Mt Mercer Wind Farm Feeder Line

Project Brief.

The 21.5km Mt Mercer Feeder line connects the Mt Mercer windfarm collection station to the local substation. FSG were engaged to provide an efficient power pole foundation design and a cost effective method of validating ground conditions across the entire length of the feeder line. FSG adopted a risk based approach to determine the required geotechnical site investigation at each pole location along the alignment.

Site Geology and Challenges.

The site geology along the 21.5km alignment generally comprises stiff clay of varying thickness overlying high strength basalt.

The greatest challenge associated with the project was to provide a realistic power pole foundation design across the entire length of the feeder line and a cost effective method of verifying ground conditions across the 21.5km alignment.

Scope of work.

The project comprises more than 160 poles, which are simply placed in an augered or drilled hole and backfilled with concrete. The pole design is governed by the lateral loads on the poles. FSG’s initial foundation design was based on limited geotechnical information along the alignment. FSG’s design approach was targeted towards systems which were simple, robust and well suited to an environment with restricted access.

Our approach to verifying ground conditions along the alignment also focussed on low cost, high turnover methods such as DCP’s and test pits. An FSG engineer inducted the Pole installation contractor in the site investigation methods to ensure consistent data quality.

During the design phase, FSG engineers liaised closely with the client to optimize the pole selection and the foundation design. Particular emphasis was placed on using the limited available geotechnical data to generate a robust preliminary design which limited the amount of drilling in high strength basalt.

Conclusion.

FSG adopted a risk based, low cost geotechnical site investigation specifically tailored to the prevailing ground conditions and access constraints.

As a result of this approach FSG were able to produce an efficient, robust pole foundation design. Frequent liaison with the client allowed pole selection to be optimized to reduce both risk and cost.