|
|
The water quality impact during the proposed dredging works for installation of submarine gas pipelines has been quantitatively assessed using the Delft3D Model. Suspended solids are identified as the most critical water quality parameter during the dredging operations. The worst-case scenarios for the dredging works have been assessed and adverse water quality impact was not predicted. Nevertheless, the implementation of the appropriate mitigation measures could effectively minimize any potential water quality impacts upon seawater and cooling water intakes. There would be no unacceptable residual water quality impact due to the proposed dredging works. An environmental monitoring and audit programme is proposed to ensure that all the recommended mitigation measures are implemented properly.
A review of the sediment quality data from the marine site investigation indicated that the majority of the marine sediments to be dredged along the proposed submarine gas pipelines were classified as Category L. The total volume of dredged sediment from the construction of the submarine gas pipelines requiring marine disposal was estimated in the engineering design study to be 267,603m3. The volume of dredged sediment suitable for open sea disposal (Type 1) was estimated to be approximately 187,179m3. The volume of contaminated sediment requiring confined marine disposal (Type 2) was estimated to be approximately 76,936m3. The volume of contaminated sediment requiring special treatment or disposal (Type 3) was estimated to be approximately 3,488m3. Allocation of marine disposal sites and all necessary permits would be applied from relevant authorities for disposal of dredged sediment. Project Proponent would obtain confirmation from CEDD/Marine Fill Committee (MFC) on the disposal options before commencement of the Project. With the implementation of the recommended mitigation measures and management procedures in accordance with the requirements of ETWB TCW No. 34/2002, no unacceptable residual impact was predicted.
Waste types generated by the construction activities are likely to include C&D material (from excavation works for construction of the landing points), general refuse from the workforce, and chemical waste from the maintenance of construction plant and equipment. Provided that these wastes are handled, transported and disposed of using approved methods and that the recommended good site practices are strictly followed, adverse environmental impacts is not expected during the construction phase.
The
ecological value of the marine ecological resource was evaluated based on the
results of literatures review and field surveys. It was found that the marine
benthic organisms found
within the dredging area consist of pollution tolerant soft benthos which
are in low diversity and typical
to benthos recorded in poor quality sediments. The
inter-tidal survey confirmed that the Inter-tidal communities
colonizing the artificial seawall at To Kwa
Wan and North Point landing points are common fouling organisms.
For the hard coral communities, low coverage of species Oulastrea crispata was found on sub-tidal habitat of To Kwa Wan
breakwaters. Coral communities of varied coverage and species diversity were
recorded in the coral sites
The temporary loss of marine benthic and
inter-tidal communities is regarded as of low significance owing to the low
diversity and abundance of marine fauna species found in the project area. The
potential impact on water quality was predicted by using water quality
modelling. The results indicated that
the elevation of SS concentration and sedimentation rate are
all within acceptable level around the identified
marine ecological sensitive receivers.
It is
concerned that the dredging activities would bring a certain level of adverse
impact on the coral communities colonizing the To Kwa Wan breakwaters. But the
adverse impact, mainly induced by SS, would be minimized by deployment of a
second silt curtain. Therefore, the potential impact to the hard coral colonies
would be minimized to an acceptable level. The health condition of the coral
communities would be monitored regularly through dive survey in order to
validate the effectiveness of the mitigation measures. In conclusion,
the potential ecological impact arising from construction
of the proposed submarine gas pipelines in
Review of existing information on fisheries resources and
fishing operations located within the Study Area have been undertaken. Although
the submarine pipelines trench to be formed at the seabed is long, the affected
area of fisheries resources is predicted to be temporary and localised to the
works associated with formation of submarine pipelines trench at the seabed as
a result of the “bottom-pull” and dredging operations. Since there was no
records of fish fry production and operation of trawlers within the proposed
works area of the project, impact to fishing activities in the area are not
expected to be significant owing to the small affected area and short period of disturbance during the phasing of works for dredging and installation
of the submarine pipeline. Impact
on future fishing operation is not anticipated as the armour rock will not
protrude above the original seabed level. Ma Wan Fish Culture Zone (approximately 16km apart) and Tung Lung
Chau Fish Culture Zone (approximately 9km apart) are not predicted to be
impacted by either suspended solids elevation, dissolved oxygen depletion or
nutrient elevation as a result of the Project. Impact to the Fish Culture Zones and fisheries due to water quality in
construction phase is not anticipated.
As potential impacts to fisheries resources and fishing operations arising from the formation of the submarine gas pipelines trench at the seabed are predicted to be temporary and localised, they are not expected to cause significant adverse impacts to any fishing grounds or species of importance to the fishery. While no special mitigation measures are required for fisheries resources and fishing activities, water quality mitigation measures recommended are also expected to mitigate impacts to fisheries resources and fishing activities.
A risk assessment
study has been conducted for the relocation of the existing submarine gas
pipeline and the associated facilities. The assessment has considered various
failure causes for towngas leakage. Based on the evaluation of potential safety
impacts, the risk associated with the proposed realigned gas facilities is
considered low. Notwithstanding the low level of risk, risk minimisation
measures have been incorporated into the design to further lower the risk and
safeguard population in vicinity.
Though it can be
concluded that there are no insurmountable risks associated with the
construction and operation of the proposed TKW gas pigging station based on the
risk ranking analysis, a quantitative risk assessment has been conducted by
HKCG. Both the individual risk and
societal risk results for the submarine gas pipelines and the two gas pigging
stations have been found “Acceptable” as per risk guidelines in
Landscape Impact Assessment were conducted to identify landscape baseline, potential impacts on the landscape resources and character areas, evaluate these identified impacts and recommend mitigation measures.
Two landscape resources, LR1 – Marine Area of To Kwa Wan, LR2 – Marine Area of North Point; and four landscape character areas, LCA1 – To Kwa Wan Plain, LCA2 – To Kwa Wan Waterfront Area, LCA3 – North Point Waterfront Area, LCA4 – North Point Urban Group were identified within the landscape assessment area.
As the proposed Project will be implemented in the urbanised areas and have no conflict with the existing landscape resources, potential adverse impacts on either landscape resources or landscape character areas are therefore not anticipated. Mitigation measures are recommended for reducing, offsetting and compensating for impacts during the construction phase. Operation mitigation measures for the two pigging stations are identified for implementation in the approved planning permission applications for the two pigging stations under Section 16 of the Town Planning Ordinance. No unacceptable residual landscape impacts are anticipated.
A baseline review identified no submerged cultural heritage sites within the Study Area. A geophysical survey which covered a 200m corridor along the length of the proposed route of the submarine gas pipelines was conducted. The survey revealed 3 significant sonar contacts located less than 50m from the centre line. However, gas blanking is present across some sections of the study area. At these locations no geophysical survey was obtained and therefore no assessment could be made.
An underwater inspection of the 3 significant sonar contacts located less than 50m from the centre line and an additional 2 between 50 and 60m was conducted. All of the sonar contacts were identified as modern debris. Therefore, there was no indication of submerged cultural heritage. Therefore, no cultural heritage impact arising from marine works of the Project is anticipated at the areas where there is full geophysical survey coverage.
Construction noise impact assessment has been based on a best estimate of the construction sequence and machines inventory.
The potential noise impact that could arise from daytime construction activities of the Project has been evaluated. Construction noise level is predicted at unmitigated scenario with a range from 64 to 77 dB(A). With the use of quiet plant and the movable noise barriers, the construction noise impact can be mitigated to a range of 54 to 71 dB(A) which comply with the relevant noise criteria. The Contractor shall, from time to time, be aware of the noise impacts on the surrounding NSRs through adequate noise monitoring during the works so that adjustments could be made to control the construction noise levels. These requirements shall be triggered by an Event and Action Plan as part of the EM&A which shall be incorporated into the works contract in order to make it enforceable.
Potential air quality impacts arising from the construction and operation of the submarine gas pipelines have been evaluated.
As the number of construction plants involved in the submarine gas pipelines laying activities at anytime on site will be limited, exceedance of AQOs emissions of gaseous pollutants from these construction plants is not anticipated. The number of plants required on site for the construction of the landing points and landmain gas pipeline will also be limited. Dust impact and SO2 and NO2 emissions from plant and site vehicles will be minimal. With the implementation of appropriate dust suppression measures stipulated in the Air Pollution Control (Construction Dust) Regulation, together with proper maintenance of equipment, adverse air quality impact is not anticipated.
No air quality impact is anticipated at the operational phase since there will not have any operational phase emissions.
|
Sensitive Receivers/ Assessment Points |
Impact Prediction Results |
Relevant Standards/ Criteria |
Extents of Exceedances |
Impact Avoidance Measures / Mitigation Measures |
Residual Impacts (After Implementation of Mitigation Measures) |
|
Water Quality |
|
|
|
|
|
|
Seawater Intakes along the
waterfront of |
Predicted SS levels at WSD seawater intakes: 3.5-8.9 (dry season), 4.4-8.2
(wet season); Predicted SS levels at cooling water intakes: 4.6-49.8 (dry season), 5.3-39.3
(wet season); Predicted SS elevations at fish culture zones: 0.0-0.6 (both dry and
wet seasons); Predicted SS elevations at marine ecological sensitive receivers: 0.0-0.6
(dry season), 0.0-0.9 (wet season); The model results indicated
no exceedance of relevant SS
criteria at WSRs was recorded |
WSD Seawater Quality Intake Criterion for SS: <10 mg/l Sedimentation rate at corals: <0.1 kg m-2 per day |
Full compliance would be achieved with the implementation of recommended good site practices |
Use of closed grab dredger during dredging Control the dredging rate to a maximum of 4,000m3 per day and limit to no more than 1 closed grab dredger Deployment of silt curtains at appropriate dredging areas |
No adverse residual impact due to the construction and operation of the submarine gas pipelines is expected |
|
Waste Management |
|
|
|
|
|
|
Water quality, air, and noise sensitive receivers at or near the Project site, the waste transportation routes and the waste disposal site. |
Main waste (Marine Dredged Sediment): The total volume of dredged sediment was estimated to be 267,603m3. Dredged sediment for Type 1 was estimated to be approximately 187,179m3, for Type 2 was estimated to be approximately 76,936m3. Contaminated sediment requiring special treatment or disposal (Type 3) was estimated to be approximately 3,488m3. Other wastes (Chemical, C&D material and general refuse): Chemical waste from maintenance and servicing of construction plant and equipment. C&D material from excavation works for construction of the landing points and landmain gas pipelines. General refuse comprising food scraps, waste paper, empty containers, etc. |
Waste Disposal Ordinance (Cap. 354) Waste Disposal (Chemical Waste) (General) Regulation (Cap. 354) Public Health and Municipal Services Ordinance (Cap. 132) - Public Cleansing and Prevention of Nuisances Regulation Land (Miscellaneous Provisions) Ordinance (Cap. 28) Dumping at Sea Ordinance (Cap. 466) Annex 7 and Annex 15 of the EIAO-TM |
Not Applicable |
Uncontaminated dredged sediment (Type 1) is suitable for open sea disposal at MFC gazetted marine disposal ground. Contaminated dredged sediment (Type 2) shall be disposed at the East Sha Chau Contaminated Mud Pits that is designated for the disposal of contaminated. Contaminated dredged sediment (Type 3) from the To Kwa Wan typhoon shelter requires special disposal arrangements by containment of the sediments in geosynthetic containers Recommendations for good site practices and waste reduction measures has been discussed in Section 4.6 The recommended mitigation measures shall form the basis of the site Waste Management Plan to be developed by the Contractor in the construction stage. |
Residual impact is not predicted |
|
Marine Ecology |
|
|
|
|
|
|
Habitats in intertidal zone
(artificial seawalss and rocky shore), sub-tidal zone (soft-bottom and
hard-bottom habitats) and the marine waters ( Corals at Cape Collinson and Tung Lun Chau (within the Eastern Buffer WCZ), Green Island and Sandy Bay (within the Western Buffer WCZ) and Fish Culture Zones at Tung Lung Chau and Ma Wan. |
Permanent natural habitat loss and temporary disturbances and loss of artificial seawall will be occurred during construction phase. The impacts to the low ecological valued marine benthos and artificial habitats within the dredging and works area are predicted to be of low significant. Indirect disturbance to the remaining hard corals around Kai Tak area is of low significant. |
EIAO – TM and WPCO. |
No exceedances were predicted in marine sensitive receivers. |
The proposed dredging works will be confined in the works area within 25m at either side of the proposed alignment and the use of closed type grab dredger will reduce sediment and contaminants runoff to the water column. |
There will be change in approximately 9.8ha of seabed substrates along the alignment. Benthic fauna is expected to be recolonized to the seabed after construction. No adverse residual impact due to the construction and operation of the submarine gas pipelines. |
|
Fisheries |
|
|
|
|
|
|
Fish Culture Zones at Tung Lung Chau and Ma Wan. |
Impacts to fishing operations during dredging of the seabed and installation of the pipelines are predicted to be localised. Temporary loss of fishing ground is considered to be reversible and short term during the construction period, as the seabed will be backfilled with rock armour and recolonization of benthos and fisheries are expected in the operation phase. |
EIAO-TM and WPCO. |
No exceedances were predicted in marine fish culture zone at Ma Wan and Tung Lung Chau. The increase in SS, DO and turbidity levels will be localized and confined to the works area only. |
The proposed dredging works will be confined in the works area within 25m at either side of the proposed alignment and the use of closed type grab dredger will reduce sediment and contaminants runoff to the water column. |
No adverse residual impact due to the construction and operation of the submarine gas pipelines is expected after the implementation of the proposed mitigation measures to control water quality impacts. |
|
Hazard to Life |
|
|
|
|
|
|
Nearby residential, existing
and planned schools in vicinity Employment population at To Kwa Wan Preliminary Treatment Works, APB Centre, North Point Police Station, Hong Kong and China Gas Limited Building, Eastern Harbour Centre, Harbour Plaza (North Point) Hotel, Wing Wah Industrial Building and Hong Kong Funeral Home. |
The risk associated with the proposed realigned gas facilities
is considered low. |
Gas Safety Ordinance (Cap. 51) Factories and Industrial Undertakings Ordinance (Cap. 59) Occupational Safety and Health Ordinance (Cap. 509) |
N/A |
Risk minimisation measures have been incorporated into the design to further lower the risk and safeguard population in vicinity |
Risk level of the Project to the surrounding public is low and acceptable. |
|
Landscape |
|
|
|
|
|
|
|
No adverse impacts on landscape resources and character areas were identified. |
EIAO-TM. |
N/A |
Avoidance: Pigging station and land gas mains are proposed on existing urbanised land use of low landscape quality to avoid landscape impact; Mitigation: Screening of construction works; Hydroseeding or sheeting of stockpiles; Ensure no run-off into the harbour; screen planting along the perimeter of proposed pigging station at Ma Tau Kok; and use appropriate building materials and colours in built structures Compensation: N/A. |
No unacceptable residual impacts were predicted |
|
Cultural Heritage |
|
|
|
|
|
|
No indication of submerged cultural heritage. |
No cultural heritage impact is anticipated |
EIAO-TM Antiquities and Monuments Ordinance (Cap. 53) Marine Archaeological Investigation Guidelines |
N/A |
N/A |
N/A |
|
Noise |
|
|
|
|
|
|
Residential Uses and School at To Kwa Wan and North Point |
Noise impacts to noise sensitive receivers during the construction phases for laying of gas pipeline during non-restricted hours are predicted especially the works areas close to the residential uses and schools. |
EIAO-TM and NCO |
Construction noise level is predicted at unmitigated scenario with a range from 64 to 77 dB(A). |
Avoidance: Proper working schedule arrangement avoiding construction works carried out during the school period; Mitigation: Use of quiet plant and movable noise barrier. |
The construction noise impact can be mitigated to acceptable levels provided that the mitigation measures implement properly. Construction noise level is predicted at mitigated scenario with a range from 54 to 71 dB(A) which comply with relevant noise criteria. No unacceptable residual impact is predicted. |
|
Construction Dust |
|
|
|
|
|
|
Residential Uses and Schools at To Kwa Wan and North Point |
No significant air quality impact is predicted. |
EIAO-TM and APCO |
No exceedances of criteria is anticipated |
Good site practice. |
No unacceptable residual impact is predicted. |