4 COnstruction NOISE impact

4.1 Introduction

4.1.1 This section presents an assessment of the potential noise impact during the construction phase of the proposed drainage improvement works.

4.1.2 Noise impacts during the construction phase would be mainly associated with the construction activities and the use of powered mechanical equipment (PME) for construction work. Appropriate mitigation measures have been recommended, where necessary, to alleviate the potential noise impacts to acceptable levels.

4.2 Environmental Legislation, Policies, Plans, Standards and Criteria

4.2.1 Noise impacts were assessed in accordance with the criteria and methodology given in the Technical Memoranda (TM) made under the Noise Control Ordinance (NCO) and the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) under the Environmental Impact Assessment Ordinance (EIAO).

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

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

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

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

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

4.2.3 Under the GW-TM, noise from construction activitiesy is not restricted during the period 0700 - 1900 hours on weekdays, except Public Holidays. However, the EIAO-TM identifies a daytime general construction noise limit of 75 dB(A) _{Leq (30 minutes)} for domestic premises and Leq(30min) 70dB(A)_Leq(30min) for schools during normal hours (65dB(A) during examination) and all others where unaided voice communication is required. Theseis standards wereas used as assessment criteria in the construction noise assessment during daytime.

4.2.4 Between 1900 and 0700 hours and all day on Sundays and public holidays, activities involving the use of powered mechanical equipment (PME) for the purpose of carrying out construction work is prohibited unless a Construction Noise Permit (CNP) has been obtained. A CNP may be granted provided that the Acceptable Noise Level (ANL) for the noise sensitive receivers (NSRs) can be complied with. ANLs are assigned depending upon the Area Sensitive Rating (ASRs). The corresponding basic noise levels (BNLs) for evening and night-time periods are given in Table 4.1.

Table 4.1 Construction Noise Criteria for Activity other than Percussive Piling

Time Period	Basic Noise Level (BNLs) (dB(A))
Time Period	ASR A	ASR B	ASR C
Evening (1900 to 2300 hours) ⁽¹⁾	60	65	70
Night (2300 to 0700 hours)	45	50	55

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

4.2.5 According to the preliminary construction programme, all the proposed construction works would be carried out during non-restricted hours. In case of any construction activities during restricted hours, it is the Contractor’s responsibility to ensure compliance with the NCO and the relevant TMs. The Contractor will be required to submit CNP application to the Noise Control Authority and abide by any conditions stated in the CNP, should one be issued.

4.2.6 Based on the preliminary design information, percussive piling would not be adopted for the proposed Project. Therefore, noise criteria as stipulated in the PP-TM would not be applicable to this Project.

4.2.7 For the noise impacts associated with the construction of the proposed Project, they would primarily be assessed against the noise criteria set out in Table 1B of Annex 5 of the EIAO-TM.

4.3 Description of the Environment

4.3.1 The proposed drainage improvement works will be divided into three sections at Sha Ha, Pak Kong and Ho Chung, which are located at the coastal lowland along Inner Port Shelter and Hebe Haven. The ambient noise levels in the vicinity of each river are discussed as follows:

Sai Kung River and Sha Ha Diversion Culvert

4.3.2 The western section of the proposed alignment is a typical rural quiet rural environment comprising Sai Kung River and agricultural land. The background noise in the vicinity of the proposed alignment is dominated by Tai Mong Tsai Road and some local access roads. The ambient noise level is expected to be low to moderate.

Pak Kong River

4.3.3 The proposed alignment is surrounded by village houses and agricultural land. It runs almost in parallel to Hiram’s Highway. Road tTraffic noise arising from Hiram’s Highway contributes significantly to the ambient noise level. The ambient noise level is expected to be moderate.

Ho Chung Channel

4.3.4 The proposed alignment is adjacent to Ho Chung Road. Mini-buses and private cars are the major transport modes for the villagers using this road. Hiram’s Highway crosses the proposed alignment. The ambient noise level is expected to be moderate to moderate-high, and which is primarily affected by traffic noise from Ho Chung Road, Hiram’s Highway and local access roads.

4.4 Noise Sensitive Receivers

4.4.1 For the purpose of noise impact assessment, NSRs within 300 m from the proposed site boundary were identified and shown in Figures 4.1 to 4.3. Representative NSRs within the 300m study area close to the Project site were selected in accordance with the criteria in the EIAO-TM to evaluate the potential noise impacts. Table 4.2 summarises the selected NSRs for the noise impact assessment. The locations of representative NSRsin the vicinity of Sai Kung River, Pak Kong River and Ho Chung Channel are are shown in Figures 4.4 to 4.6, respectively.

Table 4.2 Summary of Identified Noise Sensitive Receivers

NSR	Location	~~Use~~ Landuse
Sai Kung River and Sha Ha Diversion Culvert
SK1	No. 68, Sha Kok Mei	Residential
SK2	No. 19, Village house adjacent to Hang Cho Shui	Residential
SK3	No. 23, Muk Min Shan	Residential
SK4	No. 21, Muk Min Shan	Residential
SK5	No. 13, Muk Min Shan	Residential
SK6	No. 1, Muk Min Shan	Residential
SK7	Mr. & Mrs. Jimmy Shaw	Residential
SK8	No. 1, Builingame Garden	Residential
Pak Kong River
PK1	Village House along Hiram’s Highway	Residential
PK2	No. 3, Village House along Hiram’s Highway	Residential
PK3	No. 14, Village House, Tai Chung Hau	Residential
PK4	No. 42, Village House, Tai Chung Hau	Residential
PK5	No. 23, Village House, along Tai Chung Hau Road	Residential
Ho Chung Channel
HC1	No. 30, Ho Chung	Residential
HC2	No. 27, Ho Chung First Lane	Residential
HC3	No. 5B, Ho Chung	Residential
HC4	No. 107, Ho Chung New Village	Residential
HC5	No. 116, Ho Chung New Village	Residential
HC6	Village House adjacent to Rural Committee	Residential
HC7	Berkeley Bay Villa House 18	Residential
HCT1	Che Kung Temple	~~Places of Public Worship~~Institutional
HCSC1	Sai Kung Central Primary School	Educational

4.5 Assessment Methodology & Criteria

4.5.1 The methodology outlined in the TM on Noise from Construction Works other than Percussive Piling (GW-TM) was used for the assessment of construction noise. Notional noise sources for different construction areas were assumed in accordance with this TM. All items of powered mechanical equipment (PME) were assumed to be located at these notional source positions.

4.5.2 Sound power levels (SWLs) of PME were taken from Table 3 of the GW-TM. Where no sound power level (SWL) was given in the GW-TM, reference was made to the British Standards BS5228: Part 1:1997 Noise Control on Construction and Open Sites.

4.1.1 Since machinery equipment would not be fully operated in practice, reasonable assumptions for on-time percentage of certain PME were adoptedder to provide more realistic calculations of the construction noise levels. The assumed on-time percentage for PME are summarised in Table 4.3., the reasonable assumptions for on-time percentage of certain PME were adopted.

4.5.3 Since machinery equipment would not be fully operated in practice, appropriate on-time percentage for some items of PME are assumed and summarised in Table 4.3.

Table 4.3 On-time Percentage Assumptions for Certain Items of PME

PME	Assumed on–time %
Excavator	80%
Dump truck	70%
Loader	80%
Crane	70%
Concrete lorry mixer	70%
Vibratory poker	70%

4.5.4 As agreed by the Engineer, the assumptions of on-time percentage and the number of PME are typical and expected to be practical in completing the works within the schedule.

4.5.5 Based on the above assumptions, the total SWL for each construction activities were calculated and summarised in Appendix 4.1.

4.5.6 The assessment was based on the cumulative SWL of PME likely to be used for each location, taking into account the construction period in the vicinity of the receiver location. To predict the noise level, PME was divided into groups required for each discrete construction task. The objective was to identify the worst-case scenario representing those items of PME that would be in use concurrently at any given time. The sound pressure level (SPL) of each construction task at NSRs was calculated, depending on (1)the number of plants, (2)their frequency of operation, and (3)their distance from receivers. The noise levels at NSRs were then predicted by adding up the SPLsound pressure level of all concurrently construction tasks.

4.5.7 According to Section 2.11 of the TM on Noise from Construction Works other than Percussive Piling, a positive correction of 3 dB(A) for acoustic reflection was applied to the predicted noise level when the NSR was a building.

4.5.8 Construction tasks, within 300m of a given NSR at the same period, were considered to contribute to the cumulative impact at that NSR. Noise sources from the areas greater than this distance were excluded from the assessment.

4.5.9 Based on the available current information, the following projects would likely be carried out concurrently with the proposed Project.

Table 4.4 Concurrent Projects

Work Area	Project
Sai Kung River	Dualling of Hiram’s Highway from Marina Cove to Sai Kung Town
Pak Kong River	Dualling of Hiram’s Highway from Marina Cove to Sai Kung Town
Ho Chung Channel	Dualling of Hiram’s Highway between Clear Water Bay Road and Marine Cove and Improvement to Local Access to Ho Chung
	Improvement of Ho Chung Road

4.5.10 “Dualling of Hiram’s Highway from Marina Cove to Sai Kung Town” and “Dualling of Hiram’s Highway between Clear Water Bay Road and Marine Cove and Improvement to Local Access to Ho Chung” by Highways Department could be the projects near the site, but the implementation and programme of the projects are still subject to the review by the Highways Department. There were no details of construction programme and plant inventory available. Thus, the projects were not included in the cumulative construction impact assessment.

4.5.11 “Improvement of Ho Chung Road” is tentatively scheduled to commence in March 2005 and for completion incomplete in September 2006. It is likely to be undertaken concurrently with the proposed Project. For the purpose of this EIA Study, an indicative assessment of cumulative construction noise impact had been carried out and presented in Sections 4.8.12 - 4.8.14.

4.6 Identification of Environmental Impacts

4.6.1 The potential source of noise impact during the construction phase of the Project would be the use of PME for various construction activities. As indicated in the preliminary construction programme shown in (Figure 2.1 refers), the proposed Project lasts from December 2005 to April 2008. Construction tThe construction tasks for the proposed drainage works are summarised in Table 4.5 below:

Table 4.5 Summary of Construction Tasks for the Proposed Drainage Works

Construction Tasks	Construction Sub-tasks
Site Clearance	-
Channel Construction	Excavation
Box Culvert / Bridge	Sheetpiling
	Earthworks
	Reinforcement Fixing / Concrete operations
	Backfilling
Backfilling / Channel lining	-
Retaining Wall	-
Flood Wall	-
Weir System	-
Bored Piling Work	Bored Piling
	Reinforcement Fixing / Concrete Operations

4.6.2 The proposed drainage works would mostly be carried out within a linear and narrow construction site. Construction equipment and activities would be moving along the channel sections as the construction work proceeds. Since some of the NSRssensitive receivers were identified in close proximity to the proposed work sites, adverse noise impacts due to the use of PME would likely be found at these receivers if no appropriate noise control measures are implemented during the construction stage of the proposed Project.

4.7 Prediction and Evaluation of Impacts

4.7.1 As broadly illustrated in the construction programme, various construction activities may be carried out concurrently.

4.7.2 Based on the preliminary construction programme and the plant inventory (Appendix 4.1) proposed foror the Project, cumulative noise impact arising from different construction activities of the proposed Project on the NSRs were predicted.

4.7.3 The predicted construction noise levels for the unmitigated scenario at each river are listed given in Table 4.6 below. and A sample calculation of the predicted construction noise level for the unmitigated scenario is illustrated provided in Appendix 4.2.

Table 4.6 Summary of Unmitigated Construction Noise Levels During Normal Daytime Working Hours

NSR	Predicted Noise Levels, dB(A)	EIAO-TM Normal Daytime Construction Noise Criteria, dB(A)
Sai Kung River and Sha Ha Diversion Culvert
SK1	69-78	75
SK2	73-85	75
SK3	75-84	75
SK4	82-93	75
SK5	71-88	75
SK6	68-94	75
SK7	66-86	75
SK8	68-84	75
Pak Kong River
PK1	75-89	75
PK2	75-96	75
PK3	75-96	75
PK4	74-90	75
PK5	69-78	75
Ho Chung Channel
HC1	70-92	75
HC2	73-88	75
HC3	78-88	75
HC4	74-97	75
HC5	68-83	75
HC6	76-93	75
HC7	68-82	75
HCT1	65-84	70
HCSC1	65-75	70

4.7.4 The assessment results showed that the predicted cumulative noise levels at representative NSRs would range from 65 to 97 dB(A). Exceedance in the range of 1 to 22 dB(A) was predicted at the NSRs without mitigation measures. Mitigation measures would be required in order to abate the construction noise impacts.

4.8 Mitigation Measures

Adoption of Quiet Plant

4.8.1 For the adoption of quiet plant, the Contractor may be able to obtain particular models of plant that are quieter than the PME given in GW-TM. It is considered too restrictive to specify that a Contractor have to use specific items of plant for the construction operations. It is, however, practical to specify the total SWL of all plant to be used on site so that the Contractor is allowed some flexibility to select plant to suit his needs.

4.8.2 In this assessment, the recommended silenced PME are taken from the BS5228: Part 1:1997, which are known to be in Hong Kong. It should be noted that various types of quiet PME are commercially available in Hong Kong and have been used in other designated projects. The SWL for the quiet PME adopted are summarised in Table 4.7.

Table 4.7 Sound Power Levels for Quiet PME

Quiet PME adopted	SWL, dB(A)
Excavator	105
Dump truck	103
Loader	105
Vibratory roller	96
Concrete lorry mixer	100
Vibratory poker	98
Generator	95

4.8.3 Noise reduction is anticipated with the use of the quite PME. However, the predicted construction noise levels at some NSRs during certain construction stages would not comply with the EIAO-TM noise criteria. Therefore, further noise mitigation measures are required for those affected NSRs.

Use of Movable Noise Barrier and Temporary Noise Barrier

4.8.4 To further reduce construction noise impacts on the affected NSRs, the use of movable noise barrier for particular plants should be was adopted and are summarised in Table 4.8.

4.8.5 According to the GW-TM, a movable noise barrier with a cantilevered upper portion located above the noise generating part of the PME could reduce noise level by 5 dB(A) or up to 10 dB(A), depending on the line of sight that could be blocked by the barriers when viewed from the NSR. Depending on the size of the PME, the dimension of the movable noise barrier will be designed by the Contractor with a view to block the line of sight of NSRs. Barrier material of surface mass in excess of 7 kg/m² is recommended to achieve the desirable screening effect. The design of the movable barriers shall be certified by the Environmental Team (ET) Leader and verified by the Independent Checker (Environment) (IC(E)) to ensure the intended noise reduction effectiveness can be achieved.

Table 4.8 Movable Noise Barrier for Certain Items of PME

Construction Task		PME for which Movable Barrier is Adopted	Barrier Correction, dB(A)
Sai Kung River and Sha Ha Diversion Culvert
Site Clearance		Excavator	5
Channel Construction	Excavation	Loader and Excavator Drainage Pump	5 10
Box Culvert	Sheetpiling	Power rammer	5
	Earthworks	Excavator Drainage Pump	5 10
	Reinforcement Fixing / Concrete operations	Crane and Bar Bender / Cutter Vibratory Poker	5 10
	Backfilling	Excavator / Loader	5
Backfilling / Channel lining		Excavator / Loader Vibratory Poker	5 10
Pak Kong River
Site Clearance		Excavator	5
Channel Construction	Excavation	Loader and Excavator Drainage Pump and Generator	5 10
Box Culvert	Sheetpiling	Power rammer	5
	Earthworks	Excavator Drainage Pump and Generator	5 10
	Reinforcement Fixing / Concrete operations	Crane and Bar Bender / Cutter Vibratory Poker	5 10
	Backfilling	Excavator / Loader	5
Retaining Wall		Crane and Bar Bender / Cutter Vibratory Poker	5 10
Backfilling / Channel lining		Excavator / Loader Vibratory Poker	5 10
Ho Chung Channel
Site Clearance		Excavator	5
Channel Construction	Excavation	Loader and Excavator Drainage Pump	5 10
Box Culvert and Bridge	Earthworks	Excavator Drainage Pump	5 10
	Reinforcement Fixing / Concrete operations	Crane and Bar Bender / Cutter Vibratory Poker	5 10
	Backfilling	Excavator / Loader	5
Weir System / Retaining Wall / Flood Wall		Crane and Bar Bender / Cutter Vibratory Poker	5 10
Backfilling / Channel lining		Excavator / Loader Vibratory Poker	5 10
Piling Work in Ho Chung	Reinforcement Fixing / Concrete operations	Crane and Bar Bender / Cutter Vibratory Poker	5 10

4.8.6 After implementation of the movable noise barriers, all NSRs except SK4, SK6, PK2-4, HC1, HC4 and HC6 would comply with the construction noise criteria as stipulated in the EIAO-TM.

4.8.7 As the use of the movable noise barrier is not sufficient enough to mitigate the noise impact at some NSRs at Sai Kung River, Pak Kong River and Ho Chung Channel, temporary noise barriers are proposed to be erected along the work boundary as depicted in Figures 4.7 - 4.9.

4.8.8 With the adoption of the temporary noise barriers, all items of PME to be used on the construction site would be totally screened. This allowed a reduction in the predicted noise level (PNL) of 10 dB(A) in accordance with the GM-TM.

4.8.9 With the implementation of all above-mentioned mitigation measures, the total SWL for each activity was calculated in Appendix 4.3. The predicted noise levels at all NSRs would comply with the noise criteria. Table 4.9 summarises the mitigated noise levels during normal daytime working hours at NSRs. A sample calculation of construction noise levels for mitigated scenario is presented in Appendix 4.4.

4.8.10 The proposed mitigation measures and plant are made reference to the projects withof similar nature and conditions in Hong Kong. The recommended measures and plants are applicable and available to this Project, and they are expected to be practical in completing the works within the schedule.

Table 4.9 Summary of Mitigated Construction Noise Levels During Normal Daytime Working Hours

NSR	Predicted Noise Levels, dB(A)	EIAO-TM Normal Daytime Construction Noise Criteria, dB(A)	Mitigation Measures Proposed
Sai Kung River and Sha Ha Diversion Culvert
SK1	56-65	75	Use of Quiet PME and Movable Noise Barrier
SK2	60-71	75	Use of Quiet PME and Movable Noise Barrier
SK3	62-71	75	Use of Quiet PME and Movable Noise Barrier
SK4	62-72	75	Use of Quiet PME and Temporary Noise Barrier
SK5	58-75	75	Use of Quiet PME and Movable Noise Barrier
SK6	48-74	75	Use of Quiet PME and Temporary Noise Barrier
SK7	53-73	75	Use of Quiet PME and Movable Noise Barrier
SK8	54-70	75	Use of Quiet PME and Movable Noise Barrier
Pak Kong River
PK1	61-75	75	Use of Quiet PME and Movable Noise Barrier
PK2	61-75	75	Use of Quiet PME and Temporary Noise Barrier
PK3	61-75	75	Use of Quiet PME and Temporary Noise Barrier
PK4	60-69	75	Use of Quiet PME and Temporary Noise Barrier
PK5	55-64	75	Use of Quiet PME and Movable Noise Barrier
Ho Chung Channel
HC1	48-71	75	Use of Quiet PME and Temporary Noise Barrier
HC2	59-74	75	Use of Quiet PME and Movable Noise Barrier
HC3	64-74	75	Use of Quiet PME and Movable Noise Barrier
HC4	52-75	75	Use of Quiet PME and Temporary Noise Barrier
HC5	54-70	75	Use of Quiet PME and Movable Noise Barrier
HC6	54-72	75	Use of Quiet PME and Temporary Noise Barrier.
HC7	54-68	75	Use of Quiet PME and Movable Noise Barrier
HCT1	51-70	70	Use of Quiet PME and Movable Noise Barrier
HCSC1	50-61	70	Use of Quiet PME and Movable Noise Barrier

Good Site Practices

4.8.11 In addition to the foregoing proposal, good site practices would serve to reduce noise levels further. The following site practices should be followed during the construction:

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

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

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

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

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

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

Cumulative Construction Noise Impact

4.8.12 As mentioned in Section 4.5.11, “Improvement of Ho Chung Road” is likely to be undertaken concurrently with the proposed Project. An indicative assessment was undertaken to investigate the cumulative noise impact arising from this Project and the “Improvement of Ho Chung Road”.

4.8.13 The tentative construction programme is shown in Appendix 4.5. It is envisaged that the “Improvement of Ho Chung Road” would be constructed concurrently with this Project during March 2005 to September 2006. The works would mainly involve roadwork and resurfacing. The plant inventory and recommended mitigation measures stated in the Draft Final Report of “Improvement of Ho Chung Road” were used to evaluate the cumulative noise impact from Ho Chung Road and this Project. The total SWL of the plant are provided in Appendix 4.6. The cumulative noise levels at the NSRs have been predicted and the results are presented in Table 4.10 below. Sample calculation of cumulative construction noise levels is presented in Appendix 4.7.

4.8.14 As indicated in Table 4.10, the predicted noise levels at all NSRs would comply with the noise criteria of 75 dB(A).

Table 4.10 Summary of Cumulative Construction Noise Levels at Ho Chung During Normal Daytime Working Hours

NSR	Predicted Noise Levels, dB(A) ⁽¹⁾
NSR	Drainage Improvement in Sai Kung (Ho Chung) ⁽²⁾	Improvement of Ho Chung Road ⁽³⁾	Cumulative
HC1	48-64	62	62-66
HC2	59-70	58	62-70
HC3	64-70	56	65-70
HC4	66-75	53	66-75
HC5	65-70	46	65-70
HC6	68-72	39	68-72
HC7	64-68	36	64-68
HCT1	67-70	41	67-70
SC1	57-61	34	57-61

Note:

(1) During the construction period of this project (Dec 2005 – Sep 2006)

(2) Drainage improvement in Sai Kung (Ho Chung) (With mitigation measures stated in Section 4.8.1 to 4.8.10)

(3) Reference to the Draft Final Report on Improvement of Ho Chung Road (With mitigation measures)

4.9 Residual Environmental Impact

4.9.1 The construction noise impact is anticipated to be within the EIAO-TM requirements given that the proposed mitigation measures are properly implemented. No adverse residual construction noise impact would be envisaged.

4.10 Environmental Monitoring and Audit Requirements

4.10.1 An Environmental Monitoring and Audit (EM&A) programme is recommended to be established according to the predicted occurrence of noisy activities. All the recommended mitigation measures should be incorporated into the EM&A programme for implementation during construction. Details of the EM&A programme are provided in a stand-alone EM&A Manual.

4.11 Conclusions

4.11.1 Noise arising from the construction activities of the Project would have potential impact on the NSRs located in the vicinity of the work sites. The unmitigated cumulative construction noise levels ranging from 65 dB(A) to 97 dB(A) were predicted at the representative NSRs. In short, the predicted noise levels at all the NSRs would exceed the EIAO-TM noise assessment criteria without mitigation.

4.11.2 Sufficient noise control measures would be required to mitigate the potential construction noise impacts. The recommended mitigation measures include: (1) adopting quiet construction plant; (2) using movable and temporary noise barriers; and (3) implementing good site practices.

4.11.3 With the recommended control measures in place, the mitigated noise levels at all the NSRs due to the proposed Project would comply with the daytime construction noise assessment criteria as set out in the EIAO-TM.

4.11.4 An EM&A programme would also be implemented to monitor construction noise impact.

4.11.5 In terms of interfacing with other projects, an indicative assessment was undertaken for cumulative noise impact arising from this Project and the “Improvement work of Ho Chung Road”. The assessment results indicated that the cumulative noise levels at NSRs would comply with the construction noise criteria of 75 dB(A) stipulated in the EIAO-TM.