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.

You would have to establish that they had not used reasonable skill and care or complied with the Scope under clause 21. Presuming you can establish the former then this is an insurable risk and as such you would claim under their professional indemnity insurance to recover your losses (see clauses 80, 81 and 82).