AIRPIPE PTY LTD has recently successfully carried out a sliplining project for Griffith City Council. Airpipe was contracted to undertake the renovation of more than 900 metres of a 600-mm diameter sewerage rising main located adjacent to the city’s main shopping district. The main took waste from Yoogali and Collina districts and the industrial area.

Griffith is home to more than 23,000 people and has become the major service centre for a vast part of south-western New South Wales. Griffith was designed by Walter Burley Griffin, the architect of Canberra, and named after Sir Arthur Griffith, the first Minister for Public Works in NSW.

The existing sewer main, located along Twigg Road, between Jondaryan Avenue and Lenehan Road in Griffith was originally constructed in about 1946 using cast iron pipes. The section of pipeline to be renewed had experienced a number of bursts due to the internal deterioration of the cast iron. The cast iron pipes had been continually subjected to the effects of sulphuric acid, a product of the oxidisation of the hydrogen sulphide that naturally occurs in sewer mains. As the acid builds up it corrodes and weakens the pipe and causes it to crack and burst. The extent of the deterioration didn’t become evident until a C.C.T.V. was carried out prior to installation of the new liner.

The new liner was constructed using 560-mm OD PN 8 PE 100 polyethylene pipes supplied by Iplex Pipelines Australia Pty Ltd. The pipes were butt-fusion welded together to form a continuous string prior to insertion into the pipeline. As the pipes were being welded, each joint was debeaded.

The location of the existing sewer - sandwiched between a busy industrial-use roadway that ran through the city’s main shopping area and adjacent to the main water supply canal for the area - meant there was little room for the welding and construction equipment. To alleviate this, permission was sought, and granted, from the owners of Main Canal, Murrumbidgee Irrigation, to utilise the canal for storing the completed pipe string prior to installation.

The first string was inserted as one continuous length of over 600 metres. This is a substantial distance given the size of the polyethylene pipe in relation to the internal diameter of the existing main. By using specialised equipment for the sliplining procedure we were able to achieve such a long distance with just one pull. The second string was pulled through at nearly 300 metres.

The new liner exposed for the connection of the two strings. This picture shows the proximity of the road (top left) and Main Canal (top right), as well as the level of the water table.

By inserting the new liner in just two strings only one hole had to be opened in the existing pipeline, apart from the connection points at either end of the renovated length. This also reduced the number of fittings needed to join the strings together. No problems were encountered and in fact the actual sliplining only took 2 days to complete.

Mr Peter Gin, Water and Sewer Manger for Griffith City Council was extremely happy with the work that was carried out on this project. The direct cost-saving to the Council when comparing the two viable methods of replacing this main proved once again that the best solution is a trenchless method.

Airpipe Pty Ltd achieved accreditation with Sydney Water for our Corporate Occupational Health Safety & Rehabilitation Management System during 1999. This followed many months of documenting our existing work methods and quality procedures.

INTERSTATE OFFICES

Airpipe QLD Pty Ltd was incorporated in March 1999. Peter Coles and Kelvin Slade, with Kelvin running the day-to-day operations, jointly own the new company. Kelvin can be contacted on mobile 0409 608 787.

OTHER PROJECTS

Airpipe is still the major polyethylene welder for the bore liners throughout the Blue Mountains, west of Sydney. We have been carrying out this work for more than 8 years for a number of drilling companies that are involved in the construction of bores for Sydney Water to provide sewerage services to the residents of the Blue Mountains.

We have successfully carried out the welding, debeading and installation of bore liners up to 500 mm OD PN 20. Due to the nature of the terrain in the region, most jobs have to be carried out in extremely difficult situations, with pipe and equipment having to be lowered into deep trenches or onto built-up platforms. In one instance the butt-fusion welding machinery had to be lowered down a ravine and placed on a purpose-built platform off the side of a cliff in order to give direct access to the borehole.

Peter Coles, Managing Director, Airpipe Pty Ltd, P O Box 240, Picton 2571 Australia can be contacted for further information on mobile 0409 205 696 or phone: +61 2 4683 2363, Fax: +61 2 4683 2364, Email: airpipe@bigpond.com