In the light of the experience gained during Stage 1 works, an International Review Panel was set up by the Government, in April 2000, to examine whether the original plans remained the most cost-effective and environmentally friendly means of treating the sewage entering Victoria Harbour.
The panel members presented their report in November 2000. In it they recommended upgrading the treatment of sewage using compact sewage treatment technology. This would then allow treated sewage to be discharged within the Harbour via an existing short outfall.
The panel also gave four options for collecting sewage from Hong Kong Island, and recommended some further trials and assessments to verify the viability of those options.
In 2004, the Government completed the trials and studies on the way forward for HATS which have confirmed that, while the four options should be technically feasible, it would be necessary to provide additional land for the construction of the biological treatment plant.
On 20 November 2004, the Government completed a 5-month public consultation programme on the way forward for the remaining stages of HATS.
Trials and Studies
(1) Environmental and Engineering Feasibility Study (EEFS)
The study was commenced in Nov 2001. The EEFS has confirmed that all the four options by the International Review Panel are environmentally acceptable and technically feasible. Besides, disinfection would also be required to remove the E.coli bacteria in order to reopen the Tsuen Wan beaches.
Among the four options, which mainly differ in the scale of decentralization, the option to centralize treatment for all sewage at Stonecutters Island is the preferred option as it performs the best overall in terms of cost, environmental and engineering aspects. The Study has also concluded that, even if the most compact sewage treatment technology is used in the biological treatment process, all the options would require extra land of at least 12 hectares outside the current boundary of the SCISTW.
(2) Compact Sewage Treatment Technology Pilot Plant Trials
Drainage Services Department awarded three trial contracts to three different technology providers in December 2001, with two employing different designs of the Biological Aerated Filter (BAF) technology and one employing the Submerged Aerated Filter (SAF) technology.
These trials were completed in 2003. The trials have demonstrated that the two BAF systems tested could perform well under local conditions (i.e. high temperature, low pH/alkalinity and high salinity) and meet the prescribed standard. On the other hand, SAF could not perform up to the prescribed standard. The trials have also revealed that the satisfactory operation of the BAF systems would depend heavily on the reliability of the on-line instrumentation and control system5 as well as the technical knowledge and experience of the operators on the respective designs of BAF technology. Therefore, competent / skilled operators would be required to ensure the reliable and stable operation of the BAF plants, in particular, during the start-up of the biological treatment process and emergency incidents.
(3) Study on Procurement Options
The Study was carried out to identify the most efficient and effective procurement arrangement for implementing the further stages of the HATS. The Study, which was administered by Drainage Services Department (DSD), commenced on 21 March 2002 and was completed in end 2006.
Under Phases I and II of the Study, all the possible procurement options for implementing HATS Stage 2 had been reviewed having regard to overseas experience. It was concluded that we should consider using the Design-Build approach to construct underground tunnels as far as possible. As regards the provision of the biological treatment facilities, the Study recommended that we should consider the use of Public Private Partnership, possibly by means of Design-Build-Operate arrangement.
The final phase of the Study, Phase III, commenced in March 2005 after the way forward for the implementation of HATS Stage 2 had been decided following the public consultation exercise held in the second half of 2004. It had developed the consultancy and contract strategies and administration structures for the phased implementation of HATS Stage 2. This last phase had also reviewed the previously recommended procurement options to take into account the fact that the upgrading of SCISTW would now be constructed in two phases. It was concluded that we should consider using enhanced Design-Build approach for both the upgrading of Stonecutters Island Sewage Treatment Works and the associated preliminary treatment works under HATS Stage 2A. Under the enhanced Design-Build approach, the Engineer will complete an outline design and a performance specification, and the contractor will carry out the detailed design and the construction works.
(4) Stage 1 Flow Reassessment Study
This study was prompted by the need to address capacity issues associated with developments in East Kowloon. To determine the capacity constraints of the deep tunnels, a hydraulic model was set up to simulate the sewage flow patterns for the various planning projections provided by the Planning Department for years 2006, 2011, 2016 and “Year X”, (i.e. the year when the projected full development scenario is reached. This envisages a population of 5.2 million in the HATS Stage 1 service area compared with 3.5 million in 2000). The results of the hydraulic model simulations indicate that the existing deep tunnels could handle all the sewage generated by the above projected ultimate population in the HATS Stage 1 catchment. There should be no overflows under dry weather conditions and the sewage overflow to the Harbour due to heavy rainstorms would be very small compared to the volume of sewage handled.
(5) SCISTW Capacity Reassessment Study
As recommended by the IRP, this study is to determine the maximum capacity of the Stage 1 Sedimentation tanks at the SCISTW and the effect of increased flow on the pollution removal efficiency of the SCISTW. The trials have concluded that the maximum flow that could be handled by the sedimentation tanks would be in line with the maximum design flow. By adjusting the flow distribution configuration of the treatment works, the sedimentation tanks were able to handle 10% more flows, but at the expense of a slight deterioration in the effluent quality, which is acceptable.
Consultation with the Key Stakeholders and the General Public
We conducted a five-month public consultation exercise on the way forward for HATS stage 2 between 21 June and 20 November 2004. To enable our key stakeholders to understand the project, we organized a series of in-depth technical briefings, discussion forums and public hearings with a broad spectrum of the community including the Environmental Affairs Panel of the Legislative Council and political parties, advisory committees, District Councils in the Harbour area, professional bodies, academia, special interest groups, and various business/trade organizations. Through these outreach activities, we collected comments from 46 keys stakeholders and 81 written submissions made by individual persons or companies from the community at large. It is clear from the comments received that:
- the community attaches high importance to cleaning up Victoria Harbour as a matter of priority;
- most people support the centralization of treatment of all the Harbour area sewage at Stonecutters Island;
- while some would like to see both stage 2A and 2B implemented in one go, the majority opinion is willing to accept a phased programme given the scale of HATS stage 2, the financial implications, and uncertainty surrounding the future sewage flow build-up;
- there are divergent views on the need for disinfection, and in particular the use of the chlorination-dechlorination process; and
- the community believes that it is worth paying higher sewage charges if the outcome is a cleaner harbour, though many considered it important to take into account affordability in adjusting sewage charges and to consult the public extensively beforehand.
More details are set out in :
- Consultation document (pdf file)
- Consultation report (pdf file)
- Consultation Submissions
- Public Hearing on 6 Nov 2004
The following achievements and events were significant in the development of the HATS Stage 2A.
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