Cromford Canal - Construction

Construction

The canal obtained its Act of Parliament in 1789. Perhaps because they had quoted too little, basing their estimates on Jessop's cost predictions which may themselves have been too optimistic, the contractors soon found themselves in financial difficulties and, at the end of 1790, simply walked off the site. Benjamin Outram hastily took over full management control and was awarded a salary increase. In January 1792 there was a problem when the Amber Aqueduct failed but, by May, the canal to the east of Butterley was virtually complete and most of the earthworks to the west.

The Butterley Tunnel was excavated by first sinking 33 shafts, about 75 yards (69 m) apart as much as 57 yards (52 m) deep to give a number of working faces. Most of the heading was through soil, with some coal measures and iron ore deposits, the final tunnel being lined through most of its length.

By 1793 the company had a balance in hand of only £273 and the cost had risen to half as much again as Jessop's original estimate. Nevertheless the canal was showing an income, unfinished though it was.

In August, however, there were problems with the Derwent Aqueduct which required considerable modification. The spandrel walls had parted due to the horizontal forces imposed by the canal, and a longitudinal split had opened up in the arch. In his report to the canal committee, Jessop gave his opinion that the use of Crich lime, being unusually pure, had delayed the setting of the mortar. Later writers, with the benefit of engineering knowledge acquired after Jessop's time, have suggested that the spandrel walls were simply too slender for the forces imposed. At any rate, the arch was partly dismantled and steel tie bars and lateral reinforcing arches were installed, together with external buttresses. This Jessop did at his own expense.

In the end, despite costing about twice the initial estimate (£42,697) (£3,910,000 as of 2012),, the canal opened in 1794 and was a financial success.