant explosion killing one of the contractors engaged in the works (April 1972). Subsequent to the explosion, No 2 shaft was inspected and the 2,600 feet column of infill material had subsided into the underground roadways as a result of the violence of the explosion, necessitating removal of the cap and recommencing of infilling operations.

Following removal of the surface headgear and associated buildings the site was placed on the market by its owner, The Duchy of Lancaster.

Remediation task

The site was acquired by Gladman Developments in 2000/2001 who then set about the task of remediating the legacy left by the previous intensive past mining activities.

Wardell Armstrong was appointed by Gladman Developments to complete a physical investigation of the site in order to help quantify the constraints arising from the former site useage. The investigations identified:

  • 12 former mine shafts
  • unstable shallow mine workings
  • possible subterranean gases. A wide range of sub-surface structures including basements, culverts, tunnels and a fan drift
  • possible ground contamination
  • thick deposits of fill materials

Wardell Armstrong was also commissioned to design a remediation strategy to mitigate the effects of these mining related constraints. The mine shafts were located by probe drilling and stabilised as necessary by the injection of a grout mix and covered with a reinforced concrete cap. The shallow mine workings were stabilised by drilling and grouting. No major concentrations of subterranean gas were encountered and passive protection measures were incorporated within each building as a precautionary measure. The buried structures were either removed by excavation, infilled and stabilised or the foundations for the new buildings designed to avoid any subsequent problems. Whilst the site history provided the potential for contamination of the soils within the site, the testing carried out did not identify any significantly elevated levels of contamination. All unsuitable materials encountered during the works were removed from site. A variety of ground improvements works and foundation designs were adopted to overcome problems associated with the variable nature of the thick fill material deposits within the site.

During the course of these works, it was essential that proper regard was given to the potential hazards. Full liaison between the main contractor, D Hamilton Groundworkers, Gladman Developments and Wardell Armstrong ensured that the works were completed without any problems.

Wardell Armstrong was further commissioned as structural engineer in the design of the four new buildings within the site. Gladman Developments itself was responsible for the architecture and project management of the actual construction. The completed development value is around £10 million and is scheduled to provide employment opportunities for some 1,000 people.

In addition to the construction of the buildings and car parks, Gladman is in the process (assisted by Wardell Armstrong’s traffic engineers) of carrying out improvements to Town Road, including the signalisation of the Town Road/Chell Street junction at Providence Square on behalf of the City of Stoke-on-Trent.

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