NEC ECC: Liability of acceptance of design

The ECC, Option A is being used on a new power plant project. Secondary Options W1, X2, X7, X16, X18 and Z are incorporated.

The design for the office block has been submitted by the Contractor and accepted by the Project Manager. However, the design does not comply with current legislation.
The Contractor is stating that, as accepted by the Project Manager, that correcting this would be a compensation event.

Who is liable for this and how should it be dealt with?

The Contractor is talking rubbish !

I point you at clause 14.1 of NEC3 ECC : “The Project Manager’s or Supervisor’s acceptance of a communication from the Contractor does not change the Contractor’s responsibility to Provide the Works or liability for his design.”