Client
Cleveland Potash Limited
Value
£1.27M
Sectors & Services
Buildings Repairs & Refurbishment Nuclear & Power Concrete Repair Coatings Corrosion Control Cleaning & Preparation Projects
Boulby Mine, situated within the North York Moors National Park, is the world’s first and only Polyhalite mine, producing a natural multi-nutrient fertiliser rich in potassium, calcium, magnesium, and sulphur. The main mine shaft building, a 50-year-old cast in situ concrete structure with primary and secondary steel reinforcement, provides access to the UK’s deepest mine at 1,200 m.
With external walls rising 45 m and 12.5 m in diameter, significant structural deterioration had occurred, including cracking and spalling caused by corrosion of reinforcement from chloride exposure and high internal humidity.
CRL was appointed Principal Contractor in October 2020 to undertake essential structural refurbishment while maintaining operational access, ensuring safety, and addressing long-term durability.
Services undertaken
- Erection of 45 m fully encapsulated scaffolding
- Extensive hydro-demolition works to remove defective concrete
- Internal and external concrete repairs
- Cleaning and preparation of structural steelwork
- Installation of over 2,700 sacrificial galvanic anodes
- Application of hand-applied and dry-spray concrete repair materials
- Carbon fibre strengthening of key structural elements
- Application of two layers of anti-carbonation coatings
- Surface cleaning to remove contaminants prior to coating
- Safety management including exclusion zones and risk assessments
- Maintenance of operational access during internal works
- Quality control and adherence to repair specifications
- Environmental management including waste recycling and emissions monitoring
The refurbishment commenced with extensive planning to allow internal and external works without interrupting shaft operations. Externally, a 45 m fully encapsulated scaffold was erected around the shaft, providing safe and controlled access. Hydro-demolition techniques were employed to remove 31 m³ of defective concrete, exposing reinforcement for cleaning and preparation. Structural steelwork was installed to strengthen key elements, with existing steel cleaned and treated to remove rust and laitance. Over 2,700 sacrificial galvanic anodes were incorporated into the repairs to mitigate future corrosion, enhancing the service life of the reinforced concrete.
Concrete repair mortar was applied using a combination of hand-applied and dry-spray methods, ensuring precise adhesion to the prepared surfaces. Once repairs were complete, the structure was thoroughly cleaned to remove surface contaminants before two layers of anti-carbonation coatings were applied. Approximately 3,500 m² of coating was carefully applied to deliver uniform protection. Carbon fibre strengthening was also integrated into critical areas, providing additional structural reinforcement. The project included robust safety protocols, including exclusion zones, and achieved circa 30,000 man-hours without incident. Comprehensive quality control ensured repairs met the highest standards despite the logistical challenges posed by pandemic restrictions.
"With close collaboration between ourselves as principal contractor, the client and our sub-contractors, the project has run smoothly without any major issues."
Matt Robinson | Regional Manager | CRL
Long-term durability and corrosion prevention were prioritised through the application of anti-carbonation coatings over the repaired concrete surfaces. These coatings, combined with the installed sacrificial anodes, provide a robust barrier against chloride ingress and reinforcement corrosion, significantly extending the life of the shaft. Surface preparation ensured optimal adhesion of the protective layers, while structural steel elements received thorough cleaning and treatment to prevent future degradation.
By integrating carbon fibre strengthening and adopting precise repair methodologies, the project delivered enhanced resilience and structural integrity. These measures reduce ongoing maintenance requirements, support effective asset management, and ensure the shaft remains operational and safe for decades to come.
Environmental Benefits
CRL’s restoration approach offered environmental benefits including significant emissions savings. We measure emissions from materials, waste and employee commuting.
When comparing the material requirements and associated embodied carbon emissions of both options (replacement and restoration), there are substantial savings in CRL’s restoration option. We used the UK Government’s conversion factors (2021 – revised January 2022) to calculate the following embodied carbon emissions. We compared the concrete and steel materials requirements to illustrate these savings.
CRL’s restoration approach offered estimated savings of 91% in the volume of concrete required, and 96.5% in the volume of steel required. The total emissions savings from emissions was an estimated 93.8%.
Through our waste management suppliers Reconomy and Wilf Noble Recycling Ltd, 100% of site waste was diverted from landfill, being either recovered or recycled. Reconomy provided us with a waste management carbon emissions report for the project. Using the same waste volume/emissions ratio from our Reconomy reports, we estimate the waste management emissions of the replacement option would have been 93.7% higher.
For both internal and external phases, 66.67% of our full-time employees were from the North-East, helping to reduce emissions from commuting. Those that commuted from further afield would have stayed in accommodation to further reduce travel emissions. We estimate a saving of 85% in carbon emissions.
In summary, CRL’s restoration approach offered an estimated 90.7% carbon emission saving versus the replacement alternative just from the materials, waste management and employee commuting alone. While our calculations have not accounted for all emissions from the project, we have accounted for the main sources. Our total figure highlights the significant carbon savings of CRL’s operations and alternative restoration solution.
Social Value
Our social value delivery focussed on two key areas. Bringing in new employees from the local region and carbon emissions savings made through our sustainable approach to restoring the man riding shaft. We used the National TOMs Framework to give a financial social value delivery.
Employing locally is important for CRL to support local economies and communities. We have a strong workforce based in the North-East. In addition to many existing CRL employees from the region, we were able to recruit 6 direct employees based in the North-East, including Darlington, Middlesborough, Newcastle and Sunderland. Total employment time equated to 3 FTE employees. Using the National TOMs measurement NT1, this gave a total social value delivery of £94,383.
Sustainability is at the core of our business model. By repairing and restoring assets, we offer a more sustainable option that the traditional demolish and rebuild approach. This cuts out significant levels of carbon emissions in all areas of the project. The estimated 90.7% saving in carbon from materials, waste and employee commuting is an example of this. Using the National TOMs NT31 measurement, this gives a social value delivery of £43,617.30.
The total social value delivery of this project was £138,000.30.
The project is an example of the benefits of repair/refurbishment over replacement. The cost savings to the Client, the ability to maintain operations and the environmental benefits make this an excellent example of a sustainable construction project.
