Avoiding Liverpool was the aim: All aboard the world's ONLY moving aqueduct
Barton Aqueduct – where heavy metal shifts H2O
Posted in Geek's Guide, 28th July 2016 13:57 GMT
Geek's Guide to Britain There are several fine examples of Victorian engineering still working in Blighty. Tower Bridge in London is one of my personal favourites. I was surprised to discover that another was on my doorstep. Well, 4.34km (2.7 miles) from my doorstep to be more accurate.
The Grade II-listed Barton Swing Aqueduct in Salford was built to solve the knotty problem of how to get the Bridgewater Canal across the proposed Manchester Ship Canal. And bar some routine maintenance, the odd lick of paint and a change of power source from steam to electricity, it has been doing the same job on a daily basis for over 120 years.
What makes the Barton Aqueduct even more interesting is that not only was it the first swing aqueduct to be built but it was also the last. To this day it is unique. And not just in the UK. Scour the globe and you’ll not find another one.
The aqueduct’s origins form part of the story of the Manchester Ship Canal – or the Big Ditch as it was fondly known – which opened in January 1894.
Straightening and dredging the River Irwell to allow sea-going ships to unload in Manchester and thus avoid the punitive charges being imposed by the port of Liverpool had been kicking around for over a century before work started.
A daunting project on many levels, one significant problem had been what to do about the Bridgewater Canal, which crossed the River Irwell at Barton on a stone aqueduct designed and built by James Brindley, the Duke of Bridgwater’s gifted canal engineer.
Heart of operations lies within the control tower. Photo: Alun Taylor
Opened in 1761, the stone aqueduct was a vital link in the north-west’s canal system, so closing it was out of the question. Building a flight of locks to take narrow boats down from the canal level to the Irwell was dismissed too. The speed of the water flow in the Ship Canal on occasion would on make steering a narrowboat across it dicey in the extreme. Brindley himself had dismissed this idea before building his stone aqueduct.
A system of locks and a fixed bridge with enough clearance to allow the size of vessel the Ship Canal could accommodate was a non-starter too.
Both lock-based options would also have caused congestion on the Bridgewater Canal and since the Manchester Ship Canal Company had been obliged to buy the Bridgewater Canal lock, stock and barrel as part of the hugely expensive project (seven years in the building the Ship Canal cost £15m in 1894 or around £1.7bn in 2015 terms) it was keen to maximise income from the Bridgewater waterway.
Luckily the Ship Canal’s ingenious chief engineer, Edward Leader Williams (later Sir), had a plan. The adjoining Barton road bridge was already envisioned as a swing bridge so why not just create a section of canal on a similar pivot and treat it in the same way?
Look at Barton aqueduct today and you see it much as it was when new, the only difference being the removal of the tow-path that once ran above the right hand side of the water trough so horses could pull the barges across.
Measurements, mechanics and how a moving aqueduct actually works
The aqueduct takes the form of a boxed lattice girder frame with an iron water trough made from 0.95cm (3/8 inch) iron plate at the bottom. The trough is 5.4m (18ft) wide by 2.1m (7ft) deep (but only filled to a depth of 1.8m (6ft) and 71.6m (235ft) long. It weighs 1,473 tonnes (1,450 tons) when full of water. Even dry, it weighs a not inconsiderable 660 tonnes (650 tons). The whole enchilada sits on a pivot on an artificial island in the middle of the Ship Canal.
The aqueduct pivot mechanism consists of a 8.2m (27ft) diameter race plate embedded in a series of granite blocks. Sixty-four cast iron taper rollers sit on top of the race plate held in position by a spider ring. On top of that an upper race plate supports the aqueduct and the circular gear ring that connects the hydraulic drive system to the aqueduct superstructure.
Draining the trough before swinging the bridge was originally mooted but was dismissed for two reasons. Firstly due to the time needed to refill the trough and secondly because while the Bridgewater Canal was renowned for the cleanliness of its water - apparently the fishing in it was rather good - the River Irwell was little more than a toilet. Over the previous decades it had developed into a drain for the outflow from the burgeoning industries of Manchester and Salford.
To reduce the pressure of the turning mechanism, a hydraulic press was installed in the pivot. When water was admitted to the press it took up to half the weight. So successful was this system of hydraulic assistance that Leader Williams retrofitted it to several road swing bridges being built over the Ship Canal including the ones at Stockton Heath and Knutsford Road in Warrington.
Hydraulic control levers used to turn the aqueduct, photo: Alun Taylor
When hydraulics are suddenly really, really important
The weight of the structure meant that the design was pushing the limits of the possible. This became clear when the sixty-four 35.5cm (14 inches) mean diameter hollow cast-iron rollers started to deform. By 1927 the structure had dropped by 8.89cm (3 1/2-inches). In 1928 the iron rollers were replaced with steel and since then the bridge has dropped by only 2.4mm (3 3/32-inch). Once the iron rollers were replaced the hydraulic assistance was dispensed with.
You will find an archive picture of workmen replacing the rollers while the trough was supported on four jacks. The concrete jack supports can still be seen on the island. Messing about in a 0.91m (3ft) high space with 660 tonnes of ironwork above my noggin is not a job I’d fancy.
The hydraulic system was originally charged by steam engines and a water accumulator tower situated on the north (Eccles) bank of the canal but in 1939 electricity took over the job and the system is now powered by two Mather & Platt induction motors.
The steam pumping house and water tower were demolished after the Second World War, the site now covered by the houses of Havenscroft Avenue at the end of which is the modern access gate to the aqueduct and bridge site.
A bit moist, but native Mancs will assume it’s just the weather
Opening and closing the bridge involves exactly the same process as on the day it first opened. Barrier gates that when open lie against the bank of the canal and the side of the aqueduct trough are manually wound shut and the 60cm (2ft) gap between them left to drain.
Next, four hydraulic rams push a 12 tonne U-shaped wedge that sits between the canal and the trough up to create some free space between the two. The U-shaped wedge is tapered in profile and faced with rubber on both sides. When the bridge is closed the wedge drops back down under its own weight to form a watertight seal between canal and the trough.
The original steam engines were replaced by electric in 1939. Photo: Alun Taylor
The innovative design of the water seals of the Barton aqueduct certainly owes something to Leader Williams’ time as engineer to the Weaver Navigation and designer of the Anderton Boat Lift. It is remarkable how little leakage there is from the trough gates. Stand underneath them and yes, you’ll get a bit wet, but no more than you would in a light shower. Native Mancunians will assume it’s just the weather.
Many people will tell you that the aqueduct swings through 90 degrees. It doesn't, as even a cursory glance at a map of the site will reveal. While the road bridge crosses the island at a right angle the aqueduct only needs to swing through 73 degrees.
Thanks to the large body of water in the canal, the aqueduct bridge doesn’t suffer from the hot weather stick that can sometime jam the Barton road bridge shut and necessitate a call to the Greater Manchester Fire Service to come and hose down the ends.
The area that immediately surrounds the ends of the aqueduct and the narrow artificial island that houses the bridge, aqueduct pivots and the control tower are not open to the general public. That's no great surprise. The architecture is purely functional, the brickwork a bit shabby, the paint peeling (over the years the bridges have changed colour several times but more recently repainting has taken place only when needed rather than for the sake of aesthetics), the decoration minimal. Functionality is the name of the game.
The island itself has weathered the passing years well despite the not inconsiderable flow of water in the Ship Canal. The regular rooting out of unwanted vegetation aside the Cornish granite stonework has required little in the way of maintenance. Grass now covers much of the island surface at its ends away from the passage of workman's boots.
Some of the woodwork attached to the sides is in need of repair, presumably having been thumped once too often by maintenance barges, but that is ultimately a cosmetic issue and one that merely underscores the fact that this is a working facility not a museum to Great Britain's vanishing industrial past.
Getting past the barriers
Thanks to Peel Ports I did manage to wangle a visit pass. That was one thing. Actual access to the island was another - it’s tricky: you must weave through a narrow gate built into the side of the busy road bridge and down a metal ladder. Once on the island the chances of falling into the Ship Canal are pretty high thanks to only intermittent railing on the island. And there's quite a lot of exposed machinery. Hard hats, work boots and high viz jackets are very much the order of the day.
I'd half-expected the operation of the bridge to be largely an automatic affair. Large buttons with Open and Close on them figured in my imaginings. I could not have been more wrong. Operation is conducted from inside that four-storey piece of stolid-brown brick utilitarian that’s the control valve control tower that spans most of the width of the island.
Climb the creaky wooden stairs of that tower to the top floor of the four-storey block and you find something they looks much like the interior of a Victorian railway junction box. Yes there a PC now but it’s just there to monitor the movement of shipping. It has nothing to do with the operation of the bridge or aqueduct.
By turning a pair of rotating controls - the connectors from which run exposed the full height of the control tower and into the foundations of the island - the operator manually adjusts the hydraulic valves that regulate the water pressure that turns the bridge.
The control levers look every moment their 120-year age, polished by what must amount to hundreds of thousands of actions. Like the aqueduct itself the controls were made to last and the workmanship is evident when you run your hands over the smooth, cold metal.
Steel rollers replaced cast iron examples in 1928. Photo: Alun Taylor
It’s as much an art as a science not least because it involves a knack of judging the amount of momentum in play. Once hydraulic pressure has got the bridge moving very little additional energy is required to keep it moving. White lines painted on the canal abutment walls provide a simple visual guide for the operators to line the trough up when closed.
It is training and manual procedures rather than technology that prevents the bridge operators from emptying the contents of the trough - or conceivably the entire Bridgewater Canal - into the Ship Canal.
Opening and closing the Barton swing bridges takes about half an hour and happens on average once a day. A far cry from the heyday of the Salford docks when it opened and closed like a toilet door in a dysentery outbreak.
Today the regular traffic consists more of sightseeing ferries running between Salford Quays and Liverpool though there is still some commercial traffic heading to and from Weaste Wharf (cement), the Cargills plant (grain) and Irwell Park Wharf (mostly scrap metal these days).
For obvious reasons the aqueduct bridge is swung open first and closed last - traffic on the Bridgewater Canal is pretty sparse while the road bridge is constantly busy with people travelling to that nearby temple of rampant consumerism, the Trafford Centre.
Strangely narrow boat users apparently sometimes complain at the delay caused by the swinging of the aqueduct. Why anyone would moan about being delayed for thirty minutes by a system that has been in use for more than a century and when they themselves are only travelling at walking pace is beyond me.
Keeping the aqueduct operating is down to the expertise and resourcefulness of the staff at Peel Ports. Most new parts, especially for the electric and hydraulic systems which back to before the Second World War and beyond, have to be handmade. Finding people and companies who can do so is becoming more difficult as the years tick by.
Make like a local
Watching the two bridges swing silently from their open position across the Ship Canal to the closed position in which the two structures come to rest line astern along the island on which they sit is rather impressive and well worth a shufti even if Victorian engineering is not your thing.
The best place to watch the bridge and aqueduct do their dance is from the footbridge over the Bridgewater Canal on the southern, Trafford, side of the swing aqueduct at the end of Chapel Place.
But be warned: it’s not overly welcoming. The area was landscaped with tourists and visitors in mind in the mid 1980s and it is from this time that the brick paving and gazebo date but it is a bit dilapidated today.
In 2006 Salford City Council carried out an appraisal to redevelop the area and create the Barton-Upon-Irwell Conservation Area and apply for World Heritage Site status but that seems to have come to nothing.
Barton aqueduct - view from control tower, photo: Alun Taylor
Another area that should offer a good view of both bridges is the open space beside Brindley’s original stone embankment to the north of the ship canal. The abutments of Brindley’s aqueduct survive on the Eccles (north) side of the Ship Canal, the original bridge line being bypassed when the Bridgewater Canal was realigned.
The area was landscaped during the early 1990s but has since become rather neglected, overgrown and uninviting. This area is officially known as the Barton Aqueduct Pocket Park and is now part of a regeneration project led by Salford City Council and funded by the Heritage Lottery Fund so things may improve in the near future.
There is also now also a new, wider heritage conservation area scheme, known as ‘Barton Bridges’, organised by the Peel Group in association with Salford and Trafford Councils with the objective of regenerating the whole area as a visitor attraction encompassing the aqueduct, the road bridge and the nearby Augustus Pugin-designed All Saint’s church.
If you fancy a visit to the Barton aqueduct there are plenty of places nearby to eat and drink.
The Trafford Centre with its huge range of bars and eateries is only a ten minute walk away. It also now boasts a Five Guys burger joint, reason alone to visit if you ask me. Halfway to the Trafford Centre is Table Table, a family pub offering a decent range of nosh. The nearest pub is the Kings Arms, a few seconds stroll away along Barton Lane. Handy if all you fancy is a quick pint. If you want to stay longer, there are several hotels close to the Trafford Centre including two Premier Inns.
The biggest problem in planning a visit is finding out when the aqueduct actually opens and closes. There's no reliable information available, so Peel Ports will be your best bet unless you fancy hanging around until something big chugs along the canal.
By car: M60 to Junction 10 then follow signs for The Trafford Centre then for the B5211 for Eccles. Park on Old Barton Road and a two minute walk from the end of Chapel Place. Or park at the Trafford Centre.
On foot: From the Trafford Centre the Barton aqueduct is a ten minute walk. Public transport: Metro to Eccles then 20 minute walk along the B5230, Barton Lane.