Two different size drain pipes but only one lining.

FOR some Hunters Hill Council in Sydney is in a unique situation. In size, it is the smallest Municipality in NSW but the 3,700 odd rated properties are valued in excess of $3 billion. The Municipality is nestled between the Parramatta and Lane Cove Rivers on the inner foreshore of Sydney Harbour with large private residences along tree lined streets. 

This historic sandstone residence (Clifton) was built in 1890 by John Ryder-Jones, then chairman of the Sydney Stock Exchange.

Not the sort of location to send in excavators, jack hammers etc. to dig up and relay a faulty drain. Faced with just such a problem, the Council chose to investigate the alternative of Trenchless Technology. 

Paul Murphy, Development Engineer with Council contacted Kembla Watertech and explained the situation. A drain pipe running from Woolwich Road down through private property and into the Parramatta River was leaking badly and storm water was finding its way into No.7 Woolwich Rd.

A CCTV survey of the particular drain revealed faulty joints, cracked connections and worse, the pipe had a change in diameter in the back yard of a private residence where there was no access for equipment.

The question asked of Kembla was; "Can you structurally repair this drain which is made up of two pipes of different diameter with access to one end only? " Our reply; "Yes we can. We will join two different size linings together and install it in one installation".

Kembla's price for this Trenchless Technology solution was considerably less than other quotations and we were asked to carry out the work. The cost of dig up and relay was too horrendous to even worth thinking about! 

Kembla Watertech's Enviroliner system is a process for the renovation of pipelines by the installation of a resin impregnated, flexible tube which is inverted into the existing conduit by use of hydrostatic pressure. The tube is cured to a hardened state while held in intimate contact with the conduit. This type of system is classified as a Cast In Place Pipe (CIPP) and is a trenchless method for restoring full structural integrity to deteriorating pipelines. The Environliner method results in a seamless, jointless "pipe-within-a-pipe" with a smooth continuous inner surface which results in an increase in flow capacity of the lined pipe.

The first stage at Hunters Hill was to CCTV survey the drain to log the positions of the branch connections and determine the exact location of the change in diameter. The survey revealed that the drain was actually 490mm diameter for the first 26 metres and then 415mm diameter for the next 36 metres. Kembla's engineering department designed the thickness of the lining in accordance with AS/NZ 2566.1: Buried Flexible Pipes to give a minimum life of 50 years. 

At the manufacturing stage, the 490mm diameter length was joined to the 415mm diameter length by a one metre long tapered section. This 'composite' lining was then impregnated with catalysed resin and transported to the site. The lining was installed into the drain from an existing pit in Woolwich Street (see photograph). A small scaffold tower was erected to provide the hydrostatic head that inverts the lining (turns it inside out) into the existing pipe. 

The inversion process continued until the lining passed through the intermediate pit in the back yard (see photograph) and finished at the downstream access pit. After curing of the lining the hardened ends were removed and a robotic cutter used to reinstate the connections without excavation. A CCTV survey of the completed job showed that the lining was in intimate contact with the existing pipe wall, the tapered change in diameter had been made correctly and all live connections had been reinstated.

Lining being installed from existing drain inlet Lining through the pit in the backyard

Paul's final comment: "Hunter's Hill Council has a responsibility to protect the environment and to provide our rate payers with the most cost effective solutions for maintenance of our infrastructure. The entire lining process was completed by Kembla in 8 hours and with minimal disruption. We are very satisfied with the technology and service provided by Kembla to solve a difficult problem in such a cost effective manner. Council have had no further complaints despite record rains."

 Article supplied by Kembla Watertech.

Last Updated on 29 December 2002