In reference to a NEC4 Option A, an event which is an Employer’s risk is stated in Cl 80.1. No Further risks have been added in this section by the Client, and this was displayed to the bidders during the tender stage, therefore the contractor is to accept all risks. Well that is what we want!
However, as NEC try to avoid provisional sums, if the Contractor includes a clarification, e.g: ‘no allowance has been included for tunnels/caves below ground level’, as this was not determined within a GPR survey (site information) before tender, what is the best step? Can a provisional sum be included, still be Contractor risk.? Or Client to accept risk, therefore update 80.1, and this to be issued as CE if it occurs?
Clause 80.1 is a sub-set of a compensation events as clause 60.1(14) says that a compensation event is “an Employer’s risk event” i.e. as per clause 80.1.
However, I think you are looking at the wrong clause for a physical condition risk. I think you should be looking at clause 60.1(12) for what physical condition "an experienced contractor would have had judged at the Contract Date to have such a small chance of occurring that it would have been unreasonable to have allowed for"and also at 60.2 for what information to take intro account when making this judgement.
So, if you include the clarification somewhere in your bid, you will give the PM some ammunition to say “well you thought about it”. If you to include this clarification, clearly state that something like 'Based on the data in the Site Information, as an experienced contractor" - and why would they use you if you were not - “we judge that the likelihood of tunnels/caves below ground level has such a small chance of occurring that no allowance has been made for it in our tender.”