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Relocation of Sha Tin Sewage Treatment Works to Caverns









 

Updated on 26 March 2018

1.

What is the purpose of the Public Engagement activities of the relocation of Sha Tin Sewage Treatment Works to caverns?

We wish to maintain close dialogue and share the latest information with the public through the Public Engagement activities. We will collect public opinions and concerns, and work together with the public to enhance the relocation proposal.

2.

How will you make use of my views?

The consultant will collect and compile public views. We will introduce suitable enhanced and innovative elements based on the project situation in response to public concerns, with a view to further improving the relocation proposal.

3.

How can I participate in the Public Engagement exercise?

You may refer to the announcement of the website for the latest details of the Public Engagement activities.

For enquiry, please refer to the following:

Email: enquiry@STSTWinCaverns.hk

Hotline: (852) 3142 2256

Fax: (852) 2827 8700

4.

How can I express my opinions?

You may express your opinions via:

Email: enquiry@STSTWinCaverns.hk

Hotline: (852) 3142 2256

Fax: (852) 2827 8700

Mail:  Drainage Services Department
Sewerage Projects Division
44/F, Revenue Tower
5 Gloucester Road
Wan Chai, Hong Kong
(Please specify “Relocation of Sha Tin
Sewage Treatment Works to Caverns”)


5.

Why do you propose Nui Po Shan of A Kung Kok as site for relocation of the Sha Tin Sewage Treatment Works?

According to the study on “Enhanced Use of Underground Space in Hong Kong” completed by the Civil Engineering and Development Department in March 2011, the preliminarily proposed site for relocation of the Sha Tin Sewage Treatment Works to caverns was Nui Po Shan of A Kung Kok.

Under the feasibility study, a re-confirmation review of the proposed relocation site was conducted. When conducting the review, the feasibility study consultant identified a suitable site adjacent to the existing Sha Tin Sewage Treatment Works.

After the review, consultant confirmed Nui Po Shan of A Kung Kok as the best site for relocation of the Sha Tin Sewage Treatment Works. The methodology and result of the reconfirmation review have been examined by an independent expert panel composed of three professors from the Hong Kong University of Science and Technology. To sum up, Nui Po Shan of A Kung Kok site has the following favourable conditions:

  1. The geology of this area, belonging to hard granite with no obvious weak zones and faults, suits for construction of large caverns most;
  2. In the proximity of the existing Sha Tin Sewage Treatment Works and effluent export tunnel (which transports the treated effluent from the Sha Tin Sewage Treatment Works to Kai Tak River in Wong Tai Sin for discharge), relocating the Sha Tin Sewage Treatment Works to this area will minimize the impact on the upstream sewerage system and the downstream disposal system, thereby minimizing the disturbance to the whole Sha Tin District, reducing the construction and operation costs and shortening the construction period;
  3. The majority of the area belongs to government land;
  4. The community and environment will be enhanced wholly after relocating the Sha Tin Sewage Treatment Works; and
  5. With appropriate measures, the traffic impact near the proposed relocation site arising from the relocation works would be well mitigated.


6.

Will the relocation proposal cause any adverse impact to the surrounding environment?

We have completed the assessment on the environmental impacts due to the relocation project during the construction and operation stages. We will conduct environmental monitoring and audit (EM&A) programme during the construction and operation of the relocation project, and will strictly implement the environmental mitigation measures recommended in the approved Environmental Impact Assessment (EIA) Report and the Environmental Permit (EP). Relevant details can be found in this project website or Environmental Protection Department's website at http://www.epd.gov.hk/eia/register/report/eiareport/eia_2402016/cover.html

7.

Will the relocation proposal affect the effluent export route and the water quality of the Tolo Harbour and the Victoria Harbour?

The existing Sha Tin Sewage Treatment Works is being operated such that the effluent quality will meet the requirements set down in the Discharge Licence issued by the Environmental Protection Department.

Under the current arrangement, the treated effluent from the existing Sha Tin Sewage Treatment Works is conveyed to the effluent export tunnel starting at Nui Po Shan of A Kung Kok and be conveyed to Kai Tak River in Wong Tai Sin for discharge. This arrangement can make use of the flushing effect by the treated, clean effluent from the Sha Tin Sewage Treatment Works, and hence improve the water quality and environment of Kai Tak River. This arrangement will be maintained after relocating the Sha Tin Sewage Treatment Works to caverns.

According to the preliminarily planning of the relocation project, the relocated Sha Tin Sewage Treatment Works will maintain the same effluent quality after relocation. Nevertheless, the Drainage Services Department will keep close liaison with the Environmental Protection Department and the relevant parties to ensure that the effluent quality of the relocated Sha Tin Sewage Treatment Works will meet the planned use of the receiving water body.

8.

Will the relocated Sha Tin Sewage Treatment Works cause any odour issue to the nearby community?

To obtain more reliable wind data for odour impact assessment, the Drainage Services Department engaged the City University of Hong Kong to conduct a wind tunnel test for analysing the wind speed and wind direction at the proposed relocation site (Nui Po Shan of A Kung Kok) and developing the wind rose for the site.

Based on the wind tunnel test data, the consultant completed the odour impact simulation and determined the most appropriate location for the ventilation shaft. The consultant predicted that, through implementing appropriate odour control measures and sitting the ventilation shaft at a remote location on the hill, the air quality at the nearby residential estates / villages (e.g. Chevalier Garden, Kam Tai Court, Ah Kung Kok Fishermen Village, Tai Shui Hang Village, Mui Tsz Lam Village, etc.) will be far below the allowable limit of 5 odour units as stipulated in the Environmental Impact Assessment Ordinance. The relevant odour impact assessment were included in the approved EIA Report. The environmental mitigation measures recommended in the approved EIA Report will be implemented:

  1. Adopting the advantage of caverns as natural barriers for odour control;
  2. Covering up of odour sources;
  3. Preventing odour leakage through the access tunnels by applying negative pressure inside caverns;
  4. Installing deodourising units to clean up the collected foul air;
  5. Discharging exhausted air at height to further enhance the dilution effect; and
  6. Enhancing the odour management of the sludge transportation (including adopting sludge carrying vehicles with enclosed containers, cleaning and drying the surface of the sludge carrying vehicles before leaving the caverns, carrying out regular monthly tests for the enclosed containers to ensure proper functioning, etc.).

9.

Will the sludge carrying vehicles cause any odour issue during operation of the relocated Sha Tin Sewage Treatment Works?

At present, there are about 20 vehicles per day taking sludge away from the existing Sha Tin Sewage Treatment Works. Although the incoming sewage will increase progressively in future, we will adopt advanced treatment technology to maintain the sludge production and hence the traffic volume of sludge carrying vehicles at a similar level. In addition, we will enhance the odour management of the sludge transportation, including adopting sludge carrying vehicles with enclosed containers, cleaning and drying the surface of the sludge carrying vehicles before leaving the caverns, carrying out regular monthly tests for the enclosed containers to ensure proper functioning, etc.

10.

Will the relocation proposal cause any adverse impact to the traffic network nearby?

The consultant has recommended the following mitigation measures in order to reduce the impacts to the nearby traffic as far as possible:

Early Construction Stage
  1. Blasting works will not be commenced in the early stage of the construction, hence the number of construction vehicles is estimated to be low. Construction vehicles will access the temporary construction site and Ma On Shan Road via A Kung Kok Street and access during morning and afternoon peak hours will be avoided;
  2. The construction of the temporary steel bridge requires approximately one year, in which the completion time is anticipated to be same as that of the blasting works, thus aids the transportation of rock materials by construction vehicles.


After the Completion of the Temporary Steel Bridge
  1. Construction vehicles will transport the excavated rock materials via the temporary construction access connecting Ma On Shan Road, temporary haul road and temporary steel bridge to lower the use of A Kung Kok Street;
  2. The Contractor will be required to limit the construction vehicles for transporting the excavated rock materials to access or leave the construction site during morning and afternoon peak hours.

During the investigation and design stage, we shall conduct traffic impact assessment to ensure compliance with the relevant requirements.

11.

How long will the construction of the relocation project take?

The detailed design of the project is currently in progress and we are anticipating to seek funding from the Finance Committee (FC) for the proposed Stage 1 Contract in 2018. Subject to the funding approval of the FC, we plan to commence the proposed Stage 1 Contract in the first quarter of 2019. The remainder of the relocation project mainly comprises the construction of the cavern complex at Nui Po Shan, installation and testing of the sewage and sludge treatment works and associated facilities, construction works for upstream sewerage and pumping stations, and decommissioning and demolition of the existing Sha Tin Sewage Treatment Works. The relocated Sha Tin Sewage Treatment Works is anticipated to commence operation in 2030.

12.

Is there any linkage between the Ma Liu Shui reclamation proposal and the proposal for relocation of Sha Tin Sewage Treatment Works to caverns?

The Ma Liu Shui reclamation proposal by Civil Engineering and Development Department (CEDD) and the proposal for relocation of Sha Tin Sewage Treatment Works to caverns by Drainage Services Department, covering different engineering scopes, are two separate and independent projects. Nonetheless, the land resources released by both proposals initiate a synergy: if Ma Liu Shui reclamation proposal is supported by the public, CEDD will together consider the released lands from the two proposals and formulate an overall development strategies in future planning and feasibility study.

13.

Drill and blast method is adopted for the cavern construction, what is the vibration level of the nearby buildings during the blasting operations?

The consultant completed the preliminary assessment on blasting vibration of nearby buildings / structures since drill and blast method will be adopted for the cavern construction.

Nowadays, the allowable vibration limits for general buildings / structures and sensitive buildings / structures are 25mm/s and 13mm/s respectively. Based on the evaluation results, the predicted vibrations of nearby estates / villages (e.g. Chevalier Garden, Kam Tai Court, A Kung Kok Fishermen Village, Tai Shui Hang Village, Mui Tsz Lam Village, etc.) will be much lower than the above limits. The feasibility study consultant anticipated that the current advanced blasting technology and control measures can effectively mitigate the vibration of nearby buildings to an acceptable level.

The consultant recommended the preliminary mitigation and control measures as follows:

  1. Pre-construction survey will be conducted on the nearby buildings and structures and monitoring points will be set up;
  2. Hoardings will be erected outside the construction site. Noise barriers and other blasting containment will be installed to reduce noise level and withstand blast pressure;
  3. The duration of blasting operations will be short. The blasting operations will be controlled and closely monitored to ensure that the vibration limits are not exceeded; and
  4. Liaison office will be set-up near the cavern site to facilitate enquiry from the nearby residents. Liaison office will also regularly send updated blasting schedules to the nearby estates / villages.

In the investigation and design stage, we will conduct the blasting vibration assessment to ensure the compliance with the relevant requirements.

14.

Will the cavern construction activities and the sewage in the sewage treatment works affect the groundwater?

The groundwater level near the caverns will be monitored during the construction stage to ensure that the surrounding groundwater level will not be affected due to the cavern construction activities and presence of the caverns.

Sewage in the sewage treatment works will be contained in sewage treatment tanks composed of reinforced concrete structures with seepage preventive measures. Therefore, the sewage will not have any direct contact with the rock in the caverns nor cause any groundwater pollution.

15.

Will the design treatment capacity of the relocated Sha Tin Sewage Treatment Works take into account the projected population in Sha Tin?

The design treatment capacity of the relocated Sha Tin Sewage Treatment Works will take into account the projected population in Sha Tin. Nevertheless, if there is any unforeseen substantial increase in sewage treatment demand in future, the relocated Sha Tin Sewage Treatment Works could be expanded by using the underground space to increase the sewage treatment capacity. Compared with the traditional open plan sewage treatment works, the sewage treatment works in caverns could make use of underground space more easily for expansion of the facilities.

16.

Will advanced sewage treatment technology be considered in the relocation proposal?

We are studying potential advanced sewage treatement technologies, such as:

  1. Moving Bed Biofilm Reactor (MBBR);
  2. Aerobic Granular Sludge (AGS);
  3. Sulfate Reduction, Autotrophic Denitrification and Nitrification Integrated (SANI®) Process.


17.

How will you make use of the rock materials from the excavation of caverns?

We anticipate that the rock materials from the excavation of caverns are mainly granites, which are useful construction materials. Part of the granites will be reused on site as road base, drainage layer materials or backfill materials. The remaining granite will be transported to Lam Tei Quarries for processing into aggregates to support other construction projects. On the other hand, moderately and fully decomposed granite will be transported to Tuen Mun Area 38 Fill Bank as backfill materials for other construction projects.

18.

Will the excavation of caverns affect the terrestrial ecology?

The excavation of caverns, similar to tunneling works, will be conducted underground, thus minimizes the ecological impacts to the ground surfaces of Nui Po Shan and the nearby environment.

19.

Will relocation project cause adverse health impacts to the nearby residents?

The risk arising from exposure to toxic air pollutants (TAPs) associated with the emissions of the relocated Sha Tin Sewage Treatment Works is evaluated in our Environmental Impact Assessment Report (as approved by the Director of Environmental Protection). The non-carcinogenic and carcinogenic health impact of the TAPs imposed to the impacted Human Receptors (HRs) were assessed and compared with international guideline levels. It is concluded that the levels of TAPs at HRs were found to be extremely small when compared to the derived reference levels. The highest incremental cancer risk arising from the operation of relocated Sha Tin Sewage Treatment Works is predicted to be 7.1E-08 which is far below the guidance level of 1E-06 adopted by USEPA and it is considered that the relocation project would not present an unacceptable risk to the nearby residents.

   
 
 
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