NEC3 PSC Option E - failed design

under an NEC3 option E PSC contract where the scope was to design a section of dual carriage way. if the design was found to have hit a restricted section of land in a small part of the design, which was known to the designer and stated in numerous documents and so definitive proof they should never have encroached the land. what mechanisms are there to deal with the partially failed design under the contract. there is significant costs associated with the re design of this small section which involves land take.