Rocla® Concrete Poles supplied 16 Duraspun® concrete power poles to Enerserve (a division of Energy Australia) to raise existing 132kV power lines along the southern part of the Westlink M7.
The existing lines, which cross over the M7 route, had to be raised to statutory clearances above the new M7 to allow for safe construction. The pre-stressed transmission poles ranged in size and from 35 metres to 40 metres with 80kN ultimate strength.
All poles were supplied in three sections and assembled on site using Rocla’s bolted jointing system. Most of the poles were mounted in 2-metre diameter, 6-metre deep piled footings, however some were installed in 4-metre square, 4-metre deep mass concrete footings for additional height. One set of poles, installed in soft soil adjacent to a creek bed, required additional depth and more than 100 cubic metres of mass concrete for each pole. These tall, high-strength “monopoles” offer an economical, attractive alternative to steel lattice towers in many situations.
The use of monopoles also allowed the two 132kV circuits to be raised separately, allowing one circuit to continue supplying customers. Michael Taylor of Enerserve said the Rocla® poles were specified for this project because of their fast lead time, lower cost and ease of construction, compared to steel lattice towers.