Ian Vickridge, Consultant, and previous Technical Director with Black & Veatch Hong Kong and Past Chairman of the CHKSTT Trenchless International — October 2011
The Trenchless Technology industry in Hong Kong has grown significantly as the urban terrain challenges open-cut methods for major projects. Here, Past Chairman of the CHKSTT Ian Vickridge reflects on the trenchless industry and how he has seen it evolve.
Ian Vickridge first became involved with the development of Trenchless Technology in Hong Kong in 1997, when he presented a short course on Trenchless Technology to a group of young Hong Kong engineers. Among this group were several enthusiasts who went on to champion Trenchless Technology in Hong Kong, and eventually helped to form the China Hong Kong Society for Trenchless Technology (CHKSTT).
In 1997, there were already some interesting major trenchless projects underway, including some large diameter, deep sewer construction by tunnel boring machines (TBM) for Stage 1 of the Harbour Area Treatment Scheme (HATS), and a long-distance horizontal directional drilling (HDD) project. The HATS sewer construction had run into problems that were later resolved and the project was eventually completed in 2001. The HDD project was record breaking at the time, consisting of two large diameter bores, each 1.4 km long, drilled along difficult profiles through heavily faulted granite, deep below a main shipping channel and close to the new Tsing Ma suspension bridge. The bridge had recently been completed, connecting mainland Hong Kong to the new international airport on Lantau Island. However, although this project was a major achievement attracting international attention, the use of trenchless methods for the installation and rehabilitation of urban utility services was very limited, and most work of this nature was still being carried out by open-trench methods.
That being said, things were moving on and by the end of 1999, the HDD project was nearing completion. A similar HDD project to install electricity cables across the same Ma Wan Channel was well underway, and a small but dedicated group of individuals had formed the CHKSTT to act as a forum to encourage even greater use of trenchless techniques.
Initially the new society organised local technical talks and site visits, but they were soon gaining further exposure to the latest developments in Trenchless Technology through dialogue with the ISTT and other Affiliated Societies. In 2002, a delegation from Hong Kong attended the No-Dig International conference and exhibition in Copenhagen, and this was followed by participation in Trenchless Asia – a successful conference and exhibition held in Hong Kong in 2002.
Article continues below…
By this time there was considerable interest in trenchless methods, and it is interesting to note that although many of the papers presented at this conference were from overseas, there were several local papers describing the actual and planned use of a variety of trenchless methods in Hong Kong. This was largely influenced by the program of water mains replacement and rehabilitation that had been launched by the Water Supplies Department (WSD) of Hong Kong.
Trenchless makes its mark
By 2002, the use of trenchless methods for urban utilities was really taking off and it was not long before innovations were being made and international records established in Hong Kong. By 2004, a variety of rehabilitation techniques, including close fit PE linings, slip lining, cured-in-place pipe (CIPP), and spiral-wound linings, were being widely used. Open trench was no longer the only method being considered for installing new pipes and cables – HDD, pipe jacking, and pipe ramming were all recognised as being realistic, tried and tested alternatives.
The use of trenchless methods continued to flourish, and at the same time a synergistic interest in pipe condition assessment started to grow. Soon, a variety of new techniques for assessing pipe condition, by both direct and indirect methods, were being employed. These included historical reviews of burst and leaks, non-destructive methods for determining pipe wall thickness, soil corrosivity studies, stray current surveys, coating defect surveys, and leak detection surveys. This interest in condition assessment was evident in the papers presented at the first international conference organised by CHKSTT, which was held in Macau in 2007.CHKSTT went on to organise a subsequent conference in Hong Kong in 2009 for their 10th anniversary year and are now in the process of organising their 3rd conference to be held in Hong Kong later this year.
The people of the CHKSTT
One of the guests at the conference in 2009 was Glenn Boyce, who was instrumental in getting the CHKSTT going and was their first Chairman. Glenn later went on to become Chairman of the North American Society (NASTT). At the same conference Jon Boon took over the Chairman’s job at CHKSTT from Ian Vickridge – Jon had previously been Chairman of the UK Society (UKSTT) and Ian had previously been the Executive Secretary for UKSTT.
Another strong international player in the CHKSTT is Derek Choi, who is not only a past Chairman of CHKSTT but also a longstanding member of the ISTT Executive Sub Committee and now Vice Chairman of ISTT.
Although the CHKSTT is relatively small, it has always had strong international links with other Affiliated Societies and the ISTT. It is these connections and the international support provided by ISTT and the family of trenchless societies that have helped drive the advancement of Trenchless Technology in Hong Kong over the past decade or so.
Under Hong Kong
As one of the most densely populated cities in the world, Hong Kong is a city where trenchless techniques are not only preferable in construction and maintenance, but often essential.
With a total area of 1,104 square km and a population of more than seven million people, most of the land in Hong Kong is occupied. When underground infrastructure requires repairs or general maintenance, simply digging to reach infrastructure is not always an option.
Further complicating matters is the fact that the majority of land is hilly to mountainous, with steep slopes, making conventional trenching techniques for laying and then maintaining underground infrastructure difficult.
Sparking the trenchless boom
In 1998, Hong Kong’s WSD first used Trenchless Technology on a large scale water main installation program, sparking a boom in no-dig techniques in Hong Kong. The value of trenchless work in Hong Kong started expanding from a previously low base as business began to invest in trenchless equipment and expertise.
Contracts for works relating to trenchless technologies in Hong Kong were often subcontracted as part of larger projects to companies that specialised in the field of trenchless methods. This was due to the fact that only larger, government-approved companies in Hong Kong could qualify to bid for sizeable civil engineering contracts, while companies that specialised in Trenchless Technology – which tended to be smaller, while the industry developed – were left to bid on the individual works involved with these projects.
When the industry in Hong Kong was still small and developing, local contractors partnered with overseas firms to gain further expertise and a base with which to tap the Hong Kong market. In particular, German companies are well regarded both in Hong Kong and worldwide for their reputation for reliable technical support.
Germany’s Herrenknecht dominated the microtunnelling market, spiral wound PVC was well regarded for close fit lining, and German products were often called on for pipe cleaning equipment, relining and pipe bursting.
Giving new life to old water mains
Hong Kong’s fresh water and salt water supplies are provided through a network 7,800 km of water mains, most of which are underground. A substantial portion of these water mains were laid over 30 years ago and are now approaching the end of their service life, becoming increasingly difficult and costly to maintain.
As such, WSD is currently undertaking the Mains Replacement and Rehabilitation program, which will see approximately 3,000 km of the water mains rehabilitated or replaced.
This massive 15-year phased project started in 2000 and the estimated cost is $HK22.8 billion ($US1.3 billion). Due to its size, the project has been divided into sections by region. The program is currently in its final stage, which started in March 2011, and approximately 53 per cent of overall works were completed in June 2011. It is estimated that 30 km of water mains are replaced or rehabilitated monthly.
Important considerations for all sections of the project include avoidance of unnecessary water supply disruption to consumers, avoidance of unnecessary traffic disruption during construction and cost effectiveness of the works, with priority to be given to water mains susceptible to leakage and bursting.
While conventional mains replacement methods of opening trenches and laying new mains continue to be used where the traffic and environmental impacts arising from the works are not serious and when the underground utilities present are not congested, sections of the project require the use of trenchless methods.
As these techniques have been employed to avoid Hong Kong’s already congested underground infrastructure network, the replacement water mains have been laid deep underground.
The main techniques the WSD has been using for replacement of mains include pipe ramming, pipe jacking and horizontal directional drilling, while the main techniques to be employed for rehabilitation will be the close fit lining method, the cured-in-place pipe method and the pipe bursting method.
The project is due for completion in 2015.
Breaking ground around town
In recent years, Hong Kong has embraced the benefits of microtunnelling for many of its infrastructure projects.
With the country’s dense urban landscape, the use of microtunnelling has vast benefits such as avoiding the disruption and damage caused by excavation. Pipelines can be installed using a remotely controlled and steerable method, usually with the use of a laser guidance system.
Microtunnelling is well suited to rigid line and level criteria, which enables boring to be undertaken at flatter grades.
Construction on the Drainage Services Department of Hong Kong’s Tuen Mun Western Trunk Sewerage Project is ongoing since its commencement in 2009.
Chun Wo Development Holdings Limited was contracted last year by the department to use a TBM for pipe construction for more than 4 km of the 6 km long trunk sewer.
The project, which also included a sewage pumping station, is expected to be completed in 2014.
Basket is empty.
