Well, firstly, I agree with the sentiments of Dave Miller who seems to know more about this than I do !
Addressing the purely NEC aspects: from what you have said, not only is it clear this could happen and you have closed the more obvious contractual routes for them to claim a compensation event.
The one that remains open is if you instruct them to do the clear-up as this would be a change to the Works Information (NEC3) or Scope (NEC4). However, the obvious counter argument to this would be that "it arises from the fault of the Contractor" and therefore, while a compensation event, has zero assessment (see clause 61.4)
But, given what you say, does it really arise from the fault of the Contractor ? It sounds as if there was a high risk of this happening regardless of which Contractor you employed.
Going back to what Dave said, I would fundamentally re-think the project as otherwise both of you might end up with a large fine and a bad reputation.
Addressing the purely NEC aspects: from what you have said, not only is it clear this could happen and you have closed the more obvious contractual routes for them to claim a compensation event.
The one that remains open is if you instruct them to do the clear-up as this would be a change to the Works Information (NEC3) or Scope (NEC4). However, the obvious counter argument to this would be that "it arises from the fault of the Contractor" and therefore, while a compensation event, has zero assessment (see clause 61.4)
But, given what you say, does it really arise from the fault of the Contractor ? It sounds as if there was a high risk of this happening regardless of which Contractor you employed.
Going back to what Dave said, I would fundamentally re-think the project as otherwise both of you might end up with a large fine and a bad reputation.