Location: Keith St Substation to Main St Substation, Palmerston North
Due to cable faults on some of the main power feeds into the Palmerston North CBD Blackley’s were requested to assist with the route design and installation of ducts for a new 33kV power supply.
Blackley’s were approached because of their cable installation experience and equipment and because they have achieved PowerCo’s ISN certification.
Blackley’s completed a desktop study of the proposed route and then verified this route using service mark outs and by pot holeing the existing services in advance of the actual excavation.
The Main St length of the project is approximately 2000m and besides being a busy city street it is also a State Highway and therefore a main entry point to the city. The balance of the project is approximately 900m in a grassed area behind the Main St cemetery. Included in the work are 3 major road crossings, 4 minor road crossings and a crossing of the four laned Main St as well.
The project requires 3 x 160mm ducts to be installed in trefoil with a 20mm duct in the centre of the bundle and a 32mm duct attached to the outside. The duct is bedded in compacted thermal sand and the balance of the profile is backfilled with AP65 and M4, AP40 aggregate installed in compacted layers.
The desktop investigation revealed that there were very few existing services running down the road in the parking area between the lane edge line and the kerb & channel so a decision was made to use a chain trencher where possible to speed up the installation process. Excavators were used for road crossings or where existing services were too close together or where additional depth was required to provide the necessary clearances from existing services.
Progress to date has been good with the Main St section complete other than laying the cable into the substation. The Main St road crossing and approximately 50% of the section behind the Cemetery is also complete.
1000m of the duct has had cable installed so the project is on target for completion in early December.