Site Conditions and NEC4 ESC Option B

Where a Contractor encounters unforeseen ground conditions under an Option B Contract, which causes an increase to the BoQ measure, are they entitled to this increased measure if the Z Clauses exclude claims for compensation due to unforeseen ground conditions.

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Benjamin, I’ll share my view below, but I suspect there could be further detail that could change the landscape.

Assuming that the resulting cost due to the excess quantity is more than 0.5% of the total of the Prices at the Subcontract Date (otherwise there is no issue arising), this would be a CE - provided that the item is already in the BoQ, e.g. excavation.

Now, bringing the reasoning behind the above increase, complicates things due to the Z-clause mentioned. If the reasoning has to be part of the discussion (I personally do not see why, if the BoQ allows for the excavation to be measured in m3 regardless of the ground properties), my question would be what “claims for compensation due to unforeseen ground conditions” exactly include; time, cost or both? It would be more clear if it stated “compensation events”.


I agree with Peter some more detail would be useful. Depending on the method of measurement the quantities are generally measured from the drawings so unless you are referring to say an extra over rate for hard material it is difficult to see why the quantities should increase.

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