4 NOISE IMPACT

Sha Tin Cavern Sewage Treatment Works EIA Report

AECOM 4-1 August 2016

4 NOISE IMPACT

4.1 Introduction

4.1.1.1 This section presents an assessment of the potential noise impacts associated with the construction and operation of the Project. The noise impact assessment is conducted in accordance with the requirements of Annex 5 and Annex 13 of the EIAO-TM as well as the requirements set out under Clause 3.4.2 of the EIA Study Brief.

4.2 Environmental Legislation, Standards and Criteria

4.2.1 General

4.2.1.1 Noise impacts are assessed in accordance with the criteria and methodology given in the Technical Memoranda made under the NCO, and the EIAO-TM.

4.2.1.2 The NCO provides the statutory framework for noise control. This defines statutory limits applicable to equipment used during the construction and operation phases of the proposed works in the study area. The NCO invokes four Technical Memoranda, which define the technical means for noise assessment:

Technical Memorandum on Noise from Places other than Domestic Premises, Public Places or Construction Sites (IND-TM);

Technical Memorandum on Noise from Construction Work in Designated Areas (DA-TM);

Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM); and

Technical Memorandum on Noise from Percussive Piling (PP-TM).

4.2.1.3 The NCO and the accompanying Technical Memoranda provide a mechanism for assessing noise levels and provide the statutory power to control noise.

4.2.1.4 With regard to the assessments of the construction noise impact during restricted hours and operational fixed plant noise impact, the NCO designates acceptable noise levels for Noise Sensitive Receivers (NSRs) on the basis of an Area Sensitivity Rating (ASR), based on the characteristics of the area within which they are located such as rural, village, low-density residential, or urban (see Table 4.1). Within these areas, the presence of "influencing factors" (IFs) (such as the presence of industrial activities or major roads) can further affect the ASR and hence the acceptable noise levels.

Table 4.1 Area Sensitivity Ratings (ASRs)

Type of Area Containing NSR

Degree to which NSR is affected by Influencing Factor (IF)

Not Affected Indirectly Affected

Directly Affected

Rural Area A B B

Urban Area B C C

Low density residential area consisting of low-rise or isolated high-rise developments

A B C

Area other than those above B B C



4.2.2 Construction Noise – General Construction

4.2.2.1 The NCO provides the statutory framework for noise control of construction works, other than percussive piling, using PME between the hours of 1900 and 0700 hours or at any time on Sundays and general holiday (i.e. restricted hours). Noise control on construction activities taking place at other times is subject to the Criteria for Evaluating Noise Impact stated in Table 1B of Annex 5 in the EIAO-TM. The noise limit is Leq(30 minutes) 75 dB(A) at the façades of dwellings and Leq(30 minutes) 70 dB(A) at the façade of schools (Leq(30 minutes) 65 dB(A) during examinations).

4.2.2.2 Between 1900 and 0700 hours and all day on Sundays and public holidays, activities involving the use of PME for the purpose of carrying out construction works is prohibited unless a Construction Noise Permit (CNP) has been obtained. A CNP may be granted provided that the Acceptable Noise Level (ANL) for the NSRs can be complied with. ANLs are assigned depending upon the ASR. The corresponding basic noise levels (BNLs) for evening and night time periods are given in Table 4.2.

Table 4.2 Basic Noise Levels (BNLs)

Time Period Basic Noise Level (BNLs), dB(A)

ASR A ASR B ASR C

Evening (1900 to 2300 hours) (1) 60 65 70

Night (2300 to 0700 hours) 45 50 55

Note: (1) Includes Sundays and Public Holidays during daytime and evening

4.2.2.3 The Noise Control Authority will consider a well-justified CNP application, for construction works within restricted hours as guided by the relevant Technical Memoranda issued under the NCO. 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 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.

4.2.2.4 Under the DA-TM, the use of five types of Specified Powered Mechanical Equipment (SPME) and three types of Prescribed Construction Work (PCW) within a designated area during restricted hours would require a valid CNP. The SPME includes hand-held breaker, bulldozer, concrete lorry mixer, dump truck and hand-held vibratory poker. The PCW are:

Erecting or dismantling of formwork or scaffolding;

Loading, unloading or handling of rubble, wooden boards, steel bars, wood or scaffolding material; and

Hammering.

4.2.2.5 In general, it should not be presumed that a CNP would be granted for carrying out PCW within a designated area during restricted hours. The CNP may be granted for the execution of construction works during restricted hours involving the use of PME and/ or SPME if the relevant ANLs and criteria stipulated in the GW-TM and DA-TM can be met.

4.2.2.6 Percussive piling is prohibited between 1900 and 0700 hours on any weekday not being a general holiday and at any time on Sunday or general holiday. A CNP is required for the carrying out of percussive piling between 0700 and 1900 hours on any day not being a general holiday. PP-TM sets out the requirements for working and determination of the permitted hours of operations. Referring to the construction method for the Project, percussive piling is not required.



4.2.3 Construction Noise – Ground-borne Noise

4.2.3.1 Construction ground-borne noise is under the control of the NCO, the EIAO, and their subsidiary Technical Memorandum. With reference to the IND-TM under the NCO, the criteria for noise transmitted primarily through the structural elements of the building or buildings should be 10dB(A) less than the relevant ANL. These criteria apply to all residential buildings, schools, clinics, hospitals, temples and churches.

4.2.3.2 The construction ground-borne noise criteria in daytime (0700-1900 hours) (except General Holidays & Sunday) will therefore be 10dB(A) less than the Criteria for Evaluating Noise Impact stated in Table 1B of Annex 5 in the EIAO-TM:

Leq(30 minutes) 65 dB(A) at the façades of dwellings;

Leq(30 minutes) 60 dB(A) at the façade of schools (Leq(30 minutes) 55 dB(A) during examinations)

4.2.3.3 As descripted in Section 4.2.2.2, construction noise (including construction ground-borne noise) within restricted hours (i.e. between 1900 and 0700 on a normal working day or at any time on a general holiday and Sunday) is controlled by the GW-TM. A CNP is required for construction activities involving the use of PME carried out in restricted hours and the construction ground-borne noise at NSRs shall be limited to 10 dB(A) below the respective ANLs for the ASR category of “A”, “B” and “C” at the NSRs. A summary of these criteria is given in Table 4.3.

Table 4.3 Ground-borne Noise Criteria (ANL, Leq, 5min dB(A))

Time Period Basic Noise Level (BNLs), dB(A)

ASR A ASR B ASR C

Evening (1900 to 2300 hours) (1) 50 55 60

Night (2300 to 0700 hours) 35 40 45

Note: (1) Includes Sundays and Public Holidays during daytime and evening

4.2.4 Construction Noise – Blasting

4.2.4.1 There is no statutory procedure or criteria under the NCO and EIAO for assessing the blasting impacts and is therefore beyond the scope of the EIA. However, the administrative and procedural control of all blasting operations in Hong Kong is vested in the Mines Division of the CEDD. The Dangerous Goods (General) Regulations, Chapter 295B also stipulates that no person shall carry out blasting unless he possesses a valid mine blasting certificate to be issued by the Mines Division of CEDD. The Superintendent of Mines will review the application on a case-by-case basis before issuing the Mine Blasting Certificate. According to the Clause 2.1.2 of EIA Study Brief, alternative construction methods to replace basting have been considered to minimise the construction noise impact as far as possible. TBM method would be adopted for the laying of pipelines below Shing Mun River or in hard rock. For the construction of caverns, as discussed in Section 2.8.2, the drill-and-blast method would be the most effective solution in this Project. Furthermore, the drill-and-blast method for the caverns could shorten the construction period and therefore minimize the noise nuisance induced. Blasting should be carried out outside sensitive hours as far as practicable, and the blasting schedule should be submitted to the concerned authority for approval prior for its implementation.

4.2.5 Road Traffic Noise

4.2.5.1 For road traffic noise, Annex 5, Table 1A “A Summary of Noise Criteria” of the EIAO-TM defines the criteria L10(1 hour) for the road traffic noise at various NSRs:

70dB(A) at the façades of residential dwellings, hotels, offices;

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65dB(A) at the façades of schools, places of public worship, courts of law, places where unaided voice communication is required; and

55dB(A) at the façades of hospital or clinics.

4.2.6 Operational Phase Fixed Plant Noise

4.2.6.1 Fixed plant noise sources are controlled by the NCO and IND-TM. The ANLs for the NSRs are determined based on the ASR. The ANLs for different ASRs during different periods are summarised in Table 4.4 below.

Table 4.4 Acceptable Noise Level for Fixed Plant Noise

Time Period ANL, dB(A)

ASR A ASR B ASR C

Day (0700 to 1900 hours) 60 65 70

Evening (1900 to 2300 hours) 60 65 70

Night (2300 to 0700 hours) 50 55 60

4.2.6.2 The NSRs at the north of the relocated STSTW are high rise housing developments as well

as low rise development such as village houses and education institutions. This area is not urban area or rural area. The type of this area is considered as “Area other than those above”. Since traffic noise from busy Tate’s Cairn Highway which is an IF affect some NSRs in this area. The ASR of the NSRs in this area would be “B” or “C” depending on whether the IF directly or indirectly affects or does not affect the respective NSRs.

4.2.6.3 The other NSRs located at the west and south-west of the relocated STSTW are village houses and low rise Government, Institution or Community (GIC) developments. These NSRs are located next to the green belt area, therefore, the type of these NSRs is considered as “Rural Area”. However, the NSRs at the west of the site are directly affected by traffic noise from Tate’s Cairn Highway and the ASR for this area is considered as “B”. The ASR of the NSRs at the south-west of the site is considered as “A” in the assessment.

4.2.6.4 The relocated STSTW and associated facilities would be operated 24-hour a day, ANL for night time with lower acceptable noise levels is adopted as the noise criteria for fixed noise sources for residential NSRs. Whereas for school, the ANLs for daytime and evening period are adopted in view of the normal opening hours of school.

4.2.6.5 As stipulated in Annex 5 of the EIAO-TM, the noise standard for planning purposes for fixed noise source are (a) 5 dB(A) below the appropriate ANL, or (b) the prevailing background noise levels (for quiet areas with level 5 dB(A) below the ANL). In this regard, noise measurement was undertaken in the vicinity of the representative NSRs to study the prevailing noise level. The measured prevailing background noise results are presented in Appendix 4.01 and summarized in below Table 4.5. Should the prevailing background noise level be lower than the ANL by more than 5dB(A), the background noise level would be adopted as the assessment criteria.

Table 4.5 Background Noise Measurement Results

Measurement Location

Description

Measured Min Leq 30-min, dB(A) Measurement

Method Day / Evening [1]

Night [2]

M1 Chevalier Garden 44 42 Façade

M2 Wellborn Kindergarten 46 45 Façade

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Description

Measured Min Leq 30-min, dB(A) Measurement

Method Day / Evening [1]

Night [2]

M4 Ma On Shan Tsung Tsin Secondary School

61 53 Free-field [3]

M5 SKH Ma On Shan Holy Spirit Primary School

59 52 Free-field [3]

M6 Ah Kung Kok Fisherman’s Village

56 49 Façade

M7 The Neighbourhood Advice-Action Council Harmony Manor

49 44 Façade

Notes: [1] Daytime means 07:00 – 19:00 and Evening time means 19:00 – 23:00. [2] Night time means 23:00 – 07:00 of the next day. [3] Façade correction of +3 dB(A) has been added to the measurement results for free-field

measurement.

4.2.6.6 In any event, the ASR assumed in the EIA Report is for indicative assessment only. It

should be noted that the fixed noise sources are controlled under Section 13 of the NCO. At the time of investigation, the Noise Control Authority shall determine noise impact from concerned fixed noise sources on the basis of prevailing legislation and practices being in force and taking account of contemporary conditions/situations of adjoining land uses. Nothing in the EIA Report shall bind the Noise Control Authority in the context of law enforcement against all the fixed noise sources being assessed.

4.3 Description of Environment

4.3.1.1 The relocated STSTW is located at Nui Po Shan at the east of Shing Mun River. Surrounding area of the relocated STSTW is a mixture of residential uses, village type development and institutional uses. The existing noise climate of the study area is dominated by the railway noise from the existing Ma On Shan Line and traffic noise arising from Tate’s Cairn Highway, Ma On Shan Road and A Kung Kok Street. The study area for noise impact assessment for the works of the relocated STSTW is defined by a distance of 300m from the Project boundary as shown in Figure No. 60334056/EIA/4.01.

4.3.1.2 The existing STSTW is located on the coast at the mouth of the Shing Mun River where it enters Tolo Harbour. The site occurs within urban developed area, surrounded by residential buildings in the west and Sha Tin Racecourse in the south. The study area for noise impact assessment for the works of the decommissioning of the existing STSTW is defined by a distance of 300m from the site boundary of the existing STSTW.

4.4 Noise Sensitive Receivers

4.4.1.1 The study area for noise impact assessment is defined by a distance of 300m from the site boundary of the construction site and the cavern for the relocated STSTW. The representative NSRs for the construction and operation of the relocated STSTW are identified and given in Table 4.6 below. Their locations are shown in Figure No. 60334056/EIA/4.01. Photographs of all the identified existing NSRs are provided in Appendix 4.02.

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Table 4.6 Representative Noise Sensitive Receivers affected by Relocated STSTW to Cavern during Construction and Operation Phases

NSR ID Description Type of Use

Distance from the Boundary of the

Relocated STSTW (m)

Construction [C] or Operation

[O] Phase Assessment

NR-C01 Chevalier Garden Residential 70 C/O

NR-C02 Wellborn Kindergarten Education 160 C/O

NR-C03 Hay Nien Primary School

Education 110 C/O

NR-C04 Ma On Shan Tsung Tsin Secondary School

Education 90 C/O

NR-C05 Tai Shui Hang Village Residential 210 C/O

NR-C06 Kam Tai Court Residential 180 C/O

NR-C07 S.K.H. Ma On Shan Holy Spirit Primary School

Education 210 C/O

NR-C08 Ah Kung Kok Fishermen Village

Residential/ Retail

10 C/O

NR-C09 Hong Kong Mountaineering Union

Societal / Storage

220 C

NR-C10 The Neighbourhood Advice-Action Council Harmony Manor

Mental Health Hospital

100 C/O

NR-C11 Shing Mun Springs Rehabilitation Centre

Rehabilitation Centre

240 C

Note: Construction Assessment refers to assessment for noise impact due to construction of Cavern STSTW; Operation Assessment refers to assessment of fixed plant noise impact from operation of CSTW.

4.4.1.2 Table 4.7 presents the ANLs of the representative NSRs based on the fixed plant noise

criteria mentioned in above Section 4.2.6. Considering the ANLs and the background noise measurement results presented in Table 4.5, Table 4.8 presents the fixed plant noise criteria of the representative NSRs in this assessment.

Table 4.7 Acceptable Noise Levels of the Representative Noise Sensitive Receivers

NSR Influence Factor (IF)

AADT

Degree to which NSR is affected

by IF

Area Sensitive

Rating (ASR)

ANL, dB(A)

Day / Evening

Night

NR-C01 N/A N/A Not Affected A 60 50

NR-C02 N/A N/A Not Affected A 60 -

NR-C03 Ma On Shan Road 37,730 Indirectly

Affected B 65 -

Tate’s Cairn Highway 64,620


Affected B 65 -


NR-C05 Ma On Shan Road 37,730 Indirectly Affected

B 65 55

NR-C06 Ma On Shan Road 37,730 Directly

Affected C 70 60


NR-C07 Ma On Shan Road 37,730 Directly

Affected C 70 -




NSR Influence Factor (IF)

AADT

Degree to which NSR is affected

by IF

Area Sensitive

Rating (ASR)

ANL, dB(A)

Day / Evening

Night


Affected B 65 55


NR-C10 N/A N/A Not Affected A 60 50

Note: AADT refers to the annual average daily traffic referenced to The Annual Traffic Census (ATC) 2014 of the Transport Department.

Table 4.8 Fixed Plant Noise Criteria of Representative Noise Sensitive Receivers

NSR ANL - 5, dB(A) Background Noise


Measured Min Noise Level, dB(A)

Fixed Plant Noise Criteria,

dB(A) Day Night Day Night

NR-C01 55 45 M1 44 42 42

NR-C02 55 - M2 46 - 46

NR-C03 65 - M4 61 - 61

NR-C04 60 - M4 61 - 60

NR-C05 60 50 M4 61 53 50

NR-C06 65 55 M5 59 52 52

NR-C07 65 - M5 59 52 52

NR-C08 60 50 M6 56 49 49

NR-C10 55 45 M7 49 44 44

4.4.1.3 Under the assumption of worst-case scenario, six NSRs are identified for the assessment

of ground-borne noise impact due to the use of PME at close vicinity. These identified NSRs are presented in Table 4.9 and its locations are shown in Figure No. 60334056/EIA/4.03.

Table 4.9 Representative Noise Sensitive Receivers for Assessment of Ground-borne Noise Impacts Due to Construction Works

Ground-borne Noise

Sensitive Receiver (GBNSR)

Description Type of

Uses Construction Work in the

Closest Site

Shortest Horizontal Distance to the Closest Work

Areas (m)

GBNSR-1 Chevalier Garden Residential Main Portal 78

GBNSR-2 Ah Kung Kok Fishermen Village

Residential Main Portal 44

GBNSR-3

The Neighbourhood Advice-Action Council Harmony Manor

Mental Health

Hospital

Access Road for Ventilation Shaft and Project Explosives

Magazine at A Kung Kok Shan

29

GBNSR-4 Kam Tai Court Residential Emergency Outfall

Construction 24

GBNSR-5 Seaview Villa Residential Decommissioning and Demolition of Existing

STSTW 157

GBNSR-6

Ma On Shan Tsung Tsin Secondary School

Education Main Portal 95





4.4.1.4 The representative NSRs which are likely to be affected by demolition of existing STSTW are identified and given in Table 4.10 below. Their locations are shown in Figure No. 60334056/EIA/4.01. Photographs of these identified existing NSRs are provided in Appendix 4.02.

Table 4.10 Representative Noise Sensitive Receivers affected by Decommissioning/Demolition of the Existing STSTW

NSR ID Description Type of

Use Distance from the Boundary of the

Existing STSTW (m)

NR-D01 Seaview Villa Residential 150

NR-D02 Kam On Garden Residential 220

NR-D03 Sha Tin Lookout Residential 270

NR-D04 Evergreen Villa Residential 290

NR-D05 Racecourse Gardens Residential 280

NR-D06 Kam Tai Court Residential 270

NR-D07 S.K.H. Ma On Shan Holy Spirit Primary School

Education 280

4.4.1.5 Two temporary access haul roads between Ma On Shan Road and the cavern work site for

construction vehicles/trucks would be provided during construction phase. The two temporary access haul roads would be located within the construction works area. These temporary access haul roads would be demolished after construction phase. The locations of the temporary access haul roads are indicated in Figure No. 60334056/EIA/4.02. Relevant sections of Ma On Shan Road would have minor temporary modification for these merging points. A small portion of existing noise barrier at Ma On Shan Road would be temporary removed and re-provided along the temporary access haul road due to this modification. Once the construction work for the relocated STSTW is completed, these two temporary access haul roads would be demolished and the relevant section of Ma On Shan Road and associated noise barrier would be recovered as before. The nearest NSR, Ah Kung Kok Fishermen Village, which is located in the vicinity of the concerned noise barrier, is selected for traffic noise impact assessment to study and demonstrate adequate noise protection to the surrounding when the existing barrier at the concerned road section of Ma On Shan Road is temporarily replaced by a noise barrier on the temporary access road.

4.5 Identification of Pollutant Sources

4.5.1 Construction Phase of Relocated STSTW

4.5.1.1 Construction noise is expected from the use of PME during various construction activities, such as excavation, concreting, compaction works, material handling activities etc, at all land-based works areas including the existing and relocated STSTW, improvement measures at A Kung Kok Street, alternative access to and from the relocated STSTW and temporary explosives magazine site at A Kung Kok Shan. For the cavern construction at Nui Po Shan, since most of the construction works for relocated STSTW including water reclamation facilities would be carried out underground / inside the rock mass, noise would be limited to areas near the portal, other above ground structures such as the ventilation shaft, fan plant rooms and the workshop and chemical store and the potential PME activities at the temporary stockpiling area.

4.5.1.2 As mentioned in Section 2, only the construction period of proposed Sha Tin ISEPS would be overlapped with the period for construction of cavern STSTW. However, the work site of ISEPS is located more than 300m from cavern STSTW works site, cumulative noise impact is not expected.

4.5.1.3 Drill-and-blast method will be adopted for the cavern construction. Potential ground-borne noise impacts arising from breaking the rock head may affect the NSRs in the close vicinity of the works site. The PMEs which are potentially in generating of ground-borne noise would be drill rigs, hydraulic breakers and hand-held breakers. TBM method will be





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adopted for construction of an effluent pipeline connecting to THEES tunnel and it would also pose potential ground-borne noise impact to the NSRs in the vicinity of the work site.

4.5.1.4 Blasting construction method is not considered with respect to noise annoyance, as the duration of blasting is very short and infrequent. No assessment has been carried out regarding noise annoyance impacts within any of the identified sensitive receivers.

4.5.1.5 Based on the current construction programme, there is no construction work outside the cavern within the restricted hours, therefore, only construction noise impact assessments for both air-borne and ground-borne noise during day hours according to the EIAO-TM is conducted in the study.

4.5.1.6 During construction phase, two temporary access roads would be provided to divert the truck traffic from cavern work site to Ma On Shan Road directly. As mentioned in Section 4.4.1.5, a small portion of existing noise barrier (9.2mPD to 10mPD) at Ma On Shan Road at this merging location would be temporary removed and re-provided along the temporary access haul road. Traffic noise impact assessment is therefore conducted to study and demonstrate adequate noise protection to the surrounding when the existing barrier at the concerned road section of Ma On Shan Road is temporarily replaced by a noise barrier on the temporary access road. Once the construction work for the relocated STSTW is completed, the temporary access roads would be demolished and the relevant section of Ma On Shan Road and associated noise barrier would be recovered as before.

4.5.2 Operation Phase of Relocated STSTW

4.5.2.1 Potential fixed plants noise impact during operation of the relocated STSTW would be generated from the operation of the ventilation shaft, ventilation buildings, fan plant rooms, pumps, general exhaust fans and ventilation fan of deodourization units etc. Since most of these fixed plants will be fully enclosed inside concrete structures or by physical rock mass within the caverns, noise impact from these facilities is anticipated to be insignificant. The air-conditioning/ventilating system operated at the administration building include air handling units, chiller and cooling tower. The cooling tower would be located at the rooftop of the administration building. The chiller would be located inside the plant room (concrete structure) with provision of ventilation system. The noise impact from operation of the chiller would be negligible but the ventilation fan for the plant room would be potential noise source. Fixed plant noise due to the above ground ventilation shaft, cooling tower at the roof of administration building, ventilation fan for the chiller plant room at administration building and ventilation buildings would dominate the fixed plant noise impact to NSRs in the vicinity. The pumps of the water reclamation facilities would be the main potential noise sources during operation. However, these facilities are located inside cavern, the noise arising from the pumps is anticipated to be insignificant.

4.5.2.2 During operation phase of the Project, the vehicles from relocated STSTW would pass through A Kung Kok Street and then to Ma On Shan Road. The peak hour traffic flow of A Kung Kok Street in Year 2016 is 931 nos. vehicle. The maximum number of vehicles due to the operation of relocated STSTW is anticipated to be less than 20 nos. vehicles per hour. The increase noise level due to operation of the relocated STSTW at A Kung Kok Street would be insignificant. As comparing with the traffic flow in the roads within the study area such as Ma On Shan Road and Tate’s Cairn Highways (over 7000 vehicles in peak hour), the increase in traffic flow from operation of relocated STSTW on the road network is negligible, therefore no significant off-site road traffic impact would be expected.

4.5.3 Decommissioning and Demolition of the Existing STSTW and the Temporary Explosives Magazine

4.5.3.1 Construction noise is expected from the use of PME during various decommissioning and demolition activities, such as excavation, material handling activities, etc. at the existing STSTW and the temporary explosives magazine site at A Kung Kok Shan. Potential construction noise impact would affect the nearby NSRs.



4.5.4 Concurrent Projects

4.5.4.1 Construction noise impact due to the reconstruction and upgrading of the existing upstream sewage pumping stations, is expected to be minor due to the small scale works and the construction periods are expected to be short term.

4.5.4.2 To redirect the sewage from the existing STSTW to the relocated STSTW, an ISEPS will be constructed at the existing STSTW.

4.6 Assessment Methodology

4.6.1 Construction Phase and Decommissioning of the Existing STSTW

Construction Noise – Airborne Noise

4.6.1.1 The construction noise assessment methods for the construction of the proposed relocated STSTW and the decommissioning of the existing STSTW are presented below.

4.6.1.2 The assessment follows the procedures given in the GW-TM. For the assessment of noise from PME, the distance attenuation is determined by using the following formula:

Distance Attenuation in dB(A) = 20 log D + 8 [where D is distance in metres]

4.6.1.3 Sound Power Levels (SWL) of equipment are taken from Table 3 of the GW-TM. Where no SWL is given in the GW-TM, reference is made to British Standard 5228: Part 1: 2009 Code of practice for noise and vibration control on construction and open sites and previous similar studies. For each construction activity, PMEs are grouped according to their likely concurrent usage. The plant inventory and percentage on-time utilization of the PME for the assessment has been confirmed to be practical and suitable for the proposed works.

4.6.1.4 Noise impact is assessed on the basis of the following assumptions:

Noise impact at the nearest sensitive facades of the residential buildings to the source positions is assessed;

A +3 dB(A) façade correction is added to the predicted noise levels to account for the facade effect at each NSR; and

All PME items required for a particular construction activity is located at the notional source position, in accordance with the GW-TM.

4.6.1.5 In accordance with the GW-TM, the notional source position is a position mid-way between the approximate geographical centre of the construction site and its boundary nearest to the NSR. As the size of the construction site is large such that the notional source position would be greater than 50m from the point on the site boundary nearest to the NSR. The position shall be taken to be a point 50m from that point on the site boundary measured along the line between the approximate geographical centre of the site and the point on the site boundary nearest to the NSR.

4.6.1.6 There are two haul roads for the access of the cavern site to Ma On Shan Road. The impact from construction vehicles is calculated in accordance with the following formula as stipulated in BS5228: Part 1:2009.

Leq (30 mins) = LWA − 33 + 10logQ − 10logV − 10logd + A

where:

LWA is the SWL of the plant, in decibels (dB)

Q is the number of vehicles per hour



V is the average vehicle speed, in kilometres per hour (km/h)

d is the distance of receiving position from the centre of haul road, in metres (m)

A is the angle of view correction, A = 10log(angle of view in degrees /180)

Construction Noise – Ground-borne Noise

4.6.1.7 The projection methodology is recommended by the U.S. Department of Transportation and Federal Transit Administration1. This projection methodology has been used in the Ground-Borne Noise & Vibration Assessment for Shatin to Central Link (SCL) EIA 2 approved by EPD (EIA Register No. AEIAR-166/2012).

4.6.1.8 The main components of the proposed prediction model for ground-borne noise are:

Vibration source level from operation of PME;

Vibration propagation through the ground to the structure foundation;

Vibration reduction due to the soil/structure interface;

Vibration propagation through the building and into occupied areas; and

Conversion from floor and wall vibration to noise.

4.6.1.9 The vibration level Lv,rms at a distance R from the source is related to the vibration source level at a reference distance Ro. The conversion from vibration levels to ground-borne noise levels is determined by the following factors:

Cdist: Distance attenuation Cdamping: Soil damping loss across the geological media Cbuilding: Coupling loss into building foundation Cfloor: Coupling loss per floor Cnoise: Conversion factor from floor vibration levels to noise levels Cmulti: Noise level increase due to multiple sources Ccum: Cumulative effect due to neighbouring sites

The predicted ground-borne noise level Lp inside the noise sensitive rooms is given by the following equation.

Lp = Lv,rms + Cdist + Cdamping + Cbuilding + Cfloor + Cnoise + Cmulti + Ccum

4.6.1.10 The assessment is based on assumptions for worst case. Details of the assumptions are described in the following:-

Reference Vibration Sources

4.6.1.11 Reference is made to the assessment approach, source terms and transmission factors adopted in the approved EIA study for the SCL project. The reference vibration levels of the PMEs are summarized in Table 4.11.

1 Transit Noise and Vibration Impact Assessment. Report No. FTA-VA-90-1003-06 2 Mass Transit Railway Corporation Limited (MTRC), EIA Study for Shatin to Central Link – Hung Hom to

Admiralty Section. 2011. (EIA Register No. AEIAR-166/2012)



Table 4.11 Summary of Reference Vibration Level of PMEs

PME

Reference

Vibration

Level, mm/s

Remarks

Drilling rig 0.536 rms Vibration velocity level at reference distance of 5.5m

Hydraulic breaker 0.298 rms Vibration velocity level at reference distance of 5.5m

Hand-held breaker 0.279 rms Vibration velocity level at reference distance of 5.5m

TBM/ micro TMB* 2.5 PPV Vibration velocity level at reference distance of 5.5m

Note: * Reference vibration level of micro TMB is assumed to be the same as TMB for conservative purpose

Distance Attenuation

4.6.1.12 Ground-borne noise can attenuate by longer distance of vibration energy transmission pathway. For this assessment, the shortest plan distances between the GBNSRs and the closest work areas are identified for correction. For separate distance over 300m, ground-borne noise assessment is excluded.

Soil Damping

4.6.1.13 Internal losses of soil would cause the vibration amplitude to decay against the propagation distance and the decay relationship is based on the equation set out in the Transportation Noise Reference Book3.

V(R) = V(Ro) e-2f R/2c

The velocity amplitude V is dependent on the frequency f in Hz, the soil loss factor , the wave speed c in m/s, the distance R from the source to the NSR. The properties of soil materials are shown in Table 4.12.

Table 4.12 Wave Propagation Properties of Soil

Soil Type Longitudinal Wave Speed c, m/s

Loss Factor, Density, g/cm3

Soil 1500 0.5 1.7

Rock 3500 0.01 2.65

4.6.1.14 No damping attenuation is applied in this assessment as conservative approach.

Coupling Loss into Building Structures

4.6.1.15 The coupling loss into building structures represents the change in the incident ground-surface vibration due to the presence of the piled building foundation. In this assessment, the correction has adopted the value in the “Transit Noise and Vibration Impact Assessment” published by Federal Transit Administration which is given in Table 4.13.

Table 4.13 Loss factor for Coupling into Building Foundation

Building Foundation Type Correction

Wood Frame Houses -5 dB

1 – 2 Storey Masonry -7 dB

3 – 4 Storey Masonry -10 dB

Large Masonry on Piles -10 dB

Large Masonry on Spread Footings -13 dB

Foundation in Rock 0 dB

3 P. M. Nelson. Transportation Noise Reference Book. 1987.



Coupling Loss per Floor

4.6.1.16 The coupling loss per floor represents the floor-to-floor vibration transmission attenuation. For multi-storey buildings, a common value for the attenuation of vibration from floor-to-floor is approximately 1 dB attenuation in the upper floor regions and greater than 3 dB attenuation at lower floors. Coupling loss of 1 dB reduction per floor is assumed in this report for a conservative assessment to account for any possible amplification due to resonance effects.

Conversion from Floor Vibration to Noise Levels

4.6.1.17 Conversion from floor vibration levels to indoor reverberant noise levels is based on standard acoustic principles. The conversion factor is dependent on the surface area S of

the room in m2, the radiation efficiency , the volume of the room V in m3 and the room reverberation time RT in seconds. Conversion factors from floor vibration levels to indoor reverberant noise levels adopted in the assessment are 27 dB for residential units, which is in line with the previous approved EIA reports.

Noise Level Increase due to Multiple Sources

4.6.1.18 This represents the increase in noise level due to multiple noise sources. The factor adopted for this assessment is based on the number of plants used concurrently and the construction programme from the construction plant list. Appendix 4.03 presents the construction programme and Appendix 4.04 presents the construction plant inventory under the unmitigated scenario.

Cumulative Effect due to Neighbouring Sites

4.6.1.19 Any cumulative effect of construction ground-borne noise at GBNSRs due to neighbouring sites shall be included. However, for this site, there is no neighbouring site inducing ground-borne noise.

Conversion to A-weighted Noise

4.6.1.20 For assessment of ground-borne noise at GBNSRs, a 20 dB(A) reduction is adopted for conversion to A-weighted noise. This conversion factor is obtained from the “Transit Noise and Vibration Impact Assessment” and is also adopted in the previous approved EIA reports.

Traffic Noise due to Relocation of Noise Barrier during Construction Phase

4.6.1.21 As mentioned in Section 4.5.1.6, traffic noise impact assessment is conducted to determine the potential impact due to relocation of a small portion of 3m high noise barrier from existing Ma On Shan Road to the temporary access haul road. Traffic noise is predicted using the methodology provided in the UK Department of Transport Calculation of Road Traffic Noise (CRTN) 1988. Road traffic noise levels are presented in terms of noise levels exceeded for 10% of the one-hour period during the peak traffic flow, i.e. L10(1hour) dB(A). The projected Year 2022 peak hour traffic flows and vehicle compositions, which is the maximum traffic flow during the construction period and has been agreed with TD, is adopted in the assessment.

4.6.1.22 For the purpose of the traffic noise assessment in this study, the roads within 300m from the proposed project alignment are included in the assessment. The locations of the existing noise barrier and the re-provisioned noise barrier, and the assessment points are shown in Appendix 4.07.






4.6.1.23 The following two scenarios are studied:

Without Project Scenario - Existing road layout and configuration of the noise mitigation scheme on Ma On Shan Road/Tate’s Cairn Highways in Year 2022

With Project Scenario - Existing road layout and configuration of the noise mitigation scheme on Ma On Shan Road/ Tate’s Cairn Highway except that a small portion of noise barrier at Ma On Shan Road is relocated to the temporary access road in Year 2022

4.6.2 Operation Phase

Fixed Plant Noise

4.6.2.1 For determination of assessment criteria, 2-days noise measurement (one at weekday and one at Sunday/public holiday) were conducted at the representative NSRs to study the prevailing noise levels. 24-hours per day noise measurement was carried out at each representative NSR. The measurements were conducted in accordance with the calibration and measurement procedures stated in the IND-TM. The measurement results and the assessment criteria for the representative NSRs due to fixed noise impact from the Project, as adopted in this EIA Study are presented in Appendix 4.01.

4.6.2.2 The following standard acoustic formula is used for calculating the sound pressure levels (SPL) at the representative NSRs due to fixed plant noise impact.

SPL = Max SWL – DC + FC – BC Where:

SPL Sound Pressure Level, in dB(A) Max SWL Maximum Permissible SWL, in dB(A) DC Distance Attenuation, in dB(A) (i.e. 20logD + 8 [where D is the distance

in metres]) FC Façade Correction, in dB(A) (i.e. 3 dB(A)) BC Barrier Correction, in dB(A)

4.6.2.3 It is assumed that all the fixed plant within the same location would be operated

simultaneously for the worst-case scenario. Screening correction offered by buildings or other structures such as office and residential buildings is taken into account in calculating the predicted noise levels. According to the GW-TM, effective barriers can result in noise reduction of 5 to 10 dB(A) for the fixed plant depending on the line of sight of the representative NSRs. A positive 3 dB(A) is added to the predicted noise levels at the NSRs due to the façade effect.

4.6.2.4 A positive 3 dB(A) for corrections of tonality is considered in the assessment.

4.7 Prediction and Evaluation of Environmental Impacts

4.7.1 Construction Noise - Airborne Noise

4.7.1.1 For normal daytime working hours, exceedances of the construction noise criteria would be predicted at representative NSRs in the absence of mitigation measures based on the construction programme as shown in Appendix 4.03 and the construction plant inventory presented in Appendix 4.04. The locations of the construction works areas, the details of construction noise calculations and results are presented in Appendix 4.05. A summary of the unmitigated noise assessment results is shown in Table 4.14.







Table 4.14 Unmitigated Construction Noise Levels due to the Project at Representative NSRs During Normal Daytime Working Hours

NSR Description Criteria, dB(A) Max SPL, dB(A)

NR-C01 Chevalier Garden 75 79

NR-C02 Wellborn Kindergarten* 70 80

NR-C03 Hay Nien Primary School 70 (65) 81


70 (65) 82

NR-C05 Low rise residential buildings on Tai Shui Hang South Street

75 77

NR-C06 Kam Tai Court 75 79


70 (65) 79

NR-C08 Ah Kung Kok Fishermen Village 75 82

NR-C09 Hong Kong Mountaineering Union 75 73


75 89

NR-C11 Shing Mun Springs Rehabilitation Centre 75 81

NR-D01 Seaview Villa 75 78

NR-D02 Kam On Garden 75 73

NR-D03 Sha Tin Lookout 75 73

NR-D04 Evergreen Villa 75 76

NR-D05 Racecourse Gardens 75 71

NR-D06 Kam Tai Court 75 70


70 (65) 71

Note: Bolded values indicate exceedance to noise criteria. * According to the information provided by Wellborn Kindergarten, there is no

examination period. 4.7.1.2 The above results show that the exceedances would be predicted at most of the residential

and educational NSRs during normal teaching period and examination period. Noise mitigation measures would therefore be required to reduce noise levels to the stipulated noise standards.

4.7.2 Construction Noise - Ground-borne Noise

4.7.2.1 Ground-borne noise impact from PMEs to the nearby sensitive receivers is predicted following the methodology described in Section 4.6, and the prediction results are summarized in Table 4.15. Detailed calculations are provided in Appendix 4.06. Results show that all representative GBNSRs would comply with the criteria under EIAO-TM.

Table 4.15 Predicted Construction Ground-borne Noise Impact Associated with the PME Use at Open Works Areas

GBNSR Description

Max. Predicted Ground-borne Noise

Levels Leq(30mins), dB(A)

EIAO-TM Criterion for

daytime (0700-1900)

Criteria Achieved

GBNSR-1 Chevalier Garden 51 65 Yes

GBNSR-2 Village House in A Kung Kok

52 65 Yes




GBNSR Description

Max. Predicted Ground-borne Noise

Levels Leq(30mins), dB(A)

EIAO-TM Criterion for

daytime (0700-1900)

Criteria Achieved

GBNSR-3 The Neighbourhood Advice-Action Council Harmony Manor

53 65 Yes

GBNSR-4 Kam Tai Court 45 65 Yes

GBNSR-5 Seaview Villa 40 65 Yes

GBNSR-6 Ma On Shan Tsung Tsin Secondary School

45 55 Yes

4.7.3 Traffic Noise due to Relocation of the Existing Noise Barrier during Construction

Phase

4.7.3.1 The length of existing noise barrier on the concerned road section of Ma On Shan Road at the height of 9.2 mPD to 10mPD to be temporary removed would be 150m. The noise barrier with the length of 220m at 10mPD would be re-provided along the temporary access haul road. Traffic noise levels have been predicted at representative noise assessment points at Ah Kung Kok Fishermen Village (2-storey high village houses) for the scenarios of with existing barrier configuration and temporary barrier arrangement in Year 2022, which is the peak flow during construction period. Assessment results indicate that there is negligible difference in noise levels at the representative noise assessment points between two scenarios. The details of the assessment and Year 2022 peak hour traffic flows are presented in Appendix 4.07.

4.7.4 Operational Fixed Plant Noise

4.7.4.1 Referring to the preliminary engineering design, the maximum SWLs of the ventilation shaft, cooling tower, ventilation fan for chiller plant room and ventilation buildings at main portal and secondary portal are presented in Table 4.16 and considered in the fixed noise impact assessment. Table 4.17 presents the predicted fixed plant noise levels at representative NSRs. The detailed calculation is shown in Appendix 4.08.

Table 4.16 Maximum Sound Power Levels for Fixed Plant Noise Sources

Noise Source

Description Maximum SWL, dB(A)

VB-M Ventilation Building at Main Portal 90

VB-E Ventilation Building at Secondary Portal 90

ADB-C Ventilation Fan for Chiller Plant Room at Administration Building 85

ADB-CT Cooling Tower at roof of Administration Building 88

VS Ventilation Shaft 95

Table 4.17 Predicted Fixed Plant Noise Levels at Representative Noise Sensitive Receivers

NSR Description Criterion,

dB(A) Predicted Noise

Level, dB(A)


NR-C02 Wellborn Kindergarten 46 45

NR-C03 Hay Nien Primary School 61 43


60 43


50 41






NSR Description Criterion,

dB(A) Predicted Noise

Level, dB(A)


52 41



44 44

4.7.4.2 The assessment results show that no exceedance of the fixed plant noise criteria would be

expected at the nearest NSRs.

4.8 Mitigation of Adverse Environmental Impacts

4.8.1 Construction Noise - Airborne Noise

4.8.1.1 In order to reduce the excessive noise impact at the affected NSRs during normal daytime working hours, adoption of quiet PME is recommended. The contractor(s) may be able to obtain particular models of plant that are quieter than the PMEs given in GW-TM. It is considered too restrictive to specify that a contractor has to use specific items of plant for the construction operations. It is practical to specify the total SWL of all plant to be used on site so that the contractor(s) is allowed some flexibility to select plant to suit his needs.

4.8.1.2 The use of quiet plant associated with the construction works is prescribed in British Standard “Code of practice for noise and vibration control on construction and open sites, BS5228” which contains the SWLs for specific quiet PME. The SWLs of quiet PMEs adopted for the assessment are detailed in Appendix 4.09. The mitigated noise levels with the adoption of the quiet PMEs are summarized in Table 4.18 and the detailed mitigated noise assessment results are presented in Appendix 4.10.

Table 4.18 Mitigated Construction Noise Levels due to the Project at Representative NSRs During Normal Daytime Working Hours (Using Quiet PME)

NSR Description Criteria, dB(A) Max SPL,

dB(A)


NR-C02 Wellborn Kindergarten* 70 70

NR-C03 Hay Nien Primary School 70 (65) 72


70 (65) 74


75 68



70 (65) 73


NR-C09 Hong Kong Mountaineering Union 75 66


75 80

NR-C11 Shing Mun Springs Rehabilitation Centre 75 72

NR-D01 Seaview Villa 75 75

NR-D02 Kam On Garden 75 70

NR-D03 Sha Tin Lookout 75 70





NSR Description Criteria, dB(A) Max SPL,

dB(A)

NR-D04 Evergreen Villa 75 73

NR-D05 Racecourse Gardens 75 68

NR-D06 Kam Tai Court 75 67


70 (65) 68

Note: Bolded values indicate exceedance to noise criteria, italic values indicate exceedance to noise criterion during examination period only.

* According to the information provided by Wellborn Kindergarten, there is no examination period.

4.8.1.3 With the use of quiet PMEs, exceedance would still be predicted at educational NSR NR-

C03, NR-C04, NR-C07 and residential NSR NR-C10 during construction works for relocated STSTW. During demolition of existing STSTW, exceedance of noise criterion for examination period would be anticipated at educational NSR NR-D07.

4.8.1.4 To alleviate the construction noise impact on these affected educational NSRs, movable noise barrier for Air Compressor, Bar Bender and Cutter, Breaker, Chisel, Saw, Compactor, Concrete Mixers, Pump, Crane, Desander, Drilling Rig, Dump Truck, Excavator, Generator, Grab, Lorry, Paver, Poker and Roller are proposed. Movable temporary noise barriers that can be located close to noisy plant and be moved iteratively with the plant along a worksite can be very effective for screening noise from NSRs. A typical design which has been used locally is a wooden framed barrier with a small cantilevered upper portion of superficial density no less than 14kg/m2 on a skid footing with 25mm thick internal sound absorptive lining. This measure is particularly effective for low level zone of NSRs. A cantilevered top cover would be required to achieve screening benefits at upper floors of NSRs. It is anticipated that suitably designed barriers could achieve at least 5 – 10 dB(A) reduction. In addition, noise barrier/acoustic mat for the Drilling Jumbo is also proposed when it is operated outside the portal and within 20m inside the portal so as to have screening effecting with 10 dB(A) noise attenuation.

4.8.1.5 For residential NSR NR-C10, in view of site constraint, it is not possible to install the movable noise barrier. In order to further alleviate the construction noise impact on this NSR, it is proposed to limit the number of on-time operating PMEs within 120m of this NSR during construction of access road. With this measure in place, the predicted construction noise levels at this NSR would comply with the criterion of 75 dB(A).

4.8.1.6 Noise reduction from the use of mitigation measures including quiet plant and noise barrier/acoustic mat for construction plants and limitation of the number of on-time operating PMEs as described above have been applied in the assessment. Details of construction noise calculations and results for the “mitigated” scenario are presented in Appendix 4.10. The predicted mitigated cumulative noise levels at representative NSRs are summarised in the Table 4.19.

Table 4.19 Mitigated Construction Noise Levels due to the Project at Representative NSRs During Normal Daytime Working Hours (with further Mitigation Measures)

NSR Description Criteria, dB(A) Mitigation Measures

Max SPL, dB(A)

NR-C03 Hay Nien Primary School 70 (65)

Quiet PME + Movable Noise Barrier/Acoustic

Mat

63


70 (65)

64


70 (65)

66




NSR Description Criteria, dB(A) Mitigation Measures

Max SPL, dB(A)


75

Quiet PME + Limit of the

number of on-time operating PMEs within 120m of the NSR during

construction of access road

75


70 (65) Quiet PME +

Movable Noise Barrier

64

Note: Bolded values indicate exceedance to noise criteria, italic values indicate exceedance to noise criterion during examination period only.

4.8.1.7 With the installation of further mitigation measures, all representative NSRs would comply

with the EPD noise criteria except that educational NSR NR-C07 would exceed the criterion for examination period. At the time of the assessment, the school can only has the examination schedule in the Year 2015-2016, therefore, the prediction on any exceedance of criterion for examination period is based on this schedule. Referring to the examination schedule provided by this school, the examination period in each year is 3 days in January and 3 days in June respectively. The potential impact on the educational NSR NR-C07 is summarized as below:

Exceedance of 1 dB(A) :

3 days in January and 3 days in June 2021;

3 days in January and 3 days in June 2022; and

3 days in January 2023.

4.8.2 Construction Noise – Ground-borne Noise

4.8.2.1 Results show that all representative GBNSRs would comply with the criterion, mitigation measure is not required.


4.8.3.1 The predicted noise levels of the representative NSRs in the vicinity of the fixed plant sources such as ventilation shaft, cooling tower at the roof of administration building, ventilation fan for chiller plant room at administration building and ventilation buildings would comply with the noise criterion, no further mitigation measure is required.

4.9 Evaluation of Residual Impacts

4.9.1 Construction Noise

4.9.1.1 With the implementation of proposed mitigation measures in Section 4.8.1, exceedance of 1 dB(A) would still be predicted at educational NSR NR-C07 (S.K.H. Ma On Shan Holy Spirit Primary School) during examination period. Based on the observations from site visits, this school has already been noise insulated with air-conditioners. With the provision of air-conditioners, it is considered that the noise impact would be minimized by keeping the windows closed during examination period. Notwithstanding this, due to more stringent noise criterion of 65 dB(A), it is recommended that particularly noisy construction activities, should be scheduled to avoid examination periods of this NSR as far as practicable. The Contractor should liaise with the school representative(s) to obtain the examination



schedule so as to avoid noisy construction activities during school examination period. The residual impacts are evaluated in accordance with Section 4.4.3 of the EIAO-TM as shown in Table 4.20 below.

Table 4.20 Evaluation of Residual Noise Impacts during Construction Phase

Criteria Assessment

Health and health of biota or risk of life The extent of noise nuisance would be unlikely to induce public health concern.

Magnitude of the adverse environmental impacts

The predicted exceedance of construction noise for NSR NR-C07 is 1 dB(A) during examination period. All practicable measures have been proposed and exhausted to minimize the noise impact. In addition, it is noted that noise insulation works with air-conditionings have been installed at this school. With the provision of air-conditioners, it is considered that the noise impact would be minimized by keeping the windows closed during examination period.

Geographic extent of the adverse environmental impact

The geographic extent of the adverse impact from noise is anticipated to be limited to NSR NR-C07 during examination period.

Duration and frequency of the adverse environmental impacts

The predicted exceedance durations of construction noise for NSR NR-C07 during examination period are: Exceedance of 1 dB(A) :

3 days in January and 3 days in June 2021;

3 days in January and 3 days in June 2022; and

3 days in January 2023.

All practicable measures have been proposed and exhausted to minimize the noise impact.

Likely size of the community or the environmental that may be affected by the adverse impacts

NSR NR-C07 would be temporarily affected by residual construction noise during examination period.

Degree to which the adverse environmental impacts are reversible or irreversible

Not Applicable in noise section.

Ecological context

Not Applicable in noise section

Degree of disruption to sites of cultural heritage

Not Applicable in noise section

International and regional importance The impacts are localized and not of international and regional importance



Criteria Assessment

Likelihood and degree of uncertainty of adverse environmental impact

The impacts predicted are based upon worst case assumptions and as such, would not occur to the extent predicted on all occasions.

4.9.1.2 In addition to the mitigation measures mentioned in Section 4.8, the good site practices

listed below shall be adopted by all the contractors to further ameliorate the noise impacts. Although the noise mitigating effects are not easily quantifiable and the benefits may vary with the site conditions and operating conditions, good site practices are easy to implement and do not impact upon the works schedule.

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

Silencers or mufflers on construction equipment should be utilised and should be properly maintained during the construction program;

Mobile plant, if any, should be sited as far away from NSRs as possible;

Machines and plant (such as trucks) that may be in intermittent use should be shut down between works periods or should be throttled down to a minimum;

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

Material stockpiles and other structures should be effectively utilised, wherever practicable, in screening noise from on-site construction activities.


4.9.2.1 No residual fixed plant noise impact due to the operation of the Project is expected.

4.10 Environmental Monitoring and Audit

4.10.1.1 An EM&A programme is recommended to be established according to the predicted occurrence of noisy activities. The recommended mitigation measures should be implemented during construction stage. Details of the programme are provided in a stand-alone EM&A Manual.

4.10.1.2 No adverse impact is expected due to the operation of the fixed plants. Operational fixed plant noise monitoring is therefore considered not necessary. Prior to the operational phase of the Project, a commissioning test for the ventilation buildings, cooling tower and ventilation fan for chiller plant room at administration building, and the ventilation shaft should be conducted to ensure compliance with the relevant designed maximum SPLs.

4.11 Conclusion

4.11.1 Construction Noise

4.11.1.1 This assessment has presented the construction noise impacts of the Project during construction of relocated STSTW including water reclamation facilities, decommissioning and demolition of existing STSTW and the temporary explosives magazine. The predicted maximum unmitigated noise levels at representative NSRs would range from 70 to 89 dB(A). With the adoption of quiet PME, use of movable noise barrier/acoustic mat, and limitation



of the number of on-time operating PMEs within 120m of the Neighbourhood Advice-Action Council Harmony Manor during construction of access road, , the noise levels due to the Project itself at all representative residential NSRs would comply with the EIAO-TM criterion of 75 dB(A). All representative educational NSRs would also comply with the noise criteria except that exceedance of noise criterion by 1 dB(A) during examination period is still predicted at educational NSR NR-C07 due to construction activities at the main portal and at Area 73. As this NSR is located in close vicinity of these work areas, all practical mitigation measures have been exhausted. Since the affected period would be limited to examination periods and the affected educational NSR has been noise insulated with air conditioners, it is considered that the residual noise impact is in short term period and would be minimized by keeping the windows closed during the affected examination periods.

4.11.1.2 During the actual construction period, as much as practically possible should be done to reduce the construction noise, and on-going liaison with all concerned parties and site monitoring should also be conducted during the course of the construction period. A construction noise EM&A programme is recommended to check the compliance of the noise criteria during normal daytime working hours.

4.11.1.3 Ground-borne construction noise impacts pertinent to the use of hydraulic breaker, hand-held breaker, drill rig and TBM would comply with criteria of NCO. No adverse ground-borne construction noise impacts would be predicted and therefore no noise mitigation measure and noise monitoring are proposed.

4.11.1.4 Blasting noise due to construction of cavern is not considered with respect to noise annoyance, as the duration of blasting is very short and infrequent. Nevertheless, blasting should be carried out outside sensitive hours as far as practicable, and the blasting schedule should be submitted to the concerned authority for approval prior for its implementation. Blasting should be carried out by a person possesses a valid mine blasting certificate by Mines Division of CEDD.

4.11.1.5 For the temporary modification works at the merging point of Ma On Shan Road and temporary access haul road, the re-provision of 220m length noise barrier with 10mPD on temporary access haul road to replace the existing 150m length noise barrier with 9.2mPD to 10mPD on Ma On Sha Road would pose negligible difference in the overall traffic noise level at the sensitive facades in the vicinity. Once the construction work is completed, the noise barrier on the concerned road section of Ma On Shan Road would be re-installed according to the existing configuration.


4.11.2.1 The noise impact associated with the operation of the Project has been assessed. The predicted fixed plant noise levels at the representative NSRs would comply with the criteria based on the plant design information provided by the Engineer at the time of the assessment. If there is any change in engineering design information during detailed design stage or fitting-out stage, the fixed source noise design should be reviewed by the Engineer/Contractor to ensure that both the NCO and EIAO-TM criteria at the NSRs can be met in the future. Prior to the operational phase of the Project, a commissioning test for the ventilation buildings, the ventilation shaft, ventilation fan for chiller plant room at administration building and cooling tower at the administration building would be conducted to ensure compliance with the relevant allowable maximum sound power levels.

4 NOISE IMPACT

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