State engineering award for CATCON

South Eastern Times
Thursday 19/7/2007 Page: 1

THE Lake Bonney stage two Wind Farm construction team - CATCOM - has been recognised with a State engineering award for such innovative measures as providing 212 million litres of water for drought-affected livestock. The company has been awarded a 2007 Civil Contractors Federation (CCF) South Australian Earth Prize for its $19.8 million work along the Woakwine Range, which began midway through last year. They have been applauded for their excellence in civil construction as the judges took into account their project management, construction techniques and environmental management.

The company understood the design and construction of the reinforced concrete foundations for 53 wind turbine towers and the installation of 40km of connecting underground electrical and fibre optic cabling. As part of their contract, CATCON had to build access roads to each site as well as a hard stand area which could support the cranes to lift the 80 metre towers, 45 metre blades and nacelles (generators) into place. CATCON general manager, Steve Moreau said the annual CCF awards were supported by his company and he was pleased the project was honoured in this way.

According to Mr Moreau, CATCON had between 60 and 70 company personnel and sub-contractors on the windfarm tasks on any one day. He said the CCF award was also a fitting recognition for their efforts. Of the 53 turbines in Babcock and Brown's Lake Bonney stage two, 29 have already been erected. The erection project is on schedule, and is due for completion in February. The first operational stage of Babcock and Brown's Lake Bonney has 46 smaller turbines while the nearby Canunda Windfarm has 23 and is run by a separate company, International Power.

Babcock and Brown site representative, Glenn Leman has also commended CATCON on the standard of their work. Mr Leman said the company had completed the windfarm's civil engineering works in a timely fashion, When judging the annual awards, the CCF took into account site-related problems faced by CATCON. Although excellent in terms of wind generation capacity, the site contained swamp lands, a high water table, hard rock and low load-bearing capacity subsoil material.

In two places, the civil works contractors required major ground remediation four metres below the natural water table. CATCON faced a number of other challenges during the 10-month build process, which ended in April. Among these were the rigid deadlines for the farm's connection to the national electricity grid and the commitment to complete trench works within 24 hours to reduce landowner and farmer concerns about injuries to livestock.

CATCON also extended site roads, beyond contract requirements to divert concrete trucks from public roads. The company also took exceptional efforts to avoid environmental disruption by realigning access tracks, site exit locations and cable trenches to run along hill crests. These efforts avoided disruption of fertile farming lands and the visible scarring of the landscape along the Woakwine Range. The natural terrain consisted of steep inclines and marshy areas.

The remote location is more than 400 km from a capital city and this created long lead times in the delivery of equipment. From time to time, there were pump breakdowns and the weather conditions ranged from mid-winter to the height of summer. As the 53 tower bases and access roads were built over an area measuring 11km long and 1.5km wide, there were safety and logistics issues on a regular basis. Individual radios and global positioning systems were used by CATCON personnel and other contractors to good effect.

Adverse weather conditions had the potential to create concrete cold joints in the tower foundations. With large volumes concrete pours required during extremely hot and windy conditions at exposed locations, more than 20 pours consistently occurred in the hours before dawn. Each foundation base required 400 cubic metres of concrete and this equates to 80 trucks with a five tonne load. In some places, the batching plant was 10 km away from the base and so timing of truck movements was critical. Fire ban days also impacted on the construction project as ground clearing and welding were prohibited.

In the swamp lands, dewatering was undertaken by using large pumps and ground spears in the foundation impact zone. The water was then expelled through two holding tanks to settle and extract the accumulated silt. More than 221 million litres of clean water was collected and pumped to two fenced areas for the use of sheep and cattle from neighbouring farms. This solution provided much needed relief to the livestock during the drought while resolving CATCON'S technical design problems. CCF awarded the Adelaide-based company its award for projects with a value between $5 million and $20 million. The national CCF awards will be announced at a ceremony in Alice Springs in October.