Editing Aire and Calder Navigation (section)

===Modernisation===
The Aire and Calder tried to work with the railways when they arrived in the 1840s, by making traffic agreements, but still suffered a significant drop in trade. Receipts dropped by one-third between 1851 and 1856.<ref>{{harvnb |Hadfield |1973 |pp=361–362}}</ref> Thomas Hammond Bartholomew, the chief engineer, had been experimenting with steam power since 1813, and steam paddle tugs had been operating on the system since 1831. When he died in late 1852, two-thirds of the traffic was pulled by steam tugs. His son, William Hammond Bartholomew, replaced him and introduced tugs with propellers soon afterwards. These could tow ten [[Humber Keel|keels]], carrying 700 tons, but were held up at locks, as the keels had to be worked through one at a time. Between 1860 and 1867, the locks from Goole to Castleford were extended to {{convert|206|by|22|ft|m}} to alleviate this.<ref>{{harvnb |Crabtree |1993 |pp=18–20}}</ref>

In 1861, Bartholomew met with the chairman, Warde-Aldam, to propose a system of sectional boats, each consisting of six compartments, with a bow and stern section. The compartments or tubs would be unloaded into ships by a hydraulic hoist at Goole, which would lift them from the water and tip them over. Warde-Aldam thought that such a system could carry 45,000 tons of coal per year, and £13,382 was allocated for three train boats, a hoist, and hydraulic machinery to control the hoist and the lock into the docks. By late 1864, the prototypes were operational, with the stern section replaced by a [[Tugboat|pusher tug]]. Soon afterwards, extra compartments were ordered, as experience showed that a tug and seven compartments could fit into the larger locks.<ref>{{harvnb |Crabtree |1993 |pp=22–33}}</ref> In 1874, Warde-Aldam noted that "...the people now call them '[[Tom Pudding]]s' from their wobbling gait." The length of the trains increased to ten or eleven tubs, but such a train was difficult to steer from the rear, and so the tugs moved to the front and pulled the assembly. In 1880 they carried 151,860 tons,<ref>{{harvnb |Crabtree |1993 |pp=46–47}}</ref> and by 1913 there were 18 tugs, 1,010 compartments, and 1,560,006 tons were carried, 33 times Warde-Aldam's original estimate.<ref>{{harvnb |Crabtree |1993 |p=61}}</ref>

Around 1864, the Aire and Calder dabbled in owning its own railways, purchasing the [[Silkstone Waggonway]] from the [[Barnsley Canal]]. But this proved a poor investment; in 1866 the waggonway carried just 3,246 tons of coal down from a peak of over 32,000 in 1851, and in 1870 no coal was carried at all. In August 1872, it was reported that "the rails have been pulled up and sold".<ref>{{harvnb |Goodchild |1994}}</ref>

[[File:Lock on the Aire and Calder Navigation.jpg|thumb|left|One of the large locks]]
After the [[First World War]], another programme of improvements to the locks was carried out, extending the locks to {{convert|457|ft|m}}, which enabled trains of 19 compartments to operate regularly. Experiments with trains as long as 38 tubs were carried out, but the difficulty of splitting the train to pass through the locks meant that 19 was the usual maximum. The compartments continued until the late 1960s to carry around half a million tons of coal, long after most British canals had ceased to be used for commercial traffic, but the gradual demise of the coal industry led to compartment traffic ceasing in 1986.<ref>{{harvnb |Crabtree |1993 |pp=87–89}}</ref>

The 20th century saw two major phases of improvement. In 1905, the [[New Junction Canal]] connected the Aire and Calder to the [[Sheffield and South Yorkshire Navigation]] near Stainforth. It was funded by the Aire and Calder, with the Don Navigation eventually meeting half the cost.<ref>{{harvnb |Hadfield |1973 |p=377}}</ref> During the 1960s, the navigation underwent another modernisation scheme, in which the locks from Goole to Leeds were upgraded and enlarged to accommodate vessels conforming to the 600-tonne Euro-barge standard.<ref>{{harvnb |Clarke |1999 |p=26}}</ref> There is some variation in lock sizes, with the smallest being at Knostrop, which is {{convert|203|by|22|ft|m}} with a water depth of {{convert|8.4|ft|m}} over the lock cill.<ref>{{harvnb |Freight Study Group |2002 |p=108}}</ref> Euro barges are {{convert|200|by|20|ft|m}}, and when fully loaded with 600 tonnes of cargo, have a draught of {{convert|8.2|ft|m}}.<ref>{{harvnb |Andrews |2000}}</ref> Locks on the Wakefield section can accommodate vessels which are {{convert|195|by|17.6|ft|m}} with a draught of {{convert|7.5|ft|m}}, though rigid vessels are constrained to 141&nbsp;ft to enable turning at Wakefield <ref name=jane>{{harvnb |Cumberlidge |2009 |p=52}}</ref> while the locks below Castleford have three sets of gates,<ref>{{harvnb |ICE Briefing |2008 |p=8}}</ref> so that a {{convert|200|ft|m|adj=on}} section can be used, rather than the full {{convert|457|ft|m}} required by the compartment boats.<ref>{{harvnb |Edwards |1985 |p=41}}</ref>

The main problem with upgrading the Wakefield branch was the dimensions of [[Stanley Ferry Aqueduct|George Leather's cast iron aqueduct]] over the River Calder at Stanley Ferry. Structural analysis showed that parts of the ironwork were overloaded, and so in 1981 a new concrete aqueduct was cast by [[John Laing plc|John Laing Construction Ltd]], on a site a little further upstream. The complete structure was then pushed into position by hydraulic jacks in a six-day operation, after which the navigation was diverted over it, although the old aqueduct was left in place and can still be used.<ref>{{harvnb |Taylor |2003 |p=62}}</ref>

Although coal mining was one of the main reasons for the success of the navigation, it has also brought problems, caused by subsidence. In March 1988, the bank near Lemonroyd lock collapsed into [[St Aidan's|St Aidan's opencast mine]], which then flooded.<ref name=jane53>{{harvnb |Cumberlidge |2009 |pp=53–54}}</ref> A significant factor was the presence of excavations below the opencast workings where lower coal seams had previously been mined. The failure resulted in some {{convert|780000|cuyd|m3}} of material, including the banks of the river and the canal, slipping into the workings, which then flooded to a depth of {{convert|230|ft|m}}, creating a lake which covered {{convert|250|acre|ha}}.<ref name=hughes>{{harvnb |Hughes |Clarke |2001 |loc=Abstract}}</ref> An act of Parliament ('''{{visible anchor|Aire and Calder Navigation Act 1992}}''' ([[List of acts of the Parliament of the United Kingdom from 1992#Local Acts|1992]]. c. iv), was obtained to allow {{convert|1.9|mi|km}} of new waterway to be constructed. The original locks at [[Kippax, West Yorkshire|Kippax]] and Lemonroyd were replaced by a single lock at Lemonroyd.<ref name=jane53/> Opencast mining finally resumed ten years later, after the site had been pumped out,<ref name=hughes/> but the coal reserves are now exhausted, and the site forms a nature reserve, with wet grasslands, reedbeds and open water covering {{convert|740|acre|ha}}.<ref>{{harvnb |Black |Veatch |2010 |p=23}}</ref>