Black Bobs Creek Bridge, Sutton Forest

In 1828 Major Mitchell as Surveyor-General of NSW, made plans for the realignment of large sections of the major arterial roads leading from Sydney, including the Great South Road.

in June 1832 the Governor authorised construction of one section of the Great South Road from Lupton’s Inn 16km south of Picton, to Goulburn. Mitchell’s New Line necessitated the building of several substantial bridges, including one over Black Bob’s Creek. Mitchell’s plans for improvement of the colony’s Great Roads were greatly assisted by David Lennox, a Scottish stonemason who had twenty years’ experience in bridge building before emigrating to New South Wales. Lennox is considered the most significant of the early bridge builders/designers in NSW.

Lennox designed three bridges on the Great South Road and of these, only the stone abutments and retaining walls associated with the bridge over Black Bob’s Creek are extant.

At Black Bobs Creek, Lennox originally proposed a stone arch similar to the one he had constructed at Berrima. However, the design was changed to that of a timber beam bridge, which was completed in 1836.

The timber span was replaced, first in 1860 by another timber bridge, then in 1896 the Department of Public Works contracted John Wallace Park to construct a ‘concrete arch culvert over Black Bob’s Creek, Main Southern Road’. The span of the new bridge - an un-reinforced concrete arch, was reduced by 10 ft (3 m) to about 20 ft (6.1 m), and the void filled with earth and rubble. The substantial stone abutments of Lennox’s bridge were retained and the concrete of the arch was detailed to appear like stone blocks.

The concrete arch which in 1896 replaced Lennox’s timber beam bridge, was the first un-reinforced concrete arch bridge in NSW and is the oldest existing concrete bridge in the State. It remained in service for 75 years despite the concrete having been made from low strength sandstone aggregate. When the highway alignment was altered and a new bridge was built nearby in 1971, it effectively removed traffic from Black Bobs Creek Bridge.