Heritage and conservation register

Item

Field Value
Name of Item Narooma Bridge over the Wagonga Inlet
Item Number 4300639
Type of Item Built
Item Sub-Type Steel Truss
Roadloc  
Address **** Princes Highway (SH 1) over Wagonga Inlet Narooma 2546
Local Government Area Eurobodalla 
Owner Local Government
Current Use Road bridge
Former Use Road bridge

Statement of significance

Field Value
Statement of significance The Narooma Bridge, completed in 1931, is of State significance. It has is representative of an important period of development of the Princes Highway and was the first major bridge constructed on the highway by the Main Roads Board as part of its efforts to develop the highway. The bridge represents this period of development in a readily interpretable physical way. Opening span bridges are important in NSW because they are a reminder of the time when river transportation was more common. The design of bascule span used on the Narooma bridge represents a simple, practical and economical solution to the problems posed by the competing needs of navigation and road transport. The Narooma bridge has State technical significance because it represents a significant and rare variation of the bascule opening span which is an important type of bridge in NSW. There is only one other bascule span in NSW which has a similar design and that other bridge is currently threatened with demolition.
Date Significance Updated 13 May 2009

Description

Field Value
Designer Main Roads Board
Builder Morison and Bearby ; State Monier Pipe and Reinforced Concrete Works
Construction years 1929 - 1931
Physical description A three span steel and concrete bridge. The end spans are 48.8 m through span trusses while the central span consists of a 18.9m Bascule span. The trafficable deck is 6.1m wide. A 1.5m footpath was added to the eastern side in 1960. The deck of the truss spans is made up of a concrete slab cast on the stringers and cross girders. The cross girders are connected to the trusses at the vertical web members. The deck of the bascule consists of a steel grate. The truss superstructure is a conventional Pratt design and is made up of composite sections fabricated by riveting channels plates and angles together. All original connections are riveted. The sliding and fixed bearings are of cast steel. The expansion bearing has specially fabricated cast steel turned roller bearings. The bascule span also has two composite bascule girders of riveted members. The bascule girders have quite an elaborate design at the trunnion end with a circular arc to which a quadrant rack has been attached. A pair of pinions made from cast steel drives the racks. Mechanism of the bascule - the pinions are set on a forged and turned nickel shaft that runs east west. In the centre of this shaft is a gearbox containing a worm gear, which connects the pinion shaft to a north south running shaft. This is connected to a retrofitted electric motor and a hand driven shaft by mitre gears. The gears used in the mechanism are made from cast steel and have been machined to specified tolerances. The counterweight is connected to the bascule girder at the top of the arc. The counterweight moves vertically. It is restrained by a lattice portal frame that is in line with the trunnion pin. The weight itself consists of reinforced concrete. There is a cavity to which pig iron has been added to balance the counterweight. The bascule span is locked in position by a series of pins operated by rods, shafts and levers at the end of the bascule girder. The substructure of the bridge is generally made from reinforced concrete. The northern abutment and piers bear directly on rock while the southern abutment sits on a grid of timber piles driven to a set load capacity. The embankments at each abutment are stabilised with a mat of precast concrete blocks which have been bedded together with mortar.
Physical Condition
and/or
Archaeological Potential
Original condition assessment: 'Very good condition considering its design and the harsh environment in which it is located. Some corrosion, spalling and hairline cracks but generally well protected by regular maintenance.' (Last updated: 4/05/2001.) 2007-08 condition update: 'Fair.' (Last updated: 17/4/09.)
Modifications and dates Unknown - Deck of the bascule span changed form original five inch thick hardwood planks aligned across the deck on hardwood plates bearing on the stringers to the current steel grate. 1960 - 1.5m footpath added on the eastern side. 1960 - pig iron in the counterweight repositioned and additional weight added to balance the footpath. RTA painted the truss in 1999.
Date condition updated 17 April 2009

History

Field Value
Historical notes The opening of the twentieth century saw the land around the Wagonga Inlet served by sea. The motor vehicle was in its infancy and the state of the coach and wagon roads made motor transport difficult. A hand propelled punt was installed at the Wagonga River near the heads in 1894. Progress at "Noorooma" then became rapid, with the Moruya to Bega mail coach passing through the township daily.

The push was then on for a bridge. However, the hand driven punt remained until 1929, when a petrol driven punt which had previously operated at Batemans Bay was installed at Narooma.

With the establishment of the Main Roads Board in 1925, priority was given to improving portions of the Princes Highway that were in urgent need of attention. The south coast had a particularly strong need for a good highway because other transport opportunities wee limited. Coastal shipping was in decline and the railway from Sydney stopped at Bomaderry.

As one result, a bridge was proposed over the Wagonga Inlet at Narooma. Construction began in 1929 and was completed in 1931 at a cost of 42,267 pounds.

Listings

Field Value
Heritage Listing Reference Number Gazette Number Gazette Page
Heritage Act - s.170 NSW State agency heritage register       

Assessment of Significance

Field Value
Historical Significance State - Representative of an important period of development of the Princes Highway. One of the first bridges built on the Princes Highway by the Main Roads Board, highlighting the importance of completing the missing link in the highway at the Wagonga Inlet. The bridge's design is typical of this period and as such it helps to define the historical development of the highway in a much more evident way than a section of road or a cutting. Bascule spans are a subset of the group of opening bridges. They are an important reminder of the time when river navigation was important and they demonstrate one solution to accommodating the competing needs of road and river transport.
Historical Association ****
Aesthetic/Technical Significance Local - Has local landmark qualities and sits in a beautiful setting over the Wagonga Inlet. Acts as a gateway to the town and contributes to rather than detracts from its setting.
Social Significance Local - It has local social significance because of its association with local people who helped in its construction.
Research Significance State - It represents a significant and rare variation of the bascule opening span. Bascule spans are a subset of the group of opening bridges. A bascule bridge is one which can be raised and lowered like a drawbridge, with one end hinged and the other free to move. They are balanced with a counterweight using a see-saw principle. Narooma Bridge has particular technical significance because it retains the bascule span in its original hand driven mechanism, even though a later electric motor has been added. The mechanism, though heavy, is simple and could be operated by one person, due to the introduction of ball and roller bearings. It was adopted because it was considered safer against damage than an ordinary opening span.
Rarity Rare, because it has a bascule span, the first of only two built in NSW. The other (Coopernook) is under threat of demolition. The design of Narooma Bridge was used in three other bridges in NSW (and probably Australia). Narooma is the oldest and is the only one likely to remain in its original arrangement.
Representativeness A good example of a bascule span opening bridge.
Integrity/Intactness Good. While the bascule span has been modified by the addition of an electric motor and with adjustments made to the counterweight when the footpath was added to the bridge, the alterations do not detract from the significance of the design because they demonstrate its adaptability. Also, the hand driven mechanism is still intact and usable.
Assessed Significance State

References

Field Value
Type Author Year Title

Study details

Field Value
Title Year Author Inspected by Guidelines used
Heritage assessment and Conservation Management Plan Narooma Bridge  2000  Hughes Trueman Reinhold    Yes 
RTA s170 Register Upgrade Project - Southern Region  2002  Godden Mackay Logan    No 

Custom fields

Field Value
Roads and Maritime Services Region Southern
Bridge Number 5972
CARMS File Number ****
Property Number Bridge
Conservation Management Plan April 2000 - contact Kevin Kennedy, Southern region

Images

View from north east
View from north east
View from south east
View from south east
Bascule mechanism
Bascule mechanism
Counterweight and hinge of bascule span.  Note additional weight on the east side to balance the weight of the footpath addition.
Counterweight and hinge of bascule span. Note additional weight on the east side to balance the weight of the footpath addition.


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