The disused Stapylton quarry is located in the suburbs of the Queensland Gold Coast. Gold Coast City Council, as part of the Northern Wastewater Strategy, has included the use of the quarry for storage and re-distribution of reclaimed water from the Beenleigh Water Reclamation Facility (WRF) to the downstream cane farmlands. A comprehensive EIS has been produced, which has strict water quality requirements for the quarry environs as well as the reservoir and outflow. This paper presents the background to the Northern Wastewater Strategy, the requirements for the Stapylton reservoir and the analysis performed for the detailed design of the embankment dam and the inlet bubble plume destratification system. The modelling of the destratification system was undertaken using the programme DYnamic REservoir Simulation Model (DYRESM) coupled with Computational Aquatic Ecosystems DYnamics Model (CAEDYM). The outcomes and implications of the modelling for the design and system operation including environmental monitoring are discussed.
Mark R. Sinclair & Richard J. Rodd
Over the last six years there have been ongoing significant developments in the design, fabrication and particularly of the corrosion protection details for high capacity ( >13,500kN MBL ) re-stressable ground anchors used to improve stability of gravity dams. These Australian based developments and the resultant specifications and details have now become the de-facto standards adopted.
The ANCOLD Register dams to have had this generation of cables installed have included; Ross River Dam, Lake Manchester Dam, Catagunya Dam, Tinaroo Falls Dam and Wellington Dam. These projects include the highest capacity permanent ground anchors installed to date worldwide. Some smaller capacity anchors installed into dams have also benefited from this technology.
The Recent Developments and Application of Large Ground Anchors for
Mark Locke and Scott Kindred
The Bulk Water Alliance (BWA) consisting of ACTEW and ACTEW-AGL, GHD, and John Holland / Abigroup, are delivering the Enlarged Cotter Dam project in Canberra, ACT. The greatly enlarged reservoir will require two central core rockfill saddle dams on a ridge adjacent to the main dam site. Construction of these two dams was completed in early 2011. The challenges of the site and the Alliance delivery model have provided opportunities for innovation in both use of materials and construction.
The dam foundations were variably weathered and fractured with some highly weathered seams extending below the cutoff trench foundation. The foundation was grouted effectively using GIN grouting and the entire cutoff trench was shotcreted to reduce the risk of piping of the dispersive core material.
The steep topography provided very limited sources of material suitable for a dam core. Potential contingency plans considered included bentonite enrichment of the low plasticity materials or a change to a concrete faced rockfill dam. The high cost of these options drove the decision to use the available residual soils from small gullies by selectively winning material with a higher fines content for use below full supply level. The lack of room on the ridge for stockpiling and conditioning of clays lead to trialling of a continuous mixer for mixing and conditioning the core which was found to be highly successful.
Filter materials were crushed sands and gravels produced from nearby commercial quarries. The materials and grading were generally high quality, with some challenges producing coarser filter materials by blending available aggregate products. A range of options were effectively adopted for placement of the filters including loader placement, trench boxes and spreading from a modified ejector dump truck.
Enlarged Cotter Dam Saddle Dams – Materials and Construction
Krey Price, Mike Harvey, Bob Mussetter, Stuart Trabant
The California Department of Water Resources, Division of Dam Safety (DWR-DSD), has determined that San Clemente Dam on the Carmel River in Monterey County, California, does not meet seismic safety standards. Several alternatives have been considered to decommission the dam and eliminate the hazard, including thickening of the 25-m-high, concrete arch structure, lowering the dam, and complete removal. At the present time, the upstream reservoir that had an original storage capacity of about 1.8 GL, is essentially filled with sediment. The 29-km reach of the Carmel River between the dam and the Pacific Ocean passes through urbanised areas within the upscale Carmel Valley; flooding and channel stability in these areas are significant concerns. The Carmel River also contains habitat for the endangered steelhead and red-legged frog that could be positively or negatively affected by the decommissioning.
After an extensive series of hydraulic and sediment transport modelling studies, two actions remain under consideration: (1) dam thickening, which will require reconstruction of the existing fish ladder and construction of an adjacent, 3-metre diameter sluice gate to prevent sediment build-up from blocking the ladder outlet, and (2) removal of the dam and rerouting the river into a tributary branch of the reservoir, which would isolate approximately 65 percent of the existing sediment deposits from future river flows and eliminate a significant fish-passage problem. Both options were modelled extensively in hydrologic, hydraulic, and sediment transport applications. Since available models do not adequately represent sediment dynamics at the sluice gate, a special sediment routing model was formulated to evaluate this aspect of Option 1. Option 2 is currently preferred by the resource agencies, since it would optimise endangered species habitat; however, this option would be three to four times more expensive than Option 1, and funding limitations may impact the alternative selection. Evaluation efforts are ongoing, along with approaches to address liability issues associated with the decommissioning actions for the privately owned facility, while optimising the benefits and costs of the selected action.
Modelling Studies to Design and Assess Decommissioning Actions for a Seismically Unsafe, Concrete Arch Dam
T. Mortimer, J. McNicol, P. Keefer, W. Ludlow
CS Energy’s Kogan Creek Coal Mine located in the Surat Basin in Queensland, services the 750MW coal fired, Kogan Creek Power Station. Strip mining generates large volumes of mine waste which is typically used to construct waste dumps. Recent work at the mine has focused on using mine waste to construct an ash storage facility to store ash that is piped over 5 km from the power station as a dense phase slurry. The use of mine waste to construct the ash storage facility provides significant cost and time savings, however a range of design, construction and operation issues needed to be addressed to operate a facility of this type.
This paper describes some of the key design, construction and operation considerations for the ash storage facility. Design considerations include pipeline transport through environmentally sensitive areas, addressing the stability of the embankment and the use of a partial LLDPE geomembrane lining system to reduce the risk of seepage from the storage. Construction considerations include post construction (pre ash deposition) floor treatment to reduce potential settlement. Operational considerations include ash slurry deposition, water management of the decant pond and progressive rehabilitation of the final landform.
2011 – Design, Construction and Operation of a Partially Lined, Ash Storage Facility Constructed from Mine Waste