Wyaralong Dam

Wyaralong Dam
The dam wall, from the viewing platform.
Location of the Wyaralong Dam inQueensland
Country	Australia
Location	South EastQueensland
Coordinates	27°54′33″S152°52′52″E
Purpose	Potablewater supply
Status	Operational
Construction began	2010(2010)
Opening date	2011(2011)
Construction cost	A$380 million
Operator(s)	SEQ Water
Dam and spillways
Type of dam	Gravity dam
Impounds	Teviot Brook
Height	48 m (157 ft)
Length	490 m (1,610 ft)
Dam volume	218,300×10^3m3(7,710×10^6cu ft)
Spillway type	Uncontrolled
Reservoir
Total capacity	102,883 ML (22,631×10^6imp gal; 27,179×10^6US gal)
Catchment area	546 km2(211 sq mi)
Surface area	1,230 ha (3,000 acres)
Website www.seqwater.com.au

TheWyaralong Damis amass concretegravitydamwith anun-gated spillwayacross theTeviot Brookthat is located in theSouth Eastregion ofQueensland,Australia.The main purpose of the dam is forsupplyofpotable waterfor theScenic Rimregion.The dam was initiated by theQueensland Governmentin 2006 as a result of the prolongedMillennium droughtwhich saw the catchment areas of South East Queensland's dams receive record low rain. It was completed in 2011.

Location and features

The dam is located approximately 14 kilometres (8.7 mi) north-west ofBeaudesert.The dam wall itself is split between thelocalitiesofWyaralongandAllenview,but the bulk of impounded water is within Wyaralong.

The Wyaralong Dam was completed prior to the2010–2011 Queensland floods.On January 11, during the flood period, the Mayors of bothLogan CityandScenic Rimsaid they believed thatLoganhad been spared a great deal of flood damage because of the dam.

The concrete dam structure is 48 metres (157 ft) high and 463.60 metres (1,521.0 ft) long.The dam wall is constructed from a medium cementitious mix roller compacted concrete, which is a zero-slump concrete that is placed in 300mm thick lifts and compacted with vibratory compactors.The foundation is a sub horizontal dipping blocky sandstone. The dam is built with a 130-metre (430 ft) wide uncontrolled central primary spillway and an uncontrolled left bank secondary spillway which commences discharging at the 1:100 year flood level. The dam cross section is rather squat in order to provide sufficient resistance against potential sliding along foundation bedding planes. The 218,300-thousand-cubic-metre (7,710×10^⁶cu ft) dam wall holds back the 103,000-megalitre (23×10^⁹imp gal; 27×10^⁹US gal) reservoir when at full capacity. From acatchment areaof 546 square kilometres (211 sq mi) that includes much of the western portion of theMcPherson Range,the dam creates a reservoir with a surface area of 1,230 hectares (3,000 acres). Teviot Brook and the surrounding land is a recognised Aboriginal Pathway with significant cultural heritage values.

The dam is managed bySEQ Wateras part of awater securityproject in the South East Queensland region, known as theSouth East Queensland Water Grid.The outlet is on the right bank and is capable of abstracting water from any level of the reservoir by the use of baulks. The outlet includes an innovative and operationally complex bidirectional fish lift, which uses a single hopper to transport fish in both upstream and downstream directions.

Conception

The site was identified in a 1990 study,Water Supply Sources in South-East Queensland,as a future source of water supply for the South East Queensland region. In this report, the site of Wyaralong Dam was ranked 13th out of 15 studied possible dam locations in the region. A location on theAlbert RiveratGlendower,also nearBeaudesert,was the preferred location and the government subsequently bought back all the land required for theGlendower Dam.A new dam was not expected to be required until 2060 or later and Glendower Dam remained the preferred dam site, the land already fully government owned.Properties previously acquired by the government are progressively being sold to private buyers.

In October 2005, in advance of thestate election,the Queensland government announced Wyaralong Dam as the new preferred option, even after recent studies into possible dam locations found a location upstream on theLogan Riverto be a more reliable option. After a series of studies, a Senate Inquiry and much contested information,Federal Environment MinisterPeter Garrettgranted approval for the Wyaralong Dam in November 2008.

The dam is a storage and regulation facility. It does not discharge directly into the piped reticulation network, but rather discharges back into the natural drainage network of creeks and brooks. Water released from the dam flows downstream along Teviot Brook toCedar Grove Weir,where it is diverted for treatment and use in the piped network.

Construction

Picnic area and boat ramp

The construction was tendered under an alliance contract. In this type of contract risks and rewards are shared by all the proponents including designers constructors and the owner. Queensland Dam Consortium won the tender for the dam's construction, and the Alliance was formed from their members which included Macmahon Construction as the lead contractor, Hydro Tasmania,Snowy Mountains Engineering Corporation,Paul Rizzo and Associates (USA), ASI Contractors (USA) and Queensland Water Infrastructure the special purpose vehicle created by the Queensland Government owner to deliver the project.The Alliance contract for dam construction was for a little overA$100 million. However it was widely reported that the building costs for the dam would totalA$333 million.The latter figure includes the cost of the Bromelton Offpeak Storage Project, Cedar Grove Weir and the reconstruction of a length of the Boonah to Beaudesert Road.

Work on access roads began in early 2009 and construction of the dam wall began in early 2010.The diversion channel was plugged on 17 December 2010, allowing the dam to begin to fill.The dam site was opened to the public on 3 June 2011.The 12 kilometres (7.5 mi) of new road betweenBoonahand Beaudesert were constructed under a separate contract byFulton Hogan.

The dam costA$380 million to construct, including purchasing farmland flooded by the dam reservoir.

Treatment

By late 2012 the dam still had not been connected to theSEQ Water Gridbecause it contains water so mineralised it is cheaper to produce desalinated water than to treat it.The Wyaralong water treatment plant is expected to costA$235 million to construct.Funding for the plant was planned for the 2014/15 financial year. In 2017 SEQ Water external relations manager Mike Foster stated the Wyaralong Water Treatment Plant wouldn't be necessary until "2030 or beyond".

January 2011 floods

Main article:2010–2011 Queensland floods

As a result of rainfall during the2010–2011 Queensland floodsthe dam filled to 100% capacity, just 25 days after the wall was plugged to hold water, but before its completion.By 10 January during the flood period, the dam held 83,133 megalitres (18,287×10^⁶imp gal; 21,961×10^⁶US gal), 80.7 per cent of its 103,000 megalitres (23×10^⁹imp gal; 27×10^⁹US gal) capacity. Parts of the dam were still under construction, but its wall was plugged to hold water on 17 December 2010.On 11 January the dam filled and began to overtop at 9:27am, Following the overtopping, in the first 24 hours over 17,300 megalitres (3,800×10^⁶imp gal; 4,600×10^⁶US gal) of water flowed over the primary spillway and entered the Logan River at Cedar Grove.

See also

• List of dams in Queensland

External links

• International Water Power and Dam Construction Magazine