A risky cure: Kembla Watertech & Sydney Water’s ASTT Award-winning project

Victoria Street in Darlinghurst is the second busiest road in Kings Cross, and runs parallel to Darlinghurst Road, Sydney’s Mecca of nightclubs, restaurants, hostels, and adult entertainment premises.

In 2009, as part of a larger work program, Sydney Water contracted Kembla Watertech to rehabilitate a sewer originally constructed over 100 years ago. Access chambers at the downstream and upstream ends of the project were both greater than 22 m in depth.

Project team

Highest risk oviform CIPP installation worldwide

Research and development then began to find a product that would meet WRc design requirements for relining this large diameter, very deep sewer main.

The design process concluded that a 29.5 mm wall thickness reinforced cured-in-place pipe (CIPP) liner was required to meet the WRc design standard commonly adopted for oviform shaped pipelines. This very thick liner was installed at this location to cater for the long term loads applied by the potentially high water table on the 23.5 m deep large diameter (990 x 660 mm) oviform sewer main.

Following careful consideration of the risks involved in the installation and curing of a liner of this thickness and at this depth, the lining methodology chosen was a pull-in and water cure. This installation was considered one of the highest risk oviform CIPP installations conducted worldwide.

A complex bypass

CIPP lining requires the host pipe to be dry for the duration of the installation and curing process.

Given the busy location of this project, sewer bypass arrangements were quite complex and involved installing a system of submersible pumps within the sewer system that would cater for the flow and deliver over 25 m of discharge head to an additional system of booster pumps on the surface.

Wet weather threatened the installation, but the bypass was installed 24 hours prior to the liner installation and a full days trial confirmed that the bypass well and truly catered for the incoming sewer flows. A total bypass distance of over 800 m for 2 x 6 inch hoses, powered by a system of submersible, 6 inch booster pumps and generators easily catered for the flows. Reticulation sewer flows in several other locations were also catered for by a system of submersible pumps and flows were diverted to a location downstream of the works.

Installation Procedure

To counter installation issues of wall thickness relative to diameter, a pull-in system was chosen. The fibreglass/felt/resin composite main liner is winched into position (structural component) and an additional calibration liner (low wall thickness) is inverted into the main liner. This creates intimate contact with the main liner before it is pressurised by a water column and heated in order to cure.

An internationally experienced pull-in liner technician was used for consultation purposes to ensure smooth operation on-site. Preliminary work involved conducting a trial recirculation in a ‘dummy’ liner on a 25 m deep oviform sewer near Kembla’s Strathfield yard.

Installation of the main liner commenced on 4 June 2012, using a 10 tonne capstan winch. This installation was considered high risk due to the weight of the liner installed and the depth of the sewer. The winch-in process was a time consuming and complex process, and took over twelve hours to complete successfully.

The second component of the work included installing the calibration liner, and effectively sealing the system so heated water can be introduced. Installation of the calibration liner concluded after approximately another 12 hours.

Heated water was then introduced to the system and continuously recirculated to initiate and control the curing process. This was carried out over a 24 hour period to ensure the high quality of the final product. Once the liner was cured, the ends were cut out and end treatments applied. The rehabilitated pipe was visually inspected and surveyed and the site was demobilised.

Total time on-site was seven days of continuous day and night shifts. This included wastewater bypass set-up, traffic control set-up, site establishment, installation of the liner, and site disestablishment.

A novel technology

During 2009, Kembla Watertech’s Project Team began research and development into a corrosion resistant fibreglass/felt/resin CIPP composite material. The research, done in conjunction with consultant/supplier Roders GmbH in Germany, was specifically designed to cater for the needs of large diameter, deep oviform sewer pipes within Sydney Water’s SewerFix Program.

During 2010, a series of trials and testing of materials were undertaken. Two yard trials were conducted at Kembla Watertech’s above ground testing facility in Strathfield using different material constructions to prove the viability of installation. A 900 x 600 mm steel oviform mould was purpose-built to accurately reflect site conditions. Post curing, the materials were retrieved and sent to HTS Pipe Consultants testing facility in the United States to determine a range of mechanical properties for the material.

After the results were received, the liner construction type was modified to reflect the mechanical property requirements of a 23.5 m deep large diameter oviform pipe. Testing was again conducted at an additional trial in Germany and witnessed by Kembla’s Design and Project Management Team.

Layer orientation of felt/fibreglass was optimised during this period to provide the client, Sydney Water, with a product that met the specific requirements for design purposes, as based on WRc guidelines for intact oviform pipes. After this, a range of laboratory prepared samples of different construction types were cured and the samples tested to determine specific mechanical properties.

Trial installations

In 2011, prior to Sydney Water’s final product approval, Sydney Water issued Kembla with two reinforced trial sites to validate installation in real conditions. This consisted of a 400 x 600 mm oviform stormwater pipe at Erskine Street, Sydney, and a 450 mm circular stormwater pipe at Reservoir Street, Surry Hills. Both trials were conducted successfully in November 2011.

Sydney Water’s product approval was granted, allowing Kembla to utilise a range of liner construction types on the deep oviform sewers in the Sydney Water contract, including Darlinghurst. Development of the product spanned three years.

Community benefits

This project involved working around the clock for a period of seven days. Working at night has the potential for high impact to residents and local stakeholders, however, community members were consulted early and in detail about the expected impacts of this project. As a result, no complaints were received by Sydney Water regarding noise. Kembla received two separate compliments, one from a local resident and the second from a building manager regarding the communication of the project and reduction of impacts to the community.

State-of-the-art silenced pumps and equipment were used during the project with pumps continually monitored and turned off whenever possible to reduce noise impacts.

The street experiences a high volume of traffic, and traffic was well-managed throughout the project. Pedestrian traffic was maintained throughout the area, despite the lengthy wastewater bypass. Local driveways were ramped to maintain access for local residents.

Occupational health safety benefits

As an additional safety precaution due to the depth of this project, the upstream length of sewer was isolated to aid in the event of an emergency evacuation. Additionally, a specialist traverse/communication rescue party was on standby at strategic positions within the sewer system.

Due to the complexities of working in a deep sewer, a communications system able to communicate kilometres below ground was used on this project.

The elimination of open excavations using a trenchless lining methodology, as opposed to open-cut or tunnelling techniques, represented a huge benefit to public safety and disruption.

Risk assessments and consultation with all affected authorities ensured adjacent infrastructure was protected along with the wellbeing of the workers.

A happy ending

The Victoria Street oviform sewer main was rehabilitated successfully, safely and with no community or environmental issues. Taking over three years in research and development to meet Sydney Water’s requirements and standards, the adopted reinforced CIPP lining system adequately met Sydney Water’s needs for this project and will be rolled-out for the remaining sewer mains issued for rehabilitation as part of this contract.