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Relocation of Sha Tin Sewage Treatment Works to Caverns









 

Updated on 31 December 2014

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. As majority of the area belongs to government land, the relocation project will not require to resume large amount of private lots;
  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?

The feasibility study consultant completed the preliminary assessment on the environmental impacts due to the relocation project during the construction and operation stages. In the investigation and design stage, we will conduct the environmental impact assessment, and propose suitable mitigation measures to ensure the compliance with the relevant requirements.

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 develop the wind rose for the site.

Based on the wind tunnel test data, the feasibility study 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 siting 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, A 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 consultant preliminarily proposed the following odour control measures:

  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.).

We are conducting the environmental impact assessment, including odour impact assessment, and propose suitable mitigation measures to ensure the compliance with the relevant requirements.

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 feasibility study consultant completed the preliminary assessment on traffic impact of the relocation project to the nearby traffic network, in particular A Kung Kok Street. Since A Kung Kok Street is a main route for many buses and mini-buses to/from Ma On Shan area, the consultant preliminarily recommended the following mitigation measures to minimise the additional loading on this road due to construction traffic:

  1. Two temporary traffic management schemes should be further studied in the design stage, including construction of temporary roads to enable the construction vehicles to enter/exit the cavern site directly from/to the high speed road (Ma On Shan Road) so as to minimise the use of A Kung Kok Street; and
  2. Restricting construction vehicles passing through A Kung Kok Street during morning peak hours through site management.

Based on the traffic modeling results, the consultant anticipated that the traffic impact of the additional construction vehicles to the nearby area will be very minimal if the recommended measures are implemented.

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

11.

How long will the construction of the relocation project take?

The cavern excavation works will tentatively take about 4 to 5 years, followed by civil, and electrical and mechanical works and the relevant testing, and subsequently the demolition of the existing Sha Tin Sewage Treatment Works. The whole relocation project is expected to complete in around 10 years.

The consultant has preliminarily explored measures to shorten the construction period (such as early commencement of the advance works, phased relocation, etc.) and formulated the implementation strategies and programme for the relocation proposal. We will review various methods and measures for further shortening the construction period in details during the investigation and design stage.

12.

What is the future land use of the existing Sha Tin Sewage Treatment Works site after relocation?

The Government will aim at a balanced development on the land vacated taking into consideration the social needs. The preliminary idea at present is that the site would be used for housing and other beneficial uses, including community facilities as well as recreation areas such as waterfront promenade, with a view to improving the community and the environment for the sustainable development of Hong Kong.

The Government would undertake a detailed planning and engineering study for the released site at several years before the completion of the relocation project. The planning and engineering study will cover technical and impact assessments on the proposed land use, as well as public consultation.

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.

How will the construction and demolition materials generated from the relocation project be managed?

The feasibility study consultant initially worked out the preliminary management plan for the construction and demolition materials, including making use of the excavated rocks for the construction materials (e.g. aggregates for concrete production or pavement materials), and how to make good use of demolition materials.

In the investigation and design stage, we will formulate the construction and demolition material management plan to ensure the compliance with the relevant requirements.

15.

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.

16.

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.

17.

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.


18.

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 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.

   
 
 
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