Overall Strategy and Programme
The rapid growth in the last few decades has transformed
Hong Kong into an eminent financial and communication centre and
one of the most densely populated cities in the world. The dramatic
increases in economic activities and population have produced large
quantities of foul water or sewage - over 2.4 million cubic metres
every day.
To protect the marine environment, the sewage must
be properly collected and treated, through the public sewage facilities,
before its disposal to the sea. With our continuous investment in
the public sewerage infrastructure, all urban areas of Hong Kong
and much of the developed New Territories are now provided with
a public sewerage system, covering about 95% of the households and
over 98% of the sewage produced.
To cope with the increasing development and the
rise in the standard of living, we need to continuously expand and
upgrade the sewerage infrastructure. The Sewage Strategy Study completed
in 1989 established the long term strategy for collecting, treating
and disposing of the wastewater generated by the community to meet
the water quality objectives.
Stonecutters Island Sewage Treatment Works
treats over half of the sewage produced in Hong Kong every day |
The study recommended substantial improvements
to the public sewerage facilities for the whole territory and the
whole strategy has two main components, the Harbour Area Treatment
Scheme (HATS) and the Sewerage Master Plans (SMPs). The HATS caters
for the urban centres around Victoria Harbour, which generate more
than 70% of sewage in the territory. Under the stage I of HATS,
sewage is collected and transferred to a centralized sewage treatment
plant at Stonecutters Island by deep tunnels where it will receive
chemically enhanced primary treatment (CEPT) before discharge to
the western harbour.
Under the SMPs, improvements to the sewerage system
in the territory are being carried out on a catchment-by-catchment
basis in which the territory is divided into 16 SMP areas. In each
of these areas, the existing sewerage network is extended and improved,
and existing sewage treatment works (STWs) are upgraded or new facilities
are constructed so as to ensure sufficient capacity for conveying
and treating sewage generated today and from future developments.
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Sewerage Master Plan Areas |
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New Works
DSD is responsible for the design, construction
and commissioning of the sewerage improvement works. This is a huge
and hard undertaking because the provision of new and adequate sewerage
infrastructure to cope with the rapid development of Hong Kong requires
vast resources and the new facilities take time to build.
In December 2001, the successful completion of
the HATS Stage 1 marks an important milestone in sewage treatment
in Hong Kong, as well as a remarkable engineering achievement by
international standards. The scheme is now treating over 1.3 million
cubic metres of sewage collected from Kowloon and the northeastern
part of Hong Kong Island each day, bringing substantial improvement
to the water quality of Victoria Harbour. A programme of trials
and studies is also being implemented by Government with a view
to formulating the way forward for the further stages of HATS.
SMP works, which started in 1989, are progressing
well. Two SMPs, namely the Chai Wan & Shau Kei Wan SMP and the
HK Island South SMP were completed in 1997 and 2000 respectively.
The East Kowloon SMP, which involves the construction of about 17
km of sewers and the rectification of expedient connections in the
industrial areas in San Po Kong, Kowloon Bay and Kwun Tong, was
substantially completed in 2001. The North West Kowloon SMP and
Aberdeen, Ap Lei Chau and Pokfulam SMP are making good progress
and are now 90% and 80% completed respectively. For Central, Western
& Wan Chai West SMP and Wan Chai East & North Point SMP,
which serve northern Hong Kong Island, construction for the stage
2 works has commenced. The other SMPs are under various stages of
design or construction, and are scheduled for completion in phases
by 2013.
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![](images/03/3-6.jpg) |
Relining of sewer at Chai Wan |
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Harbour Area Treatment Scheme, Stage I project |
Upgrading of major STWs will continue so as to
keep pace with increased development and to suit the latest water
quality objectives. The upgrading works at Shek Wu Hui STW was substantially
completed in August 2001. This financial year we also started the
construction works for three major STWs, which include Shatin STW
stage 3 extension, Sham Tseng STW and the upgrading of Siu Ho Wan
STW. The planning and design for the upgrading of other STWs such
as Tai Po STW Stage V, San Wai STW, Pillar Point STW and Sai Kung
STW phase 2 is well underway. However, in view of the latest population
growth and housing demands, more sewerage facilities and services
would be required and reviews of the SMPs are being undertaken by
the Environmental Protection Department (EPD).
Brief descriptions of major sewerage projects are
attached in Appendix D.
From the establishment of DSD in 1989 to now, we
have been implementing sewerage projects with a total cost of about
$31.8 billion, comprising $8.2 billion for HATS Stage I, $17.2 billion
for SMP works and $6.4 billion for other associated works. So far,
we have completed works amounting to $19 billion under the programme,
another $6 billion of works is being planned for the next five years.
In 2001/02, the expenditure on sewerage projects was $1.8 billion.
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Sewer improvement works under SMP |
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Operations and Maintenance of the Sewerage
System
About 95% of the population is at present served
by the public sewerage system with over 98% of the sewage produced
being collected and treated. This system includes a sewerage network
of about 1,400 km in length. To maintain this extensive and comprehensive
network of sewers and to ensure their proper functioning at all
times, DSD has implemented a preventive maintenance programme for
carrying out regular inspection and cleansing of sewers. In 2001,
we have inspected 876 km of sewers, of which 697 km were cleansed,
and removed 5,200 m3 of silt, costing a total of about $57 million.
To enhance the management of drainage and sewerage
assets and the services to the public, DSD completed digitization
of all drainage records in 1996. This has enabled us to handle requests
for drainage records efficiently. The system is being further enhanced
so as to assist the planning of maintenance works and generate statistical
reports on assets for better management of resources.
In 1997, we installed a Drainage Complaints Information
System (DCIS) to replace the manual procedures for recording drainage
complaints. All complaints received are directly input into the
database so that progress on the follow-up actions can be monitored
effectively. This system also serves to identify black spots for
planning and reviewing of the preventive maintenance programme.
With a view to enhancing the operational efficiency
in handling drainage complaints, a Direct Labour Force Mobile Computing
Application (DLFMCA) has recently been developed. With the integration
of the DLFMCA and the DCIS, the workforce can make use of a Personal
Digital Assistant (PDA) to receive work orders, capture work results,
take site photos and make sketches on-the-spot. All captured data
can be uploaded to the DCIS by a simple operation when the staff
return to the depot thus greatly improving the efficiency in processing
drainage complaints and facilitating the monitoring of work progress.
Following the successful pilot implementation launched in August
2001, the application was migrated to full production in May 2002
to bring full benefits to the operation in handling drainage complaints.
Numbers of complaints on blockage of sewers received
and dealt with in past years are shown in Appendix
E.
As the Drainage authority, DSD is responsible for
vetting public and private developments with respect to their impacts
on the sewerage system. We also provide advice, as necessary, on
their connections to the public sewerage system. In 2001, we have
processed over 29,000 sets of sewerage-related submissions and issued
154 demand notes for connections for new developments.
![](images/03/31.gif) |
Figure 3.1 Percentage of treatment at different
levels |
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![](images/03/3-7.jpg) |
Personal Digital Assistant (PDA) can take site photos |
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Colleague inputs work result to the PDA and send back to DCIS |
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Operations and Maintenance of Sewage Treatment Facilities
DSD is currently operating about 200 sewage handling
facilities including about 60 STWs scattered over HK in which pollutants
in sewage are removed by various treatment processes so as to achieve
the discharge requirements as specified in the discharge licences.
Location of major STWs is shown in Appendix
F.
In terms of levels of treatment, preliminary treatment
or screening basically removes large particles of 6 mm in diameter
and above and grit of over 0.2 mm in size from the sewage. In primary
treatment, further removal of pollutants is carried out by sedimentation.
The Chemically-enhanced primary treatment (CEPT) plant at Stonecutters
Island makes use of chemical additives to speed up and enhance the
sedimentation process and, hence, achieves higher and faster removal
of pollutants than the normal primary treatment plants. Secondary
treatment plants provide biological treatment to sewage in which
organic matters are converted to stable substances by bacterial
activities.
In 2001, we have treated a total of 885 million
m3 of sewage. 64.5%, 0.5%, 17.2% and 17.8% of the sewage received
preliminary treatment, primary treatment, CEPT treatment and secondary
treatment respectively.
Facility |
Hong Kong Island
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Kowloon
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New Territories
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Outlying Islands
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Total
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Sewage pumping stations/ Low flow interceptors |
30
|
29
|
68
|
14
|
141
|
Preliminary treatment plants |
11
|
6
|
6
|
1
|
24
|
Primary treatment plants |
-
|
-
|
-
|
2
|
2
|
Chemically-enhanced primary treatment plants |
-
|
1
|
-
|
-
|
1
|
Secondary treatment plants |
2
|
-
|
21
|
8
|
31
|
Total : 199 |
Table 3.1 The geographic distribution of sewage
pumping stations and treatment plants of different treatment
levels |
The sludge arising from the sewage treatment process
is currently dewatered to a minimum of 30% dry solid content before
final disposal at sanitary landfills. In 2001/2002, a total of around
197,000 tonnes of dewatered sludge and 21,400 m3 of screenings and
grit were disposed of.
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Final sedimentation tank helps remove floc
before effluent discharge |
In addition to all the proactive measures taken
to ensure effective operation of our sewage treatment facilities,
the department has designated engineers to carry out research and
development work with a view to further improving our services,
such as finding solutions for operational problems in sewage treatment,
and keeping abreast of the latest technological development in the
field.
To minimize breakdown of sewage treatment facilities,
we have been applying advanced computer software to administer the
day-to-day maintenance on the electrical and mechanical equipment
in the major sewage treatment works. Proper maintenance of buildings
and concrete structures in STWs is equally important and the task
is managed by a dedicated team of engineers. Regular inspection
and repair, if necessary, of structures is carried out to ensure
integrity of structures and proper functioning of the plants. Apart
from these, landscaping work including planting of 9,232 trees/shrubs,
re-painting of 20 plants and cleansing of 139,520 m2 of structures
had been carried out during the year in order to upkeep and beautify
the appearance of these plants.
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Operations and Maintenance of Submarine Outfalls
There are a total of 43 submarine outfalls and
two effluent disposal tunnels built for effective discharge of treated
effluent in a controlled manner. To prevent pollution of the receiving
water bodies caused by the leakage of effluent through cracked submarine
outfalls, inspections and maintenance of the outfalls are carried
out regularly. One of the effective means adopted for monitoring
the performance of the outfalls is by helicopter inspection of dye
test on the outfall pipes. Dye tests on these 45 effluent outfalls
and tunnels at 24 plants have been carried out during the year,
and 17 detected leakage were subsequently repaired. In addition,
underwater inspection, hydrographic sounding survey, regular flushing
and desilting of outfalls have been carried out as scheduled in
a comprehensive preventive maintenance programme.
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Overview of Sandy Bay Preliminary Treatment Works |
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Dye test on an effluent
outfall at Shau Kei Wan |
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Harbour Area Treatment Scheme (HATS)
In 1989, the Sewage Strategy Study recommended
the Strategic Sewage Disposal Scheme [now renamed as HATS] to collect
and convey all wastewater from the urban areas surrounding Victoria
Harbour through a deep tunnel conveyance system to one or two centralized
sewage treatment works for treatment, before final disposal to the
waters south of Hong Kong.
The Scheme is a major Government initiative to
clean up Victoria Harbour and is to be implemented in stages. Stage
I focuses on the collection and conveyance of sewage from Kowloon
and the northeastern part of Hong Kong Island to Stonecutters Island
for centralized treatment, while the furthur stages aim at collecting
and treating sewage from the northern and southwestern parts of
Hong Kong Island, as well as providing a higher level of treatment
for all the sewage in order to meet the environmental standards.
Construction of HATS Stage I commenced in mid-1994.
It entails the upgrading of seven existing preliminary treatment
works and construction of a 23.6 km-long deep tunnel conveyance
system, a large-scale sewage treatment works at Stonecutters Island
and a 1.7 km-long outfall tunnel, serving a population of 3.5 million
people.
The deep tunnel conveyance system was adopted not
only to allow the shortest route to be chosen but also to minimise
the disturbance and nuisance to the public, the environment, utilities,
transport systems, etc. during construction. The tunnel system consists
of seven deep tunnels of finished diameters from 1.2m to 3.5m and
depths at 76m to 143m below sea level, and has a minimum rock cover
of 30m. Except for the shortest tunnel section from Kwai Chung to
Tsing Yi, which was constructed by drill and blast method, hard
rock tunnel boring machines (TBMs) were used for excavating the
other six tunnels. Owing to the forfeiture of the original tunnel
contracts in December 1996, progress of the tunnel construction
had been seriously disrupted. The tunnel progress had also been
affected by the adverse geological conditions encountered during
excavation. Despite all these problems and difficulties, all tunnels
were successfully completed in December 2001 and the Stage I system
has since been commissioned and put into full operation. It is now
treating over 1.3 million cubic metres of sewage collected via the
deep tunnels every day at Stonecutters Island before dispersing
the treated effluent into the western harbour through the Stage
I Outfall.
The Stonecutters Island Sewage Treatment Works
adopts a Chemically Enhanced Primary Treatment (CEPT) process and
has a capacity for treating 1.7 million cubic metres of sewage each
day. It is achieving excellent performance results and is the world's
most efficient plant of its kind. Its main underground pumping station
is also the largest in Asia having a pumping capacity of 31 cubic
metres per second.
As for the further stages of the Scheme, the Environmental
Impact Assessment Study, completed in 1999, recommended that chemical
treatment enhanced by disinfection should be adopted and the effluent
be discharged to the east of Lamma Island. However, in view of the
public concerns regarding the above development plan, the Government
commissioned a second International Review Panel (IRP) to review
the proposed scheme. The review was completed in November 2000 recommending
that consideration should be given to upgrading the treatment level
to a higher standard and discharging the effluent within the harbour
areas. On this basis, the IRP suggested four alternative plans with
different degrees of centralization of treatment facilities and
locations of outfalls for further development of HATS.
In response to the IRP's recommendations, a series
of studies and trials are now being undertaken to assist in formulating
the way forward for the subsequent stages of HATS. These include
the environmental and engineering feasibility studies (by EPD) to
investigate the viability of the IRP's options, the pilot plant
trials (by DSD) to study the application of compact sewage treatment
technologies for Hong Kong sewage, and the study on procurement
options (by DSD) to identify the most efficient and effective procurement
arrangement for implementing the further Stages of HATS. All these
studies and trials have commenced and are scheduled for completion
by early 2004.
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The Stonecutters Island STW is the most compact and efficient CEPT plant in the world |
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Asia’s largest sewage pumping station |
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Stopping 600 tonnes (i.e. 40 standard container units)
of pollutants from entering the harbour every day |
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Wan Chai East and North Point Sewerage —
an integrated approach to sewer construction in urban areas
The Wan Chai East and North Point Sewerage Improvement
Works is one of the major Sewerage Master Plan projects. It aims
to improve and upgrade the existing sewerage systems in Wan Chai
East and North Point to meet development needs up to the year 2021.
The works comprise the construction of about 17 km of sewers and
a new pumping station and the estimated project cost is $1.6 billion.
An essential but a very difficult portion of the works is the construction
of two lengths of trunk sewers in some of the busiest roads in Causeway
Bay and North Point, a 1 km long sewer along Yee Wo Street, Hennessy
Road, Percival Street and Gloucester Road and a 2.7 km long sewer
along Electric Road and Java Road. Thus an important consideration
in our planning and design of the works is to minimize the impact
on traffic as well as the nuisance and inconvenience to the public
that may be induced by the construction activities. An effective
measure is to construct the trunk sewers by means of trenchless
methods which can largely reduce the extent of road opening, and
can thus minimize disruption to traffic, businesses and public.
It is also more environmental friendly because we can minimize and
effectively control the environmental impacts such as noise and
dust generated from the construction activities.
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It is a challenging undertaking to build sewers in the busiest road in Causeway Bay and North Point |
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Trial run of the temporary traffic scheme at Percival Street, Causeway Bay |
Advance Contract Helps Reduce
Risks for the Construction of Trenchless Sewer
Trenchless methods, though largely reduce the extent of road openings
on the surface, require the construction of working shafts of considerable
size at suitable locations for the laying of sewers underneath the
road surface. As the shafts are usually located at the heavily trafficked
junctions, there are high risks that, after the contract has started,
it is found that the location may need to be changed due to prevailing
traffic conditions, presence of underground utilities or ground
conditions. This would lead to additional cost and delay in the
construction.
In order to reduce the risks, costs and time associated
with trenchless construction, we have adopted an innovative approach
by the use of an advance contract to provide relevant information
as much as possible before tendering of the construction contract.
In the advance contract, we conduct full-scale trial runs for all
agreed temporary traffic schemes to demonstrate their effectiveness
and to modify the temporary traffic arrangements if necessary. With
the agreed traffic schemes and the finalized locations of shaft
sites, we carry out further investigation works to obtain more ground
and utilities information, including trial trenches at shaft sites
to eliminate the risk of uncharted utilities. We also make advance
co-ordination and planning for all utilities diversions that are
found necessary. This largely reduces unforeseen risks during construction
and minimizes delay to the construction works.
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Trial run for agreed temporary traffic scheme |
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Underground utilities |
Public Relations Strategy
Though we are using trenchless technique for the construction of
trunk sewers, some disturbance to the public and shop owners would
still be unavoidable. It is very important that those affected are
well aware of the benefits of the works and our readiness to mitigate
any potential disturbance.
Therefore, we have, prior to tendering of contracts,
conducted presentations to the Wan Chai and Eastern District Councils
to brief the council members about our proposed works and traffic
diversion arrangements in the concerned areas during construction
and have obtained their support. We will report regularly to the
Councils on the progress during construction. We have also prepared
and distributed information leaflets, through District Offices,
to the council members and the general public, especially those
shop owners and local residents who are likely to be affected by
the works. Pictorial signboards have also been placed at predominant
locations at the works sites to inform the general public of the
progress of proposed works, traffic and/or pedestrian diversion
schemes and other relevant information at that particular site.
We will regularly update the information to keep the people affected
fully informed.
After commencement of the contracts, the Resident
Engineer and his site staff have established regular contacts with
all concerned parties, ie the shop owners and committees of private
buildings that might be affected by the works. There is a patrol
team specially organised to carry out regular inspection of the
works sites to ensure safety and minimum nuisance to the public.
A 24-hour hotline has also been set up so that any public concern
or complaint can be received and dealt with promptly. In addition
to the hotline, the public may also use the feedback forms attached
with the information leaflets to provide their feedback on the works.
Closures of heavily trafficked roads or footpaths
or construction activities in front of shops will never be welcome.
However, we have integrated advanced construction technology, innovative
contracting strategy and a proactive public communication approach
to provide a cost-effective and workable solution in this Wan Chai
East and North Point sewerage improvement project. In particular,
this is the first time DSD has introduced an advance contract prior
to tendering of the main works. We have achieved a significant reduction
in the contract sum of the main works contract. The construction
works had started in May 2002 and are scheduled for completion in
early 2006.
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Excavation of trial trench
at Electric Road, North Point |
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Information leaflets will be distributed to the affected community about the works progress |
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