Planning, Design and Construction of New Sewerage Facilities
Planning, Design and Construction of New Sewerage Facilities
Relocation of Sha Tin Sewage Treatment Works to Caverns
To expand and make good use of land resources, the Government has been actively exploring viable solutions for developing rock caverns. The Sha Tin Sewage Treatment Works (STW) is earmarked for relocation to a number of caverns to be excavated in Nui Po Shan opposite Shing Mun River. Upon relocation, the STW's maximum design sewage treatment capacity is 340,000 cubic metres per day, which is about 36% greater than that of the existing facility. The relocation will release about 28 hectares of land on the existing Sha Tin STW site for other uses that benefit the public and improve the living environment of the district.
The future Sha Tin STW relocated in a cavern complex will be the largest of its kind in Hong Kong. The whole project is anticipated to be completed in about 13 years. The relocation plan will be implemented by stages, including site preparation and access tunnel construction, main caverns construction and upstream sewerage collection works, sewage treatment facilities installation, as well as decommission and demolition of the existing Sha Tin STW.
Current Progress
The project's design work has been completed in phases since 2017. Stage 1 works, which include site formation, construction of access tunnel and retaining structures as well as associated road works, have commenced since February 2019 and are expected to be completed as scheduled in the fourth quarter of 2022. The DSD is working on the detailed design for the remaining stages of construction works. We will continue to push forward with all work stages and seek funding approval from the Finance Committee of Legislative Council timely.
Harbour Area Treatment Scheme
The Harbour Area Treatment Scheme (HATS) is Hong Kong's largest ever environmental infrastructure project, aiming to improve the water quality of Victoria Harbour by collecting and treating sewage from both sides of the Harbour. The project had been carried out in two phases since 1994, with construction works spanning over two decades at a total cost of $25.8 billion. The facilities of HATS Stage 1 and Stage 2A were fully commissioned in December 2001 and December 2015 respectively. In order to maintain and enhance the reliability of sewage treatment services of the HATS system, we will carry out a study to review its performance, assess the operational condition of the different system components and draw up recommendations based on study findings for the enhancement of the HATS facilities.
Current Progress
Consultancy study on the system management is scheduled to commence in mid-2020 for completion in 2021.
Shek Wu Hui Effluent Polishing Plant
To keep pace with the rapid development of North District, we are expanding the treatment capacity of Shek Wu Hui Effluent Polishing Plant from 93,000 cubic metres per day to 190,000 cubic metres per day in phases, while upgrading the facility to tertiary treatment level to ensure that its discharge will comply with more stringent environmental requirements, thus protecting the ecological environment of Deep Bay. We will also take this opportunity to revamp the plant's exterior and environmental performance, bolstering its role as an educational site for water conservation and transforming the plant into an iconic multipurpose community facility.
Current Progress
The DSD commenced the advance works of Shek Wu Hui Effluent Polishing Plant in mid-2015 to convert a group of conventional secondary treatment facilities with a capacity of 20,000 cubic metres into a membrane bioreactor with a capacity of 40,000 cubic metres. This group of facilities has been in operation since December 2019. The main works are being implemented in three phases, with the first phase started in the third quarter of 2019 and the final phase scheduled for completion in 2034. The estimated cost for advance works, investigation and design is about $500 million and the estimated cost for the main works comes to about $13.2 billion.
Yuen Long Effluent Polishing Plant
The existing Yuen Long STW provides sewage treatment services for Yuen Long Town, Yuen Long Industrial Estate and Kam Tin areas. In view of the ever-increasing volume of sewage in the areas concerned, we will expand the treatment capacity of Yuen Long STW in stages from 70,000 cubic metres per day to 150,000 cubic metres per day. The facility will also be upgraded to tertiary treatment level to ensure that its discharge will comply with more stringent environmental requirements, thus protecting the ecological setting of Deep Bay. We will also take this opportunity to introduce numerous greening features to beautify the plant's exterior, as well as using renewable energy to enhance its environmental performance, and providing public co-use facilities for the benefit of the local community.
Current Progress
An Environmental Permit was granted in April 2019. Tender for the extension works is on-going. Construction will be implemented in two stages. Stage 1 Works are scheduled for commencement in the fourth quarter of 2020 and completion in 2027. The estimated cost for investigation and design is about $89 million while the estimated cost for Stage 1 Works is about $6.8 billion.
Expansion of Sha Tau Kok Sewage Treatment Works Phase 1
Sha Tau Kok STW is a secondary treatment works that provides centralised treatment for sewage collected from Sha Tau Kok Town, Yim Liu Ha, Tsoi Yuen Kok and Sha Tau Kok Chuen. To cope with the anticipated increase in sewage volume of the Sha Tau Kok sewage catchment, we will redevelop the Sha Tau Kok STW in situ to increase its treatment capacity from about 1,660 cubic metres per day to about 5,000 cubic metres per day. The project includes the construction of a submarine outfall which is approximately 1.7 kilometres in length and 450 millimetres in diameter, and the decommissioning of existing sewage pumping station and associated sewage rising mains.
This is the DSD's first “Construction 2.0” pilot project. Heading in the direction of “innovation, professionalisation and revitalisation”, the project team will adopt off-site construction, smart infrastructure and Building Information Modelling to enhance efficiency, quality and safety management.
Current Progress
Construction works commenced in November 2018 for completion in 2025. The estimated project cost is about $2.04 billion. The contractor has to build temporary sewage treatment facilities to maintain sewage treatment to the service area in the construction period .
Upgrading of San Wai Sewage Treatment Works Phase 1
Since population growth in Yuen Long, Tin Shui Wai and Hung Shui Kiu has led to increasing pressure on sewage treatment facilities in the areas, we are increasing the treatment capacity of San Wai STW from about 164,000 cubic metres per day to about 200,000 cubic metres per day. Upon completion of the project, the sewage treatment level of San Wai STW will be upgraded from preliminary treatment to chemically enhanced primary treatment with ultraviolet disinfection. By then, the quality of Hong Kong's northwestern waters will be improved.
Current Progress
The project commenced under a “Design, Build and Operate” contract in May 2016 and is scheduled for completion in December 2020. Upon completion of construction works, the contractor will undertake the operation and maintenance of the new San Wai STW for a period of 10 to 15 years. The estimated project cost is about $3.14 billion.
Upgrading of Cheung Chau Sewage Treatment and Disposal Facilities
The existing Cheung Chau STW provides sewage treatment services for the population of Cheung Chau. To facilitate the gradual expansion of the village sewerage network to other unsewered areas on the island in the future, we will construct additional treatment facilities at Cheung Chau STW to increase its sewage treatment capacity from 4,000 cubic metres per day to 9,800 cubic metres per day, and upgrade its sewage treatment level from primary to secondary.
Current Progress
An Environmental Permit was granted for the project in May 2014. Detailed design for the upgrading works is in progress. Construction is scheduled for commencement in 2020 and targeted for completion in 2026.
Heung Yuen Wai Sewage Treatment Works
Heung Yuen Wai STW, located in Liantang/Heung Yuen Wai Boundary Control Point (BCP), is a small-scale secondary STW with a design capacity of about 360 cubic metres per day. The plant adopts the membrane bioreactor (MBR) technology for sewage treatment. Frist, sewage passes through screens. Then, all organic matters, suspended solids, ammonia-nitrogen, nitrate and nitrite-nitrogen are removed from sewage by the MBR. As a last step, effluent is purified by hollow fibre membranes before discharge. Sludge produced during the sewage treatment process is transported to Shek Wu Hui STW for further treatment.
Current Progress
Heung Yuen Wai STW has been in operation since August 2019, providing treatment for sewage collected from various facilities such as the passenger clearance building, public toilets and government offices at the BCP.
Professional Laboratory Services
To effectively monitor the water quality and efficiency of sewage treatment process so as to ensure compliance of treated sewage with specified discharge requirements, we carry out regular sewage sampling and analyses. The DSD operates a number of laboratories and adopts the Laboratory Information Management System (LIMS) as well as business intelligence software to facilitate laboratory workflow automation and computerised management. Consolidation of laboratory results and operation data allows us to monitor the quality of effluent discharged and facilitate both decision-making and control of the sewage treatment process.
The DSD's laboratories provide various types of testing services. To enhance laboratory efficiency and reduce human errors, automatic analysers for nutrient test, trace metal elements test and biochemical oxygen demand (BOD) test have been installed in the Shatin Central Laboratory. In addition, the Shatin Central Laboratory was accredited in 1999 for testing environmental samples (water & wastewater) under the Hong Kong Laboratory Accreditation Scheme (HOKLAS) operated by the Hong Kong Accreditation Service of the Innovation and Technology Commission. Having obtained HOKLAS accreditation of BOD test using automatic BOD analyser in 2017, the Shatin Central Laboratory became the first laboratory in Hong Kong to be granted this accreditation. It has also been accredited for tests such as colour and turbidity. To ensure that the laboratory management system can move with the times, the Shatin Central Laboratory is preparing to update the management system to the latest ISO/IEC 17025:2017, which is expected to be completed in June 2020.
In the year under review, up to 32 tests of the Shatin Central laboratory were accredited and more than 242,000 analyses were completed. The results of an analysis of the quality of effluent discharged from major sewage treatment works can be found on our website or retrieved through data.gov.hk.
Construction of Dry Weather Flow Interceptors
Ingress of polluted dry weather flow into the stormwater drainage system does not only impair the quality of water bodies nearby, but also cause an odour problem. To improve the situation, the DSD is constructing an underground dry weather flow interceptor (DWFI) and a pumping station along the seafront of New Yau Ma Tei Typhoon Shelter to intercept and divert the polluted dry weather flow from the Cherry Street box-culvert to Stonecutters Island STW for proper treatment and discharge. In addition, in order to solve the problems of water quality and odour in the coastal areas of Kowloon West and Tsuen Wan, we are constructing eight new DWFIs (four in Tsuen Wan and four in Kowloon West) and carrying out modification works to 39 existing DWFIs in Kowloon West.
Current Progress
Construction works of the DWFI at Cherry Street box culvertin Tai Kok Tsui commenced in December 2017 for completion in 2022. The estimated project cost is about $660 million.
Phase 1 of upgrading works of West Kowloon and Tsuen Wan sewerage commenced in September 2017 and the four DWFIs in Tsuen Wan were completed in September 2019. The remaining works are scheduled for completion in mid-2022. The estimated project cost is about $280 million.
Enhancement Works for Kwun Tong Sewage Pumping Station
To support the local development of East Kowloon, we are carrying out enhancement works for Kwun Tong SPS. The works items include construction of an underground sewage balancing facility with a capacity of up to 16,000 cubic metres, and provision of ventilation and odour control equipment. The roof of the pumping station will also be turned into a landscaped deck to enhance visual appearance of the pumping station and provide an open space of about 11,000 square metres for public enjoyment.
Current Progress
Construction commenced in December 2017 with completion planned for 2022. The estimated project cost is about $1.05 billion. Both Design for Manufacture and Assembly (DfMA) and traditional cast in-situ methods are employed in the project to increase efficiency and shorten the construction period.
Construction of Additional Sewage Rising Main and Rehabilitation of the Existing Sewage Rising Main between Tung Chung and Siu Ho Wan
The existing sewage rising main between Tung Chung and Siu Ho Wan is the only pipe for conveying sewage in the area. It is approaching the end of its design life of 25 years. To meet the increased demand from the development of Hong Kong International Airport and Tung Chung New Town Extension, and to enhance the reliability of the sewerage system, the DSD regularly inspects and rehabilitates the existing sewage rising main, while constructing in parallel another sewage rising main in stages. On completion of these works, the two rising mains are expected to be able to cope with the sewage flows projected up to 2038.
Current Progress
Commenced in August 2016 by phases, the first phase of works includes the construction of a sewage rising main about 6.5 kilometres in length and 1,200 millimetres in diameter and implementing associated connection and ancillary works. The second phase of works is the rehabilitation of the existing sewage rising main. The first and second phases are scheduled for completion in 2022 and 2025 respectively. The total estimated project cost is about $1.36 billion.
Improvement of Village Sewerage
Many villages in Hong Kong are still not connected to public sewerage; some of them are relying on septic tanks to treat their sewage. Sewage from poorly maintained septic tanks may find its way into the stormwater drainage system, posing hygiene problems and polluting nearby water bodies. In view of this, the DSD has been striving to expand the public sewerage systems to village areas over the years to collect their sewage for proper treatment. The DSD is currently carrying out construction of public sewerage for villages in Sai Kung, North District, Kwun Tong, Yuen Long and the Outlying Islands, in a bid to improve hygienic conditions and water quality in rural areas.
Current Progress
As at March 2020, we have laid public sewerage for over 240 villages. At present, the works for around 25 villages are underway while the works for around 245 villages are under planning and design. In the third quarter of 2020, we will commence a project providing sewerage for parts of Sai Kung area to improve their sanitary conditions and the water quality of Port Shelter. This project is scheduled for completion in 2025 at an estimated cost of about $1.2 billion.
Furthermore, we will carry out sewerage works in four unsewered villages or areas in Sha Tin and Tai Po. The project includes building a sewage pumping station in Sha Tin, modifying the existing Tai Po Kau sewage pumping station and laying a total of about 5.6 kilometres of sewers. Works are scheduled to commence in the third quarter of 2020 for completion in the third quarter of 2024. The estimated project cost is about $308 million.
Managing Drainage and Sewerage Networks
The DSD is managing about 4,717 kilometres of stormwater drains and sewers. Some of the underground pipes have been in service for 30 years on average. Over 2,089 kilometres of the pipes have been used for 30 years or longer, with many of them showing signs of wear and tear. Any structural failure of seriously deteriorated pipes may result in soil erosion and even road subsidence, affecting normal operation of the pipelines and bringing adverse impacts on traffic, environment and public safety.
In view of this, in addition to carrying out regular inspections, we are striving to implement a territory-wide risk-based rehabilitation programme for aged stormwater drains and sewers, with surveys and rehabilitation of high-risk underground pipes being conducted in phases. We will also examine and employ various cutting-edge technologies to efficiently maintain our underground pipe networks and enhance the cost-effectiveness of our works.
Rehabilitation of Trunk Sewers in Kowloon, Sha Tin and Sai Kung
To reduce the risk of sewer collapse and sewage seepage and enhance public safety and environmental hygiene through improvement on the reliability of our sewage system, the DSD is carrying out rehabilitation works to four sections of trunk sewers totalling 1.7 kilometres in length, which are located in Ngau Chi Wan, To Kwa Wan, Sha Tin and Sai Kung respectively, as well as constructing about 0.7 kilometres of additional trunk sewers and undertaking related sewage diversion and manhole rehabilitation works in Sha Tin and Sai Kung.
Current Progress
The works commenced in January 2018 and 40% of the sewers have been rehabilitated as scheduled. We are adopting trenchless construction technology and using micro-tunnel boring machines to lay additional sewers. The project is expected to be completed in the first quarter of 2022 at the estimated project cost of about $680 million.
