1. Introduction

1.1 Environmental Impact Assessment (EIA) Study Brief

As stated in the Study Brief, the main objective of the Project is to dredge approximately 5.5 million cubic metres of sediment from the seabed of Kwai Tsing Container Basin, as well as portions of Northern Fairway and Western Fairway, to provide sufficient depth of container basin and approach channel to Kwai Tsing Container Port (KTCP) for the safe navigation of Ultra Large Container Ships (ULCS).

The Project is a designated project under item C.12 of Schedule 2 of the Environmental Impact Assessment Ordinance (EIAO), which encompasses ”a dredging operation exceeding 500 000 m³ or a dredging operation which

a. is less than 500m from the nearest boundary of an existing or planned

i. Site of special scientific interest;

ii. Site of cultural heritage;

iii. Bathing beach;

iv. Marine park or marine reserve;

v. Fish culture zone;

vi. Wild animal protection area;

vii. Coastal protection area; or

viii. Conservation area; or

b. Is less than 100m from a seawater intake point.”

Under section 5(1)(a) of the EIAO, the Civil Engineering and Development Department (CEDD) submitted an application (Application No. ESB-198/2008) for an Environmental Impact Assessment (EIA) Study Brief on 22 October 2008, along with Project Profile No. PP-369/2008. Subsequently, EIA Study Brief No. ESB-198/2008 was issued by EPD on 4 December 2008 for carrying out the EIA for the Project.

An Environmental Impact Assessment (EIA) Study has been undertaken to provide information on the nature and extent of environmental impacts arising from the construction (and future maintenance) of this proposed designated project and related activities taking place concurrently, and to contribute to the decisions on the overall environmental acceptability of the Project.

This Executive Summary provides the key findings contained in the EIA Report, which included the assessment of potential water quality, waste, marine ecology, fisheries, landscape, cultural heritage, noise and construction dust impacts from the construction and operation of the Project, and the recommendations for mitigation measures to ensure compliance with environmental legislation and guidelines.

2. Project Description

2.1 Project Requirements & Programme

The southern portion of Rambler Channel between Tsing Yi and Kwai Chung has been developed into Hong Kong’s primary container shipment port. The nine container terminals, comprising a total of 24 berths which line the east and west sides of the channel, are collectively referred to as the Kwai Tsing Container Port (KTCP), and the waterway within the KTCP is referred to as the Kwai Tsing Container Basin (KTCB). Access for ocean-going container vessels between the KTCB and the main shipping lanes is along the section of the Northern Fairway to the south of Tsing Yi, the Western Fairway and the East Lamma Traffic Separation Scheme (ELTSS).

Developments within the container shipping industry have seen the introduction of ultra-large container ships (ULCS) to the main intercontinental shipping routes. These vessels have a maximum draft of 15.5m. The current average seabed level within the KTCB is approximately -15.6mCD, while depth in parts of the approaches to the KTCB is shallower. Therefore, under this Project it is proposed to deepen the seabed level of the KTCB and its marine access route to provide adequate depth of water to enable the new generation of ULCS to call at the KTCP. The Project layout is shown in Figure 2.1.

The Project’s objective is to lower the seabed in the KTCB and its access fairways and channels so as to maintain an adequate clearance for ULCS at all times. For the purpose of determining the functional least depth of dredging, the maximum draft of an ULCS is taken to be 15.5m. It is recommended in Marine Department’s “The Complete Berthing Guidelines for Port of Hong Kong” that an under-keel clearance of 10% of the maximum draft is provided within manoeuvring basins, sheltered fairways and approaches to berths. Marine Department has also confirmed the applicability of this criterion to the Kwai Tsing Container Basin and its approaches in the Northern and Western Fairways, as well as the East Lamma Traffic Separation Scheme, and advised that the minimum depth to be provided is 17.0m below the lowest astronomical tide, corresponding to a sea bed level of -17.0mCD.

In order to determine the appropriate maintained seabed level, an assessment of the sedimentation rates within the Project area since 1990 has been carried out. The assessment concludes that the potential for sedimentation within the Project area is low. However, it is not known with certainty that the conditions which existed in the period covered by the assessment will prevail for the service life of the KTCP. In order to account for possible increases in the sediment load in the Pearl River Estuary, yet still achieving a sensible balance between capital and maintenance dredging works, a target seabed level of -17.5mCD has been adopted.

In Section 2.2.1 of Port Works Design Manual Part 1, the Chart Datum (CD) is 0.146m below the Principal Datum (PD). As such, the target seabed level will be -17.646mPD.

In addition to the foregoing, modification of the Tsing Yi Submarine Sewage Outfall and demolition of the Kwai Chung Submarine Sewage Outfall are included as part of the scope of works. For the Tsing Yi Submarine Sewage Outfall modification works, this will involve removal of the rock armour, replacement of the existing riser pipes and non-return valves, and followed by re-application of rock armour. Demolition of the Kwai Chung Submarine Sewage Outfall will only involve the dismantling of the pipe section that is above the dredge level. The dredged volume quoted in the Study Brief was 5.5Mm³; however, as the engineering design has progressed in parallel with this EIA, the dredged volume has been refined to be 4.4Mm³. This provides environmental benefit through the reduction in the volume of material to be dredged and disposed of as well as reducing the extent of potential impacts on the receiving water column.

According to the latest estimate, the Project is tentatively scheduled to commence works in the second half of 2011, to be substantially completed within 2 years except for a small area near Container Terminal no. 1 and 5.

2.2 The Study Area and Surrounding Environment

The Kwai Tsing Container Port (KTCP), located in the north-western part of the harbour in the reclamation along Rambler Channel between Kwai Chung and Tsing Yi Island, comprises nine container terminals with 24 berths of 7,804m of deep sea frontage and is operated by five companies, each responsible for maintaining a strip of seabed of approximately 50m wide along the terminals. The Project area includes also a portion of Northern Fairway to the south of Tsing Yi Island and a section of Western Fairway on the west side of Hong Kong Island. In the north western corner inside the container basin, there are two submarine outfalls namely Tsing Yi Submarine Sewage Outfall and Kwai Chung Submarine Sewage Outfall which also fall within the Project area.

2.3 Need for the Project and Consequences of not Proceeding with the Project

The Hong Kong Container Port is the third busiest container port in the world after Singapore and Shanghai, followed by Shenzhen. It is renowned for its efficient cargo-handling operations making it a preferred shipping hub in the region. With the global trend of increasing the size of container ships, the ULCSs to be generated in the near future will have a maximum draft of 15.5m. However, the KTCB and its approach channel are currently being maintained at the depth of about -15.5 mCD with some parts being only at -15.2 mCD.

In the short term, with the trend of the increasing size of container vessels, current container ships occasionally have to wait for high tide to depart from Kwai Tsing Container Port due to insufficient depth of KTCB. Such limitations reduce the efficiency in cargo-handling operations, potentially harm the reputation of Kwai Tsing Container Port and conceivably could encourage vessels to make alternative arrangements including the diversion of traffic to Shenzhen and other Regional ports.

The execution of this Project is therefore necessary to keep the container basin deep enough to maintain current efficiencies and to facilitate the growing size of container ships in the short term. In addition, it is also needed to meet the draft requirement of ULCSs and to maintain the competitiveness of the Kwai Tsing Container Port and Hong Kong as a Regional hub port in the long term. Benefits from this Project are the considerable increase in import and export capacity and the associated economic and social gains for Hong Kong as a whole.

In the absence of this Project, the insufficient depth of KTCB and its approach channel will cause Kwai Tsing Container Port to become less efficient given increased vessel sizes, including the inability to physically berth and accommodate the ULCSs. The long-term development potential of the Kwai Tsing Container Port will inevitably be constrained by the depth of KTCB and its approach channel. International shipping lines will no longer continue to call the Hong Kong Port but turn to Yantian Port or other ports, and in the longer term resulting in a critical loss of shipping trade and declining competitiveness of Hong Kong in the world port economy.

2.4 Consideration of Alternative Construction Methods and Sequence of Work

2.4.1 Do Nothing Scenario

The do-nothing scenario is described in the preceding section 2.3. The current depth of the KTCB limits the efficiency of KTCP and threatens the long term position of Hong Kong as a Regional hub and world class port.

The new generation of ULCS is expected to have a draft of 15.5m. This means that in order for these ULCS to access the container terminals at KTCP, a minimum water depth of about 17m would be required. Current seabed levels thus constrain access by ULCS to tides higher than +1.5mCD. Such restrictions on the permissible access time for ULCS would severely hinder the operational flexibility and efficiency of these container ships, and would be an impractical option for both shipping lines and terminal operators. Consequently, a “do nothing” option is not considered viable for the long term economy of Hong Kong.

2.4.2 Alternative Location

Currently, KTCP is the only port in Hong Kong that contains the facilities which can handle the volumes of cargo associated with the ULCS. Apart from this location, the only other potential location for handling ULCS and their associated cargo would be the proposed Container Terminal 10 (CT10) project at Southwest of Tsing Yi. However, there is no confirmed programme for the CT10 project at this stage, and no certainty that the proposed CT10 project will be able to meet the timeline required for the arrival of the ULCS. Encouraging shipping to migrate to alternative locations, external to Hong Kong, would not be conducive to the role of KTCP as a Regional hub and a world class port.

2.4.3 Alternatives to Treatment and Disposal of Dredged Sediment

Other than conventional dredging and disposal of dredged material, consideration has been given to the potential for reuse of the dredged material in order to minimise the volumes of sediment requiring disposal, based on the nature of sediment including moisture content and level of contamination. Reuse of the sediment as landfill cover is not possible as sediment is not accepted at landfill sites in Hong Kong. Reuse of dredged material in reclamation or public fill is also not recommended as the sediment would require significant treatment (in-situ and ex-situ treatment including dewatering or decontamination, etc) before it could be suitable for use as fill material. As part of this Project, a number of alternative sediment treatment options have been considered to assess the feasibility of reusing of sediment from the Project. As the purpose of the Project is to provide sufficient depth for the ULCS, only ex-situ treatment options were considered.

Treatment options which have been considered include mechanical dewatering, physical separation, brick making, bioremediation, chemical treatment, stabilisation and thermal treatment. The viability of these treatment methods are summarised below, with further details of these methods provided in Chapter 4 of the EIA Report.

Mechanical dewatering - considered inappropriate for this project due to the slow nature of the process and the additional implications resulting from the generation of contaminated water. Disposal of remaining residual sediment still has to be resolved.

Physical separation - effective only for sandy material and would not be suited to the clay based nature of the sediment arising from the Project.

Brick making – similar to physical separation, the nature of the dredged sediment would be unsuitable for brick making.

Bioremediation – this method would be effective for organic contaminants, but not for heavy metal contaminants, hence its applicability would be restricted.

Chemical treatment – this method is contaminant-specific, and would not be suitable if a wide range of contaminants is identified.

Stabilisation treatment - involves binding the contaminants to prevent their release, however, this type of treatment may not be sufficient to ensure the sediment acceptable for reuse, nor will this method reduce the volume of sediment that requires disposal, therefore this option is not considered appropriate for this Project.

Thermal treatment – this option would lead to other adverse environmental impacts as well as requiring extensive pilot testing and an additional environmental impact assessment to be conducted.

The above summary shows that it is difficult to identify a practical treatment method for the dredged material that would be generated by this Project. Other constraints include limitation of the Project programme, need to minimise disturbance to the KTCP operations as far as possible, land-take requirements, environmental consequences of treatment methods, disposal of residual material and viability of reuse options. It was concluded after detailed study that these options would not be feasible especially given the volume of material to be treated.

An alternative option involving the creation of an artificial island to dispose of the dredged material would have been considered if there was reclamation associated with this Project. The practicalities of coordinating with other reclamation projects, unrelated to this Project, may still be considered by the future Contractor if timing, programme, contractual and environmental management arrangements could be coordinated. However, the risks associated with such arrangements are high. To ensure a secure outcome for the project, disposal of the dredged material is therefore the recommended option.

2.4.4 Dredging Programme

The current dredging programme is tentatively stated as being between 2011 and 2013 to allow the KTCP to receive ULCSs by 2013. In order to meet this deadline, it is envisaged that 24-hour dredging operations will be required. In order to avoid disruption to the operation of the KTCP and to maintain safe marine access, dredging operations have to take into account movements of marine traffic as well as environmental considerations. On the environmental side, the dredging programme has considered the effect of other concurrent projects in the vicinity of the Project as well as projects involving dredging which are farther away but which could potentially have a “cumulative effect” on this Project.

It is currently envisaged that implementation of the dredging works will involve the simultaneous use of dredgers in the Western Fairway, Northern Fairway and the KTCB i.e. a maximum of 3 dredgers at any one time. Consideration has been given to ensure that potentially conflicting demands of vessel traffic and dredging works are resolved through deliberation of, inter alia, marine traffic, types of dredgers and environmental factors.

It was also seen that within the Project area, a hot spot was found near Container Terminal no. 1 and 5 (S2). As such, it would be prudent to isolate S2 to a later stage such that the majority (c. 99%) of the navigational (i.e. capital work) dredging can proceed without affecting the overall construction programme. Scientific research indicates that dredging in the dry season where the sea water temperature is relatively lower compared to the wet season can help in controlling the release of unionized ammonia (UIA) as this is temperature dependent. This approach is especially appropriate for dredging at the hotspot area to minimize the impact in terms of UIA on water sensitive receivers.

2.4.5 Conventional Dredging Method

As part of the detailed engineering studies associated with this Project, it has been identified that equipment which could be deployed is constrained by a number of factors including: the layout and seabed composition (material to be dredged) of the KTCB; need to maintain undisrupted operation of the KTCP during the dredging works; programme; and need to avoid adverse environmental impacts.

The nature of the material is one of the key factors determining the equipment to be used for dredging. Initial ground investigations indicated the presence of soft marine deposits over the majority of the Project area. Subsequently, additional detailed investigations revealed some harder materials at a small area in the north-eastern (NE) corner of the KTCB.

Characteristics of the materials to be dredged define the options available for dredging plant, such as, trailer suction hopper dredger, or cutter suction dredgers or grab dredgers. The most commonly used types of dredger in Hong Kong are the trailer suction hopper dredger (TSHD) and the grab dredger (GD). The TSHD is more manoeuvrable than the GD, and with a comparatively higher production rate. While the dredging work can be undertaken at a faster rate with a TSHD, there are, however, higher consequential environmental impacts associated with this option, particularly due to the practice of “overflowing”, whereby the TSHD allows supernatant water pumped aboard to overflow back into the sea. However, “overflowing” is not permitted in Hong Kong during loading or transporting of materials and thus the efficiency of the TSHD is reduced.

The GD generally results in smaller environmental impact compared to the other types of dredger, especially when fitted with a frame-type silt curtain. However, a GD operates in a stationary mode and is slower to manoeuvre, when compared to TSHD.

In Hong Kong, the use of TSHD is not permitted to dredge contaminated spoil. On the other hand, grab dredgers can perform relatively accurate removal of sediment, simply by adjusting the location of the dredger and the depth of grabbing, and hence, is the accepted technique when there is a need to handle contaminated sediment. Investigation of the sediment quality under this Project has identified an irregular distribution of contaminated and uncontaminated sediment within the zones to be dredged (refer to Chapter 4 on Waste Management of the EIA Report). As such, it would not be practical to deploy the TSHD to handle only the uncontaminated spoil. For this reason, grab dredging is preferred over TSHD.

Findings of the Marine Traffic Impact Assessment (MTIA) (completed under Agreement No. CE 63/2008) indicate that dredging works within the KTCB and its approaches using either multiple grab dredgers or TSHDs will not result in unacceptable marine traffic impacts. However, the busy nature of the marine environment at KTCB requires that appropriate management measures be implemented and that in-field conformance to high standards of safety management be maintained.

As mentioned earlier, some hard material was found within the NE corner of the KTCB. Such material may not be readily removed by GD, and may require the use of a cutter suction dredger (CSD). The potential environmental impacts of a CSD are limited to the generation of sediment plume in the immediate vicinity of the stationary CSD whilst in operation. A CSD’s operation is very localized when engaged in the removal of hard materials with large particle size, and therefore, associated environmental effect will be limited to a small area.

Other types of dredger, such as bucket ladder dredgers and backhoe dredgers, have not been commonly used in Hong Kong. These dredgers are not known to provide operational advantages over grab dredgers, and hence, have not been considered further.

2.4.6 Keyhole Dredging Method

2.4.6.1 Dredging Methodology

This innovative technique was investigated in Holland between 2003 and 2005 as a possible means to extract sand from the below layers of overburden without removing the overburden. It involves the insertion of a hollow tube into the material to be extracted, loosening of the material with water jets and then pumping the slurried material to the surface through the tube. The tube traverses around the central insertion point in a series of elliptical loci which trace out in plan the image of a petalled flower, centred on the insertion point. The seabed material remains in place (though is disturbed to some degree by the process) and the level of the sea bed drops in proportion to the volume of material which has been extracted. The process is repeated at centres which are determined by the radius of the treated zone (estimated to be about 2m to 3m, depending on the plant used), such that the tips of the “petals” at adjacent insertion points are approximately contiguous. Production rates of 150m³ of material extracted per hour have been reported, which is comparable to the rates achieved by grab dredging.

Keyhole dredging has not been proven to be successful on the scale demanded by this Project and adverse environmental impacts are likely. The method would have a greater impact on marine traffic in the basin and fairway than conventional grab dredging, with increased risks of collision and loss-of-life potential. In the light of the foregoing discussion, the use of keyhole dredging is considered to be not feasible for this Project and was not recommended for further consideration. As such, convention dredging is selected as the preferred option for this Project.

2.5 Selection of Preferred Option

2.5.1 Dredging Equipment

In selecting the preferred dredging option, consideration has been given to aspects including technical feasibility, environmental acceptability, public interest and the findings from the Marine Traffic Impact Assessment (MTIA). The benefits and disbenefits of different dredging options which are relevant to this Project are summarised as follow:

Table 2.1: Benefits and Disbenefits of Dredgers which could be used for this Project

Dredging options	Benefits	Disadvantages
Using grab dredger (Typical dredging rate: 4000 m³ / 24 hours)	· Least amount of sediment release, therefore have a lesser environmental impact · Fixed position so other vessels can plan movements around the working area · Silt curtain can be applied around the dredging area to reduce the dispersion of the sediment plume · Relatively small operating area · Accurate dredging	· Slower rate of production
Using cutter suction dredger (Typical dredging rate: 700 m³/hour)	· Enables excavation of hard materials · Faster production rate than grab dredger (if overflowing is not a constraint) · More maneuverability than grab dredger	· More marine sediment produced by volume due to high water content · Silt curtain cannot be applied in this Project due adverse impact on shipping in the KTCB and its approaches. Frame type silt curtain cannot be used
Using trailer suction hopper dredger (Typical dredging rate: 7200 m³/24 hrs)	· Easy to manoeuvre as the dredger is self-propelled · Potentially higher rate of production	· More marine sediment produced by volume due to high water content · Movement of suction pipe and draghead causes turbidity and resuspension of sediment, resulting in more significant environmental impact · Overflow will not be permitted from hopper during loading to avoid causing sediment resuspension; this will have a major negative impact on the productivity of the TSHD and could render the method not feasible in terms of programming · Silt curtain cannot be applied for this Project due to constraints including those of marine traffic · Operation interferes with other marine traffic

Dredging options

Benefits

Disadvantages

Using grab dredger

(Typical dredging rate: 4000 m³ / 24 hours)

· Least amount of sediment release, therefore have a lesser environmental impact

· Fixed position so other vessels can plan movements around the working area

· Silt curtain can be applied around the dredging area to reduce the dispersion of the sediment plume

· Relatively small operating area

· Accurate dredging

· Slower rate of production

Using cutter suction dredger

(Typical dredging rate: 700 m³/hour)

· Enables excavation of hard materials

· Faster production rate than grab dredger (if overflowing is not a constraint)

· More maneuverability than grab dredger

· More marine sediment produced by volume due to high water content

· Silt curtain cannot be applied in this Project due adverse impact on shipping in the KTCB and its approaches. Frame type silt curtain cannot be used

Using trailer suction hopper dredger

(Typical dredging rate: 7200 m³/24 hrs)

· Easy to manoeuvre as the dredger is self-propelled

· Potentially higher rate of production

· More marine sediment produced by volume due to high water content

· Movement of suction pipe and draghead causes turbidity and resuspension of sediment, resulting in more significant environmental impact

· Overflow will not be permitted from hopper during loading to avoid causing sediment resuspension; this will have a major negative impact on the productivity of the TSHD and could render the method not feasible in terms of programming

· Silt curtain cannot be applied for this Project due to constraints including those of marine traffic

· Operation interferes with other marine traffic

Table 2.2 below provides a summary of the aspect considered in identifying the preferred dredging option

Table 2.2: Selection of Preferred Dredging Option

	Dredging Method
Aspects Considered	GD	CSD	TSHD
Disturbance to marine traffic	Moderate	Least	Least
Loss Rate of SS	Least	Moderate	Most
Manoeuvrability	Least	Moderate	Moderate
Accuracy	Most	Moderate	Least
Speed of Work (production rate)	Slow	Slow¹	Slow^{^[1]}
Ease of mitigation of impact of elevated SS in the KTCB	ü	x	x
Removal of hard material	X	ü	x
Removal of Contaminated sediment	ü	x	x
Removal of Uncontaminated sediment	ü	ü	ü
Protection of water quality at Fish Culture Zones	ü	ü	x
Protection of water quality at Bathing Beaches	ü	ü	x
Public Option and perception	ü	x	x
Preferred Dredging Option	ü	ü	x

Given the aforementioned findings and considerations, the grab dredger has been identified as the preferred equipment for dredging, as it is able to meet the technical requirements while limiting the environmental impacts. Since grab dredgers are not effective in the removal of hard material, a CSD is likely to be needed to carry out dredging at the NE corner of KTCB dredging area. The estimated volume of hard material that will require excavation is approximately 92,000 m³. Since the hard material forms a very small component of the entire dredging operation (accounting for approximately 2% of the dredged material), the choice of CSD is not likely to significantly alter the overall environmental impacts associated with the Project. Nonetheless the impacts associated with both dredgers have been assessed in the subsequent sections of the EIA.

2.5.2 Dredging Rationale

Owing to the distinctive nature of this Project, considerations have been given to balancing the Construction Programme, Marine Traffic Impact and Environmental aspects to determine which is the most favourable dredging rationale for this Project. In achieving this balance, the first principle is ensure the outcome fulfils the needs of the Project, i.e. that the dredging operation can be undertaken within the anticipated programme. At the same time, the environmental and marine traffic issues have been taken into account such that proposed activities will not result in unacceptable levels of environmental impact and will minimise obstruction to the operation of the container terminals.

Taking into account the foregoing, it was calculated that a maximum of three grab dredgers would be able to complete the dredging operation within the programme of this Project without compromising the environment and marine traffic (a separate report has been prepared under this Project relating to the Marine Traffic Impact Assessment). Due to the presence of hard material in the NE corner of the container basin, a CSD is likely to be deployed to remove hard material in that area.

2.6 Existing Submarine Outfall within Kwai Tsing Container Basin

The Project will also involve modification of the Tsing Yi Submarine Sewage Outfall and dismantling of the abandoned Kwai Chung Submarine Sewage Outfall, such that these outfalls will not pose any hazard to future marine traffic after the lowering of KTCB’s seabed.

In order to conform to the target seabed level, the existing riser pipes for the Tsing Yi Submarine Sewage Outfall will be cut down to a level below -18.9mCD. Tailor-made collars will be adopted to connect the existing riser pipes to the new non-return valves. Immediately after the modification works, the outfall and riser pipes will be protected by rock fill and rock armour. It is understood from DSD that the Tsing Yi Submarine Sewage Outfall was originally designed for continuous screened sewage discharge to the sea. Upon the commissioning of HATS Stage 1 system in 2001, the outfall changed to serve as an emergency by-pass just in case of the failure of HATS's tunnelling system.

The Kwai Chung Submarine Sewage Outfall will be demolished by chiselling, which is localised in terms of the resulting impact and is unlikely to release suspended solids (SS) or other materials to the receiving environment. As only approximately half of the outfall is above the target seabed level of -17.5mCD, this top half of the concrete pipe will be demolished, and material will fall into the bottom half of the pipe rather than being removed.

Based on the above, there is insignificant environmental impact in terms of water quality or waste management associated with the modification and dismantling of the two submarine sewage outfalls. Particular on the Tsing Yi Submarine Sewage Outfall, the modification works do not in any way modify its performance and result in addition of pollution loading to the environment.

2.7 Need for Maintenance Dredging

The following information has been used to identify the changes in seabed levels for assessing the sedimentation rate within the works area in the Kwai Tsing Container Basin, and its approach channels in the Northern and Western Fairways:

a. Hydrographic data provided by the Marine Department for bathymetric surveys carried out in the Study Area as follows:-

i. Northern Fairway and Container Basin – annual records 2000 to 2009;

ii. Western Fairway – 1999, 2002, 2004, 2006 and 2008.

b. Dredging histories obtained from the Port Works (previously Technical Services) Division of the Civil Engineering Department and Marine Department on removal of high spots in local locations during development of the Container Terminal CT9.

c. Bathymetric survey completed in November 2009 under this Project.

The computer software “Surfer” was used to analyse the changes in seabed levels through the generation of “sedimentation isopachytes” by subtracting contours of successive survey data to identify zones of sediment accumulation within the Study Area.

Additionally, the Container Terminal Operators (CTOs) are reported to have been undertaking maintenance dredging within the berth boxes. From the information provided, a “worst credible” maintenance scenario has been developed, based on the highest annual maintenance dredging volumes attained by each of the operators over the past ten years. In arriving at an annual maintenance dredging volume of 225,000m³, volumes of capital dredging to lower the sea bed within berth boxes have been ignored, as these are not considered to be maintenance dredging. Furthermore, where dredging intervals at particular terminals exceed one year, the dredged volume is divided by the interval to provide an estimate of the annual volume. The value includes an allowance of 30,000m³, being the estimated annual volume of maintenance dredging undertaken by the Port Works Division (PWD) of CEDD and as notified by PWD accordingly. It is considered that the aggregate volume of maintenance dredging thus derived is conservative, yet appropriate for inclusion in the assessment of Water Quality and Waste in Sections 3 and 4 of the EIA Report.

2.8 Interface with Planned Projects

This Project is tentatively scheduled to commence in the second half of 2011, to be substantially completed within 2 years except for a small area near Container Terminal no. 1 and 5. The following projects have been identified as potentially concurrent projects. Some of the projects described below could have dredging activities which overlap with this Project and could thus cause cumulative effects. Details of the construction programmes and descriptions of the Project works were investigated from which relevant projects were selected for inclusion in the assessments under this EIA. Details of the overlapping projects and activities are contained in Section 2.8 of the EIA Report.

Table 2.3: Potential Interface with Planned Projects

Interface with Planned Projects
1. Construction of Container Terminal No.10 (CT10) in Southwest Tsing Yi
2. Proposed dredging for marine sand at South of Tsing Yi
3. Marine borrow and dumping areas at South Tsing Yi
4. Proposed laying of submarine cable between Kennedy Town and Outlying Islands
5. Proposed submarine cable from Tong Fuk to Chung Hom Kok
6. Dredging operations and seawalls modification works carried out by the container terminal’s operators
7. Wan Chai Development Phase II and Central – Wan Chai Bypass
8. Shatin to Central Link – Cross Harbour Section (Phase II – Hung Hom to Admiralty)
9. Installation of Submarine Gas Pipelines and Associated Facilities from To Kwa Wan to North Point for former Kai Tak Airport Development
10. Tuen Mun – Chek Lap Kok Link (TM-CLKL)
11. Hong Kong – Zhuhai – Macao Bridge (HZMB) – Hong Kong Link Road (HKLR)
12. HZMB Hong Kong Boundary Crossing Facilities (HKBCF)
13. Lantau Logistics Park
14. Backfilling North Brothers Marine Borrow Area
15. Existing Dredging/ Filling of the Contaminated Mud Pits in East Sha Chau
16. Proposed Dredging works of the Contaminated Mud Pits in South of Brothers

3. Environmental Impacts

3.1 Water

3.1.1 Assessment Scope and Criteria

The water quality assessment has been conducted in accordance with the requirements of the Study Brief and Annexes 6 and 14 of the EIAO-TM. The criteria used for evaluating the water quality impacts include: the EIAO-TM; Water Quality Objectives for the Victoria Harbour, Western Buffer and Southern Water Control Zones (WCZ); Water Supplies Department’s Water Quality Criteria (for flushing water); various water quality criteria for cooling water intakes belonging to MTRC and EMSD; AFCD’s suspended solid criteria for benthic organisms and fish culture zones. The following tables present two sets of the major criteria listed above.

Table 3.1: Summary of Water Quality Objectives

Parameters	Victoria Harbour WCZ	Western Buffer WCZ	Southern WCZ
Dissolved Oxygen (DO) (bottom)	Not less than 2.0 mg L^-1 for 90% of samples	Not less than 2.0 mg L^-1 for 90% of samples	Not less than 2.0 mg L^-1 for 90% of samples
Depth-averaged DO	Not less than 4.0 mg L^-1 for 90% of samples	Not less than 4.0 mg L^-1 for 90% of samples (Not less than 5.0 mgL^-1 for 90% of samples for fish culture subzones)	Not less than 4.0 mg L^-1 for 90% of samples (Not less than 5.0 mgL^-1 for 90% of samples for fish culture subzones)
pH	To be in the range of 6.5 - 8.5, change due to waste discharge not to exceed 0.2	To be in the range of 6.5 - 8.5, change due to waste discharge not to exceed 0.2	To be in the range of 6.5 - 8.5, change due to waste discharge not to exceed 0.2
Salinity	Change due to waste discharge not to exceed 10% of natural ambient level	Change due to waste discharge not to exceed 10% of natural ambient level	Change due to waste discharge not to exceed 10% of natural ambient level
Unionised ammonia	Annual mean not to exceed 0.021 mg L^-1	Annual mean not to exceed 0.021 mg L^-1	Annual mean not to exceed 0.021 mg L^-1
Temperature	Change due to waste discharge not to exceed 2^oC	Change due to waste discharge not to exceed 2^oC	Change due to waste discharge not to exceed 2^oC
Suspended solids	Waste discharge not to raise the natural ambient level by 30% nor cause the accumulation of suspended solids which may adversely affect aquatic communities	Waste discharge not to raise the natural ambient level by 30% nor cause the accumulation of suspended solids which may adversely affect aquatic communities	Waste discharge not to raise the natural ambient level by 30% nor cause the accumulation of suspended solids which may adversely affect aquatic communities
Nutrients	Annual mean depth-averaged total inorganic nitrogen not to exceed 0.4 mg L^-1	Annual mean depth-averaged total inorganic nitrogen not to exceed 0.4 mg L^-1	Annual mean depth-averaged total inorganic nitrogen not to exceed 0.1 mg L^-1
Toxicants	Not to be present at the levels producing significant toxic effect	Not to be present at the levels producing significant toxic effect	Not to be present at the levels producing significant toxic effect

Table 3.2: WSD’s Water Quality Criteria for Flushing Water at Sea Water Intakes

Parameter (in mg L^-1 unless otherwise stated)	Target Limit
Colour (HU)	< 20
Turbidity (NTU)	< 10
Threshold Odour Number (odour unit)	< 100
Ammonia Nitrogen (NH₃-N)	< 1
Suspended Solids (SS)	< 10
Dissolved Oxygen (DO)	> 2
5-day Biochemical Oxygen Demand (BOD₅)	< 10
Synthetic Detergents	< 5
E. coli (no. per 100 mL)	< 20,000

Note:

(1) This criteria has been taken as reference when assessing water quality at flushing water intakes. Note that not all parameters were taken for the assessment.

(2) The WSD criteria has been used as it more stringent than EMSD Code of Practice for Water-cooled Air Conditioning System in terms of suspended solids

(3) No E.coli. has been detected in sediment samples taken for the Project. Insignificant E.coli impact is therefore anticipated

3.1.2 Impact Assessment

Water quality assessments were undertaken to assess the effects of dredging on the receiving environment in terms of SS, and other water quality parameters of significance to water sensitive receivers. Key water sensitive receivers identified include fish culture zones, beaches, coral communities, Water Supplies Department’s (WSD’s) flushing water intakes and the Electrical and Mechanical Services Department (EMSD’s) cooling and flushing water intakes (Figure 3.1). The water quality impact during the proposed dredging works was quantitatively assessed using the Delft3D Model.

The water quality impact during construction and operational phase of the Project has been assessed. The impacts of the proposed dredging works have been quantitatively assessed using the Delft3D Model. Suspended solids were identified as the most critical water quality parameter during the dredging works. Different scenarios including worst-case scenarios and a scenario with concurrent projects for dredging works have been assessed and their acceptability in terms of comparing the predicted results with various standards is provided in Table 3.3. No adverse water quality impacts were predicted at any identified WSRs, including bathing beaches, coral communities and Fish Culture Zones (FCZ). At the seawater intakes the standards were exceeded due to elevated background levels of Suspended Solids (SS) concentrations. The background levels, without the effects of this Project, already exceeded the standards and thus any additional SS concentration from this Project would only exacerbate the issue.

Table 3.3: Summary of Predicted SS for all Scenarios

	Gazetted Beaches	Corals	Fish Culture Zone	Cooling Water Intakes	Flushing Water Intakes
Subject Project Only
Dry Season
Maximum SS elevation (mg L^-1)	1.1	0.9	0.8	12.7	13.5
Exceedance	No	No	No	No	Yes
Wet Season
Maximum SS elevation (mg L^-1)	0.9	2.9	0.5	11.3	11.4
Exceedance	No	No	No	No	Yes
Concurrent Projects included
Dry Season
Maximum SS elevation (mg L^-1)	1.8	1.0	2.6	12.7	13.5
Exceedance	No	No	No	No	Yes
Wet Season
Maximum SS elevation (mg L^-1)	1.6	3.7	2.0	11.3	11.4
Exceedance	No	No	No	No	Yes

* For cooling water and flushing water intakes, maximum SS levels are shown

Based on the predicted results, increases in Suspended Solids (SS) concentrations at some WSD flushing water intakes are anticipated. However, provided suitable mitigation measures are applied e.g. installation of a frame type silt curtain around the grab dredger and a silt screen at seawater intake locations, compliance with the WSD criterion can be achieved.

The impact on bathing beaches was analysed and the conclusion drawn was that the beach water quality would be unaffected by this Project. The effects of dredging on the HATS outfall were assessed and was found to be negligible. The changes to the dispersion and dilution characteristics of the Tsing Yi Submarine Sewage Outfall were confirmed to be negligible. During the operation phase maintenance dredging will be required. The scale of this work is significantly less than for capital dredging works and this will be acceptable in terms of water quality at all WSR’s except the seawater intakes. The non-compliance at these intakes is due to elevated SS concentrations in the marine waters. However suitable mitigation measures will ensure compliance.

From the assessment of S2 alone, in terms of UIA the annual average UIA values are exceeded at the beaches at Approach, Ting Kau, Lido and Casam compared with WQO UIA annual mean criteria. Only the Approach Beach has UIA value higher than 0.021 mg/L in the wet season, whilst all the gazetted beaches except for Tung Wan, Ma Wan, Lo So Shing and Hung Shing Yeh are affected by UIA in the dry season (i.e. > 0.021 mg/L) with values ranging from 0.025 mg L^-1 to 0.190 mg L^-1. A comparatively smaller number of the other sensitive receivers such as cooling water and flushing water intakes were also predicted to exceed the UIA criterion with values ranging from 0.105 mg L ^-1 to 0.221 mg L ^-1. Based on the assessment of S2 alone, it is considered to be prudent to isolate S2 as mitigation measure in order not to affect the overall construction programme.

3.1.3 Mitigation Measures

3.1.3.1 Construction Phase

Dredging

The non-compliance of WSD’s SS criterion at the flushing water intakes WSD1, WSD8, WSD9 and EMSD1 is due to the non-compliance of ambient SS levels at the Rambler Channel and waters near Tsuen Wan. Deployment of silt screens at the flushing water intakes WSRs WSD1, WSD8, WSD9 and EMSD1 was recommended to minimise the predicted elevation in SS levels at the four WSRs.

The implementation of silt screens at the flushing water intakes would reduce the SS level by 60%. The SS reduction factor has been adopted in the previous approved EIA studies. The surface SS levels at the seawater intakes WSD1, WSD8, WSD9 and EMSD1 after the implementation of silt screen were presented in Table 3.4. The SS concentrations at these WSRs comply with the WSD’s SS criterion.

Table 3.4: Maximum Surface SS Levels (mg L^-1) with Silt Screen

WSR	Scenario 1		Scenario 2		Scenario 3		Scenario 4		Scenario 5		Scenario 6		Scenario 7
	Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet	Dry	Wet
Surface
WSD1	5.4	4.6	5.4	4.6	4.7	4.3	5.4	4.6	5.4	4.6	5.0	4.6	4.8	4.4
WSD8	4.8	4.3	4.8	4.3	4.6	4.2	4.9	4.3	4.9	4.3	4.8	4.3	4.7	4.3
WSD9	4.2	1.8	4.2	1.8	4.3	1.8	4.2	1.8	4.1	1.8	4.2	1.8	4.5	2.1
EMSD1	4.6	4.4	4.6	4.4	4.5	4.2	4.6	4.5	4.6	4.5	4.6	4.4	4.5	4.2
Depth-averaged
WSD1	6.1	8.1	6.1	8.1	5.1	6.3	6.1	8.2	6.1	8.2	5.8	8.2	5.2	6.5
WSD8	5.3	6.7	5.3	6.7	5.0	6.4	5.3	6.8	5.3	6.8	5.2	6.6	5.1	6.5
WSD9	4.7	3.4	4.7	3.4	4.8	3.4	4.6	3.4	4.5	3.4	4.7	3.4	5.0	3.8
EMSD1	5.0	6.5	5.0	6.5	4.9	6.2	5.1	6.5	5.1	6.5	4.9	6.4	4.9	6.3

Occasionally, the near-surface current speed near the flushing water intake WSD1 can be greater than 0.5 ms^-1 especially during spring tides, such that the effectiveness of the silt screen would be reduced. However, the deployment of silt screen was still recommended at WSD1 since high SS impact occurs due to poor tidal flushing when current speed is low.

Other mitigation measures that should be undertaken during dredging include:

1. maximum dredging rate shall be 4000 m³(in-situ volume) per day per grab dredger and 700 m³in 30 minutes in any given hour (max. 8400 m³/day, based on a 12-hour operation per day) per cutter suction dredger;

2. only two types of dredgers will be allowed for this Project: (a) grab dredger with closed grab, and (b) cutter suction dredger;

3. the allowed maximum number of grab dredgers or cutter suction dredger operating simultaneously within the Project area shall follow the requirement listed in Table 3.5 below;

4. to minimize the potential SS impact from dredging, deployment of silt curtains around the grab dredgers is recommended (please refer to Figure 3.7 attached to the EIA Report for the schematic design);

5. either one cutter suction dredger or one grab dredger shall be working in Zone 2 (including subzones) of the Container Basin (Appendix 3.13 attached to the EIA Report) at any time;

6. CSD is only to be deployed for the removal of harder material during daytime only (07:00 to 19:00) in Zone 2 (including subzones) of the Container Basin (Appendix 3.13 attached to the EIA Report);

7. Project dredging works within Zone 1-6 (including subzones) of the Container Basin (Appendix 3.13 attached to the EIA Report) shall not be carried out at the same time with Terminal Operator’s maintenance dredging activities;

8. if further mitigation measures are required, as demonstrated by the water quality monitoring data under the EM&A programme, then consideration will be given to reducing the dredging rate, or dredging only on the state of the tide which would avoid migration of SS towards the WSD and EMSD intakes;

9. the dredging pump of cutter suction dredger shall be operated during cutting to reduce the sediment loss to water body;

10. no overflow of dredged mud will be allowed. Barges or hopper should not be filled to a level that will cause the overflow of materials or polluted water during loading or transportation;

11. all construction vessels should be sized so that clearance is maintained between vessels and the seabed in all tide conditions, to ensure that undue turbidity is not generated by turbulence from vessel movement or propeller wash;

12. the speed of all construction vessels will be controlled within the works area to prevent propeller wash from stirring up the seabed sediments;

13. all barges / dredgers used should be fitted with tight fitting seals to their bottom openings to prevent leakage of material;

14. construction activities should not cause foam, oil, grease, scum, litter or other objectionable matter to be present on the water within the site or dumping grounds;

15. before commencement of dredging works, the holder of the Environmental Permit should submit detailed proposal of the design and arrangement of the frame type silt curtain to EPD for approval; and;

16. the speed of any construction vessels shall not exceed 10 knots when passing through the Project Site Boundary as shown in Figure 2.1 attached to this Executive Summary.

Table 3.5: Allowed Maximum Number of Grab Dredgers or Cutter Suction Dredger Operating Simultaneously

Locations Scenario	Rambler Channel (A)	Stonecutter Island (B)	Northern Fairway (C)	Western Fairway (D)	Western Fairway (E)
1	One GD		One GD	One GD
2	One GD		One GD		One GD
3			One GD	One GD	One GD
4	One GD	One GD		One GD
5	One GD	One GD	One GD
6	One CSD		One GD		One GD

Treating Hotspot

Sediment from ground investigation S2 location has been identified, through testing sediments and elutriates, to be highly contaminated with ammonia. As such, the impact assessment has identified that it would be prudent to isolate S2 such that the majority (c. 99%) of the navigational (i.e. capital work) dredging can proceed without affecting the overall construction programme. To address the high levels of NH₃-N and hence UIA issue at S2, it is recommended that before dredging works at S2 commences, a field trial or alternative confirmatory method is to be carried out to clearly define the area affected, and thereafter, to propose (through the field trials) an acceptable method or option such as hydraulically closed grab dredgers, specially designed silt curtain, bioremediation or similar methods to work at this area for treating the specific cause of the contamination prior to removal of sediments. The objective of the field trial is to propose the most effective dredging process and rate to control the release of ammoniacal nitrogen and UIA into the water column and achieve compliance at the WSD1 seawater intake (NH3-N) and at the beaches for UIA. Capital dredging works in the vicinity of S2 should not therefore be carried out until the proposed method and rate are confirmed. Having taken note of the other projects in the vicinity, it would be appropriate to time the dredging of S2 to avoid other capital works projects as far as possible and thus the Q3/Q4 of 2013 would currently be favoured.

As discussed in Section 3.7.1.6 of the EIA report, the removal of S2 from the main dredging programme can effectively reduce the predicted level of ammoniacal nitrogen and UIA at seawater intakes and gazetted beaches. This is the first level of mitigation proposed. However, since there is marginal exceedance of WSD guidelines or WQO, a reduction in dredging rate is still recommended as the administrative control strategy to control the release of contaminants into water column. An outline dredging plan is also included in EIA Report, which indicates the dredging sub-zone where S2 is located is to be isolated and with dredging works to be carried out towards the end of the construction programme. The said plan provides a mitigation strategy in which the control of dredging rate is employed as the strategy to control the release of contaminants during dredging.

Operation Phase

Maintenance Dredging

Although SS impacts on the WSRs during the maintenance dredging were expected to be much lesser than the impacts during construction phase, silt screens at the flushing water intakes WSD1 and EMSD1 should be provided. In addition, silt curtain around grab dredgers will be installed during maintenance dredging. Subject to the review of environmental performance of the dredging operations, the deployment of silt curtains may be suspended if supporting evidence is obtained through the operation phase water quality monitoring and audit programme.

Other mitigation measures that should be undertaken during maintenance dredging include:

1. only grab dredger with closed grab will be allowed with a maximum rate of 4000m³/day (in-situ volume);

2. no overflow of dredged material will be allowed. Barges should not be filled to a level that will cause the overflow of materials or polluted water during loading or transportation;

3. all barges used should be fitted with tight fitting seals to their bottom openings to prevent leakage of material;

4. construction activities should not cause foam, oil, grease, scum, litter or other objectionable matter to be present on the water within the site or dumping grounds;

5. in the event that there is an exceedance of SS at the WSD intakes other than WSD1 then further mitigation measures shall be considered including the use of silt curtains or a reduction in the dredging rate; and

6. no maintenance dredging will be carried out concurrently with other maintenance dredging works by container terminal operators.

3.1.4 Environmental Monitoring and Auditing

An environmental monitoring and audit programme including water quality monitoring at specific WSRs e.g. FCZ, seawater intakes, gazetted beaches, coral communities, has been proposed to ensure that all the recommended mitigation measures will be implemented properly.

3.2 Waste

3.2.1 Assessment Scope and Criteria

The waste management implications have been undertaken in accordance with the requirements of the Study Brief and Annexes 7 and 15 of the EIAO-TM. This section identifies the types of wastes arising as a result of the construction and operation of the Project in accordance with the detailed requirements outlined in Condition 3.4.6 of the EIA Study Brief. The major waste will be dredged marine sediment from the Kwai Tsing Container Basin (KTCB) and portions of Western Fairway and Northern Fairway and construction and demolition (C&D) materials resulting from the modification and dismantling works for Kwai Chung and Tsing Yi Submarine Sewage Outfalls.

3.2.2 Impact Assessment

The proposed dredging activities are anticipated to generate a variety of wastes that could be divided into distinct categories based on their composition and ultimate method of disposal. Mitigation measures and good site practices, including waste handling, collection, transportation and disposal are recommended with reference to the applicable waste legislation and guidelines. With the implementation of the recommended mitigation measures, no adverse residual impact is expected to arise during the proposed dredging works.

Major waste generated is dredged marine sediment from the Kwai Tsing Container Basin (KTCB) and portions of Western Fairway and Northern Fairway. 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 dredging area were classified as Category L. The total volume of dredged sediment requiring marine disposal is estimated to be 4,420,384 m³. The volume of dredged sediment suitable for Type 1, Open Sea Disposal (Category L sediment) is estimated to be 1,816,560 m³. The volume of dredged sediment suitable for Type 1, Open Sea Disposal (Dedicated Sites) (Category M_p sediment) is estimated to be 1,102,148 m³. The volume of contaminated sediment requiring Type 2, Confined Marine Disposal (Category M_f and H sediment) was estimated to be 1,501,676 m³

Table 3.6: Summary of Dredging Rate, Manoeuvring of Dredgers and Disposal Routings

Sediment Type	Dredging Rate	Manoeuvring of Dredgers	Proposed Routing for Disposals
Type 1, Open Sea Disposal (Category L sediment)	Up to maximum 12,000 m³ per day	Maximum 3 dredgers will operate at any one time across all works areas per day	South Cheung Chau Open Sea Disposal Area, East Ninepin Open Sea Disposal Area or other designated locations
Type 1, Open Sea Disposal (Dedicated Sites) (Category Mp Sediment)			South of Brothers Confined Marine Disposal Facility Or Cross boundary disposal arrangement (alternative option)
Type 2, Confined Marine Disposal) (Category Mf and Category H Sediment)			South of Brothers Confined Marine Disposal Facilities

^# In accordance with ETWB TC(W) No. 34/2002, sediment with the following category:

L means Category L Material, ≤Lower Chemical Exceedance Level

M_f means Category M Material, >Lower & ≤Upper Chemical Exceedance Level and has failed biological screening test

H means Category H Material, >Upper Chemical Exceedance Level & <10 x Lower Chemical Exceedance Level and biological screening test is not required

H_p means Category H Material, >Upper Chemical Exceedance Level & >10 x Lower Chemical Exceedance Level and has passed biological screening test

H_f means Category H Material, >Upper Chemical Exceedance Level & >10 x Lower Chemical Exceedance Level and has failed biological screening test

* In accordance with ETWB TC(W) No. 34/2002, no biological screening test is required for those Cat H with chemical screening results >Upper Chemical Exceedance Level & <10 x Lower Chemical Exceedance Level. By definition, this material belong to Type 2 Confined Marine Disposal

The sediment would be dredged and transferred to barges for subsequent disposal as allocated by Marine Fill Committee (MFC) depending on the level of contamination. Under the current disposal planning, Category M_p sediment is to be dredged and disposed of at South of Brothers Confined Marine Disposal Facilities or alternatively cross boundary disposal facility. While Category M_f and H sediments will go to the confined marine disposal facilities at South of Brothers Confined Marine Disposal Facility which is the designated disposal site for this Project for accepting this type of dredged material.

For Category L material, which is suitable for open sea disposal in accordance with ETWB TCW no. 34/2002, disposal locations such as South Cheung Chau Open Sea Disposal Area, East Ninepin Open Sea Disposal Area or other designated locations will be allocated by MFC.

It is anticipated maintenance dredging is to be carried out in the operation phase on an irregular basis. Based on the record of Port Works Division, Dredged sediment is expected to be suitable for Type 1, Open Sea Disposal and Type 2 Confined Marine Disposal. The estimated quantity (maximum of 30,000 m³ per annum for this Project, and an estimated total of 225,000m³ for KTCP which includes this Project) is anticipated. Compared to the quantity of sediment generated under the capital dredging works, the associated effect of maintenance dredging in terms of handling and disposal is considered insignificant.

The disposal options as identified in this Project will be subject to confirmation from MFC. The Project will not be carried out before obtaining confirmation from MFC on the disposal option.

The Project also includes the removal of portions of outfall/diffusers of the Kwai Chung and Tsing Yi submarine sewage outfalls above the proposed dredging level, i.e. -17.5mCD. The existing material above the proposed dredging level surrounding the submarine outfall will also be removed. These materials would amount to less than 500 m³. It is anticipated that the rock and rubble generated from the removal of the submarine outfalls will not be dredged during the dredging process and all these material will remain below the sea bed.

Under the Dumping at Sea Ordinance (DASO), a Sediment Quality Report (SQR) is to be prepared for EPD’s approval under DASO before dumping permit is granted. The disposal arrangement as identified for this Project will be subject to procedural agreement from MFC. The Project works will not be carried out before obtaining confirmation from MFC on the disposal option.

3.2.3 Mitigation Measures

Adverse impacts relating to waste management such as odour, noise and wastewater discharge are not expected to arise, provided that good site practices are strictly followed. Recommendations for good site practices during the construction activities include:

1. obtain the profile of different sediment categories and careful planning of sediment removal;

2. strictly follow various mitigation measures for protecting water quality as described in the water quality section of the EIA;

3. nomination of an approved person, such as a site manager, to be responsible for good site practices, arrangements for collection and effective disposal to an appropriate facility, of all wastes generated at the site;

4. training of site personnel in proper waste management and chemical handling procedures;

5. provision of sufficient waste disposal points and regular collection of waste;

6. barges filled with dredged sediment shall be towed away immediately for disposal. In so doing, odour is not anticipated to be an issue to distant sensitive receivers;

7. well planned delivery programme for offsite disposal such that adverse environmental impact from transporting sediment material is not anticipated; and

8. use any well maintained PME on site.

3.2.4 Environmental Monitoring and Auditing

An environmental monitoring and audit programme in terms of regular site audit and checking of various disposal records has been proposed to ensure that all the recommended mitigation measures will be implemented properly.

3.3 Marine Ecology

3.3.1 Scope and Criteria

The potential marine ecological impacts arising from the dredging works have been assessed in accordance with the criteria stipulated in Annexes 8 and 16 of the EIAO-TM and Study Brief. The assessment criterion for protecting the marine ecological sensitive receivers in this Study was based on the fact that a sedimentation rate higher than 0.1 kg m^-2 per day would introduce moderate to severe impact upon corals. While there are no established legislative criteria for water quality for corals, an elevation criterion of SS levels less than 30% of ambient baseline conditions has been adopted as the critical value above which impacts to the habitat may occur. In the fish culture zones, the elevation of SS should be less than 30% of ambient baseline conditions at the fish culture zones based on international marine water quality guidelines for the protection of ecosystems.

The guidelines for protection of marine ecology follow the Water Quality Objectives (WQO) under the Water Pollution Control Ordinance (Cap. 358). The WQO for unionised ammonia (UIA) is 0.021mg/L. In addition to the WQO for unionised ammonia, the recommended maximum concentration to protect 80% marine biota according to the water quality assessment guidelines (WQAG) for ammoniacal nitrogen (NH3-N) within Hong Kong marine waters corrected to pH 8.0 is 1.2mg/L (CityU’s CCPC 2001). This figure should be adjusted for the pH at specific site according to the Consultancy Study on Fisheries and Marine Ecological Criteria for Impact Assessment (City U’s CCPC 2001).

3.3.2 Impact Assessment

The marine ecological resources within or around the dredging area have been studied through literature review and field survey. Marine ecology field surveys for inter-tidal, sub-tidal hard-bottom and soft-bottom benthic habitats were conducted between September 2009 and January 2010. The evaluation of the ecological importance of the marine habitats was conducted through the review of the ecological resources in inter-tidal, sub-tidal hard-bottom and soft-bottom marine benthic communities and the marine mammals in open waters within the four Water Control Zones (WCZs) (Victoria Harbour, Western Buffer, North Western and Southern WCZs). It was found that the ecological resources in Kwai Tsing Container Basin (within the Victoria Harbour WCZ) are relatively low in ecological importance owing to the newly installed artificial habitats colonized by low abundance of pollution tolerant marine organisms. The marine ecological resources at the inter-tidal and sub-tidal hard-bottom habitats at Green Island, Kau Yi Chau, Siu Kau Yi Chau are of moderate-low importance with more natural shorelines and the presence of coral communities. The sub-tidal soft-bottom habitats within the Project area are highly disturbed by marine traffic. Dominant species are polychaetes with indicator species that are tolerant to sediment with low oxygen and high organic content.

Potential impact of loss of soft-bottom seabed habitat due to the dredging works is considered to be minor, owing to the high re-colonizing ability of the marine benthic communities on similar seabed substrates after construction. According to the water quality modelling results, the predicted sediment plume is confined to the dredging area such that the elevation of suspended solid levels around the coral sites is within acceptable levels. Therefore the indirect impacts to off-site habitats induced by the elevation of suspended solid concentration in the water column and the increase in sedimentation rate is expected to be minor. The predicted unionised ammonia (UIA) concentration at all sensitive corals community indicated no exceedance of Water Quality Objective (WQO) will occur during construction phase. Exceedances of WQO for UIA at coastal waters around Rambler Channel are predicted to cause insignificant impact on the dominant marine biota along the modified artificial seawall of low ecological value. The predicted ammoniacal nitrogen concentrations at the coastal waters around Rambler Channel are all within the recommended water quality assessment guideline (i.e. maximum NH₃-N concentration) for the protection of 80% fisheries and marine biota. Thus the potential toxicity effect on marine ecology at coastal waters surrounding the proposed dredging area is anticipated to be of low impact. Anticipated impacts to marine mammals relating to direct collision and indirect disturbance due to dredging activities is negligible as the Project area is outside the distribution range of both the Chinese White Dolphin (Sousa chinensis) and Finless Porpoise (Neophocaena phocaenoides). Besides, anticipated indirect impact to recognized sites of conservation importance namely Cape D’Aguilar Marine Reserve, Sha Chau and Lung Kwu Chau Marine Park, Sham Wan Site of Special Scientific Interest (SSSI) and San Tau Beach SSSI is considered negligible with predicted suspended solid elevation less than 0.1mg/L. Furthermore, in view of minor modification works, low ecological value of the Container Basin and the re-application of rock armour will allow reinstatement of the habitat for the recolonization of inter-tidal and sub-tidal communities, anticipated impact on marine ecology due to the modification of Tsing Yi Submarine Sewage Outfall and demolition of the Kwai Chung Submarine Sewage Outfall is predicted to be insignificant.

During operation phase, direct collision and acoustic disturbance to Chinese White Dolphins and Finless Porpoises due to the incurred marine traffic are considered unlikely and there have been very few sightings of marine mammals recorded in the Project area and its vicinity in the last 10 years. The affected seabed habitat is expected to be recolonized by benthic organisms and no residual impact on marine ecology is predicted. Even though maintenance dredging is to be carried out, it will be of a much smaller scale than capital dredging works. In view of the fact that the Project area is of low ecological value and not the prime habitat for marine mammals, potential impact on marine ecology is considered negligible.

With the use of grab dredgers and by limiting the number of dredgers working simultaneously to three, potential impacts due to SS elevations will be minimised. To further reduce potential impacts, the release of dredged sediment into surrounding waters should be avoided and barges should work as closely as possible to the dredger. Frame type silt curtains will be deployed to reduce the migration of sediment plumes. Other water quality mitigation measures will also help to minimize the impact on marine ecology.

The potential cumulative impact of the increase in suspended solids at marine ecology sensitive receivers including coral communities at Green Island and Kau Yi Chau is considered to be insignificant with the implementation of frame type silt curtain and water quality mitigation measures. The loss of soft-bottom sub-tidal habitat is temporary and benthic fauna will be recolonized after the ceasation of dredging works. Residual impact on marine ecology is considered negligible.

3.3.3 Mitigation Measures

To minimize any potential adverse impacts arising from dredged marine sediment, the release of dredged sediment into surrounding water should be avoided. Barges should work as close as possible to the point of dredging to minimise release of sediment into the receiving waters. Frame type silt curtains will be deployed to reduce the migration of sediment plumes. Additionally, dredged sediment will be transferred to barges for subsequent disposal at the designated disposal site(s) as allocated by MFC.

3.3.4 Environmental Monitoring and Auditing

An environmental monitoring and audit programme has been proposed in term of water quality monitoring at designated locations to monitor the effect of dredging activities to marine ecological environment. The intention of such EM&A programme is to ensure that all recommended mitigation measures will be implemented properly.

3.4 Fisheries

3.4.1 Scope and Criteria

An assessment of the potential impacts of the dredging works on existing fisheries resources, fishing operations and marine culture activities has been undertaken in accordance with the Study Brief and EIAO–TM Annexes 9 and 17, Fisheries Protection Ordinance (Cap 171), Marine Fish Culture Ordinance (Cap 353) and Water Pollution Control Ordinance (Cap 358). Special attention was given to the fishing activities and fishing, spawning and nursery grounds within the Study Area; although it is noted that the dredging area is situated within the Principal Fairways and the Container Basin, which are not regarded as prime fishery operation areas. For the culture fisheries, four Fish Culture Zones namely Ma Wan, Lo Tik Wan, Sok Kwu Wan and Cheung Sha Wan FCZs were identified as the fisheries sensitive receivers.

3.4.2 Impact Assessment

Reviews of existing information[2] on capture and culture fisheries showed that both capture and culture fisheries resources are relatively low and the fisheries activities are infrequent within the area to be dredged.

Impacts to capture fisheries due to temporary loss of fishing ground and short term disruption of fisheries operation are predicted to be minor owing to the low frequency of fishing operation in the proposed dredging area. Indirect water quality impact to the FCZs was assessed with reference to the Water Quality Modelling results, which indicated that the suspended solids (refer to below table), bottom DO and unionised ammonia concentrations are compliant with the Water Quality Objectives as well as the maximum SS criterion of 50 mg/L at FCZs. The non-compliance of depth-averaged DO during wet season and total inorganic nitrogen concentrations is due to the non-compliance of ambient levels as recorded by the routine monitoring of EPD. However the changes in total inorganic nitrogen concentration and DO level during the construction phase in the FCZs are predicted to be insignificant. The potential toxicity effect on capture fisheries operation and fisheries resources due to the potential exceedances of unionised ammonia at coastal waters around Rambler Channel is anticipated to be of low impact, due to the marginal exceedances which are seasonally dependent. The compliance of total ammoniacal nitrogen maximum concentration of 1.2 mg L^-1for protection of 80% of fisheries at coastal waters around the gazetted beaches at Rambler Channel is predicted and the area is not the major capture fisheries operation area as discussed in Chapter 6. This further indicates insignificant impact to fisheries. The potential impact due to the release of contaminants during dredging is considered to be negligible due to the rapid dilution effect and the distance of the FCZs from the nearest dredging boundaries. Therefore the potential impact to the FCZs and fisheries due to the change of water quality in construction phase is predicted to be negligible. Potential impacts on fisheries during the operation phase are negligible as maintenance dredging will only be undertaken on a small scale, compared to capital works dredging which was assessed to be acceptable in terms of water quality, marine ecology and fisheries impact.

Table 3.7: Predicted Suspended Solids Elevations at Fish Culture Zones

Fish Culture Zone	Assessment Point	Dry Season		Wet season
	Assessment Point	Maximum Depth-averaged SS elevation (mgL^-1)	SS Criterion (mgL^-1)	Maximum Depth-averaged SS elevation (mgL^-1)	SS Criterion (mgL^-1)
Ma Wan	F1	2.6 (Scenario 7)	3.2	2.0 (Scenario 7)	2.5
Lo Tik Wan	F2	0.2 (Scenario 3 & 7)	1.8	0.1 (Scenarios 1,2,3, 4, 6,& 7)	1.6
Sok Kwu Wan	F3	<0.1 (all scenarios)	1.8	<0.1 (all scenarios)	1.6
Cheung Sha Wan	F4	<0.1 (all scenarios)	2.6	<0.1 (all scenarios)	4.4

The potential cumulative impact of change in water quality on fisheries due to this Project and concurrent projects were assessed in the Water Quality Impact Assessment. With reference to the water quality modelling results, cumulative impact especially for the elevation of SS levels are predicted to be complying with the relevant criteria for all the FCZs. The implementation of water quality mitigation measures, e.g. installation of frame-type silt curtain for grab dredger will reduce the migration of SS from dredging site to water sensitive receivers including FCZs.

As the future maintenance dredging will be of a much smaller scale than capital dredging works, and in view of the Project area is not the prime fishery operation area, the potential impacts on fisheries resources and fishing operations are considered to be negligible during periods of maintenance dredging.

3.4.3 Mitigation Measures

General good site practices and mitigation measures recommended for controlling water quality to acceptable levels are also expected to be effective in minimizing the impact to capture and culture fisheries during the construction phase. Measure include: control of the speed of all construction vessels within the works area to prevent propeller wash from stirring up the seabed sediments; barges / dredgers to be fitted with tight fitting seals to their bottom openings to prevent leakage of material; and barges or hopper not to be filled to a level that will cause the overflow of materials or polluted water during loading or transportation and the use of a frame type silt curtain.

3.4.4 Environmental Monitoring and Auditing

An environmental monitoring and audit programme has been proposed in term of water quality monitoring at the four fish culture zones (Ma Wan, Lo Tik Wan, Sok Kwu Wan and Cheung Sha Wan FCZs) during the course of the marine construction works. 24 hours water quality monitoring is also suggested at the four FCZs for continuous measurements of DO, temperature and turbidity to supplement the routine monitoring activities. Similarly, the intention of such EM&A programme is to ensure that all recommended mitigation measures will be implemented properly.

3.5 Hazard to Life

3.5.1 Assessment Scope and Criteria

The hazard to life assessment has been undertaken in accordance with the requirements of the Study Brief and Annexes 4 of the EIAO-TM. Currently, there are 3 nos. of LPG/oil depots located in the vicinity of the proposed dredging area, located at the southern part of Tsing Yi, include:

N6: Exxon Mobil Tsing Yi East Terminal for LPG and oil at TYTL 46RP;

N8: Exxon Mobil Tsing Yi West Terminal for LPG and oil at TYTL 115; and

N11: China Resources Petrochemicals Co. Ltd (now SINOPEC) LPG and oil depot at TYTL 127

The Hazard to Life assessment has been undertaken to assess the potential risk to construction workers and users during the construction stage of the Project due to their presence within the consultation zones of the mentioned Potentially Hazardous Installations (PHIs). The potential adverse impacts to construction workers and personnel onboard dredgers, barges and other supporting craft will be evaluated by considering the total capacity of N6 and N11, of which the 1 km consultation zone for the depots overlaps with part of the proposed dredging area.

3.5.2 Impact Assessment

The hazard assessment consists of the following steps: Information Collection; Hazard Identification; Frequency Assessment; Consequence Assessment; Risk Summation and Assessment; and Risk Mitigation and Recommendations.

Hazard scenarios from the SINOPEC and ExxonMobil LPG/ oil depots are then identified for the study. Population data, including land, marine, road and dredging workers, as well as meteorological data, are obtained from relevant sources. Consequence distances and occurring frequencies are then evaluated for risk summation in the SAFETI modelling software.The results of assessment are then compared with the Hong Kong Government Risk Guidelines (HKRG) stipulated in Annex 4 of the Technical Memorandum for Environmental Impact Assessment Ordinance (EIAO-TM) to determine the acceptability, which included the criteria for Individual Risk Guideline and Societal Risk Guideline.

Individual Risk: The 1×10^-5 per year risk contours extend slightly outside the PHI boundaries, but are mostly close to the site boundary and does not go into the proposed dredging works area. Further away from the depot and jetty, the risk gradually diminishes to lower risk levels. The individual risk levels of the two PHIs therefore marginally satisfy the Hong Kong Government Risk Guidelines for individual risk. It should also be noted that individual risk is solely determined by the LPG/ oil depots (N6, N11) and is not related to the actual population. Therefore, individual risk is not affected by the presence of the dredging workers of the Project.

Societal Risk: The Frequency-fatality (FN) curves for the SINOPEC and ExxonMobil Depots before, during and after the dredging works project indicated that the societal risk levels for “all neighbouring population” (including dredging workers) for both depots have only insignificant changes from Year 2009 to 2012 and then to 2014. The reason for the change is due to changes in land, road and marine population nearby the PHIs. The F-N curves of the two PHIs all lie in the ALARP region. It should be noted that the proposed dredging project does not cause the societal risk levels of the two PHIs to go into the ALARP region. As compared to the overall societal risk from the two depots, the presence of dredging workers of the proposed project is marginal. Therefore it can be concluded that with the dredging works project taking place, the societal risk levels of the LPG/ oil depots still satisfy the Hong Kong Government Risk Guidelines for societal risk.

In summary, the overall risk levels show that the two depots meet the Hong Kong Government Risk Guidelines, which is consistent with previous studies. The increase in societal risk caused by the presence of the dredging workers is minimal comparing to the overall risk level, and is not permanent. It is therefore concluded that the risks posed by two PHIs on the neighbouring population and the dredging workers satisfy the Hong Kong Government Risk Guidelines.

3.5.3 Mitigation Measures

In spite of the negligible additional risk, mitigation measures are recommended to further reduce the risks as low as reasonably practicable. Sound communication channels shall be established with the oil companies, Marine Department, and Fire Services Department for effective notification and emergency evacuation in case of accidents. In addition, proper safety and emergency training should be given to the relevant operation staff at the dredging site. Emergency plans and procedures should be prepared and drills should be performed periodically.

3.5.4 Environmental Monitoring and Auditing

In view of the above assessment, no requirement for environmental monitoring and auditing is envisaged.

3.6 Landscape, Visual and Glare

3.6.1 Assessment Scope and Criteria

Landscape, Visual and Glare Impact Assessment was conducted for the Project. The proposed Project is situated in the Rambler Channel, Northern Fairway and Western Fairway. No land works are proposed within any landscape related zonings. Therefore the Project will not have any conflict with the landscape setting of the area.

The assessment of landscape impacts involved the following procedures: identification of baseline landscape resources and landscape character areas; assessment of degree of sensitivity to change of the landscape resources and character areas; identification of potential sources of landscape impacts; identification of the magnitude of landscape impacts; identification of potential landscape mitigation measure; and predicted significance of landscape impacts before and after the implementation of the mitigation measures. The landscape impacts is to be assessed in accordance to Annex 10 and 18 of the EIAO-TM and Study Brief to determine if the impacts are beneficial, acceptable, acceptable with mitigation measures, unacceptable or undetermined.

Assessment of the potential magnitude of visual and glare impacts will consider such factors including: compatibility with the surrounding landscape; duration of the impact, reversibility of the impact; scale of the impact and distance of the source of impact from the viewer, and blockage of view. The magnitude of visual and glare impact is classified as: Large; Intermediate; Small; or Negligible. The visual impact assessment covered the areas of Ma Wan, Tsing Yi, Kwai Chung, Tsuen Wan, Northeast Lantau and Northwestern part of Hong Kong Island. All the key visually sensitive receivers (VSRs) within the zone of visual influence were identified (Figure 3.2).

Potential glare impacts assessment during construction covered all the nearby sensitive receivers in Tsing Yi, Kwai Chung, Tsuen Wan, Lamma Island, Western and Southern Districts and uses of Route 8. According to the EIAO-TM, glare is included as one of the potential visual impact source which would cause uncomfortable eye feeling by direct or indirect light source. Potential glare sources include the night lighting associated with the dredgers. As glare impact or uncomfortable eye feelings are subjective, some typical light levels are presented below to give a point of reference.

Major Sports Stadium: 1000 to 2000 lux

e.g. Hong Kong Stadium – 1400 lux, 2008 Beijing Olympics Equestrian Venue, Shatin – 1400 lux

Sunny Day: 30,000 to 50,000 lux

(Lux is a unit used to define illustration. 1 lux is equal to 1 lumen falling on an area of 1 square metre)

3.6.2 Impact Assessment

The baseline study identified 14 landscape resources and 5 landscape character areas (LCA) within the assessment area. As the Project will not involve any land works, no conflicts with any identified landscape resources and landscape character areas were anticipated during the construction and operational phases. The impact level on existing landscape is therefore acceptable.

The proposed works only involve seabed dredging and a small number of dredgers to be used compared with the busy maritime traffic traversing the exiting fairways, and thus the level of visual impact is anticipated to be acceptable. There will be no significant visual effects caused by the implementation of the Project on identified VSRs during the construction or operational phases.

Lighting for the 24-hour dredging operation is the only man-made light source generated by the proposed Project. The proposed lighting for dredging activities of the Project will be about 250 lux, which is applicable to both day-time and night-time dredging for 24-hour operation. However, the proposed dredging works will not cause any adverse glare nuisance, as these man-made light sources will not be directly pointing to any VSRs and potential spill light will be avoided by the provided visa shields to the lights of dredgers. There will also be no facilities or equipments installed with mirrors or any other polished materials on the dredgers. The slight increase of about 5-20 lux experienced by the VSRs due to the Project will be insubstantial as this low level of lighting intensity basically is not noticeable to the VSRs. Therefore the glare impact level is considered to be acceptable.

3.6.3 Mitigation Measures

Landscape: The proposed Project involves no land works and therefore no conflicts with all existing landscape resources and landscape character areas were anticipated. No specific mitigation measure is required.

Visual and Glare: Although no adverse visual and glare effects were identified, some precautionary measures are recommended to ensure the environmental performance in terms of visual and glare nuisance at VM1 (ID no. of visual mitigation measure). Proper site practice for works lighting shall carefully consider the following: to avoid light pollution and glare to the surroundings; visa shields to the lights of dredgers shall be provided; the light source shall not point directly to any VSRs; and lights shall be switched off if they are not in use.

3.6.4 Environmental Monitoring and Auditing

In view of the above assessment, no requirement for environmental monitoring is envisaged.

3.7 Cultural Heritage

3.7.1 Assessment Scope and Criteria

The cultural heritage impact has been undertaken in accordance with the requirements of Annexes 10 and 19 of the EIAO-TM and Study Brief. A Marine Archaeological Investigation (MAI) was completed to locate and assess the significance of any underwater cultural heritage which may be present on the seabed in the areas that will be impacted by the dredging works. In accordance with Antiquities and Monuments Office (AMO) Guidelines, the MAI comprised: Marine Archaeological Review, Baseline Review, Geophysical Survey, Assessment of Archaeological Potential and Impact Assessment.

3.7.2 Impact Assessment

There have been no previous MAI Studies in the vicinity of the current study. The two previous EIA studies in the vicinity, namely for the South-East Tsing Yi Port Development and for dredging of the Anchorage Area for Stonecutters Island Naval Base, did not contain any information relevant to the current investigation.

The Baseline Review revealed historical evidence indicating that the waters within the Study Area have been the focus of intense maritime activity. The main shipping route to Guangzhou passes though this area, although the Kap Shui Mun passage would be used in preference to the Rambler Channel. The prevalence of piracy throughout the Hong Kong region gives an increased likelihood of shipwreck occurrence. However, the land and islands adjacent to the Study Area have been the focus of some of the most intensive development in Hong Kong. Most of the original coastline is now buried beneath extensive reclamation. Archive research did not locate any records showing shipwrecks within the Study Area except the QE1 (Figure 3.4), which has been salvaged. The current dredging will not impact the location of the QE1.

In November 2009 a geophysical survey was completed to cover 100% of the Study Area. It revealed that the seabed within the Study Area is extensively disturbed with clear evidence for previous dredging, dumping and modern debris. This is particularly intense in the vicinity of the existing utilities: two submarine outfalls, one pipeline and two submarine cables.

The side scan sonar data indicated the presence of 74 sonar contacts for unidentified objects. 54 of these have been disregarded as having archaeological potential. The remaining 20 are all situated in areas where there has been extensive previous dredging. The seismic profiler data showed 36 seismic contacts for buried objects. However, most of these contacts are associated with the modern utilities. There were some sections of the Study Area for which there was no data due to gas masking.

The geophysical survey confirmed that the seabed within the Study Area has been previously disturbed. The most significant impact on the seabed across the Study Area is the extent of previous dredging. This started in 1990 with maintenance dredging and subsequently construction of the Container Terminal 9 in 1998. Regular maintenance dredging is carried out. The full MAI sets out the details of the dredging and it can be clearly seen that the entire seabed has been dredged at each of the 20 unidentified sonar contacts. Dredging would have had a negative impact on the seabed and would have served to destroy or redistribute archaeological remains, if present. It is therefore not possible that an intact archaeological site is present on the seabed within the Study Area. The 20 unidentified objects could represent isolated objects that have been exposed and moved by the dredging but it is more likely they are modern dumped materials. The objects have low archaeological potential.

3.7.3 Mitigation Measures

As the seismic profiler data was not able to provide 100% coverage due to the gas masking, it is recommended that a monitoring brief is conducted. The 20 sonar contacts have low archaeological potential and it is recommended that a monitoring brief should be conducted during the dredging. When dredging occurs in the vicinity of the sonar contacts and the masked areas, a marine archaeologist should be present to monitor the dredged spoil and provide advice. If material indicative of archaeological remains is retrieved, the AMO should be contacted as soon as possible.

3.7.4 Environmental Monitoring and Auditing

In view of the above assessment, no particular requirement for environmental monitoring and auditing is envisaged, except that a monitoring brief shall be conducted for the 20 sonar contacts and masked areas during the dredging.

3.8 Noise

3.8.1 Assessment Scope and Criteria

Potential noise impact arising from the construction of the Project has been evaluated, based on the criteria and guidelines for evaluation and assessing noise impact as stated in Annexes 5 and 13 of the EIAO-TM , Study Brief and Noise Control Ordinance (NCO), with the key criteria illustrated below.

Table 3.8: Noise Standards for Daytime Construction Activities

Noise Sensitive Uses	0700 to 1900 hours on any day not being a Sunday or general holiday, Leq (30 min), dB(A)
All domestic premises including temporary housing accommodation	75
Hotels and hostel	75
Educational institutions including kindergarten, nurseries and all others where unaided voice communication is required	70 65 during examination

Table 3.9: Area Sensitivity Rating

Type of Area Containing NSR	Degree to which NSR is affected by Influencing Factors (IF)
Type of Area Containing NSR	Not Affected	Indirectly Affected	Directly Affected
(i) Rural area, including country parks or village type developments	A	B	B
(ii) Low density residential area consisting of low-rise or isolated high-rise developments	A	B	C
(iii) Urban area	B	C	C
(iv) Area other than those above	B	B	C

Table 3.10: Acceptable Noise Level for Construction Noise

Time Period	ANL, Leq (30 min), dB(A)
Time Period	ASR A	ASR B	ASR C
All days during the evening (1900 to 2300 hours), and general holidays including Sundays during the daytime and evening (0700 to 2300 hours)	60	65	70
All days during the night-time (2300 to 0700 hours)	45	50	55

3.8.2 Impact Assessment

Noise Sensitive Receivers (NSRs) located closest to the Project site boundary are selected for the assessment. They are Ching Tao House (CTH) of Cheung Ching Estate in Tsing Yi, which is located more than 310m from the site boundary and Cheung Ching Estate which are within 500m from the site boundaries (Figure 3.3).

The construction noise impact assessment has been based on different work schedule scenarios. The construction noise level at the representative noise sensitive receiver (NSR) is predicted to be 43 to 54 dB(A) which complies with the construction noise standard during daytime working hours i.e. 75 dB(A). No adverse noise impact is anticipated. During periods of maintenance dredging in the operational phase, it is anticipated that a reduced plant inventory will be used on the basis of the significantly reduced dredging volumes anticipated for maintenance dredging compared to capital works dredging. Given that the use of three dredgers was acceptable for the construction phase, then it may be surmised that maintenance dredging will also be able to comply with the relevant noise criteria.

Based on the assessment, the construction noise levels predicted at the representative NSR will also comply with the noise standards during restricted hours. It is therefore considered feasible to undertake dredging works over a 24 hour period, subject to obtaining a Construction Noise Permit for works being carrying out in restricted hours.

3.8.3 Mitigation Measures

No mitigation measures are required during the daytime construction, as no exceedance of the daytime noise criteria is anticipated. The construction noise level at the representative NSR is predicted to comply with the noise standards stipulated in the GW-TM. No residual impact is anticipated,

In order to further ameliorate the construction noise impacts, good site practices listed below should be adopted by all the Contractors as far as practicable. Although the noise mitigating effects are not easily quantifiable and the benefits may vary with the site conditions and operating conditions, good site practices are easy to implement and do not impact upon the works schedule.

1. Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction programme;

2. Machines and plant that may be in intermittent use should be shut down between works periods or should be throttled down to a minimum;

3. Plant known to emit noise strongly in one direction should, wherever possible, be orientated so that the noise is directed away from nearby NSRs; and

4. Should dredging be carried out during restricted hours, work locations close to NSRs shall be avoided.

3.8.4 Environmental Monitoring and Auditing

As no existing or planned NSR have been identified within 300 m from the works areas and the predicted construction noise level at the NSR located nearest to the works areas is far below the daytime noise criteria, construction noise monitoring is not required. If there are any planned noise sensitive uses within 300m from the works area occupied during the dredging period, noise monitoring programme should then be implemented during the period(s) with predicted occurrence of noisy activities.

Notwithstanding the above, auditing of the site works to ensure proper implementation of the required mitigation measures is recommended.

3.9 Air

3.9.1 Assessment Scope and Criteria

The air quality impact has been undertaken in accordance with the requirements of Section 1 of Annexes 4 and 12 of the EIAO-TM and Study Brief. Potential air quality impact arising from the construction of the Project has been evaluated. Assessment Criteria for aerial emission is based on the Hong Kong Air Quality Objectives (“AQO”) for air pollutants given in Chapter 9, "Environment", of the Hong Kong Planning Standards and Guidelines (HKPSG) for air pollution control and are listed below.

Table 3.11: Hong Kong Air Quality Objectives

Pollutant	Concentration in micrograms per cubic metre
	Average Time
	1 hour	8 hours	24 hours	3 months	1 year
Sulphur Dioxide	800	N.A.	350	N.A.	80
Total Suspended Particulates	500*	N.A.	260	N.A.	80
Respirable Suspended Particulates	N.A.	N.A.	180	N.A.	55
Nitrogen Dioxide	300	N.A.	150	N.A.	80
Carbon Dioxide	30,000	10,000	N.A.	N.A.	N.A.
Photochemical Oxidants (as Ozone)	240	N.A.	N.A.	N.A.	N.A.
Lead	N.A.	N.A.	N.A.	1.5	N.A.

3.9.2 Impact Assessment

Within the 500m assessment area, 24 existing air sensitive receivers (ASRs) were identified in accordance with Annex 12 of the EIAO-TM which the main ones including Hutchison Logistics Centre, Asia Terminal Limited Logistics Centre, Mariners’ Club, Modern Terminal Limited Building, Tsing Yi Industrial Centre, Cheung Ching Estate, Hong Kong International Terminal, Rambler Oasis Hotel and Rambler Crest (Figure 3.3).

The construction activities involved in the Project are mostly marine based and without dusty activities. The dredged materials are of very high moisture content and dust emissions are not expected during the construction period.

According to the marine site investigation results, the acid volatile sulphide (AVS) levels are of similar magnitude than those of the odour remediated sediments collected from Shing Mun River and Sam Ka Tsuen Typhoon Shelter. It is anticipated that the potential odour emissions from the dredged sediments from this Project will be minimal given the magnitude of AVS tested and sensitive receivers are far away and adverse odour impact is therefore not anticipated.

3.9.3 Mitigation Measures

Negligible dust impact is expected from the proposed dredging activities. To further ensure the minimization of potential air quality impact at the ASRs, requirements of the Air Pollution Control (Construction Dust) Regulation, where relevant, shall be adhered to during the construction and any maintenance dredging activities.

Adverse odour impact during dredging is not anticipated. However, in recognition of good site practice and in order to minimize any potential odour emissions, the dredged sediment placed on barge for more than one day shall be properly covered as far as practicable to minimise the exposed area and hence the potential odour emissions during the transportation of the dredged sediment. If dredged sediment is found to be malodorous it shall be removed from site as soon as possible.

3.9.4 Environmental Monitoring and Auditing

In view of the above assessment, no requirement for environmental monitoring is required; however, auditing of the site works to ensure proper implementation of the required mitigation measures is recommended.

4. Environmental Monitoring and Audit

An environmental monitoring and audit programme (EM&A programme) has been recommended for implementation during construction of the Project to ensure compliance with environmental legislation and standards during Project implementation.

On the basis of the assessments carried out for this EIA, monitoring of water quality is recommended during construction and periods of maintenance dredging for this Project. The monitoring programme has been designed to confirm the effectiveness of the mitigation measures proposed and the acceptability of the impacts associated with the Project. It has also been developed to obtain a robust, defensible database of baseline information for water quality before construction, and thereafter, to monitor any variation of water quality from the baseline conditions and exceedances of relevant water quality objectives (WQOs) at the sensitive receivers during construction of the Project. It should also be noted that the monitoring of water quality also provides details on the acceptability of the works on the marine ecology and fisheries resources as described in the EIA.

While none of the other aspects considered under this EIA require formal monitoring under the Environmental Monitoring and Audit programme for the works, it is recommended that auditing of these aspects is undertaken and this has formed the basis of the holistic EM&A programme.

In addition to dredging, in order to ensure that the hydraulic performance of the Tsing Yi Submarine Sewage Outfall will not be adversely affected due to the proposed dredging and outfall modification works, hydraulic performance monitoring is proposed to be conducted before, during and after the proposed modification works. A summary of the proposed monitoring and auditing requirements is given in Table 4.1 for the construction phase.

Table 4.1: Environmental Monitoring and Audit Requirements during Construction Phase

Environmental Aspects	Environmental Monitoring	Site Audit
Water	√	√
Waste	X	√
Marine Ecology	X	√
Fisheries	X	√
Hazard to Life	X	√
Landscape, Visual and Glare	X	√
Cultural Heritage	√	√
Noise	X	√
Air Quality	X	√

Although the volume of dredging required for maintenance dredging is less than for the capital works dredging, the monitoring of water quality and auditing of waste handling and disposal arrangements is recommended, as part of the maintenance dredging programme.

5. Conclusions

This EIA has provided an assessment of potential environmental impacts associated with the dredging works in Kwai Tsing Container Basin and its Approach Channel, based on the information available at this stage. In selecting the preferred option to accomplish the required dredging operation within the anticipated time frame, consideration has been given to technical feasibility, environmental acceptability and public reactions. Moreover, a number of mitigation measures have been identified to minimise the potential for adverse environmental impacts to occur. The mitigation measures are detailed in full in the Environmental Mitigation Implementation Schedule in Chapter 13 of the EIA Report. These measures will be implemented by the Project Proponent and, if appropriate, enforced by EPD by means of the EIAO.

One of the key environmental outcomes has been the ability to plan, design and ultimately construct the Project so that direct impacts to sensitive receivers are avoided, as far as practically possible. Considerations of different dredging options with regard to engineering feasibility and environmental effects have been undertaken. Combinations of dredging scenarios and the associated effects were studied. Preferred options were proposed to minimise the impacts on water quality and avoid direct impacts to water quality, ecologically sensitive habitats and Fish Culture Zones (FCZ).

The equipment that can be deployed for this project is constrained by a number of factors including; the layout and seabed composition of the KTCB; the need to maintain undisrupted operation of the KTCP during the dredging works; the programme; and the need to avoid adverse environmental impacts.

Given the findings from marine traffic impact and environmental effects, the use of grab dredgers was identified as the preferred dredging method, as the grab dredger is able to meet the technical requirements while limiting environmental impacts. However, the grab dredger may not able to remove harder materials which have been identified in the NE of the KTCB. Alternative equipment such as CSD was suggested. Since this harder material only amounts to approximately 2% of the overall dredged material the use of CSD will not materially affect the assessment of the impacts associated with this Project. This has been confirmed in the assessments undertaken.

It was also seen that within the Project area, a hot spot was found at location near Container Terminal no. 1 and 5 (S2), where its ammoniacal nitrogen value in elutriate was recorded at more than 20 mg L^-1. Upon examination it was surmised that the high reading could be due to historically deposited contaminants from activities in the immediate area. As such, it would prudent to isolate S2 such that the majority (c. 99%) of the navigational (i.e. capital work) dredging can proceed without affecting the overall construction programme. To address the high levels of NH₃-N and hence UIA issue at S2, it is recommended that before dredging works at S2 commences, a field trial or alternative confirmatory method is to be carried out to clearly define the area affected, and thereafter, to propose (through the field trials) the most effective dredging process and rate to control the release of ammoniacal nitrogen and UIA into the water column.

Detailed impact assessments have been conducted for both construction and operational phases of the Project, and have concluded acceptable impacts for all aspects considered. With the assistance of water quality modelling, water quality impacts have been demonstrated as being acceptable, albeit with the adoption of mitigation measures for the protection of water quality at the WSD seawater intakes.

A programme of Environmental Monitoring and Audit has been developed to confirm the effectiveness of the mitigation measures associated with the Project.

[1] The prohibition of overflowing from TSHDs reduces their efficiency and effectively nullifies any dredging rate advantage over grab dredging; this effect is exacerbated with increasing separation between dredging site and disposal facility.

[2] Please refer to Section 6.12 of the EIA report for the complete list of references.