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Water Corporation - Groundwater Replenishment Trial
The Water Corporation, Department of Health (DoH), Department of Water (DoW) and Department of Environment and Conservation (DEC) have a common intention to investigate whether water sourced from advanced treatment of wastewater can provide a potential future public drinking water source for Perth, by way of groundwater replenishment. An Interagency Working Group has been set up to progress a Groundwater Replenishment Trial (GWRT), allowing the Water Corporation to assess the technical feasibility and assist all parties to consider and address environmental, social, and health issues relevant to groundwater replenishment. The GWRT will also facilitate several hydrogeological research projects to assist in informing these objectives.
The proposed GWRT will be located at the Water Corporation’s Beenyup site at Craigie, in the northern suburbs of Perth. It will treat approximately 1.5GL/yr (5ML/d) of secondary treated wastewater from Beenyup Wastewater Treatment Plant by membrane filtration, reverse osmosis and ultra violet treatment and inject this highly treated water into the Leederville aquifer at approximately 120m – 220m depth. The GWRT will operate for a period of four years; commencing with groundwater monitoring in 2008 to determine background groundwater quality and injection of high quality water in 2009. Injection will be carried out and monitored for a period of three years.
Rockwater was engaged to carry out a Site Evaluation which described the stratigraphy, lithology and hydrogeology of the site determined from a cored borehole, correlation with two nearby bores, and seismic surveying. A local groundwater flow and solute transport model was developed to evaluate the travel distance for injectant during the planned three year operation of the GWRT.
St. Hilda’s Anglican School for Girls - Geothermal Water Supply Project
St. Hilda’s existing 25 m swimming pool is to be decommissioned and a new 50 m pool constructed on the property. As part of the re-development plan the School is investigating the feasibility of obtaining a suitable geothermal water supply to provide pool heating and possibly heating for a 150-bed boarding house.
If a geothermal water supply can be obtained, the intention is to pump warm groundwater from a deep production bore in the Yarragadee aquifer, pass the water through heat exchange units to warm the pool and accommodation unit, and then to inject the cooled water back into a shallower section of the aquifer. This would result in no net loss of water from the aquifer and provide a source of heating with negligible carbon-dioxide emissions.
Edith Cowan University - Hydrothermal Air Conditioning Project
Edith Cowan University pumps groundwater from two production bores which feed heat exchangers used to provide thermal energy for an air-conditioning system at its Joondalup Campus. After the water has passed through the heat exchangers, it is pumped back into the aquifer via two injected bores.
Rockwater conducted a review of the injection system, including sampling of the injection water for chemical analysis and an assessment of the options that could be used prevent subsequent clogging of the screens. A sealed system, minimising the possibility for air-entrainment and the oxidation of dissolved iron, and new pipes able to withstand the attendant high collapse pressures, were proposed. An improved design for the replacement injection bores, including the use of longer screens with a larger diameter and aperture size than previously used, was also recommended.
Prior to drilling of the new injection bores, one of the existing production bores was test-pumped in order to determine its sustainable yield, provide aquifer parameters for groundwater modelling, and assess the radius of influence of pumping and therefore assist in siting of the new injection bores.
Two new injection bores was constructed and equipped. Thereafter, a number of pumping tests were performed to assess the capacity of the new injection bores operating individually and then together as an operational configuration.
Water Corporation - Jandakot ASR
The Water Corporation has identified aquifer storage and recovery (ASR) as a potentially significant operating strategy for water distribution and treatment within the Perth Metropolitan Scheme. It has potential benefits with regard to environmental and contingency issues such as drought management, improvement of water quality, groundwater banking, maintenance of groundwater levels and protection of groundwater-dependent vegetation. A large-scale ASR trial was therefore established at Jandakot to determine the feasibility of injecting large quantities of potable water into Perth's deep, confined aquifer systems for storage and re-use.
Rockwater was invited to provide hydrogeological consultancy to this project, based on their previous experience in the field. A preliminary feasibility study was conducted and the Jandakot site was selected for the initial trial: factors such as bore construction, aquifer characteristics and the availability of a suitable injection source were assessed. Two initial trials were conducted with over 200,000 kL of water injected and recovered from the Leederville aquifer at the site. The technique was shown to be feasible, with appropriate action taken for the prevention and control of clogging, and the project was subsequently upgraded to an operational trial. A further 675,000 kL of potable water has been injected into the Leederville aquifer, and is currently being recovered for use within the Perth Metropolitan Scheme. Rockwater remains the principal hydrogeological consultant to this major research project, and is responsible for design and management of ongoing monitoring, data collation and assessment, technical advice and consultancy, and reporting.
Town of Claremont Aquatic Centre
Following the success of the Christchurch geothermal heating project, other swimming centres have been keen to implement similar systems. The Town of Claremont Aquatic centre was one of the first to engage Rockwater to conduct a feasibility study to determine site suitability. The feasibility study showed geothermal water should be available in the Yarragadee aquifer and the council resolved to install a geothermal-based heating system as part of its upgrade. Rockwater was subsequently awarded the contract for hydrogeological services including bore design, preparation of tenders, management of the production and injection bore construction, and reporting to the Department of Environment. A production bore was successfully installed to 845 m depth and yields water supplies of 43.2oC to the heat exchanger. The cooled water is then returned to the aquifer via a 605 m deep injection bore resulting in no net loss of groundwater from the system; recirculation is of cool water to the deep bore is prevented by separation from the lower aquifer by impermeable shale layers. The Sustainable Energy Development Office, of the Government of Western Australia reported "The local council have been more than pleased with their choice, with operating costs totalling just $2,500 for the first half of 2004. Being more energy efficient, the geothermal system also results in lower greenhouse gas emissions. It is estimated that the system will save 8,300 tonnes of greenhouse gas emissions over a 25-year period."
Christ Church Grammar School
Rockwater was principal hydrogeological consultant to the Christ Church Grammar School geothermal heating project: an innovative project utilising geothermal bore water in a heat exchange unit to heat the school swimming pool. Economic feasibility studies showed that despite higher initial capital costs, the use of geothermal groundwater has lower annual energy and maintenance costs, and over a life cycle of 25 years is about 15% cheaper than conventional (fossil-fuel) heating options. It has the environmental advantages of causing no net loss of groundwater, since the water is reinjected into the aquifer once the heat has been extracted, and saving about 5,000 tonnes of greenhouse gas emission over a 25 year life. Following a feasibility study to determine whether geothermal groundwater was accessible at the site, bore construction designs were compiled and tendered to appropriate drilling contractors. Rockwater supervised all drilling and construction for the deep production and injection bores and provided the down-hole geophysical and temperature logging services which identified the appropriate aquifer intervals for extraction and reinjection. The system has now been operating successfully for two years, with geothermal groundwater (41.6oC) from the Yarragadee aquifer pumped from a 738 m deep production bore, and returned into a higher level of the Yarragadee aquifer, hydraulically separated from the lower level, via a 609 m deep injection bore. The project has won both government and industry recognition for its environmental sustainability and engineering excellence.
Mines and Resources Australia - White Foil Project
Mines and Resources Australia utilised injection bores completed in a local palaeochannel aquifer at its White Foil Project to dispose of groundwater extracted during mine dewatering operations. Several problems were encountered during these operations and Rockwater was commissioned to investigate the re-injection programme and make recommendations for future operation and development of the scheme. It was found that clogging of the bores by suspended solids was the likely cause of reduced injection capacity and recommendations were made for filtration of the injected water and regular re-development of the injection bores.
Following an increase in the mines dewatering requirements, Rockwater was commissioned to conduct a more detailed hydrogeological investigation to define the palaeochannel characteristics and identify optimum locations for additional injection bores. A drilling programme was undertaken and three additional injection bores were installed under the supervision of Rockwater personnel. The results from the drilling programme were assessed and reported, providing additional information on the palaeochannel aquifer and a quantitative assessment of the injection capacity of the borefield. Further recommendations were made for pretreatment of injected water and the establishment of an ongoing bore re-development programme for the control of clogging.
Australian Mines Ltd - Blair Nickel Project
Rockwater was contracted to investigate the feasibility of disposing of water accumulated in a box cut and underground workings at Blair Nickel Mine by injection into a local palaeochannel aquifer. It was estimated that a total of 120,000m3 of water had accumulated in the mine during a period of shut-down and that injection at rates of up to 800 m3/d would be required over a period of five months to dispose of this water. Pumping and injection tests were conducted on an existing production bore to assess the ability of the aquifer and the bore to accept the required injection rates. It was found that the rates required might be sustained in the one bore as long as clogging control procedures were implemented. A second bore was subsequently drilled and tested to provide additional capacity and backup. Rockwater was responsible for the preliminary aquifer review, supervision of the pumping and injection tests, data collation and assessment, providing technical advice and recommendations for operations, preparation of a monitoring programme, and reporting to the regulatory authorities.
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