3 NOISE IMPACT

3.0.0.1 This Section presents an assessment of the potential noise impacts associated with the construction and operation of the proposed Deep Bay Link. Noise impacts during the construction phase are mainly associated with the construction activities and the use of powered mechanical equipment for construction works. For operation phase, the noise impacts are primarily from the road traffic through the Deep Bay Link.

3.1 Legislation, Policies, Plans, Standards and Criteria

3.1.1 Construction Noise

3.1.1.1 The principal legislation governing the control of construction noise is the Noise Control Ordinance (NCO) (Cap 400) and the Environmental Impact Assessment Ordinance (EIAO) (Cap 499). Guidelines concerning the assessment methodology and relevant criteria are provided in the supporting Technical Memoranda (TMs). The following TMs are applicable to the control of noise from construction activities:

• Technical Memorandum on Noise from Percussive Piling (PP-TM)
• Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM)
• Technical Memorandum on Noise from Construction Work in Designated Areas (DA-TM)
• Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM)

Percussive Piling

3.1.1.2 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). A Construction Noise Permit (CNP) is required for such works during the weekday daytime hours (0700-1900hrs Monday through Saturday).

3.1.1.3 When assessing a CNP application for carrying out percussive piling, the Noise Control Authority is guided by the PP-TM. The Noise Control Authority will look at the difference between the Acceptable Noise Levels (ANLs), as promulgated in the PP-TM, and the Corrected Noise Levels (CNLs) that are associated with the proposed piling activities. Depending on the level of noise impact on nearby Noise Sensitive Receivers (NSRs), the Noise Control Authority would determine the time periods for percussive piling operation. The time periods are indicated in Table 3.1.

3.1.1.4 The Government is committed to phase out the use of diesel, pneumatic and steam hammer pile drivers, which are particularly noisy. There are more stringent requirements for the use of diesel, pneumatic and steam hammer after 1 October 1999.

General Construction Works

3.1.1.5 Noise generated by general construction works during normal working hours (i.e. 0700 to 1900 hours on any day not being a Sunday or public holiday) fall within the scope of the EIAO-TM. The recommended noise standards are presented in Table 3.2 below.

3.1.1.6 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 use of powered mechanical equipment (PME) for the carrying out of construction works during the restricted hours would require a Construction Noise Permit (CNP). The Noise Control Authority is guided by the GW-TM when assessing such an application.

3.1.1.7 When assessing a CNP application for the use of PME, the Noise Control Authority will compare the ANL's as promulgated in the GW-TM, and the CNLs (after accounting for factors such as barrier effects and reflections) associated with the agreed PME operations. A CNP may be issued if the CNL is equal to or less than the ANL. The ANLs are related to the noise sensitivity of the area in question and the Noise Control Authority will judge these at the time of the CNP application. As conditions may vary between the time of the EIA for a project and the time of a CNP application, the assignment of any Area Sensitivity Ratings in the EIA is not binding upon the Noise Control Authority. The relevant ANLs are shown in Table 3.3.

3.1.1.8 In addition to the general controls on the use of PME during the restricted hours, the Noise Control Authority has implemented a more stringent scheme via the DA-TM. The DA-TM regulates the use of five types of Specified Powered Mechanical Equipment (SPME) and three types of Prescribed Construction Work (PCW), which are non-PME activities, in primarily densely populated neighborhoods called Designated Areas (DAs) during restricted hours. The SPME and PCW are shown in Table 3.4 below:

3.1.1.9 In the interest of offering additional protection to the population, the carrying out of PCW is generally banned inside a DA during restricted hours. As for the use of SPME, it would be necessary to comply with DA-TM noise level requirements that are 15 dB(A) less than those listed in the GW-TM before a CNP may be issued.

3.1.1.10 Factors such as the assigning of Area Sensitivity Rating, ANLs etc could affect the assessment results of a CNP application. The Noise Control Authority would decide these at the time of assessment of such an application based on the contemporary situations/conditions. It should be noted that the situations/conditions around the sites may change from time to time.

3.1.1.11 Despite any description or assessment made in the subsequent paragraphs, the Noise Control Authority will be guided by the Technical Memorandum (Memoranda) in assessing an application, once filed, for a Construction Noise Permit (CNP). The Authority will consider all the factors affecting their decision taking contemporary situations/conditions into account. Nothing in this report shall bind the Authority in making their decision. There is no guarantee that a CNP will be issued. If a permit is to be issued, the Authority shall include any condition it thinks fit, and such conditions shall be followed while the works covered by the permit are being carried out. Failure to comply with any conditions could result in the cancellation of the permit and prosecution action under the NCO.

3.1.2 Operational Noise / Traffic Noise

3.1.2.1 The EIAO-TM provides guidance on acceptable road traffic noise levels at the openable windows of various types of noise sensitive buildings. The relevant criteria are shown in Table 3.5 below:

3.1.2.2 In cases where practicable direct mitigation measures alone would not be adequate in mitigating noise impacts, indirect technical remedies for existing NSRs may be adopted provided that the residual impacts satisfy all three criteria below:

(i) the predicted overall noise level from the new road together with other traffic in the vicinity must be above the specified noise level (e.g. 70 dB(A) for domestic premises and 65 dB(A) for education institutions, all in L10(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 were commenced; and

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

The total number of existing dwellings, classrooms and other noise sensitive elements that may qualify for indirect technical remedies are then estimated.

3.1.2.3 For the purpose of this assessment, the roads within the study scope could be classified as follows:

• Existing roads: including existing roads that will remain either completely unchanged or that will undergo only very minor alterations, like Castle Peak Road;
• New roads: the road sections covered by this project, i.e. Deep Bay Link and its associated slip roads; and
• Altered/Planned roads: all other new roads under other planned projects, e.g. Shenzhen Western Corridor, Route 10 Northern Section, Widening of Yuen Long Highways, and planned roads in Hung Shui Kiu New Development Area.
  

3.2 Description of Environment

3.2.1 Potential Noise Sources

3.2.1.1 The proposed Deep Bay Link is a trunk road of dual-3 lane standard providing a strategic link between the proposed Shenzhen Western Corridor, Yuen Long Highway and the proposed Route 10. Potential operational phase noise sources from the proposed DBL includes:

• road traffic noise from the traffic carried by DBL;
• noise from the proposed emergency helipad

3.2.1.2 During the construction phase, noise from construction activities is also likely to affect noise sensitive receivers nearby.

3.2.1.3 There are a few existing noise sources in the surrounding areas. They are basically the road traffic noise from distributors and trunk roads, namely Castle Peak Road and Yuen Long Highway.

3.2.1.4 The area is generally under intensive planning for the future development. A strategic growth area, the Hung Shui Kiu NDA, was under active design and planning stage. In HSKNDA, a new town will be formed which creates a number of new noise sensitive receivers near DBL.
3.2.1.5 Yuen Long Highway is also undergoing the design for a dual-3 widening which also increase the amount of traffic noise in the area. The project has completed an EIA Report in December 2001.

3.2.1.6 Furthermore, DBL will connect the traffic from the proposed Route 10 which may also affect noise sensitive receivers nearby.

3.2.2 Noise Sensitive Receivers

3.2.2.1 With reference to Annex 13 of the EIAO-TM, noise sensitive receivers (NSRs) include residential uses (all domestic premises including temporary housing), institutional uses (educational institutions including kindergarten and nurseries, hospitals, medical clinics, homes for the aged, convalescent homes, places of worship, libraries, court of law, performing arts centres, auditoria and amphitheaters) and others. NSRs within a distance of 300 m from the either side of and along the full sketch of the project boundary (including the proposed road and the associate facilities) were identified for noise assessments.

3.2.2.2 Locations of existing and planned/committed NSRs are shown in Figure 3.1. The works limit/area presents the construction work area and the proposed land resumption limit. Existing receivers inside the land resumption limit will be removed at that time. Existing NSRs were identified by reference to topographic maps and field surveys. They are listed in the following Table 3.7.

Table 3.7 Existing Noise Sensitive Receivers (NSRs) Identified

3.2.2.3 Existing NSRs in areas encircled by the proposed Lam Tei Interchange would be resumed together with the proposed Route 10 Northern Section project. The traffic at the beginning of DBL operation would be lower than the traffic in year 2021. Considering the NSRs are low-rise in nature, they are not likely affected during the intermediate period.

3.2.2.4 Planned/committed NSRs in the future were identified by reference to relevant Outline Zoning Plans, Outline Development Plans, Layout Plans and other published plans in relation to the Planning and Development on Northwest New Territories. These NSRs were mostly found in the proposed Hung Shui Kiu New Development Area and some local planned private developments were also identified. Table 3.8 gives the details of the planned/committed NSRs.

Note: information was based on the available data as the date of the issue of this report.

3.2.2.5 For the purpose of this assessment, an alternative layout was included for air and noise assessments for HSKNDA. The alternative layout with NSRs included the following revisions:

• the Government Quarters site in Area 2C and the school sites in Area 2D was swapped; and
• the secondary school and the Indoor Recreation Centre at the side of the West Rail viaduct (Area 1C) was swapped.

3.3 Assessment Methodology

3.3.1 Construction Noise

3.3.1.1 Construction noise impact was assessed by adopting the standard acoustic principles and the methodologies relevant to technical memoranda issue under the Noise Control Ordinance, primarily the TM on Noise from Construction Work other than Percussive Piling (GW-TM).

3.3.1.2 During daytime from 0700hr to 1900hr on weekdays other than general holidays, the assessment of construction noise excluding percussive piling was carried out in accordance with the methodology stipulated in paragraphs 5.3 and 5.4 of Annex 13 and the criteria in Table 1B of Annex 5 of the EIAO-TM.

3.3.1.3 The assessment also made reference to the British Standard BS 5228:Part 1:1984 Noise Control on Construction and Open Sites, Part 1: Code of Practice for Basic Information and Procedures for Noise Control. Sound power levels of equipment will be referenced to these TMs and the BS5228, where applicable, and the emission levels in previous projects in Hong Kong were also be referenced.

3.3.1.4 Figure 3.24 shows the locations of notional noise source for construction noise assessment. Notional noise sources were assumed at the bridge pier location where intensive activities were likely found.

3.3.1.5 Practicable direct mitigation measures including movable barriers, enclosures, quieter alternative methods, re-scheduling and restricting hours of operation of noisy task were recommended if exceedance of relevant criteria was predicted. In case where the mitigated noise levels still exceeded the relevant criteria, the duration of the noise exceedance was given.

3.3.1.6 Cumulative impacts from other projects had been included for assessment. Proposed mitigation measures of the Yuen Long Highway Widening were assumed in place in this assessment with reference to the Final Environmental Impact Assessment Report - Widening of Yuen Long Highway between Lam Tei and Shap Pat Heung Interchange Preliminary Design and Ground Investigation Assignment exhibited under EIAO.

3.3.2 Traffic Noise

3.3.2.1 The computer programme, HFANoise, was used to model traffic noise on the road networks. It adopts methodology of the UK Department of Transport's Calculation of Road Traffic Noise (CRTN) which has been accepted for the assessment of road traffic noise impact in the Annex 13 of the EIAO-TM. The road traffic noise was presented in terms of noise levels exceeded for 10% of the one-hour period for the hour having the peak traffic flow [L10(1hr) dB(A)].

3.3.2.2 The procedures of CRTN assume typical traffic and noise propagation conditions which are consistent with moderately adverse wind velocities and direction. All noise levels were expressed in terms of L10 hourly dB(A). The value of L10 hourly dB(A) is the noise level exceeded for just 10% of the time over a period of one hour. The calculations were worked to 0.1dB(A) keeping within the quoted range of the validity charts. For comparison with the specified noise level or the EIAO-TM standards, the relevant noise level from traffic expected to use the highway was to be rounded to the nearest whole number (0.5 being rounded up). Details of the methods are given in the CRTN.

3.3.2.3 Considering the scope of this Project, road sections were classified as the following categories for purpose of road traffic noise assessment:

(i) New roads

• Deep Bay Link main alignment
• Ramps and slip roads in Lam Tei Interchange joining YLH and Route 10 Northern Section
• Connection points to ramps joining HSKNDA at HSK Interchange
• Connection points to Ha Tsuen Interchange
  
  

(ii) Altered/Planned roads:

• Shenzhen Western Corridor
• Route 10 Northern Section
• Widened section of Yuen Long Highway
• Planned roads in Hung Shui Kiu NDA Development

(iii) Existing roads
 

• Castle Peak Road

3.3.2.4 The road classification for assessment is graphically presented in Figure 3.34. The cross-sections of the different alignment settings are given in Figure 10.6.3.1.

3.3.2.5 Calculations of future road traffic noise were based on the peak hourly flow in respect of the maximum traffic projected within a 15 years period upon commencement of operation i.e. afternoon peak hour traffic flow in year 2021. The traffic flow forecasts were endorsed by Transport Department for use in this EIA and a memo from TD is given in Appendix 3B. It had assumed with the future strategic growth and planning of traffic routes including regional developments like HSKNDA, operation of Route 10 Northern Section, potential widening of Yuen Long Highway to a dual-4-lanes configuration. The traffic flow data for year 2021 afternoon peak hour are presented in Appendix 3B Figures 3.1a, 3.1b and 3.1c.

3.3.2.6 Both the morning peak and afternoon peak for traffic flows were evaluated. Peak hourly traffic may vary for PM & AM at some parts of the DBL. The main reasons for choosing PM peak hourly traffic are: i) DBL mainly serves cross-boundary traffic for which after which the peak is in the afternoon, and ii) The total emissions over the entire DBL are higher in the afternoon considering the flow and length of the road involved. The case may be different for HSKNDA and Yuen Long Highway.

3.3.2.7 The scenario without Route 10 in year 2011 was also evaluated. Without Route 10 in year 2011 the traffic is likely using YLH as the main dispersion route. The year 2021 traffic forecast have taken into account for the possible growth (growth in cross-boundary traffic, incoming population for HSKNDA, and other regional increase in traffic) during the next 15 years after the operation of DBL. The case for year 2021 is much larger in traffic volume as compared to that of the year 2011 and therefore, it is considered as the worst-case within 15 years for use in assessing the environmental impact for traffic air and noise pollution. The traffic flow data for year 2021 afternoon peak hour are presented in Appendix 3B Figures 3.1d and 3.1e.

3.3.2.8 Assessment points (APs) at the worst-affected noise sensitive façade by DBL were selected to represent identified NSRs for quantitative noise assessments. Details of the APs are presented in Figure 3.1 for location and in Appendix 3B for calculation assumptions. Traffic noise levels at the APs in respect of each road section and the overall noise levels from the combined road sections (both new and existing) were calculated.

3.4 Identification, Prediction and Evaluation of Potential Impacts

3.4.1 Construction Phase

Construction Method

3.4.1.1 The construction of DBL alignment typically involves piling, pile cap construction, pier construction and superstructure construction. For the construction of superstructure, two methods of construction are considered for viaducts, namely the segmental launching method and the span by span cast in-situ method. The mainline of DBL together with the ramps cross over YLH, KCRC West Rail and Castle Peak Road where falsework will be high and where bridge decks are fairly straight will best be constructed by segmental launching methods. Other ramps not crossing major roads and where falseworks are low, conventional span by span cast in-situ method should be used. The construction procedure of DBL alignment is illustrated in Figure 3.22.

3.4.1.2 The construction work of DBL could be divided into the following work tasks and areas:

1) Deep Bay Link Mainline
The road layout of the mainline is a dual-3-lane carriageway. However, due to bifurcation of slip roads, the deck is generally wider than 2 lanes in each direction. A twin box section for the mainline is therefore proposed. Typical span length will be 40m with monolithic reinforced concrete column.

2) Ramps in Lam Tei Interchange Connecting to Yuen Long Highway
All ramps at Lam Tei Interchange would be constructed by cast-in-situ method. They can be constructed simultaneously with the Mainline.

3) Precast Yard for Segmental Launching Method
The segmental construction requires a precast yard for fabrication of the concrete segments and the curing and storage of the completed concrete segments. There would be approximately 2500 numbers of segments which may required up to 6 production lines. The size of a fabrication yard will be approximately 500 m2 and the storage yard will be approximately 700 m2 allowing the stacking up of segments.

It is also considered to import concrete segments from Mainland China instead of setting up a precast yard. This would require a barging point at Tuen Mun for shipping the concrete segments and an initial proposal is to use the same barging point as for Shenzhen Western Corridor Project. The environmental impact for this alternative arrangement is assessed in the Section Barging Point for Lung Kwu Sheung Tan.

4) Concrete Batching Plant
Concrete batching plant would be used for the project which would be located at the loop encircles by ramps at Lam Tei Interchange and at Ha Tsuen Interchange.

5) Haul Road Construction traffic
Since there is no large scale site formation nor cut-and-fill works for DBL, the construction traffic generated is small. The access to the site will be diverted to several proposed routes as shown in Figure 3.25.
3.4.1.3 The proposed locations of the precast yard and concrete batching plant are shown in Appendix 3A - Drawing 22913/P/53/597 and Drawing 22913/P/53/598.

3.4.1.4 For the assessment of construction noise impact on the sensitive receivers at Ngau Hom Shek, the construction activities in association with the construction activities of Shenzhen Western Corridor are assumed as follows:

Construction activity 1 - construction of SWC shore alignment;
Construction activity 2 - construction of DBL landside alignment at the work site;
Construction activity 3 - construction of DBL alignment;
Construction activity 4 - SWC work site;
Construction activity 5 - construction of haul road;
Construction activity 6 - construction traffic;
Construction activity 7 - construction of SWC shore alignment (500m offshore); and
Construction activity 8 - construction of SWC shore alignment (1500m offshore).

3.4.1.5 The SWC work site (construction activity 4) will be required by SWC team for the construction of shore alignment and this part of alignment (construction activity 2) will therefore be constructed at the last stage. In the view of this arrangement construction activities 1, 3, 4, 7, 8 would likely be working at the same time under the worst-case. When these activities are completed, construction activity 2 will be carried out over the area of the work site at the end. The construction of haul road and haul road traffic which are in different locations will be separately analysed.

3.4.1.6 The information regarding SWC have been agreed with the SWC Project Team for use in this EIA report as best available information at the time of submission.

3.4.1.7 In general percussive piling is not recommended due to potential noise impacts and bored piling would be used instead.

Tentative Construction Schedule

General Works

3.4.1.8 Only a tentative construction schedule is available in this preliminary design stage. The construction period of DBL is anticipated from 2003 to 2006. Major construction activities would be started in 2003 and completed in 2006.

3.4.1.9 It is anticipated that there will be no construction work carried out during the restricted hours (i.e. between 7pm and 7am and any time during general holidays including Sunday) under the scheduled construction programme for general works, except the unavoidable night works for several road segments over major roads and rails.

Night Works

3.4.1.10 Unavoidable night works are likely required for limited alignment construction crossing over major roads (Castle Peak Road and Yuen Long Highway) and the West Rail and LRT.

3.4.1.11 For constructing the viaduct decks spanning across railways and major roads using balance cantilevering method, it is a must as required by Transport Department and the Police Force that no live traffic should be underneath the launching operation for safety reasons. Further consultation with KCRC revealed that segmental viaduct construction would not be permitted above live rail tracks during the operational hours of both LRT and West Rail. Hence these activities can only be carried out when the railways are in the isolation period and roads are closed to public traffic. It would be during the night-time period when the closure of railway and roads would cause less disturbance to the traffic.

3.4.1.12 The isolation period of KCRC and LRT will be around 1:00am to 5:00am. Major road closure will be around 12:00 midnight to 6:00am. Hence night works are unavoidable in this regard.

3.4.1.13 The major activity will be the launching deck segments. Each operation can launch two segments at each night. For a 2.5m wide segment, a span of around 40m long will contain 16 segments. It will required 16 days to complete one span using balance cantilever method. It is envisaged that the contractor may propose faster erection method such that 2 segments can be launched per night, but it will be subject to the contractor's proposal.

3.4.1.14 It is essential to use segmental launching for this project, since this will save the erection of false work to support the bridge deck. The height of the bridge decks are relatively high in general, for instance, the deck is 16m above Castle Peak Road in order to span over the West Rail viaduct. There are difficulties and expensive in erecting the false works for such a height. Segmental launching is the most effective and common construction method to over come these difficulties.

3.4.1.15 However according to our experience in the construction of Route 3 country park section and the West Rail viaducts recently, there are requirements from the traffic police and KCRC that the no live traffic should be underneath the launching operation. That is to say the roads have to be closed and the Railways had to be isolated during such operation. For the strategy roads such as Yuen Long Highway, Castle peak Road, West rail and LRT, the only time they can be closed or isolated will be around 12:00 midnight to 6:00am every night. Although the window for the closure of isolation is short, a pair of segment launching is usually achievable.

3.4.1.16 As reviewed from previous projects, this operation is unavoidable and this is the only construction method that the bridge deck can be constructed for such a type programme project. Therefore the night shift are unavoidable. The operation, however will only mobilize the launching girder and the lorries supplying the bridge segments. No other plants are required. In general, each span requires around 16 continuous nights, say 2 weeks per span. There are 2 spans over West Rail, 2 spans over LRT and Castle Peak Road and 8 spans over YLH. The detail work methods have not been available at this stage.

3.4.1.17 In the view of the stringent noise limits during night-time, the preliminary estimate showed that the it was difficult to mitigate to the 45 dB noise limit even that all reasonable mitigation measures were considered exhausted including quiet plant and temporary noise barriers had been assumed. The prediction is given in Appendix 3B Table 3A2.7.

3.4.1.18 Before these unavoidable night works to be carried, the future contractor has to apply for a Construction Noise Permit (CNP) under NCO for carrying nighttime construction work under the circumstance. It should be note that the Noise Control Authority, at its discretion, issue a CNP even if the noise limit is exceeded if it can be demonstrated to his satisfaction that carrying nighttime construction work during restricted hours would cause less public annoyance or inconvenience than would be caused by carrying out the construction work during non-restricted hours.

Alignment Construction at Local Level

3.4.1.19 Construction of alignment segment at local level would be a more important concern that the overall construction programme. Sensitive receivers are mainly affected by the construction of road alignment which in turn operates in a sequential manner. After completion of a particular task, the construction activities and equipment move to the next location. Receivers are only affected temporarily and intermittently.

3.4.1.20 The timing for the construction of road segment in front of a sensitive receiver would likely be the true impact period of construction. For a typical span of 40m long, piling for each pier is about 3 weeks, wait for 2 weeks, then complete pile cap within 2 weeks, wait 3 weeks and construct the pier. The construction of pier requires 3 weeks, wait for 3 weeks before constructing the deck. The first pier will be available to receive load after 16 weeks. It would take another 2 weeks for launching of road segments.

3.4.1.21 It is estimated that the fabrication yard and the associated batching plant can be formed and set up within 2 months of commencement. The first segment can be cast in the 4th month after commencement. Launching should not start until there is a balance between the speed of building piers and deck launching. It is very likely that the launching should start 8 months after commencement.

Cumulative Impact due to Concurrent Other Construction Activities

3.4.1.22 For the purpose of this EIA, cumulative impacts of DBL associated with other concurrent project was assessed based on the following programme:

Project Anticipated Construction Programme
Deep Bay Link 2003-2006
Shenzhen-Hong Kong Western Corridor* 2003-2005
Yuen Long Highway Widening* 2003-2005
Hung Shui Kiu New Development Area* 2004-2010
Route 10 Northern Section* 2004-2007
San Wai Sewerage Treatment Works* 2004-2007

* The programme is tentative only and subject to review by respective study.

3.4.1.23 Since most of the noisy construction work like foundation and structural work would be completed by 2005 for DBL, the cumulative impacts would only be signification with the construction of SWC, Route 10 Northern Section and Yuen Long Highway widening at localized areas.

Potential Impacts for Unmitigated Scenario

3.4.1.24 DBL is constructed to a certain extent by resumption of existing rural land. The extent of land resumption together with the construction work site boundary is typically 10 m to 30 m from the edge of the proposed road alignment. Under these circumstances, some existing noise sensitive receivers are lying quite close to the construction work site. Table 3.9 shows the buffer distance required for the different work tasks as an indication.

3.4.1.25 It can be seen that NSRs located within 200 m away from the construction activities would likely be affected by the construction noise for unmitigated scenario.

3.4.1.26 The haul roads to construction sites likely to cause noise concern were assessed. The proposed routes of construction site access were shown in Figure 3.25. Since there would be no longer any large-scale cut and fill, or site formation activities, the peak haul road traffic would likely be around 40 veh/hr for both to-and-from directions. While the peak haul road traffic near Ngau Hom Shek would be around 80 veh/hr for both to-and-from directions.

3.4.1.27 Noise due to haul road traffic was estimated and the details of the prediction are presented in Appendices 3A1 (for Ha Tsuen and Lam Tei areas) and 3A3.6 (for Ngau Hom Shek area). The results show that at distances 3m, 5m, and 10m from the centre of the haul road the noise levels would be 70, 68 and 65 dB(A) respectively. Hence, the potential noise impacts to nearby NSRs would not be adverse and be within the acceptable standard of 75 dB(A).

3.4.1.28 For the haul road traffic noise impact arising from Fung Kong Tsuen Road near Ngau Hom Shek, the results show that at distances 3m, 5m, and 10m from the centre of the haul road the noise levels would be 73, 71 and 68 dB(A) respectively. Hence, the potential noise impacts to nearby NSRs would not be adverse and be within the acceptable standard of 75 dB(A).

3.4.1.29 Details of construction noise activities and assessments are presented in Appendices 3A1 and 3A2.

3.4.1.30 For the sensitive receivers at Ngau Hom Shek (E24), details of the construction noise activities and assessments are given in Appendix 3A3.
Barging Point at Lung Kwu Sheung Tan

3.4.1.31 During construction stage, it would be necessary to provide a barging point for barges to transport the construction materials (e.g. concrete for in-situ construction, precast viaduct segments, dump waste (e.g. dredged materials) through marine route and then by land to the site. There is no marine construction site for the Project.

3.4.1.32 The proposed location for the barging point is located at Lung Kwu Sheung Tan to the south of WENT Landfill along Yung Long Road. As shown in Drawing No. 23306/P/03/104 in Appendix 3A, road access is provided by Yung Long Road connecting Lung Kwu Tan Road, which then leads to Tuen Mun Road to other places. The roads are currently used as access for the power station in Lung Kwu Tan, thus upgrading is generally not necessary.

3.4.1.33 The number of vehicles for loading and unloading in barging points is expected to be small, likely around 2 nos. per hour at maximum. The likely mechanical equipment involved are one barge, the crane of the barge or probably a mobile crane.

3.4.1.34 No NSRs were identified within 300m from this proposed barging point and hence there would be no adverse impact expected.

3.4.2 Operational Phase

3.4.2.1 Predicted traffic noise levels at NSRs are summarized in Table 3.16 for existing NSRs, Table 3.17 for Planned NSRs and Table 3.18 for HSKNDA.

Ngau Hom Shek

3.4.2.2 DBL road alignment at this section is elevated and is on bridge structure. Surrounding the NSR (NSR E24) are squatter houses or temporary houses and are generally one storeys high. Since the road alignment is elevated, noise from traffic is screened by the bridge structure itself and impact is considered minimal. Predicted traffic noise levels at NSRs were around 65-70dB(A), which are within the EIAO-TM standard.

Hung Shui Kiu to Castle Peak Road

3.4.2.3 Existing landuse near the Hung Shui Kiu Exit and the mainline of DBL north of Castle Peak Road are two or three storeys high village houses or squatter houses. The predicted noise impacts are acceptable for the existing NSRs E14 and E16 but not for the existing NSR E15 (village houses near Tsing Chuen Wai). Exceedances of 1 to 4 dB(A) of noise levels at E15 was found. It was mainly due to cumulative noise impacts from the mainline of DBL and the existing Castle Peak Road.

Between Castle Peak Road and Lam Tei Interchange

3.4.2.4 Existing NSRs (NSRs E8 Fuk Hang Tsuen and E9 Tuen Mun San Tsuen) are two or three storeys high village houses or squatter houses (1 storey), while NSR E7 (Botania Villa) is 12 storeys high residential buildings. NSRs E10 and E11 are a secondary school and Miu Fat Buddhist Monastery, respectively. Noise impacts were acceptable for E9, but exceedances were found at E7, E8, E10 and E11. The predicted noise levels ranged from 66-79dB(A) for E7 and E8. Noise exceedances of about 1 to 9 dB(A) were found at E10 and E11.

3.4.2.5 Higher noise levels were predicted at those NSRs close to the mainline of DBL, Ramps B and D of Lam Tei Interchange and the existing Yuen Long Highway. The traffic from these roads is the major source of noise level exceedances.

3.4.2.6 Future planned residential area (NSRs F1A and F1B) at Fuk Hang Tsuen Road CDA was also found to exceed the noise criteria of 70dB(A). As the site area was just about 55 m away from the mainline of DBL at the nearest, therefore the total building height is already restricted to 45 mPD in the planning conditions posed by Planning Department.

Between Castle Peak Road and Route 10

3.4.2.7 Existing NSRs (NSRs E5, E12 and E13) near Tsoi Yuen Tsuen and YLH are two or three storeys high village houses or squatter houses (1 storey), whereas NSR E4 is the Lam Tei Gospel School (a primary school). The predicted noise levels ranged from 64-79dB(A).

3.4.2.8 Noise level exceedances of 70dB(A) were found at the NSRs close to the ramps of DBL and the existing Yuen Long Highway. The source of exceedances of these NSRs was mainly from the traffic on Yuen Long Highway and the ramps of DBL.

DBL mainline with Ramp H  joining Yuen Long Highway

3.4.2.9 Existing NSRs (NSRs E1 Lo Fung Hang and E3 near Route 10 portal) are two or three storeys high village houses or squatter houses, whereas NSR E2 is a temple, Nam On Fat Tong. Since Yuen Long Highway is an elevated structure, exceedance of noise levels at lower floor levels was not predicted but higher floor levels. Noise exceedances of 1 to 5 dB(A) were predicted.

3.4.2.10 The source of exceedances of noise level of 70dB(A) was mainly due to the high traffic flow of Yuen Long Highway. Partial traffic noise was from Ramp H joining the Yuen Long Highway with traffic flow of about 600 veh/hr.

Ramps A, B, C and D of DBL joining to Yuen Long Highway

3.4.2.11 Existing NSRs (NSRs E6 near Shun Tat Street, E18 near HSKNDA Area 3B and E19 Tan Kwai Tsuen) are two or three storeys high village houses or squatter houses, whereas NSR E20 is a school, Ying Yin School. The predicted noise levels ranged from 69-82dB(A).

3.4.2.12 Traffic from Ramps A, B, C and D and Yuen Long Highway is the major source of noise exceedance. The new road of Hung Shui Kiu area near Ramp C has minor contribution to noise exceedance.

3.4.3 Hung Shui Kiu New Development Area

3.4.3.1 At this stage, the Hung Shui Kiu New Development Area is undergoing planning study and there is no firm layout for use in this environmental impact assessment. A 2-tier approach is proposed to assess the noise impacts from DBL on sensitive uses in HSKNDA:

(a) calculation of noise impact at lot boundary of sensitive uses in HSKNDA, with direct at source mitigation measures in place in DBL;

(b) where exceedances are found, calculation of the minimum buffer distances between lot boundary of sensitive uses in HSKNDA and DBL required for reducing the residual impact to within the EIAO-TM.

3.4.3.2 In addition to the original layout, an alternative layout was provided by HSKNDA project team for testing in this EIA report.

3.4.3.3 For the purpose of comparison with relevant standards, the noise levels at assessment points (APs) should be applied. The summary for noise levels predicted at assessment points at site boundaries and typical school layouts are given in Table 3.18 and the detail results are given in Appendix 3B. Exceedances of EIAO-TM standards were found caused by both DBL and HSKNDA planned roads.

3.4.4 Noise from the Proposed Helipad

3.4.4.1 A helipad is proposed near Ha Tsuen Interchange for emergency uses. There would be no routine flight expected. Figure 3.3 shows the location of the helipad and it is observed that there are no existing NSRs identified within 300 m. The future landuse zoning is likely to be "green belt" and "recreational" and hence there would be no NSRs in the future. Based on the data from other previous monitoring at Tamar Basin, it was estimated that the maximum noise levels (Lmax) during take-off (measured at 25 m) were about 100 dB(A) for helicopter type Sikorsky S76 and Black Hawk S70. The highest recorded levels were noted to occur during take-off. To meet the HKPSG noise standard of 85 dB(A) Lmax, a setback of 200 m from the nearest NSR is required. In this case, without any NSRs located within 300 m, the proposed helipad location should not have any adverse impact.

3.5 Mitigation of Adverse Impacts

3.5.1 Construction Phase

3.5.1.1 The predicted noise levels showed that construction noise activities are likely to give rise to adverse daytime noise impacts at some of the identified NSRs. Mitigation measures are therefore required and the following forms of mitigation have been considered:

Use of Quiet Plant and Working Methods

3.5.1.2 The use of quiet plant was identified to be a feasible solution to tackle the adverse impacts associated with construction works. The Contractor should obtain particular models of plant that are quieter than standard types given in the GW-TM. The benefits achievable in this way would depend on the details of the Contractors' chosen methods of working, and it would be too restrictive to specify that a Contractor has to use specific items of plant for the construction operations. It is therefore both preferable and practical to specify an overall plant noise performance specification to apply to the total SWL of all plant on the site so that the Contractor is allowed some flexibility to select plant items to suit his needs. It should be noted that various types of silenced equipment could be found in Hong Kong. However, the Authority, when processing a CNP application, will apply the noise levels contained in the relevant statutory TMs unless the noise emission of a particular piece of equipment can be validated by a certificate or through a demonstration.

3.5.1.3 Quiet PME is defined as PME whose actual SWL is less than the value specified in the GW-TM for the same item of plant. Reference can be made to the British Standard BS5228: Part 1:1997 Control on Construction and Open Sites.

Using Temporary and Movable Noise Barriers

3.5.1.4 Movable barriers that can be located close to noisy plant can be very effective at screening NSRs from particular items of plant or noisy operations. Movable barriers of 3 to 5 m height with a small cantilevered upper portion and skid footing can be located within a few metres of stationary plant and within about 5 m or more of a mobile equipment such as an excavator and mobile crane etc., such that the line of slight to the NSR is blocked by the barriers. It would be possible for the Contractor to provide purpose-built noise barriers or screens constructed of appropriate material (minimum superficial density of 7 kg/m2) located close to operating PME, in order to reduce the noise impact to the surrounding sensitive uses. Certain types of PME, such as generators and compressors, can be completely screened by portable barriers giving a total noise reduction of 10 dB(A) or more.

3.5.1.5 For this assessment, it was estimated that movable noise barriers can achieve a 10 dB(A) noise reduction for stationary plant and 5 dB(A) for movable plant.

Reducing the Numbers of Plants Operating in Critical Areas Close to NSRs

3.5.1.6 In general the number of plant should be left to the choice of the Contractor so that in combination with the selection of quiet plant, any further reduction in the total plant noise level, or the site specific maximum sound power levels, as described above, can be achieved. It would be appropriate to restrict the number of operating PME within certain parts of the site that are very close to the NSRs in order to reduce the level of noise impacts. This method could be more effective for activities associated with foundation work, pile construction and excavation activities in which a large number of PME are anticipated, but not all of them would be utilised at the same time.

Using Noise Screening Structures or Purpose-built Noise Barriers along the Site Boundary

3.5.1.7 Considering the low-lying nature of surrounding NSRs (typically village houses or temporary houses), it would be effective to have noise screening structures along the site boundary to protect NSRs close to the construction site boundary. The following measures could be applied to reduce the construction noise:

i) Site buildings such as office and stores could be grouped together to form a substantial barrier separating site operations and nearby noise sensitive premises. This may be applicable for sites such as Lam Tei Interchange area and other work sites.

ii) Stacks of certain materials such as bricks, aggregate, timber or top soil can be strategically placed to form a barrier. This may be applicable for construction of road alignment.

iii) For adverse cases, purpose-built noise barriers or screens could be placed along the site boundary. This may be applicable for road alignment sites.

3.5.1.8 An estimate of about 10dB(A) reduction could be achieved for substantial structures or purpose-built noise barrier/screen. Higher reduction and benefit could also be achieved for NSRs close to the site.

Good Site Practice

3.5.1.9 The following good site practice should be adopted during the construction phase:

• The contractor should site noisy equipment and activities as far from sensitive receivers as practical. Also, temporary site offices (and other similar structures) should be located, as far as is possible, such that sensitive receivers are screened by these structures from the line of sight of the construction areas.
•  Intermittent noisy activities should be scheduled to minimize exposure of nearby NSRs to high levels of construction noise. For example, noisy activities could be scheduled at times coinciding with periods when the schools are likely to be unoccupied. Prolonged operation of noisy equipment close to the schools should be avoided.
• Idle equipment should be turned off or throttled down. Noisy equipment should be properly maintained and used no more often than is necessary.
• Construction activities should be planned so that parallel operation of several sets of equipment close to a given receiver is avoided.
• Where possible, the numbers of concurrently operating items of plant should be reduced through sensitive programming.
• Construction plant should be properly maintained and operated. Construction equipment often has silencing measures built in or added on, e.g. compressor panels, and mufflers. Silencing measures should be properly maintained and utilized.

Proposed Specific Construction Noise Mitigation Measures

3.5.1.10 The proposed mitigation measures for construction noise are arranged in an increasing level of efforts. Since the actual activities in the construction sites may vary at local site level, the level of mitigation measures adopted should also be determined with reference to the findings of the EM&A programme.

3.5.1.11 The number of PME used on site should be reviewed from time to time to avoid excessive or dummy PME located too close to NSRs. Good site practice should be followed through the construction phase.

3.5.1.12 Noise sensitive receivers were affected by both fixed construction sites (precasting yards, concrete batching plant and work sites) and alignment construction for the carriageways. Two main causes for noise exceedance were identified:

i) NSRs are too close to the construction sites, particularly for those along the road alignment
ii) Construction of foundation was noisy but short-term

3.5.1.13 To minimize the potential of adverse impact, the following measures are specifically recommended to be adopted for DBL:

i) Purpose-built construction site hoardings are to be installed in such a way to act as an acoustic screen/noise barrier for active carriageway construction work proximity to NSRs in locations shown in Figure 3.20(A, B). The boundary wall or hoarding shall:

• have a mass per unit of surface area in excess of 7 kg/m2 to prevent sound transmitted through the wall/screen;
• have no gaps or openings at joints in the screen material; and
• have a vertical height of 3m to screen the NSRs.

The exact location of purpose-built construction site hoarding would be subject to local site conditions. Temporary noise barriers should be placed close to the noisy mechanical equipment in case the purpose-built site hoarding could not effectively screen the NSRs.

ii) Quiet plant/power mechanical equipment of sound power level lowered than those listed in Table 3 of the GW-TM shall be used for all construction sites as far as practicable.

3.5.1.14 Considering the NSRs close to the construction site boundaries (within 30m) are low-rise housings (typically 1 storey in height), their sensitive facades could be screened by a 3m high purpose-built site hoarding for viewing the ground-level construction equipment (both moving and stationary). A 10 dB(A) reduction was assumed in this regard since it would be able to screen both stationary and mobile equipment along the other side of the hoarding. For construction superstructure or other elevated works, the effect would be less and it was assumed nil reduction in this case. The purpose-built site hoarding should be erected until the completion of structural work or the time no longer having noisy work. The effectiveness is illustrated in Figure 3.21 and the site hoarding should be erected and adjusted in any case to protect the nearby NSRs.

3.5.1.15 Table 3.10 summarizes the specific mitigation measures proposed for construction activities. Table 3.11 presents the summary of results.

3.5.1.16 Cumulative construction impacts were assessed for likely concurrent projects in the area. Based on the available information, it was understood that construction activities of Hung Shui Kiu NDA development, Yuen Long Highway Widening and Route 10 Northern Section were likely coincided with the construction schedule of DBL. Since construction work is likely controlled by actual construction progress and respective construction schedule, the assessment had been carried out based on some worst estimates and worst NSRs.

3.5.1.17 NSRs near Tsing Chuen Wai and Castle Peak road are likely affected by both HSKNDA and DBL construction activities. Based on the worst affected assessment point 8327 (NSR E15), it was found that the overall noise level would be around 72dB(A) with DBL being the main source of construction noise. The level is within the acceptable noise limit of 75dB(A) with mitigation measures in place.

3.5.1.18 NSRs near the portal of Route 10 were also assessed as represented by assessment points 76 (NSR E3 near Route 10 portal ) and 8801 (NSR E4 Lam Tei Gospel School). Cumulative noise levels are 72-73 dB(A) for both NSRs and NSR E3 is found within the noise limit of 75 dB(A). For Lam Tei Gospel School (E4 8801), it requires further mitigation measures in order to meet the noise limits (70 and 65 dB(A)) as indicated in Table 3.12.

3.5.1.19 Cumulative impacts with SWC have been assessed with the APs of NSR E24 Ngau Hom Shek and presented in the results shown in Table 3.10. No exceedances were found.

3.5.1.20 With only the mitigation measures proposed in Table 3.10, some of the NSRs still exceeded the noise criteria from 1 to 4 dB(A). It is found that these NSRs are too close to the construction work. As present in Table 3.11, the four NSRs found to have residual impacts are E4 AP8801 Lam Tei Gospel School (residual impact of 3 dB during normal school date and 8 dB during examination period), E8 AP8414 Fuk Hang Tsuen village house (residual impact of 1 dB, representing about 2 dwellings), E12 AP43 Rural /village houses near Tsoi Yuen Tsuen (residual impact of 1 dB, representing 5 dwellings) and E13 AP8605 village house in Tsoi Yuen Tsuen (residual impact of 4 dB, representing about 6 dwellings). The duration is expected to be around 5 weeks during the pile and pile cap construction.

3.5.1.21 The residual impact could be reduced by special measures which are summarized in Table 3.12. For NSRs E4, E8 and E12, the residual impacts could be reduced to relevant limits by special measures. Only NSR E13 would be subject to residual impact of 4dB for a duration of about 5 week during non-restricted hours i.e. normal daytime (0700-1900) at intermittent worst periods under the current programme.

3.5.1.22 For E4 Lam Tei Gospel School, early liaison with the school for the planned examination periods is recommended to plan for the construction work. Noisy piling and pile cap construction should be avoided.

3.5.1.23 The special measures require the reduction of the number of concurrent bridge pier constructions. The applicability of special measures should be reviewed during the construction phase by the Contractor as a part of the EM&A process. A construction noise mitigation proposal is required to be submitted by the contractor for the reviewed by ET and approval by IEC.

3.5.1.24 Calculations of the predicted noise level with proposed specific measures are detailed in Appendix 3A2.5.

3.5.1.25 The construction plant inventory assumed for this assessment was confirmed by the project proponent HyD as practicable and reasonable for the completion of the project within the scheduled construction programme based on the information available at this stage.

3.5.1.26 A detailed review of the construction noise assessment is recommended prior to the construction work commencement during the construction stage to re-conform the requirements for construction noise mitigation. The review should be carried out by the Construction Contractor and the Environmental Team using contemporary information regarding construction equipment and construction programme.

Table 3.11 Summary of Potential Cumulative Construction Noise Impacts

3.5.2 Operational Phase

Road Traffic Noise

3.5.2.1 Noise mitigation measures in form of barriers are proposed to build on the DBL in order to reduce excessive noise on various existing and future sensitive receivers. All NSRs are predicted to be within EIAO standards.

3.5.2.2 Details of proposed noise barriers are shown in Figure 3.2 and are summarized in Table 3.13 respectively. These noise barriers shall be designed and constructed to comply with the Guidelines On Design of Noise Barriers - Environmental Protection Department & Highways Department of the Government of the Hong Kong SAR, First Issue March, 2001. The setup for typical type of proposed noise barriers is given in Figures 10.6.3.6 and 10.6.3.7.

3.5.2.3 Some proposed mitigation measures of the Yuen Long Highway Widening were applied in this assessment with reference to the Final Environmental Impact Assessment Report - Widening of Yuen Long Highway between Lam Tei and Shap Pat Heung Interchange Preliminary Design and Ground Investigation Assignment exhibited under EIAO. This would ensure that the peak traffic flow within 15 years from YLH Dual-3 scenario was mitigated. For the recommended noise barriers on DBL in the YLH EIA Report, this DBL EIA has carried out assessment using the worst-case scenario of DBL as mentioned in Sections 3.3.2.4 to 3.3.2.8 which is considered more appropriate and realistic for DBL EIA. While assuming that the barriers on YLH will be implemented as agreed in its exhibited EIA report, this DBL EIA assessed, formulated and optimized the barriers on DBL in accordance with EIAO-TM. The may be some difference between the barriers shown in the YLH EIA on DBL alignment but in any case the NSRs are mitigated to a worst-case scenario in this DBL EIA.

3.5.2.4 Low noise surfacing will be adopted as the standard measures of HyD's guidelines for the roads with vehicle speed limit greater than 70km/hr for DBL. All proposed low noise surfacing should be designed according to the design guidelines/practice notes issued by HyD Guidance Note No. RD/GN/010A and RD/GN/011B. The traffic noise assessment has assumed that low noise road surfacing materials would be provided to the Deep Bay Link.

Table 3.13 Summary of Proposed Noise Mitigation Measures Implemented by DBL

(1): All proposed low noise surfacing should be designed according to the design guidelines/practice notes issued by HyD Guidance Note No. RD/GN/010A.

(2): * Des/C/O/Dec: Design/Construction/Operation/Decommissioning;

HyD: Highways Department.

Existing noise sensitive receivers

3.5.2.5 Table 3.16 summarizes the traffic noise impacts under unmitigated and mitigated scenarios for the existing sensitive receivers. With the proposed direct mitigation measures in place, noise levels would be reduced to within EIAO-TM standard except for a few existing sensitive receivers which are currently affected by existing roads.

3.5.2.6 Noise levels at NSR E10 and E11 (Madam Lau Kam Lung Secondary School and Miu Fat Buddhist Monastery) still exceeded the noise standard by 8 to 9dB(A) after mitigation. The source of exceedance is found solely due to the traffic noise of the existing Castle Peak Road. As the contribution of traffic noise from DBL was less than 1dB(A), these NSRs are not eligible for indirect measures under this Project.

3.5.2.7 Noise level at NSRs E8, E13 and E15 still exceeded the standard by about 1 to 4dB(A). The source of exceedance was due to the traffic noise of the existing Castle Peak Road, and the contribution of traffic noise from DBL was less than 1dB(A). These NSRs are also not eligible for indirect measures under this Project.

Other Future/planned noise sensitive receivers

3.5.2.8 Table 3.17 summarizes the traffic noise impacts under unmitigated and mitigated scenarios for the future planned sensitive receivers. Noise impacts on future sensitive receivers at planned residential areas and school sites except HSKNDA were all reduced to acceptable levels, except one location at NSR F9 Area 3C (RR2).

3.5.2.9 NSR F9 is part of the future phases of HSKNDA and information from TDD and PlanD indicated that it would be likely a residential development with a maximum building height of 12 storeys in the Planning Area 3C. While no further planning information is available, assessment was carried at site boundary. It is found that there is an exceedance of 3 dB(A) at 12th floor and no exceedance at 9th floor or lower. The receiver is also found mainly affected by Yuen Long Highway (not DBL) although barriers are proposed by Yuen Long Highway Widening EIA.

3.5.2.10 The main reason for this exceedance is due the higher traffic flow data used in the DBL EIA for year 2021. In the Yuen Long Highway Widening EIA, the project scope was limited to a dual-3 carriageway (with 3 lanes on both sides) widening from the current dual-2 alignment (with 2 lanes on both sides). The amount of traffic was assumed to be around 8600 veh/hr in the dual-3 lanes. Mitigation measures of Yuen Long Highway had been designed to this capacity for dual-3 alignment. Due to the forecasted increase in traffic on Yuen Long Highway, there would be a need to further widen the dual-3 to a possible dual-4 alignment (4 lanes on both sides) in the future. Taking into account of this possible future arrangement, the traffic flow forecast for Yuen Long Highway used in this DBL EIA was higher at around 11600 veh/hr for year 2021. This is the worst case for assessment in this DBL EIA under the foreseeable transport planning. Exceedance is identified because the mitigation measures for dual-3 configuration of Yuen Long Highway could not handle the predicted increase in traffic.

3.5.2.11 Based on the prediction results, additional noise barriers on the central divider of YLH would be required for the dual-4 configuration of YLH. However, the application is likely limited by the structural loading capacity of existing bridge structures at some locations. A combination of three vertical barrier sections as shown in Table 3.14 are predicted able to achieve 70 dB(A) standard at NSR F9. These barriers are on the at-grade sections of YLH avoiding the existing bridge structures and are therefore considered feasible subject to the future investigation and detail design. No residual impact is expected in this case.

3.5.2.12 Considering the fact that the exceedance is only found after the completion of the potential dual-4 widening project of Yuen Long Highway with no further or additional measures and the proposed 12 storeys development in the Planning Area 3C of HSKNDA completed, it should be this dual-4 widening project to formulate and implement direct mitigation measures to control the traffic noise impact. By that time, an EIA would be required to deal with the impact to achieve an acceptable level based on the updated information. Upon review of the likely construction work for noise barriers on the central divider of YLH and the future difficulties in construction, it would be better in this stage to design and allow for the spatial requirements of the foundation works for these barriers on the central dividers. This should be taken up as part of the DBL Design and Construction assignment.

3.5.2.13 Both the HSKNDA project and the future dual-4 widening of Yuen Long Highway project should review the case for F9 Area 3C in their respective environmental impact assessments.

3.5.3 Hung Shui Kiu New Development Area

3.5.3.1 A semi-enclosure (200m in length on DBL) together with the cantilever barriers are proposed to minimize the traffic noise impacts at HSKNDA. With the proposed direct mitigation measures in place, noise levels would be reduced to within EIAO-TM standard except for a few future sensitive receivers at future school sites for assessment points at site boundary as summarized in Table 3.18. The assessment points for HSKNDA layout is given in Figure 3.31. The details of the assessment results are given in Appendix 3B.

3.5.3.2 The assessment results indicate that most assessment points (APs) at site boundaries of the planned sites are within the EIAO-TM standards except school site 2B with 2 dB(A) exceedance.

3.5.3.3 For the proposed alternative layout, most assessment points (APs) at site boundaries of the planned sites are found within the EIAO-TM standards except school sites at 2B and 2C with 2 dB(A) exceedance.

3.5.3.4 Sources of traffic noise contributions for these affected APs are in two folds: noise from DBL and noise from HSKNDA planned roads (Road P1 and local road L1). After the application of mitigation measures in the form of the 200m semi-enclosure and cantilever barriers together with the cantilever barrier on HSKNDA Road P1, noise contribution from DBL dropped substantially from 76 dB(A) to 61 dB(A) at school site 2B for example. The contribution from HSKNDA planned road (mainly from Road L1) was around 65 dB(A).

3.5.3.5 Further noise mitigation measures on DBL were explored which include 3 cases as shown in the following Table 3.20:

Table 3.20 Summary of Noise Mitigation Measures Explored for DBL for HSKNDA

3.5.3.6 The effectiveness of extending the 200m semi-enclosure is found less than 1 dB(A) reduction of noise levels at assessment points. The direct noise mitigation measures are considered not acoustically effective in this case. In addition, semi-enclosure will be a substantial structure and long semi-enclosure would cause undesirable landscape and visual impact. Noise mitigation measures should therefore be formulated using an integrated approach for development planning and the noise sources.

3.5.3.7 As it is not likely that a sensitive facade school would be located directly at site boundary with large angle of view based on a conventional school layout, a typical school building was incorporated into the HSKNDA layout and the alternative layout for a more realistic assessment.

3.5.3.8 With the use of a typical school building, the actual noise level experienced by sensitive facades is found to be smaller than at site boundaries. All the assessment points at the typical school building facade are found to be meeting the EIAO-TM standard of 65 dB(A).

3.5.3.9 No further residual impacts are expected in this case. Hence, it is considered that the current mitigation scheme is able to protect both the HSKNDA layout and its alternative layout. The layouts with the incorporation of typical school buildings are shown in Figures 3.32 and 3.33 for reference.

3.5.3.10 The mitigation measures and constraints as identified in this EIA for consideration of HSKNDA are summarized in Table 3.18. There may be some uncertainties and likely changes in the future HSKNDA since it is understood that HSKNDA is undergoing further planning study. It is likely that (i) population accommodation may change, (ii) traffic flow forecast may change due to future update information and (iii) landuse pattern may change. Therefore, the mitigation measures and constraints are only suggestions for consideration during the design of HSKNDA. The validity of the predicted impacts in this report and the suggested measures/constraints are recommended to be reviewed in the future study of HSKNDA by the Territory Development Department.

3.6 Definition and Evaluation of Residual Impacts

3.6.1 Construction Phase

3.6.1.1 Only Four NSRs were found to have residual impacts are E4 AP8801 Lam Tei Gospel School (residual impact of 3 dB during normal school date and 8 dB during examination period), E8 AP8414 Fuk Hang Tsuen village house (residual impact of 1 dB, representing about 2 dwellings), E12 AP43 Rural /village houses near Tsoi Yuen Tsuen (residual impact of 1 dB, representing 5 dwellings) and E13 AP8605 village house in Tsoi Yuen Tsuen (residual impact of 4 dB, representing about 6 dwellings). The duration is expected to be around 5 weeks during the pile and pile cap construction.

3.6.1.2 The residual impact could be reduced by special measures which are summarized in Table 3.12. The residual impact could be reduced by special measures which are summarized in Table 3.12. For NSRs E4, E8 and E12, the residual impacts could be reduced to relevant limits by special measures. Only NSR E13 (representing about 6 dwellings in Tsoi Yuen Tsuen) would be subject to residual impact of 4dB for a duration of about 5 weeks during non-restricted hours i.e. normal daytime (0700-1900) at intermittent worst periods under the current programme. For E4 Lam Tei Gospel School, early liaison with the school for the planned examination periods is recommended to plan for the construction work. Noisy piling and pile cap construction should be avoided.

3.6.1.3 The special measures require the reduction of the number of concurrent bridge pier constructions. The applicability of special measures should be reviewed during the construction phase by the Contractor as a part of the EM&A process. A construction noise mitigation proposal is required to be submitted by the contractor for the reviewed by ET and approval by IEC.

3.6.1.4 No further residual impacts exceeding the applicable criteria other than the four NSRs mentioned were predicted due to this Project with the implementation of the proposed mitigation scheme during the construction phase. For the four NSRs (E4, E8, E12 and E13), the likely residual impacts are presented in Section 3.6.1.1. The effectiveness and practicability of specific measures for reducing residual impacts needed to be reviewed on-site by the Contractor through the submission of contraction noise mitigation proposals.

3.6.2 Operational Phase

3.6.2.1 No residual impact exceeding the applicable criteria was predicted due to this Project with the implementation of the proposed mitigation scheme and the proposed development layout/constraint in HSKNDA.

3.6.2.2 It is estimated that about 1073 existing dwellings, 280 planned dwellings (excluding HSKNDA), 2 schools (Ying Yin School and Lam Tei Gospel School) and two places of worship (Nam On Fat Tong and Miu Fat Buddhist Monastery) that would exceed the EIAO noise standards without mitigation measures, would be protected to meet EIAO requirements for DBL with the implementation of the proposed direct technical remedies (traffic noise mitigation measures). The high-densities and medium densities developments and schools in HSKNDA would also be mitigated to within EIAO requirements for DBL.

3.6.2.3 The proposed mitigation measures under DBL project include a 200m long semi-enclosure, about 6.2 km of cantilever barriers and about 4.9 km of vertical barriers in summary.

3.7 Environmental Monitoring and Audit

3.7.0.1 Due to the potential construction noise impact to the nearby residential developments, it is recommended that EM&A for construction noise be carried out throughout the construction period of the project. To ensure implementation of construction phase mitigation measures with consideration of practicability in local levels, the exact location of the purpose-built construction site hoardings and other noise mitigation measures shall be reviewed during the construction phase. The changes or alternative proposals shall be reviewed by Environmental Team and the Independent Environmental Checker.

3.7.0.2 Monitoring at the operational phase is also suggested to check the effectiveness of direct measures on road traffic noise sources. The details of the EM&A program are given in Section 11 of this report and the separate EM&A manual.