22-583: Mundaring Weir is a concrete gravity dam (and historically the adjoining locality) located 39 kilometres (24 mi) from Perth , Western Australia in the Darling Scarp . The dam and reservoir form the boundary between the suburbs of Reservoir and Sawyers Valley . The dam impounds the Helena River . A soldier, Ensign Robert Dale , became the first European to explore the region in 1829. European populations did not grow significantly until construction of
44-401: A substation and chlorination facility were decommissioned. New treatment facilities included pre-treatment, filtration, chlorination, stabilisation and fluoridation . The old facilities were not able to sustain increasing water demands and current Australian drinking water guidelines. Aesthetic water qualities such as colour, taste and odour had deteriorated over the years. Mundaring Weir was
66-474: Is that their large concrete structures are susceptible to destabilising uplift pressures relative to the surrounding soil. Uplift pressures can be reduced by internal and foundation drainage systems. During construction, the exothermic curing of concrete can generate large amounts of heat. The poorly-conductive concrete then traps this heat in the dam structure for decades, expanding the plastic concrete and leaving it susceptible to cracking while cooling. It
88-406: Is the designer's task to ensure this does not occur. Gravity dams are built by first cutting away a large part of the land in one section of a river, allowing water to fill the space and be stored. Once the land has been cut away, the soil has to be tested to make sure it can support the weight of the dam and the water. It is important to make sure the soil will not erode over time, which would allow
110-638: The Water Authority of Western Australia 's operations at the Weir maintained housing for its workers. There is a youth hostel (built at the site of the now defunct primary school), an art gallery in the area, and many picnicking spots. There is still rangers' housing at the site, along with functioning pumping stations and water treatment facilities. The 963 kilometres (598 mi) walking trail Bibbulmun Track commences in Kalamunda following Piesse Brook , then along
132-449: The weight of the material and its resistance against the foundation. Gravity dams are designed so that each section of the dam is stable and independent of any other dam section. Gravity dams generally require stiff rock foundations of high bearing strength (slightly weathered to fresh), although in rare cases, they have been built on soil. Stability of the dam primarily arises from the range of normal force angles viably generated by
154-536: The biggest danger to gravity dams and that is why, every year and after every major earthquake, they must be tested for cracks, durability, and strength. Although gravity dams are expected to last anywhere from 50–150 years, they need to be maintained and regularly replaced. Paulls Valley Paulls Valley is a suburb of Perth , Western Australia within the City of Kalamunda . It was officially named in 1973 and commemorates Albert Paull, an early orchardist who settled in
176-607: The dam can begin. Usually gravity dams are built out of a strong material such as concrete or stone blocks, and are built into a triangular shape to provide the most support. The most common classification of gravity dams is by the materials composing the structure: Composite dams are a combination of concrete and embankment dams . Construction materials of composite dams are the same used for concrete and embankment dams. Gravity dams can be classified by plan (shape): Gravity dams can be classified with respect to their structural height: Gravity dams are built to withstand some of
198-518: The dam in the late 1890s. This involved the building of a Mundaring Weir railway line from Mundaring to the Mundaring Weir site. The Irish Australian engineer C. Y. O'Connor was involved in the design of a scheme that transported water to the Eastern Goldfields of Coolgardie and Kalgoorlie in the eastern part of Western Australia. The weir was completed in 1903. The lake created by
220-525: The dam was known as the Helena River Reservoir , it was renamed as Lake C.Y. O'Connor in 2004. The owner of the dam, the Water Corporation , refers to the weir as Mundaring Dam on its website, but no other authority, such as Geographic Names, or Geoscience Australia uses this term. The Shire of Mundaring uses an image of the Mundaring Weir in its logo. Work commenced to raise the dam in
242-434: The foundation. Also, the stiff nature of a gravity dam structure endures differential foundation settlement poorly, as it can crack the dam structure. The main advantage to gravity dams over embankments is the scour -resistance of concrete, which protects against damage from minor over-topping flows. Unexpected large over-topping flows are still a problem, as they can scour dam foundations. A disadvantage of gravity dams
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#1732852228344264-609: The late 1940s, and was completed in November 1951. In the early 1970s the downstream dam from the weir —the Lower Helena Pumpback Dam —was constructed. It last overflowed into the Helena Valley in 1996. In the first fifty years overflows were a regular occurrence. The 1950s raising of the weir affected overflows, but they continued. In the 1960s the weir regularly overflowed. Like any structure of its age and design,
286-451: The lower zig-zag section of the end of the railway line (which can still be seen when the capacity of the dams falls below approximately 35%) feature prominently in postcards of numerous weekend and special picnic excursion trains that travelled to the weir from the 1910s until the late 1940s. The steepness of the Mundaring weir railway line restricted the capacity of the railways to conduct
308-483: The monitoring tunnels. The weir leaks, and the photos below show consistent stain/moisture points between 2008, 2010, 2020 and 2024, where water moves through the structure: A new pump station with an initial capacity of 165,000 cubic metres (5,800,000 cu ft) per day, and an ultimate capacity of 240,000 cubic metres (8,500,000 cu ft) per day, commenced operations in March 2014. The existing two pump stations,
330-511: The picnic trains, as the Msa Garratt locomotives were the most suitable, but in short supply, at times when the weir was overflowing in the 1940s. The railway line was closed in 1952. Additionally, a tramway, using timber rails, was constructed to convey sawn timber from a mill 3 miles (4.8 km) from the site of what is today known as The Dell in Paulls Valley to the weir from where it
352-421: The scheme with guide books, trails, and web-sites to provide information about the history of the scheme. Most of this project was developed between 2001 and 2003. 31°57′36″S 116°10′17″E / 31.9600°S 116.1713°E / -31.9600; 116.1713 Gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only
374-635: The south side of the Helena valley. Crossing the weir wall the track follows the northern side of C.Y.O'Connor lake before turning south and continuing the journey to Albany . The history and context of the whole Goldfields Water Supply Scheme was celebrated by the Golden Pipeline project, where the Water Corporation had the National Trust of Australia (WA) create an " interpretation " of the history of
396-485: The strongest earthquakes . Even though the foundation of a gravity dam is built to support the weight of the dam and all the water, it is quite flexible in that it absorbs a large amount of energy and sends it into the Earth's crust. It needs to be able to absorb the energy from an earthquake because, if the dam were to break, it would send a mass amount of water rushing downstream and destroy everything in its way. Earthquakes are
418-573: The terminus of the Mundaring Weir branch railway , which was originally constructed by the Public Works Department of WA for the transport of materials for the construction of the dam. It was only after the completion of the weir that the location became popular with picnickers and sightseers, as the project caught the imagination of the public in Perth. The landscaped grounds of the weir, and
440-493: The water to cut a way around or under the dam. Sometimes the soil is sufficient to achieve these goals; however, other times it requires conditioning by adding support rocks which will bolster the weight of the dam and water. There are three different tests that can be done to determine the foundation's support strength: the Westergaard, Eulerian, and Lagrangian approaches. Once the foundation is suitable to build on, construction of
462-399: The weir requires monitoring and repairs and maintenance. On the original structure the central small building was used for aspects of monitoring the weir's internal status – it was rebuilt on the heightening of the dam, although it was no longer used for its original purpose. In 2009 two face wall entrance points were created on either side (north and south) of the face to facilitate access to
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#1732852228344484-576: Was railed on the above railway line. It opened in 1909 and closed in 1913. The old "Pumping Station Number 1" is now the C Y O'Connor Museum run by the National Trust . There is also the Kookaburra outdoor cinema , and the Department of Environment and Conservation has the Hills Forest activity centre, as well as a regional administrative office. Before rationalisation of its work force at this locality,
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