Ausgrid’s Merewether Sub transmission substation (STS), located at Coady Street, Hamilton South, is a major electricity supply point for a number of zone substations in the Newcastle and Lake Macquarie council areas. These substations are supplied at 33,000 volts by a series of underground cables from Merewether STS. Several of these cables are to be the subject of a replacement program that will be implemented over the next five years. Image above shows a similar cable project.
This replacement program is necessary as the original cables are reaching the end of their serviceable life. Timely replacement of these assets ensures a stable and secure electricity supply for our customers.
The large number of cables from Merewether STS, means that the available routes for the new cables are extremely limited. This is compounded by the presence of existing utility services such as town-water, storm water, sewer, telecommunications and gas lines beneath local streets.
To ensure the most cost-efficient delivery of the replacement programs, Ausgrid also seeks the shortest and most feasible route from Merewether STS to the cable connection point on the network. The cable sets to be replaced are direct buried. As some of these have been retired (supply to Adamstown, Charlestown, Dudley 33/11kV zone substations have been decommissioned), Ausgrid will re-use these corridors for installation of new ducts for the replacement cables.
The initial project will see the replacement of two cables that follow a route from Merewether STS to King Street Adamstown. The new cables will be installed within conduits in a common trench between Merewether STS and King Street, Adamstown. Spare conduits will also be installed for future replacement or to cater for increased electricity demand in the future, as required.
The common section of the route will be via Chatham Street, Fellowes Street, Lockyer Street and King Street. One cable set transitions to a new underground to overhead connection pole (UGOH) in King Street, near the entrance to the Merewether Golf Club. The second cable set will turn from King Street into Ella Street, Belmore Street and then to a UGOH in O’Connell Park, near the site of the old Adamstown zone substation.
Ausgrid is in the process of conducting an environmental assessment for this project. Tenders will be called for the trenching work in the near future. We anticipate that work will start in the first quarter of 2017.
An Environmental assessment is being prepared for the project in accordance with Part 5 of the Environmental Planning and Assessment Act 1979 and Clause 228 of the Environmental Planning and Assessment Regulation 2000. The assessment investigates the potential environmental impacts associated with the construction, operation and maintenance of the proposed infrastructure. It also recommends mitigation measures as required to ensure any impacts are at acceptable levels.
Ausgrid assesses the project for construction approval based on information contained in the assessment and any other relevant documents. Consultation with Newcastle Council and RMS has also been undertaken, as the trenching will impact on local streets.
As noted above, the large number of underground cables requiring dedicated routes from Merewether STS, coupled with other infrastructure (such as sewer, water, storm water, gas and telecommunications) already present beneath local roads means there are limited route options. Ausgrid has investigated a number of options and selected the one that provides the shortest possible distance, while avoiding existing service installations, and re-using old cable routes.
Ausgrid will keep the residents along the route informed of the project’s scope and timeframe, and provide advance notice where there may be impacts on property access during the trenching and conduit installation.
Like any construction work, the trenching component of the project would involve some noise and dust, and temporary traffic and parking disruptions, which we would work to mimimise as much as possible.
Construction activities will include:
- saw cut road surface and excavate trench, approximately 800mm to 1400mm wide, to lay conduits (PVC pipes) to house the new cables
- filling trench with a specialised concrete mix known as fluidised thermal backfill (FTB) and then temporarily resurfacing the trenched area
- at a later date, permanent restoration of the road surface*.
The initial conduit installation and resurfacing takes about three days outside each property depending on ground and weather conditions. Following completion of the trenching works, new cables will be fed into the conduits and pulled to their UGOH connection points.
*Permanent restoration of the trenched sections will follow soon after the conduit installation. The one joint bay (in Fellowes Street, near the Lockyer Street intersection) and a pulling pit in Ella Street, near Belmore Street intersection) will be permanently resurfaced after the cables are installed, joined and tested.