Determination of Method of Excavation. Trenches for pipelines shall be excavated by either mechanical means or by hand, determined as follows: Trial holes of minimum dimensions 1,0 x 1,0 m shall be excavated by hand along all pipeline routes at 50 m intervals ahead of the Contractor's program for trench excavation. The trial holes shall be to the depth required for the pipeline under consideration to a maximum depth of 1.5 m. If material that cannot, in the opinion of the Engineer, be excavated by hand methods but can be machine excavated is encountered before the bottom of the trial hole, then excavation may be deemed to be carried out by mechanical means, the length of such excavation determined on the basis of other trial hole findings. If hard rock material that can only be removed by blasting or using jackhammers is encountered before the bottom of the trial hole, then excavation may be deemed to be carried out by hand up to the level of the hard rock where after the excavation shall be completed by means of using blasting or jackhammers as appropriate. The length of such excavation determined on the basis of other trial hole findings.
