Journey times along Perth's southern corridor have been reduced with the completion of another phase in the A$355M upgrade of the Kwinana Freeway. Lawrie Tootell reports.
The design and build contractor on the Kwinana Freeway interchange and extension project linking the towns of Kwinana, Rockingham, Mandurah and the Western Australian capital Perth, had to win the tender twice. Opening to traffic on 23 June, five months ahead of the target date set by client Main Roads Western Australia, the 35km section was first awarded to Thiess, one of Australia's largest contractors and part of the German Hochtief Group in November 1999, valued at A$132M ($67M).
But 'the initial plans had a new rail line running on the outside of the southbound carriageway, ' says Theiss project manager, Tony Cariss. 'Opposition from residents and other interested parties called for significant revisions and that meant a new tender, which we also won.'
Some 15km of the northbound carriageway was shifted 15m westward to allow the rail tracks to be fitted between the two carriageways, as has been done on the Mitchell Freeway to the north of Perth. It also meant going back to the drawing board to incorporate the increased span widths for the bridges, interchanges and overpasses.
However, within two days of winning the tender, Thiess was setting up on site. A comprehensive GPS survey of the full length of the route reduced the number of surveys, with no need to clear the line of sight, and gave °15mm horizontal accuracy.
'That is close enough for carriageway alignments, but we still used traditional methods for the bridges and interchanges, ' says Cariss.
There are many reasons why the contract ran so smoothly, says Cariss. 'The client, consultants and suppliers were all extremely professional and joined a partnering agreement, so there was no pointing fingers at site meetings. Most issues were eliminated before they could develop into problems.'
A management system was introduced to ensure progress was maintained on schedule.
This divided the contract into five sections, each with its own superintendent who reported directly to the on-site headquarters, says Cariss. And with the client insisting that traffic continue to flow with as little obstruction as possible during construction, Thiess and traffic management consultant Shawmac incorporated the final works into traffic diversion, thus reducing unnecessary land clearance.
Over recent decades, Australians have become very environmentally conscious and no major road scheme is let without a full scale review of its impact on land use, fauna and flora.
With Freeway passing through built up residential areas and important wetlands, stringent controls were needed over working methods to ensure the least possible damage.
According to Thiess environmental manager Helen de Best:
'Unless a company can demonstrate a record of environmental management systems, it is unlikely to be included on any government select tender list for major works. Work initiated on the Freeway includes several kilometers of fencing to stop animals straying on to the road, and a number of concrete box tunnels under the carriageways to allow wombats, bandicoots, snakes and possums to swap sides without fear of being run down.'
At the southern end, the project runs parallel to the Peel Drain, a large waterway flowing southwards into the Peel Inlet at Mandurah. Runoff water from the Freeway and surrounding areas is channelled into specially built embayments planted with reed and other local species which act as natural filter beds before the water passes into the main waterway.'
One of the most challenging parts of the job, says de Best, was the collection by hand of more than 1,000kg of local plant seeds for sowing on the newly formed embankments and median strip. 'Once the winter rains start we will have an army of landscapers back to plant out the seeds.
Just short of 1,000 Balga or grass trees have also been relocated. Known locally as blackboys because of their jet black trunks, they grow less than 10mm a year and some specimens were approaching 2m in height.'
Theiss set up its own batching plant and casting yard just south of the half way mark, in the middle of the Freeway line. 'It was ideal. It required no additional land clearing, provided easy access for in-coming materials and finished products could be hauled to their final resting place without using public roads, ' says Cariss.
A critical point was that all concreting work had to be completed exactly to schedule, otherwise the carriageways could not be completed. The plant churned out concrete for the 122 precast beams for the 11 bridges - the largest spanning 48m and weighing 200t, and more than 650 precast segments for the three rail tunnels. A further 25,000m 3of concrete was required for the bridge decks, underpasses and associated structures.
Earthwork volumes of 3M. m 3and around 2Mt of sand and limestone for road base were imported from local pits running parallel to the Freeway. Hard rock came from quarries in the Darling ranges 35km east of the site. The weather was particularly kind to the muckshifters with not one day lost to rain.
There was no shortage of new ideas from the on-site engineers, one of which proved highly successful. Working closely with the Reinforced Earth Company, Theiss engineers and consultant Bruechle, Gilchrist & Evans, designed one piece, full height concrete panels for the retaining walls on the abutments of all 11 bridges.
'The system worked extremely well, ' says Cariss.
'The 8m high panels were propped in position with a few degrees of lean at the top. The area behind was then backfilled with sand and final vertical alignment of each panel adjusted during compaction. This system was an Australian first and there is no doubt it will become standard practice where foundation settlement is minimal, ' he adds.
The contract specifies that Thiess will remain responsible and guarantee carriageways and structures for seven years. A further landscaping guarantee that could run for 10 years if a 50% flora coverage is not achieved in three years is also part of the deal. Neither guarantee appears to weigh heavily on either Cariss or de Best.
With the Freeway fully operational, drivers can cover the 40km from the outskirts of Rockingham to the centre of Perth without encountering a single set of traffic lights. Long term traffic flow predictions increases with up to 85,000 vehicles per day using the link over the next 20 years. Residential land values are climbing steadily along the route. A number of new suburbs have already been established as city slickers fulfill the dream of 'going bush' while retaining all the social graces and comforts of the big smoke.
Client: Main Roads Western Australia Road design: Gutteridge, Haskins & Davey Structural design: Bruchle, Gilchrist & Evans Environmental consultant: ATA Environmental Landscaping: EPCAD Traffic management: Shawmac Geotechnical consultant: Coffey Geosciences Traffic signals: Lincolne Scott Australia Checking engineer: SMEC Australia Acoustic engineer: Hering Storer Acoustics