Advisory Council on the Environment

Report on the 72nd Environmental Impact Assessment Subcommittee Meeting

(ACE Paper 25/2002)
For advice


At its meeting held on 8 July 2002, the Subcommittee considered the following environmental impact assessment (EIA) reports-

     (a) EIA report on Yuen Long and Kam Tin Sewerage and Sewage Disposal Stage 1- Packages 1A-1T and 1B-1T- Kam Tung Trunk Sewerage Phases I and II; and
  (b) EIA report on Permanent Aviation Fuel Facility.


2. Members are requested to advise whether the two EIA reports should be endorsed.


EIA report on Yuen Long and Kam Tin Sewerage and Sewage Disposal Stage 1- Packages 1A-1T and 1B-1T-Kam Ting Trunk Sewerage Phases I and II
(ACE-EIA Paper 11/2002)

Need for the project

3. The proposed works are required to provide adequate infrastructure for sewerage and sewage disposal in North West New Territories to match with the planned development and population. If the proposed works are not implemented, the area will remain unsewered and the absence of proper sewage treatment and disposal facilities would cause untreated sewage to continue to be discharged to watercourse leading to the Deep Bay.

Description of the project

4. The project includes the construction of 10 km of trunk sewers/rising mains and associated pumping stations to transfer sewage from the Kam Tin Core Area to the Yuen Long Sewage Treatment Works. The majority of sewers/rising mains will be constructed along the maintenance access road of the Kam Tin main drainage channel.

Views and recommendations of the EIA Subcommittee

5. Having studied the EIA report and ACE-EIA Paper 11/2002 and after detailed discussion, Members agreed to recommend the EIA report to the Council for endorsement subject to the implementation of all mitigation measures proposed in the EIA report, in particular, the following-

     (a) requirement of the contractors to prepare a Waste Management Plan for approval by the Engineer to ensure proper handling and disposal of wastes arising from the project;
  (b) establishment of a trip-ticket system as one of the contractual requirements to monitor the disposal of construction and demolition materials and solid wastes; and
  (c) erection of fences along the boundaries of pumping station sites to limit the construction activities to be conducted within the exits and prevent dumping of materials in adjacent areas especially fishponds.

EIA report on Permanent Aviation Fuel Facility (PAFF)
(ACE-EIA Paper 12/2002)

Need for the project

6. The existing temporary Aviation Fuel Receiving Facility (AFRF) sited off Sha Chau does not have the capacity to meet the forecast demand for aviation fuel beyond year 2005/2006. The proposed project will replace the existing facility with a permanent one at Tuen Mun Area 38. Thereafter the existing AFRF will be retained in a dormant but ready state as an emergency back-up facility.

Description of the project

7. The project will consist of an aviation fuel farm of a maximum of 12 tanks, a jetty with two berths, a twin submarine pipeline and on-site operational facilities including offices. The fuel tank farm and the twin submarine pipeline constitute designated projects under the EIA Ordinance.

Views and recommendations of EIA Subcommittee

8. Members' concerns on the project related mainly to the operation of the existing facility; methods used for selecting and evaluating the alignment of pipelines; dripping of fuel during vessel discharge of aviation fuel; effect of piling noise on dolphin food source; alternative piling methods; efficacy of the bubble jacket; acoustic decoupling; sediment plume modeling and distribution of water quality monitoring points; safety of the new facility during typhoon; environment management system; mud dredging and compensation for fishermen; cumulative impacts; oil spillage from the tank farm and extension of the period of no piling activity to avoid the calving season.

Operation of the existing facilities

9. On Members' concern about the operation of the existing facility and whether there had been any leakage of fuel and disturbance to marine life, the project proponent team confirmed that there had been no leakage at all during the operation of the facility in the past five years. The dolphin monitoring programme undertaken before, during and after the construction phase has shown that dolphin abundance has returned to pre-construction levels. This indicated that any impacts on the dolphins were short-term.

Methods used for selecting and evaluating the alignment of pipelines

10. Members re-visited the methods used for selecting and evaluating the alignment of the pipelines. The project proponent team explained that they wanted to avoid routing the pipelines through areas which were not feasible, i.e. a route through the contaminated mud pits at East Sha Chau (northern corridor) and a route around the north-east of the airport where there are a number of cables in the seabed (eastern corridor). Placing a pipeline in those locations was undesirable in environmental and engineering terms. Furthermore, in areas where there were a number of submarine cables, the co-existence of fuel pipelines and electrical cables would induce natural corrosion of pipelines thus posing environmental risk. After eliminating eastern and northern corridors, the western corridor was the only area found to be feasible for locating the pipelines. Two pipeline options in the western corridor were assessed in terms of risk and operational effects. The present option was selected because of, inter alia, the smaller quantity of dredging required and a lesser impact on dolphins. The initial selection was qualitative but the two options for the pipelines were assessed by means of a quantitative approach.

Dripping of fuel during unloading

11. On the possibility of minor dripping of fuel during discharge of aviation fuel from vessels, the project proponent team pointed out that although dripping at the discharge connection could occur, there are catch-trays put underneath the connection between the vessel and the jetty to collect dripping and prevent fuel from falling into the sea. Also the smaller number of vessel movements involved in the operation of the new facility, would minimize the frequency of such incidents.

Effect of piling noise on dolphin food source

12. On the effect of piling noise on dolphin food sources (e.g. fish), the project proponent team indicated that this had been taken into account in the EIA. Dolphins also feed on other kinds of marine life such as squid, and these are not as adversely affected by noise impacts as dolphins. The fact that there was no long term impact on dolphin abundance arising from the AFRF project showed that the effect of piling noise on dolphin food sources had been negligible and short term. Otherwise the dolphins would not have returned.

Alternative piling methods

13. The project proponent team pointed out that bored piling was a feasible alternative but using it for the construction of the jetty would take a much longer time from an engineering point of view and might not be preferable over percussive piling in terms of overall environmental impact. To allow the boring equipment to operate, a casing must first be percussively driven into the seabed. In addition, to socket the pile into bed rock would require the use of a chisel which also produced percussive noise impacts. The longer construction period would extend the duration of potential ecological impacts and make it very difficult to avoid the peak calving season.

14. The project proponent team reminded the Subcommittee that the AFRF project had also utilised percussive piling and, before deciding on it, a panel of dolphin experts had been consulted, including an expert on underwater acoustics. They agreed that the benefits of a shorter construction period making use of percussive piling outweighed the disbenefits of additional noise impacts, which could be reduced by mitigation measures.

Efficacy of the bubble jacket

15. Members expressed concern about the efficacy of the bubble jacket, which would be subject to test, in attaining the specified noise attenuation. The project proponent team indicated that the proposed bubble jacket is based on the bubble curtain used during construction of the AFRF but had been modified to overcome problems posed by deep water and stronger currents present near Tuen Mun Area 38. The commitment in the EIA is that the bubble jacket would provide the same, if not better, noise attenuation to that provided by the AFRF bubble curtain. It aimed to achieve at least a 3-5 dB reduction in noise. The design of the bubble jacket would be undertaken at the detailed design stage.

16. Since the detailed design of the bubble jacket would be subject to test, it would not be appropriate to set a more stringent noise target than that specified in the EIA report. The project proponent would, however, try to achieve a better level of noise attenuation and would submit the results of the noise attenuation test to the Subcommittee for information.

Acoustic decoupling

17. A Member pointed out that the barge on which the piling equipment was installed might act as an amplifier for the piling noise. The project proponent team explained that to address this problem, they would insulate the steel frames, generators and all other noisy equipment on the barge so that they were acoustically decoupled. Specific decoupling measures would be worked out in the detailed design stage.

Sediment plume modeling and more water quality monitoring points

18. Having regard to the fish kill in Ma Wan in connection with the Penny's Bay project, a Member expressed concern about the accuracy of the sediment plume modeling. The project proponent team said that they have reviewed the water quality modeling for the Penny's Bay project and considered that the results were reasonably accurate. The team further explained that the accuracy of modeling depended largely on the grid size. With the advance in computing power, a finer grid size has been used and the present modeling would be more accurate than that for the Penny's Bay project. Furthermore, the current movement at Sha Chau area was much less complex than the Ma Wan area and hence the uncertainty would be less.

19. On the number of water quality monitoring points proposed for environmental monitoring and auditing purposes, the project proponent team explained that based on the result of the modeling which showed that the water quality would be within the water quality objectives, no monitoring was in fact required. However, since the project was within a marine park, the proposed monitoring points would target the dredging in the marine park but not along the entire alignment of the pipelines. Also bearing in mind that the dredging work within the marine park would last for only a few days, the proposed number of monitoring points would be sufficient. However, to allay the concerns of a Member, the project proponent agreed to put in more water quality monitoring points.

Operation safety during typhoon

20. On the operational safety of the facility during a typhoon, the project proponent team explained that at or before typhoon signal no. 3 was hoisted, tankers would go offshore and would not stay at berth. Hence, there would be no question of a tanker incident at the PAFF during a typhoon.

Environment Management System

21. The project proponent team said that there are already contractual obligations in place which require the contractor as well as the operator of the facility to put in place an Environmental Management System to ensure that the proposed measures in the EIA report, including the testing of the bubble jacket, would be implemented.

Mud dredging and compensation for fishermen

22. On mud dredging and possible contamination of the fishery resources, the project proponent team indicated that they had worked on a number of projects in the same area and were highly familiar with the level of sediment contamination in the area that would be affected by the pipeline. The sediments to be disturbed by the project were not contaminated. As for the contaminated mud pits at East Sha Chau, a risk assessment on the contaminated mud pits on dolphins and fishery resources had already been undertaken under a different project and the result was that there was no significant risk on fishery resources.

23. On compensation for fishermen, the project proponent team clarified that the project would be gazetted under the Foreshore and Seabed Ordinance, around October 2002. According to the Ordinance, the project proponent, not the Government, would be required to compensate the affected fishermen if necessary. The fishermen would be notified through the Marine Department when dredging took place and the compensation would be arranged through Agriculture, Fisheries and Conservation Department.

Cumulative impacts

24 On cumulative impacts, the project proponent clarified that the Submarine Cable Landing installation project between Tuen Mun and the airport had already been completed. The three reclamation projects in conjunction with the widening of Castle Peak Road would be completed before 2003 whilst the dredging of the present project would not start until 2004. Also, the New Contaminated Mud Marine Disposal Facility at Airport East/East Sha Chau Area would not start until 2006. The conclusion was that an issue of cumulative impacts did not exist.

Oil spillage from the tank farm

25. The project proponent indicated that the tank farm would be bunded so that any fuel spillage would not go outside the tank farm boundary on land.

Extension of the period to avoid full calving season

26. On the point of extending the non-piling period to avoid a longer calving season (April to August) rather than just the peak calving season (April to June), the project proponent pointed out that though actual piling lasted for only 60 days, a lot of preparation work was required before piling. Extension of the period to August would reduce the working time to only seven months and would affect the piling work. Nonetheless, the project proponent agreed to consider the proposal when the works programme was better defined.


27. After detailed discussion, the Subcommittee concluded that it would recommend the EIA report to the Council for endorsement with the following proposed conditions-

     (a) measures should be taken to reduce the underwater piling noise as much as possible and in any case noise should be reduced by 3 to 5 dB. In addition, the results of the bubble jacket noise attenuation trial and test should be reported to the EIA Subcommittee before piling commences;
  (b) the piling and related equipment installed on the piling barge should be acoustically decoupled such that the underwater noise emitted from the hull of the barge would not be higher than that from the percussive piling itself; and
  (c) there should be additional water quality monitoring points during the dredging phase.

Fisheries resource assessment

28. As a separate issue outside the purview of the PAFF project, the Airport Authority agreed to consider the request raised by a Member on the possibility of conducting a fisheries resource assessment covering more than the project area.

EIA Subcommittee Secretariat
July 2002




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