Section	Title	Aims
1	Introduction	An introduction of the background information and the layout of the EIA report
2	Project Description	A description of the extent and details of the project available
3	Study Objectives and Scope	Outline the objectives and scope for various environmental aspects
4	Available Technical Information	List the key information reviewed in this EIA study
5	Air Quality Assessment	Present the legislation, methodology and recommendations for air quality impacts during construction phase
6	Operational Noise Assessment	Present the legislation, methodology and recommendations for operational noise impacts
7	Construction Noise Assessment	Present the legislation, methodology and recommendations for construction noise impacts
8	Water Quality Assessment	Present the legislation, methodology and recommendations for water quality impacts
9	Waste Management Implications	Present the legislation, methodology and recommendations for waste management
10	Cultural Heritage Assessment	Present the legislation, methodology and recommendations for cultural heritage
11	Landscape and Visual Impacts	Present the legislation, methodology and recommendations for landscape and visual impacts
12	Environmental Monitoring and Auditing Programme	Present the legislation, methodology and recommendations for EM&A
13	Recommendations and Conclusions	Summary of the findings and recommendations
14	Summary of Environmental Outcomes	Summarise environmental outcomes and benefits
15	Implementation Schedule	Summarise implementation responsibility for environmental mitigation measures
16	References	List of relevant reference information

Description	Date
Final Assessment Report, West Kowloon to Tuen Mun Centre, Contract No. TS-900 Environmental Impact Assessment Report	Feb 1999
Final Assessment Report, Technical Annexes, Contract No. TS-900, Environmental Impact Assessment	Feb 1999
Environmental Monitoring and Audit Manual, West Kowloon to Tuen Mun Centre, Contract TS-900, Environmental Impact Assessment	Sept 1998
Archaeological Action Plan, Contract DD901, Environmental Support Services	Feb 1999
Essential Public Infrastructure Works, Final EIA Report, Contract No. DD-901, Environmental Support Services	May 1999
Supplement to the Archaeological Action Plan, The Au Tau Area, Contract No DD-901, Environmental Support Services	May 1999
Agreement No CE 66/96, Planning and Development Study on North West New Territories, Environmental Assessment, Technical Paper No. 6, Report No. 0208/TEC/T6.1	Apr 1999
Agreement No CE 10/95, Tin Shui Wai Development, Engineering Investigations for Development of Areas 3, 30 & 31 of the Development Zone and the Reserve Zone, Final Investigation Report, Vol 1 - Main Text, Executive Summary, EIA	Mar 1997
Agreement No CE 12/97, Tin Shui Wai Further Development, Design and Construction – Intensification of Areas 104 and 108b, Feasibility Assessment on Noise, Air Quality and Solid Waste Impacts, 0188/ENG/R6.2	Jun 1998
Agreement No CE 12/97, Tin Shui Wai Further Development, Intensification of Areas 104 and 108b, Final Report on Sewerage Impact Assessment, 0188/ENG/R4.2	Jun 1998
Agreement No CE 12/97, Tin Shui Wai Further Development, Intensification of Areas 104 and 108b, Final Report on Traffic Impact Assessment, 0188/ENG/R5.2	Jun 1998
Lam Tei & Yick Yuen - Outline Zoning Plan, S/TM-LTYY/1	Jun 1996
Tuen Mun - Outline Zoning Plan, S/TM/11	Jan 1999

	Concentration in micrograms per cubic metre (i)
Sulphur Dioxide	800		350		80
Total Suspended Particulates	500		260		80
Respirable Suspended Particulates (v)			180		55
Carbon Monoxide	30,000	10,000
Nitrogen Dioxide	300		150		80
Photochemical Oxidants (as ozone) (vi)	240
Lead				1.5

6 Operational Noise Assessment

6.1 Legislation and Standards

6.1.1 Railway Noise Criteria – Airborne Noise

Railway noise is controlled under the Noise Control Ordinance (NCO)^[5] and the associated Technical Memorandum on Noise from Places Other Than Domestic Premises, Public Places or Construction Sites (TM-Places) ^[14] .

The acceptable Noise Levels (ANLs) for different Area Sensitivity Ratings (ASRs) are summarised below:

ASR	Time Period ^{(see Note 1)}	Acceptable Noise Levels (ANL), L _{eq, 30 min}
A	Day & evening	60 dB(A)
	Night	50 dB(A)
B	Day & evening	65 dB(A)
	Night	55 dB(A)
C	Day & evening	70 dB(A)
	Night	60 dB(A)

Table 6.1: Acceptable Noise Levels (ANLs)

Note 1: Day : 0700 to 1900 hours

Evening : 1900 to 2300 hours

Night : 2300 to 0700 hours

Additional corrections shall also be applied if the measured noise level is qualified for tonality and intermittency.

The TM-EIA ^[13] and HKPSG ^[19] also provide criteria for railway noise. These criteria are given below:

Parameters	Criterion, dB(A)	Ref
Maximum A-weighted sound pressure level, L_max (2300-0700hrs)	85	TM-EIA
Equivalent Continuous Sound Level, L_{eq (24 hours)}	65	HKPSG

Table 6.2: Noise Criteria Stipulated in TM-EIA and HKPSG

6.1.2 Fixed Plant Noise Criteria

Similar to railway noise, noise from associated fixed plant (eg rectifier station) is controlled by the NCO. In addition, according to TM-EIA, fixed plant noise should also be designed to be 5dB(A) below the ANL stipulated in the TM-Places. A summary of the noise limits for fixed plant is given in the following table.

		Noise Limit, L _{eq, 30 min}, dB(A)
ASR	Time Period ^{(see Note 1)}	ANL	HKPSG
A	Day & evening	60	55
	Night	50	45
B	Day & evening	65	60
	Night	55	50
C	Day & evening	70	65
	Night	60	55

Table 6.3: Noise Levels for Fixed Plant Noise

Note 1: Day : 0700 to 1900 hours

Evening : 1900 to 2300 hours

Night : 2300 to 0700 hours

6.2 Noise Sensitive Receivers (NSRs)

6.2.1 NSR Locations

The study area for the noise impact assessment will include all noise sensitive receivers within 300m from the project boundaries. With the shielding from the first row of building blocks, the second row of NSRs will generally be protected. The assessment therefore focuses on the first row of NSRs that have direct line of sight to the operating trains within the project boundaries.

NSRs are chosen in accordance with Annex 13 of the TM-EIA. Both existing and future planned uses will be included. The existing NSRs are identified through desktop review and site surveys. The planned NSRs are identified in the latest Outline Zoning Plans. The drawings in Appendix 2 illustrate the location plans and detailed descriptions of the NSRs proposed for the EIA study. A summary of these sensitive receivers is given below:

NSR / Use	Horiz dist to rail / viaduct	Remarks
Schools along Tin Fuk Road	30 – 50m	With openable windows
Schools along Tin Shing Road	25 – 70m	With openable windows
Residential blocks	30 – 50m	With openable windows
Retail & hotel	30m	With sealed glazing and central A/C

Table 6.4: Summary of Noise Sensitive Receivers close to the Alignment

6.2.2 Area Sensitivity Ratings

Appendix 2 also presents the Area Sensitivity Ratings (ASRs) for the identified NSRs assumed for the assessment of operational noise impacts. The ASRs for the NSRs are determined by reviewing the traffic flow data available, the TS-900 EIA report for West Rail and the existence of any Influencing Factors.

The following table summaries the ASRs for the identified NSRs.

NSRs

ASRs

Residential blocks / schools along Tin Fuk Road

Residential blocks / schools along Tin Shing Road

Table 6.5: Summary of Area Sensitivity Ratings for Identified NSRs

The ASRs assumed are indicative only based on the latest information available. It should be noted that fixed noise sources are controlled under Section 13 of the NCO. At the time of investigation, EPD will determine noise impact from concerned fixed noise sources on the basis of prevailing legislation and practices being in force, taking account of contemporary conditions / situations of adjoining land uses.

6.3 Airborne Noise Assessment

6.3.1 Assessment Methodology

6.3.1.1 Train Noise Data and Operational Data

KCR has provided the train noise data in L_max for LRV (both new and existing trains). The L_max data has been converted to SEL using established train noise prediction methodology^[25]. A summary of the noise data and the corresponding operating conditions is given below:

Parameters	Noise Data / Operating Conditions
L_max	: 65 dB(A)
Track form	: Ballast track in well maintained condition
Speed	: 50kph
Distance	: 25m
Length of train	: 40m (for 2-car trains)

Table 6.6 Summary of Train Noise Data Provided by KCR

6.3.1.2 Correction for Rail Deterioration

A 3dB(A) correction is included in the prediction model to allow for the rail deterioration.

6.3.1.3 Correction for Train Speeds

The train speeds for various rail sections are prepared by KCRC and LRT (Appendix 4). These speeds are the practical average travel speed, taking into account the speed limits at junctions and across roads.

The correction of L_max for train speeds is based on the following equation ^[25]:

Change of L_max with speed = 30 log (V₁ / V₂) dB(A)

Where V₁ and V₂ are the average train speeds.

6.3.1.4 Correction for Distance

The correction of L_max for distance is based on the following equation:

Change of L_max with distance = 10 log (d₁ / 25) dB(A)

Where d₁ is the distance between track and receiver.

6.3.1.5 Correction for Deck Reflection

Except for the viaduct across Junction C at Tin Shui Wai Phase 4, ballast track would be used. On the viaduct section, non-ballast low-vibration track would be used. The following corrections are applied for the reflection from the deck of viaduct.

· Viaduct with ballast track = 1.5dB(A)

· Viaduct without ballast track = 2.5dB(A)

6.3.1.6 Correction for Joints

There will be no cross-over in the proposed LRT. A 7dB(A) correction is included in the model to represent the argumentation in noise due to thermal expansion joints.

It has been advised by KCR that Continuously Welded Rail (CWR) will be adopted for the proposed LRT works. There would be neither thermal expansion joints nor structural breaks for the rail on viaduct.

6.3.1.7 Wheel Squeal

Wheel squeal would occur when wheelset negotiate sharp curves. For non-resilient wheels, researches have indicated that it may have squeal when the radius of curvature is less than 100 times of the wheelbase ^[25]. Other study ^[31] has concluded that resilient wheels are effective measures to control wheel squeal noise. That report also quoted that the use of resilient wheels would control squeal noise for radius of curvature less than 30m.

It has been advised by KCR that both the existing and future LRT trains are provided with resilient wheels, with a wheelbase of about 1.9m. For a conservative assessment however, this assessment has incorporated wheel squeal correction of 3dB(A) for curves with radius of curvatures less than 200m. For NSRs within 25m from such a curve, an additional correction of 3dB(A) would be allowed.

6.3.1.8 Conversion to SEL

The calculation of SEL from L _max is based on the following equation ^[25]

SEL = L _max + 10 log (L/V) +10.5 –10 log (4D / (4D²+1) + 2 tan^-1 (1/2D))

Where L = train length, m

V = train speed, kph

d = Distance from track, m

D = d / L

6.3.1.9 Correction for Train Frequency

The predicted train frequencies (for up to Year 2011) during AM peak hour for various alignment sections has been provided by KCR .

It has also been advised by LRT that the hourly train frequency during early morning before 0700 hours (ie 0630 to 0700 hours) would be 100% of the AM peak (Appendix 4). The train frequency during AM peak will therefore be adopted for the night-time noise assessment.

The correction of SEL for train frequency is calculated based on the following equation:

Change of SEL with train frequency = 10 log (N₁) dB(A)

Where N₁ is the train frequency for the rail segment.

6.3.1.10 View Angle

The correction for view angles is based on the following equation:

Change of SEL with view angle = 10 log (f/180) dB(A)

Where f is the view angle.

6.3.1.11 Correction for Façade Reflection

A 2.5dB(A) correction will be applied for all receivers to account for the façade reflection effect.

6.3.1.12 Cumulative Noise Impacts from West Rail

The proposed LRT alignments are arranged alongside the West Rail alignment in Tin Fuk Road. For NSRs that are affected by both the LRT and West Rail alignments, additional noise contributions from West Rail has been included in the noise assessment to determine the cumulative noise impacts. The noise contributions from West Rail were extracted from the West Rail calculations (Appendix 5).

6.3.1.13 Structure Re-radiated Noise from Viaduct Structure

In order to estimate the magnitude of re-radiated noise from viaduct structure, noise measurements have been conducted to establish the noise re-radiated from existing LRT viaduct structures.

The location was close to Junction MJ9 (ie under the viaduct connecting Fung Tai Stop and Siu Hong Stop, and near Tuen Mun Government Primary School). The measurement location was directly underneath the existing concrete viaduct, with a head room of approximately 5-6m. Ballast track was installed. Trains were travelling at approximately 40-50kph.

The measured train noise levels are corrected to a distance of 25m (Figure 6.1) for comparison with the train noise data provided by KCR. A summary of the comparison is given below:

Location	Measured L _max,dB(A)	Dist corr, dB(A)	Corrected L_max, dB(A)	LRT Noise Data, L_max dB(A)
Near Tuen Mun Government Primary School	60 – 63	-8	52 – 55	65

Table 6.7: Comparison of Measured Structure Re-radiated Noise and KCR’s Noise Data

The corrected structure re-radiated noise levels are at least 10dB(A) less than the noise data of 65dB(A) L_max (at the reference conditions) provided by KCR. In this respect, the noise contribution from structure re-radiated noise from concrete viaduct structure would be more than 10dB(A) below the calculated airborne noise impacts. Since the cumulative noise impacts (ie with contributions from West Rail) will be controlled to within the ANL limits, the structure re-radiation noise would not have significant contributions on the cumulative noise impacts.

6.3.1.14 Normal, Abnormal and Emergency Operation

As advised by LRT, the definitions of Normal, Abnormal and Emergency Operations for LRT are as follows (see Appendix 6):

Normal The day-to-day operations without any interruption causing service delay.

Abnormal - The planned or expected event / happening which is not day-to-day or infrequent nature (eg engineering or operational adjustment catering for extended LRV services) or incidents resulting in service disruption less than 20 minutes).

Emergency - An unexpected occurrence that has environmental impact (eg spillage of chemical) or major incident as defined in the Procedure Manual of Contingencies.

Under the “Abnormal Operations”, the operation time of LRT will be extended from 0130 hours by another 1 –2 hours. These “Abnormal Operations” will occur during special periods (eg Chinese New Year and Christmas). Although the services period is extended in these occasions, the hourly train frequency will remain the same as that during “Normal” operation. The noise assessment during “Normal” operations will therefore also cover the “Abnormal” operation periods.

6.3.2 Assessment Results

The controlling noise parameter would be the night-time noise impacts (ie L_{eq, 30 min}) since the train frequency during early morning (ie 0630 to 0700) would be 100% of AM peak and the noise criterion before 0700 hours would be the one for night-time period. Given that the L_max is only 65dB(A) at 25m from track, all the NSRs would not be exposed to noise levels exceeding the stipulated 85dB(A) L_max criterion.

Air-borne rail noise prediction has been conducted according to the methodology described above. Appendix 7 presents a summary of the predicted cumulative train noise impacts.

Results indicate that the cumulative noise impacts (for year up to 2011) at all the NSRs would be within the stipulated noise limits. A summary of the predicted cumulative noise impacts for representative NSRs is given below (see Appendix 7 for details):

NSR	Description	Predicted Noise Impacts, dB(A)	Criteria, dB(A)	Compliance
N2	Yiu Foo House	55*	55	Yes
N10	Yau Hong House	55*	55	Yes
N15	The Church of Christ in China Hong Kong Council Fong Yun Wah School	56	65	Yes
N19	Tse Sum House (HOS)	55*	55	Yes
N27	Tin Shui Wai Catholic Primary School	51	65	Yes
N31	Lynwood Court (Blk 1)	54	55	Yes

Table 6.8 : Summary of Predicted Cumulative Noise Impacts (up to 2011) at Typical NSRs

* with West Rail contribution

6.4 Fixed Plant Noise Assessment

6.4.1 Noise Sources

The proposed LRT works include a rectifier station (ie R14 for the Tin Shui Wai Phase 4 Extension) that is a potential fixed noise source. It has been advised that the transformer to be installed in the rectifier stations would be similar to those that have been currently installed in Tuen Mun and Tin Shui Wai areas. Transformer bays will be provided with a concrete cover and opened on one side. Other equipment (eg switching gears) will be accommodated in plant rooms.

6.4.2 Assessment Methodology

Noise measurement results indicate that the outdoor transformers in existing rectifier stations would generate a noise level of 64 – 66dB(A) at a distance of 2m, when there are two transformers operating simultaneously. The measurements were taken during peak hour when the loading of the transformers was close to the maximum.

The assessment assumes “point source” dispersion with correction factors of 3dB(A) for tonality and 3dB(A) for façade effect. Possible screening effects from the rectifier station structure have not been included for a conservative assessment. All the transformers in the rectifier stations are assumed to be operating in the noise assessment.

6.4.3 Assessment Results

6.4.3.1 Transformer Noise

The noise impacts caused by the transformers have been conducted based on the measured transformer noise levels and the methodology described above. Calculations indicated that the predicted noise impacts, based on the measured noise data for existing transformers, would be in the range of 38-39 dB(A) for the NSRs near R14. These noise levels are within the NCO-5 limit of 50dB(A). Calculations of noise impacts are presented in Appendix 9.

Although the predicted noise impacts are within the specified noise limits, the Detailed Design Consultant is still recommended to orientate the transformer bays in such a way that the open sides are not facing the nearest NSRs, and preferably facing onto a main road, if it is practicable.

6.4.3.2 Other Noise Sources

Other potential noise sources in rectifier station include the ventilation system for switch rooms. It is recommended that a review to be conducted during the Detailed Design Stage to ensure that adequate noise attenuation treatments (eg silencers, acoustic louvres) are incorporated into the detailed design of the ventilation system to ensure compliance with the relevant noise criteria.

6.5 Recommendations

The findings of operational noise assessments indicate that there would not be any adverse impacts on the neighbouring NSRs. It is not required to implement specific noise mitigation measures for the proposed LRT Works. However, the following recommendations should be implemented during the design and operational stages of the proposed works.

· The railway operator should ensure that the worst-case noise level of 65 dB(A) L_max at 25m from straight and well maintained ballast track is always achieved.

· The Detailed Design Consultant should ensure that the structure re-radiated noise from viaduct structure is at least 10dB(A) below the noise criteria of 65 dB(A) L_max at 25m, at 50kph.

· The Detailed Design Consultant should ensure that the noise level at 2m from the transformer bays in the rectifier would be less than 66dB(A).

· The Detailed Design Consultant should orientate the open side of transformer bays in rectifier station to face away from the nearest NSRs, and preferably facing onto a main road, if practicable.

· The Detailed Design Consultant should conduct a detailed review on ventilation systems in the rectifier stations to determine the need for any noise attenuation (eg silencers, acoustic louvres etc).

6.6 Conclusion

Assessments of airborne noise and structure re-radiated noise have been conducted based on the train noise data provided by KCR and the methodology described in this section. Results indicate the cumulative noise impacts would be within the stipulated noise criteria. Recommendations are given for the railway operator and the Detailed Design Consultants to ensure compliance with the requirements given in TM-EIA.

7 Construction Noise Assessment

7.1 Legislation and Standards

Control over the generation of construction noise in Hong Kong is governed by the NCO ^[5] and the EIAO ^[2] and their subsidiary requirements. Various Technical Memoranda (TMs) have been issued under the NCO and the EIAO to stipulate control approaches and criteria. These TMs prescribe the maximum permitted noise levels for the use of Powered Mechanical Equipment (PME) and certain construction activities and processes, according to the type of equipment or activity, the perceived noise climate of the area, and the working hours of equipment operation and usage. The TMs applicable to the control of noise from construction activities in current proposed LRT works are:

· Technical Memorandum on Noise from Construction Work other than Percussive Piling ^[15] (TM-CW);

· Technical Memorandum on Noise from Construction Work in Designated Areas ^[16] (TM-DA); and

· Technical Memorandum on Environmental Impact Assessment Process ^[13] (TM-EIA).

7.1.1 Noise Standards in Normal Working Hours

Noise arising from general construction works during normal working hours is governed by the TM-EIA under the EIAO. The following table presents the recommended noise standards.

Uses	Acceptable Noise Standards L_{eq (30mins)}, dB(A)
All domestic premises including temporary housing accommodation	75
Hotels and hostels	75
Educational institutions including kindergartens, nurseries and all others where unaided voice communication is required	70 65 (During examinations)

Note: The above standards apply to uses that rely on opened windows for ventilation.

Table 7.1: Noise Standards for Daytime (0700 to 1900 hours) Construction Activities

In accordance with the TM-EIA, the noise criteria as laid down in the above table for the construction of designated project shall be met as far as practicable. All practicable mitigation measures shall be exhausted and the residual impacts are minimised.

7.1.2 Noise Standards in Restricted Hours

The NCO provides statutory controls on general construction works during the restricted hours (ie 1900 to 0700 hours from Monday to Saturday and at any time on Sundays or public holidays). The use of Powered Mechanical Equipment (PME) for construction works during the restricted hours would require a Construction Noise Permit (CNP). The TM-CW details the procedures adopted by EPD for assessing such application. The granting of a CNP is subject to conditions stated in the permit and it may be revoked at any time for failure to comply with the stated conditions.

In addition to the general controls on the use of PME during the restricted hours, the use of Specified Powered Mechanical Equipment (SPME) and the undertaking of Prescribed Construction Work (PCW) during the restricted hours in a designated area are controlled by the TM-DA. Construction plant or equipment classified as SPME under the TM-DA includes hand-held breakers, bulldozers, concrete mixer lorries, dump trucks and poker vibrators. PCW includes the erection or dismantling of formwork or scaffolding, hammering, handling of rubble, wooden boards, steel bars, or scaffolding material, and the disposal of rubble through plastic chutes.

The TM-DA details the procedures that would generally be adopted by EPD for assessing the use of SPME during the restricted hours and for determining whether a CNP would be issued.

Maximum noise levels from construction activities during the restricted hours at affected NSRs are controlled under the TMs and shall not exceed the specified Acceptable Noise Levels (ANLs). These ANLs are stipulated in accordance with the Area Sensitivity Ratings (ASRs) established for the NSRs. The ANLs for construction works in designated areas are more stringent than those given in the TM-CW, as reflected from the corresponding Basic Noise Levels (BNLs) stated in the following table.

Time Period	Area Sensitive Ratings
Time Period	A	B	C
All weekdays during the evening (1900 to 2300 hours), and general holidays (including Sundays) during the day and evening (0700 to 2300 hours)	60(45)	65(50)	70(55)
All days during the night-time (2300 to 0700 hours)	45(30)	50(35)	55(40)

Note: Figures in brackets are BNLs for SPME construction work in designated areas

Table 7.2: BNLs for Construction Noise other than Percussive Piling

According to the Noise Control Designated Area Plan no. EPD/NP/KLN-01, Tin Shui Wai Phase 4 lies within the Designated Area.

7.2 Assessment Methodology

7.2.1 Noise Prediction Methodology

Under the current plan of construction schedule from periods March 2001 to November 2003, the construction works would be carried out at normal working hours only (ie 0700 to 1900 hours on any day other than Sunday or public holiday) and it would not be required to carry out construction works during the restricted hours (ie 1900 to 0700 hours from Monday to Saturday and at any time on Sundays and public holidays). This assessment therefore focuses on the construction works during the normal working hours.

However, should construction works during restricted hours are found to be necessary, the Contractor shall apply for a Construction Noise Permit (CNP) from the Noise Control Authority. Despite any description or assessment made in this EIA Report on construction noise aspects, there is no guarantee that a CNP will be issued for the project construction. The Noise Control Authority will consider a well-justified CNP application, once filed, for construction works within restricted hours as guided by the relevant Technical Memoranda issued under the Noise Control Ordinance. The Noise Control Authority will take into account of contemporary conditions/situations of adjoining land uses and any previous complaints against construction activities at the site before making his decision in granting a CNP. Nothing in this EIA Report shall bind the Noise Control Authority in making his decision. If a CNP is to be issued, the Noise Control Authority shall include in it any condition he thinks fit. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

The following procedures apply to the assessment of construction noise impacts:

· locate representative NSRs that may be affected by the works;

· determine plant items for corresponding construction activities based on the agreed plant inventories with KCRC;

· determine the sound power levels of the plant items according to the information stated in the TM-CW or other recognised sources of reference, where appropriate;

· calculate the correction factors based on the distance between the NSRs and the notional noise source positions of the work sites;

· apply corrections including façade, distance, barrier attenuation, acoustic reflection where applicable, in the calculations;

· predict construction noise levels at the NSRs in the absence of any mitigation measures;

· conduct assessment of noise impacts at NSRs to quantify the level of impact, in accordance with TM-CW.

An in-house program was used to facilitate the analysis of the construction noise calculations. The initial program runs were conducted without any mitigation measures. Where noise level exceedances were identified, further runs were made assuming different combinations of mitigation measures to be incorporated to control noise impacts.

Works during the restricted hours shall be assessed in accordance with the requirements in the TM-CW and TM-DA under the NCO by the Contractors, if they desire to apply for a CNP for evening or night time works.

7.2.2 Noise Mitigation Strategy

Where noise exceedances from assessment criteria were found at the NSRs, appropriate mitigation measures would be evaluated and recommended. A systematic approach to the evaluation of mitigation measures has been adopted, consisting of four levels of mitigation (and combination of each level) as described below.

Mitigation	Description
M1: Level One	Selection of quiet plant and working methods
M2: Level Two	Construction of temporary noise barriers
M3: Level Three	Delocalization of equipment and/or local reduction of number of plant items
M4: Level Four	Limiting equipment operating time

Table 7.3: Construction Noise Mitigation Strategy

7.2.2.1 M1: Level One Mitigation Measures

Some models of plant are quieter than the standard types listed in the TM-CW. Quiet plant is defined as PME whose actual SWL is less than the value specified in the TM-CW for the same piece of equipment. The benefits achieved in using quiet plant will depend on Contractor’s selection of working method. Examples of SWLs of specific silenced PME that may be used in the construction of the project worksites are given in BS5228 Part I, detailed in Section 7.3.5.3.

7.2.2.2 M2: Level Two Mitigation Measures

In general, noise barriers of 3 to 5 metres high located on site boundaries between noisy construction activities and NSRs could give up to 5-10 dB(A) reduction from screening. With careful consideration in the location of site access for the effectiveness of the barriers, barriers in the form of site hoardings could achieve this level of reduction. Certain types of PME, such as generators and compressors, can be partially or completely enclosed to give a total SWL reduction of 15-25 dB(A). Movable barriers that can be located close to noisy plant can also be very effective at screening NSRs from particular plant. This measure is particularly effective for low-rise noise sensitive premises or schools.

7.2.2.3 M3: Level Three Mitigation Measures

For the same set of plant items, delocalization of equipment or avoiding all equipment operating at the same site location would reduce the noise impact from construction activities on nearby NSRs. This approach is very effective for construction work site of linear shape. Delocalization of identical plant may include eg separating two dump trucks (or two concrete lorry mixers or two excavators) by more than 200m apart such that they would not be operated at the same working area. For the NSR close to the construction work site (less than 50m), the noise contribution from the distant PME would be insignificant.

Selection of the number and types of construction plant is usually left to the Contractor to allow flexibility in devising efficient working methodologies. However, in combination with the selection of quiet plant and noise barriers, limiting plant numbers may be required to provide further mitigation of construction noise levels at source in critical areas.

7.2.2.4 M4: Level Four Mitigation Measures

By restricting the percentage of operation of PME to 50% within 30-minute period, a noise reduction of 3 dB(A) could be achieved. Construction plant including dump truck may be used with careful attention to ensure that the engines are switched off or only idling at low power setting when not in direct use. For these PME the operating time should be carefully controlled so that they are only operating for 15 minutes in every consecutive 30-minute period.

7.3 Construction Noise Assessment

7.3.1 Noise Sensitive Receivers

NSRs have been identified in accordance with the HKPSG and the TM-EIA. A comprehensive list of all the identified NSRs for assessment of operational noise impacts was prepared and presented in Appendix 2. These NSRs would also be affected by the construction works during the construction stage. The worst affected NSRs during the construction phase of the proposed LRT works have been considered.

The landuses in the vicinity of the proposed alignment and LRT stops include schools and residential developments. The key representative NSRs for construction noise assessment are listed in the table below. The separation distances of the NSRs to the construction sites are described in detail in Appendix 10.

Site Area	NSR	Description
Tin Shui Wai Phase 4 Extension	N1	Queen Elizabeth School Old Student's Association Primary School
	N2	Yiu Foo house
	N4	Yiu Man House
	N6	TWGH's Kwok Yat Wai College
	N7	Yiu Yat House
	N10	Yau Hong House
	N12	Yau Tai House
	N14	Yiu Fung House
	N15	The Church of Christ In China Hong Kong Council Fong Yun Wah School
	N16	3-storey residential block
	N17	3-storey residential block
	N18	3-storey residential block
	N21	Tse Yan House (Rental Block)
	N22	Tse Yan House (HOS)
	N23	Tsz Ping House
	N25	Buddhist To Chi Fat She Yeung Yat Lam Memorial School
	N27	Tin Shui Wai Catholic Primary School
	N29	Kenswood Court (Block 14)
	N31	Lynwood Court (Block 1)
	N33	Queen Elizabeth School Old Student's Association Secondary School

Table 7.4: Listing of Key Representative NSRs for Construction Noise Assessment

7.3.2 Potential Sources of Impacts

Potential impacts on NSRs during the construction phase of the project will arise mainly from PME to be operated at the construction worksites. The proposed LRT alignment will be both at grade and elevated. The construction period would be from March 2001 to November 2003 according to KCRC. The LRT extension and alteration construction works will include the following key activities:

· at-grade alignment construction;

· standard viaduct construction (R.C. structure); and

· LRT stop construction.

The activities that may introduce potential noise impacts will include:

· site clearance and formation activities where it is proposed that excavator, vibratory rollers and dump trucks are used;

· LRT stop construction where it is proposed to use concrete lorry mixers and pokers;

· track laying involving a tampering machine and mobile crane operation;

· piling where it is proposed to use reverse circulation drills, concrete lorry mixers and pokers;

· pile cap construction involving excavator, concrete lorry mixer and poker operations;

· column construction where it is proposed to use concrete lorry mixers, pokers and mobile cranes; and

· superstructure construction where it is proposed to use concrete lorry mixers, pokers and mobile cranes.

The construction of the proposed LRT works involves different construction activities and plant at different stages. KCRC has provided construction plant inventories with the necessary quantity of plant to carry out the construction works. It is understood that the use of these plant and equipment would be KCRC’s preferred approach to the construction. Appendix 11 gives details of these plant inventories and construction schedules. This construction noise assessment has been based on these plant inventories for impact modelling.

A brief description of works to be undertaken at the worksite and the total SWLs for the plant in the absence of any mitigation measures are presented in the following table.

Site Area	Activity No	Construction Activities Description	Total Unmitigated SWL ⁽¹⁾, dB(A)
Tin Shui Wai Ph 4 Extension	1	Site clearance and formation (SCF)	124
	2	LRT stop construction (LSC)	122
	3	Piling (PIL)	122
	4	Pile Cap Construction (PCC)	122
	5	Backfilling (BF)	119
	6	Column Construction (CLC)	122
	7	Superstructure Construction (SSC)	123
	8	Track laying (TRL)	120
	9	Installation of Overhead Line Cable (OLC)	118

[1] Based on KCRC’s plant inventories.

Table 7.5: Total Unmitigated SWLs for Construction Activities

The construction works will generally be restricted to normal daytime working hours. Construction noise impacts are predicted in the following sections.

7.3.3 Cumulative Construction Noise Impact with West Rail Construction

It was advised by KCRC that there will be no overlapping on the construction work of LRT and West Rail at Tin Shui Wai Phase 4 area. Cumulative construction noise impact from West Rail is therefore not considered in this assessment.

7.3.4 Predictions of Impacts

Façade noise levels at the NSRs were calculated ^[27] based on the SWLs and corrections for distance attenuation given in the TM-CW. The predicted unmitigated maximum noise levels at the key representative NSRs at ground level zone during the construction phase of the LRT works are shown below. The exceedances from daytime construction noise criteria are given.

Site Area	NSR	Description	Activities in Each Construction Phase^(1,2)
Site Area	NSR	Description	SCF	LSC	PIL	PCC	BF	CLC	SSC	TRL	OLC
Tin Shui Wai	N1	Queen Elizabeth School Old Student's Association Primary School	80 (10)	78 (8)	78 (8)	78 (8)	75 (5)	78 (8)	79 (9)	76 (6)	74 (4)
Phase 4 Extension	N2	Yiu Foo house	80 (5)	78 (3)	78 (3)	78 (3)	75 (0)	78 (3)	79 (4)	76 (1)	74 (0)
	N4	Yiu Man House	78 (3)	76 (1)	76 (1)	76 (1)	73 (0)	76 (1)	77 (2)	74 (0)	72 (0)
	N6	TWGH's Kwok Yat Wai College	86 (16)	84 (14)	84 (14)	84 (14)	81 (11)	84 (14)	85 (15)	82 (12)	80 (10)
	N7	Yiu Yat House	79 (4)	77 (2)	77 (2)	77 (2)	74 (0)	77 (2)	78 (3)	75 (0)	73 (0)
	N10	Yau Hong House	82 (7)	80 (5)	80 (5)	80 (5)	77 (2)	80 (5)	81 (6)	78 (3)	76 (1)
	N12	Yau Tai House	91 (16)	89 (14)	89 (14)	89 (14)	86 (11)	89 (14)	90 (15)	87 (12)	85 (10)
	N14	Yiu Fung House	90 (15)	88 (13)	88 (13)	88 (13)	85 (10)	88 (13)	89 (14)	86 (11)	84 (9)
	N15	The Church of Christ In China Hong Kong Council Fong Yun Wah School	88 (18)	86 (16)	86 (16)	86 (16)	83 (13)	86 (16)	87 (17)	84 (14)	82 (12)
	N16	3-storey residential block	81 (6)	79 (4)	79 (4)	79 (4)	76 (1)	79 (4)	80 (5)	77 (2)	75 (0)
	N17	3-storey residential block	80 (5)	78 (3)	78 (3)	78 (3)	75 (0)	78 (3)	79 (4)	76 (1)	74 (0)
	N18	3-storey residential block	81 (6)	79 (4)	79 (4)	79 (4)	76 (1)	79 (4)	80 (5)	77 (2)	75 (0)
	N21	Tse Yan House (Rental Block)	83 (8)	81 (6)	81 (6)	81 (6)	78 (3)	81 (6)	82 (7)	79 (4)	77 (2)
	N22	Tse Yan House (HOS)	84 (9)	82 (7)	82 (7)	82 (7)	79 (4)	82 (7)	83 (8)	80 (5)	78 (3)
	N23	Tsz Ping House	78 (3)	76 (1)	76 (1)	76 (1)	73 (0)	76 (1)	77 (2)	74 (0)	72 (0)
	N25	Buddhist To Chi Fat She Yeung Yat Lam Memorial School	73 (3)	71 (1)	71 (1)	71 (1)	68 (0)	71 (1)	72 (2)	69 (0)	67 (0)
	N27	Tin Shui Wai Catholic Primary School	78 (8)	76 (6)	76 (6)	76 (6)	73 (3)	76 (6)	77 (7)	74 (4)	72 (2)
	N29	Kenswood Court (Block 14)	81 (6)	79 (4)	79 (4)	79 (4)	76 (1)	79 (4)	80 (5)	77 (2)	75 (0)
	N31	Lynwood Court (Block 1)	81 (6)	79 (4)	79 (4)	79 (4)	76 (1)	79 (4)	80 (5)	77 (2)	75 (0)
	N33	Queen Elizabeth School Old Student's Association Secondary School	82 (12)	80 (10)	80 (10)	80 (10)	77 (7)	80 (10)	81 (11)	78 (8)	76 (6)

Note:

(1) SCF : Site Clearance & Formation; LSC: LRT Stop Construction; PIL: Piling; PCC: Pile Cap Construction; BF: Backfilling; CLC: Column Construction; SSC: Superstructure Construction; TRL: Track Laying; OLC: Installation of Overhead Line Cable.

(2) Exceedances from daytime noise criteria (Table 7.1) are shown with brackets.

Table 7.6: Unmitigated Predicted Noise Levels at Ground Level Zone of NSRs

The noise impacts at 5th floor level, 10 floor level up to 30 floor level in 5 floor level steps are also predicted, where appropriate for each NSR. Detailed analysis indicates that the predicted unmitigated maximum noise exceedances are between ground level and 5th floor level. Depending on distance and elevation of the NSR under consideration, the noise impact reduces by between 1 to 4 dB(A) for every 5 storeys.

7.3.5 Evaluation of Impacts

Predicted unmitigated construction noise levels at the NSRs are shown in Table 7.7. It should be noted that the noise levels represent worst case scenarios, since the calculations assume that all of the available plant items for a phase of works are in use for 100% of the time. In practice this is unlikely to be the case as a number of plant items will operate sequentially with spatial constraints within the work site, and all equipment items would unlikely be operated at the same location. As will be seen later, these constraints are recommended as part of the noise mitigation control strategy (M3 and M4) at some critical NSRs.

7.3.5.1 Tin Shui Wai Phase 4 Extension

Predicted unmitigated construction noise levels at the NSRs within the Tin Shui Wai Phase 4 Extension are shown in Table 7.7. In general, high noise levels were predicted during site clearance and LRT stop construction works at the majority of NSRs in the vicinity of the proposed LRT alignment.

Noise impacts up to 18 dB(A) exceedance from daytime construction standards were predicted at nearby residential and educational NSRs. The maximum noise level predicted were 91 dB(A) at Yau Tai House (N12) and 90 dB(A) at Yiu Fung House (N14) arising from site clearance and formation works involving excavation activities.

Areas of potential significant noise impacts include Queen Elizabeth Primary School (N1), Yiu Foo house (N2), TWGH’s Kwok Yat Wai College (N6), Yau Tai House (N12), 3-storey residential blocks (N16, N17 & N18), Tin Shui Wai Catholic Primary School (N27), Kenswood Court (N29), Lynwood Court (N31), Queen Elizabeth Secondary School (N33) and the neighbouring areas. These NSRs are affected by construction noise from low level floors to high level floors.

The noise generated from track laying construction works generally introduce less noise impacts. Maximum noise exceedances of 11 ~14 dB(A) at TWGH’s Kwok Yat Wai College (N6),Yiu Fung House (N14) and Fong Yun Wah School (N15) were predicted. The affected floors include ground floor, 5th floor, 10-floor and 15-floor.

It should be noted that cumulative noise impact from West Rail would not affect TWGH’s Kwok Yat Wai College (N6). Under the current construction schedules, the major construction (column construction) of West Rail will be completed on 19 February 2001, whereas the LRT construction at this area (track laying) will commence on 01 August 2001. There would be no overlapping on the construction works of LRT and West Rail at this location.

7.3.6 Recommended Mitigation Measures

The predicted noise levels show that unmitigated construction activities are likely to give rise to adverse daytime noise impacts at the majority of the NSRs in the vicinity of the proposed alignment, and mitigation measures are therefore required. Noise emissions from construction sites could be minimised by the following means:

· use of good site practices to limit noise emissions at the source;

· scheduling of construction works outside school examination periods in critical areas;

· use of “quiet PME” and working methods (M1);

· use of site hoarding as noise barriers (with careful design) to screen noise at ground level zone (M2);

· use of permanent, temporary and movable noise barriers (M2);

· delocalization of equipment and/or local reduction of the number of plant to be used on site, where practicable (M3); and

· limiting the operating time of construction equipment on site and use of smaller equipment (M4).

Based on the unmitigated construction noise calculations, the maximum allowable total sound power levels generated from plant items during daytime construction works (ie 0700 to 1900 hours) are derived, where maximum noise exceedance are predicted. The sound power level limits for the key representative NSRs are summarised in the table below.

Site Area	NSR	Description	Construction Activities^(1,2)
Site Area	NSR	Description	SCF	LSC	PIL	PCC	BF	CLC	SSC	TRL	OLC
Tin Shui Wai Phase 4 Extension	N1	Queen Elizabeth School Old Student's Association Primary School	109	109	109	109	109	109	109	109	109
	N2	Yiu Foo house	114	114	114	114	114	114	114	114	114
	N4	Yiu Man House	116	116	116	116	116	116	116	116	116
	N6	TWGH's Kwok Yat Wai College	103	103	103	103	103	103	103	103	103
	N7	Yiu Yat House	115	115	115	115	115	115	115	115	115
	N10	Yau Hong House	117	117	117	117	117	117	117	117	117
	N12	Yau Tai House	108	108	108	108	108	108	108	108	108
	N14	Yiu Fung House	104	104	104	104	104	104	104	104	104
	N15	The Church of Christ In China Hong Kong Council Fong Yun Wah School	101	101	101	101	101	101	101	101	101
	N16	3-storey residential block	113	113	113	113	113	113	113	113	113
	N17	3-storey residential block	114	114	114	114	114	114	114	114	114
	N18	3-storey residential block	113	113	113	113	113	113	113	113	113
	N21	Tse Yan House (Rental Block)	116	116	116	116	116	116	116	116	116
	N22	Tse Yan House (HOS)	115	115	115	115	115	115	115	115	115
	N23	Tsz Ping House	116	116	116	116	116	116	116	116	116
	N25	Buddhist To Chi Fat She Yeung Yat Lam Memorial School	116	116	116	116	116	116	116	116	116
	N27	Tin Shui Wai Catholic Primary School	111	111	111	111	111	111	111	111	111
	N29	Kenswood Court (Block 14)	113	113	113	113	113	113	113	113	113
	N31	Lynwood Court (Block 1)	113	113	113	113	113	113	113	113	113
	N33	Queen Elizabeth School Old Student's Association Secondary School	107	107	107	107	107	107	107	107	107

Note:

(2) Sound Power Levels in dB(A).

Table 7.7: Maximum Allowable Sound Power Levels

The above table gives guidance on the total allowable sound powers emitted from unmitigated plant items in different work areas to NSRs. The recommended control philosophies detailed in this section should be incorporated into the Contract Specification and developed in the Implementation Schedule in order to ensure the acceptable environmental performance of construction works will be complied.

The following illustrates a feasible approach to mitigate the predicted noise impacts during the construction phase. It is possible that the Contractor may develop a different package of environmental control measures to meet the required noise standards. Proposed alternative mitigation measures shall be demonstrated to meet or achieve better performances and in full compliance with the TM-EIA noise criteria and compatible with the construction programme.

7.3.6.1 Good Site Practices and Noise Management Techniques

Good site practice and noise management could considerably reduce the noise impact from construction site activities on nearby NSRs. The following measures should be followed during each phase of construction:

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

· machines and plant (such as trucks, cranes) that 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, where possible, be orientated so that the noise is directed away from nearby NSRs;

· silencers or mufflers on construction equipment should be properly fitted and maintained during the construction works;

· mobile plant should be sited as far away from NSRs as possible and practicable; and

· material stockpiles, mobile container site office and other structures should be effectively utilised, where practicable, to screen noise from on-site construction activities.

The noise benefits of these techniques can vary according to specific site conditions and operations. The environmental noise climate would certainly be improved through these control practices, although the improvement can only be quantified during implementation when specific site parameters are known.

7.3.6.2 Scheduling of Construction Works Outside School Examination Period

During school examination periods, the daytime construction noise criterion is 65 dB L_{Aeq,
30 min.} which is lower than the normal daytime school criterion (70 dB L_{Aeq,
30 min.}) by 5 dB(A). In critical areas, scheduling of construction works outside school examination period to less intrusive periods would definitely reduce the noise impacts on the NSRs and this also relieves the need to incorporate more stringent noise mitigation measures required to ensure compliance with the construction noise criteria.

7.3.6.3 Use of “Quiet” Equipment and Working Methods (M1)

The use of quiet plant is identified as a feasible solution to tackle adverse noise impacts associated with the construction works. It is generally known (supported by field measurement) that particular models of construction equipment are quieter than standard types given in the TM-CW. Whilst it is generally considered too restrictive to specify that the Contractor has to use specific models or items of plant, it is reasonable and practicable to set plant noise performance specifications for specific PME so that some flexibility in selection of plant is allowed. A pragmatic approach would be to request that the Contractor independently verifies the noise level of the plant proposed to be used and demonstrates through furnishing of these results, that the plant proposed to be used on the site meets the requirements.

The benefits achievable in this way can be considerable but will depend on the level of control given to the project engineer under the contract conditions and the ability and willingness to use these powers to control the level of environmental noise.

BS5228 ^[20] contains examples of SWLs for specific silenced PME. Examples known to be available are given in the table below. The total SWLs for each construction activity with the suggested “quieter” PMEs are detailed in Appendix 12.

Power Mechanical Equipment (PME)	Power Rating and/or size	BS5228 Table No.	Maximum SWL, dB(A)	CNP Reference in TM-CW	SWL in TM-CW
Concrete Lorry Mixer	5m³	C6	(100)	CNP044	109
Dump Truck	35 t	C9	(109)	CNP067	117
Excavator	45kW	C3	(106)	CNP081	112
Excavator (idling)	73kW	C3	96	CNP081	112
Lorry	35t	C3	(105)	CNP141	112
Mobile Crane	56kW	C7	(106)	CNP048	112
Mobile Crane (idling)	56kW	C7	99	CNP048	112
Poker vibrator	2kW	C6	(102)	CNP170	113
Vibratory Roller	9kW, 7000kg	C3	(102)	CNP186	113

Note: Bracket indicates SWLs being used in the calculations of mitigated noise levels.

Table 7.8: Listing of “Quiet” Equipment

It should be noted that while various types of silenced equipment could be found in Hong Kong, however, the EPD when processing a CNP application for evening or night time works may apply the noise levels specified in the TM-CW and TM-DA, unless the noise emission of a particular piece of equipment can be validated by certified site measurement or demonstration.

7.3.6.4 Purpose Built Temporary Noise Barriers (M2)

Purpose built temporary noise barriers 3 to 5m high located on the site boundaries between noisy construction activities and NSRs could generally reduce noise levels by up to 5-10 dB(A) through partial screening. It would be possible for the Contractor to provide these in the form of site hoardings to achieve this attenuation effect, provided that the barriers have no openings or gaps and have a superficial surface density of at least 7kg/m².

Given that the LRT worksite is linear in shape, a 3.5m high site hoarding of adequate surface mass could provide partial screening to NSRs at lower floors from construction works at grade. In general this would provide minimum 5 dB(A) attenuation. This has been assumed in the calculations for low level NSRs provided that the construction activities are at grade. Given the detailed information of site boundary wall and the geometry between the NSRs and the noise sources, the designs of the hoarding can be worked out to meet these requirements or achieve better screening effect.

7.3.6.5 Movable Noise Barriers (M2)

Movable noise barriers that can be located close to noisy plant and be moved iteratively with the plant along a worksite can be very effective at screening noise from NSRs. A typical design that has been used in Hong Kong is a 3.5 m high wooden framed barrier with a small cantilevered upper portion of superficial density no less than 7kg/m²on a skid footing with 25mm thick internal sound absorptive lining. Barriers of this type can be placed within a short distance from mobile plant such as an excavator, mobile crane etc.

Where these screening effects can be achieved at upper floors of NSRs, greater benefits would result at lower floors. To affect noise screening to NSR at high level e.g. 5 to 15-storey zones, cantilevered top cover would be required.

It is anticipated that suitably-designed noise barriers could achieve up to 10 dB(A) for static plant and 5dB(A) noise reduction for mobile plant. The noise screening benefit for the plant items considered in this assessment is as follows:

· stationary plant – 10 dB(A) screening for PME e.g. air compressor, water pump, concrete pump, generator, poker vibrator; and

· mobile plant – 5 dB(A) screening for PME e.g. excavator, lorry, roller, dump truck, concrete lorry mixer and mobile crane.

Any barriers designed by the Contractor should satisfy this noise performance in order to control the emission of noise from PME. The Contractor should pay particular attention to ensure barriers are close fitting around plant items thereby gaining greater noise reduction benefit.

7.3.6.6 Delocalization of Equipment in Critical Areas (M3)

For the same set of plant items, delocalization of equipment or avoiding all equipment operating at the same site location would reduce the noise impact from construction activities on nearby NSRs. Inspection of maximum noise exceedance calculations indicate the critical NSRs would be within 50m from the construction worksites. For two identical plant items at distance 200m apart, this would provide minimum 3 dB(A) or even more noise attenuation. In this assessment, 3 dB(A) noise reduction for concrete lorry mixer, excavator, dump truck, mobile crane, piling (reserve circulation drill) and poker is assumed to take into this factor, where required.

7.3.6.7 Local Reduction of Number of Plant Operating in Critical Areas where Practicable (M3)

In general the selection of the numbers of plant should be left to the Contractor so that in combination with the selection of quiet plant, any further reduction in the total plant noise levels, or the site specific maximum sound power levels can be achieved. This method could be more effective for activities associated with the use of dump trucks and excavators, where limiting operating plant items would be a practicable measure.

7.3.6.8 Limiting Operation Time of Construction Equipment On-Site (M4)

In locations where adverse noise impacts may arise, it would be appropriate to restrict the usage of particular noisy equipment operating within certain parts of the site that are very close to the NSRs. The percentage of time that the noisy equipment is allowed in operation may also need to be controlled so as to reduce the noise emissions during critical construction stages.

By restricting the percentage of operation of PME to 50% within 30-minute period, a noise reduction of 3 dB(A) could be achieved. In the assessment, this attenuation has been assumed for dump trucks in critical areas where M4 mitigation control is required. The dump trucks are only operating for 15 minutes in every consecutive 30-minute period.

7.3.7 Prediction of Mitigated Noise Levels

KCRC has confirmed that the above mitigation measures M1 to M4 as being practicable in completing the construction work on schedule. The noise mitigation measures described above regarding the use of quiet plant, noise barrier, equipment delocalization, local reduction of plant items and/or limiting operation time have been applied and the resultant noise levels with mitigation measures are shown in the table below.

Site Area	NSR	Description	Activities in Each Construction Phase^(2,3)
Site Area	NSR	Description	SCF	LSC	PIL	PCC	BF	CLC	SSC	TRL	OLC
Tin Shui Wai Phase 4 Extension	N1	Queen Elizabeth School Old Student's Association Primary School	70 (0) M2	68 (0) M2	69 (0) M2	67 (0) M2	69 (0) M2	69 (0) M2	69 (0) M3	69 (0) M2	69 (0) M2
	N2	Yiu Foo house	75 (0) M1	71 (0) M1	71 (0) M1	72 (0) M1	69 (0) M1	72 (0) M1	74 (0) M2	73 (0) M1	69 (0) M1
	N4	Yiu Man House	73 (0) M1	69 (0) M1	69 (0) M1	70 (0) M1	67 (0) M1	70 (0) M1	74 (0) M1	71 (0) M1	67 (0) M1
	N6	TWGH's Kwok Yat Wai College	68 (0) M4	68 (0) M3	68 (0) M3	68 (0) M3	67 (0) M3	68 (0) M3	68 (0) M3	70 (0) M3	69 (0) M2
	N7	Yiu Yat House	75 (0) M1	71 (0) M1	71 (0) M1	72 (0) M1	69 (0) M1	72 (0) M1	73 (0) M2	73 (0) M1	69 (0) M1
	N10	Yau Hong House	73 (0) M1	69 (0) M1	69 (0) M1	70 (0) M1	67 (0) M1	70 (0) M1	74 (0) M1	71 (0) M1	67 (0) M1
	N12	Yau Tai House	73 (0) M3	74 (0) M2	75 (0) M2	74 (0) M2	75 (0) M2	75 (0) M2	75 (0) M3	75 (0) M3	74 (0) M2
	N14	Yiu Fung House	73 (0) M3	73 (0) M2	73 (0) M2	74 (0) M2	71 (0) M2	74 (0) M2	75 (0) M2	75 (0) M2	71 (0) M2
	N15	The Church of Christ In China Hong Kong Council Fong Yun Wah School	70 (0) M3	69 (0) M3	67 (0) M3	67 (0) M3	70 (0) M2	67 (0) M3	66 (0) M3	70 (0) M3	70 (0) M2
	N16	3-storey residential block	75 (0) M2	72 (0) M1	72 (0) M1	73 (0) M1	70 (0) M1	73 (0) M1	74 (0) M2	74 (0) M1	70 (0) M1
	N17	3-storey residential block	75 (0) M1	71 (0) M1	71 (0) M1	72 (0) M1	69 (0) M1	72 (0) M1	73 (0) M2	73 (0) M1	69 (0) M1
	N18	3-storey residential block	75 (0) M2	72 (0) M1	72 (0) M1	73 (0) M1	70 (0) M1	73 (0) M1	74 (0) M2	74 (0) M1	70 (0) M1
	N21	Tse Yan House (Rental Block)	74 (0) M1	70 (0) M1	70 (0) M1	71 (0) M1	68 (0) M1	71 (0) M1	75 (0) M1	72 (0) M1	68 (0) M1
	N22	Tse Yan House (HOS)	75 (0) M1	71 (0) M1	71 (0) M1	72 (0) M1	69 (0) M1	72 (0) M1	75 (0) M2	73 (0) M1	69 (0) M1
	N23	Tsz Ping House	74 (0) M1	70 (0) M1	70 (0) M1	71 (0) M1	68 (0) M1	71 (0) M1	75 (0) M1	72 (0) M1	68 (0) M1
	N25	Buddhist To Chi Fat She Yeung Yat Lam Memorial School	69 (0) M1	65 (0) M1	65 (0) M1	66 (0) M1	63 (0) M1	66 (0) M1	70 (0) M1	67 (0) M1	63 (0) M1
	N27	Tin Shui Wai Catholic Primary School	70 (0) M3	70 (0) M1	70 (0) M1	70 (0) M3	68 (0) M1	70 (0) M2	70 (0) M2	70 (0) M4	68 (0) M1
	N29	Kenswood Court (Block 14)	75 (0) M2	72 (0) M1	72 (0) M1	73 (0) M1	70 (0) M1	73 (0) M1	74 (0) M2	74 (0) M1	70 (0) M1
	N31	Lynwood Court (Block 1)	75 (0) M2	72 (0) M1	72 (0) M1	73 (0) M1	70 (0) M1	73 (0) M1	74 (0) M2	74 (0) M1	70 (0) M1
	N33	Queen Elizabeth School Old Student's Association Secondary School	69 (0) M3	69 (0) M1	69 (0) M1	70 (0) M1	67 (0) M1	70 (0) M1	69 (0) M3	70 (0) M2	67 (0) M1

Note:

(1) MM: Mitigation Measures (see Section 7.3.5 for details of various mitigation measures M1, M2, M3 & M4).

(2) The application sequences of M1, M2, M3 and M4 means that the higher level mitigation measures have already integrated the lower level measures.

(3) SCF : Site Clearance & Formation; LSC: LRT Stop Construction; PIL: Piling; PCC: Pile Cap Construction; CLC: Column Construction; SSC: Superstructure Construction; TRL: Track Laying; OLC: Installation of Overhead Line Cable.

(4) Exceedances from daytime noise criteria (Table 7.1) are shown with brackets.

Table 7.9: Mitigated Predicted Noise Levels

With the use of quiet plant and noise barriers (M1+M2), construction noise levels at the majority of NSRs could be controlled within the daytime construction criteria. Noise level exceedances in the range of 1 to 12 dB(A) were predicted at Queen Elizabeth Primary School (N1), TWGH’s Kwok Yat Wai College (N6), Yau Tai House (N12), Yiu Fung House (N14), Fong Yun Wah School (N15) and Queen Elizabeth Secondary School (N33).

With further mitigation measures of equipment delocalization and local reduction of plant items (M1+M2+M3) at critical areas, noise exceedances have been reduced to 1dB(A) at TWGH’s Kwok Yat Wai College (N6). With further application of M4, construction noise levels at this school could be controlled within the daytime construction criteria.

7.3.7.1 Cumulative Impacts Within LRT Worksites

Adverse cumulative noise impacts from the construction worksites would not be expected provided that noisy construction activities within the worksites could be scheduled to more than 200m apart. This gives at least 10 dB(A) lower noise at a NSR compared to the noise generated from identical plant within a distance 50m apart.

There may be slight cumulative noise impact when construction works in the northern end of Tin Shui Wai Phase 4 Extension and construction works in the southern section of Tin Shui Wai Reserve Zone Extension under a separated LRT alteration proposal) are carried out simultaneously. To eliminate cumulative noise impacts, it is recommended to avoid simultaneous noisy activities within these two zones by scheduling of work areas at a minimum distance 200m apart. With careful management on the scheduling of construction works, the cumulative noise impacts in these areas could be eliminated.

7.3.8 Further Mitigation to be Considered by the Contractor

Analysis of prediction results indicates that excavators, and dump trucks are the major sources of construction noise impacts. The worst affected locations are between ground level to 5^th floor of the NSRs. The following mitigation measures shall be implemented by the Contractor in order to reduce construction noise impacts identified in this report.

· The availability of detailed plans or work areas and locations of plant (as opposed to gazetted work boundaries) will enable the Contractor to reduce the amount of uncertainty in the distance corrections applied to source noise levels used in this assessment. As a guide, a doubling of distance from NSRs will achieve a 6dB(A) reduction in noise levels.

· The layout of worksites should be critically reviewed and judiciously planned in order to make best use of existing features which may be able to provide screening of NSRs from plant noise eg site offices, site containers, etc.

· To determine specific SWL measurement of typical plant proposed to be used, particularly those activities that have been identified to be noisy or cause exceedances above daytime noise criteria. These ‘actual’ levels may then be able to be used in place of the values in the TM-CW.

· Use of smaller PME with lower SWL, e.g. smaller excavator, lorry to replace dump truck, where practicable.

· Practicality/cost-effectiveness of portable, full noise barriers for sections of works identified in this report.

· Sequential operation of a limited number of plant items in every 30-minute interval. For example, only excavator and vibratory roller are used in every 30-minute interval while only grader and dump truck are used in the next consecutive 30-minute period, where practicable.

· Use of limiting the operational period of other PME, where appropriate and practicable, as a last resort in order to meet the noise criteria. As an example, if PME could be operated for only 10 minutes out of any 30 minute period, a reduction of 5dB(A) could be achieved.

With the application of one or more of the above recommended methods of mitigation, there is considerable scope practicable to reduce noise impacts to within the allowable noise limits.

7.4 Conclusion

This assessment has predicted that the unmitigated construction noise impacts associated with the LRT alterations and extensions would be high at the nearby NSRs. Standard noise mitigation measures have been identified which could reduce the noise levels to within the noise criteria at most NSRs. Measures including the use of silenced PME, installation of movable barriers, delocalization of equipment, local restrictions on the number of PME in use and limiting the operation time of construction plant should be incorporated into the Contract Specifications and Implementation Schedules.

With the recommended mitigation measures, construction noise impacts at all NSRs could be controlled to within 75dB(A) criteria stipulated in the TM.

The preceding assessment has been conducted based on daytime noise criteria and it is understood that evening and night-time works would not be required normally. Where evening and night works are desired by the Contractors, they shall apply for a CNP from EPD.

8 Water Quality Assessment

8.1 Legislation and Standards

The regulatory requirements and standards to protect water quality are the Water Pollution Control Ordinance (WPCO) ^[6], its subsidiary technical memoranda, and various technical circulars issued by the Works Branch and EPD. Whilst the technical circulars are non-statutory, they are generally accepted as best guidelines in Hong Kong and have been adopted as relevant for this assessment.

8.1.1 Water Pollution Control Ordinance (WPCO)

Under the WPCO, Hong Kong waters are divided into 10 Water Control Zones (WCZs). Each WCZ has a designated set of statutory Water Quality Objectives (WQO). The standards to be met in each WCZ depend on the classification of the receiving waters (eg inland, inshore, marine or foul sewer). The standards are applied to effluents through licences issued by EPD under Sections 15, 16 and 20 of the WPCO. The relevant standards are set out in the Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters ^[17] (TM-Waters).

For this assessment study, the Tin Shui Wai Phase 4 Extension is located in Deep Bay WCZ.

8.1.2 Technical Memorandum on Standards for Effluents Discharged into Drainage and Sewerage Systems, Inland and Coastal Waters

This TM issued under Section 21 of the WPCO defines acceptable discharge limits to different types of receiving waters.

Effluents discharged into the inshore and marine waters of the Victoria Harbour WCZ are subject to standards stipulated in Tables 9a and 9b of the TM. The standards in Tables 10a and 10b of the TM apply to effluents discharged into the inshore and marine waters of the North Western and Western Buffer WCZs respectively. For the effluent discharged into the coastal water of Tolo and Port Shelter WCZ, the standards in Table 7 should be applied.

In this assessment study for the Tin Shui Wai Phase 4 Extension, the standards for the effluent discharged into the coastal waters of Deep Bay WCZ, which stipulated in Table 8 of TM should be referred, although reference should also be made to Section 8.1.3 below.

Discharges of effluents into the foul sewerage system need to comply with the standards listed in Tables 1 and 2 of the TM.

For cooling water discharges, in addition to the TM requirements (which only apply to discharges of up to 6,000m³per day), the EPD has required that discharges of between 6,000 and 1,000,000 m³ per day have a temperature of not more than 35⁰C and not more than 10⁰C above influent temperature, and contain not more than 0.2mg/1 of total residual chlorine.

8.1.3 The Deep Bay “Zero Discharge Policy”

In addition to Table 8 of the TM, this policy aims to limit the decline of water quality in Deep Bay and its catchments. It requires that major developments within Deep Bay catchments and all new developments in sensitive areas of the catchments do not increase existing pollution loads by connecting the sewage system of the developments to the public sewer system. If connection of the public sewer system is not feasible at the early development stage, (say first five years), the on-site treatment facilities should be installed as a temporary measure and the connection work of public sewer system must be completed within this period.

8.1.4 Construction Site Drainage Guidelines

The Practical Note for Professional Persons on Construction Site Drainage (PN1/94) issued by EPD provides basic environmental guidelines for the handling and disposal of construction site discharges to minimise impacts on water quality.

8.2 Assessment Methodology

8.2.1 Construction Phase

Current construction design was reviewed to assess the proximity of the proposed LRT construction activities to existing and committed WSRs. All WSRs have been identified according to the guidance provided in HKPSG, and verified by field surveys and area appraisals.

Construction type, sequence and duration were reviewed to identify activities likely to impact upon identified freshwater and marine water bodies and WSRs, water courses, streams, ponds and wetland freshwater catchment areas.

Following the identification of WSRs and potential water quality impacts, the scale, extent and severity of potential net (ie unmitigated) construction impacts were evaluated, taking into account all potential cumulative effects including those of adjacent projects, with reference to the WPCO criteria.

In the event that net water quality impacts exceed the appropriate WPCO criteria, practical water pollution control measures/mitigation proposals will be identified to ensure compliance with reference to the WPCO criteria for the beneficial uses of the marine water bodies and fresh water courses. Water quality monitoring and audit requirements will be subsequently developed to ensure the efficacy of the construction stage water pollution control and mitigation measures (Section 12).

8.2.2 Operational Phase

Present operational LRT designs were reviewed to assess the proximity of the rail alignment or any associated operational facilities to existing and future committed WSRs in accordance with the HKPSG.

All operational infrastructure proposals and activities were reviewed to identify activities likely to impact upon identified adjacent water bodies, water courses, streams, ponds, wetland freshwater catchment areas and marine WSRs.

Following the review of the LRT operation, the potential adverse effects, scale, extent and severity of potential net (i.e. unmitigated) impacts were assessed and evaluated, with reference to the WPCO criteria.

In the event that net impacts exceed the appropriate criteria, practical water pollution control measures and mitigation proposals will be identified for inclusion in the design to ensure residual impact compliance with reference to the WPCO criteria for the beneficial use of the marine water bodies and fresh water courses.

8.3 Assessment Results

The potential water quality impacts, which include the impacts on river and marine water quality and drainage, caused by the construction and operation of the Tin Shui Wai Phase 4 Extension.

The generation of construction and operational wastewater are key issues as it may cause adverse water quality impacts on WSRs if not properly controlled. The mitigation measures have been recommended to ensure that discharge levels meet the TM-Waters and EPD’s ‘zero discharge’ policy for the Deep Bay catchment.

8.3.1 Construction Phase

8.3.1.1 Water Sensitive Receivers (WSRs)

Potential WSRs likely to be affected by the construction works of proposed Tin Shui Wai Phase 4 Extension include:

a) Surface waters, including Tin Shui Wai Nullah; and

b) Fish/duck ponds near the southern section of Tin Shui Wai Phase 4 Extension.

8.3.1.2 Baseline Conditions

8.3.1.2.1 Tin Shui Wai Nullah

Tin Shui Wai Nullah is a concrete channel which drains the Tin Shui Wai area and discharges into inner Deep Bay. According to EPD’s River Water Quality in HK 1997, there was a marked improvement of the water quality of the nullah. The upstream monitoring station TSR2 was upgraded from “fair” to “good” and the downstream monitoring station TSR1 from “bad” to “fair”, with a substantial decrease in Ammonical-Nitrogen and E.coli (see Table 8.1).

The water quality of Tin Shui Wai nullah is monitored monthly by EPD’s river water monitoring programme. The EPD monitoring data of two monitoring stations TSR1 and TSR2 are summarised and given in Table 8.1. The monitoring locations are shown in Figure 8.1.

Even though the water quality of Tin Shui Wai Nullah was improved in 1997, the overall quality is still unsatisfactory, as reflected by occasional non-compliance with WQOs for BOD₅, COD and SS.

Parameter	TSR1	TSR2	WQOs for inland waters of Deep Bay WCZ
DO(mg/L)	7.6 (5.9 – 17.3)	10.5 (7.8 – 15.5)	4mg/L
BOD₅(mg/L)	14 (3-76)	3 (1-7)	3mg/L
COD(mg/L)	19 (11-130)	14 (4-41)	15mg/L
Oil and Grease (mg/L)	0.8 (0.5 – 7.6)	0.5 (0.5 – 1.2)	n.a.
SS (mg/L)	30 (7 – 140)	15 (5 – 93)	Annual Median 20mg/L
Ammonical N (mg/L)	2.50 (0.36 – 11.00)	0.46 (0.12 – 10.00)	n.a.
Total KjeldahI N (mg/L)	4.20 (0.78 – 20.00)	1.20 (0.23 – 14.00)	n.a.
Total P (mg/L)	0.88 (0.19 – 3.90)	0.17 (0.05 – 1.70)	n.a.
pH value	8.2 (7.9 – 9.6)	8.2 (7.6 – 9.5)	6.5 – 8.5
Flow (L/s)	NM	28 (3 – 570)	n.a.

Table 8.1 : Summary Statistics of 1997 Water Quality of Tin Shui Wai Nullah (TSR)

Notes:

1. Data presented are annual arithmetic means, except where specified otherwise.

2. Data enclosed in brackets are ranges.

3. NM indicates no measurement taken.

4. n.a. = not available

Source: EPD (January 1997 – December 1997)

8.3.1.3 Potential Source of Impact

Potential sources of impacts to water quality from the construction of the elevated grade separations and extension alignments are shown below:

· Construction Runoff ; and

· Sewage effluents generated from the construction workforce.

8.3.1.4 Prediction and Evaluation of Impact

8.3.1.4.1 Construction Runoff

Construction runoff from site areas may contain high loading of suspended solids (SS) and contaminants. Potential water pollution sources from construction site run off include:

a) Runoff and erosion from site surfaces, drainage channels, earth working areas and stockpiles;

b) Wash water from dust suppression sprays and wheel washing facilities; and

c) Fuel, oil, solvents and lubricants from maintenance of construction machinery and equipment.

Construction runoff may cause physical, biological and chemical effects. The physical effects could cause the increasing of SS from the site, which could cause blockage of drainage channels. Local flooding may also happen in a heavy rainfall situation. The chemical and biological effects caused by the construction runoff are highly dependent upon the chemical and nutrient content of the runoff. Runoff containing significant amounts of concrete and cement-derived material may cause primary chemical effects such as increasing of turbidity and discoloration, elevation in pH, and accretion of pH solids. A number of secondary effects may also result in toxic effects to water biota due to elevated pH values, and reduced decay rates of faecal micro-organisms and photosynthesis rate due to the decreased light penetration.

Once the construction activities commence, there will be an increase of SS levels and turbidity of nearby water bodies such as the fish/duck ponds near the southern section of Tin Shui Wai Phase 4 Extension. The downstream water quality of Tin Shui Wan Nulllah may also be affected by the construction works.

The water quality impacts from these construction activities are likely to be minimal provided that site boundaries are well maintained and good construction practices are applied to ensure that litter, fuel, oil, solvents and lubricants are properly managed, stored, handled and disposed.

8.3.1.4.2 Sewage Effluents

Sewage effluents will arise from the sanitary facilities provided for the on-site construction workforce. The characteristics of sewage would include high levels of 5-day Biochemical Oxygen Demand (BOD₅), Ammonia and E. coli counts.

Portable chemical toilets and proper disposal of sewage will be implemented at site offices to ensure that discharge standards are met. The same practice could be applied for the sewage generated by the construction workers dispersed along the extension alignments. No major water quality impact is expected.

8.3.2 Operational Phase

8.3.2.1 Baseline Conditions

The selected WSRs for the construction phase are also applicable to the operational phase.

Owing to the enforcement of Livestock Waste Control Scheme and the WPCO, it is expected that the surface water quality will be improved gradually. Therefore, the pollution loading from the nearby environment should be reduced gradually.

8.3.2.2 Potential Sources of Impacts

The runoff from rail track is considered as a potential source of impact to water quality from the operation of the extension alignment.

Air conditioning systems are not included in the design of LRT stops. Therefore, cooling water discharge is not considered as a potential source of impact.

Sewage discharge is not considered as a potential source of impact, as no commercial activities are allowed and there are no toilet/restroom facilities provided in the LRT stops. For the LRT terminus, however, toilets will be provided.

8.3.2.3 Predication and Evaluation of Impacts

The rail track runoff may be contaminated with SS (including metal chippings from track grindings and corrosion of rolling stock and other equipment). Grinding of rail will take place on a regular basis. Oil and grease arising from the light rail trains may also contaminate the rail track runoff. The requirements in the TM standards will be achieved if appropriate mitigation measures are adopted and implemented in order to minimise the potential contamination sources.

The sewage discharge from the toilets in the terminus will be discharged to the nearby public sewers. No adverse impacts are anticipated.

8.4 Recommendations

8.4.1 Construction Phase

Appropriate mitigation measures should be implemented to control construction runoff to prevent SS loading entering the water bodies and impacting on downstream WSRs. The surface runoff, soil erosion and sewage effluents should be minimised by proper site management practices.

The guidelines stipulated in the ProPECC PN 1/94 ^[18] should be followed in order to control the construction site runoff. Good housekeeping and best management practices should be implemented to ensure the runoff from construction site area and any stored excavated material complies with the WPCO and there are no unacceptable impacts on the WSRs caused by the construction activities. All discharge for the construction site areas should be controlled to comply with the TM-Waters. The “zero discharge” policy should also be complied for the construction of alignment due to the site areas falling within the Deep Bay WCZ.

8.4.1.1 Construction Runoff

Exposed soil areas should be minimised to reduce the contamination of runoff and erosion. The following mitigation measures should be adopted to control the runoff-related impacts:

a) The use of sediment/silt traps; and

b) The adequate maintenance of drainage systems to prevent flooding and overflowing.

The dikes or embankments for flood protection should be implemented around the boundaries of earthwork areas. Temporary ditches should be provided to facilitate the runoff discharge into an appropriate watercourse, through a site/sediment trap. The sediment/silt traps should be incorporated in the permanent drainage channels to enhance deposition rates.

Both temporary and permanent drainage pipes and culverts provided for runoff discharge should be adequately designed for the controlled release of storm flows. All sediment/silt traps should be cleaned and maintained regularly. The temporarily diverted drainage should be reinstated to its original condition when the construction works have finished or the temporary diversion is no longer required.

Wheel washing facilities should be implemented and regularly cleaned and maintained. Sediment, sand and silt in the wash water from the wheel washing facilities should be settled out and removed before discharging in storm drains. A section of the road between the wheel washing bay and the public road should be paved with backfill to prevent wash water or other site runoff entering the public road drain.

Oil interceptors should be provided in the drainage system downstream of any oil/fuel pollution sources. The oil interceptors should be emptied and cleaned regularly to prevent the release of oil and grease into the storm water drainage system after accidental spillage. A bypass should be provided for the oil interceptors to prevent flushing during of heavy rain.

All fuel/oil tanks and chemical storage tanks/areas should be provided with locks and be sited on sealed areas, within bunds of a capacity equal to 110% of the storage capacity of the largest tank, to prevent spilled fuel oils from reaching the receiving water bodies.

By adopting the above mitigation measures with Best Management Practices (BMPs), it is anticipated that the impacts of construction site runoff from the construction site will be reduced to an acceptable levels before discharges.

8.4.1.2 Sewage Effluent

Portable chemical toilets and sewage holding tanks are recommended to handle the construction sewage generated by workers from both the construction areas and dispersed along the alignment. A licensed Contractor should provide appropriate and adequate portable toilets and is responsible for appropriate disposal and maintenance.

8.4.1.3 Residual Impacts

Although the runoff from construction areas is expected, the water quality impacts will generally be temporary and localised. Therefore, no residual water quality impacts are expected from the construction phase of the extension alignment, provided that all of the recommended mitigation measures including appropriate drainage and silty runoff collection facilities are adopted.

It is considered that control of discharges from construction activities and proper site management procedures, as mentioned above, no residual water quality impacts is expected.

8.4.2 Operation Phase

8.4.2.1 Runoff from Rail Track

The impacts from track runoff could be minimised by the adoption of the following mitigation measures:

a) Provide a surface water drainage system in order to collect the track runoff. Where oil and lubricating fluids could be spilt, the track drainage channels discharge should pass through oil/grit interceptors/chambers, or sub-soil drainage system, to remove oil, grease and sediment before being pumped to the public stormwater drainage system;

b) The silt traps and oil interceptors should be cleaned and maintained regularly. The efficiency and performance of these facilities are highly dependent on regular cleaning and maintenance; and

c) Oily contents of the oil interceptors should be transferred to an appropriate disposal facility, or to be collected for reuse, if possible.

8.4.2.2 Residual Impacts

No residual operational water quality impacts are expected if appropriate drainage and effluent collection systems are adopted and incorporated.

8.5 Conclusion

The potential water quality impacts arising from the construction and operational phase of the Tin Shui Wai Phase 4 Extension have been assessed. Assessment results indicate that no residual water quality impacts should be generated from the construction and operation of the new LRT extension provided that the recommended mitigation measures are implemented.

AAB	Antiquities Advisory Board
AMO	Antiquities and Monuments Office
ANL	Acceptable Noise Levels
APCO	Air Pollution Control Ordinance
AQO	Air Quality Objectives
ASR	Area Sensitivity Ratings
BNL	Basic Noise Levels
BOD₅	5-day Biochemical Oxygen Demand
CNP	Construction Noise Permit
COD	Chemical Oxygen Demand
CRN	Calculation of Rail Noise
CRTN	Calculation of Road Traffic Noise
dB	Decibels
DDC	Detailed Design Consultant
DO	Dissolved Oxygen
DPA	Development Permission Area
EIA	Environmental Impact Assessment
EIAO	Environmental Impact Assessment Ordinance
EM&A	Environmental Monitoring and Auditing
EPD	Environmental Protection Department
FMC	Fill Management Committee
HKAQO	Hong Kong Air Quality Objectives
HKHA	Hong Kong Housing Authority
HKPSG	Hong Kong Planning Standards and Guidelines
Hz	Hertz
KCR/KCRC	Kowloon-Canton Railway Corporation
LR/LRT	Light Rail
NCO	Noise Control Ordinance
NSR	Noise Sensitive Receiver
OZP	Outline Zoning Plan
PCW	Prescribed Construction Work
PME	Powered Mechanical Equipment
ppm	Parts per Million
ProPECC	Professional Persons Environmental Consultative Committee
PS	Particular Specification
PTI	Public Transport Interchange
RSP	Respirable Suspended Particulates
SEL	Sound Exposure Level
SPME	Specified Powered Mechanical Equipment
SS	Suspended Solids
SSC	Suspended Sediment Concentration
SWL	Sound Power Level
TIS	Tin Shui Wai
TM	Technical Memorandum
TOC	Total Organic Carbon
TSP	Total Suspended Particulates
VSR	Visually Sensitive Receivers
WBTC	Works Branch Technical Circular
WCO	Water Control Objectives
WCZ	Water Control Zone
WDO	Water Disposal Ordinance
WPCO	Water Pollution Control Ordinance
WQO	Water Quality Objectives
WR	West Rail
WSR	Water Sensitive Receivers

	Concentration in micrograms per cubic metre (i)
Pollutant	1 Hour (ii)	8 Hour (iii)	24 Hours (iii)	3 Months (iv)	1 Year (iv)
Sulphur Dioxide	800		350		80
Total Suspended Particulates	500		260		80
Respirable Suspended Particulates (v)			180		55
Carbon Monoxide	30,000	10,000
Nitrogen Dioxide	300		150		80
Photochemical Oxidants (as ozone) (vi)	240
Lead				1.5

1 INTRODUCTION

2 Project Description

3 study Objectives and Scope

4 AVAILABLE TECHNICAL Information

5 Air Quality Assessment

6 Operational Noise Assessment

7 Construction Noise Assessment

8 Water Quality Assessment

8.3.1.2.1 Tin Shui Wai Nullah

8.3.1.4.1 Construction Runoff

8.3.1.4.2 Sewage Effluents

8.5 Conclusion

9 Waste Management Implications