Geograph - photograph every grid square

Usually referred to as “Bleach Green viaduct” there are three viaducts carrying the lines from Belfast to Ballymena/Londonderry and Larne Harbour across the Three Mile Water and Valentine’s Glen, to the north of Whiteabbey station.
When opened in 1848, the line to Ballymena used the Larne line as far as Greenisland (then called “Carrickfergus Junction”) where it left, by a trailing junction, to head towards Monkstown and Ballymena.
This indirect route resulted in longer journey times and time-consuming operations as locomotives ran round their trains. In 1931 work started on the construction of a loop line from Bleach Green to Monkstown, the effect of which was to create a shorter, direct, line from Belfast to Ballymena and Londonderry and eliminate the reversing at Greenisland.
A special train, on 17 January 1934, marked the formal opening of the loop line (of just under 1½ miles) and viaduct.
The project also involved the building of a new viaduct for the down Larne line and the creation of a burrowing junction (remotely controlled) where the down Larne line ran under the main line.
The main line viaduct, of reinforced concrete, is 630ft long, 70ft at its highest and has ten arches. It has a ruling gradient of 1:176½. The down Larne line viaduct (also reinforced concrete 400ft in length and 40ft in height. The original stone viaduct carrying the up Larne line (1848) remained in use.
For further reading see “The Northern Counties Railway” by JRL Currie, David & Charles (1974).