3. CONSTRUCTION IMPACTS

3.1 Introduction

The Study Brief specifically requires an assessment of the water quality, fisheries, cultural heritage, ecological (terrestrial and aquatic), landscape and visual impacts, hazard to health and waste management arising from the project along with an assessment of the waste arisings. However it is recognised that during construction there may be some impacts arising from the construction activities such as construction dusts and noise. This section has therefore been included to address the potential environmental impacts including air quality and noise during the construction phase, identify any mitigation measures necessary and to define any special requirements during the construction phase such as monitoring and auditing or provision of special pollution control measures. Reference is also made to the potential issues of loss of yield relating to the Shap Long Reservoir.

3.2 Sensitive Receivers

Sensitive receivers (SRs) for both air quality and noise, which have been identified within the study area of the Project, are illustrated on Figure 3.1. These include a few scattered village houses at Ham Tin Tsuen and Pui O Lo Wai Tsuen on Chi- Ma- Wan Peninsula as well as the residential buildings of Cheung Kwai Estate, Greenery Crest, village houses and the institution of Buddhist Wai Yan Memorial College along the west coast of Cheung Chau Island. No sensitive receiver was identified within an area of 500m radius in the vicinity of the Tai Long Wan tunnel portal. Descriptions of the representative sensitive receivers are presented in Table 3-1.

Table 3-1 Summary of the Representative Sensitive Receivers (Air and Noise)

SRs	Location	Usage	Closest Distance (m)
Pui O, Lantau
SR12	Pui O Lo Wai Tsuen	Village House	20
SR2	Ham Tin Tsuen	Village House	10
SR3	Ham Tin Tsuen	Village House	20
SR4	Hostel (Lot No. 27) in the vicinity of Pui O tunnel portal	Hostel	40
Cheung Chau
SR54	Greenery Crest	Residential	30
SR65	Buddhist Wai Yan Memorial College	Institution	10
SR7	Village house at Pak She Praya Street	Village House	10
SR8	Cheung Kwai Estate	Residential	50

3.3 Air Quality

The potential air quality impacts associated with the installation of the 3 x 132 kV circuits from Pui -O via Chi -Ma -Wan Peninsula via the Adamasta Channelsea crossing towards Cheung Chau have been considered for the land based section of the works only although they are not required under the Study Brief. For the section of submarine cables, construction dust impact will not be expected. For the remaining section, dust generation as a result of earth excavation is the major source of air pollution during the construction phase. Following completion of construction works there will be no adverse environmental impact. Suitable mitigation measures, where necessary, are recommended to protect the ASRs and to ensure that the legislative criteria and guidelines are satisfied.

3.3.1 Relevant Regulations and Guidelines

The principal legislation that is relevant to air pollution from construction sites is the Air Pollution Control Ordinance (APCO) (Cap. 311). Relevant Air Quality Objectives for Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP) extracted from EIA-TM are tabulated presented below in Table 3-2 below. For construction dust, EIA-TM also recommends a maximum hourly level of 500 µg/m³ for TSP at nearby Air Sensitive Receivers (ASRs).

Table 3-2 Hong Kong Air Quality Objectives

Averaging Time	Pollution Concentration Level (µg/m^3 )
	TSP	RSP
1 hour^1	500^*	N.A.
24 hour^2	260	180
Annual^3	80	55

Notes:

(1) Not to be exceeded more than three times per year.

(2) Not to be exceeded more than once per year.

(3) Arithmetic means.

N.A. Not Available

* Maximum allowable dust levels at ASRs provided in the EIA-TM.

3.3.2 Existing Environment

The existing environment of the proposed cable alignment is primarily affected by the traffic on Pui O such as South Lantau Road and Chi Ma Wan Road, as well as on Cheung Chau such as Cheung Chau Sai Tai Road, Tai Hing Tai Road, Praya Street and Pak She Praya Street. No industrial source has been identified in the area. As such, the local traffic is considered to be the dominant source affecting the ambient air quality.

As tThe proposed project is on Lantau Island and the , there is currently one fixed air quality monitoring station is currently operated by EPD in Tung Chung, which is the closest monitoring station to this Project, has been used to obtain dlocated in Tung Chung. ata reported for the year 1999. These data are contained in Table 3-3 for The key parameters for pollutants – Total Suspended Particulates (TSP) and Respirable Suspended Particulates (RSP) data reported for the year 1999 at this station is givendemonstrated in Table 3-3.

Table 3-3 Annual Average of TSP and RSP Monitored at Tung Chung in 1999

Air Pollutants	Annual Average (µg/m^3)
TSP	75
RSP	48

3.3.3 Potential Sources of Impact

Dust, in relation to the construction of underground cable, cable tunnel and submarine cable, will be generated from blasting, reclamation, excavation, filling, material handling and vehicular movements on unpaved work sites and found to be are the main sources of dust. No batching plant will be is required to be established on-site. Major worksites have been identified along the alignment and shown in Figure 3.2. Activities to be undertaken at the worksites are discussed below.

Construction of Underground Cable

Dust generation during the construction of the underground cable is mainly arisesd from the excavation of the trench along the routeworksite.

Construction of Cable Tunnel

The Chi -Ma -Wan cable tunnel is expected towill be excavated by drill and blast method or tunnel boring machine (TBM) over a period of 3480 weeks with 25,000 Mm³ of spoil being generated, or by drill and blast technique (alternative method). Two possible worksites, the northern portal area in Pui O Wan and southern portal area in Tai Long Wan East, have been identified for the tunneling works. At both end portals in Pui O Wan and Tai Long Wan East, theThe excavated spoils from thePui O tunnel portal are expected to will be transported away by trucks. trucks while those extracted from Tai Long Wan tunnel portal are expected towill be disposed by barges using the temporary landing area after the tunnel has been drivlled throughn.

Construction of Submarine Cable

For the section of submarine section,cables, no adverse dust impacts are expected.

3.3.4 Construction Dust Assessment Methodology

Dispersion Model

The extent of dust impacts arising from the construction of project has been predicted using the USEPA approved model Fugitive Dust Model (FDM) in conjunction with the construction programme. The Compilation of Air Pollutant Emission Factors, 5th Edition, US Environmental Protection Agency, 19956, (AP-42) was used to determine the various fugitive dust sources.

Meteorological Data Input

Sequential meteorological data for 1999 from Cheung Chau and King’s Park weather stations, operated by Hong Kong Observatory, was used as input to the model to obtain 1-hour and 24-hour average TSP concentration at the identified ASRs. Data obtained from Cheung Chau and King’s Park stations used as input to the model includes wind direction and speed together with atmospheric Pasquill stability class, mixing heights and air temperature.

Emission Factors

Emission factors, for various fugitive dust sources have been determined based on the USPEPA Compilation of Air Pollution Emission Factors, 5^thth Edition (AP-42). Emission factor for typical construction operations given in the USPEPA is 1.2 tons per acre of construction per month of activity (296.5 g/m²/month). The emission factors used for carrying out the modelling are summarised in Table 3-4. Dust emission factor of 3.2 x 10^-4 g s^-1 m^-2 was obtained by converting the above emission factor based on 26 working day per month and 10 operation hours per day. Calculations of the emission factors are given in Appendix A.

The dust emission from the construction of underground cable and cable tunnel is associated with blasting, excavation, material handling and vehicle movement on unpaved road. The emission factor for general construction is illustrated in Table 3-4 below.

Table 3-4 Emission Factors for General Construction Activities

Activities	Emission Factors	Remarks
General Construction	3.2 x 10^-4 g s^-1 m^-2	Based on USEPA AP-42 Vol. 1 5^th Edition, Section 13.2.3

Prediction of 1-hour TSP Levels

It was assumed that construction would take place over ten hours per day. The corresponding meteorological data has thus been used as input to the FDM. The highest predicted TSP levels were obtained and compared with the recommended 1-hour limit of 500 mgm^-3.

Prediction of 24-hour TSP Levels

As the time variation of dust emissions is not considered in the FDM, the daily TSP levels for daytime construction activities are therefore determined by simulating the model with the default option of an 8-hour averaging period. Meteorological data was used for the period 0900 – 1700 hours. The 24-hour TSP level was then estimated by multiplying the modeled results by a conversion factor (8 hours out of 24 hours = 1/3) to take account of the 8-hour construction period, i.e. one-third of the 8-hour TSP levels predicted from the model. The predicted 24-hour TSP levels from daytime activities and the background daily TSP level were added together and compared with the AQO of 260 mgm^-3.

3.3.5 Evaluation of Impact

Construction dust impacts were modelled using the Fugitive Dust Model (FDM) with worst case assumptions as input data and at ground level. Predicted hourly and daily TSP levels at the identified ASRs are shown in Table 3-5 below. The background annual average TSP levels of 75 mgm^-3 extracted from EPD’s Tung Chung Air Quality Monitoring Station has been added to the predicted hourly and daily results to provide the cumulative impact.

Table 3-5 Predicted Hourly and Daily TSP Levels (mmgm^-3) – Without Mitigation

ASRs	Areas	Locations	Dust Impacts^(1) Maximum Hourly Average TSP Level^(1)	Maximum Daily Average TSP Level^(1)
ASR1	Pui O, Lantau	Pui O Lo Wai TsuenHam Tin Tsuen	161193	8384
SR2		Ham Tin Tsuen	184	83
ASR32		Ham Tin TsuenPui O Lo Wai Tsuen	254146	8781
ASR46		Hostel (Lot No. 27)	591406	9892
ASR54	Cheung Chau	Greenery Crest	154140	8280
SR6		Buddhist Wai Yan Memorial College	212	83
SR7		Village House along Pak She Praya Street	226	86
SR8		Cheung Kwai Estate	169	79
Dust Criteria			500	260
Notes: (1) Background TSP level is included in the results. (2) (2) Bolded figure values represents dust levels exceeding the criteria.

As indicated in Table 3-5, the predicted 24-hourly and daily1-hour TSP concentration levels at all the ASRs except for SR4 are complyied with the AQO criteria of 500260 mmgm^-3 and 260500 mmgm^-3 respectively duringusing underground cable and cable tunnel construction.

Owing to the close proximity of the hostels (approx. 70m) to the Pui O tunnel portal area and the temporary working platform, exceedance of hourly TSP at SR4 was predicted. In order to reduce the adverse dust impact during construction, dust suppression control measures such as regular watering are recommended. A dust reduction efficiency of 50% can be practically achieved by applying watering twice a day.

With the implementation of the recommended mitigation measures, the mitigated hourly and daily TSP concentration levels were predicted and the results are presented in Table 3-6.

Table 3-6 Predicted Hourly and Daily TSP Levels (mgm^-3) – With Mitigation

ASR	Area	Location	Hourly Average TSP Level^(1)	Daily Average TSP Level^(1)
SR1	Pui O, Lantau	Pui O Lo Wai Tsuen	118	79
SR2		Ham Tin Tsuen	130	79
SR3		Ham Tin Tsuen	164	81
SR4		Hostel (Lot No. 27)	333	87
SR5	Cheung Chau	Greenery Crest	115	79
SR6		Buddhist Wai Yan Memorial College	144	79
SR7		Village House along Pak She Praya Street	151	81
SR8		Cheung Kwai Estate	122	77
Dust Criteria			500	260
Notes: (1) Background TSP level is included in the results.

In Table 3-6, the predicted hourly and daily TSP concentration levels at all the ASRs are well below the AQO criteria.

In addition,

According to the contour plots of mitigated 1-Hhourly and daily TSP concentrations are presented as shown in Figures 3.4 and 3.5 respectively., Nno exceedances of AQO criteria at the sensitive uses are identified. Therefore, no residualadverse construction dust impacts areis expected.

The input and output files of the FDM Model for the dust assessment during construction phase are provided in Appendix B.

3.3.6 Mitigation Measures

The construction works at the Pui O tunnel portal are likely to cause Construction dust impact on the nearby ASR if no mitigation measures are in place from the above limited construction works would unlikely to be of a concern. However, the construction dust impact can be reduced to an acceptable level with the implementation of dust control measures. Both general and specific mitigation measures are recommended to ensure no adverse air quality impact during construction phase.

Specific

Dust suppression efficiency of 50% can be achieved by applying watering twice a day.

General

Nevertheless, tThe following control measures are stipulated in the Air Pollution Control (Construction Dust) Regulation and should be implemented to minimise the dust nuisance.

· the stockpile should be properly treated and sealed with latex, vinyl, bitumen or other suitable surface stabiliser if a stockpile of dusty materials is more than 1.2m but lessmore than 1.2m high and lies within 50m from any site boundary that adjoins a road, street, or other area accessible to the public;

· effective dust screens, sheeting or netting should be provided to enclose the scaffolding from the ground floor level of the building or if a canopy is provided at the first floor level, from the first floor level, up to the highest level of the scaffolding where a scaffolding is erected around the perimeter of a building under construction;

· dump truckskip hoist for material transport should be totally enclosed by impervious sheeting;

· any excavated dusty materials or stockpile of dusty materials should be covered entirely by impervious sheeting or sprayed with water so as to maintain the entire surface wet, and recovered or backfilled or reinstated within 24 hours of the excavation or unloading;

· stockpile of dusty materials should not extend beyond the pedestrian barriers, fencing or traffic cones;

· dusty materials remaining after a stockpile is removed should be wetted with water and cleared from the surface of roads;

· vehicle washing facilities should be provided at every vehicle exit point;

· the area where vehicle washing takes place and the section of the road between the washing facilities and the exit point should be paved with concrete, bituminous materials or hardcores;

· where a site boundary adjoins a road, streets or other area accessible to the public, hoarding of not less than 2.4m high from ground level should be provided along the entire length except for a site entrance or exit;

· every main haul road should be scaled with concrete and kept clear of dusty materials or sprayed with water so as to maintain the entire road surface wet;

· the portion of road leading only to a construction site that is within 30m of a designated vehicle entrance or exit should be kept clear of dusty materials;

· every stock of more than 20 bags of cement should be covered entirely by impervious sheeting or placed in an area sheltered on the top and the 3 sides;

· cement delivered in bulk should be stored in a closed silo fitted with an audible high level alarm which is interlocked with the material filling line such that, in the event of the silo approaching an overfilling condition, an audible alarm is triggered and the material filling stops within one minutes;

· silo used for the storage of cement not be overfilled;

· loading, unloading, transfer, handing or storage of bulk cement or any cement during or after the de-bagging process should be carried out in a totally enclosed system or facility, and any vent or exhaust should be fitted with an effective fabric or equivalent air pollution control system or equipment;

· cement, or any other dusty materials collected by fabric filters or other air pollution control system or equipment should be disposed of in totally enclosed containers;

· stockpile of dusty materials should be either covered entirely by impervious sheeting, placed in an area sheltered on the top and the 3 sides; or sprayed with water so as to maintain the entire surface wet;

· all dusty materials should be sprayed with water prior to any loading, unloading or transfer operation so as to maintain the dusty material wet;

· vehicle speed should be limited to 10 kph except on completed access roads;

· every vehicle should be washed to remove any dusty materials from its body and wheels before leaving the construction sites;

· the load of dusty materials carried by vehicle leaving a construction site should be covered entirely by clean impervious sheeting to ensure that the dusty materials do not leak from the vehicle;

· the working area of excavation should be sprayed with water immediately before, during and immediately after the operations so as to maintain the entire surface wet;

The following control measures are recommended during blasting of works:

· the area within 30m from the blasting area shall be wetted with water prior to blasting;

· blasting shall not be carried out when the strong wind signal or tropical cyclone warning signal No. 3 or higher is hoisted unless prior permission of the Commissioner of Mines is obtained.

· wire mesh, gunny sacks and sandbags should be used on top of the blast area at each shot to prevent flying rock and dust;

· water the surface of the blast area to increase its moisture content;

· dust filters should be fitted to the tunnel construction ventilation systems;

· vents of all silos and weighing scale shall be fitted with fabric filtering system; and

· seating of pressure relief valves of all silos shall be checked, and the valves resealed if necessary, before each delivery.

Material Handling

·The height from which fill materials are dropped should be controlled to a minimum practical height to limit fugitive dust generation from unloading;

·Any stockpiles of aggregate or spoil should be covered and water applied;

·Water spray should be used during the handling of excavated and fill material where dust is likely to be created; and

·All dusty materials should be sprayed with water immediately prior to any loading, unloading or transfer operation so as to maintain moisture content of the dusty materials.

Earthworks

·The amount of exposed soil should be kept in minimal by re-vegetation of completed earthworks.

3.3.7 Residual Impacts

No residual air quality impact is expected.

3.3.8 Environmental Monitoring & Audit

Full compliance with the AQOs during construction will likely achieved at all air sensitive receivers without the requirements of mitigation measures. Therefore, routine dust monitoring during construction is not required but regular site audits are recommended to be conducted to ensure the implementation of good site practice and appropriate mitigation measures.

3.3.9 Conclusions

A quantitative assessment on the construction dust impacts has identified that fugitive dust is the primary potential air pollutant during the proposed works. The assessments have demonstrated that apredicted an exceedance of hourly TSP dust criteria at the hostel, SR4, was predictedimpact will be minimal. for the situation where no mitigation measures were in place. Wwith the application of the established and practical dust suppression techniques such as regular watering twice a day, covering/dampening any stockpiles and dampening dusty materials before transportation and the control measures stipulated in the Air Pollution Control (Construction Dust) Regulation, the construction dust impacts can be reduced by more than 50% to an acceptable level. No residual air quality impact Through the proper implementation of the recommended mitigation measures, dust generation will be further controlled and exceedance of the acceptable criteria is not expected. As a result, no routine air quality monitoring is recommended.

that baseline dust monitoring and dust impact monitoring is carried out prior to and during the construction works.

3.4 Noise

This section presents an assessment of the potential noise impact associated with the installation of the 3 x 132 kV circuit from Pui -O via Chi -Ma -Wan Peninsula via Sea Crossing towards Cheung Chau. The quantitative assessment methodology which has been adopted is presented and control measures, to ensure the effective protection of the identified sensitive receivers, are recommended.

3.4.1 Relevant Regulations and Guidelines

General Construction Works

In Hong Kong, construction noise within “restricted hours” (i.e. between 19:00 to 07:00 hours from Monday to Saturday and any time on public holidays) is controlled under the Noise Control Ordinance (NCO) (Cap. 400) and the relevant Technical Memoranda (TMs) issued by the Environmental Protection Department (EPD) through a Construction Noise Permit (CNP) system.

If construction works are carried out during “restricted hours”, a CNP has to be obtained from EPD allowing 28 days for the application to be processed. In addition, any percussive piling work can only be carried out with a valid CNP issued by the Authority. The TMs classify a variety of uses including domestic premises, hostel and place of public worship as noise sensitive receivers (NSRs).

The Noise Control Authority will consider a well-justified CNP application, once fielde, for construction works within restricted hours as guided by the relevant Technical Memorandum issued under the Noise Control Ordinance. The Noise Control Authority will take into account of contemporary conditions/situations of adjoining land uses and any previous complaints against construction activities at the site before making his decision in granting a CNP. Nothing in this EIA Report shall bind the Noise Control Authority in making his decision. If a CNP is to be issued, the Noise Control Authority shall include in it any condition he thinks fit. Failure to comply with any such conditions will lead to cancellation of the CNP and prosecution action under the NCO.

Although the TMs do not provide any statutory control over construction noise during the “non-restricted hours”, a limit of L_eq(30min) 75 dB(A) is proposed for all domestic premises including temporary housing accommodation in the “Practice Note for Professional Person, PN2/93” issued by the Professional Persons Environmental Consultative Committee in June 1993. For schools, the recommended noise levels during normal schools days is L_eq(30min) 70 dB(A) and is lowered to L_eq 65 dB(A) during examination periods. These limits have been applied on major construction projects and are now widely accepted in Hong Kong. The same noise criteria are stipulatedcan be found in Table 1B Noise Standards for Daytime Construction Activities in the gazetted Technical Memorandum on EIA Process issued under Section 16 of the EIA Ordinance which also specify the relevant noise standards for hotels and hostels as shown in Table 3-76.

Table 3-76 Noise Standards for Daytime Construction Activities

Uses	0700 to 1900 Hours on Any Day Not Being a Sunday or General Holiday Leq (30 mins) dB(A)	1900 to 0700 Hours or Any Time on Sundays or General Holidays
All domestic premises including temporary housing accommodation	75	See Note (iii)
Hotels and hostels	75
Educational institutions including kindergartens, nurseries and all others where unaided voice communication is required	70 65 (during examinations)

Notes :

(i) The above standards apply to uses which rely on opened windows for ventilation;

(ii) The above standards shall be viewed as the maximum permissible noise levels assessed at 1m from the external facade;

(iii) The criteria laid down in the relevant technical memorandum under the Noise Control Ordinance for designated areas and construction works other than percussive piling may be used for planning purpose. A Construction Noise Permit (CNP) shall be required for the carrying out of the construction work during the period.

(Source : Table 1B of Technical Memorandum on EIA Process.)

3.4.2 Existing Environment

The existing noise environment is dominated by road traffic. Pui O such as South Lantau Road and Chi Ma Wan Road, as well as Cheung Chau such as Cheung Chau Sai Tai Road, Tai Hing Tai Road, Praya Street and Pak She Praya Street are the major sources of road traffic noise. No industrial source has been identified in the area and noise from traffic mainly contributes to the daytime and nighttime background noise levels in the area.

The existing noise environment at Pui O, Lantau is dominated by road traffic. South Lantau Road and Chi Ma Wan Road are the major sources of road traffic noise. Sometimes the sea wave may generate a high background noise level.

In Cheung Chau, there isare no vehicular roads for automobiles so the major noise sources come from commercial activities and the community. During holidays, the background noise is always higher as many tourists visit Cheung Chau hosts many visitors.

3.4.3 Potential Source of Impacts

Various construction activities have been identified which could cause elevations in noise levels at the nearby NSRs. A typical construction programme for Pui O via Chi Ma Wan via Sea Crossing towards Cheung Chau, has been developed which is shown in Figure 2.4. It is recognised that the Contractor may develop a different construction programme and construction method from the one presented in this report, however it will be his responsibility to demonstrate that his methods ensure compliance with the criteria stipulated in the preceding sections.

As indicated in the preliminary construction programme, the main construction activities comprise:

· installationconstruction of underground cable;

· construction of cable tunnel; and

· laying of submarine cable.

Installation of Underground Cable

The main construction activities include road breaking, trench excavation, cable laying, backfilling, removal of debris and road paving.

Construction activities at this project are expected to operate during normal daytime working hours (i.e. 0700 to 1900 hours on any day but not being a Sunday or public holiday).

A plant inventory has been established based on previous relevant highway project experience and is presented in Table 3-87.

Table 3-78 Powered Mechanical Equipment Used (Underground Cable)

Activity	PME Employed	Identification Code	Sound Power Level dB(A)
Road Breaking	Air Compressor	CNP 001	100
	Hand-held Breaker	CNP 023	108
	Dump Truck	CNP 067	117
	Backhoe	CNP 081	112
Trench Excavation	Backhoe	CNP 081	112
Road Reinstatement	Compactor	CNP 050	105
	Concrete Lorry Mixer	CNP 044	109
	Vibratory Poker	CNP 170	113

As mentioned previously, Cheung Chau does not possess vehicular access for automobiles, no dump trucks and or backhoes are expected to be used for installing underground cables. Trolleys areis expected to be employed for transporting the excavated materials.

ConstructionInstallation of Cable Tunnel

The Chi Ma Wan Peninsula cable Ttunnel areis expected willto be excavated preferably by a tunnel boring machine or possibly using or the drill and blast method. Temporary works areas The tunnel portals will be located at two possible worksites will locate at, the northern portal area in Pui O Wan and the southern portal area in Tai Long Wan East respectively. Tunnel excavation works are expected to take place during normal daytime working hours (i.e. 0700 to 1900 hours on any day not being a Sunday or public holiday) for the first 100m. Beyond this initial length, 24-hour working is expected which is normal practice in tunnel construction and provides optimal programming and use of resources.

During restricted hours the construction activities will be contained within the tunnel and tunnel portal blast doors will be closed. All materials excavated during restricted hours will be stockpiled within the tunnel or at the tunnel portal and will be removed only during normal working hours. These measures will significantly reduce noise emissions associated with construction of the tunnel therefore no noise impacts from the nighttime construction of the tunnel are anticipated.

In Pui O Wan, the excavated spoil from the tunnel will be transported away by trucks. At the southern portal area in Tai Long Wan East, about 25,000 Mm³ of spoil will be excavated and transported off-site by truck.barges.

A plant inventory has been established by the tunnel designer and is presented in Table 3-98.

Table 3-98 Powered Mechanical Equipment Used for Tunnel Construction

Activity	PME Employed	Identification Code	Sound Power Level dB(A)
General	Loader	CNP 081	112
	Backhoe / Muck CarLoader	CNP 081CNP 081	112112
	Concrete Lorry MixerBackhoe / Muck Car	CNP 044CNP 081	109112
	Mobile CraneConcrete Mixer	CNP 048CNP 045	11296
	Dump TrucksHoist, Passenger/Material (Pneumatic)	CNP 067CNP 121	117108
	Concrete PumpDump Trucks	CNP 047CNP 067	109117
	Mobile generatorConcrete Pump	CNP 101CNP 047	108109
	CompressorMobile generator	CNP 002CNP 101	102108
	Water PumpCompressor	CNP 281CNP 002	88102
	Ventilation FanWater Pump	CNP 281CNP 241	88108
Site Formation	Rock Drill (Hydraulic)	CNP 182	123
	Shotcrete Vehicle	CNP 047	109
	Explosive Delivery Vehicle	CNP 141	112
TBM Tunnel Construction (Envisaged DesignPreferred Method)	Tunnel Boring Machine	-	88
	Conveyor Belt System	CNP 041	90
Drill & Blast Tunnel Construction (Alternative DesignMethod)	Rock Drill (Hydraulic)	CNP 182	123
	Conveyor Belt System	CNP 041	90
	Shotcrete Vehicle	CNP 047	109
	Explosive Delivery Vehicle	CNP 141	112
Lining Construction	Concrete Delivery Truck	CNP 141	112
	Pumping Plant	CNP 047	109

TAs Tthe lining construction of the tunnel will take place inside behind the tunnel so the noise impact for this activity does not needs to be assessed.“portal”, no noise impact is expected and therefore this activity has not been assessed.

As there is no noise sensitive receiver at Tai Long Wan, the noise impact for delivery by barge does not need to be assessed.

construction will take place inside the tunnel so the noise impact for this activity is required to be assessed.

LayingInstallation of Submarine Line

The major vessels that will be employed for laying the submarine cables including lay barge, tugb boat, warning boat, pontoon barge and floating crane, etc. The proposed PMEs will be used for the installation of submarine cables are given in Table 3-10.

Table 3-10 Powered Mechanical Equipment Used (Submarine Cable)

Activity	PME Employed	Identification Code	Sound Power Level dB(A)
Laying Submarine Cable	Lay Barge	CNP 061	104
	Tub Boat	CNP 221	110
	Warning Boat	CNP 061	104
	Pontoon Barge	CNP 061	104
	Floating Crane	CNP 048	112

Construction works under water, an adverse noise impact on the nearby village houses would not be expected. Therefore, no detailed assessment is required.

The major vessels that will be employed for laying the submarine cables including lay barge, tugb boat, warning boat, pontoon barge and floating crane, etc. The proposed PMEs will be used for the installation of submarine cables are given in Table 3-109.

Table 3-109 Powered Mechanical Equipment Used (Submarine Cable)

According to the GW-TM, the notional source postionposition of the employed PME for laying the submarine cables will be taken to be a point 50m from the promenatepromenade at Cheung Chau. Therefore, the distance between the PME and the closest noise sensitive receiver is expected to be over 100m and any noise generated will be attenuated by distance. It should also be noted that in the typhoon shelter, the laying of cables will be completed by divers due to the physical constraints of walking within this confined area.As stated in Section 2 the cables will be laid by diver in the typhoon shelter and PME is not expected to be used. The distance between the PME and the closest noise sensitive receiver is expected to be over 300m and thus as noise will be attenuated to acceptable levels. No further assessments of the noise from laying submarine cables has been carried out.

3.4.4 Assessment Methodology

A methodology for assessing construction noise other than percussive piling has followed the guidelines set out in the Technical Memorandum on Noise from Construction Work other than Percussive Piling (GW-TM). The methodology is as follows:

· identify the likely type, sequence and duration of principal noisy construction activities required for the implementation of the proposed project;

· identify a list of plant inventory likely to be required for each construction activity;

· calculate the maximum total sound power level (SWL) for each construction activity using the plant list and SWL data given for each plant in the technical memorandum;

·

·representative NSRs as defined by the EIAO-TM have been identified, based on existing and committed landuses in the study area that may be affected by the worksite. For the purposes of this study, NSRs have been identified up to a distance of 300m from the alignment. However, this distance may be reduced, subject to the first layer of NSRs providing adequate acoustic shielding;

· calculate the distance attenuation and barrier corrections to NSRs from worksite notional noise source point; and

· predict construction noise levels at NSRs in the absence of any mitigation measures.

If the noise assessment criteria are exceeded at NSRs, mitigation measures must be considered. A re-evaluation of the total SWL for each construction activity will be made assuming the use of practical mitigation measure such as “quiet” equipment and movable noise barriers. If the criteria were still exceeded, further mitigation measures such as reduction in noisy plant working simultaneously would be considered.

3.4.5 Evaluation of Impacts

As there is no noise sensitive receiver within 300m from the work site at Tai Long Wan tunnel portal, no construction noise impact generated from this work site is required to be assessed.

The unmitigated noise levels associated with the installation of 3 x 132kV supply circuit from Pui O via Chi Ma Wan Peninsula via sea crossing towards Cheung Chau has been predicted for the worst case representative NSRs for each construction activities and the results are summarised in Table 3-11.. Details and of the calculation are summarised in Table 11 as well as contained provided in Tables C-1 and C-2 of Appendix C, and takinge into account of noise attenuation over distance.

Table 3-11C-2 in Appendix C indicates that the cumulative construction noise impact of unmitigated construction activities associated with installation of underground cable and construction of cable tunnel would cause exceedance of the daytime construction noise criterion at majority of the NSRs, up to 8892dB(A) at SR2, Pui O Lo Wai Tsuen. Mitigation measures are therefore required for these NSRs in order to alleviate the noise impacts generated from installation of the underground cable and construction of cable tunnel during the construction phase.

Table 3-11 Predicted Noise Level at Representative Noise Sensitive Receivers -– Without Mitigation (Leq30min dB(A))Unmitigated

i(

	Predicted Noise Level, at DdB(A)
NSR(s)	Pui O, Lantau				Cheung Cchau
	SR1	SR2	SR3	SR4	SR5	SR6	SR7	SR8
Daytime Construction Noise Criteria dB(A)	75	75	75	75	75	70	75	75
1. Installation of Underground Cablee
Road Breaking	886	92	86	80	7874	8884	8884	70
Trench ExecavationExcavation	831	87	81	75	N.A.77	N.A.87	N.A.87	N.A.73
Road Reinstatement	842	88	82	76	78	88	88	74
2. Construction of Cable Tunnel
General	N.A.	N.A.	N.A.	79	N.A.	N.A.	N.A.	N.A.
Site Formation	N.A.	N.A.	N.A.	82	N.A.	N.A.	N.A.	N.A.
TBM	N.A.	N.A.	N.A.	50	N.A.	N.A.	N.A.	N.A.
Drill & Blast	N.A.	N.A.	N.A.	82	N.A.	N.A.	N.A.	N.A.
Tunnel Lining	N.A.	N.A.	N.A.	72	N.A.	N.A.	N.A.	N.A.
General + Site Formation/Drill & Blast	N.A.	N.A.	N.A.	84	N.A.	N.A.	N.A.	N.A.
3. Cumulative Impact	86	92	86	85	78	88	88	74

* Bolded value means PNL exceeds the daytime construction noise criteria

* Bolded value means PNL exceeds the daytime construction noise criteria

3.4.6 Mitigation Measures

Mitigation measures for each construction site are detailed below, and the following forms of mitigation measures are recommended and should be incorporated into the Contract Specifications:

· good site practice to limit noise emissions at source

· selection of quieter plant and working methods

While it is recognised that the Contractor may develop a different package of mitigation measures to meet the required noise standards, the following suite of practical and implementable measures demonstrate an approach that would be feasible to reduce noise to acceptable levels.

Good Site Practice

Good site practice and noise management can significantly reduce the impact of construction site activities on nearby NSRs. The following package of measures should be followed during each phase of construction :

· only well-maintained plant should be operated on-site and plant should be serviced regularly during the construction works;

· machines and plant that may be in intermittent use should be shut down between work periods or should be throttled down to a minimum;

· plant known to emit noise strongly in one direction, should, where possible, be orientated to direct noise away from the NSRs;

· mobile plant should be sited as far away from NSRs as possible; and

· material stockpiles and other structures should be effectively utilised, where practicable, to screen noise from on-site construction activities.

Selecting Quieter Plant and Working Methods

The Contractor may be able to obtain particular models of plant that are quieter than standards given in GW-TM. Benefits which can be achieved through this approach will depend on the details of the Contractor chosen methods of working. As it is considered too restrictive to define specific items of plant for the construction operations, it is more 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 to suit his needs.

The nature of the construction noise sources of the project allows the introduction of a wide range of possible mitigation measures. Commonly used noise mitigation measures include:

· Application of properly designed silencers, mufflers, acoustically dampened panels and acoustic sheds or shields, etc.;

· Use of electric-powered equipment where applicable instead of diesel-powered or pneumatic-powered equipment;

· Erecting noise enclosures around noisy plants;

· Location of noise emitting plants at maximum possible distances from sensitive receivers;

· Contractual clauses for construction works;

· Schedule of noisy operations during non-restricted hours;

· Regular maintenance of site plant/ equipment; and

· A temporary cantilevered barriers of 4m high is proposed to be erected at the tunnel portal area in order to alleviate the construction noise impact by blocking the line of view from the nearby receivers. The material needs to have a surface density (>7 kg/m²) to provide sufficient screening effect (approx. 10 dB(A)).

Mitigation Measures during blasting of works (specific)

· Tunnel portal doors should be closed when the construction activities carried out within the tunnel

1^st Level of Mitigation Measure

Tables C-3 and C-4 ofin Appendix C indicated that wWith the use of quiet plant under the installation of underground cable and construction of cable tunnel, the cumulative construction noise impact at NSRs (i.e. SR1, SR2, SR3, SR4 and SR7) would slightly still exceed the daytime noise criterion (i.e. 75dB(A) for residential use) by up to 82 dB(A) as shown in Table 3-12 at NSRs (i.e. SR1, and SR2, SR3, SR4 and SR7). Due to the close proximity to the construction works, SR5 the Buddhist Wai Yan Memorial College (SR6) would be adversely affected and the predicted noise levels would exceed the daytime noise criterion (i.e. 70dB(A) for schoolsinstitutional use) by 133dB(A). Additional mitigation measures are therefore required to further reduce noise to acceptable levels. See Table 12.Details of the calculation are provided in Tables C-3 and C-4 of Appendix C.

Table 3-12 Predicted Noise Level at Representative Noise Sensitive Receivers – With Use of Quiet Plant (Leq30min dB(A))

	Predicted Noise Level, dB(A)
NSR(s)	Pui O, Lantau				Cheung Chau
	SR1	SR2	SR3	SR4	SR5	SR6	SR7	SR8
Daytime Construction Noise Criteria dB(A)	75	75	75	75	75	70	75	75
1. Installation of Underground Cable
Road Breaking	77	83	77	72	74	83	83	69
Trench Excavation	74	80	74	69	N.A.	N.A.	N.A.	N.A.
Road Reinstatement	74	80	74	69	70	80	80	66
2. Construction of Cable Tunnel
General	N.A.	N.A.	N.A.	72	N.A.	N.A.	N.A.	N.A.
Site Formation	N.A.	N.A.	N.A.	81	N.A.	N.A.	N.A.	N.A.
TBM	N.A.	N.A.	N.A.	50	N.A.	N.A.	N.A.	N.A.
Drill & Blast	N.A.	N.A.	N.A.	81	N.A.	N.A.	N.A.	N.A.
Tunnel Lining	N.A.	N.A.	N.A.	65	N.A.	N.A.	N.A.	N.A.
General + Site Formation/Drill & Blast	N.A.	N.A.	N.A.	82	N.A.	N.A.	N.A.	N.A.
3. Cumulative Impact	77	83	77	82	74	83	83	69

2^nd Level of Mitigation Measure

In addition to the above mitigation measures, a temporary vertical barriers is proposed to be erected at the tunnel portal area in order to alleviate the construction noise impact by blocking the line of view from the nearby receivers. The barrier material needs to have a surface density (> 7 kg/m²) to provide sufficient screening effect (58 to 10 dB(A) reduction). Moreover, the construction noise level produced by rock drill would be further reduced by the shielding effect of topographical constraints of the tunnel portal area (5 to 10 dB(A) reduction).

Table 3-13C-5 and C-6 ofin Appendix C demonstrated that with incorporation of quiet plant and the use of movable barrierconsideration of the effect of barrier, the cumulative noise impact at all NSRs would comply with the daytime construction noise criterion except SR5. The predicted noise levels at SR65 would still exceed the noise criterion by 58dB(A). See Table 13. Details of the calculation are provided in Tables C-5 and C-6 of Appendix C.

Table 3-13 Predicted Noise Level at Representative Noise Sensitive Receivers – With Use of Quiet Plant and Use of Movable Noise Barriers (Leq30min dB(A))

	Predicted Noise Level, dB(A)
NSR(s)	Pui O, Lantau				Cheung Chau
	SR1	SR2	SR3	SR4	SR5	SR6	SR7	SR8
Daytime Construction Noise Criteria dB(A)	75	75	75	75	75	70	75	75
1. Installation of Underground Cable
Road Breaking	69	75	69	63	64	74	74	60
Trench Excavation	69	75	69	63	N.A.	N.A.	N.A.	N.A.
Road Reinstatement	69	75	69	63	65	75	75	61
2. Construction of Cable Tunnel
General	N.A.	N.A.	N.A.	72	N.A.	N.A.	N.A.	N.A.
Site Formation	N.A.	N.A.	N.A.	72	N.A.	N.A.	N.A.	N.A.
TBM	N.A.	N.A.	N.A.	50	N.A.	N.A.	N.A.	N.A.
Drill & Blast	N.A.	N.A.	N.A.	72	N.A.	N.A.	N.A.	N.A.
Tunnel Lining	N.A.	N.A.	N.A.	65	N.A.	N.A.	N.A.	N.A.
General + Site Formation/Drill & Blast	N.A.	N.A.	N.A.	75	N.A.	N.A.	N.A.	N.A.
3. Cumulative Impact	69	75	69	75	65	75	75	61

* Bolded value means PNL exceeds the daytime construction noise criteria

With the implementation of appropriate and sufficient noise mitigation measures, it is envisaged that the potential construction noise impact at all other NSRs can be substantially minimised. Details of the noise mitigation measures shall be formulated based on the conclusions of this EIA Report. The effectiveness and continuous implementation of the noise mitigation measures shall be checked by an audit programme which can help protecting the nearby NSRs through the provision of regular feedback to the site contractors.

3.4.7 Residual Impacts

According to the predicted results of the mitigated noise with two levels of mitigation measures as shown in Table 3-13C-5 and C-6 ofin Appendix C, there is still an exceedance of noise level by 5dB(A) at SR65, the Buddhist Wai Yan Memorial College. As the noisiest activity in front of SR65 is road breaking and road reinstatement, the high noise level at this receiver only exists for a few days (2 to 3 days). Short duration of this residual impact could be mitigated by scheduling the construction works at SR65 on Saturday (non-teaching period) or school holidays.

3.4.8 Environmental Monitoring & Audit

Laying underground cables is a typical installation and CLP has established good trade practices for this work such that they minimise the construction noise and dust impacts. With the implementation of noise mitigation measures and scheduling the construction activities in front of the school, full compliance with the environmental criteria is expected to be achieved. Therefore, routine environmental monitoring for construction noise is not required during the construction phase. Regular site audits are however recommended to be conducted to ensure the effectiveness of these good site practices and appropriate mitigation measures.

3.4.9 Conclusions

The unmitigated noise levels associated with the installation of underground cable and construction of cable tunnel, would cause exceedance of the daytime construction noise criterion at the nearby NSRs. The most seriously affected area is Ham Tin Tsuen of Pui O, Lantauthe Buddhist Wai Yan Memorial College (SR5) where unmitigated noise level of up to 9288 dB(A) is predicted. Therefore, adequate control measures will be necessary for the installation of underground cable and construction of cable tunnel. Mitigation measures including the use of quiet plant and consideration of barrier effect are proposed to substantially minimise the noise level. Although the noise impact at all NSR would comply with the daytime construction noise criterion (ie 75 dB(A) for domestic premises),mitigated noise level reduces to 78 dB(A), it still exceeds the noise criteria the Buddhist Wai Yan Memorial College (ie SR6) would still exceed the noise criteria (ie 70 dB(A) for schools) by 5 dB(A). By considering the short duration of this residual impact, re-scheduling the construction works at SR65 on Saturday (non-teaching period) or school holidays could minimise the noise impacts. Therefore, the residual noise impact could be alleviated.

For the construction of the tunnel, numerous of noisy PMEs such as jumbo drilling machine and rock bolt jumbo are involved. Construction noise impact at the nearby NSRs is expected. With the erection of the temporary vertical noise barrier at Pui O tunnel portal and adoption of quiet plants, the construction noise impact can be alleviated. The predicted noise levels with mitigation can comply with the noise criteria.

As noise exceedances during the construction phase are not predicted and the laying underground land cable is a trade practice well established by CLP, routine environmental noise monitoring is not required during construction. However regular site audits are recommended to be conducted to ensure the implementation of good site practice and appropriate mitigation measures.

By comparing the assessment results for construction of cable tunnel with TBM and drill & blast method, the construction noise impacts at the nearby sensitive receivers are acceptable for both methods with the implementation of mitigation measures. Although TBM is the envisaged option based on the finding, both TBM and the drill & blast method are also feasible and comply with the daytime noise criteria.

3.5 Impact on Loss of Groundwater

Site investigations have been conducted to identify the ground condition in Chi Ma Wan Peninsula along the proposed cable alignment. The investigation revealed that the proposed tunnelling will have negligible effect on the water catchment yield and is unlikely to cause any significant drawndown of the groundwater profile and as a result it does not affect existing plantation within the study area. However, as a preventive measure, monitoring points are proposed at appropriate locations to monitor any change of the ground water profile during the construction period.

The purpose of the groundwater monitoring is to:-

· monitor the existing ground water table, in case of any substantial change or abnormal loss of groundwater, mitigation measures could be implemented at the first instance; and

· implement mitigation measures wherever appropriate to prevent further groundwater inflow into the proposed cable tunnel and to alleviate the drawdown effect which although unlikely has the potential to affect the existing plantation.

The proposed tunnel is located approximately 120m below the ground surface in Chi Ma Wan Peninsula. The estimated catchment affected by the proposed tunnel will be approximately 390,000m² based on a 400m zones of influence as described in McFeat et al, 1998. The water inflow into the proposed cable tunnel will depend on the amount of rock joints, types of joint infill and aperture thickness. Major water inflows occur where fracture zones and open joints are encountered. It is recommended that groundwater monitoring points are installed at shallow cover locations such as in Lung Mei and where fracture zones and open joints are anticipated.

3.5.1 Mitigation Measures

In case any substantial and abnormal changes in the ground water table are observed from the monitoring point as a result of groundwater inflow into the proposed cable tunnel, mitigation measures as outlined below are recommended to prevent further groundwater loss. The mitigation measures include:-

· traditional pre-injection systems using cement grout will be applied in the identified fault intersection zone to reduce the water inflow, if necessary; and

· apply 2mm thick typical high performance PVC waterproof membrane and geotextile fleece mats as suggested in the tunnel preliminary design report to ensure watertighteness of the tunnel.

3.5.2 Environmental Monitoring & Audit

In order to ensure no ground water loss during the cable tunnelling work, monitoring of ground water table as specified in section 4 of the EM&A Manual and the monitoring requirements as defined below will be specified in the Contract Document. The monitoring requirements during construction period include:-

· The contractor is required to submit a layout plan showing the proposed locations groundwater monitoring points to the satisfaction of EPD;

· The contractor is required to submit method statements for the proposed mitigation measures to prevent further ground water inflow into the proposed cable tunnel to the satisfaction of EPD, the mitigation measures are:-

(i) pre-injection system using approved cement grout and any equivalent approved methods and/or proprietary products which could achieve the same performance and purpose; and

(ii) lining and waterproof membrane for the cable tunnel.