QLD – Dam Upgrade Activity in Queensland

There has been considerable dam upgrade activity in the last year in Queensland to remediate damage to dams and related major water assets from recent floods in 2013 and 2011.

Callide Dam

SunWater has completed repairs at Callide Dam to rectify damage to the dam’s gates sustained during a flood event in early 2013, caused by ex-Tropical Cyclone Oswald.  SunWater’s General Manager, Bulk Water and Irrigation Systems, Tom Vanderbyl said SunWater commenced repairs in October after post-flood inspections revealed two gates at the dam were damaged during the record flood.  “At the peak of the event, all six gates were opened, safely passing an estimated 173,000 megalitres of water per day,” he said.  “After the peak event, two of the dam’s six gates were damaged and were taken out of service while the damage was assessed.”  Mr. Vanderbyl said while the damage did not present an immediate safety hazard, SunWater prioritised the repairs to ensure both gates were returned to service as soon as possible.  “The rectification works involved repairs to the damaged gates and load testing to ensure all gates are in sound working order for the wet season.”  Callide Dam forms part of the Callide Valley Water Supply Scheme, storing and supplying up to 136,300 megalitres of raw water to Biloela, Callide Power Station, downstream irrigation customers and supplementing groundwater supplies through recharge within the Callide Valley.

Source: Sunwater media release 3 Dec 2013 www.sunwater.com.au

Paradise Dam

SunWater has commenced and completed additional interim repairs at Paradise Dam to further strengthen the dam for the wet season.  SunWater Chief Executive, Peter Boettcher said as part of Phase 3 investigations, SunWater conducted geotechnical drilling of the dam’s dissipator slab in October, and early findings suggest further strengthening of the dissipator slab is required.

“Paradise Dam is safe under normal conditions, however, the safety review has identified an issue with the dissipator and plans are being put in place to rectify this issue for the wet season,” Mr. Boettcher said.  “These additional interim repairs include shielding dissipator drains, constructing a capping slab over the dissipator and installing additional monitoring equipment on the dissipator slab.”

“SunWater staff continue to undertake regular surveillance of the dam and relevant stakeholders such as the Local Disaster Management Group and the Dam Safety Regulator are updated regularly about SunWater’s dam operating activities.”  Mr. Boettcher said the initial results of the safety review are being progressively peer reviewed by independent experts to provide SunWater and the Dam Safety Regulator with the best available information about the safety of the dam.

Source: Sunwater media release 23 Oct 2013 www.sunwater.com.au

Source: Department of Energy and Water Supply media release 18 Dec 2013

Borumba Dam

Seqwater has repaired scouring and erosion at the toe of Borumba Dam in readiness for the summer months.  The repairs were required as a result of damage caused by the January 2011 floods.   The toe, made of rock, sits in front of the dam wall and almost 3,600 tons of rock was brought in to provide extra protection against erosion.  Being so close to the waterway, Seqwater commissioned an environmental study before starting the works to ensure any possible impacts were minimised.

The January 2011 flood waters also deposited around 12,000 tonnes of gravel in the outlet channel downstream of the dam spillway. The gravel has been cleared to improve outflows from the dam.  The remediation works began in May after the wet season to reduce the risk of outflows over the ungated spillway during construction.  The timing of the project also allowed for the works to be finished before the Christmas holidays so there would be no impact on the popular camping spot downstream of the dam.

Despite several construction days lost to wet weather and challenges experienced while moving water from one section of the plunge pool to another to allow for access, the works were completed in less than five months.

Source: Seqwater media release 6 Nov 2013 www.seqwater.com.au

Mount Crosby Weir

Essential repairs to Mt Crosby Weir, a critical link in Brisbane and Ipswich’s water supply chain, were completed ahead of the 2013-14 summer wet season.  Mt Crosby Weir is one of the most important assets in South East Queensland’s bulk water supply system.  Water from the weir is pumped to the region’s largest water treatment plants, which supply most of Brisbane and Ipswich’s drinking water.

A diver sent in to inspect the weir and associated infrastructure following Ex-Tropical Cyclone Oswald in January 2013 discovered significant damage to the structure.

Work at the weir included hauling out a 22-tonne log, which was wedged in one of the two intake pipelines to the Mt Crosby East Bank Water Treatment Plant.  Once the log was removed, about 300 tonnes of rock and sediment that had accumulated in the intake pipeline had to be cleared away.

Numerous sections at the toe of the weir had been severely undermined and immediate action was taken to shore up the structure while a new concrete toe block was constructed to support the toe of the weir.  The repairs began in late June 2013 and, despite a number of challenges including the need to build a coffer dam to confine the flow of the Brisbane River to allow for a detailed inspection of the structure to be carried out, the works were completed in less than five months.

Originally built in 1926, the remediation works were the first major maintenance works at the weir since it was transferred to Seqwater in 2008.  The Mt Crosby project is part of an extensive program of works Seqwater is undertaking to prepare for the 2013-14 wet season.

Source: Seqwater media release 1 Nov 2013 www.seqwater.com.au

Collated by Michel Raymond from publicly available news releases.  Permission to publish obtained from Sunwater and Seqwater.