Tesco has asked Costain to conduct a review of its troubled £25m Gerrards Cross project after the dismissal of original contractor Jackson Civil Engineering.
The move follows the collapse on 30 June last year of a 30 m section of the tunnel, which was being constructed by Jackson over a section of the Chiltern railway. The accident disrupted rail services in Buckinghamshire for two months.
Costain, which was originally due to build a supermarket on top of the £20.3m tunnel, will now take three months to assess the future of the scheme.
A Costain spokesperson said: "Tesco has appointed a team, comprising Costain and a small number of new subcontractors, to review the Gerrards Cross project before taking a final decision on its future. We will be undertaking surveying, inspection and ancillary work within the site boundary in the near future."
Tesco has appointed Costain and a small number of contractors to review the Gerrards Cross project before taking a final decision on it
Costain added: "The review will allow Costain to fully understand the details of the project to be able to implement the design in a way that restores public confidence in the safety of the project."
The accident happened while a 30 m section of the tunnel was being backfilled. An investigation by tunnel contractor Jackson showed the collapse was caused by overloading. Tesco paid £8.5m in compensation to rail passengers travelling between Birmingham and London as a result of the collapse. The commuters had an hour added to their journeys.