If 60.1(12) is deleted as a Z clause, what stops the Contractor claiming for the same event under 60.1(19)?
I doubt you’d have success with this approach.
By deleting the express provision of the contract that deals with physical conditions the intent of the Employer was clearly to transfer this risk to the Contractor rather than make it the subject matter of another compensation event by implication.
The Guidance Notes say clause 60.1(19) is a force majeure event which wouldn’t ordinarily include physical conditions.
Also the test to apply is strict, there are five bullet points under clause 60.1(19) and you need to prove that four of them are true for you to have a compensation event. The third bullet point would be your most difficult to overcome, " which neither Party could prevent" - was their nothing either the Contractor or Employer could have done to prevent you from encountering the physical conditions you experienced? I suspect the answers will usually be yes, especially from the Employer.