Potential ecological impacts associated with the construction of the sewerage system and pumping stations have been identified in the EIA(DE) Report. It is envisaged that the impacts can be effectively mitigated by pursuing an approach of avoidance, minimisation, on-site compensation, and off-site compensation, in that order. At each stage, residual impacts are to be re-assessed to determine whether there is a need to proceed to the next stage of mitigation. The following measures have been developed in accordance with this approach to mitigate the identified impacts.
10.1.1 Mitigation Measures Adopted
All of the proposed sewers, rising mains and pumping stations will be located in areas classified as of low ecological value. In this way impacts to ecologically important habitats will be avoided.
10.1.2 Further Recommendations
No construction works along a section of the proposed sewerage alignment, which fall within the Deep Bay Wetland Conservation Area and the Deep Bay Wetland Buffer Area (WCA and WBA) and close to the locations of ecologically sensitive species (including Intermediate Egret, Black-faced Spoonbill, Buzzard, Imperial Eagle and Avocet) (Figure 8.7a), are recommended during the winter season (November to March). Regular inspections (at least twice a month) should be carried out during the winter season to ensure proper implementation of this restriction.
10.2.1 Mitigation Measures Adopted
Where the sewers and rising mains
crossover the existing MDC within the WCA and WBA, the pipe jacking method will
be adopted instead of dredging. It
is expected that the construction noise will be restricted to the pit area
only, as noisy powered mechanical equipment such as the hydraulic jack will mainly
be underground. Therefore the
noise impact and disturbance to the MDC will be greatly reduced.
The use of temporary noise barriers, in the form of site hoarding, along the boundary of the pumping station site is considered to be a practicable and an effective mitigation measure to further reduce the noise impacts associated with the construction of the pumping station
10.2.2 Further Recommendations
For construction activities of the remaining sections of the proposed sewerage alignment (including parts of S4, S5 and S6) within the WCA and WBA during winter, regular inspections by an Environmental Team (at least twice a month) should be carried out during the winter season (November to March) to check the number of workfronts and proper implementation of mitigation measures such as erection of movable noise barriers. The Environmental Team should report the details in the Monthly EM&A Report. An Independent Environmental Checker should review the regular inspections of the Environmental Team and the Contractor is responsible to ensure the proper implementation of the recommended mitigation measures.
With the implementation of the mitigation measures proposed below (and in Sections 8.7.1 & 8.7.2 of the EIA (DE) Report), and given that only a small area will be lost due to the Project and the impact is generally considered as low, no habitat compensation is required.
Since no construction works within the sections of the sewerage alignment which unavoidably fall within the Deep Bay Wetland Conservation Area and the Deep Bay Wetland Buffer Area (WCA and WBA) and those sections close to the location of ecologically sensitive species (including Intermediate Egret, Black-faced Spoonbill, Buzzard, Imperial Eagle and Avocet) (Figure 8.7a) are recommended during the winter season (November to March), regular inspections (at least twice a month) should be carried out during the winter season to ensure proper implementation of such requirement..
For the unavoidable schedule with the remaining sections of the sewerage alignment (including parts of S4, S5 and S6) within the WCA and WBA during winter, regular inspections by an Environmental Team (at least twice a month) should be carried out during the winter season (November to March) to check the number of workfronts and proper implementation of mitigation measures such as erection of movable noise barriers with a suitable footing along the sites. The Environmental Team should report the details in the Monthly EM&A Report. An Independent Environmental Checker should review the regular inspections of the Environmental Team and the Contractor is responsible to ensure the proper implementation of the recommended mitigation measures.
In order to ensure that the Contractor has implemented the recommendations of the EIA(DE) Report, the IEC shall be responsible for checking the effectiveness of the Contractors working practices and implementation of mitigation measures as outlined in this section (this should form part of the regular IEC audit programme). In particular, the site audits should review the working practices of the Contractor at the WCA/WBA during the construction phase of the Project.
The following mitigation measures are recommended to minimise disturbance to the surrounding habitats.
· Use of quietened construction plant and equipment (refer to Table E2 in Annex E) for the construction of pumping station (P3) and sewerage alignments (S4, S5 and S6) located within the Deep Bay Wetland Conservation Area and the Deep Bay Wetland Buffer Area, as well as pumping station P2 located beside Sha Po marsh (location refer to Figure 8.4b in the EIA(DE) Report), to minimise the noise impact to the wildlife, particularly rare birds.
· Erect fences along the boundary of pumping station construction sites (P1 to P7) before the commencement of works to prevent tipping, vehicle movements, and encroachment of personnel into adjacent areas; particularly at sites close to the Humped Fig Tree Ficus tinctoria subsp. gibbosa (pumping station P7, refer to Figure 8.4b in the EIA(DE) Report and P2) to avoid disturbance to the remaining pond areas (0.7a).
· Avoid any disturbance, particularly filling and illegal dumping, to the remaining abandoned fishpond where pumping station P2 is to be constructed.
· Prevent stream and pond (P2) sedimentation during construction, particularly during the construction of pumping stations (P1 to P7), through the erection of sediment barriers and operation of siltation traps in streams which could potentially be affected.
· Treat any damage that may occur to individual major trees in the adjacent area with surgery.
· Reinstate temporary work sites/disturbed areas immediately after completion of the construction works, i.e. through on-site tree/shrub planting. Tree/shrub species used for reinstatement works should compliment those species in surrounding area.
· Regularly check the work site boundaries to ensure that they are not exceeded and that no damage occurs to surrounding areas, particularly at the location of pumping station P2.
· Prohibit and prevent open fires within the site boundary during construction and provide temporary fire fighting equipment in the work areas.