Ocean Outfall HDD for a Major Australian Telecommunications Company



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Introduction

Two major Australian telecommunications companies, along with Spark New Zealand, formed a joint venture partnership to deploy an undersea telecommunications cable system between New Zealand to Australia, known as the Tasman Global Access (TGA). The cable provides a 2,300 kilometre link between Raglan, in New Zealand, and the Northern Beaches, in Australia. The system will provide an alternative route for trans-Tasman communication traffic, significantly improving New Zealand’s international connectivity, as well as strengthening links into fast-growing Asian markets.

One of the telecommunications companies engaged UEA to construct a new access chamber in the Northern Beaches and install a 5-1/2 FH steel conduit from the access chamber 800 metres southeast to a location on the seabed off of one of the Northern Beaches. Works commenced in mid-July and were successfully completed on 14th August 2015. The TGA cable will be pulled through the conduit to the access chamber at a later date.

Project Scope

During the course of the project, UEA was tasked with the following work:

  • Erect a sound proofing compound around the work site. To sound proof the area, UEA erected a scaffold system 4 metres high, enclosed the entire site and installed a sound attenuation system over the scaffolding. The noise attenuation system was obtained from Echo Barriers and can provide anything up to 50% reduction of noise. (See before and after photos of site compound.)
  • Use UEA’s Vermeer D300 Horizontal Directional Drill Rig to complete the 800 metre ocean outfall bore installing a 5-1/2 FH drill pipe. This was left in situ as the telecom company’s required conduit.
  • Employ and manage a suitable qualified Diving Company to remove UEA’s tooling equipment from the ocean and install a termination piece on the end of the drill string. This was finished when the bore was complete for the company to link up to when installing their cable.
  • Construct a reinforced concrete pit within the street as the access chamber to pull the TGA cable into at a later date.

24 Hour Working

Due to the ground conditions (sand), UEA advised the telecommunications company at tender stage that in order to ensure a successful bore, UEA may have to drill 24 hours a day for five days. Due to this work schedule, local residents needed to be advised and notified suitably of the intended works, so UEA undertook the following:

  • Liaised with the local council
  • Produced a Community Liaison Plan
  • Placed an advertisement in the Manly Daily
  • Placed and manned an information stall on the corner of the street over one weekend
  • Posted information letters to all residents within 100 metres of the project
  • Invited and held an evening information session, with both UEA and the telecommunications company present, for the residents who were notified with letter drops

As all involved parties were properly advised of UEA’s plan in advance, UEA’s mobilisation to site was very smooth and there were no issues.

Techniques Used

Techniques on site included:

  • D300 HDD Rig to install Mild Steel Case using wash over method to assist with steer of drill pipe during installation and to eliminate the risk of fluid frac out on Pittwater Road
  • D300 HDD Rig to install 800m of 5-1/2 FH drill pipe
  • Steering Engineer employed to monitor pipe install and provide feedback to drill rig

The Works

Challenges

This bore presented a number of challenges from the onset, such as:

  • Closing off the street and erecting the compound
  • Drilling down the street and maintaining a safe distance from the existing previously installed conduit
  • Drilling from sand ground conditions entering into rock ground conditions, while maintaining steer and grade, to achieve the agreed exit point location (the most technical challenge)
Programme
  • The scaffold and sound attenuation system were erected in 3 days, fully enclosing the site
  • The steel case was installed in 2 days
  • 800 metres of 5-1/2 FH drill pipe was installed in 6 days and UEA managed to do this working 14 hour shifts, satisfying all concerned and avoiding the need to disturb residents at night
  • Termination pieces were installed, new pit was constructed, road was fully restored, site compound was removed, the plant and all equipment were fully de-mobilised in 12 days, which allowed for concrete curing times
Completion

From inception to completion, UEA successfully completed the project in 23 days.

Handover

The client was delighted with UEA’s capabilities and was very satisfied with the completed works and the accuracy of the installation. In addition, the site set up was professionally managed with very little impact on residents, and very few concerns or complaints were received.

Further information

For details about this project, or for information about UEA Trenchless’ accreditation status, phone 02 9851 3000 or email us for a quick response. To find out more about Trenchless Technology, visit our Technical Centre.