Primus Line has provided a trenchless sewer rehabilitation solution for two troublesome water mains in New South Wales.
The mains, located beneath a busy highway and dual rail track, were rehabilitated using DN 200 and DN 300 Primus Line® systems, with minimal impact on road and rail users.
New South Wales water utility Sydney Water Corporation (SWC) is responsible for providing safe drinking water and sanitation services to more than 5 million residents in Sydney, comprising almost 5,000 km of water and waste pipelines. It is one of the largest water utilities in the southern hemisphere and is recognised as taking an innovative approach to water management.
In January 2017, SWC approached Primus Line with a project to rehabilitate two critical trunk water mains: one at Pymble and the other at Penshurst Railway Station. The pipeline rehabilitation took place in June 2017.
The water main at Pymble consisted of a 47 m section of DN 225 cast iron concrete lined (CICL) pipe, while the Penshurst water main was a 77 m section of DN 300 CICL pipe. Both host pipes were transporting potable water, with an operating pressure of 10 bar.
The Pymble main runs below the Pacific Highway and, although it developed a leak in the 1980s, there was no technically and commercially viable rehabilitation method available to engineers at the time. With a large retailer planning to build an outlet at this location, and its water needs anticipated to put stress on the network, SWC had to find a solution.
At the Pymble location, the Pacific Highway is a main carriageway and often congested, meaning that any rehabilitation works had to be performed during the non-peak period between 9pm and 4am, and traditional dig and lay methods would take too long and be too disruptive to the community. The CICL pipes also included two difficult to navigate 45° bends.
The Penshurst main, which services a retail area and a public amenities block, was damaged more than two years ago. The location of the pipeline, below a twin track railway, and the presence of 4, v45° bends made finding a solution for the rehabilitation difficult.
The critical nature of the railway meant that the rehabilitation method needed to be performed at night and be as non-disruptive as possible. When considering solutions, SWC estimated that the trenchless method of horizontal directional drilling (HDD) would cost more than AU$600,000.
SWC decided the most effective solution for its leaky mains was to renew the lines with using the Primus Line® system. The liner has been used effectively in the past to rehabilitate pressure pipes, with the low wall thickness of 6 mm having a minimal impact on hydraulic capacity, in comparison to high density polyethylene (HDPE) pipes.
The liner comprises three layers: a polyethylene (PE) inner coating, a Kevlar® core and an abrasion-resistant PE outer layer that protects the core during installation. The system is AS/NZS 4020:2005 certified and was able to meet the key criteria of being able to pass though bends.
Primus Line provided 47 m of DN 200 PN 40 medium pressure Primus Liner and 77 m of DN 300 PN 25 medium pressure Primus Liner, as well as 4 connectors with AS 4087 PN 16 flanges for the project.
Pits were created at each end of the segment being rehabilitated. In both cases, the pipes were cleaned and CCTV inspection was performed, before the appropriate liner was pulled into place.
Compressed was then used to expand the liner and, at each end of the segment, the Primus Liner was attached to the original network using the connectors provided, and a fitting piece was used to complete the connection. Installation of the liner itself took only one night for each project.
The use of the Primus Line system on the existing infrastructure has extended the service life of the critical water mains by approximately 50 years. SWC was able to renew both pipes within one week, including performing CCTV inspection, pipe cleaning and liner installation.
Primus Line has estimated that savings in excess of 80 per cent can be realised using this method when compared to other rehabilitation methods.
This article was featured in the September edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
For more information visit the Primus Line website.
If you have project news you would like featured in Trenchless Australasia contact Managing Editor Nick Lovering at firstname.lastname@example.org