The Contract brief at the tender stage of this contract was that the two reactor buildings, also referred to as the Safestores at the Trawsfynydd site were to be converted into a condition within which they could be left unattended for several decades – a state also referred to C&M period (Care & Maintenance Period). In the future, following the successful completion of the Height Reduction Enabling Works (HREW) Project, both buildings would be reduced in height and during this process, the current external face of the buildings would also be removed and so exposing some of the interior of the building. To prevent water ingress into the centre of the building and damage to the structure of the building it was necessary to provide an additional inner weather envelope and these elements of works formed the majority of this contract’s deliverables. These works would also allow the designed passive vent system to be implemented. The other major element of work was the asbestos cleaning of the eight cable risers across the two buildings, to eliminate any residual asbestos risk during the C&M period. At the end of the project, the buildings would be placed in a quiescent state with no active building services and the only live electrical cables being those that supply other operational areas on site. 

To submit a tender and hopefully deliver this project on behalf of the Client, Magnox Limited,

OBR Construction partnered up with Erith Contractors Limited – a National enabling specialist with asbestos removal and handling expertise as well as an established demolition capability. OBR Construction would undertake the majority of the scope with Erith Contractors undertaking the works to clean the eight cable risers. Each of the two buildings contained four cable risers, vertical shafts from ground floor level to the fifth floor – a height of approx. 23 metres. All risers were contaminated with asbestos and required to be cleaned to obtain a four stage clearance. 

OBR Construction therefore undertook the construction of ‘sidewalls’ of steel cladding fixed to the existing structure. Associated works included the fabrication and installation of additional staircases, forming new openings within brick and mass reinforced concrete walls and waterproofing the masonry walls of the staircases and fire-door replacements. In general, other elements of OBR’s works were the sealing of cable tunnels, de-servicing the buildings and sealing between cable risers and sub-floor voids.

Extensive diamond coring and concrete cutting works were involved and OBR Construction delivered the majority of our works utilising our own directly employed skilled workforce and specialist Hilti plant and equipment including an additional scope of work to core some holes directly through the 3.2 metre thick reinforced mass concrete Bioshield walls which was only the second occasion for this to be successfully delivered within the UK. 

The successful bid of just over £9m was submitted as a JV (Joint Venture) between Erith and OBR Construction and upon award, the project was commenced in the Autumn of 2019 with physical works starting during January 2020. However, in mid-March 2020 the government introduced the national lockdown and Trawsfynydd being regarded a sensitive government site, was locked down for approximately 6 months during which no physical works were undertaken. Initially OBR’s portion of the scope was valued at £4.5m with Erith’s elements being £4.6m.

Administration and weekly progress meetings continued throughout the lockdown period via virtual meetings and a considerable amount of background issues were discussed and resolved in preparation for a phased return to site during September 2020 which were then subject to numerous restrictions and control measures to prevent the further spread of the Covid-19 virus. 

Eventually, full return to site was achieved by around Jan-Feb 2021 and the project continued and successfully delivered by June 2023 with Erith completing their objectives by Feb 2023 and OBR’s activities continuing through to June. An additional works scope was added / instructed for OBR Construction to undertake the completion of the construction of the Capping Roof which increased the total value of OBR’s portion of the contract to just over £6m. Overall, the total project value increased to £11m. 

OBR Construction’s full time on-site team on this project consisted of a Project Manager, a visiting QS, A Works Manager, an Trainee Project Manager, two General Foreman and a team of some twelve multi skilled operatives carrying out groundworks, diamond coring, electrical decommissioning and strip-outs, fire doorsets replacements and various steel fixing activities. 

Currently, following the successful delivery of this project, OBR Construction are already in discussions with major demolition companies with a view to perhaps partnering again to undertake the actual Height Reduction works to both the Safestore buildings at Trawsfynydd which are scheduled to be commenced during the Autumn of 2024.