North Lismore Plateau Water Main HDD Complete

Posted 21 June 2016

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UEA Trenchless has completed the Horizontal Directional Drilling (HDD) work on the installation of dual water mains north of Lismore for a new development.

North Lismore Plateau (NLP) is a site approximately three kilometres northwest of Lismore’s CBD which has been identified for future growth. The proposed development site is expected to yield approximately 2,079 dwellings, and a new water main is required in order to service the new development.

UEA proposed an alternate method to install the 355mm and 280mm 1.5km pipelines by utilising HDD, which was accepted by council and a crew was mobilised in February 2016. UEA chose to use one of the two Ditchwitch AT3020s currently within the fleet of drill rigs.

By the start of May all pipe work had been completed with 1,589m of 280mm and 1,423m of 355mm installed using HDD methods. Council also requested that all house services on the other side of the road to the new main be installed with 125mm PE pipe to be utilised as a case pipe and a 40mm product pipe slipped through this pipe. All these case pipes were installed using a HDD rig totalling an additional 430m of underboring.

UEA Trenchless had to overcome several challenges encountered during the drilling process, some of which included:

  • Large extremely hard floating boulders – These boulders were difficult to drill through, especially with the surrounding soft ground conditions. Rather than changing drill heads and possibly damaging cutting teeth, UEA decided to dig up each rock and remove it before continuing to drill. Due to the shallow depth that the main is running at, dig ups were not an issue.
  • Reactive and soft ground conditions – At the start of the project, this combination of ground conditions and travelling at shallow depths meant that the surface level humping became an issue that could cause major damage. Utilising knowledge within the company, the methods and tooling was altered and boring longer shots of large diameter was possible without any damage to existing surface levels.
  • Traffic – UEA opted to use temporary traffic lights to shut down one lane. Traffic regulations restricted the lights to be turned off until 9:00 each morning due to local traffic going to school and work, therefore additional staff were required each morning to operate Stop/Go until the lights were able to be turned on.

Because of the knowledge and experience from UEA’s team, and a close working relationship with council, these issues were overcome with no effect to the project for the client. Now that the main has been installed by UEA’s HDD crew, a UEA civil crew will now link up all of the bores and install cross connections and all required fittings. The main will then be cleaned and tested in preparation for connections. The process will be managed closely with the client’s input to ensure minimal disruption. Once the new main is live, each house will have their service transferred to the new main and the old main will be decommissioned once complete.

For more details on this project or to see more of UEA’s horizontal directional drilling projects, contact the Trenchless team at trenchless@uea.com.au or call us on 02 9851 3000.