Harold Weaver founded General Constructions (GC) on 11 November 1936. GC has evolved over the years through various restructures and name changes into the Interflow of today. The first GC project was the construction of the Northbridge sewer reticulation system in Sydney, where trenches were excavated by hand using picks and shovels. GC went on to build many sewer and water supply lines with projects throughout regional New South Wales, including Lismore, Grafton, Singleton, Cootamundra and West Wyalong.

The GC spirit was to always find a better way of doing things. An early example of this came when GC imported the first Barber-Greene trencher from the United States to Australia in 1938. This multiple-bucket and ladder-type production trencher was revolutionary and significantly reduced the cost of excavations.

The hard-clay geology of Nyngan, Narromine and Warren in western NSW allowed GC to venture into ‘Trenchless Technology’ for the first time using the pot-and-drive method for the excavation of deep sewer lines. A 3 feet (0.9 m) diameter shaft was bored using a drilling rig. Initially, two shafts were bored close to each other and two workers would hand dig to join the shafts at depth. Each man would then dig with pick and shovel in opposite directions towards the next shaft 12 feet (3.7 m) away and then continue to dig from shaft to shaft until the pipeline drive was completed.

To support its pipe laying capabilities, GC entered the dewatering business via a related entity, Vortec. In addition to carrying out dewatering on GC projects, Vortec also undertook dewatering on many sites throughout Australia, such as Sydney Airport’s North South runway, and international jobs in Papua New Guinea and Sri Lanka.

At the same time, GC was utilising trench boxes of its own design. These trench boxes were used for about ten years. Then, in the 1970s, GC started importing more advanced units from Germany. It was immediately evident that these new trench boxes would revolutionise trench-supporting techniques in Australia. Trenches which had previously taken a week to excavate were now being completed in a single day.

By the 1980s, GC had carved out its place in the municipal pipeline construction business. During this time it had gained extensive experience by performing work in many diverse locations and conditions, and had built up expertise in overcoming difficult challenges. The company began to focus on work that enabled it to exploit its competitive advantages – that is, more complex, larger jobs, and jobs that were further from home.

GC also began to gain exposure to techniques such as pipe jacking and sliplining, the early predecessors of the Trenchless Technologies we see today.

In 1991, GC was faced with a challenging proposition when the company was invited to bid on an open trench replacement of a failing 300 mm diameter sewer in the middle of a busy road. GC had recently become aware of a new Trenchless Technology called Expanda pipe, which was manufactured by Rib Loc, an Australian company based in Adelaide. GC and Rib Loc entered into an agreement and Expanda was used commercially for the first time in Australia. Following this, GC began using Expanda on other jobs and market acceptance grew.

In 1996, the Interflow name and brand was launched to coincide with the significant push into the exciting new area of trenchless pipeline renewal.

In a trenchless environment, the liner installation is only one part of the total pipe renewal solution. Other ancillary processes that are taken for granted today, such as lateral marking and cutting, end sealing and chemical grouting of junctions, were needed. Interflow found solutions for all of these functions either by developing or sourcing new products.

Over the last 75 years, General Constructions, and more recently Interflow, has always endeavoured to take a leading position by searching for state-of-the-art solutions to give that competitive edge. Since 2000, Interflow has introduced the ground-breaking technologies of Rotaloc and Ribline; expanded its product offering with pipe bursting, CIPP and access chamber rehabilitation; and developed its own system for lateral connection repair called the ‘Interfit’. In addition to the recently developed capabilities, Interflow continues to operate a Civil Constructions Division.

In the last decade, Interflow has been recognised with numerous awards for its products and projects from bodies such as Engineers Australia, CCF and the ASTT, culminating with the 2010 ISTT Project of the Year Award for the rehabilitation of the North Georges River Submain using a 2.4 m diameter Ribline structural liner.

A desire and willingness to find better and smarter solutions ultimately led Interflow into the Trenchless Technology sector, and to what has become the core of the current business. However, its success in this sector could not have been achieved without the skills developed during the long history in pipeline construction and the decades of experience attained by its key people.

Interflow is located in every mainland capital of Australia and also has an office in Auckland, New Zealand.

In 2011, Interflow remains at the forefront of the Trenchless Technology industry and is proud to once again be the Platinum Sponsor of this year’s No-Dig Down Under in Brisbane.