Birmingham Canal Old Main Line

An early improvement was to add an extra lock to the Wolverhampton flight; for some reason the bottom lock had been built with a bigger fall than the others which obviously wasted water so in 1784 its drop was reduced and an extra lock (now Lock 20) added above it.

More major improvements were needed to cope with the growing water shortages on the short summit level and steam pumping engines supplied by Boulton & Watt had been erected at both ends by 1779 to recirculate the lockage water; the first canal back-pumping system.  But congestion at the locks led to engineer John Smeaton being engaged to lower the summit by cutting through the hill at the Wolverhampton level, eliminating 3 locks at each end.  This was completed by 1790 and the 3 remaining Smethwick locks were also duplicated with a parallel flight to reduce traffic delays.  (Only the later flight remains in use today although the line of the original locks can still be seen, but the 3 remaining Spon Lane locks are the originals from 1769 and thus the oldest on the BCN.)

However, traffic continued to increase and the locks at Smethwick remained a bottleneck so in 1824 engineer Thomas Telford was consulted and recommended extensive improvements to the main line.  Starting from Birmingham, by 1827 a new wider and deeper channel with twin towpaths was cut straight across the original winding route, leaving the Ouzells Street Loop, Icknield Port Loop and Soho Loop to serve the extensive works that lined their banks.  These still survive, although the following Cape Loop is largely closed and the Soho Foundry loop has all disappeared.

From Smethwick Junction an impressive cutting was excavated up to 70 feet deep to continue the new canal at the Birmingham level through to Bromford Junction at the foot of the Spon Lane locks.   By Smethwick Top Lock Telford built an attractive single-span cast iron aqueduct to carry the Engine Arm canal, and several road bridges which cross the Galton Valley cutting including the magnificent cast iron Galton Bridge.  Near Spon Lane Junction this ‘New Main Line’ canal passes under the more conventional two-arched brick-faced Steward Aqueduct which carries the original route which became known as the ‘Old Main Line’.  Many of the distinctive Horseley Iron Works bridges carrying the towpaths over new junctions were also erected at this time, with some later additions made at the Toll End Works.

A unique feature of the New Main Line is the toll islands built midstream at various key points.  These originally carried a small brick tollhouse and many have central lay-by channels for gauging boats.  None of the original tollhouses survive but a replica has been built at Smethwick Top Lock.  As part of his improvements, Telford also built the Rotten Park or Edgbaston reservoir in 1826 which fed both into the Soho Loop and by a long feeder into the end of the Engine Arm.  This superseded the original Smethwick Great Reservoir which has since been built over.

The Galton Valley section was opened by 1829 and the huge amount of material excavated was already being used to build the extensive embankments of the ‘Island Line’ which continues the New Main Line from the Wednesbury Old Canal at Pudding Green Junction in a dead straight line for over 2 miles to Tipton.  Here the 3 Factory Locks raise it to join the Old Main Line again at Tipton Factory Junction.  From Tipton a new canal through Coseley Tunnel was built, again with twin towpaths, cutting out the long and circuitous Wednesbury Oak Loop, part of which remains open today as the Bradley Arm.  All these improvements were completed by 1838 and shortened the through route by no less than 7 miles, from 22½ miles to 15½ miles.

The Old Main Line had itself been shortened in 1821 by straightening which left the Oldbury and Brades Loops, both now closed.  The Gower Branch with the 3 Brades Locks, 2 of which form the only staircase on the BCN, was opened in 1836 to give another connection between the Old and New Main lines.  A further connection, now lost, had been created where the Island Line cut across the Tipton Green Branch, dating from 1809.  This formerly continued via the Toll End Communication Canal through to the Walsall Canal.

Later improvements included a new Pumping Station opened in 1892 near Brasshouse Lane in Smethwick to raise water between the two canal levels.  In 1974 a new road was built when Galton Bridge was pedestrianised, crossing the Galton Valley on earth embankments and including two new concrete ‘tunnels’, Galton Tunnel on the New Main Line and Summit Tunnel on the Old Main Line.