International Power appointed GFWAust to carry out permeation grouting works around the cooling water pipes.

Pelican Point Power Station is a gas fired power station owned by International Power and located in Port Adelaide in South Australia. The cooling water pipes for the closed circuit water system for the steam turbines run from the site out to the Adelaide River.The fibre glass cooling water pipes are 2.8 and 2.2m and were laid in a trench 10m below the surface. The trench was backfilled around the pipes with a coarse angular gravel and the trench was then covered with fill. During the construction the trench was partly filled and a concrete plug placed  as a sloping berm against the gravel 

One of the water pipes developed a crack thought to be due to tidal changes and surges from passing vessels in the gravel. To repair the crack, the pipe was sealed internally with polyurethane and a proposal to grout the gravel was designed by SKM consulting engineers. GFWAust were appointed to carry out grouting works

Grout trials were carried out in a steel tank with plastic sides developed by the University of Adelaide to replicate the situation in the ground. The trials assisted in determining the most appropriate grout mix and the suitability of the installation and injection method.

Grout spears of 20mm diameter were installed down to the level of the pipes invert. The holes were predrilled with an auger with special attention to ensure there was no risk of hitting the pipes. 

A grout mix of flyash, bentonite and sulphate resistant cement was mixed in colloidal mixers and pumped with low pressure permeation grouting through the spears. Concern over grout travel along the trench into the river was monitored using a pH meter in boreholes in front of the grout zone.  

Due to the uncertainty of the grout pipe installation and grouting requirements GFWAust entered into an agreement with International Power to control costs and share the risk.