Night works

It is a cold winter’s night in Hong Kong, and the clock has passed midnight. A manhole has been widened at Shek Pai Street, and a crane truck stands to the side to deliver some 100 meters of cured-in-place-pipe (CIPP) liner. Fifteen workers are putting the liner into the manhole to rehabilitate a more than 50-year-old granite-based pipe covered with concrete on top, which has been damaged and poses a risk of the road collapsing.

 

The 1960s street in the Kwai Chung district in Kowloon is a vital transportation link for the 5,000 residents who live in the area and is surrounded by high-rise buildings on both sides. Despite being a construction site, traffic passes by easily in one open lane and there is little noise.

 

Underground, there is an old trunk drain that conveys stormwater from upstream catchment areas to the downstream drainage network. Originally, this was a nullah* constructed by stone pitching before it was converted to a pipe and the street built over it.

 

Thanks to CIPP technology and liners, residents in the area can now feel safer after only a minor disturbance on their street for just a couple of nights. If the traditional “open, cut and replace” method had been used, it would have required complete closure of the road for 12 to 24 months, leading to noise, traffic jams and pollution in the form of vehicle fumes, dust and road waste.

 

“CIPP technology allows the rehabilitation or construction of a new pipe inside an old one without the need to excavate the entire length of the old pipe,” says William Wong, Business Development Manager for Trelleborg’s seals and profiles in Asia-Pacific.

 

“In this case, only minor construction was required to enlarge the manholes to allow access for the new pipe, which is larger than the original manhole,” he says. “During the day, the road is open; at night, the work is carried out in most cases without the community noticing. 

This project highlights the advantages of trenchless technology over traditional open, cut and replacement of old and defective pipes.”

 

Trelleborg has both the expertise and a large range of products to support pipe rehabilitation projects, including customized solutions for water infrastructure challenges.

 

“For the rehabilitation of sewer pipes, our flexible pipe liners are used in combination with our polymer resin systems,” Wong says. “Furthermore, our stoppers and flow-through plugs are optimally suited for the temporary blanking off and bypassing of flows during pipe tests and repairs.”

 

“Hong Kong is a fully developed and densely populated city,” says Saul C M Chan, Principal Project Coordinator for planning and rehabilitation at the Hong Kong Government’s Drainage Services Department. “The majority of the drainage and sewerage systems were built decades ago and some of them are deteriorating. They should be rehabilitated as soon as possible to avoid malfunctioning of these systems and the possible adverse impact arising from pipe failures.

 

“Compared with other trenchless methods, the CIPP method is a proven technology with good ­control of workmanship and quality,” Chan says.

The old horseshoe-shaped pipe in the Hong Kong project, measured 1.3 meters wide, which is unusually large compared with pipes in Western countries, where 300 millimeters is considered big. Rehabilitation of the pipe with Trelleborg’s product allows extension of the pipe’s life and its service to the community by at least 50 years.

 

Wong describes CIPP technology as a sustainable way to extend the life of infrastructure while also increasing capacity. “The Shek Pai Street project is just one example of the many drainage and sewerage systems that need to be rehabilitated in Hong Kong,” he says. “The rehabilitation of these systems is crucial to ensure the safety and well-being of the ­population and to avoid damage to the environment.”

 

By 6 am, the first phase of Trelleborg’s CIPP project at Shek Pai Street is essentially complete. There will be a couple more nights of work before the project is finally finished, but then the residents in the area can feel assured of effective storm drainage and that roads will not collapse for many more decades.