4.1.1.1 Potential construction phase air-borne noise impacts may be generated as a result of the use of powered mechanical equipment (PME) for various construction activities including site formation, cut and cover works, construction of jacking and receiving pits, and formation of intakes and outfalls, as detailed in Section 2 of this report. Further details of the construction activities, programme and equipment requirements are provided in Section 4.7 below. No operational noise impacts would be anticipated for this project and have, therefore, not been considered further.
4.2 Environmental Legislation, Standards and Guidelines
4.2.1 Noise Control Ordinance and Technical Memoranda
4.2.1.1
The
Noise Control Ordinance (NCO) and the EIAO provide the statutory framework for
noise control. Assessment procedures and
standards relevant to this project are set out in the Technical Memoranda (TM)
given below.
· The TM on Environmental Impact Assessment Process (EIAO-TM);
· The TM on Noise from Construction Work other than Percussive Piling (GW-TM); and
· The TM on Noise from Construction Work in Designated Areas (DA-TM).
4.2.1.2 No percussive piling is proposed for the project and as such the Technical Memorandum on Noise from Percussive Piling will not be relevant to the noise assessment and is not discussed further. Notwithstanding, percussive piling is prohibited at any time on Sundays and public holidays and during the weekday evening and night-time hours (1900-0700hrs, Monday through Saturday) and a Construction Noise Permit (CNP) would be required from the Environmental Protection Department (EPD) if such works were eventually needed.
4.2.2 Noise Standards for Non-restricted Hours
4.2.2.1 Daytime construction noise (excluding percussive piling) between the hours of 0700 and 1900 on weekdays, that is, non-restricted or normal working hours, is governed by the EIAO-TM. Annex 5 of the EIAO-TM sets out the construction noise assessment limits, which are Leq(30 min) 75dB(A) for domestic premises and hotels, and Leq(30 min) 70dB(A) for educational institutions including kindergartens (or 65dB(A) during examination periods), nurseries and all other places where unaided voice communication is required. The recommended noise standards are summarised in Table 4.1 below.
Table 4.1 Daytime
Construction Noise Limits
|
Uses |
Noise Standard, Leq, 30 min dB(A) |
|
Domestic premises, hotels
and hostels |
75 |
|
Educational institutions, kindergartens, nurseries and all others
where voice communication is required |
70 (65 during examination
period) |
Note: The above criteria apply to noise sensitive uses which rely on open window for ventilation and should be viewed as the maximum permissible noise levels assessed at 1m from the external façade.
4.2.3 Noise Standards for Restricted Hours
4.2.3.1 During restricted works periods between 1900 and 0700 hours from Monday to Saturday and at any time on Sundays or public holidays, activities involving the use of PME for the purpose of carrying out construction work is prohibited unless a Construction Noise Permit (CNP) has been obtained.
4.2.3.2 The GW-TM provides details of the procedures adopted by the EPD for assessing such applications. The granting of a CNP is subject to the conditions as stated in the CNP, which may be revoked at any time for failure to comply with the permit conditions. A CNP may be granted in cases where the noise can be contained within the Acceptable Noise Level (ANL) at the Noise Sensitive Receivers (NSRs). ANLs are assigned depending on the Area Sensitivity Ratings (ASRs) of the study area. The ANLs for construction works in a “Designated Area” (controlled by the DA-TM) are more stringent than those given in the TM-GW.
4.2.3.3 Under the DA-TM, the use of five types of Specified Powered Mechanical Equipment (SPME), namely hand-held breaker, bulldozer, concrete lorry mixer, dump truck and hand-held vibratory poker, and undertaking three types of Prescribed Construction Works (PCW) within a designated area during restricted hours would require a valid CNP. 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.
4.2.3.4 In general, it cannot be presumed that a CNP would be granted for carrying out PCW within a designated area during restricted hours but it may be granted if the relevant ANLs and criteria stipulated in the GW-TM and DA-TM can be met.
4.2.3.5 As defined in the latest Noise Control Designated Area Plan (Plan No. EPD/AN/NT-05), the eastern part of the project area is within the Designated Area. The corresponding basic noise levels (BNLs) for evening and night-time periods are given in Table 4.2 and the figures in brackets for designated areas would apply to this area.
Table 4.2 Construction
Noise Criteria for Activities other than Percussive Piling
|
Time
Period |
Basic Noise Levels (BNLs),
dB(A) |
||
|
ASR ‘A’ |
ASR ‘B’ |
ASR ‘C’ |
|
|
Evening (1900 to 2300 hrs)[a] |
60 (45) |
65 (50) |
70 (55) |
|
Night-time (2300 to 0700 hrs) |
45 (30) |
50 (35) |
55 (40) |
NOTE:
[a] Includes Sunday and Public Holidays during daytime and evening.
Figures in brackets are BNLs for Specified Powered Mechanical Equipment (SPME) construction work in designated areas.
4.2.3.6 As noise in restricted periods is covered by the NCO, it is not assessed further in this EIA Report under the EIAO and despite any reference made in this EIA Report to construction noise aspects during restricted periods, 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 TM issued under the Noise Control Ordinance. The Noise Control Authority will take into account contemporary conditions/situation of adjoining land uses and any previous complaints against construction activities at the site before making his decision in granting a CNP. Nothing in the 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 seen fit. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.
4.2.3.7 According to the construction programme detailed in Figure 2.8b, all the proposed construction works are, however, expected to be carried out during non-restricted hours. In case of any construction activities during restricted hours, it will be the Contractor’s responsibility to ensure compliance with the NCO and the relevant TMs. The Contractor will be required to submit a CNP application to the Noise Control Authority and abide by any conditions stated in the CNP, should one be issued.
4.3.1.1 NSRs have been identified in accordance with Annex 13 of the EIAO-TM which can included domestic premises, temporary housing accommodation, educational institutions, nurseries, hospitals, medical clinics, homes for the aged, convalescent homes, places of public worship, libraries, courts of law, performing arts centres, auditoria, amphitheatres, hostels and country parks. Noise sensitive receivers present within the 300m study area boundary have been identified.
4.3.1.2
The construction sites are located
to the northern side of the Po Lin Monastery, northwest of the Po Lin Monastery
near
Table 4.3 Representative
Noise Sensitive Receivers
|
NSR (1) |
Location |
Type |
No. of Storeys |
Minimum Source-Receiver
Slant Distance (m)* |
|
NSR1 |
Columbarium of |
Place of public worship |
1 |
18.7 |
|
NSR3 |
Village House No. 68 |
Residential |
2 |
40.8 |
|
NSR4 |
Village House No. 65 |
Residential |
2 |
30.8 |
|
NSR5 |
Village House No. 49A |
Residential |
1 |
6.5 |
|
NSR6(2) |
Village House No. 40 |
Residential |
2 |
24.5 |
|
NSR7 |
Luen Sin Tong |
Place of public worship |
2 |
35.5 |
|
NSR8 |
Village House No. 34 |
Residential |
2 |
26.3 |
|
NSR9 |
Village House |
Residential |
2 |
25.7 |
|
NSR11(3) |
|
Place of Public Worship |
1 |
35.9 |
Notes:
* Slant distance is the distance from the SR to the location of the PMEs in the nearest works area. Refer to Appendix C2 for the locations of the notional sources.
(1) The numbering of the NSRs is consistent with that of the
ASRs in Section 3 of this EIA
Report. SR2 and SR10 are shopping centre
and kitchen of the Po Lin Monastery, respectively and, therefore, do not
constitute an NSR for this assessment and as such, no NSR2 or NSR10 has been included in this
assessment.
(2) NSR6 is an abandoned village house but is the closest property to the proposed construction works among the cluster of village houses in this area. It also offers
shielding to 3 village houses behind it.
It has, therefore, been selected to represent the NSRs in this area as a worst case as it would be the worst affected location.
(3) NSR11
is the kitchen house of Po Lin Monastery and would normally not be considered
as an NSR. However, it is selected
to represent the closest occupied building of the Monastery that
would be the worst affected by the construction works.
4.3.1.3 The photos of the NSRs are also provided in Appendix C1.
4.4.1.1
The project site is located in a
rural area and the surrounding land uses comprise village type development, government
or community use such as Po Lin Monastery, with the majority of the area being
green belt and
4.4.1.2
Relevant studies of the baseline
noise levels in the Ngong Ping area include the “Outlying Islands Sewerage
Stage 1 Phase 1 Ngong
4.5 Identification of Potential Noise Impacts
4.5.1.1 The potential sources of noise impact during the construction phase of the Project would be the use of PME for various construction activities. According to the construction programme in Figure 2.8b, the construction of the project would tentatively start in August 2013 and last for about 30 months. There are seven major construction activities to be carried out which are relevant to the construction noise assessment, as follows:
· Activity 1: Site formation works (All works areas with Project Area);
· Activities 2: Construction of Site Office (SO);
· Activities 3 and 4: Construction of drainage pipelines (Work Sections 1 and 3, Figure 2.9a) and box culverts (Work Sections 4 and 5, Figure 2.9a) using the cut and cover method with stockpiling activities at the stockpile areas (SA1, SO, SA2, SA3 and SA4);
· Activity 5: Construction of jacking pits (JP1 and JP2, Figure 2.9a) and receiving pits (RP1, RP2, RP3 and RP4, Figure 2.9a) and including mucking-out activities at jacking pits (JP1 and JP2) for the pipe-jacking process in Work Sections 2 and 6; and
· Activity 6: Construction of manholes, intakes and outfalls (SA1, SA2, SA3, WA3, WA4).
· Activity 7: Demolition of Site Office (SO) with associated road reinstatement and landscaping works.
4.5.1.2 For the pipe jacking, as the jacking system would be located at the bottom of the pit which is about 6m below ground level, the noise of the jacking machine would be effectively shielded from the sensitive receivers. Thus, it would not be considered as a potential noise impact during the construction phase. However, other PMEs such as air compressor, lorry and mobile crane, etc., which would be required for the pipe jacking process would be at ground level and these would be considered as potential noise sources in the noise assessment.
4.6.1.1 There are no concurrent projects identified that would have the potential to result in cumulative noise impacts at the NSRs during the same construction period of the Project.
4.7 Assessment Approach and Assumptions
4.7.1.1 In accordance with the EIAO-TM, the methodology outlined in the GW-TM has been used for the construction noise assessment. The general approach is summarised below:
· Locate the NSRs which would most likely be affected by the noise from construction works;
· Determine the items of PME for each discrete construction activity, based on the available information or agreed plant inventories;
· Assign sound power levels (SWLs) to the proposed PME according to the GW-TM or other sources;
· Calculate the distance attenuation and screening effects to NSRs from the noise source;
· Predict the construction noise levels at NSRs in the absence of any mitigation measures; and
· Include a 3dB(A) façade correction to the predicted noise levels in order to account for the façade effect at each NSR.
4.7.2.1 Groups of PME have been assigned to various construction activities of the project and the full plant inventory is presented in Appendix C3. The key PME to be used for the construction works activities are shown in Table 4.4 below. The Project Proponent has confirmed this plant inventory as being practical and adequate for completing the construction works within the scheduled timeframe and the is presented in Appendix B1. The plant inventory has been provided as one option which is considered technically feasible and represents a realistic worst-case scenario for assessment purposes in this EIA.
4.7.2.2 The on-time of each piece of equipment has been estimated with the reference of EIAO-GN 9/2004 to reflect the actual situation and is considered practicable and the percentages of time have been considered when calculating the cumulative Sound Power Levels (SWL) for the construction activities.
Table
4.4 PME Identified as Major Noise Sources for the Unmitigated
Scenario
|
ID |
PME |
CNP |
No. of Item |
SWL, dB(A) |
% on time |
Total SWL, dB(A) |
|
1 |
Activity 1 - Site Clearance |
|||||
|
1a |
Felling of Trees |
|||||
|
Saw, Chain, Hand-Held |
CNP
202 |
1 |
114 |
50% |
111 |
|
|
1b |
Removal of Trees |
|||||
|
Excavator/Loader,
Wheeled/Tracked |
CNP 081 |
1 |
112 |
70% |
114 |
|
|
Dump Truck, gross vehicle weight > 38
tonne |
CNP
067 |
1 |
117 |
30% |
||
|
2 |
Activity 2 – Construction of Site Office |
|||||
|
Concrete
Lorry Mixer |
CNP 044 |
1 |
109 |
50% |
112 |
|
|
Excavator/Loader,
Wheeled/Tracked |
CNP 081 |
1 |
112 |
70% |
||
|
Generator,
Silenced, 75 dB(A) at 7m |
CNP 102 |
1 |
100 |
100% |
||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
3 |
Activity 3 – Laying of Pipe by Open-cut Method |
|||||
|
3a |
Excavation and installation of earth lateral
support system |
|||||
|
3a-1 |
Excavation and installation of earth lateral
support system – Excavation |
|||||
|
Excavator/Loader,
Wheeled/Tracked |
CNP 081 |
1 |
112 |
70% |
111 |
|
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
3a-2 |
Excavation and installation of earth lateral
support system - Sheet Piling |
|||||
|
Piling, vibrating hammer |
CNP
172 |
1 |
115 |
50% |
112 |
|
|
3a-3 |
Excavation and installation of earth lateral
support system - Delivery of Precast Elements |
|||||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
100 |
|
|
3a-4 |
Excavation and installation of earth lateral
support system – Generators and Pumps |
|||||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
100 |
|
|
Generator, Silenced, 75 dB(A) at 7m |
CNP
102 |
1 |
100 |
100% |
||
|
3b |
Laying of pipe |
|||||
|
Crane,
Mobile/Barge Mounted (diesel) |
CNP 048 |
1 |
112 |
70% |
111 |
|
|
Generator,
Silenced, 75 dB(A) at 7m |
CNP 102 |
1 |
100 |
100% |
||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
||
|
Winch
(Electric) |
CNP 262 |
1 |
95 |
50% |
||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
3c |
Backfilling the trench |
|||||
|
3c-1 |
Backfilling the trench – Filling |
|||||
|
Dump
Truck, gross vehicle weight > 38 tonne |
CNP 067 |
1 |
117 |
30% |
114 |
|
|
Excavator/Loader, Wheeled/Tracked |
CNP
081 |
1 |
112 |
70% |
||
|
3c-2 |
Backfilling the trench – Compacting |
|||||
|
Compactor, Vibratory |
CNP
050 |
1 |
105 |
50% |
102 |
|
|
3d |
Reinstatement of original pavement |
|||||
|
Concrete
Lorry Mixer |
CNP 044 |
1 |
109 |
50% |
112 |
|
|
Poker,
Vibratory, Hand-held |
CNP 170 |
1 |
113 |
50% |
||
|
Generator, Silenced, 75 dB(A) at 7m |
CNP
102 |
1 |
100 |
100% |
||
|
4 |
Activity 4 – Construction of Box-culvert |
|||||
|
4a |
Excavation and installation of earth lateral
support system |
|||||
|
4a-1 |
Excavation and installation of earth lateral
support system – Excavation |
|||||
|
Excavator/Loader,
Wheeled/Tracked |
CNP 081 |
1 |
112 |
70% |
111 |
|
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
4a-2 |
Excavation and installation of earth lateral
support system – Sheet Piling |
|||||
|
Piling, vibrating hammer |
CNP
172 |
1 |
115 |
50% |
112 |
|
|
4a-3 |
Excavation and installation of earth lateral
support system - Delivery of Precast Elements |
|||||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
100 |
|
|
4a-4 |
Excavation and installation of earth lateral
support system – Generators and Pumps |
|||||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
100 |
|
|
Generator, Silenced, 75 dB(A) at 7m |
CNP
102 |
1 |
100 |
100% |
||
|
4b |
Erection of formwork, steel fixing and concreting |
|||||
|
4b-1 |
Erection of formwork |
|||||
|
Saw,
Circular, Wood |
CNP 201 |
1 |
108 |
50% |
105 |
|
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
4b-2 |
Steel fixing |
|||||
|
Bar
Bender and Cutter (Electric) |
CNP 021 |
1 |
90 |
80% |
90 |
|
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
4b-3 |
Concreting |
|||||
|
Concrete
Lorry Mixer |
CNP 044 |
1 |
109 |
50% |
114 |
|
|
Crane,
Mobile/Barge Mounted (diesel) |
CNP 048 |
1 |
112 |
70% |
||
|
Poker,
Vibratory, Hand-held |
CNP 170 |
1 |
113 |
50% |
||
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
4c |
Backfilling the trench |
|||||
|
4c-1 |
Backfilling the trench – Filling |
|||||
|
Dump
Truck, gross vehicle weight > 38 tonne |
CNP 067 |
1 |
117 |
30% |
114 |
|
|
Excavator/Loader, Wheeled/Tracked |
CNP
081 |
1 |
112 |
70% |
||
|
4c-2 |
Backfilling the trench – Compacting |
|||||
|
Compactor, Vibratory |
CNP
050 |
1 |
105 |
50% |
102 |
|
|
4d |
Reinstatement of original pavement |
|||||
|
Concrete
Lorry Mixer |
CNP 044 |
1 |
109 |
50% |
112 |
|
|
Poker,
Vibratory, Hand-held |
CNP 170 |
1 |
113 |
50% |
||
|
Generator, Silenced, 75 dB(A) at 7m |
CNP
102 |
1 |
100 |
100% |
||
|
5 |
Activity 5 – Laying of Pipe by Pipe-jacking
Method |
|||||
|
5a |
Construction of jacking pits |
|||||
|
5a-1 |
Construction of jacking pits – Excavation |
|||||
|
Breaker,
Excavator Mounted (Hydraulic) |
CNP 028 |
1 |
122 |
70% |
120 |
|
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
5a-2 |
Construction of jacking pits - Delivery of
Precast Elements |
|||||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
100 |
|
|
5a-3 |
Construction of jacking pits - Generators and
Pumps |
|||||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
101 |
|
|
Generator,
Silenced, 75 dB(A) at 7m |
CNP 102 |
1 |
100 |
100% |
||
|
Air blower (electric) |
CNP
006 |
1 |
95 |
50% |
||
|
5b |
Pipe jacking |
|||||
|
Crane,
Mobile/Barge Mounted (diesel) |
CNP 048 |
1 |
112 |
70% |
111 |
|
|
Winch
(Electric) |
CNP 262 |
1 |
95 |
50% |
||
|
Grout
mixer |
CNP 105 |
1 |
90 |
80% |
||
|
Lorry,
5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
105 |
30% |
||
|
Pipe
jacking machine* |
No Noise Impact |
1 |
|
-- |
||
|
Grout
pump |
CNP 106 |
1 |
|
-- |
||
|
Tunnel boring machine* |
No
Noise Impact |
1 |
|
-- |
||
|
5c |
Construction of receiving pits |
|||||
|
5c-1 |
Construction of receiving pits – Excavation |
|||||
|
Breaker,
Excavator Mounted (Hydraulic) |
CNP 028 |
1 |
122 |
70% |
120 |
|
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
5c-2 |
Construction of receiving pits – Delivery of
Precast Elements |
|||||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
100 |
|
|
5c-3 |
Construction of receiving pits – Generators and
Pumps |
|||||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
101 |
|
|
Generator,
Silenced, 75 dB(A) at 7m |
CNP 102 |
1 |
100 |
100% |
||
|
Air blower (electric) |
CNP
006 |
1 |
95 |
50% |
||
|
5d |
Backfilling the pits |
|||||
|
5d-1 |
Backfilling the pits – Filling |
|||||
|
Dump
Truck, gross vehicle weight > 38 tonne |
CNP 067 |
1 |
117 |
30% |
114 |
|
|
Excavator/Loader, Wheeled/Tracked** |
CNP
081 |
1 |
112 |
70% |
||
|
5d-2 |
Backfilling the pits – Compacting |
|||||
|
Compactor, Vibratory |
CNP
050 |
1 |
105 |
50% |
102 |
|
|
6 |
Activity 6 – Construction of Manholes, Inlet and
Outfall Structures |
|||||
|
6a |
Excavation |
|||||
|
6a-1 |
Excavation – Rock Breaking |
|||||
|
Breaker,
Excavator Mounted (Hydraulic) |
CNP 028 |
1 |
122 |
70% |
120 |
|
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
|
6a-2 |
Excavation – Spoil Delivery |
|||||
|
Dump Truck, gross vehicle weight > 38
tonne |
CNP
067 |
1 |
117 |
30% |
114 |
|
|
Excavator/Loader, Wheeled/Tracked** |
CNP
081 |
1 |
112 |
70% |
||
|
6a-3 |
Excavation – Generators and Pumps |
|||||
|
Water
Pump (Electric) |
CNP 281 |
1 |
88 |
50% |
100 |
|
|
Generator, Silenced, 75 dB(A) at 7m |
CNP
102 |
1 |
100 |
100% |
||
|
6b |
Erection of formwork, steel fixing and concreting |
|||||
|
6b-1 |
Erection of formwork |
|||||
|
Saw,
Circular, Wood |
CNP 201 |
1 |
108 |
50% |
105 |
|
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
6b-2 |
Steel fixing |
|||||
|
Bar
Bender and Cutter (Electric) |
CNP 021 |
1 |
90 |
80% |
90 |
|
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
6b-3 |
Concreting |
|||||
|
Concrete
Lorry Mixer |
CNP 044 |
1 |
109 |
50% |
114 |
|
|
Crane,
Mobile/Barge Mounted (diesel) |
CNP 048 |
1 |
112 |
70% |
||
|
Poker,
Vibratory, Hand-held |
CNP 170 |
1 |
113 |
50% |
||
|
Water Pump (Electric) |
CNP
281 |
1 |
88 |
50% |
||
|
6c |
Backfilling |
|||||
|
6c-1 |
Backfilling – Filling |
|||||
|
Dump
Truck, gross vehicle weight > 38 tonne |
CNP 067 |
1 |
117 |
30% |
114 |
|
|
Excavator/Loader, Wheeled/Tracked** |
CNP
081 |
1 |
112 |
70% |
||
|
6c-2 |
Backfilling – Compacting |
|||||
|
|
Compactor, Vibratory |
CNP
050 |
1 |
105 |
50% |
102 |
|
7 |
Activity 7 – Demolition of Site Office with
associated road reinstatement work and landscaping works |
|||||
|
Breaker,
Excavator Mounted (Hydraulic) |
CNP 028 |
1 |
122 |
70% |
121 |
|
|
Dump
Truck, gross vehicle weight > 38 tonne |
CNP 067 |
1 |
117 |
30% |
||
|
Lorry, 5.5 tonne < gross vehicle weight
<= 38 tonne |
CNP
145 |
1 |
105 |
30% |
||
Note:
* Pipe jacking system, grout pump and tunnel boring machine would be located at the bottom of the pit which is about 6m below ground level. The noise of the machines would be effectively shielded from the sensitive receivers and thus would not be considered as a potential noise source in the construction noise assessment.
** For the construction of RP4 and Outfall B at WA4 (task ID 5 and 6), a mini excavator (CNP 082) with SWL in 94 dB(A) will be used instead of the normal excavator (CNP 081) due to lack of space near the works area and access constraints
4.7.2.3 The SWLs of the PME have been taken from Table 3 of the GW-TM. Where no SWLs are provided for individual PME in the GW-TM, reference has been made to the British Standard 5228: Part 1:2009 Noise Control on Construction and Open Sites, previous similar studies or from other EIA reports or measurements taken in other relevant studies.
4.7.2.4 The proposed plant inventory involves the use of some SPME, as detailed in Section 4.2.3.3, including dump trucks and hand-held vibratory pokers. As such, should construction works extend into restricted hours, the DA-TM will become effective and further restrictions on the acceptable noise will be imposed.
4.7.3.1 As detailed in Section 2.7.3 the works will be undertaken based upon two active work fronts, one for the cut and cover (C&C) works of the drainage pipeline and box culvert and another one for the trenchless drain constructions, after site clearance and the site office (SO) establishment. The details of construction sequence and the location of the Works Sections can refer to Section 2.7.3 and Figure 2.9a of the report respectively.
4.7.3.2 For the construction works of the pipeline and the box culvert by cut and cover, it is assumed that the works would be conducted section by section in the specific timeframe according to the construction programme in Figure 2.8b, with each section being approximately 40m in length and taking 2 months to construct.
4.7.4.1 With reference to Table 4.4 above, for Activity 1, during the tree felling removal activities, the excavator and dump truck would not be operating. Therefore, the sub-task Activity 1b with the highest SWL of 114dB(A) has been adopted in the unmitigated noise assessment as a worst case scenario. A similar approach has been adopted for Activity 3, Construction of Pipeline by Cut and Cover Method, with the sub-task Activity 3c with highest SWL of 114dB(A) being adopted in the noise assessment as a worst case scenario as sub-tasks 3a to 3d will not be conducted concurrently during the open cut works area. Similarly, for Activity 4 for the construction of the box culvert the highest SWL being 114dB(A). For Activity 6, the construction of Intake C and Outfall B will not be undertaken at the same time and will be constructed one after the other between Months 16 - 18. Therefore, depending upon the location of the NSR, the task closer to the NSR, that is, with the highest SWL of 120dB(A), has been adopted in the noise assessment. For example, the total SWL of the PME required for the construction of Outfall B has been adopted in the noise assessment of NSR1.
4.7.4.2 For the construction of RP4 and Outfall B involving the Construction of Receiving Pits and Outfall Structures (Tasks ID 5 and 6), a mini robot mounted excavator (CNP 082) will be used instead of the normal excavator as a result of site constraints associated with the lack of working space and access near the works area. The specific plant inventory for construction works at RP4 / Outfall B is given in Table 4.5.
Table 4.5 Specific
Plant Inventory for Construction Works at RP4 / Outfall B for the Unmitigated
Scenario
|
ID |
PME |
CNP |
No. of Item |
SWL, dB(A) |
% on time |
Total SWL, dB(A) |
|
5 |
Activity 5 – Laying of
Pipe by Pipe-jacking Method |
|||||
|
5c+ |
Construction
of receiving pits |
|||||
|
5c-1 |
Construction
of receiving pits – Excavation |
|||||
|
|
Breaker, Excavator
Mounted (Hydraulic) |
CNP
028 |
1 |
70% |
122 |
120 |
|
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
30% |
105 |
|
|
5c-2 |
Construction
of receiving pits - Delivery of Precast Elements |
|||||
|
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
30% |
105 |
100 |
|
5c-3 |
Construction
of receiving pits - Generators and Pumps |
|||||
|
|
Water Pump (Electric) |
CNP
281 |
1 |
50% |
88 |
101 |
|
|
Generator, Silenced, 75
dB(A) at 7m |
CNP
102 |
1 |
100% |
100 |
|
|
|
Air blower (electric) |
CNP 006 |
1 |
50% |
95 |
|
|
5d+ |
Backfillig
the pits |
|||||
|
5d-1 |
Backfillig
the pits – Filling |
|||||
|
|
Dump Truck, gross vehicle
weight > 38 tonne |
CNP
067 |
1 |
30% |
117 |
112 |
|
|
Excavator, mini-robot mounted |
CNP 082 |
1 |
70% |
94 |
|
|
5d-2 |
Backfillig the pits –
Compacting |
|||||
|
|
Compactor, Vibratory |
CNP 050 |
1 |
50% |
105 |
102 |
|
6 |
Activity 6 – Construction
of Manholes, Inlet and Outfall Structures |
|||||
|
6a+ |
Excavation |
|||||
|
6a-1 |
Excavation
- Rock Breaking |
|||||
|
|
Breaker, Excavator
Mounted (Hydraulic) |
CNP
028 |
1 |
70% |
122 |
120 |
|
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
30% |
105 |
|
|
6a-2 |
Excavation
- Spoil Delivery |
|||||
|
|
Dump Truck, gross vehicle
weight > 38 tonne |
CNP
067 |
1 |
30% |
117 |
112 |
|
|
Excavator, mini-robot mounted |
CNP 082 |
1 |
70% |
94 |
|
|
6a-3 |
Excavation
- Generators and Pumps |
|||||
|
|
Water Pump (Electric) |
CNP
281 |
1 |
50% |
88 |
100 |
|
|
Generator, Silenced, 75 dB(A) at 7m |
CNP 102 |
1 |
100% |
100 |
|
|
6b+ |
Erection
of formwork, steel fixing and concreting |
|||||
|
6b-1 |
Erection
of formwork |
|||||
|
|
Saw, Circular, Wood |
CNP
201 |
1 |
50% |
108 |
105 |
|
|
Water Pump (Electric) |
CNP 281 |
1 |
50% |
88 |
|
|
6b-2 |
Steel
fixing |
|||||
|
|
Bar Bender and Cutter
(Electric) |
CNP
021 |
1 |
80% |
90 |
90 |
|
|
Water Pump (Electric) |
CNP 281 |
1 |
50% |
88 |
|
|
6b-3 |
Concreting |
|||||
|
|
Concrete Lorry Mixer |
CNP
044 |
1 |
50% |
109 |
114 |
|
|
Crane, Mobile/Barge
Mounted (diesel) |
CNP
048 |
1 |
70% |
112 |
|
|
|
Poker, Vibratory,
Hand-held |
CNP
170 |
1 |
50% |
113 |
|
|
|
Water Pump (Electric) |
CNP 281 |
1 |
50% |
88 |
|
|
6c+ |
Backfilling |
|||||
|
6c-1 |
Backfilling
– Filling |
|||||
|
|
Dump Truck, gross vehicle
weight > 38 tonne |
CNP
067 |
1 |
30% |
117 |
112 |
|
|
Excavator, mini-robot mounted |
CNP 082 |
1 |
70% |
94 |
|
|
6c-2 |
Backfilling
- Compacting |
|||||
|
|
Compactor, Vibratory |
CNP 050 |
1 |
50% |
105 |
102 |
4.7.4.3 The noise levels at the ground floor of the receivers have been predicted as these are considered to represent a worst-case condition with the shortest distance between the SRs and the notional noise sources, and a 3dB(A) façade correction has been applied. Appendix C2 shows the locations of the assumed notional sources of the PMEs in the noise assessment.
4.7.4.4 As noted above, as concurrent construction activities of various works elements could occur, the works within 300m from the sensitive receiver and within line of sight of the sensitive receiver is counted as cumulative impact for the worst case scenario. Table 4.6 summarises the assumed worst case concurrent construction activities for each sensitive receiver with the distance between the SRs and the noise sources.
Table 4.6 Assumed
Worst Concurrent Construction Activities for Each Sensitive Receiver
|
Notional Sources* |
Slant Distances from NSRs (m) |
||||||||
|
NSR 1 |
NSR 3 |
NSR 4 |
NSR 5 |
NSR 6 |
NSR 7 |
NSR 8 |
NSR 9 |
NSR 11 |
|
|
Intake A (SA1)
(Works Section 1) |
-- |
-- |
-- |
-- |
-- |
226.2 |
-- |
132.0 |
117.2 |
|
Intake B (SA2)
(Works Section 4) |
-- |
193.9 |
172.4 |
90.1 |
202.1 |
-- |
274.2 |
-- |
-- |
|
Intake C (WA3)
(Works Section 6) |
183.3 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
Outfall A (SA3)
(Works Section 5) |
-- |
40.8 |
52.6 |
93.3 |
283.4 |
-- |
-- |
-- |
-- |
|
Outfall B (WA4)
(Works Section 6) |
18.7 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
JP 1 (SO) (Works Section 2) |
-- |
-- |
-- |
288.6 |
-- |
64.3 |
26.3 |
39.1 |
76.0 |
|
JP 2 (SA4) (Works Section 6) |
123.1 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
RP 1 (WA1) (Works Section 1) |
-- |
-- |
-- |
-- |
-- |
120.4 |
57.2 |
25.7 |
42.4 |
|
RP 2 (WA2) (Works Section 2) |
-- |
299.0 |
248.6 |
176.1 |
24.5 |
-- |
129.1 |
167.2 |
202.5 |
|
RP 3 (WA3) (Works Section 2) |
183.3 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
RP 4 (WA4) (Works Section 6) |
18.7 |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
-- |
|
SO (SO) (Works Section 2) |
-- |
-- |
-- |
254.4 |
-- |
35.5 |
35.9 |
56.2 |
89.1 |
|
Section A1 (Works Section 1) |
-- |
-- |
-- |
-- |
-- |
196.1 |
-- |
99.3 |
84.1 |
|
Section A2 (Works Section 1) |
-- |
-- |
-- |
-- |
-- |
164.6 |
99.6 |
63.7 |
50.4 |
|
Section A3 (Works Section 1) |
-- |
-- |
-- |
-- |
-- |
127.6 |
65.4 |
30.5 |
35.9 |
|
Section A4 (Works Section 3) |
-- |
-- |
214.1 |
136.7 |
33.0 |
-- |
141.9 |
178.6 |
213.4 |
|
Section A5 (Works Section 3) |
-- |
233.2 |
187.4 |
104.7 |
79.2 |
-- |
176.6 |
-- |
235.1 |
|
Section A6 (Works Section 3) |
-- |
193.5 |
157.7 |
68.0 |
119.6 |
-- |
208.4 |
-- |
261.6 |
|
Section B1 (Works Section 4) |
-- |
193.5 |
163.8 |
74.8 |
166.8 |
-- |
265.3 |
-- |
289.6 |
|
Section B2 (Works Section 5) |
-- |
165.7 |
127.1 |
37.5 |
164.6 |
-- |
252.0 |
-- |
299.7 |
|
Section B3 (Works Section 5) |
-- |
134.3 |
92.1 |
6.5 |
175.1 |
-- |
275.1 |
-- |
-- |
|
Section B4 (Works Section 5) |
-- |
101.6 |
58.1 |
13.5 |
192.8 |
-- |
-- |
-- |
-- |
|
Section B5 (Works Section 5) |
-- |
68.8 |
29.9 |
42.2 |
220.3 |
-- |
-- |
-- |
-- |
|
Section B6 (Works Section 5) |
-- |
44.5 |
33.7 |
71.9 |
252.1 |
-- |
-- |
-- |
-- |
Note:
* refer to Appendix C4 for the locations of the notional sources. Reference in bracket refers to Works Areas as detailed in Table 2.13 or Works Sections detailed in Table 2.7.
“--“ denotes the works site is more than 300m from the NSR or no there is no line of sight from the NSR.
4.7.5.1 The predictions of construction noise impacts have been based on the methodologies described in the GW-TM under the NCO. The methodologies which have previously been applied in other EIA studies are generally accepted for use in assessing construction noise impact against the EIAO-TM noise criteria. In carrying out the assessment, realistic worst case assumptions have been made in order to provide a conservative assessment of potential noise impacts. The construction noise impact has, therefore, been assessed based on conservative estimates for the types of plant to be utilised and the methods of working.
4.7.5.2 There are some limitations in the approach, such as the accuracy of predictive base data for future conditions, e.g. plant inventory for the proposed construction works. Uncertainties in the assessment of impacts have been considered when drawing conclusions from the assessment and worst case assessments made overall.
4.8 Construction Noise Assessment Results
4.8.1 Construction Noise Impact – Unmitigated Scenario
4.8.1.1 A summary of the predicted unmitigated maximum noise levels are provided in Table 4.7 below. The details of the predicted unmitigated noise levels at the representative NSRs during each construction months are presented in Appendix C4.
Table 4.7 Predicted
Unmitigated Construction Noise Levels for Representative NSRs
|
NSR |
Location |
Maximum Predicted
Construction Noise Level, dB(A) |
EIAO -TM Noise Criteria,
dB(A) |
|
NSR1 |
Columbarium of |
91 |
70 |
|
NSR3 |
Village House No. 68 |
83 |
75 |
|
NSR4 |
Village House No. 65 |
81 |
75 |
|
NSR5 |
Village House No. 49A |
93 |
75 |
|
NSR6 |
Village House No. 40 |
88 |
75 |
|
NSR7 |
Luen Sin Tong |
85 |
70 |
|
NSR8 |
Village House No. 34 |
88 |
75 |
|
NSR9 |
Village House |
89 |
75 |
|
NSR11 |
|
84 |
70 |
|
|
Denotes exceedance of the noise criteria |
||
4.8.1.2 The results indicate that the noise levels at all sensitive receivers will exceed the day-time noise criteria of 75dB(A) for the residential developments and 70dB(A) for the places of public worship during the construction activities for varying periods of time. Based upon these results, noise mitigation measures will be necessary in a number of locations to reduce the noise to acceptable levels.
4.8.2.1 One of the sources of exceedances is identified to be Activity 1 – Site Clearance. This activity would be conducted along the whole alignment which will become very close to some NSRs (up to 6m). However, removal of trees would require a top down approach and according to the tree survey conducted for the area, the trees scheduled to be felled are up to a maximum of 14m tall. Thus, a noise barrier of a sufficient height to screen the high works when cutting at top sections of the trees would not be feasible.
4.8.2.2 Therefore, in order to mitigate the exceedances from the site clearance works, which is largely as a result of the use of the chain saw in close proximity to the NSRs, it is recommended that a quieter chain saw be used to mitigate the exceedances. The chain saw can be replaced with an electric chain saw with a lower noise level to reduce the noise impact to the residents during tree felling. A commonly available model, for example, the Husqvarna 316 Electric Chain Saw, has a rated maximum noise emission level of 103dB(A), which is 11dB(A) lower than the diesel powered chain saw previously assumed. Such electricity powered chain saws will effectively reduce construction noise emissions during site clearance and, thus, an electric saw with a SWL of 103dB(A) or lower is recommended for use in Activity 1. The brochure for the Husqvarna 316 Electric Chain Saw has been included in Appendix C5.
4.8.2.3
Use of other quiet equipment with lower SWL has been recommended to
reduce the noise impacts for this Project.
The list of assumed quieter equipment, and their respective SWLs, is presented
in Table
4.8 below.
Table
4.8 Mitigated Quiet PMEs
|
PME |
Reference* |
SWL,
dB(A) |
|
Tracked excavator fitted with hydraulic
rock breaker |
BS
D8/13# |
110 |
|
Concrete lorry mixer |
BS
D6/33 |
96 |
|
Tracked mobile crane (132kW, 55t) |
BS
C3/29 |
98 |
|
Dump Truck |
BS
D9/39 |
103 |
|
Tracked excavator (14t) |
BS
C2/7 |
98 |
|
Generator, Super Silenced, 70 dB(A) at 7m |
CNP
103 |
95 |
|
Poker vibratory |
BS
C4/34 |
97 |
|
Hand Held Electric Circular Saw, 150mm
Blade |
BS
D7/75 |
105 |
|
Electric Chain-Saw, Hand-held |
Ref
1+ |
103 |
|
Water Pump, Submersible (Electric) |
CNP
283 |
85 |
Note:
* reference to the British Standard BS5228-1:2009 Code of practice for noise and vibration control on construction and open sites – Part 1: Noise.
+ Reference was made to Husqvarna Model 316 Electric Chain Saw, rated power being 1600W and guaranteed maximum noise emissions being 103dB(A) as provided by manufacturer.
# Sheetpile installation would be part of the earth lateral support system. An excavator with a mounted vibrating hammer, with a noise level similar to a breaker, would be used for this installation work. Therefore, the assessment has been made with reference to an excavator mounted breaker.
4.8.2.4 Due to severe space constraints within the village, the installation of fixed temporary barriers of 2.5m high along the site boundary are not considered feasible for most of the areas as there is not sufficient space to provide the deep foundations needed to compensate for the wind loading that would occur on barriers of this height.
4.8.2.5 In respect of WA4 which is adjacent to the Columbarium (NSR1), the Columbarium itself is surrounded by two solid boundary walls of about 2.5m high and about 200mm thick which are sufficient to act as a fixed barrier. However, at intervals along the wall, vertical gaps in the wall are present which would reduce the attenuation properties of the boundary wall. As such, it is recommended that, during the construction phase at WA4, the gaps in the wall, along the front edge of the Columbarium facing the works, be covered with acoustic fabric or small barrier sections to increase the screening to NSR1 from the noise during the construction of Outfall B and RP4. A noise attenuation level of 10dB(A) for the PME, as detailed in Table 4.9 below, has been assumed for the upgraded Columbarium boundary wall. It should be noted that the access gate to the facility will not be affected. If acoustic fabric is not used, any barrier material should have a surface density of at least 10kg/m2. Figure 4.4 shows the cross section between the construction works site and public in NSR1 demonstrating how the boundary wall can shield the public within the Columbarium from works at WA4.
Table
4.9 Noise Attenuation of PMEs from the Fixed
Temporary Noise Barrier for NSR1
|
PME |
Reduction Level (dB(A)) |
|
Tracked mobile crane (132kW, 55t) |
10 |
|
Poker vibratory |
10 |
|
Concrete lorry mixer |
10 |
|
Hand Held Electric Circular Saw, 150mm Blade |
10 |
|
Tracked excavator fitted with hydraulic rock breaker |
10 |
|
Dump Truck |
10 |
|
Air blower (electric) |
10 |
|
Bar Bender and Cutter (Electric) |
10 |
|
Compactor, Vibratory |
10 |
|
Excavator, mini-robot mounted |
10 |
|
Generator, Super Silenced, 70 dB(A) at 7m |
10 |
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
10 |
|
Water Pump, Submersible (Electric) |
10 |
4.8.2.6 As fixed temporary barriers along the works boundary are not feasible, with reference to the EIA Report of Kwun Tong Line Extension (AEIAR-154/2010), the following mitigation measures have been recommended to reduce the noise impacts from specific PMEs:
· Use of mobile temporary noise barriers at individual movable and stationary PMEs. The barriers should be about 2m high which considering the low rise residential sensitive receivers would be considered sufficient for screening purposes. The barrier material shall have a surface density of at least 10kg/m2 to effectively provide noise screening. With reference to EIAO Guidance Note No.9/2004, noise reductions of 5dB(A) and 10dB(A) can be achieved by direct application of the noise barriers to movable and stationary plant, respectively; and
· Use of enclosures with covers at the top and three sides and a surface density of at least 10kg/m2 to screen noise from generally static noisy plant, such as air compressors.
4.8.2.7 Table 4.10 below summarises the mitigation measures to be adopted for PMEs being operated in all the works areas and the respective reductions in noise levels.
Table 4.10 Mitigation
Measures and Assumed Effectiveness for PMEs
|
PME |
Mitigation Measures |
Reduction
Level (dB(A)) |
|
Bar Bender and Cutter (Electric) |
Noise
Enclosure |
10 |
|
Tracked excavator fitted with hydraulic rock breaker |
Temporary Noise barrier |
5 |
|
Tracked excavator (14t) |
Temporary Noise barrier |
5 |
|
Generator, Super Silenced, 70 dB(A) at 7m |
Noise
Enclosure |
10 |
|
Hand Held Electric Circular Saw, 150mm Blade |
Noise
Enclosure |
10 |
4.8.3 Construction Noise Impact – Mitigated Scenario
4.8.3.1 The mitigated sound power levels for the construction equipment are
presented in Appendix C6. After the implementation of the noise
mitigation measures recommended above, the noise levels at NSR5 would still
exceed the criteria. Residual impacts of
between 4-11dB(A) are predicted. The details of the predicted noise levels at
the NSRs with the implementation of the practicable mitigation measures detailed
above during the construction works are presented in Appendix
C7, with a summary provided in Table
4.11
below.
Table 4.11 Predicted
Mitigated Construction Noise Levels and Duration at Representative NSRs
|
NSR |
Range of Predicted
Construction Noise Level, dB(A) |
EIAO -TM Noise Criteria,
dB(A) |
Period Exceeding the Noise Standard |
Remarks |
|
NSR1 |
55 – 70 |
70 |
-- |
-- |
|
NSR3 |
50 – 71 |
75 |
-- |
-- |
|
NSR4 |
50 – 74 |
75 |
-- |
-- |
|
NSR5 |
48 – 86 |
75 |
Up to 1 week |
Month 1: Tree removal works with SPL of 79dB(A) to the
NSR which will be affected for 2 – 3 days only. Between Month 21 – 24: Construction works for the box culvert (Activity 4) at Chainage B0+45
to B2+22 , with SPL of up to 86dB(A) to the NSR in
these 3-4 days. |
|
NSR6 |
48 – 72 |
75 |
-- |
-- |
|
NSR7 |
50 – 70 |
70 |
-- |
-- |
|
NSR8 |
51 – 73 |
75 |
-- |
-- |
|
NSR9 |
52 – 73 |
75 |
-- |
-- |
|
NSR11 |
49 – 69 |
70 |
-- |
-- |
|
|
Denotes exceedance of the noise criteria |
|
||
4.8.3.2 The NSR5 will be affected by the site clearance works in the first month. It should be noted that site clearance works will apply to the whole alignment which is about 1km long in total and the clearance works as a whole would only last for 1 month. Thus, in reality, the affected NSRs would suffer from exceedances from site clearance for 2 – 3 days only. The exceedances at NSR 5 will be about 4 dB(A) but for this short duration only. An electric chain saw has already been assumed and no further practical mitigation measures are considered to be available,
4.8.3.3 In addition to the exceedance from the site clearance works, the exceedance at NSR5 would, also, be related to the sheet piling works during the box culvert construction (Activity 4) between Chainages B0+45 to B2+22 between Months 21 and 24 (Works Section 5). Further practicable mitigation measures, such as a fixed temporary noise barrier, have, therefore, been considered at this NSR to be implemented during this activity.
4.8.3.4 The noise exceedance would only be induced during sheet piling works which is assumed to be carried out by a hydraulic breaker. Calculations have showed that with the maximum SWL of Activity 4 being 107dB(A), NSR5 would suffer from exceedances only when construction works are carried out within 22m either side of the NSR. Hence, the actual box-culvert works where exceedances would be anticipated would be for a total alignment length of about 44m only. Sheet piling works within this particular 44m segment would take about 3 – 4 days only to complete. The extent of the segment is shown in Figure 4.5.
4.8.3.5 Since NSR5 is a single storey village house, a fixed noise barrier of 3m in height can be installed between the NSR and the open cut trench along the 44m segment in order to further mitigate the construction noise impacts from the sheet piling work. Other PMEs, such as excavator, and vibratory poker, would also benefit from the barrier. The plant inventory assessed for Activity 4 (renumbered as Activity 4+ below) when construction works are in close proximity to NSR5 is given in Table 4.12 below and Appendix C6. An illustration of the positioning of the barrier is given in Figure 4.6.
Table 4.12 Further
Mitigated Plant Inventory for Activity 4+ with Additional Noise Barrier near
NSR5
|
ID |
PME |
Ref |
No of Item |
% on time |
SWL, dB(A) |
Mitigation Measures and
Attenuation |
Total SWL, dB(A) |
|
|
4+ |
Activity 4+ –
Construction of Box-culvert with additional Noise Barrier |
|||||||
|
4a |
Excavation and
installation of earth lateral support system |
|||||||
|
4a-1 |
Excavation and
installation of earth lateral support system - Excavation |
|||||||
|
|
Tracked excavator (14t) |
BS
C2/7 |
1 |
70% |
98 |
Fixed
Noise barrier |
-5 |
100 |
|
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
30% |
105 |
|
|
|
|
4a-2 |
Excavation and
installation of earth lateral support system - Sheet Piling |
|||||||
|
Tracked excavator fitted with hydraulic rock breaker |
BS D8/13 |
1 |
50% |
110 |
Fixed Noise barrier |
-5 |
102 |
|
|
4a-3 |
Excavation and
installation of earth lateral support system - Delivery of Precast Elements |
|||||||
|
|
Lorry, 5.5 tonne < gross vehicle weight <= 38 tonne |
CNP 145 |
1 |
30% |
105 |
|
|
100 |
|
4a-4 |
Excavation and installation
of earth lateral support system - Generators and Pumps |
|||||||
|
|
Water Pump, Submersible
(Electric) |
CNP
283 |
1 |
50% |
85 |
Fixed
Noise Barrier |
-5 |
86 |
|
|
Generator, Super Silenced, 70 dB(A) at 7m |
CNP 103 |
1 |
100% |
95 |
Noise Enclosure |
-10 |
|
|
4b |
Erection of formwork,
steel fixing and concreting |
|||||||
|
4b-1 |
Erection of formwork |
|||||||
|
|
Hand Held Electric
Circular Saw, 150mm Blade |
BS
D7/75 |
1 |
50% |
105 |
Noise
Enclosure |
-10 |
92 |
|
|
Water Pump, Submersible (Electric) |
CNP 283 |
1 |
50% |
85 |
Fixed
Noise Barrier |
-5 |
|
|
4b-2 |
Steel fixing |
|||||||
|
|
Bar Bender and Cutter
(Electric) |
CNP
021 |
1 |
80% |
90 |
Noise
Enclosure |
-10 |
81 |
|
|
Water Pump, Submersible (Electric) |
CNP 283 |
1 |
50% |
85 |
Fixed
Noise Barrier |
-5 |
|
|
4b-3 |
Concreting |
|||||||
|
|
Concrete lorry mixer |
BS
D6/33 |
1 |
50% |
96 |
|
|
96 |
|
|
Tracked mobile crane
(132kW, 55t) |
BS
C3/29 |
1 |
70% |
98 |
Fixed
Noise Barrier |
-5 |
|
|
|
Poker vibratory |
BS
C4/34 |
1 |
50% |
97 |
Fixed
Noise barrier |
-5 |
|
|
|
Water Pump, Submersible (Electric) |
CNP 283 |
1 |
50% |
85 |
Fixed
Noise Barrier |
-5 |
|
|
4c |
Backfilling the trench |
|||||||
|
4c-1 |
Backfilling the trench -
Filling |
|||||||
|
|
Dump Truck |
BS
D9/39 |
1 |
30% |
103 |
|
|
99 |
|
|
Tracked excavator (14t) |
BS C2/7 |
1 |
70% |
98 |
Fixed Noise barrier |
-5 |
|
|
4c-2 |
Backfilling the trench -
Compacting |
|||||||
|
|
Compactor, Vibratory |
CNP 050 |
1 |
50% |
105 |
Fixed Noise barrier |
-5 |
97 |
|
4d |
Reinstatement of original
pavement |
|||||||
|
|
Concrete lorry mixer |
BS
D6/33 |
1 |
50% |
96 |
|
|
95 |
|
|
Poker vibratory |
BS
C4/34 |
1 |
50% |
97 |
Fixed
Noise barrier |
-5 |
|
|
|
Generator, Super Silenced, 70 dB(A) at 7m |
CNP 103 |
1 |
100% |
95 |
Noise Enclosure |
-10 |
|
4.8.3.6 With the additional noise barrier, the construction noise impacts at NSR5 are further mitigated to 81dB(A) at the worst case separation distance of 6m only and exceedances would not be anticipated until construction works are carried out within 13m of NSR5, representing a segment of about 24m, as shown in Figure 4.5. The construction works within the 13m zone would be undertaken in about 3 days and, therefore, the exceedance duration is also reduced. Table 4.13 below shows the calculation of noise impact at different separation distances from NSR5 with (Activity 4+) and without (Activity 4) the proposed noise barrier.
Table 4.13 Further
Mitigated Scenario for NSR5
|
Activity ID |
Activity SWL, dB(A) |
Separation Distance, m |
Distance Attenuation,
dB(A) |
Noise Impact at NSR5 |
|
Activity 4 |
107 |
22 |
-32 |
75 |
|
13 |
-27 |
80 |
||
|
10 |
-25 |
82 |
||
|
6 |
-21 |
86 |
||
|
Activity 4+ |
102 |
22 |
-32 |
70 |
|
13 |
-27 |
75 |
||
|
10 |
-25 |
77 |
||
|
6 |
-21 |
81 |
4.8.3.7 Notwithstanding the above measures, good site practices are, also, recommended to reduce noise levels as far as possible. These measures include the following:
· Only well-maintained plant should be operated on-site and PME should be serviced regularly during the construction programme;
· Silencers or mufflers on construction equipment should be utilised and properly maintained throughout the construction programme;
· Any mobile PME should be sited as far from NSRs as possible;
· Machines and PME that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;
· PME known to emit noise strongly in one direction should be orientated to direct away from the nearby NSRs;
· Material stockpiles and other structures should be effectively utilised, wherever practicable, in screening noise from on-site construction activities;
· Use of acoustic enclosure, in accordance with EPD’s A Practical Guide for the Reduction of Noise from Construction Works; and
· Re-scheduling of works should be considered to ameliorate the residual impact.
4.8.3.8 Given that the recommended measures have been tried and tested and
previously implemented on construction sites in
4.10.1.1 The residual impacts refer to the net impacts after mitigation, taking into account the background environmental conditions and the impacts from existing, committed and planned projects. Residual impacts associated with the construction have been assessed but no quantification of residual impacts is required.
4.10.1.2 Although all practicable mitigation measures have been applied, NSR5 will still be subject to residual impacts of up to 6dB(A) for a maximum duration of about 1 week. NSR5 will be affected by the site clearance works for a few days, and will be further affected by Activity 4 for a duration of 3 days.
4.10.1.3 The magnitude of the residual impacts has been assessed in accordance with Section 4.4.3 of the EIAO-TM in Table 4.14 below.
Table 4.14 Assessment
of Residual Impacts from Construction Noise
|
Criteria |
Assessment |
|
Effects on public health and health of biota or risk to life. |
The extent of noise nuisance would be unlikely to induce public health concern. |
|
Magnitude of the adverse environmental impacts. |
Residual impacts of between 4-6dB(A) could occur at 1 NSR during the construction phase based upon worse case scenarios. |
|
Geographic extent of the adverse environmental impacts. |
The geographic extent of the adverse impacts from noise will not be large and is anticipated to be limited to within about 40m from the drainage improvement project works area. |
|
Duration and frequency of the adverse environmental impacts. |
The construction noise impacts of the project will be maximum of 1 week only and are, therefore, temporary and reversible. |
|
Likely size of the community or the environment that may be affected by the adverse impacts. |
2 residents could be affected. In addition, pedestrians within immediate vicinity will be temporarily affected. The size of the community can be considered small and acceptable. |
|
Degree to which the adverse environmental impacts are reversible or irreversible. |
Construction phase impacts should be reversible. |
|
Ecological context. |
Not Applicable |
|
Degree of disruption to sites of cultural heritage. |
Minimal as there would be no important cultural heritage resources in the immediate vicinity of works sites |
|
International and regional importance. |
The impacts are localised and not of international and regional importance. |
|
Likelihood and degree of uncertainty of adverse environmental impacts. |
The impacts predicted are based upon worst case assumptions and as such, would not occur to the extent predicted on all occasions. However, the assessment has been made using approved mathematical modelling techniques and the degree of certainty on the results is high. |
4.10.1.4 Based upon the above, the following factors should be considered in determining the residual impacts:
· The noise impacts are not predicted to significantly affect health or cause loss of life;
· The predicted impacts are short term, temporary and reversible;
· Impacts are localised and not of international and regional importance;
· The geographic extent of the adverse impacts is confined to small areas around the works sites at two specific locations only and would not unduly affect the welfare of the local community or adjacent agricultural activities;
· The mitigation measures proposed will reduce the overall levels of impacts; and
· The study area has not shown itself to be fragile or undisturbed.
4.10.1.5 As such, given the benefits of the project to the local community and the very short term nature of the residual impacts predicted, the residual impacts associated with the construction phase exceedances for the drainage improvement works would be considered minor and acceptable.
4.11 Environmental Monitoring and Audit
4.11.1.1 The assessment has concluded that, despite the implementation of the maximum practicable extent of mitigation measures, adverse residual impacts during the construction phase will occur as a result of the implementation of the project. As such, it is recommended that construction phase environmental monitoring and audit (EM&A) is undertaken to ensure that impacts do not occur beyond unavoidable levels. It is noted that during the construction process, episodes of noise higher levels may occur and it will be the function of the EM&A process to identify these events and take the necessary action such as, for example, temporarily adjustment of the number of plant to be used or an equivalent measure as necessary.
4.11.1.2 Further details of the specific EM&A requirements are detailed in Section 10 of this report and in the EM&A Manual under separate cover. The procedure for complaints will include the provision of a hotline number for the public to use when required.
4.12.1.1 The results of the construction noise assessment indicate that the noise levels at 1 NSR, after the implementation of all practical direct mitigation measures, would still exceed the stipulated noise criteria in some locations for a short duration of 1 week only. However, the residual impacts have been assessed and concluded to be temporary, reversible and unlikely to induce public health concerns to the community and as such, are considered to be minor and acceptable.