6                                       Ecology

6.1                                 Introduction

6.1.1.1                     The EIA Report identified the construction of the proposed Sludge Treatment Facilities (STF) would have minor impact on the potential breeding ground of Little Grebe in the Assessment Area.  Potential indirect construction and operation impacts to the habitats and associated wildlife adjacent to the proposed STF would be resulted from increased human disturbance/activities and noise due to vehicles entering and exiting the site.  Mitigation measures have been recommended to minimize potential indirect impacts to wildlife.

6.1.1.2                     With the implementation of the recommended mitigation measures, it is anticipated that the construction and operation for the proposed works would not result in unacceptable impacts on ecological resources.  This section describes the requirements for the monitoring and audit of ecological impacts from the Project.

6.1.1.3                     The ecological monitoring and audit should be conducted by experienced ecologist(s) with over seven year experience in relevant field. 

6.2                                 Pre-construction Phase Monitoring

6.2.1.1                     Pre-construction ecological monitoring should be conducted prior to the commencement of any site activities to investigate the current habitat condition of the Middle Lagoon and report changes, if any, by providing an updated habitat map of the area.  The monitoring area should include the whole Middle Lagoon and area extended 20 m from the boundary of the Lagoon.  A walk through survey should be conducted within the monitoring area to identify any changes which have taken place since the EIA study which might have impact on the vegetation, habitats and associated fauna.

6.3                                 Construction Phase Monitoring

6.3.1                           Introduction

6.3.1.1                     Ecological monitoring is recommended during construction phase of the Project.  The implementation of the mitigation measures proposed under the EIA Report should be audited as part of the EM&A procedures during the construction period.  Details of the recommended mitigation measures are listed below.

6.3.2                           Measures to Avoid Mortality of Little Grebe

6.3.2.1                     Breeding activities of Little Grebe were observed within the East Lagoon.  If unmitigated, juvenile and chicks of Little Grebe with lower mobility could be killed due to construction activities.  As a precautionary measure, the whole Project Area would be thoroughly inspected twice at the earliest two weeks before the proposed start date of construction activities to confirm no breeding activities of Little Grebe (including their eggs, chicks and juveniles) would be affected by the construction activities.  The inspection should be carried out by experienced ecologist(s) with over seven year experience in the relevant field.  Agriculture, Fisheries and Conservation Department (AFCD) should be informed in writing about the suitability of conducting construction work in the Project Area before the commencement of any site activities.

6.3.2.2                     In case breeding activities (e.g. nests, chicks or juveniles) of Little Grebe are found during site inspection, the programme and method of construction would be carefully reviewed to investigate the practicable measures to minimise impact to the breeding birds through:-

l            careful phasing of construction works, reschedule to commence the works in the breeding area in a later stage;

l            minimisation of disturbance impact to the breeding birds due to construction activities.  As Little Grebe is very sensitive to human movement, it is important to screen off construction works and human activities by erection of hoarding around the breeding ground.  Sufficient buffer area should be provided between the breeding bird and hoarding to allow for their feeding, foraging and roosting activities.  The fenced-off area would be inspected weekly to confirm the effectiveness of the mitigation measure and allow adaptive measures to be made promptly; and

l            restriction of access to the breeding site.  No personnel should encroach the breeding area without the written permission from the Resident Engineer. 

6.3.2.3                     The above mentioned mitigation measures should be stipulated in contract documents to ensure the Contractors are well aware of the requirement.  

6.3.3                           Measures to Minimize Disturbance Impact to Wildlife

6.3.3.1                     To minimize the disturbance to wildlife due to human activities, where practicable, hoarding of 3 m high should be set up along the boundary of the works areas and associated site access to shield the fauna in the Middle Lagoon and other natural habitats from the disturbance impact of human activities.  Fencing with climbers or plantation would be provided, where appropriate, along the STF site boundary and the two sides of access road to screen the surrounding habitats from the STF operation.

6.3.3.2                     The works boundaries should not go beyond the proposed Project Area as shown in Figure 1.2.  All work crews, equipment and human activities should be confined within the designated works area only.  No personnel should encroach or wilfully disturb any wild animals and their habitats.  Traffic and human access from the western side of the Project Area should be avoided.

6.3.3.3                     To reduce noise disturbance to habitats and wildlife adjacent to the works area, noise mitigation measures including the use of quieter piling machinery and construction plants should be implemented to lower the noise level due to construction works.

6.3.3.4                     The above measures should be monitored at least twice per month during the construction phase.  Additional weekly audit should be conducted during the period of piling. In case of non compliance, the Contractor would be informed to implement the proposed measures properly.

6.3.3.5                     To evaluate the effectiveness of the above measures, monthly monitoring of avifauna and their notable behaviour, such as breeding activities, in the Middle Lagoon would be carried out during construction phase. The monitoring area should include the whole Middle Lagoon and area extended 20 m from the boundary of the Middle Lagoon.  All birds seen and heard in the Middle Lagoon would be identified and counted. Signs of breeding (e.g. nests, recently fledged juveniles) of birds (e.g. Little Grebe) would also be recorded.  The coverage of water and PFA filling activities in the Middle Lagoon as well as construction activities in project site would be recorded as reference information.  Subject to the findings of avifauna record and habitat condition of Middle Lagoon, the effectiveness of the proposed mitigation measure would be reviewed as necessary.

6.3.4                           Measures to Minimize Impact to Habitats

6.3.4.1                     Where practicable, all proposed works should be conducted in existing built up area to minimize impact to natural habitats.  All temporarily affected natural habitats, including streambed, should be reinstated after the completion of works. 

6.3.4.2                     To minimize loss to aquatic environment, the abutment (permanent structure) for the vehicular bridge should not be constructed at streambed.  The number and size of the temporary supporting structures to be installed during construction should be minimized as far as practicable.  For natural stream, placement of substrates of similar size and composition to those of original streambed should be considered to encourage colonization.  Measures to control potential water quality impacts to the nearby watercourse and marine environment during construction phase would be implemented and audited as mentioned in Section 5 of this EM&A Manual. 

6.3.4.3                     To minimize the potential water quality impacts from the construction works located at any river channels, natural streams or seafront, the practices outlined in ETWB TC (Works) No. 5/2005 “Protection of natural streams/rivers from adverse impacts arising from construction works” should be adopted where applicable.  Relevant mitigation measures are listed below:-

·        The proposed works should preferably be carried out within the dry season where the flow in the storm culvert/river channel/stream is low;

·        The use of less or smaller construction plants may be specified to reduce the disturbance to the riverbed;

·        Any works site inside the storm water courses should be temporarily isolated, such as by placing of sandbags or silt curtains with lead edge at bottom and properly supported props to prevent adverse impact on the water quality;

·        Temporary sewerage system should be designed to prevent wastewater from entering the river, streams and sea;

·        Temporary storage of materials (e.g. equipment, filling materials, chemicals and fuel) and temporary stockpile of construction materials should be located well away from any water courses during carrying out of the construction works;

·        Stockpiling of construction materials and dusty materials should be covered and located away from any water courses;

·        Construction debris and spoil should be covered up and/or disposed of as soon as possible to avoid being washed into the nearby water receivers;

·        Construction activities, which generate large amount of wastewater, should be carried out in a distance away from the waterfront, where practicable;

·        Mitigation measures to control site runoff from entering the nearby water environment should be implemented to minimize water quality impacts.  Surface channels should be provided along the edge of the waterfront within the work sites to intercept the runoff;

·        Construction effluent, site run-off and sewage should be properly collected and/or treated;

·        Proper shoring may need to be erected in order to prevent soil/mud from slipping into the storm culvert/river/stream/sea; and

·        Supervisory staff should be assigned to station on site to closely supervise and monitor the works.

6.3.4.4                     Standard good site practices should be implemented during the construction phase include the followings:-

·        Placement of equipment or stockpile in designated works areas and access routes selected on existing disturbed land to minimize disturbance to natural or moderate ecological valued habitat;

·        Construction activities should be restricted to works areas that would be clearly demarcated;

·        The works areas should be reinstated immediately after completion of the works;

·        Waste skips should be provided to collect general refuse and construction wastes. The wastes should be disposed of timely and properly off-site;

·        Drainage arrangements should include sediment traps to collect and control construction run-off;

·        Open burning on works sites is illegal, and should be strictly prohibited;

·        Temporary fire fighting equipment in the works areas should be provided to prevent any open fire;

·        Erect fences along the boundary of the works areas before the commencement of works to prevent tipping, vehicle movements and encroachment of personnel into adjacent areas;

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

·        Machines and plant which may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;

·        Plant known to emit noise strongly in one direction, should, where possible, be orientated so that the noise is directed away from the Middle Lagoon;

·        Silencers or mufflers on construction equipment should be utilized and should be properly maintained during the construction period;

·        Mobile plant (such as generator) should be sited as far away from the Middle Lagoon as possible; and

·        Material stockpiles and other structures should be effectively utilized, where practicable, to screen noise from on-site construction activities.

6.3.4.5                     The above measures should be monitored at least twice per month during the construction phase.  In case of non compliance, the Contractor would be informed to implement the proposed measures properly.

6.3.5                           Measures to Mitigate and Compensate for the Loss of Vegetation

6.3.5.1                     All vegetation located within the works area should be preserved as far as practicable.  To compensate for the loss of the vegetation and habitats, tree planting should be provided in the site area at where possible.  Species chosen for planting would be similar to the species identified in the survey and be native to Hong Kong or the Southern China.  The condition of the retained vegetation on site should be monitored once a month throughout the construction phase. 

6.3.6                           Measures to Create Additional Habitat for Little Grebe

6.3.6.1                     An additional pond habitat for Little Grebe would be created in a less disturbed area located at the northeastern part of the proposed STF.  The created habitat would be provided in the form of shallow pond(s) incorporating suitable habitat characteristics for Little Grebe.  The water level of the created pond would be kept between 1.5 m to 2 m.  Emergent vegetation would be planted and fish population would be controlled to allow development of aquatic invertebrate populations as prey of Little Grebe.  To screen the created habitat from disturbance due to nearby landfill traffic, planting of native vegetation would be provided on the boundary of the pond(s) as appropriate.  Prior to construction of the pond(s), the detailed Habitat Creation and Management Plan (HCMP) of the created habitat prepared by experienced ecologist(s) with over seven year experience in relevant field should be circulated to relevant departments including AFCD for comment.

6.4                                 Post-construction Phase Monitoring

6.4.1                           Introduction

6.4.1.1                     Post-construction phase ecological monitoring should be conducted within the monitoring areas for a period of one year upon completion of construction.

6.4.2                           Site Condition and Bird Monitoring

6.4.2.1                     Bi-monthly monitoring of avifauna and their notable behaviour, such as breeding activities would be carried out during post-construction phase.  The monitoring area should include the whole Middle Lagoon and area extended 20 m from the boundary of the Lagoon.  All birds seen and heard would be identified and counted.  Signs of breeding (e.g. nests, recently fledged juveniles) of birds (e.g. Little Grebe) would also be recorded.  The coverage of water and PFA filling activities in the Middle Lagoon as well as post-construction phase activities of the STF and associated facilities would be recorded as reference information.  Subject to the findings of avifauna record and habitat condition of Middle Lagoon, the effectiveness of the proposed mitigation measures would be reviewed as necessary.

6.5                                 Event and Action Plan

6.5.1.1                     Potential indirect impacts to the habitats and associated wildlife adjacent to the proposed STF would be resulted from increased human disturbance during construction and operation.  The effectiveness of mitigation measures to minimize potential impacts to habitat and wildlife is assessed through ecological monitoring programme.  However, it is recognised that the habitat conditions of ash lagoons were governed by various factors such as CLP’s pulverised fuel ash (PFA) filling activities and rainfall.  Due to the volatile and unstable nature of the ash lagoon habitat, it is considered inappropriate to expect the wildlife would utilise the habitat in an invariable manner.  Monitoring results collected during the construction and post-construction phase should be evaluated against the Event and Action Plan.  Evaluation should be based on recorded changes in:

·        Relative Abundance and species diversity of birds recorded in the monitoring area of Middle Lagoon

·        CLP’s pulverised fuel ash (PFA) filling activities in the Middle Lagoon

·        Coverage of water in the Middle Lagoon

·        The construction phase activities under the Project (for Construction Phase Monitoring only)

·        The post-construction phase activities of the STF and associated facilities (for Post-construction Phase Monitoring only)

6.5.1.2                     The Event and Action Plan is discussed in Table 6.1.

Table 6.1        Event and Action Plan

Parameter

Event

Action

Construction Phase

Relative abundance and species diversity of birds recorded in the monitoring area of Middle Lagoon

Relative abundance and species diversity of birds decreased in any three successive monitoring events

Step 1- Review site condition

 

Step 2 - Check the implementation of mitigation measures

 

Step 3- Review and adjust the mitigation measures as appropriate

Post-construction Phase

Relative abundance and species diversity of birds recorded in the monitoring area of Middle Lagoon

Relative abundance and species diversity of birds decreased in any two successive monitoring events

Step 1- Review site condition

 

Step 2 - Check the implementation of mitigation measures

 

Step 3- Review and adjust the mitigation measures as appropriate

 

6.5.1.3                     The proposed ponds created inside the STF is expected to support a small population of Little Grebe associated with the affected lagoon habitat.  No specific event and action plan are recommended.  The effectiveness of the created pond will be reviewed and adaptive management measures will be proposed as appropriate and details of these review and management protocols will be included in the HCMP.