Gosford City Council’s jurisdiction is diverse, with the Pacific Ocean defining the eastern boundary, the vast Hawkesbury River to the south, the Judge Dowling Ranges forming part of the western boundary, while to the north lie the Wyong and Cessnock Shires.
Every day, Gosford City Council supplies around 33 million litres of water to approximately 60,000 properties through 1,000 km of water mains.
The council’s water supply and wastewater system is made up of a complex array of dams, water and sewage treatment plants, pumping stations and connecting pipelines. It is integrated across the region through water connections to supply points from the Wyong and Hunter regions.
A trenchless backbone
The council says that it is increasingly looking to use Trenchless Technology wherever possible as the backbone of its ongoing and targeted asset upgrade programs.
Manager Asset Management and Planning Pam McCann said “Currently, we rely on Trenchless Technology for the CCTV inspection of the area’s sewer mains and also various sewer rehabilitation needs – especially the relining of sewer mains.”
The council is currently working with Interflow to deliver its ongoing sewer main rehabilitation program. Over the past year, the work has relied on trenchless pipeline renewal technology to reline approximately:
- 2.5 km of 150 mm, 225 mm and 300 mm diameter sewer mains, and
- 1.5 km of 375 mm, 450 mm, 525 mm and 60 mm diameter sewer mains.
The council plans further use of expert contractors for the ongoing CCTV inspection of its water and wastewater networks.
Asset management programs
The council’s ageing assets have prompted more regular replacement and repairs in recent years.
“We are continually increasing these upgrade works as the average age of the area’s water and sewer system is between 30–50 years old,” Ms McCann said.
A number of these works involve the use of Trenchless Technology.
Water
Spending close to $A3 million each year, the council seeks to improve the region’s water supply system by replacing aged and damaged water pipes and valves.
In the past year, nearly 3 km of water pipes have been replaced. This work reduces the risk of main breaks and helps maintain good quality drinking water.
Wastewater
Condition assessments have been, and are continuing to be, carried out on approximately 700 manholes throughout the wastewater system.
Manholes, where conditions are very poor, have been identified and a program for their rehabilitation has commenced. The council plans to expand this program to encompass the entire sewer network.
Through its ongoing CCTV inspection program, the council continues to identify sewer mains that have structural defects or other defects that allow infiltration of ground water. Close to $A1 million is spent each year to rehabilitate these mains via relining.
Asset Planning Engineer Gary Alford said “Whether trenchless pipeline renewal technology is used as part of our current sewer rehabilitation works depends on the type and number of defects identified via our CCTV inspections.
“Identifying the sewer mains that need high-priority rehabilitation is always a challenge.
“However, we are confident that as our CCTV inspection program intensifies, the identification of those mains needing renewal will be more accurate and detailed.”
The council is also currently investing around $A5 million each year to deliver an extensive program to identify sewage pump stations needing high-priority civil, mechanical and electrical renewal, or rehabilitation.
As part of the program, the council is critically assessing the associated downstream rising mains. Many rising mains comprise asbestos cement material and in some cases samples are being taken for X-Ray type analysis to assess remaining asset life.
This program ensures the region’s ageing pump stations continue operating to a standard that:
- Complies with the environmental protection guidelines set by the New South Wales Department of Environment, Climate Change and Water
- Improves the performance and management of the council’s wastewater network
- Protects the community, environment and nearby waterways against sewage overflows, and
- Does not pose a safety risk for the council’s operations staff or the community.
To compliment the council’s rehabilitation works, an asset management database, HANSEN, is currently being implemented to assist with the storing of knowledge on individual water and sewer assets. Information will include critical data such as condition assessments, age, materials and work orders.
This program will provide a general appreciation of assets and their position in their lifecycle. Physical condition assessments will eventually supersede this assessment process.
Mardi-Mangrove Link Project
Gosford City Council Technical Manager for the Mardi-Mangrove Link Project Joe Weston has been working for the council for almost 13 years.
Since June 2009, Mr Weston has been working on the design and construction of the Mardi-Mangrove Link Project.
The $A120 million project will link the Wyong River and Ourimbah Creek to the Mangrove Creek Dam via the Mardi Dam. The council said it is the largest water infrastructure project undertaken on the Central Coast since the mid-1980s and is due for completion in mid-2011.
Mr Weston said “This opportunity is rare in local government and I am privileged to be involved in some unique experiences and to be working with a team of very dedicated and capable people from both council and the private industry.”
One challenge with the Mardi-Mangrove Link Project is that the pipe used is a larger diameter than the council normally uses.
“This is quite challenging as we frequently need to work outside normal standards and develop innovative solutions.
“One example is where we recently used horizontal directional drilling (HDD) technology to install a 260 m section of pipe under Wyong River. A pipe bridge was not feasible because the river was too wide and there were environmental concerns,” Mr Weston said.
This is the first time a pipe this size, length and pressure rating has been installed in Australia using HDD. Mr Weston said he enjoyed the fact that working on such a large and complex project also means there is a greater range of products available and different suppliers to work with.
“This has challenged my knowledge and encouraged me to learn about products and specifications in much greater detail,” Mr Weston said.
Challenges
Drought
Around 2007, the region was in the grip of the worst drought on record. More than 15 years of below average rainfall and stream flows had pushed the Central Coast’s water supply to its limits.
Mr Watson said that the council is still focussed on ensuring the Central Coast recovers from the recent drought and in partnership with Wyong Shire Council is working to implement WaterPlan 2050 – a strategy to secure and sustain the region’s water supply system over the next 40 years. This plan includes:
- Further enhancing the current water supply system
- Continuing to use water as efficiently as possible, and
- Developing additional future sources of water.
The Mardi-Mangrove Link Project is a part of this initiative.
Discoloured water
Discoloured water has also been a battle for the council. At the end of 2009, the council completed its two-year, multi-million dollar drink water quality program – Water Quality 2010.
The program is aimed to enhance the water treatment process, clean and protect the distribution system against contamination and introduce additional management systems to safeguard drinking water quality.
Wastewater
Gosford City Council’s wastewater network services nearly 65,000 properties and includes over 1,500 km of sewer pipes, around 180 sewage pump stations and two sewage treatment plants.
The council is currently working to deliver improved sewer services to four remaining areas prioritised under the State Government’s Priority Sewerage Program and Country Towns Water Supply and Sewerage Program.
This is to alleviate public-health and environmental risks posed by on-site sewage management systems operating at properties in these towns.
