1.2 Site Description and Alignment
3.1 Construction Noise Impacts
3.2 Operational Phase – Rail Noise Impacts
3.3 Operational Phase – Fixed Plant Noise
4.1 Construction Phase
4.2 Operational Phase
Ove Arup & Partners (OAP) was commissioned by Kowloon Canton Railway Corporation (KCRC) as the EIA Consultant for the Light Rail Transit (LRT) works for Tin Shui Wai Reserve Zone and Grade Separation of the LRT with Pui To Road and Tsing Lun Road in Tuen Mun.
This study is classified as a Designated Project under Section A.2 of the Schedule 2, Part 1 the Environmental Impact Assessment Ordinance (EIAO). An EIA study has been carried out in accordance with the requirements stipulated in the study brief (ref: EIA Study Brief No: ESB-027/1999).
The potential environmental impacts arising from the proposed works have been assessed in the EIA report. The impact assessment includes air quality, noise, water quality, waste management, landscape, visual and cultural heritage.
The proposed light railway extension and alteration works are located in Tin Shui Wai and Tuen Mun (Appendix 1). The light railway in Tin Shui Wai Reserve Zone is approximately 2.6km long and has 6 stops.
The grade separation work in Pui To Road and Lam Tei involves elevating the existing trackworks near Junctions J6, Mj7, Mj8 and LT1. The future horizontal alignment would generally follow the existing alignment. For the viaduct at LT1, a safety enclosure will be provided for the entire viaduct due to the constraints imposed by the overhead electricity power lines. Temporary track diversion will be located directly to the west of the existing track. The temporary track will be on ballast and at grade.
For the viaduct section in Pui To Road Grade Separation, a composite structure consisting of a concrete deck supported by steel portals will be adopted. All the steel elements of the portals will be encased in concrete. Except for the track directly underneath the deck of the future West Rail Tuen Mun Station, ballast track will be employed. Temporary track diversion in Pui To Road will be close to the existing track.
Since site formation work has been mostly completed, extensive excavation works is not anticipated. The key construction activities to be carried out will include minor site clearance and laying of ballast and track. There will also be some minor extent of bore piling and the construction of superstructure for the viaduct at Junction C.
These activities will be controlled under the Air Pollution Control (Construction Dust) Regulation as Notifiable and Regulatory Works and not anticipated to generate large amount of construction dust. Air pollution control measures are recommended to put into the Particular Specification (PS) for the civil work to mininise any potential dust nuisance. The Contractor is therefore obliged to follow the procedures and requirements given in the PS and Regulation. An environmental monitoring and audit programme will be carried out to ensure that the construction dust impacts are controlled with the HKAQO.
The dominant construction work will include at-grade alignment, viaduct and LRT stops. These work will adopt a large number of Power Mechanical Equipments (PME). These equipment will create potential noise impact on the nearby Noise Sensitive Receivers (NSRs). The major equipment adopted will include:
· excavator/loaders, graders, vibratory rollers and dump trucks for site formation activities;
· concrete lorry mixers and pokers for stop construction;
· mobile crane and tampering machine operation for track laying; and
· reverse circulation drills, concrete lorry mixers and pokers for piling and superstructure works.
Construction of grade separation work will be taken place at the same time as that for the KCRC West Rail, cumulative impact has therefore been considered.
It is understood that work at evening, night time and Public Holidays are not normally required, assessments have therefore been focussed on the day-time construction noise impacts. Where works are desired outside the normal day-time period, the Contractors shall apply for a Construction Noise Permit (CNP) from EPD.
Under the “Do-nothing” Scenario, most of the NSRs will exceedance the daytime construction standards. The worst affected locations are Tuen Mun Town Plaza Block 1 at Pui To Road, and 2-storey residential house at LT1 Junction. Whereas for the Reserve Zone, the worst affected locations will be Tin Shui Wai Area 31 Phases 1 & 2 Primary Schools.
Good site practices therefore have been proposed to reduce the impact. These measures will include use of “quiet PME”; scheduling of construction works outside school examination periods; use of site hoarding or movable barriers to screen noise at ground level zone; delocalization of equipment and/or local reduction of the number of plant to be used on site; and limiting the operating time of construction equipment or use of smaller equipment.
With the implementation of all mitigation measures as detailed in the EIA report, construction noise impacts at all NSRs will be controlled to within the acceptable levels in accordance with the TM-EIA requirements. An environmental monitoring and audit programme will also be conducted to ensure that compliance of the noise criteria will be maintained at sensitive receivers and implementation of noise mitigation measures will be carried out effectively.
Operational noise impacts from the LRT have been assessed under the “Normal”, “Abnormal” and “Emergency” Conditions. Cumulative impact from KCRC West Rail has also been included in the assessment. The rail noise levels at the facades of the existing and future sensitive receivers have been predicted.
The structure re-radiated noise from the concrete viaduct has been measured at the existing LRT line. There will be no significant impacts on the NSRs from the structure re-radiated noise.
Results indicate the cumulative noise impacts would be within the stipulated noise criteria. Nevertheless, recommendations are still given to the railway operator and the Detailed Design Consultants to ensure compliance with the requirements given in TM-EIA.
Since the key fixed plant noise will be originated from the rectifier station, the orientation of the open side of transformer bays are recommended to be faced away from the nearest NSRs, and preferably facing onto a main road, if practicable. Adequate noise attenuation treatments (eg silencers, acoustic louvres) have been proposed for the ventilation system of rectifier station to ensure compliance with the relevant noise criteria. With the implementation of the mitigation measures and suitable design, fixed plant noise impact are not anticipated.
During the construction operation, the nearest water sensitive receivers include Tin Shui Wai Nullah for the Tin Shui Wai Reserve Zone, and Tuen Mun River Channel for the Grade Separations at Pui To Road and Lam Tei. The dominant impacts would be associated with surface runoff which could cause elevation of suspended solids.
However, the EIA report has identified that the water quality impacts will generally be temporary and localised. If mitigation measures are implemented properly, there will be no adverse water quality impacts. These mitigation measures will include the provision of adequate construction site drainage and treatment facilities and the adherence to the best management practices (stated in ProPECC PN1/94).
EIA report has concluded that minimal operational water quality impacts are expected if appropriate drainage and effluent collection systems are adopted and incorporated. These systems will include provision of surface water drainage system in order to collect the track runoff. Where oil and lubricating fluids could be spilled, the track drainage channels discharge should pass through oil/grit interceptors/chambers, or a sub-soil drainage system to remove oil, grease and sediment before being pumped to the public stormwater drainage system.
The potential impacts of waste arising from the construction and operational stages of the project have been assessed as minor and insignificant. It is recommended that potential impacts can be avoided or controlled to acceptable levels through effective waste management planning, effective management of chemical/industrial and other potentially hazardous wastes, and proper storage of reusable material.
The EIA consultant has conducted a cultural heritage assessment for the proposed LRT works. Relevant studies conducted for West Rail have been reviewed. The records maintained by AMO on the list of declared and deemed monuments, and location of sites of archaeological interest have also been reviewed. Results indicate that the construction and operation of the proposed LRT would not have adverse impacts on the cultural and heritage aspects.
During construction phase the Contractor will carry out an archaeological evaluation. A minimum of 5% sampling for the support columns of the viaduct will be used. The selected column footings would be pre-excavated prior to the onset of construction activities in order to retrieve sufficient information. If pre-excavation of selected column is not possible, the mitigation strategy would be the posting of an archaeological watching brief.
The three package of LRT alterations that have been assessed in the EIA present different site specific landscape and visual impacts. The Tin Shui Wai Extension has the advantage of being located in planned reserves constructed as part of the road infrastructure development of the New Town. Therefore, there will be no disturbance of other land uses or landscape features to construct the LRT in the TSW Reserve Zone. The appearance of the LRT will be similar to those portions of track already in use throughout Tin Shui Wai.
At Tsing Lun Road and Pui To Road Tuen Mun, the existing track has to remain in operation during viaduct construction and this will require temporary diversions. Such diversions have been carefully selected to avoid important landscape features such as Tuen Mun Town Park and mature roadside trees. Upon completion, it is proposed to reinstate areas below the LRT viaducts with planting to enhance the road amenity.
The key groups of visually sensitive receivers will be residents in housing estates adjacent to the LRT alignment and pedestrians and road users travelling alongside or crossing the tracks. The planned planting reserves in Tin Shui Wai, amentiy reinstatement planting in Tuen Mun as well as general public familiarity with the LRT in Tin Shui Wai will mean landscape and visual impacts will be generally acceptable.
An Environmental Monitoring and Audit (EM&A) Manual has been prepared for the construction phase of this development to monitor noise, air quality, water quality and waste management. Further details are given in the EM&A manual.
The EIA concludes that with the implementation of the recommended mitigation measures and monitoring of environmental conditions at sensitive receivers, the construction and operation of the proposed LRT works will have no adverse impacts on the environment.