Canning Dam

Child Places

• 03709 Canning Contour Channel (fmr)

Statement of Significance

The place, including the dam structure and environs, is of aesthetic significance to the community as a destination for picnics and recreation.
The dam is of aesthetic value for its innovative structural and hydraulic design. The elegant simplicity of the curved concrete dam wall, and the use of simplified neo-classical detailing on the gatehouse and balustrade give the structure visual qualities.
The place has historic value as it provided Perth with its water supply and contributed to the post war development of the States capital.
The place represents a large-scale engineering project constructed in the period before World War II involving the establishment of a townsite for workers.
The place is associated with a number of prominent engineers closely associated with its design and construction including Russell John Dumas, Donald Campbell Munro, Victor Cranston Munt, Thomas Cowley Hodgson and Frederick Washington Lawson.
The place is associated with the prominent Western Australian benefactor Sir Charles McNess, whose financial assistance permitted the upgrading of public access to the place by the State Gardens Board.
Canning Dam can be considered a benchmark site in the history of the provision of Perth’’s water supply and in the history of concrete gravity dam construction in Western Australia.
The dam is of social significance for associations with the sustenance work programme in the 1930s. The project was planned to be labour intensive and as result is associated with a large numbers of Western Australians.
The design and construction of Canning Dam are of scientific significance for their innovation and technical achievement.
Canning Dam is a fine representative example of a concrete gravity dam constructed in the Inter-War period, and it represents a high degree of technical excellence.

Physical Description

The site is situated within the valley of the Canning River in the Darling Plateau, approximately 33 kilometres south east of Perth. The Dam wall is situated in a narrow gorge running east and west, with rock sides sloping upward from the river bed at a slope of approximately one in four. Behind the dam wall, the south branch of the Canning River joins the main stream, with the impounded water forming a lake which stretches back in three arms to the east and west.
The dam wall is a concrete gravity structure with a curved form constructed on a base foundation of rock. The wall consists of a series of mass concrete monoliths poured in-situ. The structure includes a concrete road and reinforced concrete balustrades along the top of the dam, and a concrete gatehouse centrally located at the top of the dam wall on the upstream side. There is also a concrete valve house at the base of the dam on the downstream side. There is a spillway at the southern end of the dam wall with a reinforced concrete training wall downstream of the spillway which controls water run-off. The dam is terminated at each end by concrete piers, which are located either side of a roadway, and a concrete retaining wall on the northern side of the dam.
A quarry associated with the construction of the dam is located 400m downstream from the southern abutment of the dam, and comprises a quarry face, approximately 20 metres high, and a large open area in front of the quarry face containing some loose remnants of equipment and machinery.

History

Development of the Canning River as a source of water supply for Perth was first proposed in a report of the first Metropolitan Water Works Board of Perth in 1896. Investigation of the site began as early as 1897, but despite a series of recommendations from reports of various Inquiries, and extreme shortage of water in some years, government funds were not allocated for construction of a dam until the beginning of a 1930s Depression.
The Canning River supplied water to Perth from as early as 1924, when a pipehead dam was built near Araluen, 6km downstream from the present Canning Dam, as part of the ‘‘Hills Scheme’’, launched by Premier Sir James Mitchell in 1924 to address Perth’’s chronic water shortages.
The construction of Canning Dam ended a long period during which Perth’’s water supply was generally unsatisfactory in quality and in quantity. From the time of its construction, until the boom growth of Perth in the 1960s and the completion of Serpentine Dam in 1961, Canning Dam was viewed by the citizens as the primary source of the city’’s water supply. It still supplies approximately 20% of the city’’s requirements and therefore plays an extremely important role in the context of the development of the city.
The construction of the dam in the late 1930s provided considerable opportunities for employment at a period when the labour market was beginning to recover from the effects of the Depression. Some of the works carried out under the project used unemployed workers who were registered under the sustenance program. It was a vast undertaking for the period and provided much needed work for 500 men and a valuable boost for local industry.
The site for Canning Dam was recommended by engineer Thomas Cowley Hodgson, and was designed by Russell John Dumas, who also directed the majority of the construction works. Victor Cranston Munt was a hydraulic engineer under Dumas, and an early resident engineer on construction of the dam. Donald Campbell Munro was an understudy to Munt and was later also a resident engineer on construction of the dam.
While state of the art materials handling methods were used, in some instances, labour saving machinery worked beside operations intended to maximise the labour content. Sustenance workers were employed chiefly on site preparation, road construction, foundation excavation clearing timber from the reservoir basin, and on some concreting operations including an excavated, concrete lined outlet channel some 15km long which was constructed entirely by hand. Skilled workers were required on the dam for fixing the formwork into which the concrete was poured and these were probably employed at normal day labour rates, the main employment method used on the project.
Rock for the concrete aggregate was obtained from a quarry about 400m downstream of the southern abutment of the dam. The rock was crushed and screened to a maximum 75mm size then transported
by conveyor belts to the concrete mixing plant located close to the southern abutment of the dam. Duplicate crushers were used to prevent stoppage of output during maintenance times. Swan Portland Cement supplied the cement, while the sand was obtained from a pit located between Armadale and Kelmscott. Two cables of the long chuting system were fixed to two massive steel towers, each 76m high. This chuting system and skips were used to distribute the cement to the required positions of the wall.
The completion of the dam in 1940, approximately coinciding with the outbreak of World War II, had the result of reducing the effort taken to clean up at the end of the construction period. As a result, elements of the construction process that would normally have been removed were left at the site, providing the physical evidence of the construction techniques and to some extent the technical innovations used on the dam.
Several innovative design concepts and construction methods that were new to Australia were introduced on the project, while others which were used on the Wellington Dam, were improved upon at the Canning Dam site.
These innovations included; the bulk handing of cement (instead of bagged cement) which was hauled in by rail and transhipped to road trucks for cartage to the dam site; batching the concrete materials by weight instead of by volume; using water spraying to obtain a good key for the monolithic concrete blocks in the construction of the dam wall; creation of a cut-off trench near the upstream face of the dam and provision of a rock-filled drain downstream to intercept any water seepage between the rock face and the concrete of the dam; the inclusion of an internal drainage system to relieve internal seepage through the concrete; the use of immersion vibrators for the compaction of concrete at the dam; the use of conveyor belts to convey the crushed aggregate from the crushing plant to the batching plant 285 metres away; and, the system of chuting concrete using two high towers to support the chutes, which had been devised at Wellington Dam, was repeated at Canning Dam on a much larger scale.
In 1952 the intake of water in Canning Dam was augmented by the diversion of a stream, from the adjacent Kangaroo Gully catchment, by means of a pipe head dam and contour channel. The Kangaroo Gully Contour Channel is built above the Canning Dam and diverts water into the dam. In the 1970s, the Canning Tunnel was blasted through solid granite from Canning Dam to Roleystone to boost water flow from the dam. In 1988, work began to strengthen the dam wall to preserve the reservoir for future water needs.

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This information is provided voluntarily as a public service. The information provided is made available in good faith and is derived from sources believed to be reliable and accurate. However, the information is provided solely on the basis that readers will be responsible for making their own assessment of the matters discussed herein and are advised to verify all relevant representations, statements and information.