Grand Junction Canal - Construction

Construction

The Act of Parliament authorised the company to raise up to £600,000 to fund construction. The act authorised construction of the main line from where the eastern branch of the River Brent enters the Thames at Syon House near Brentford, to the Oxford Canal at Braunston. It also authorised branches to Daventry, the River Nene at Northampton, to the turnpike road (now the A5) at Old Stratford, and to Watford: those to Daventry and Watford were not built.

William Jessop was appointed to take charge of construction which started almost immediately from the two ends. On 3 June 1793, James Barnes was appointed Engineer, at a rate of two guineas (£2.10) per day plus half a guinea (£0.52) expenses.

At the north end, there were problems with the construction of Blisworth Tunnel: quicksand was encountered, and errors made in alignment which meant that the tunnel had a pronounced wiggle. With the opening of Braunston Tunnel, the line was open from the Oxford Canal through to Weedon Bec in June 1796. However, Blisworth Tunnel continued to cause problems, collapsing in January 1796. The canal was opened from Braunston to Blisworth in 1797. The canal from the Thames reached Two Waters near Hemel Hempstead in 1798, Bulbourne at the north end of the Tring summit in 1799, and Stoke Bruerne at the south end of Blisworth Tunnel the following year.

Thus with the exception of Blisworth Tunnel, the main line was open throughout in 1800. To allow goods to cross the gap, a road was built in 1800 over the top of Blisworth hill, and later, upon the recommendation of committee member Joseph Wilkes, Benjamin Outram was contracted to build a tramway over the hill.

James Barnes proposed that work begin again on the tunnel on a new line. Robert Whitworth and John Rennie were called in for advice, and supported this proposal. However, construction on the new line did not start until June 1802, and was not completed until March 1805.

Initially, nine locks were used in a temporary arrangement to lower and raise the canal for the crossing of the River Great Ouse at Wolverton at the river's water level. In 1799, William Jessop designed a three arch masonry aqueduct and embankment to cross the river and replace the locks. This collapsed in 1808, and a wooden trough was used as a temporary replacement. It was decided to build an iron aqueduct, with Benjamin Bevan as engineer. The foundation stone for the replacement aqueduct was laid on 9 September 1809, and it was opened on 22 January 1811.

The Grand Junction Canal had reduced the distance to London from the Midlands by 60 miles (100 kilometres)—via Oxford and the River Thames—and made the journey reliable. As a result it thrived: in 1810 it carried 343,560 tons of goods through London, with roughly equal amounts into and out of the capital.