AVI-LIV Concrete Encasement

Client

Transpower


Description

This project Involved installing mass concrete foundations with upgraded capacity to resist planned increased line loads due to duplexing to 100 towers through varied terrain between Aviemore and Livingston in the North Otago region


Value

$3M


Key Dates

Commenced: October 2014
Completed: October 2015


Project Details

Works were carried out based upon designs produced by Spire Consulting Ltd, in accordance with the standard process followed by Transpower nationwide. Seven separate standard designs were applied across different sites in this asset. Concrete was delivered and placed within excavations at 400 legs at an average volume of 7m3 per leg to sites in varying geology and geography, with significant access challenges. 4WD access was developed to all sites for the use of subsequent stringing operations, but innovative concrete transport methodologies were developed to service particularly difficult sites. Site soils ranged from plastic clays to limestone requiring varied excavation techniques, and rock breaking at some locations. Site specific temporary restraint plans were prepared in house where design calculations required hold-down during works. The unique geology required novel solutions such as placement of soil anchors within the carriageway of a road to restrain a tower during excavation of two of its legs.


Project Outcomes

Soil-steel contact and resultant steel corrosion has been eliminated, maximising durability of the tower foundations, and removing the need to carry out regular excavation for the purpose of condition assessment. The uplift and bearing capacity of the foundations have been up rated to meet the requirements of the conductor upgrade carried out in 2016.


Performance

All works were carried out with an emphasis on maintaining a good relationship with landowners, and with high value placed on health and safety. Strong and effective relationships were forged with the local community, landowners and subcontractors. Despite a high number of hours worked, in trying weather conditions and steep slopes, no lost time or medical treatment injuries were recorded.