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Toowoomba Regional Council Tackles the Challenges of a Failing Common Effluent System Using SewerGEMS

Toowoomba Regional Council Tackles the Challenges of a Failing Common Effluent System Using SewerGEMS
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Toowoomba Regional Council Tackles the Challenges of a Failing Common Effluent System Using SewerGEMS - 1

CASE STUDY Project Summary Organization: Toowoomba Regional Council Location: Crows Nest, Queensland, Australia Project Objective: • Compare a conventional gravity system and a pressure sewer system, including the capital costs of the two options • Validate predicted flows to appropriately size a pressure sewer system Products used: SewerGEMS WaterGEMS Fast Facts • The study assessed the failing drainage system in the town of Crows Nest. • Using SewerGEMS TRC engineers were able to recommend the optimal system for future use. • Considerable capital cost savings and environmental benefits will be achieved if the conventional gravity system is implemented. ROI • Using SewerGEMS helped show that implementing a conventional gravity system could save as much as AUD 2 million (13 percent of capital costs). • SewerGEMS significantly reduced the model build time from days to a matter of hours, which allowed the council to spend additional time evaluating options. Toowoomba Regional Council Tackles the Challenges of a Failing Common Effluent System Using SewerGEMS Bentley Software Helps Council Compare Conventional Gravity and Pressure Sewer Systems to Recommend Optimal System In Queensland, Australia, in 2008, eight local governments were merged into one to form what is now the Toowoomba Regional Council (TRC). This council serves a population of approximately 120,000, and maintains water and wastewater networks totaling 3,200 kilometers in reticulation mains. TRC undertook a study in 2011 focusing on the township of Crows Nest as its flagship for assessing the existing infrastructure and the development of a future sewer system. The study was designed to identify whether a conventional gravity system would be a more cost-effective option than a pressure sewer system. Consideration of various conditions such as population densities, topographic constraints and the presence of the existing infrastructure were all major factors important to TRC. The need for improved water quality, better-performing sewer systems, and reduced capital costs were the primary objectives, but TRC also had to ensure regulatory requirements were met when choosing the most effective system. Using Bentley’s SewerGEMS for sanitary and combined sewer modeling and analysis, TRC engineers assessed that AUD 2 million could be saved building a conventional gravity system instead of a pressure sewer system. In a region that is facing catch-up challenges from recent significant flooding and other issues, if correct planning can be implemented via the use of software and some out-ofthe-box thinking, significant cost savings can be realized for the community. Local Government Amalgamation Challenges The amalgamation of the eight local governments posed a real challenge for the TRC, specifically how to assess the conditions of the varied sewage assets and networks in the region for the newly adopted township. The conditions of the existing systems varied from underperforming treatment plants to state-of-the-art activated sludge treatment plants. As this was a new assembly of townships, under the governance of the TRC, the wide and varied nature of the infrastructure triggered a comprehensive assessment of the existing assets and networks, as well as the creation of a new system to improve the quality of water, and reduce the effects of sewage overflows and poor effluent quality. Issues with the Existing System at Crows Nest The first system addressed was a regional system operated by TRC, known as the common effluent drainage (CED) system in the town of Crows Nest, Queensland. The CED system services a population of approximately 1,500 and consists of 24.5 kilometers of sewer mains with five pumping stations. This system was chosen because of its poor track record of effluent issues and wet weather overflows. Poor quality of effluent in one of the Crows Nests pumping stations. Located within the catchment of Toowoomba’s largest water supply reservoir, Cressbrook Dam, the CED system at Crows Nest relies on primary treatment at each property and a collection system delivering effluent to final treatment lagoons. This process relied heavily on the property owners to ensure the effluent produced was of acceptable quality. It was not uncommon to find effluent entering the systems or pumping stations at Crows Nest, which posed a real threat to water quality with an undesirable environmental impact. Another major issue with the CED Crows Nest scheme is regular sewage overflows during wet weather events. The study concluded that there was a compelling need to investigate an alternative to the existing sewer system. Evaluating a Conventional Gravity System SewerGEMS was selected to create a preliminary design for future conventional gravity and pressure sewer network

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Toowoomba Regional Council Tackles the Challenges of a Failing Common Effluent System Using SewerGEMS - 2

“SewerGEMS significantly reduced the model build time from days to a matter of hours, which has allowed the council to spend additional time evaluating alternative sewer options” – Toby Millikan, senior engineer, Toowoomba Regional Council Find out about Bentley at: www.bentley.com Contact Bentley 1-800-BENTLEY (1-800-236-8539) Outside the US +1 610-458-5000 Global Office Listings www.bentley.com/contact options. This software was selected as it was already used in-house, understood by TRC engineers, and very capable of conducting the analysis required. Esri’s ArcMap was used to review the...

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