The construction of the section between Saddleworth and Pole Moor was a complicated task, given the inhospitable conditions of its hilly terrain, numerous peat bogs, and undesirable weather. To build this section of the motorway, large amounts of material had to be excavated, consisting of solid rock and peat, which had to be cut from the rock strata and was eventually deposited on hillsides adjacent to the motorway. In addition to the problems caused by the removal of the material, the geology of the moors resulted in the engineers needing to split the carriageways for three-quarters of a mile in the middle of this section, sparing Stott Hall Farm from demolition. Two notable bridge constructions were the bridge carrying the Pennine Way, which is curved downwards with long cantilevers, and the Scammonden Bridge, often called the longest single-span non-suspension bridge in Britain, which carries a B road above the motorway. The mile-long section between Pole Moor and Outlane suffered fewer problems, with the summer weather being satisfactory.
Information adapted from Wikipedia, the free encyclopedia.