Store Street Aqueduct | |
|---|---|
 Store Street Aqueduct at the canal level in 2008 | |
| Coordinates | 53°28′47″N2°13′39″W / 53.4796°N 2.2274°W /53.4796; -2.2274 |
| OS grid reference | SJ850981 |
| Carries | Ashton Canal |
| Locale | Manchester, England |
| Maintained by | Canal & River Trust |
| Heritage status | Grade II* |
| Characteristics | |
| Trough construction | Masonry |
| Total length | 220 feet (67.1 m) |
| Width | 17 feet (5.2 m) |
| Traversable? | Yes |
| Towpaths | North side |
| No. of spans | One |
| History | |
| Designer | Benjamin Outram |
| Opened | 1798 |
| Location | |
 Interactive map of Store Street Aqueduct | |
TheStore Street Aqueduct in centralManchester, England, was built in 1798 byBenjamin Outram on theAshton Canal. AGrade II* listed building,[1] it is built on askew of 40° across Store Street, and is believed to be the first major aqueduct of its kind inGreat Britain and the oldest still in use today.
Theaqueduct was constructed to crossShooters Brook. It is built of stone with largevoussoirs and retaining walls of coursed masonry and is 7.4 metres (24 ft) wide with triangularbuttresses. The brook wasculverted in about 1805 and Store Street was built over it. The canal is about 4.6 metres (15 ft) wide and 1.45 metres (4 ft 9 in) deep. The arch has a 7.6-metre (25 ft) square span and a 10.5-metre (34 ft) skew span rising 2.75 metres (9 ft) above road level.[2]
Generally, where a canal (or later a railway) crossed a road, or vice versa, the road would be diverted to cross at right angles. It had not always been acceptable but attempts to build masonryarch bridges at an angle, or "skew", of greater than 15 degrees had proved unsatisfactory. The method up to that time had been to build thevoussoir arch with the stone coursework parallel to theabutments. This transmitted the load outward from the crown in a straight line to the foundations, parallel to the faces of the arch. If a skew was attempted, it threw the lines of force outside the abutments, leading to weakness in the structure.
William Chapman had partially solved the problem in 1787[3][4] when building bridges for the Kildare Canal, the first being the Finlay Bridge nearNaas,Ireland.[5] The Kildare was part of theGrand Canal Company, for whichWilliam Jessop had been the engineer. Jessop would no doubt have discussed it with Outram, his partner, and he experimented with the idea on theRochdale Canal. Examples are Gorrell's Lane and March Barn road bridges, though built possibly later.[4] The method used was to build timber falsework parallel to the proposed arches. Planks were laid on the falsework parallel to the abutments. The position of the courses at the crown were marked out, then those across the remainder of the arch.
Although the aqueduct still exists and is structurally sound, years of neglect led to water leakage through the joints, and the spiral construction can no longer be seen, the surface of theintrados having been rendered.
Later railway engineers improved on the system, producing what became known ashelicoidal construction that became the norm in Englishskew bridge building. An exact solution to the problem was determined in the form of the French, ororthogonal, design. However, this was complicated and expensive to build.
