Noise Impact Assessment

4. NOISE IMPACT ASSESSMENT

4.1 Introduction

4.1.1 This Chapter presents an assessment of noise impacts associated with the construction and operation of the proposed Project.

4.1.2 Noise generated during the construction phase by works activities and powered mechanical equipment would pose potential impact to the surrounding Noise Sensitive Receivers (NSRs). Appropriate mitigation measures are recommended where necessary to mitigate such impacts.

4.1.3 The proposed access road along the northern channel bank will be open to public use. In addition, a viewing point and carpark will be constructed at the channel outfall. The introduction of road traffic along the maintenance access road may pose potential traffic noise impact to nearby noise sensitive receivers during operation. Operational phase of the channel would only involve small scale routine maintenance and is not expected to generate any excessive noise.

4.2 Noise Criteria

Construction Noise

4.2.1 There are currently no statutory criteria for noise generated from construction work other than percussive piling during the daytime hours of 07:00-19:00, Monday to Saturday, excluding Sunday and public holidays. However, there is provision in the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) for assessing noise from construction activities during daytime.

4.2.2 The noise standards for general construction works during normal working hours (i.e. 0700 to 1900 hours on any day not being a Sunday or public holiday) stipulated in Table 1B of Annex 5 of the EIAO-TM are given in Table 4.1.

Table 4.1

EIAO-TM Daytime Construction Noise Standards

Uses	Daytime Construction Noise Standards, Leq (30 minutes) dB(A)
Domestic Premises	75
Educational institutions (normal periods)	70
Educational institutions (during examination periods)	65

Notes:

These standards assume the use of open windows for ventilation. They are the maximum permissible noise levels assessed at 1 m from the receiver’s external façade.

4.2.3 The principal legislation on the control of construction noise during restricted hours is the Noise Control Ordinance (NCO) (Cap.400) and its associated Technical Memoranda (TM). The NCO provides statutory controls on general construction works during the restricted hours (i.e. 1900 to 0700 hours Monday to Saturday and at any time on Sundays and public holidays). The Contractor shall comply with the NCO and all relevant regulations under this Ordinance, including restrictions placed on noise from construction work and the requirements to seek Construction Noise Permit (CNP). At present, construction works during restricted hours are not expected. However, should works have to be carried out during restricted hours, a CNP must be obtained from the relevant Noise Control Authority (i.e. EPD) before the works are allowed to take place. Percussive piling works are also subjected to CNP licensing under the NCO. The Contractor is also required to display these permits appropriately.

4.2.4 Despite the description or assessment made in the subsequent sections, 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 by the relevant Technical Memorandum (Memoranda) issued under the NCO. The Noise Control Authority will take into account of contemporary situations/conditions 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 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 conditions that are considered appropriate and such conditions are to be followed while the works covered by the permit are being carried out. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

Road Traffic Noise

4.2.5 Road traffic noise criteria are listed in Table 1A of Annex 5 of the EIAO-TM and listed in Table 4.2 below.

Table 4.2

Road Traffic Noise Criteria

Noise Sensitive Uses	Peak Hour Traffic, L_{10(1 hour)}, dB(A)
All domestic premises, hotels, offices and temporary housing accommodation	70
Educational institutions including kindergartens, nurseries and all others where unaided voice communication is required, places of public worship and courts of law	65
Hospitals, clinics, convalescences and home for the aged, diagnostic rooms, wards	55

Notes:

The above standards apply to uses which rely on opened windows for ventilation.

The above standards should be viewed as the maximum permissible noise levels assessed at 1 m from the external façade.

4.2.6 According to EIAO Guidance Note No. 12/2005 – “Road Traffic Noise Impact Assessment Under the EIAO”, for road traffic noise, in cases where practicable direct mitigation measures would not be wholly adequate in mitigating noise impacts, indirect mitigation measures in the form of window insulation and air-conditioning is often the “last resort” in an attempt to ameliorate the residual impact.

4.2.7 On the eligibility testing criteria for indirect noise mitigation measures, reference is made to the relevant procedures stipulated in Calculation of Road Traffic Noise (CRTN) (paragraph 6 on Requirements for use with the Noise Insulation Regulations) which is used for the assessment of road traffic noise as per Section 5.1, Annex 13 of the EIAO-TM. The testing criteria are set out as below:

(i) the predicted overall noise level from the the road project together with other traffic noise in the vicinity must be above a specified noise level (e.g. 70 dB(A) for domestic premises and 65 dB(A) for education institutions, all in L_10(1hr));

(ii) the predicted overall noise level is at least 1.0 dB(A) more than the prevailing traffic noise level, i.e. the total traffic noise level existing before the works to construct the road were commenced; and

(iii) the contribution to the increase in the predicted overall noise level from the road project must be at least 1.0 dB(A).

4.2.8 For the purpose of this EIA Study, all roads are described as either:

· ‘existing’ which are the existing roads that are unchanged by the Project; or

· ‘new’ which is the proposed access road.

4.3 Study Area

Noise Assessment Study Area

4.3.1 For the purpose of noise assessment, the Study Area covers essentially 300 m from the boundary of each of the work sites of the Project. This Study Area can be reduced if the first layer of the noise sensitive receivers, closer than 300 m from the boundary, provides acoustic shielding to those receivers at further distance behind.

Description of the Existing Noise Environment

4.3.2 The major landuse in the vicinity of the Project area is village environs. Some industrial establishments, such as open storage sites and container yards, can be found along Deep Bay Road. Commercial activities such as seafood market and restaurants can be found at Lau Fau Shan which is well over 300 m to the north of the Project.

4.3.3 The existing noise environment near the upstream portion of Hang Hau Tsuen stream is dominated by the road traffic on Deep Bay Road and Lau Fau Shan Road. These roads carry a substantial amount of heavy goods vehicles and container lorries that utilize the various open storage sites and container yards in the vicinity. As such, sensitive receivers near the upstream portion are affected by traffic noise as well as industrial noise from the open storage sites and container yards. The downstream portion which is away from the roads is generally quiet with marine traffic and local village activities being the dominant noise source.

4.3.4 Noise generated by the commercial activities at Lau Fau Shan is considered to be insignificant.

4.4 Representative Noise Sensitive Receivers

4.4.1 The Representative Noise Sensitive Receivers (NSRs) chosen for noise assessment are shown in Figure 4.1. Photographs showing these NSRs are shown in Figure 1 of Appendix 4.1. These Representative NSRs are selected in accordance with the criteria in Annex 13 of the EIAO-TM. Reference has been made to the landuses annotated under the following latest Outline Zoning Plans (OZPs): S/YL-HT/9 and S/YL-LFS/7. Based on the available information at the time of assessment, there is an approved residential development to the north of the Project (TPB Application No. A/YL-LFS/156). However, no development layout or programme is available at the time of the EIA Study. A description of the Representative NSRs is tabulated in Table 4.3.

Table 4.3

Representative Noise Sensitive Receivers (NSRs)

Representative NSR	General Description	No. of Floors	Approximate Horizontal Distance from Construction Activities (Notional Point Source)	Shortest Horizontal Distance to Road Kerb
NSR 1	Wing Jan Kindergarten	1	42 m	82 m to New Road 60 m to Deep Bay Road
NSR 2	Wing Jan Camp	1	17 m	32 m to New Road 45 m to Deep Bay Road
NSR 3*	Village house at No. 84 Hang Hau Tsuen	2	15 m	10 m to New Road 154 m to Deep Bay Road
NSR 4*	Village house at No. 57 Hang Hau Tsuen	1	15 m	16 m to New Road 267 m to Deep Bay Road
NSR 5*	Village house at No. 26 Hang Hau Tsuen	2	16 m	15 m to New Road
NSR 6*	Village house at No. 88 Hang Hau Tsuen	2	14 m	30 m to New Road
NSR 7	House at Deep Bay Grove	3	165 m	175 m to New Road 48 m to Deep Bay Road
NSR 8	Village house at No. 30 Lau Fau Shan	2	255 m	245 m to New Road 24 m to Deep Bay Road
NSR 9	Planned residential development	2 - 3	55 m	50 m to New Road 5 m to Deep Bay Road
NSR 10*	Village house at No. 45A Hang Hau Tsuen	2	12 m	4 m to New Road

Note:

The location of the NSRs is shown in Figure 4.1.

* Tin-sheeted house, height not more than 5m.

4.5 Construction Noise Impact Assessment

Potential Sources of Impacts

4.5.1 The main construction activities for the proposed drainage channel include site clearance, excavation of channel to formation level, construction of channel linings, footbridges, concreting works, road surfacing works and landscaping works.

4.5.2 Dedicated haul road is not anticipated for the Project as access to the site is readily available from Deep Bay Road. The amount of associated construction traffic is considered negligible when compare with the existing traffic volume along Deep Bay Road.

4.5.3 Construction of the channel will generally be carried out starting from the downstream end to the upstream to facilitate simple draining of the works site. However, the Contractor may start at isolated sections to suit his allocation of resources and to maintain access across the channel banks.

4.5.4 Majority of the potential construction noise impact may occur during the site clearance and excavation works, when soil and stream bed sediments are excavated and transported out of the site. The construction of the Project includes construction of the channel, concreting works, road resurfacing works and landscaping works. Since the available works area is limited, the number of construction equipment will also be limited. Portion of the channel involves retaining sections of the stream bed and mangroves in-situ, as such construction activities is expected to be substantially scaled down. Similarly, the construction of maintenance access road and foot bridges will involve few mechanical equipment.

Construction Equipment

4.5.5 The type and quantity of Powered Mechanical Equipment (PME) likely to be used in each construction works described above and their Sound Power Level (SWL) are listed in Appendix 4.1. The works are standard civil engineering works and the equipment will be those typically found in similar drainage projects. It should be noted that this is an assumption of the most likely equipment to be used. The actual construction equipment will be determined by the Contractor performing the works.

4.5.6 The equipment used in the noise calculation was based on site experience and was reviewed by the design engineers. It was considered reasonable in terms of the types and numbers to be used by the Contractor for satisfactory completion of the Project based on the tentative construction programme, though there may be variation in the actual construction stage. A copy of CEDD’s memo acknowledging the proposed construction equipment is attached in Appendix 4.1.

Construction Schedule and Programme

4.5.7 The construction duration for this Project is expected to last for about 36 months within the tentative construction timeframe of end 2009 to end 2012. Currently, construction work during restricted hours is not anticipated.

Assessment Methodology and Assumptions

4.5.8 The construction noise assessment has been conducted based on standard acoustic principles. The methodology has made reference to the following:

§ Sections 5.3 & 5.4 of Annex 13 of the EIAO-TM;

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

§ BS 5228: Part 1: 1997 – Noise and Vibration Control on Construction and Open Sites, Part 1: Code of Practice for Basic Information and Procedures for Noise and Vibration Control (BS5228); and

§ EIAO Guidance Note No. 9/2004 – “Preparation of Construction Noise Impact Assessment under the Environmental Impact Assessment Ordinance”.

4.5.9 In general terms, the methodology used involves the following steps:

(i) identification of the most likely worst case scenario from the construction programme;

(ii) identification of the nearest representative NSRs to the work site;

(iii) calculation of the total Sound Power Level (SWL) of equipment to be used;

(iv) calculation of distance attenuation to NSRs from work site notional noise source point; and

(v) comparison of the Predicted Noise Levels (PNLs) with the relevant noise standards.

4.5.10 The assessment has been undertaken on the basis of the assumption that all construction equipment will be located on a notional noise source point (in accordance with the TM-GW) and is operating at the same time. The various construction activities are not expected to be carried out concurrently. Shielding effect from existing building structures, and/or topographic features have not been considered to simulate worst-case effect. A façade correction of +3 dB(A) is added to account for the sound reflection from the building’s surface of a NSR.

Assessment Results

4.5.11 The unmitigated PNL at the Representative NSRs are summarised below in Table 4.4. Detailed calculations are presented in Appendix 4.1.

Table 4.4

Predicted Noise Level during Construction of Hang Hau Tsuen Channel - Unmitigated

NSR	Unmitigated Construction Noise Level, dB(A)
NSR	Site Clearance	Excavation to Formation Level	Construction of Channel Lining, Crossings and other Works	Concreting Works	Road Surfacing Works	Landscaping and Finishing Works
NSR 1*	77	77	78	77	77	77
NSR 2	89	89	90	88	88	89
NSR 3	90	90	91	90	90	90
NSR 4	90	90	91	90	90	90
NSR 5	89	89	90	89	89	89
NSR 6	90	90	92	90	90	90
NSR 7	69	69	70	69	69	69
NSR 8	65	65	66	65	65	65
NSR 9	78	78	80	78	78	78
NSR 10	92	92	93	91	91	92

Notes:

Numbers in BOLD denote exceedance of daytime noise standard: 75 dB(A) for residential premises, 70 dB(A) for educational institution.

* Wing Jan Kindergarten (noise standard during examination not applicable)

4.5.12 Table 4.4 shows that unmitigated construction noise levels would exceed the daytime noise standards at most of the Representative NSRs at Hang Hau Tsuen. The predicted exceedance is due to the close proximity of the construction works to the NSRs. However, the likely overall exceedance with respect to each receiver is expected to be intermittent and not severe, as some part of the works would be carried out within the channel where the noise would be partially shielded. Moreover, as the available works area for the channel, pipes or box culvert are limited, the use of heavy construction machinery will be limited. Nonetheless, adequate mitigation measures will be required. The recommended mitigation measures for the construction works are discussed in the subsequent section.

4.6 Operational Noise Impact Assessment

Introduction

4.6.1 Potential noise impacts during operational phase of the Project are identified as follow:

· Road traffic noise from the proposed access road along the northern channel bank (which will be open for public use); and

· Noise from mechanical equipment during the routine maintenance of the proposed channel.

Road Traffic Noise

4.6.2 The aim of this assessment is to quantify by computer modelling the traffic noise impact from the existing surrounding roads and the proposed access road (Road A) along the northern channel bank on the representative NSRs within a 15 years period upon the commencement of the operation of the Project. The location of the proposed access road (Road A) is shown in Figure 4.1.

Assessment Criteria

4.6.3 Road traffic noise criteria used in this assessment are in accordance with the standards listed in Table 1A of Annex 5 of the EIAO-TM. The peak noise level from road traffic, measured in terms of L_{10 (1‑hr)} is 70 dB(A) at domestic premises and 65 dB(A) at educational institutions. The peak noise level criterion of 55 dB(A) in L_{10 (1‑hr)} is considered not applicable to the current assessment as no NSRs of the related uses were identified in the vicinity of the Project area.

4.6.4 Putting these criteria into the current assessment, the maximum predicted noise levels due to traffic on surrounding roads in terms of hourly L₁₀ should not exceed 70 dB(A) for NSR 2 to NSR 10, and should not exceed 65 dB(A) for NSR 1.

Assessment Methodology

4.6.5 An in-house developed computer model based on the U.K. Department of Transport's procedure "Calculation of Road Traffic Noise" (CRTN) was used to predict the hourly L₁₀ levels at typical facades of NSRs near the subject site. Peak hour traffic forecast on the existing nearby roads and the proposed access road (Road A) for the year 2027 were used for the study (Appendix 4.2).

4.6.6 In order to assess the additional operational traffic noise impact brought by the proposed access road (Road A) on the nearby noise sensitive receivers, the same computer model was employed to assess the traffic noise impact in the year 2027 without the Project. Peak hour traffic data on the existing nearby roads for the year 2027 without the Project were used for this purpose (Appendix 4.2).

Noise Sensitive Receivers

4.6.7 The representative noise sensitive receivers are identified in Table 4.3 above. Each of the NSRs has at least one assessment point located on the facade that is most affected by the traffic noise from the nearby roads. Subject to the orientation of the NSRs and their distances to the nearby roads, some of the NSRs have two or more assessment points on different facades. For NSR 1 and NSR 2, three assessment points were placed while for NSR 3, NSRs 5 to 8 and NSR 10, two assessment points were selected for each of them. For the planned NSR 9, four assessment points were placed. Location of the assessment points are shown in Appendix 4.2.

4.6.8 Some of the NSRs such as NSR 3, NSRs 5 to 10 are of multi-storeys. All assessment points were taken at 1.2 m above floor slabs and at 1 m away from the external facade of the building of the sensitive receivers. The mPD levels of each floor of the NSRs are tabulated below.

Table 4.5

Floor Levels of the NSRs

Floor Levels	NSRs
Floor Levels	NSR1	NSR2	NSR3	NSR4	NSR5	NSR6	NSR7	NSR8	NSR9	NSR10
1/F	13.4	4.0	3.0	2.8	2.8	2.8	5.3	4.2	5.5	2.8
2/F	--	--	5.5	--	5.3	5.6	8.3	6.7	8.5	5.3
3/F	--	--	--	--	--	--	11.3	--	11.5	--

Road Characteristics

4.6.9 The road sections that are within a distance of 300 m from the representative NSRs are considered in the model of this assessment. To simulate the worst case scenario, all the road sections in the model are assumed to be impervious with speed limit of 50 km/hr.

4.6.10 The proposed access road, Road A, will be connected to a viewing point with 8-9 numbers of parking spaces. It was assumed that the parking period for each vehicle at the parking space is half an hour at peak hour. As Road A is proposed to be a single two-ways road, it was therefore predicted that the peak traffic flow of Road A is 50 vehicles per hour. Vehicles longer than 7 m will be restricted from using the access road, hence a minimal 10% heavy vehicles are expected.

4.6.11 The traffic forecast in 2027 with and without the Project for the roads identified for this assessment are tabulated in Table 4.6 and Table 4.7 below. The location of the road network is shown in Appendix 4.2. A copy of Transport Department (TD) memo expressing no comments on the forecast traffic flow is included in Appendix 4.2.

Table 4.6

Traffic Forecast in 2027 with the Project

Road Name	Traffic Volume (veh/hr)	% of Passenger Vehicle	% of Heavy Vehicles	Speed (km/hr)	Road Surface
Proposed access road (Road A)	50	90	10	50	Impervious
Deep Bay Road (N1/S1)	255	49	51	50	Impervious
Deep Bay Road (N3/S3)	129	41	59	50	Impervious
Lau Fau Shan Road (N2/S2)	454	45	55	50	Impervious
Access road to Lau Fau Shan Police Station (N4/S4)	41	39	61	50	Impervious

Notes:

* Vehicles longer than 7m will be restricted from using the proposed access road.

Table 4.7

Traffic Flow Data in 2027 without the Project

Road Name	Traffic Volume (veh/hr)	% of Passenger Vehicle	% of Heavy Vehicles	Speed (km/hr)	Road Surface
Deep Bay Road (N1/S1)	205	39	61	50	Impervious
Deep Bay Road (N3/S3)	129	41	59	50	Impervious
Lau Fau Shan Road (N2/S2)	404	39	61	50	Impervious
Access road to Lau Fau Shan Police Station (N4/S4)	41	39	61	50	Impervious

Assessment Results

4.6.12 The predicted hourly L₁₀ _(1hour) dB(A) at the assessment points of the representative NSRs are tabulated in Table 4.8 to Table 4.10 below.

Table 4.8

Predicted Hourly Traffic Noise Level L₁₀at the Assessment Points of Representative NSRs in 2027 with the Project

NSR	Assessment Point	Predicted Hourly Traffic Noise Level (L_{10 (1 hour)}, dB(A))
NSR	Assessment Point	G/F	1/F	2/F
NSR 1*	N1A	64	-	-
	N1B	67	-	-
	N1C	58	-	-
NSR 2	N2A	67	-	-
	N2B	67	-	-
	N2C	64	-	-
NSR 3	N3A	63	63	-
NSR 3	N3B	63	63	-
NSR 4	N4	62	-	-
NSR 5	N5A	57	57	-
NSR 5	N5B	58	58	-
NSR 6	N6A	59	59	-
NSR 6	N6B	57	57	-
NSR 7	N7A	68	68	68
NSR 7	N7B	67	67	67
NSR 8	N8A	70	70	-
NSR 8	N8B	71	71	-
NSR 9	N9A	68	68	68
	N9B	64	64	64
	N9C	60	60	60
	N9D	60	60	61
NSR 10	N10A	61	61	-
NSR 10	N10B	62	62	-

* Wing Jan Kindergarten

Table 4.9

Predicted Hourly Traffic Noise Level L₁₀at the Assessment Points of Representative NSRs in 2027 without the Project

NSR	Assessment Point	Predicted Hourly Traffic Noise Level (L_{10 (1 hour)}, dB(A))
NSR	Assessment Point	G/F	1/F	2/F
NSR 1*	N1A	64	-	-
	N1B	67	-	-
	N1C	58	-	-
NSR 2	N2A	67	-	-
	N2B	67	-	-
	N2C	63	-	-
NSR 3	N3A	62	62	-
NSR 3	N3B	61	61	-
NSR 4	N4	59	-	-
NSR 5	N5A	54	54	-
NSR 5	N5B	55	55	-
NSR 6	N6A	58	58	-
NSR 6	N6B	53	53	-
NSR 7	N7A	67	67	67
NSR 7	N7B	67	67	67
NSR 8	N8A	70	70	-
NSR 8	N8B	71	71	-
NSR 9	N9A	67	67	67
	N9B	63	63	63
	N9C	58	58	59
	N9D	60	60	60
NSR 10	N10A	57	57	-
NSR 10	N10B	57	57	-

* Wing Jan Kindergarten

Table 4.10

Maximum Predicted Hourly Traffic Noise Level L₁₀at the Representative NSRs in 2027

NSR	Floor	Maximum Predicted Road Traffic Noise Level, L_{10 (1 hour)}, dB(A)
NSR	Floor	With Project	Without Project	Difference
NSR 1*	G/F	67	67	0
NSR 2	G/F	67	67	0
NSR 3	G/F	63	62	1
NSR 3	1/F	63	62	1
NSR 4	G/F	62	59	3
NSR 5	G/F	58	55	3
NSR 5	1/F	58	55	3
NSR 6	G/F	59	58	1
NSR 6	1/F	59	58	1
NSR 7	G/F	68	67	1
	1/F	68	67	1
	2/F	68	67	1
NSR 8	G/F	71	71	0
NSR 8	1/F	71	71	0
NSR 9	G/F	68	67	1
	1/F	68	67	1
	2/F	68	67	1
NSR 10	G/F	62	57	5
NSR 10	1/F	62	57	5

* Wing Jan Kindergarten

4.6.13 According to the predicted traffic noise level as tabulated in Table 4.8 and Table 4.10, the maximum predicted noise level in the year 2027 with the Project at the majority of the noise sensitivity receiver is within the traffic noise criterion of 70 dB(A) for residential and 65 dB(A) for school while the predicted noise level at the NSR 8B exceed the residential criterion by 1 dB(A) and that at the NSR 1B exceed the school criterion by 2 dB(A). However, as shown in Table 4.9 and Table 4.10, there will be no increase of the predicted traffic noise at these two NSRs with and without the Project. This shows that these two NSRs will not experience any significant additional noise after the operation of the proposed access road (Road A).

4.6.14 By comparing the predicted traffic noise levels upon the other representative NSRs in the year 2027 with and without the Project (Tables 4.8 to 4.10), some of the representative NSRs would experience an increase in traffic noise level by more than 1 dB(A). This additional traffic noise impact due to the operation of the proposed access road (Road A) would be mostly on the representative NSRs along Road A, namely NSR 3, NSR 4, NSR 5, NSR 6 and NSR 10. Nevertheless, the predicted traffic noise levels on these NSRs were still well within the criterion of 70 dB(A).

4.6.15 Therefore, for most of the NSRs, the predicted maximum traffic noise levels in 2027 with and without the Project will be the same or with the differences not more than 1 dB(A) and will still be within the relevant traffic noise criteria (except NSRs N8B and N1B which has been explained in Section 4.6.13 above). In conclusion, no adverse traffic noise impact would be brought by the operation of the Project to the nearby NSRs.

Maintenance of the Channel

4.6.16 Maintenance would be necessary for the proposed channel to remove excessive silts, vegetation, debris and obstructions in order to maintain its hydraulic performance and structural integrity. Siltation will generally be allowed to accumulate and removal of excess silt would be carried out at locations where it would impede water flow. Such small scale maintenance would require only light mechanical equipment such as a small loader and/or a small crane truck. Hand-held equipment will be used for vegetation removal. Little or no maintenance will be necessary for the natural stream bed section of the proposed channel. Therefore the operational phase of this Project (in terms of maintenance of the channel) would unlikely cause any adverse noise impact.

4.7 Mitigation Measures

Construction Phase

4.7.1 The predicted noise levels showed that construction works would give rise to daytime noise impacts to most of the Representative NSRs. The following types of mitigation measures are recommended.

Level 1 Mitigation - Use of Quiet Plant

4.7.2 The use of quiet plant (also referred as silenced equipment) can provide significant reduction in noise level. Quiet plant is defined as PME whose actual sound power level is less than the value specified in the TM-GW for the same piece of equipment. The common source of these information is from international standard / certification, e.g. BS 5228. To allow the Contractor some flexibility to select equipment to suit actual needs, it is considered too restrictive to specify which specified silenced equipment to be used for the construction works. Hence, it is preferable and practical to specify the noise performance specification of the plant on site in terms of the sound power level so that the Contractor is allowed some flexibility. It should be noted that various types of silenced equipment can be found in Hong Kong and are readily available on the market. The quiet plant used in the construction noise calculation is shown in Table 4.11 and Appendix 4.1. The Contractor can propose other suitable alternative equipment with similar or lower sound power level.

4.7.3 The use of quiet plant is considered to be the most effective ways of alleviating construction noise impact. The Contractor should use quiet plant with sound power level lower than that stipulated in the TM-GW as the Level 1 mitigation for construction noise.

4.7.4 The use of mini or lower power rating equipment (e.g. mini excavator) should also be considered where practical. This technique would be feasible and practical at some locations given the limited space available for using large size construction equipment and the small scale works involved.

4.7.5 The Contractor should take note of ETWB TCW No. 19/2005 – “Environmental Management on Construction Sites” which sets out the policy and procedures requiring contractors to, among others, adopt Quality Powered Mechanical Equipment (QPME)[1].

4.7.6 A list of quiet powered mechanical equipment (PME) recommended for use during construction phase is tabulated below in Table 4.11.

Table 4.11

Quiet Powered Mechanical Equipment Recommended for Use during Construction Phase

Powered Mechanical Equipment	Power Rating / Size, Weight	Reference	SWL, dB(A)
Excavator, loader	52 kW	BS5228 C.3-97	105
Dump truck	450 kW, 50 t	BS5228 C.9-39	103
Crane	62 kW	BS5228 C.7-114	101
Vibratory roller	9 kW	BS5228 C.3-115	102
Concrete lorry mixer	22 kW, 6 m³	BS5228 C.6-23	100
Vibratory poker	2 kW	BS5228 C.6-32	100
Asphalt paver / spreader	90 kW, 13 t	BS5228 C.8-24	101
Road roller	10 t	BS5228 C.8-25	96

4.7.7 With the use of quiet plant, most of the Representative NSRs still exceed the noise standard and will still require further mitigation measures.

Level 2 Mitigation - Use of Temporary Noise Barriers

4.7.8 Since most of the NSRs within the Project area are typically low-rise tin-sheeted village houses of not more than 2 storeys (all are less than 5 m tall), it would be effective to have noise screening structures or temporary noise barriers purposely-built along the site boundary to provide additional protection to NSRs close to the construction site boundary. This could be in the form of purposely-built site hoarding constructed from appropriate materials with a minimum superficial density of 7 kg/m². Noise barrier should be provided for noisy construction activities that would be undertaken close (about 30 m or less) to NSRs. The noise barrier should have a vertical height of at least 3 m or (depending on the height of the NSRs to be protected) a height ensuring that the operating equipment can be shielded from the view of the NSRs. The temporary noise barrier should have no gaps or opening at joints. The Contractor should regularly inspect and maintain the noise barrier to ensure its effectiveness.

4.7.9 For the construction works which have the potential to exceed the noise standards on nearby NSR and whose line of sight cannot be effectively blocked by the temporary noise barrier, movable (mobile) barriers should be provided. This may also be applicable in situation where construction of a temporary noise barrier may not be possible due to site / space constraints, for example blocking village or emergency vehicle access. Movable barriers of at least 2.5 m height with a small cantilevered upper portion and skid footing can be located within a few meters of stationary plant (e.g. generator) and within about 5 m or more of a mobile equipment (e.g. excavator), such that the line of sight to the NSR is blocked by the barriers.

4.7.10 With the shielding effect provided by the proposed temporary noise barriers and/or mobile barriers, noise reduction of 10 dB(A) and 5 dB(A) is expected for stationary equipment and mobile equipment respectively.

4.7.11 The proposed noise barrier for the affected Representative NSRs is shown in Figure 4.2. A typical cross section view of the barrier showing line of sight could be shielded by the proposed barrier is included in Appendix 4.1.

Good Site Practices

4.7.12 In general, potential construction noise impact can be minimised or avoided by imposing a combination of the following good site practices as mitigation measures:

(a) Only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction period.

(b) Construction plant should be sited away from NSRs.

(c) Machines and plant that may be in intermittent use should be shut down between works periods or should be throttled down to a minimum.

(d) Equipment known to emit sound strongly in one direction should be orientated such that the noise is directed away from nearby NSRs.

(e) Material stockpiles and other structures (such as site offices) should be effectively utilised to shield on-site construction activities.

(f) Stationary equipment should be located within the channel when weather conditions permit (e.g. dry season).

(g) The Contractor shall devise, arrange methods of working and carrying out the works in such manner as to minimise noise impacts on the surrounding environment, and shall provide experienced personnel with suitable training to ensure that these measures are implemented properly.

(h) In the event that new schools are built near the works area, the Contractor should minimise construction noise exposure to the schools (especially during examination periods). The Contractor should liaise with the school and the Examination Authority to ascertain the exact dates and times of all examination periods during the course of the contract and to avoid noisy activities during these periods.

4.7.13 The implementation of the above good site practices could be readily applied to construction sites and can, in theory, provide additional reduction in construction noise levels. However, such noise reduction is difficult to quantify and is therefore not considered in the calculations.

Public Relation Strategy

4.7.14 Having a good public relation with the local communities during the construction phase is indispensable for a smooth implementation of the Project. Prior to commencement of the construction, visits to the affected villages, local communities and property owners should be carried out. The purpose of the visits is to advise the public the following information in relation to the Project:

· the implementation programme of the works;

· the planned construction activities that will be involved;

· the possible impacts arising from the works;

· the measures to avoid or mitigate any adverse impacts;

· the monitoring programme to check the efficiency of the measures; and

· the communication channels between the local communities and the project office.

4.7.15 To maintain an effective communication channel with the public, a 24-hour hotline system should be established by the project office for the Contractor to receive any enquiry and complaint lodged by the public in respect of the Project. Upon receipt of enquiry / complaint, the Contractor (or its Environmental Team) should investigate the causes of the incident and take the appropriate action to rectify the situation. Periodic newsletters, information leaflets, notices or other means of communication should be provided to the affected villages, communities, and residents advising them the current progress, the schedule of works in future, the potential environmental impacts arising from the works and the corresponding mitigation measures. It is considered that such a close relation between the local communities and the project site office could ensure speedy resolution of any environmental non-compliance and maintain an environmental standard acceptable to the local communities during construction.

4.7.16 Table 4.12 shows the predicted noise levels with the implementation of the proposed Level 1 mitigation measure (use of quiet plant).

Table 4.12

Predicted Noise Level during Construction of Hang Hau Tsuen Channel - Mitigated

(Level 1 mitigation : use of quiet plant)

NSR	Mitigated Construction Noise Level, dB(A)
NSR	Site Clearance	Excavation to Formation Level	Construction of Channel Lining, Crossings and other Works	Concreting Works	Road Surfacing Works	Landscaping and Finishing Works
NSR 1*	66	66	68	65	64	66
NSR 2	77	78	80	77	76	77
NSR 3	79	79	81	78	77	79
NSR 4	79	79	81	78	77	79
NSR 5	78	78	80	77	77	78
NSR 6	79	80	81	79	78	79
NSR 7	58	58	60	57	56	58
NSR 8	54	54	56	53	52	54
NSR 9	67	68	69	67	66	67
NSR 10	80	81	83	80	79	80

Notes:

Numbers in BOLD denote exceedance of daytime noise standard: 75 dB(A) for residential premises, 70 dB(A) for educational institution.

* Wing Jan Kindergarten (noise standard during examination not applicable)

4.7.17 Table 4.13 shows the predicted noise levels with the implementation of the proposed Level 2 mitigation measures (use of quiet plant + temporary noise barrier) for the affected Representative NSRs (NSRs 2, 3, 4, 5, 6 & 10).

Table 4.13

Predicted Noise Level during Construction of Hang Hau Tsuen Channel - Mitigated

(Level 2 mitigation : use of quiet plant + use of noise barriers)

NSR	Mitigated Construction Noise Level, dB(A)
NSR	Site Clearance	Excavation to Formation Level	Construction of Channel Lining, Crossings and other Works	Concreting Works	Road Surfacing Works	Landscaping and Finishing Works
NSR 2	72	73	74	72	71	72
NSR 3	74	74	76	73	72	74
NSR 4	74	74	76	73	72	74
NSR 5	73	73	75	72	72	73
NSR 6	74	74	76	73	73	74
NSR 10	75	76	77	75	74	75

Notes:

Numbers in BOLD denote exceedance of daytime noise standard: 75 dB(A) for residential premises, 70 dB(A) for educational institution.

4.7.18 Although the proposed temporary noise barrier and mobile barrier can shield the view of NSRs 3, 4, 6 & 10 to the construction site (see Figure 1 of Appendix 4.1), there would be slight marginal exceedance of about 1-2 dB(A) as shown in Table 4.13 due to the close proximity of these NSRs to the works. Further mitigation is recommended for NSRs 3, 4, 6 & 10 by restricting concurrent usage of several equipment at the same time during excavation and construction of the channel lining, crossings. As demonstrated in Appendix 4.1, with the restriction of current usage of equipment, noise level will be within the daytime construction noise standard. Such restriction is considered feasible and would not hinder the overall progress of the construction works. It should be noted that similar noise reduction can be expected with the implementation of good site practices. It is also recommended that at least one of these NSRs be included in the EM&A programme during construction period to monitor the noise level and effectiveness of the mitigation measures.

Summary of Construction Phase Mitigation Measures

4.7.19 Table 4.14 summarises the mitigation measures proposed for the construction works. All these construction noise mitigation measures should be implemented by the Contractor during the construction phase of the works. The location of the temporary noise barriers and mobile noise barriers should be further reviewed by the Contractor during the construction stage based on the latest construction programme and contemporary conditions, including any changes with respect to NSRs. The Contractor should design, construct, operate and maintain the mitigation measures throughout the construction phase and as required by the Engineer. Before commencement of the works, the Contractor should submit to the Engineer for approval (as part of their method statement) details of the mitigation measures to be employed under the works. The Contractor’s proposed mitigation measures should also be certified by the Environmental Team (ET) Leader and verified by the Independent Environmental Checker (IEC) to ensure the intended noise reduction effectiveness can be achieved.

Table 4.14

Summary of Proposed Construction Noise Mitigation Measures

Proposed Mitigation Measures	Location	Timing / Duration	Implementation Agent	Specific Requirements
Use of quiet equipment including QPME	All construction works / sites	During the construction period	Contractor	Some examples of quiet plant and QPME are shown in *Table 4.11*. Contractor can propose other suitable alternative equipment with similar or lower sound power level.
Use of temporary noise barrier (purpose-built site hoarding) and/or movable (mobile) noise barrier	The temporary noise barrier shall be located as per *Figure 4.2* or wherever noisy construction works are being carried out close (30m or less) to NSRs	During the construction period	Contractor	Barriers should be of at least 3 m high or able to shield construction equipment from NSR’s view. These barriers should be constructed of appropriate material with a minimum superficial density of 7 kg/m², with no gaps or openings. Also, regular inspection and maintenance should be carried out. Where barriers cannot block line of sight, mobile barrier of 2.5 m high with a cantilevered upper portion should be provided.
Good site practices	All construction works / sites	During the construction period	Contractor	-----
Public relation strategy	All construction works / sites	During the construction period	Project office (Engineer) / Contractor	Maintain a 24-hour hotline for enquiry and complaint, periodic communication with affected parties.
Restrict concurrent usage of several construction equipment at the same time	For construction works in close proximity to NSRs 3, 4, 6 &10	During the construction period	Contractor	Contractor to propose details or other suitable alternatives to the Engineer and ET Leader for approval.

Operational Phase

4.7.20 As no adverse noise impact is identified during operational phase, no specific mitigation measure is necessary.

4.8 Residual Impact

4.8.1 With the implementation of proposed mitigation measures, adverse residual noise impact would not be expected from the construction works.

4.9 Cumulative Impact

4.9.1 As indicated in Section 2.9, there is a potential concurrent project within the Study Area. Based on the best available information, this project involves the construction of a sewage pumping station near NSR7. Since no information regarding the concurrent project construction activities or noise assessment is available at the time of the EIA study, reference has been made to construction noise assessment for other similar sewage pumping station project approved under the EIAO.

4.9.2 The cumulative construction noise impact as a result of the proposed Project and the concurrent project on some of the likely worst affected NSRs is shown in Appendix 4.1. Given the distance separation between the concurrent project and the NSRs, no adverse cumulative noise impact is expected during construction.

4.10 Monitoring and Audit Requirements

4.10.1 Further information regarding construction noise monitoring and audit are broadly described in Chapter 10 of this Report. Key points are summarized in the following sections. Details of the monitoring and audit of construction noise will be presented in the separate EM&A Manual.

4.10.2 Noise monitoring should be carried out at selected representative NSRs during the construction period to check for compliance with permissible noise standards, and to verify the effectiveness of the recommended mitigation measures. Ad-hoc monitoring and audit should also be carried out at other NSRs if complaints are received. Measures should be taken by the Contractor to ensure compliance with the noise standards.

4.10.3 It is recommended that at least the following representative NSRs (Table 4.15) should be monitored during the construction phase. The representative sensitive receivers have been selected for monitoring to represent a particular area likely to be most affected by the construction works of this Project.

4.10.4 As the predicted road traffic noise is within the EIAO-TM noise standard, no monitoring is required during operational phase.

Table 4.15

Representative NSRs chosen for Noise Monitoring during Construction Phase

Noise Monitoring Station	NSR ID	General Description
N1	NSR 1	Wing Jan Kindergarten
N2	NSR 3	Village house at No. 84 Hang Hau Tsuen
N3	NSR 6	Village house at No. 88 Hang Hau Tsuen

Notes:

Subject to the location of the construction works and to be proposed by the ET Leader.

4.11 Summary

4.11.1 The use of powered mechanical equipment during the construction phase of this drainage project is expected to create noise nuisance, due to the close proximity between the works areas and noise sensitive receivers. Assessment indicates that such noise impacts can be mitigated to acceptable levels by appropriate measures, such as the use of quiet plant, temporary noise barriers, restricting concurrent usage of equipment and the implementation of good site practices. The Contractor will be required to implement these measures when powered mechanical equipment is used during the construction phase. With these measures in place, residual noise impact would not be expected from the construction works and will comply with the EIAO-TM daytime construction noise standard.

4.11.2 Noise monitoring is recommended at selected noise sensitive receivers during the construction period to check for compliance with permissible noise levels and effectiveness of the proposed mitigation measures.

4.11.3 The operation phase of the Project, in terms of road traffic noise and during maintenance of the channel, is not expected to pose any noise impact to the surrounding noise sensitive receivers.

[1] QPME are construction plant and equipment that are notably quieter, more environmentally friendly and efficient. EPD has developed a system for the registration of QPME that are used in Hong Kong. A label will be issued by EPD for those plant and equipment that have been registered under the system.