Murrumbidgee Bridge Completed
21 February 1867 Empire (Sydney)
During this month the iron work of the bridge on the Murrumbidgee has been completed, and one half of the floor has been laid.
The bridge is of three spans, of 100 feet' each of the type known as the warren girder, with cast iron cylinders 6 feet in diameter, two for each.
The warren girder was adopted with a view to facilitate transport and erection, and to economise skilled labour, so expensive and difficult to obtain so far in the interior, and also to expose the bridge for as short a time as possible to the violent floods of the Murrumbidgee.
The superstructure for which drawings were made in the greatest detail in the colony and forwarded to England, was erected and tested at the works, and taken to pieces and again fitted together in the most satisfactory way, at Gundagai, the working drawings not having been deviated from in the slightest degree.
The contractors, determined on obtaining the piers from the Fitzroy Mines; the design was at their in-stance modified, and six feet cylinders substituted for nine foot segments.
The great delay in obtaining the cylinders threw the construction of the bridge back more than twelve months, causing a further delay in the carriage, which, during, the drought, was almost impossible to obtain, £20 per ton having been paid for the conveyance of some of the cylinders from Fitzroy to Gundagai; the, total cost of carriage amounting to £5000.
The high cost of carriage also regarded the work, by almost precluding the contractor obtaining proper apparatus, so that the appliances for the sinking of the cylinders had to be made on the ground. The cylinders for the North River piers are sunk seventeen feet below the bed of the river; great difficulty was encountered in cutting under water through the trunks of several large trees imbedded in the earth.
The cylinders were sunk without pumping out, and the bottom length filled with concrete, the cylinder then pumped out and the filling completed to caps with brickwork in cement and mortar.
The cylinders for South River piers were let into the rock, which was chiselled out to receive them.
The caps are sixty feet; from the base to the floor of the bridge is fifty feet over summer water and ten feet above the highest flood on record. About one-half of the cylinders were cast at the Fitzroy Mines, the remainder, by Messrs. P. N. Russell and Co.
This is first application of Australian iron for this purpose. Since this bridge was designed, the progress in the manufacture of steel has been so great, that it is proposed to apply that material wholly or partially to the future construction of bridges in the far interior.
The great cost of carriage of the additional weight of iron required more than compensates for the additional price of steel.
It is to be regretted that the finances of the colony do not admit of the large bridges in the interior being constructed in the first place of iron or steel, which would ultimately be much the most economical material.