Water Corporation recently completed a major 43km pipeline to future-proof water supply to the town of Denmark, with Horizontal Directional Drilling techniques employed to help the project avoid disruption to three river and waterway crossing reserves.
Situated on Western Australia’s picturesque south coast, Denmark lies within one of the most climate-impacted regions anywhere in the world. Just two years ago the town was facing Stage 5 water restrictions and possible supplemental water carting after four of its driest years on record. Simply put, rainfall was no longer a reliable water source for the growing community.
In 2019, the WA Government announced plans for a $25 million, 43km pipeline connecting Denmark to the Lower Great Southern Towns Water Supply Scheme, which supplies the nearby port city of Albany and several smaller communities.
The project was designed to secure Denmark’s water supply into the future by ensuring it was no longer solely reliant on rainfall into the town’s largest dam, Quickup Dam.
Construction began in July 2020 and was carried out over a nine-month period. The 43km pipeline – consisting of approximately 7,200 lengths of 250mm PVC – was installed by Western Australian-based civil construction contractor, Georgiou Group.
Further work involving mechanical, electrical and instrumentation control, was completed by Australian-owned contractor Guidera O’Connor.
Construction was carried out under strict environmental and regulatory conditions, which included:
• Minimal clearing of native flora – less than 200 square meters allowed for the entire 43km pipeline
• Rare and threatened flora to be protected along the pipeline route
• No construction work to occur within river and waterway reserves
HDD allowed for minimal disruption
Working with Georgiou Group and design consultancy Jacobs Engineering, the project team was able to further reduce the total amount of clearing to just 144 square meters.
Furthermore, not a single tree was removed during construction thanks to careful route planning through precleared areas such as farms, road reserves and firebreaks.
A local ecologist was engaged to identify rare and threatened flora along the pipeline route. Identified flora was then barricaded for the duration of the construction, ensuring it remained undisturbed while the pipeline was installed.
The pipeline traversed three river and waterway crossing reserves. To avoid construction within each of these reserves, Horizontal Directional Drilling (HDD) specialist CD Drilling was engaged to carry out drill shots at each crossing.
HDD techniques allowed the pipeline to be installed seamlessly underneath waterways, with all construction activities occurring outside the reserve boundaries.
HDD works took place over a two-month period using a Vermeer D60x90 drill rig to drill a 400mm diameter hole underneath each river crossing.
The rig then pulled the 315mm diameter HDPE pipe through the hole, before pumping cement into the cavity to seal it in place. The largest drill shot length was around 193m beneath the Hay River.
Strong push for local companies and materials
The project was ultimately completed within its $25 million budget, with a strong focus on creating employment opportunities through the hiring of local workers and use of local materials and services.
To encourage local industry participation, businesses were invited to register for subcontracting opportunities prior to the tender process beginning.
This was announced via the project website, as well as through Water Corporation and Local Government social media channels. The approach proved incredibly successful, attracting interest from 63 local businesses and ultimately leading to over $6.2 million being invested in the local community.
As well as positive economic outcomes, the project also created employment opportunities for 13 Aboriginal people and three Aboriginal-owned businesses during construction.
Securing future water supply
With the project now complete and the pipeline ready for operation, Water Corporation will monitor water levels at Quickup Dam and assess when to bring the new pipe online. This is currently anticipated for around mid-2022.
In the long term, it is expected that Denmark will be supplied via the pipeline in winter and spring, alternating to Quickup Dam in summer and autumn when demand is higher.
The pipeline is capable of supplying Denmark with up to 2.2 million litres of water per day under gravity flow from Chorkerup tank (part of the LGSTWSS). Further capacity is available to increase this to four million litres per day as the town’s population grows in the future.
In Western Australia, the impacts of climate change on rainfall are stark. For Water Corporation, this means futureproofing projects like the Albany to Denmark Pipeline are going to be increasingly vital to ensuring communities and customers continue to enjoy a reliable supply of high-quality drinking water.