Historical information

This report lists the depths of water and the consistency of the seabed surrounding the Warrnambool Harbour in October 1929, The information, often referred to as 'soundings', was obtained by Jet Probing,. In earlier days a lead line was used to perform a similar task. The author of the document is unknown.

Jet Probing is a method used for underwater archaeology, cable installation and coastal engineering. A jet probe is a machine that produces a strong jet of water that penetrates the layers of sediment on the seabed, determining their depth, thickness and consistency. It provides a survey of the seabed and can be used as an aid to engineering design and construction.

The report mentions lining up with the wooden jetty, the end of the breakwater and the leading lights. It mentions sand, loose rock and rock. It tells of stopping work due to the water being too rough, the pipe choking, difficulty in connecting pipes, and pipe joint breaking as it tried to get through the sand,

Significance

The report in the document is significant for its connection with the Warrnambool Harbour, Warrnambool Breakwater, Warrnambool Jetty and Lady Bay.

The report gives figures for the depth and consistency of the water and seabed at a particular point in time and can be used to compart with similar figures taken at different times. The results could determine plans for future engineering works.

Physical description

Report, titled 'Jet Probings, Warrnambool Harbour'. Two pages of cream coloured paper with hand written notes in pen and ink.

Report covers three days of Jet Probings, with resulting figures and comments, for the depths of the surroundings of the Warrnambool Harbour. The report is in point form, with some underlining.
Dates of recordings are 14-10-29, 15-10-29 and 16-10-29. (1929)

The situation of the harbour had become a real problem by 1910 and required continuous dredging. In 1914 the Breakwater was extended but proved to be a failure because the work began to subside and by 1920 about two thirds of the harbour was silted up. Alterations made in the 1920's increased the silting problem.

The soundings and Jet Probings were done after the Royal Commission of 1923, when the damaged stonework on the seaward side of the Warrnambool Breakwater, caused by the action of the sea, was the subject of enquiry. A conference between the Public Works, Water Commission and the Harbour Trust concluded that it would less costly to make repairs to prevent further damage rather than replaced the damage portion of the wall. A contract was raised in late 1924 to deposit rubble on the damaged side of the breakwater to minimise the Southern Ocean’s destructive action and work had started by August 1925.

By the 1940's the harbour was no longer used. More alterations were made in the 1950's and 1960's.