Between a rock and a hard place.
Agreement on what constitutes rock has always been a contentious issue with little help from methods of measurement. Unlike civil engineering where the engineer states in the preamble what constitutes rock for each job, SMM7 left it up to the parties to the contract to fight it out but NRM2 attempts to rectify this.
Although the definition of rock in NRM2 remains the same as SMM7;
Rock is any hard material that,can only be removed by the use of wedges, rock hammers, special plant or explosives due to its size or location.
Now, NRM2 defines special plant as; Special attachments to mechanical plant such as rock buckets, rippers, hammers and chisels. It includes the situation where the normal teeth of an excavator bucket need to be changed to special rock breaking teeth.
In addition individual boulders not exceeding 5m3, or one that can be lifted out in the bucket of an excavator, does not constitute rock.
Duncan Cartlidge FRICS