Figure 1.1:	Location of the Project
Figure 2.1:	Locations of Air Quality Monitoring Stations
Figure 3.1:	Locations of Noise Monitoring Stations
Figure 4.1:	Locations of Marine Water Quality Monitoring Stations

Tables

Table 2.1: Air Quality Monitoring Stations 4

Table 2.2: Equipment Used during the Baseline Air Quality Monitoring 5

Table 2.3: Summary of Baseline Air Quality Monitoring Results 6

Table 2.4: Derivation Criteria for Action and Limit (A/L) Levels for Air Quality 7

Table 2.5: Action and Limit Levels for Air Quality 7

Table 2.6: Event and Action Plan for Air Quality 8

Table 3.1: Noise Monitoring Stations 11

Table 3.2: Equipment Used during the Baseline Noise Monitoring 12

Table 3.3: Baseline Noise Monitoring Parameters, Frequency and Period 13

Table 3.4: Summary of Baseline Noise Monitoring Results - Normal Weekday Daytime (0700-1900 hrs) 14

Table 3.5: Summary of Baseline Noise Monitoring Results - Evening on Normal Weekday (1900-2300) and Sunday/Public Holiday (0700-2300 hrs) 14

Table 3.6: Summary of Baseline Noise Monitoring Results - Night-time (2300-0700 hrs) 14

Table 3.7: Action and Limit Levels for Construction Noise 15

Table 3.8: Event and Action Plan for Construction Noise 16

Table 4.1: Marine Water Quality Monitoring Stations for the Marine Viaduct for Baseline Monitoring 18

Table 4.2: Baseline Marine Water Quality Monitoring Equipment 19

Table 4.3: Multifunctional Meters Used during the Baseline Water Quality Monitoring 19

Table 4.4: Baseline Water Quality Monitoring Frequency and Period 20

Table 4.5: Summary of Baseline Water Quality Monitoring Result 21

Table 4.6: ANOVA Test Results for Turbidity and SS 21

Table 4.7: Determination Criteria for Action and Limit Levels for Marine Water Quality 22

Table 4.8: Corresponding Control and Impact Monitoring Stations during Impact Monitoring 22

Table 4.9: Derived Action and Limit Levels for IM2, IM3, and SR3 23

Table 4.10: Event and Action Plan for Marine Water Quality 24

Executive summary

In February 2025, Mott MacDonald Hong Kong Limited (MMHK) was commissioned by AAHK under Contract C24C02 to provide Environmental Team (ET) consultancy services for implementation of an EM&A programme in accordance with the Environmental Permit (EP) requirements throughout the Pre-construction, Construction and Post-construction phases of the Project.

This Baseline Monitoring Report presents the monitoring works conducted from 26 February 2025 to 2 July 2025 in order to fulfil Condition 3.3 of the EP (EP-630/2023) and Section 12.2 of the Environmental Monitoring and Audit (EM&A) Manual of the Airport Tung Chung Link Project.

Baseline Air Quality Monitoring

Baseline air quality monitoring (1-hour TSP) was carried out at the three designated monitoring locations (namely AM1a, AM2 and AM3) from 31 March 2025 to 13 April 2025 (for AM2 & AM3) and from 4 to 17 June 2025 (for AM1a).

Overall, the baseline air quality results are considered representative to the ambient air quality of the Project and were used to establish the Action and Limit Levels for air quality.

Baseline Noise Monitoring

Baseline noise monitoring was carried out at the five designated monitoring locations (namely NM1, NM2, NM3, NM4 and NM5). Summary of baseline noise monitoring period is shown below:

· NM1: from 31 March 2025 to 11 April 2025; and from 13 to 16 April 2025.

· NM2: from 31 March 2025 to 4 April 2025; from 7 to 11 April 2025; and from 14 to 20 April 2025.

· NM3: from 2 to 11 April to 2025; and from 13 to 18 April 2025.

· NM4: from 26 May 2025 to 9 June 2025.

· NM5: from 31 March 2025 to 11 April 2025; and from 13 to 16 April 2025

Overall, the baseline noise monitoring period has captured at least 14 sets of background noise for both daytime, evening time and night time periods at the noise monitoring stations, therefore, the measured noise data at the five measured monitoring locations is considered representative of the baseline conditions for the Project.

Baseline Water Quality Monitoring

The baseline water quality monitoring was conducted three days per week for four weeks from 26 February to 24 March 2025 (dry season) and from 2 June to 2 July 2025 (wet season), at mid-flood and mid-ebb tides, at 5 water quality monitoring stations. Monitoring of dissolved oxygen (DO), dissolved oxygen saturation (DO%), pH, water depth, temperature, turbidity, salinity and suspended solids (SS) were undertaken at all monitoring stations. As no pertinent activities were observed in the vicinity of the monitoring stations during the baseline monitoring that would affect the monitoring results, the water quality monitoring results obtained are considered to be appropriate for adoption as the baseline water quality dataset for the Project.

The Action and Limit levels for water quality impact monitoring at impact stations were derived based on the baseline water quality monitoring conducted in February, March, June and July 2025.

1 Introduction

1.1 Background

The Airport Authority Hong Kong (‘AAHK’) is planning to construct a dedicated road, named as the Airport Tung Chung Link (‘ATCL’), to extend the passenger transport services using autonomous vehicles (‘AV’) from the Airportcity Link (‘ACL’), which is currently under construction, to Tung Chung, aiming to enhance connectivity between the Hong Kong Port (‘HKP’), SKYCITY and Tung Chung.

Construction of ATCL is a part of the scope of the designated project, named as the Airport Tung Chung Link Project (‘ATCL Project’), under Environmental Impact Assessment Ordinance (‘EIAO’) and has obtained an Environmental Permit No. EP-630/2023 (hereafter referred to as ‘ATCL Project EP’). The ATCL Project Environmental Impact Assessment Report (‘EIAR’) (Register No. AEIAR-254/2023) was approved by the Director of Environmental Protection (‘DEP’) and the ATCL Project EP No. EP-630/2023 was granted by DEP on 26 October 2023.

The marine facilities in the waters between Airport Island and HKP Island are included in the ATCL Project EIAR (Register No. AEIAR-254/2023) and the ATCL Project EP (EP No. EP-630/2023), however, the construction of marine facilities and spur line of ATCL (including Academy Station) are not included in the current stage of ATCL construction. The alignment of ATCL is shown in Figure 1.1.

In February 2025, Mott MacDonald Hong Kong Limited (MMHK) was commissioned by AAHK under Contract C24C02 to provide Environmental Team (ET) consultancy services for implementation of an EM&A programme in accordance with the ATCL Project EP requirements throughout the Pre-construction, Construction and Post-construction phases of the ATCL Project.

1.2 Purpose of the Baseline Monitoring Report

This Baseline Monitoring Report aims to present the baseline levels of air quality, noise and water quality in the vicinity of the Project area before the commencement of construction works of the ATCL Project, in accordance with ATCL Project EP Condition 3.3 and Section 12.2 of the Environmental Monitoring and Audit Manual (‘EM&A Manual’) of this ATCL Project. An updated submission would be provided for the construction of marine facilities and spur line of ATCL (including Academy Station) before commencement of construction of the relevant works in accordance with the requirements as stipulated in ATCL Project EP Condition 3.3 and EM&A Manual Section 12.2.

This report summarises the locations of the baseline monitoring stations, monitoring methodologies, monitoring results, observations during the baseline monitoring; as well as the determination of Action and Limit Levels for each monitoring parameter with statistical analysis of the baseline data.

1.3 Structure of the Baseline Monitoring Report

The structure of the Baseline Monitoring Report is as follows:

· Section 1 - Introduction - background of the ATCL Project, purpose and structure of the report

· Section 2 - Air Quality - presents the baseline monitoring requirements with results of the baseline air quality monitoring, and the determination of the respective Action and Limit Levels for the subsequent impact air quality monitoring

· Section 3 - Noise - presents the baseline monitoring requirements with results of the baseline noise monitoring

· Section 4 - Water Quality - presents the baseline monitoring requirements with results of the baseline water quality monitoring, and the determination of the respective Action and Limit Levels for the subsequent impact water quality monitoring

· Section 5 - Conclusion - summarises the baseline monitoring results for air quality, noise and water quality.

2 Air Quality

2.1 Monitoring Requirement

According to the Section 3.2.19 in the EM&A Manual of the ATCL Project, baseline air quality monitoring should be carried out at designated monitoring locations for at least two weeks prior to the commencement of the major construction works for the ATCL Project to obtain the ambient 1-hour Total Suspended Particulate (TSP) sample. Ambient 1-hour sampling should be done at least 3 times per day at each monitoring station. Further details of the baseline air quality monitoring are presented in the following sections.

2.1.1 Monitoring Parameters

1-hour TSP levels have been measured during baseline air quality monitoring in accordance with the ATCL Project EM&A Manual. The monitoring information (e.g. monitoring date, monitoring time, weather conditions, dust source(s), other specific phenomena) was recorded in the data record sheet during the monitoring.

2.1.2 Monitoring Locations

The proposed air quality monitoring locations for baseline air quality monitoring are summarised in Table 2.1 and shown in Figure 2.1. Photographs of the monitoring equipment set up at baseline monitoring stations are given in Appendix A1.

Table 2.1: Air Quality Monitoring Stations

ID	ASR ID adopted in EIA Report	Description	Monitoring Parameter	Monitoring Level
AM1a ⁽¹⁾	---	Tat Tung Road Garden	1-hour TSP	Ground Floor
AM2	A11	Hong Kong Airlines Training Academy	1-hour TSP	Ground Floor
AM3	A10	CNAC House	1-hour TSP	Podium

Remark:

(1) As advised by the Leisure and Cultural Services Department, Tung Chung Community Garden (original monitoring station ID: AM1; ASR ID: A20) as stipulated in Table 3.1 of the ATCL Project EM&A Manual has been decommissioned and hence not accessible. Therefore, Tat Tung Road Garden which located next to the Tung Chung Community Garden is proposed to be the alternative air quality monitoring station. The proposed alternative location was agreed by the Independent Environmental Checker (‘IEC’) and AAHK on 3 April 2025 and approved by EPD on 2 June 2025.

Air quality monitoring station, AM4, which is designated in the ATCL Project EM&A Manual for the proposed marine facilities during construction phase is not included in this report, as the construction of marine facilities is not part of the current stage of ATCL construction (refer to Section 1.1).

2.1.3 Monitoring Equipment and Methodology

1-hour TSP levels shall be measured by following the standard high volume sampling method as set out in the Part 50 Chapter 1 Appendix B, Title 40 of the Code of Federal Regulations of the USEPA. Alternatively, upon approval of the Independent Environmental Checker (‘IEC’), 1-hour TSP levels can be measured by direct reading method which are capable of producing comparable results as that by the high volume sampling method, to indicate short event impacts.

For this ATCL Project, direct reading method by the use of portable direct reading dust meters (e.g. Sibata model no. LD-3B and LD-5R) were proposed to be used for baseline monitoring based on the provisions set out in Section 3.2.7 of the ATCL Project EM&A Manual. The proposal for adopting direct reading method by the use of portable direct reading dust meters was submitted to the IEC on 14 March 2025 as enclosed in the Air Quality and Noise Monitoring Proposal, which was approved by the IEC on 21 March 2025.

Table 2.2 summarises the equipment used in the baseline air quality monitoring. Copies of the calibration certificates for the equipment used during the baseline air quality monitoring are attached in Appendix A2. The portable direct reading dust meter will be calibrated every year against High Volume Sampler (HVS) to check the validity and accuracy of the results measured by direct reading method.

Table 2.2: Equipment Used during the Baseline Air Quality Monitoring

Monitoring Station	Equipment	Model
AM1a	Portable direct reading dust meter	SIBATA LD-5R (serial no. 781281)
AM2		SIBATA LD-3B (serial no. 456666)
AM3		SIBATA LD-5R (serial no. 781281)

The measuring procedures of the portable direct reading dust meter are followed in accordance with the Manufacturer’s Instruction Manual as presented below:

1-hour TSP Monitoring

SIBATA model no. LD-3B

a) set POWER to ‘ON’ and make sure that the battery level was not flash or in low level;

b) pull the air sampling inlet cover up;

c) push the knob at [MEASURE] position;

d) set time/mode setting to [BG] by pushing the time setting switch;

e) start the background measurement by pushing the Start/Stop switch once;

f) turn knob to [SENSI. ADJ] position and push Start/Stop switch once to start the span check;

g) gently return knob to the [MEASURE] position;

h) push the time setting switch to change the time setting display to [LOG];

i) remove the cap and start measurement.

SIBATA model no. LD-5R

a) turn ON the power switch;

b) close the air sampling port cap;

c) turn the scattering plate knob to [MEASURE];

d) perform the BG measurement (8 seconds + 6 seconds);

e) turn the scattering plate knob to [SENSI. ADJ.];

f) perform the SPAN measurement (60 seconds);

g) turn the scattering plate knob to [MEASURE];

h) open the air sampling port cap;

i) select the measurement mode;

j) start the measurement;

k) finish the measurement (automatically or manually);

l) close the air sampling port cap;

m) perform the BG measurement (8 seconds + 6 seconds);

n) turn OFF the power switch

2.1.4 Monitoring Frequency and Duration

The baseline air quality monitoring for 1-hour TSP sampling at AM2 and AM3 was undertaken at least 3 times per day for at least 14 consecutive days from 31 March to 13 April 2025. The baseline air quality monitoring for 1-hour TSP sampling at AM1a was undertaken at least 3 times per day for at least 14 consecutive days from 4 to 17 June 2025. The baseline air quality monitoring schedule is presented in Appendix A3.

2.2 Monitoring Results and Analysis

The baseline air quality monitoring was carried out at AM2 and AM3, from 31 March 2025 to 13 April 2025, and at AM1a from 4 to 17 June 2025, for a total of 14 days. During the baseline air quality monitoring, there were no major construction or dust generation activities in the vicinity of the monitoring stations.

2.2.1 Weather Data

It is considered that the wind data obtained at the existing Hong Kong Observatory’s (HKO) Chek Lap Kok wind station is representative of the Project area and could be used for undertaking the baseline and impact air quality monitoring programme for the ATCL Project. The proposed use of the existing wind data collected from Chek Lap Kok wind station for wind data collection instead of setting up wind monitoring equipment near the monitoring stations was proposed by the ET Leader on 14 March 2025 as enclosed in the Air Quality and Noise Monitoring Proposal and agreed by the IEC on 21 March 2025, in accordance with the requirements stated in Section 3.2.9 of the ATCL Project EM&A Manual.

Wind data collected from the Chek Lap Kok wind station was used for the air quality monitoring and is presented in Appendix A4. During the baseline air quality monitoring period (i.e. 31 March 2025 to 13 April 2025, and 4 to 17 June 2025), the weather typically varied between cloudy and sunny conditions, with no observable precipitation during the monitoring timeslot.

According to the Hong Kong Observatory, there was an influence of the associated intense and dry northeast monsoon, with strong northerly winds also affected many parts of Hong Kong on 12 and 13 April 2025, with winds occasionally reaching gale force offshore and on high ground. The intense monsoon also transported sand and dust southwards from Mongolia and brought widespread sandstorms to many inland areas in China. Under the influence of the very dry continental airstream and the sand and dust weather, the level of Hong Kong's suspended particulates surged since 12 April 2025 nighttime under the influence of a dusty air stream associated with the northeast monsoon.

2.2.2 Monitoring Results and Statistical Analysis of the Results

The detailed monitoring data and graphical presentation of the results are presented in Appendix A5, and Table 2.3 summarises the baseline air quality monitoring results.

Table 2.3: Summary of Baseline Air Quality Monitoring Results

Monitoring Station	Average 1 hour TSP (μg/m³)	Range (μg/m³)
AM1a	31	19 - 50
AM2	37	20 - 120
AM3	38	20 - 116

2.2.3 Determination of Action and Limit Levels (A/L Levels)

The Action and Limit Levels for 1-hour TSP have been derived in accordance with the derivation criteria specified in Section 3.2.26 of the ATCL Project EM&A Manual which is presented in Table 2.4 below.

Table 2.4: Derivation Criteria for Action and Limit (A/L) Levels for Air Quality

Parameter	Action Level (μg/m³)	Limit Level (μg/m³)
1-hour TSP Level in μg/m³	BL ≤ 384 μg/m³, AL = (BL x 1.3 + LL)/2 BL > 384 μg/m³, AL = LL	500

Parameter

Action Level (μg/m³)

Limit Level (μg/m³)

1-hour TSP Level in μg/m³

BL ≤ 384 μg/m³, AL = (BL x 1.3 + LL)/2

BL > 384 μg/m³, AL = LL

500

Note: BL: Baseline level; AL: Action level; LL: Limit level

Following the criteria as set out in Table 2.4, the Action and Limit Levels for Air Quality for AM1a, AM2 and AM3 are derived and presented in Table 2.5.

Table 2.5: Action and Limit Levels for Air Quality

Parameter	Monitoring Station	Action Level (μg/m³)	Limit Level (μg/m³)
1-hour TSP Level in μg/m³	AM1a	270	500
	AM2	274	500
	AM3	275	500

2.2.4 Event and Action Plan

Should non-compliance of the air quality criteria occur, actions in accordance with the Event and Action Plan in Table 2.6 shall be carried out.

Table 2.6: Event and Action Plan for Air Quality

Event	Action
Action level exceedance for one sample	· Repeat measurement to confirm finding; · If exceedance is confirmed, inform Contractor, IEC and AAHK /PM. · Identify sources, investigate the causes of exceedance and propose remedial measures. · Discuss with the Contractor, IEC and AAHK/PM on the remedial measures required. · Increase monitoring frequency to daily.	· Check monitoring data submitted by ET. · Check Contractor’s working methods. · Discuss with ET, AAHK/PM and Contractor on possible remedial measures. · Review and advise ET and AAHK/PM on the effectiveness of the proposed remedial measures.	· Confirm receipt of notification of exceedance in writing.	· Identify source(s), investigate the causes of exceedance and propose remedial measures. · Implement remedial measures. · Amend working methods agreed with the AAHK/PM as appropriate.
Action level exceedance for two or more consecutive samples	· Repeat measurements to confirm findings. · If exceedance is confirmed, inform Contractor, IEC and AAHK /PM. · Identify sources, investigate the causes of exceedance and propose remedial measures. · Advise the Contractor and AAHK/PM on the effectiveness of the proposed remedial measures; · Increase monitoring frequency to daily. · If exceedance continues, arrange meeting with the IEC, Contractor and AAHK/PM to discuss measures to be taken. · If exceedance stops, cease additional monitoring.	· Check monitoring data submitted by ET. · Check the Contractor’s working methods. · Discuss with the ET, AAHK/PM and Contractor on possible remedial measures. · Review and advise ET, AAHK/PM on the effectiveness of proposed remedial measures.	· Confirm receipt of notification of exceedance in writing. · In consultation with ET and IEC agree with Contractor on the remedial measures to be implemented. · Supervise implementation of remedial measures.	· Identify source(s), investigate the causes of exceedance and propose remedial measures. · Submit proposals for remedial measures to AAHK/PM, ET and IEC within 3 working days of notification for agreement. · Implement the agreed proposals. · Amend proposal as appropriate.
Limit level exceedance for one sample	· Repeat measurement to confirm finding. · If exceedance is confirmed, inform IEC, AAHK/PM, Contractor and EPD. · Increase monitoring frequency to daily. · Discuss with the AAHK/PM, IEC and Contractor on the remedial measures and assess effectiveness. · Keep IEC, AAHK/PM and EPD informed of the results of the effectiveness of remedial measures.	· Check monitoring data submitted by ET. · Check Contractor’s working methods. · Discuss with the ET, AAHK/PM and Contractor on possible remedial measures. · Review and advise ET and AAHK/PM on the effectiveness of the proposed remedial measures.	· Confirm receipt of the notification of exceedance in writing. · Review and agree on the remedial measures proposed by Contractor. · Ensure remedial measures are properly implemented. · Supervise implementation of remedial measures.	· Identify source(s), investigate the causes of exceedance and propose remedial measures. · Take immediate action to avoid further exceedance. · Submit proposals for remedial measures to AAHK/PM, ET and IEC within 3 working days of notification for agreement. · Implement the agreed proposals. · Amend proposals as appropriate.
Limit level exceedance for two or more consecutive samples	· Repeat measurements to confirm findings. · If exceedance is confirmed, inform IEC, AAHK/PM, Contractor and EPD. · Increase monitoring frequency to daily. · Carry out analysis of the Contractor’s working procedures to determine the possible mitigation to be implemented. · Arrange meeting with IEC and AAHK/PM to discuss the remedial measures to be taken. · Assess the effectiveness of the Contractor’s remedial measures and keep the IEC, EPD and AAHK/PM informed of the results. · If exceedance stops, cease additional monitoring.	· Check monitoring data submitted by ET · Discuss amongst AAHK/PM, ET and Contractor on the potential remedial measures. · Review the Contractor’s remedial action whenever necessary to assure their effectiveness and advise AAHK/PM and ET accordingly.	· Confirm receipt of the notification of exceedance in writing. · In consultation with IEC and ET, agree with Contractor on the remedial measures to be implemented. · Supervise the implementation of remedial measures to be implemented. · If exceedance continues, consider what portion of works is responsible and instruct the Contractor to stop that portion of works until the exceedance is abated.	· Identify source(s), investigate the causes of exceedance and propose remedial measures. · Take immediate action to avoid further exceedance. · Submit proposals for remedial measures to the AAHK/PM and copy to the IEC and ET within 3 working days of notification. · Implement the agreed proposals. · Review and resubmit proposals if problems still not under control. · Stop the relevant portion of works as determined by AAHK/PM until the exceedance is abated.

Event

Action

IEC

AAHK/PM

Contractor

Action level exceedance for one sample

· Repeat measurement to confirm finding;

· If exceedance is confirmed, inform Contractor, IEC and AAHK /PM.

· Identify sources, investigate the causes of exceedance and propose remedial measures.

· Discuss with the Contractor, IEC and AAHK/PM on the remedial measures required.

· Increase monitoring frequency to daily.

· Check monitoring data submitted by ET.

· Check Contractor’s working methods.

· Discuss with ET, AAHK/PM and Contractor on possible remedial measures.

· Review and advise ET and AAHK/PM on the effectiveness of the proposed remedial measures.

· Confirm receipt of notification of exceedance in writing.

· Identify source(s), investigate the causes of exceedance and propose remedial measures.

· Implement remedial measures.

· Amend working methods agreed with the AAHK/PM as appropriate.

Action level exceedance for two or more consecutive samples

· Repeat measurements to confirm findings.

· If exceedance is confirmed, inform Contractor, IEC and AAHK /PM.

· Identify sources, investigate the causes of exceedance and propose remedial measures.

· Advise the Contractor and AAHK/PM on the effectiveness of the proposed remedial measures;

· Increase monitoring frequency to daily.

· If exceedance continues, arrange meeting with the IEC, Contractor and AAHK/PM to discuss measures to be taken.

· If exceedance stops, cease additional monitoring.

· Check monitoring data submitted by ET.

· Check the Contractor’s working methods.

· Discuss with the ET, AAHK/PM and Contractor on possible remedial measures.

· Review and advise ET, AAHK/PM on the effectiveness of proposed remedial measures.

· Confirm receipt of notification of exceedance in writing.

· In consultation with ET and IEC agree with Contractor on the remedial measures to be implemented.

· Supervise implementation of remedial measures.

· Identify source(s), investigate the causes of exceedance and propose remedial measures.

· Submit proposals for remedial measures to AAHK/PM, ET and IEC within 3 working days of notification for agreement.

· Implement the agreed proposals.

· Amend proposal as appropriate.

Limit level exceedance for one sample

· Repeat measurement to confirm finding.

· If exceedance is confirmed, inform IEC, AAHK/PM, Contractor and EPD.

· Increase monitoring frequency to daily.

· Discuss with the AAHK/PM, IEC and Contractor on the remedial measures and assess effectiveness.

· Keep IEC, AAHK/PM and EPD informed of the results of the effectiveness of remedial measures.

· Check monitoring data submitted by ET.

· Check Contractor’s working methods.

· Discuss with the ET, AAHK/PM and Contractor on possible remedial measures.

· Review and advise ET and AAHK/PM on the effectiveness of the proposed remedial measures.

· Confirm receipt of the notification of exceedance in writing.

· Review and agree on the remedial measures proposed by Contractor.

· Ensure remedial measures are properly implemented.

· Supervise implementation of remedial measures.

· Identify source(s), investigate the causes of exceedance and propose remedial measures.

· Take immediate action to avoid further exceedance.

· Submit proposals for remedial measures to AAHK/PM, ET and IEC within 3 working days of notification for agreement.

· Implement the agreed proposals.

· Amend proposals as appropriate.

Limit level exceedance for two or more consecutive samples

· Repeat measurements to confirm findings.

· If exceedance is confirmed, inform IEC, AAHK/PM, Contractor and EPD.

· Increase monitoring frequency to daily.

· Carry out analysis of the Contractor’s working procedures to determine the possible mitigation to be implemented.

· Arrange meeting with IEC and AAHK/PM to discuss the remedial measures to be taken.

· Assess the effectiveness of the Contractor’s remedial measures and keep the IEC, EPD and AAHK/PM informed of the results.

· If exceedance stops, cease additional monitoring.

· Check monitoring data submitted by ET

· Discuss amongst AAHK/PM, ET and Contractor on the potential remedial measures.

· Review the Contractor’s remedial action whenever necessary to assure their effectiveness and advise AAHK/PM and ET accordingly.

· Confirm receipt of the notification of exceedance in writing.

· In consultation with IEC and ET, agree with Contractor on the remedial measures to be implemented.

· Supervise the implementation of remedial measures to be implemented.

· If exceedance continues, consider what portion of works is responsible and instruct the Contractor to stop that portion of works until the exceedance is abated.

· Identify source(s), investigate the causes of exceedance and propose remedial measures.

· Take immediate action to avoid further exceedance.

· Submit proposals for remedial measures to the AAHK/PM and copy to the IEC and ET within 3 working days of notification.

· Implement the agreed proposals.

· Review and resubmit proposals if problems still not under control.

· Stop the relevant portion of works as determined by AAHK/PM until the exceedance is abated.

Note: ET - Environmental Team; PM - Project Manager; IEC - Independent Environmental Checker; AAHK - Airport Authority Hong Kong

3 Noise

3.1 Monitoring Requirement

According to Section 4.3.8 in the ATCL Project EM&A Manual, baseline noise monitoring shall be carried out at the construction noise monitoring locations for a continuous period of at least 14 consecutive days at a minimum logging interval of 30 minutes during the daytime between 0700-1900, and 5 minutes between 1900 and 0700 as well as all time at general holidays including Sundays.

The baseline monitoring methodology for noise, including the monitoring parameters, monitoring locations, equipment used, methodology, and duration etc., are detailed in the following sections.

3.1.1 Monitoring Parameters

Construction noise level should be measured in terms of the A-weighted equivalent continuous sound pressure level (L_eq). L_eq_(30min)shall be used as the monitoring parameter for the time period between 0700 and 1900 hours on normal weekdays. For all other time periods, L_eq_(5min)shall be employed for comparison with the Noise Control Ordinance (NCO) criteria. As supplementary information for data auditing, statistical results such as L₁₀ and L₉₀ were also obtained for reference.

3.1.2 Monitoring Locations

The proposed noise monitoring locations for baseline monitoring are summarised in Table 3.1 and shown in Figure 3.1. Photographs of the monitoring equipment set up at baseline monitoring stations are given in Appendix B1.

Table 3.1: Noise Monitoring Stations

Monitoring Station ID	Representative NSR ID in EIA Report	Description	Monitoring Level	Type of Measurement
NM1	N01	Seaview Crescent	Roof-top of Block 1 (Direction: SW)	Façade measurement
NM2	N03	Ling Liang Church E Wun Secondary School	Roof-top (Direction: W)	Façade measurement
NM3	N08	Fu Tung Estate Tung Ma House	Roof-top (Direction: N)	Façade measurement
NM4	N09	Tung Chung Crescent	Roof-top of Block 5 (Direction: NE)	Façade measurement
NM5⁽¹⁾	N10	Priests’ Quarters of the Planned Visitation Church Development	Next to the lamp post (ID: FC3075) with 1.2 m above ground (Direction: NE)	Free-field measurement

Remark:

(1) The Priests’ Quarters of the Planned Visitation Church Development is still under construction during the baseline noise monitoring period. NM5 is located at the planned Visitation Church Development site boundary with the direction towards ATCL project work area, and is considered best representing the baseline condition of the planned NSR. Subject to the construction programme of the planned NSR, its impact monitoring station will be reviewed when necessary.

In accordance with Section 4.3.7 of the ATCL Project EM&A Manual, the monitoring station shall normally be at a point 1m from the exterior of the sensitive receiver building facade and be at a position 1.2m above the ground. If there is problem with access to the normal monitoring position, an alternative position may be chosen, and a correction to the measurements shall be made. For reference, a correction of +3 dB(A) shall be made to the free field measurements. The ET shall agree with the IEC on the monitoring position and the corrections adopted. Once the positions for the monitoring stations are chosen, the baseline monitoring and the impact monitoring shall be carried out at the same positions.

The ET may, depending on site conditions and monitoring results, decide whether additional monitoring locations shall be included or any monitoring locations could be removed / relocated during any stage of the construction phase. Any changes on monitoring locations should be proposed and submitted for IEC review.

3.1.3 Monitoring Equipment and Methodology

Hand-held sound level meters (e.g. Rion model no. NL-52 and NL-53) were used for baseline monitoring. Sound level meters in compliance with the International Electrotechnical Commission Publications 651:1979 (Type 1) and 804:1985 (Type 1) specifications shall be used for carrying out the noise monitoring. Immediately prior to and following each noise measurement, the accuracy of the sound level meter was checked using an acoustic calibrator generating a known sound pressure level at a known frequency (e.g. Larson Davis model no. CAL200). The noise measurements were made in accordance with standard acoustical principles and practices in relation to weather conditions. Measurements would be accepted as valid only if the calibration level from before and after the noise measurement agrees to within 1.0 dB.

Table 3.2 summarises the equipment used in the baseline noise monitoring. Copies of the calibration certificates for the equipment used during the baseline noise monitoring are attached in Appendix B2.

Table 3.2: Equipment Used during the Baseline Noise Monitoring

Monitoring Station	Equipment
Monitoring Station	Sound Level Meter	Acoustic Calibrator
NM1	Rion NL-53 (serial no. 01141566)	Larson Davis CAL200 (serial no. 16878)
NM2	Rion NL-53 (serial no. 01141565)
NM3	Rion NL-52 (serial no. 00175561)
NM4	Rion NL-53 (serial no. 01141565)
NM5	Rion NL-52 (serial no. 00542913)

3.1.4 Monitoring Frequency and Duration

Baseline noise monitoring was carried out at NM1, NM2, NM3 and NM5 from 31 March 2025 to 20 April 2025, and at NM4 from 26 May 2025 to 9 June 2025, prior to the commencement of the construction works. Continuous baseline noise monitoring for the A-weighted levels L_eq, L₁₀ and L₉₀ was carried out daily for a period of at least 14 consecutive days at a minimum logging interval of 30 minutes during the daytime between 0700-1900, and 5 minutes between 1900 and 0700 as well as all time at general holidays including Sundays, in accordance with the ATCL Project EM&A Manual. No construction activities were undertaken in the vicinity of the monitoring stations during the baseline monitoring.

Table 3.3 summarises the monitoring parameters, frequency, duration and periods of the baseline noise monitoring. The baseline noise monitoring schedule is provided in Appendix B3.

Table 3.3: Baseline Noise Monitoring Parameters, Frequency and Period

Monitoring Station	Parameter	Frequency	Monitoring Periods
NM1	L_eq_,L_10, L₉₀	Continuous Monitoring	· 31 March - 11 April 2025; and · 13 - 16 April 2025 ⁽¹⁾
NM2			· 31 March - 4 April 2025; · 7 - 11 April 2025; ⁽²⁾and · 14 - 20 April 2025 ⁽³⁾
NM3			· 2 - 11 April 2025; and · 13 - 18 April 2025 ⁽¹⁾
NM4			· 26 May - 9 June 2025
NM5			· 31 March - 11 April 2025; and · 13 - 16 April 2025 ⁽¹⁾

Remarks:

(1) Due to adverse weather and safety concern, baseline noise monitoring at NM1, NM3 and NM5 were suspended since 11 April 2025 at 19:00; with the baseline noise monitoring at NM1, NM3 and NM5 resumed on 13 April 2025 at 19:00.

(2) Due to battery failure and restricted access on public holidays, baseline noise monitoring at NM2 was temporarily suspended since 4 April 2025 at 19:00 and resumed on 7 April 2025 at 19:00

(3) Due to adverse weather and safety concern, and restricted access on public holiday, baseline noise monitoring at NM2 was suspended since 11 April 2025 at 19:00 and resumed on 14 April 2025 at 19:00.

3.2 Monitoring Results and Analysis

3.2.1 Monitoring Results and Statistical Analysis of the Results

The baseline noise monitoring was carried out at the five monitoring locations (NM1, NM2, NM3, NM4 and NM5) between 31 March 2025 and 20 April 2025 (for NM1, NM2, NM3 and NM5) and between 26 May 2025 and 9 June 2025 (for NM4).

During the baseline noise monitoring period, the major noise sources identified were:

· NM1: traffic noise along North Lantau Highway

· NM2: traffic noise along North Lantau Highway

· NM3: traffic noise along Tat Tung Road, North Lantau Highway

· NM4: traffic noise along Tat Tung Road, North Lantau Highway

· NM5: traffic noise along North Lantau Highway, pedestrian noise

The weather condition during the baseline monitoring period typically varied between cloudy and sunny conditions. Local shower increased with thunderstorm was observed on 12 April 2025 during the baseline monitoring period. Peak noise levels were observed at NM5 monitoring station with a high deviation of noise level within a short period of time during the consecutive monitoring sessions. Such peak noise levels are excluded from calculation to ensure the robustness of the background noise conditions after reviewing the observed noise levels during the same monitoring session, and the potential noise source might be contributed by the nearby pedestrian activities at the cycle track and footpath which is located in close proximity to the monitoring location.

To conclude, the overall baseline noise monitoring period has captured at least 14 sets of background noise for both daytime, evening time and night time periods at the noise monitoring stations, therefore, the measured noise data at the five measured monitoring locations is considered representative of the baseline conditions for the ATCL Project.

The baseline noise monitoring results are summarised in Table 3.4, Table 3.5 and Table 3.6. Detailed monitoring results and graphical presentations are shown in Appendix B4.

Table 3.4: Summary of Baseline Noise Monitoring Results - Normal Weekday Daytime (0700-1900 hrs)

Time Period and Monitoring Station	L_eq_(30min), dB(A)
Normal Weekday Daytime (0700-1900 hrs)	Average	Range
NM1	65.3	62.8 - 66.8
NM2	65.0	63.0 - 67.6
NM3	66.1	64.0 - 69.4
NM4	64.6	63.3 - 69.5
NM5 ⁽¹⁾	63.8 ⁽²⁾	62.2 - 68.1 ⁽²⁾

Remarks:

(1) Peak noise level was observed during daytime at NM5: L_eq_(5min)of 90.0 dB(A) was observed on 15 April 2025; and the peak noise levels L_eq_(30min) of 82.3 dB(A) were excluded from the calculation for NM5.

(2) +3dB(A) correction for free-field measurement

Table 3.5: Summary of Baseline Noise Monitoring Results - Evening on Normal Weekday (1900-2300) and Sunday/Public Holiday (0700-2300 hrs)

Time Period and Monitoring Station	L_eq_(5min), dB(A)
Evening on Normal Weekday (1900-2300 hrs) and Sunday/Public Holiday (0700-2300 hrs)	Average	Range
NM1	64.5	61.7 - 67.7
NM2	64.3	61.2 - 67.8
NM3	65.6	62.6 - 72.3
NM4	63.4	60.9 - 66.9
NM5 ⁽¹⁾	63.1 ⁽²⁾	60.2 - 68.5 ⁽²⁾

Remarks:

(1) Peak noise levels were observed during evening time at NM5: L_eq_(5min)of 97.6 dB(A) was observed on 4 April 2025; L_eq_(5min)of 81.0 dB(A) was observed on 5 April 2025; L_eq_(5min)of 71.8 dB(A) and 90.5 dB(A) were observed on 13 April 2025; and these peak noise levels of L_eq_(5min) were excluded from the calculation for NM5.

(2) +3dB(A) correction for free-field measurement

Table 3.6: Summary of Baseline Noise Monitoring Results - Night-time (2300-0700 hrs)

Time Period and Monitoring Station	L_eq_(5min), dB(A)
Night-time (2300-0700 hrs)	Average	Range
NM1	62.1	54.6 - 66.3
NM2	62.5	55.0 - 67.3
NM3	62.2	55.1 - 69.1
NM4	60.3	51.8 - 65.4
NM5	60.1 ⁽¹⁾	51.9 - 68.0 ⁽¹⁾

Remark:

(1) +3dB(A) correction for free-field measurement

3.2.2 Action and Limit Levels

The Action and Limit Levels for construction noise impact monitoring have been defined in accordance with the ATCL Project EM&A Manual and are tabulated in Table 3.7.

Table 3.7: Action and Limit Levels for Construction Noise

Monitoring Station	Time Period	Action Level	Limit Level L_eq_(30min),dB(A)
NM1	0700-1900 hrs on normal weekdays	When one documented complaint is received	75
NM2			70 dB(A) and 65 dB(A) during examination period
NM3			75
NM4			75
NM5			75

3.2.3 Event and Action Plan

Should non-compliance of the noise criteria occur, actions in accordance with the Event and Action Plan in Table 3.8 shall be carried out.

Table 3.8: Event and Action Plan for Construction Noise

Event	Action
Event	ET	IEC	AAHK/PM	Contractor
Action Level	· Notify IEC, AAHK/PM and Contractor. · Identify source and carry out investigation. · Report the results of investigation to the IEC and Contractor. · Discuss jointly with the AAHK/PM and Contractor and formulate remedial measures. · Increase the monitoring frequency to check the effectiveness of mitigation measures.	· Review the analysed results submitted by ET. · Review the construction methods and proposed remedial measures by the Contractor, and advise the ET and AAHK/PM accordingly.	· Confirm receipt of the notification of failure in writing. · Notify Contractor. · Require Contractor to propose remedial measures for the analysed noise problem. · Ensure remedial measures are properly implemented.	· Identify source, and carry out investigation and report the investigation to ET, IEC and AAHK/PM. · Submit noise mitigation proposals to ET, IEC and AAHK/PM. · Implement noise mitigation proposals.
Limit Level	· Notify IEC, AAHK/PM, Contractor and EPD. · Identify sources and carry out investigation. · Repeat measurements to confirm findings. · Increase the monitoring frequency. · Carry out analysis of the Contractor’s working procedures to determine possible mitigations to be implemented. · Record and inform IEC, AAHK/PM and EPD the causes and action taken for the exceedances. · Assess the effectiveness of the Contractor’s remedial action and keep the IEC, AAHK/PM and EPD informed of the results. · If exceedance stops, cease additional monitoring.	· Check monitoring results and discuss amongst the AAHK/PM, ET and Contractor on the potential remedial actions. · Ensure remedial measures implemented properly. · Review Contractor remedial actions whenever necessary to assure their effectiveness and advise the AAHK/PM accordingly.	· Confirm receipt of notification of exceedance in writing. · Notify Contractor. · Require Contractor to propose remedial measures for the analysed noise problems. · Ensure remedial measures are properly implemented. · If exceedance continues, consider what portion of work is responsible and instruct the Contractor to stop that portion of works until the exceedance is abated.	· Identify source, and carry out investigation and report the investigation to ET, IEC and AAHK/PM. · Take immediate action to avoid further exceedance. · Submit proposals for remedial actions to ET, IEC and AAHK/PM within 3 working days of notification. · Implement the agreed proposals. · Resubmit proposals if problems still not under control. · Stop the relevant portion of works as determined by the AAHK/PM until the exceedance is abated.

Note: ET - Environmental Team; PM - Project Manager; IEC - Independent Environmental Checker; AAHK - Airport Authority Hong Kong

4 Water Quality

4.1 Monitoring Requirement

In accordance with Section 5.7.2 of the ATCL Project EM&A Manual and the agreed Water Quality Baseline Monitoring Proposal by EPD on 20 February 2025, the baseline water quality monitoring was conducted to establish ambient conditions prior to the commencement of the marine construction works and to demonstrate the suitability of the proposed impact and control monitoring stations. The baseline monitoring results for water quality were used to derive the Action and Limit levels.

4.1.1 Monitoring Parameters

Monitoring for Dissolved Oxygen (DO), Dissolved Oxygen Saturation (DO%), temperature, pH, turbidity, salinity, suspended solid (SS) and water depth should be undertaken at all designated monitoring locations. All parameters should be measured in-situ whereas SS should be determined by an accredited laboratory. Two (2) replicate in-situ measurements and samples collected from each independent sampling event should be collected to ensure a robust statistically interpretable database.

Other relevant data were also recorded, including monitoring location, time, tidal stages, weather conditions and any special phenomena or work during the monitoring.

4.1.2 Monitoring Locations

The marine facilities in the waters between Airport Island and HKP Island are included in the approved ATCL Project EIAR and the ATCL project EP, however, the construction of marine facilities is not included in the current stage of ATCL construction. Therefore, water quality monitoring will only be undertaken for the marine water quality monitoring stations for the marine viaduct (namely IM2, IM3, SR3, C3 and C4).

Baseline water quality monitoring was conducted for a total of 5 marine water quality monitoring locations (namely IM2, IM3, SR3, C3 and C4). The coordinates are listed in Table 4.1 and locations are shown in Figure 4.1.

Table 4.1: Marine Water Quality Monitoring Stations for the Marine Viaduct for Baseline Monitoring

Stations	Descriptions	Easting	Northing
IM2	Impact Station	812258	817871
IM3	Impact Station	810725	816626
SR3	Seawater Intake at Tung Chung	811780	817172
C3	Control Station	812785	818754
C4	Control Station	809533	817234

4.1.3 Monitoring Equipment and Methodology

Measurement should be taken at 3 water depths, namely, 1m below water surface, mid-depth and 1m above sea bed, except where the water depth less that 6m, the mid-depth station may be omitted. Should the water depth be less than 3m, only the mid-depth station will be monitored.

Duplicate in-situ measurements and water samples collected from each independent monitoring event are required for all parameters to ensure a robust statistically interpretable dataset. At each measurement depth, two consecutive measurements would be taken. The probes would be retrieved out of the water after the first measurement and then redeployed for the second measurement. When the difference in value between the first and second measurement of on-site parameters is more than 25% of the value of the first reading, the reading shall be discarded and further readings shall be taken.

In addition, no sampling should be carried out when typhoon signal No. 3 or above or black rainstorm signal is hoisted.

Monitoring Equipment

In-situ measurements at monitoring locations including dissolved oxygen (DO), dissolved oxygen saturation (DO%), pH, temperature, turbidity, salinity and water depth were collected using the equipment listed in Table 4.2.

Table 4.2: Baseline Marine Water Quality Monitoring Equipment

Equipment	Brand and Model
Water Sampler	Van Dorn Water sampler
Monitoring Position Equipment (measurement of DGPS)	XINUO XF-1069B
Water Depth Detector (measurement of water depth)	LUCKY^TM FF718Li Fish Finder
Multifunctional Meter (measurement of DO, DO% temperature, turbidity, salinity and pH)	YSI ProDSS (Multiparameter Sampling Instrument)

On the other hand, Marine Global Navigation Satellite System (GNSS) Chart Plotter (Model: XINUO XF-1069B), which is a Digital Global Positioning System (DGPS), was used during water quality monitoring to ensure the monitoring vessel is at the correct location before taking measurements. The DGPS was checked beforehand at an appropriate checkpoint before taking measurement and water samples.

Calibration of in-situ instruments

In-situ monitoring instruments for water quality parameters were checked, calibrated and certified by a laboratory accredited under HOKLAS before use. Responses of sensors and electrodes were checked with certified standard solutions before each use.

Wet bulb calibration for DO measurement was carried out before commencement of monitoring and after completion of all measurements each day. The turbidity meter was calibrated in order to establish the relationship between Nephelometric Turbidity Unit (NTU) and the levels of suspended solids. A zero check in distilled water was performed with the turbidity probe at least once per monitoring day. The probe was then calibrated with a solution of known NTU. Standard buffer solutions of at least pH 7 and pH 10 was used for calibration of the pH instrument before and after use on each monitoring day.

Calibration certificates of the monitoring equipment used in the baseline monitoring for water quality parameters (i.e. multifunctional meters) are provided in Appendix C1 with their serial number summarised in Table 4.3.

Table 4.3: Multifunctional Meters Used during the Baseline Water Quality Monitoring

Equipment	Serial No.
Multifunctional Meter (YSI ProDSS)	16H104233 (dry season, wet season)
	17H105557 (dry season, wet season)
	21G105356 (dry season, wet season)
	21K101468 (dry season)
	21K101469 (dry season)
	24A102447 (wet season)

Sample Containers and Storage

Water samples for SS determination were stored in high density polythene containers with no preservative added, packed in ice (cooled to 4^oC without being frozen) and delivered to the testing laboratory within 24 hours of collection and analysed as soon as possible after collection.

4.1.4 Laboratory Measurement / Analysis

At least 2 replicate samples from each independent sampling event were collected for the SS measurement. Analysis of SS was carried out in a HOKLAS accredited laboratory, ALS Technichem (HK) Pty Ltd (Reg. No. HOKLAS 066). Sufficient water samples were collected at each of the monitoring stations for carrying out the laboratory SS determination.

The SS determination works started within 24 hours after collection of the water samples. The analysis followed the APHA 2540D analytical method with a detection limit of 1 mg/L. The quality assurance and quality control results are presented in Appendix C2.

4.1.5 Monitoring Frequency and Duration

The baseline water quality monitoring was conducted three days per week for four weeks from 26 February to 24 March 2025 (dry season) and four weeks from 2 June to 2 July 2025 (wet season) respectively in order to capture seasonal variability, at mid-flood and mid-ebb tides, at 5 water quality monitoring stations. The interval between 2 sets of monitoring should not be less than 36 hours.

The baseline water quality monitoring schedule is presented in Appendix C3 and the monitoring period is summarised in Table 4.4.

Table 4.4: Baseline Water Quality Monitoring Frequency and Period

Season	Monitoring Frequency	Monitoring Period
Dry Season	3 days per week, at mid-flood and mid-ebb tides, for at least 4 weeks	26 February - 24 March 2025
Wet Season		2 June - 2 July 2025 ⁽¹⁾

Remark:

(1) The monitoring events on 11 & 13 June 2025 were cancelled due to adverse weather, make-up monitoring events were thus conducted on 30 June and 2 July 2025.

4.2 Baseline Monitoring Results and Analysis

4.2.1 Baseline Monitoring Results

The baseline water quality monitoring was conducted at the five monitoring stations (IM2, IM3, SR3, C3 and C4). The baseline water quality monitoring results and graphical presentations at each monitoring station are shown in Appendix C4. During the baseline monitoring period, no construction works were observed in the vicinity of all monitoring stations. The weather typically varied between cloudy and sunny conditions. The baseline monitoring results are thus considered representative of the ambient water quality of the Project area. A summary of the monitoring parameters is shown at Table 4.5.

Table 4.5: Summary of Baseline Water Quality Monitoring Result

Parameters	Stations	Average	Range ⁽³⁾
DO in mg/L (Surface and Middle)	IM2	6.9	5.4 - 11.8
	IM3	7.0	5.0 - 12.4
	SR3	6.9	5.1 - 12.3
	C3	6.9	4.8 - 13.0
	C4	6.6	4.4 - 10.3
DO in mg/L (Bottom)	IM2	N/A ⁽¹⁾	N/A ⁽¹⁾
	IM3	6.2	3.3 - 8.1
	SR3	6.2	3.4 - 8.1
	C3	7.4 ⁽²⁾	7.4 ⁽²⁾
	C4	6.0	3.2 - 8.0
SS in mg/L	IM2	4.4	1.0 - 16.1
	IM3	4.6	1.1 - 13.5
	SR3	4.6	1.1 - 11.3
	C3	4.3	1.1 - 12.0
	C4	4.4	1.2 - 14.9
Turbidity in NTU	IM2	3.3	0.3 - 10.6
	IM3	3.8	0.5 - 9.4
	SR3	3.5	0.6 - 7.4
	C3	2.8	0.4 - 11.9
	C4	3.6	0.5 - 8.7

Remarks:

(1) During the baseline water quality monitoring period, the water depth measured at IM2 was less than 3m, only middle-level water sampling was conducted at IM2 station.

(2) During the baseline water quality monitoring period, most of the water depth measured at C3 was less than 3m, only middle-level sampling was conducted at C3, except for one set of monitoring that was measured at the surface and bottom levels on 26 February 2025.

(3) The range value was calculated using the averaged values of each parameter.

4.2.2 Statistical Analysis of the Baseline Data

During baseline monitoring, DO, DO%, pH, temperature, turbidity, salinity and SS were monitored at the control and impact stations. However, for impact stations, only turbidity and SS are linked to the control station results during impact monitoring with respect to Action and Limit levels. As such, the statistical analysis to analyse for any significant differences was conducted for turbidity and SS between control stations and impact stations. Statistical analysis of the collected data using one-way analysis of variance (ANOVA) was conducted. Results of control stations were compared against impact stations. The results of the ANOVA test are presented in Table 4.6.

Table 4.6: ANOVA Test Results for Turbidity and SS

ANOVA Test Groups	p-value (alpha = 0.05)
Control Stations (C3, C4) Against Impact Stations (IM2, IM3, SR3)	Turbidity	SS
	0.29	0.60

As shown in Table 4.6, no significant difference was observed between the control stations and the impact stations for Turbidity and SS, suggesting that the control stations and impact stations are under the same water body, demonstrating the suitability of the control stations and impact stations.

4.2.3 Determination of Action and Limit Levels for Marine Water Quality

The baseline water quality monitoring data were used to determine the Action and Limit levels, using the derivation criteria specified in Section 5.7.16 of the ATCL Project EM&A Manual (shown in Table 4.7).

Table 4.7: Determination Criteria for Action and Limit Levels for Marine Water Quality

Parameters	Action Level	Limit Level
DO in mg/L	Surface and Middle 5 percentile of baseline data Bottom 5 percentile of baseline data	Surface and Middle 4 mg/L or 1 percentile of baseline data Bottom 2 mg/L or 1 percentile of baseline data
SS in mg/L	Depth Average 95 percentile of baseline data and 120% of upstream control station at the same tide of the same day	Depth Average 99 percentile of baseline data and 130% of upstream control station at the same tide of the same day
Turbidity in NTU	Depth Average 95 percentile of baseline data and 120% of upstream control station at the same tide of the same day	Depth Average 99 percentile of baseline data and 130% of upstream control station at the same tide of the same day

Notes:

1. ‘Depth Average’ is calculated by taking the arithmetic means of reading of all sampling depths.

2. For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.

3. For turbidity and SS, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.

4. All the figures given in the table are used for reference only and the EPD may amend the figures whenever it is considered as necessary.

As learnt from the dominant flow direction, control station C4 will be at the upstream during ebb tide while control station C3 will be at the upstream during flood tide. As such, control station C4 will act as the control station during the ebb tide while control station C3 will act as the control station during the flood tide. The arrangement during the impact monitoring is detailed in Table 4.8.

Table 4.8: Corresponding Control and Impact Monitoring Stations during Impact Monitoring

Tidal Direction	Control Station	Impact Stations
Ebb Tide	C4	IM2, IM3, SR3
Flood Tide	C3	IM2, IM3, SR3

Based on the derivation criteria for Action and Limit levels and the baseline water quality monitoring data obtained, the derived Action and Limit levels for marine water quality is presented in Table 4.9.

Table 4.9: Derived Action and Limit Levels for IM2, IM3, and SR3

Parameters	Action Level	Limit Level
DO in mg/L	Surface and Middle 5.1 Bottom 3.5	Surface and Middle 4.0 Bottom 2.0
SS in mg/L	Depth Average 10.8 and 120% of upstream control station at the same tide of the same day	Depth Average 13.4 and 130% of upstream control station at the same tide of the same day
Turbidity in NTU	Depth Average 7.9 and 120% of upstream control station at the same tide of the same day	Depth Average 9.9 and 130% of upstream control station at the same tide of the same day

Notes:

1. ‘Depth Average’ is calculated by taking the arithmetic means of reading of all sampling depths.

2. For DO, non-compliance of the water quality limits occurs when monitoring result is lower than the limits.

3. For turbidity and SS, non-compliance of the water quality limits occurs when monitoring result is higher than the limits.

4. All the figures given in the table are used for reference only and the EPD may amend the figures whenever it is considered as necessary.

4.2.4 Event and Action Plan

Should non-compliance of the water quality criteria occur, actions in accordance with the Event and Action Plan in Table 4.10 shall be carried out.

Table 4.10: Event and Action Plan for Marine Water Quality

Event	Action
Action level exceedance for one sample	· Inform IEC, Contractor and AAHK/PM. · Check monitoring data, all plant, equipment and Contractor’s working methods. · Discuss mitigation measures with IEC, Contractor and AAHK/PM.	· Discuss with ET, Contractor and AAHK/PM on the mitigation measures. · Review proposals on mitigation measures submitted by Contractor and advise AAHK/PM accordingly. · Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.	· Discuss with IEC, ET and Contractor on the implemented mitigation measures. · Make agreement on the mitigation measures to be implemented. · Supervise the implementation of agreed remedial measures.	· Identify source(s) of impact. · Inform AAHK/PM and confirm notification of the non-compliance in writing. · Rectify unacceptable practice; · Check all plant and equipment; · Consider changes of working methods. · Discuss with ET, IEC and AAHK/PM and propose mitigation measures to IEC and AAHK/PM. · Implement the agreed mitigation measures.
Action level being exceeded by two or more consecutive sampling days	· Repeat in-situ measurement on next day of exceedance to confirm findings. · Inform IEC, Contractor and AAHK/PM. · Check monitoring data, all plant, equipment and Contractor's working methods. · Discuss mitigation measures with IEC, Contractor and AAHK/PM. · Ensure mitigation measures are implemented.	· Discuss with ET, Contractor and AAHK/PM on the mitigation measures. · Review the proposed mitigation measures submitted by Contractor and advise the AAHK/PM accordingly. · Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.	· Discuss with ET, IEC and Contractor on the proposed mitigation measures. · Make agreement on the mitigation measures to be implemented. · Discuss with ET, IEC and Contractor on the effectiveness of the implemented mitigation measures.	· Identify source(s) of impact. · Inform AAHK/PM and confirm notification of the non-compliance in writing. · Rectify unacceptable practice. · Check all plant and equipment. · Consider changes of working methods. · Discuss with ET, IEC and AAHK/PM and submit proposal of mitigation measures to IEC and AAHK/PM within 3 working days of notification. · Implement the agreed mitigation measures.
Limit level exceedance for one sample	· Repeat measurement on next day of exceedance to confirm findings. · Inform IEC, Contractor and AAHK/PM. · Rectify unacceptable practice. · Check monitoring data, all plant, equipment and Contractor's working methods. · Discuss mitigation measures with IEC, AAHK/PM and Contractor. · Ensure the agreed mitigation measures are implemented.	· Discuss with ET, Contractor and AAHK/PM on the implemented mitigation measures. · Review the proposed mitigation measures submitted by Contractor and advise the AAHK/PM accordingly. · Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.	· Discuss with IEC, ET and Contractor on the implemented mitigation measures. · Request Contractor to critically review the working methods. · Make agreement on the mitigation measures to be implemented. · Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.	· Identify source(s) of impact. · Inform AAHK/PM and confirm notification of the non-compliance in writing. · Rectify unacceptable practice. · Check all plant and equipment. · Consider changes of working methods. · Discuss with ET, IEC and AAHK/PM and submit proposal of additional mitigation measures to IEC and AAHK/PM within 3 working days of notification. · Implement the agreed mitigation measures.
Limit level exceedance for two or more consecutive samples	· Inform IEC, Contractor, AAHK / PM; · Identify reasons for non-compliance and source(s) of impact; · Check monitoring data, all plant, equipment and Contractor's working methods; · Discuss mitigation measures with IEC, AAHK / PM and Contractor; · Ensure mitigation measures are implemented; · Increase the monitoring frequency to daily until no exceedance of Limit level for two consecutive days.	· Discuss with ET, Contractor and AAHK/PM on the implemented mitigation measures. · Review the proposed mitigation measures submitted by Contractor and advise AAHK/PM accordingly. · Review and advise ET and AAHK/PM on the effectiveness of implemented mitigation measures.	· Discuss with IEC, ET and Contractor on the implemented mitigation measures. · Request Contractor to critically review the working methods. · Make agreement on the mitigation measures to be implemented. · Discuss with ET and IEC on the effectiveness of the implemented mitigation measures. · Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the construction activities until no exceedance of Limit level.	· Identify source(s) of impact. · Inform AAHK/PM and confirm notification of non- compliance in writing. · Rectify unacceptable practices. · Check all plant and equipment. · Consider changes of working method. · Discuss with ET, IEC and AAHK/PM and submit proposal of additional mitigation measures to IEC and AAHK/PM within 3 working days of notification · Implement the agreed mitigation measures; · As directed by the AAHK/PM, to slow down or to stop all or part of the construction activities.

Event

Action

IEC

AAHK/PM

Contractor

Action level exceedance for one sample

· Inform IEC, Contractor and AAHK/PM.

· Check monitoring data, all plant, equipment and Contractor’s working methods.

· Discuss mitigation measures with IEC, Contractor and AAHK/PM.

· Discuss with ET, Contractor and AAHK/PM on the mitigation measures.

· Review proposals on mitigation measures submitted by Contractor and advise AAHK/PM accordingly.

· Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.

· Discuss with IEC, ET and Contractor on the implemented mitigation measures.

· Make agreement on the mitigation measures to be implemented.

· Supervise the implementation of agreed remedial measures.

· Identify source(s) of impact.

· Inform AAHK/PM and confirm notification of the non-compliance in writing.

· Rectify unacceptable practice;

· Check all plant and equipment;

· Consider changes of working methods.

· Discuss with ET, IEC and AAHK/PM and propose mitigation measures to IEC and AAHK/PM.

· Implement the agreed mitigation measures.

Action level being exceeded by two or more consecutive sampling days

· Repeat in-situ measurement on next day of exceedance to confirm findings.

· Inform IEC, Contractor and AAHK/PM.

· Check monitoring data, all plant, equipment and Contractor's working methods.

· Discuss mitigation measures with IEC, Contractor and AAHK/PM.

· Ensure mitigation measures are implemented.

· Discuss with ET, Contractor and AAHK/PM on the mitigation measures.

· Review the proposed mitigation measures submitted by Contractor and advise the AAHK/PM accordingly.

· Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.

· Discuss with ET, IEC and Contractor on the proposed mitigation measures.

· Make agreement on the mitigation measures to be implemented.

· Discuss with ET, IEC and Contractor on the effectiveness of the implemented mitigation measures.

· Identify source(s) of impact.

· Inform AAHK/PM and confirm notification of the non-compliance in writing.

· Rectify unacceptable practice.

· Check all plant and equipment.

· Consider changes of working methods.

· Discuss with ET, IEC and AAHK/PM and submit proposal of mitigation measures to IEC and AAHK/PM within 3 working days of notification.

· Implement the agreed mitigation measures.

Limit level exceedance for one sample

· Repeat measurement on next day of exceedance to confirm findings.

· Inform IEC, Contractor and AAHK/PM.

· Rectify unacceptable practice.

· Check monitoring data, all plant, equipment and Contractor's working methods.

· Discuss mitigation measures with IEC, AAHK/PM and Contractor.

· Ensure the agreed mitigation measures are implemented.

· Discuss with ET, Contractor and AAHK/PM on the implemented mitigation measures.

· Review the proposed mitigation measures submitted by Contractor and advise the AAHK/PM accordingly.

· Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.

· Discuss with IEC, ET and Contractor on the implemented mitigation measures.

· Request Contractor to critically review the working methods.

· Make agreement on the mitigation measures to be implemented.

· Review and advise ET and AAHK/PM on the effectiveness of the implemented mitigation measures.

· Identify source(s) of impact.

· Inform AAHK/PM and confirm notification of the non-compliance in writing.

· Rectify unacceptable practice.

· Check all plant and equipment.

· Consider changes of working methods.

· Discuss with ET, IEC and AAHK/PM and submit proposal of additional mitigation measures to IEC and AAHK/PM within 3 working days of notification.

· Implement the agreed mitigation measures.

Limit level exceedance for two or more consecutive samples

· Inform IEC, Contractor, AAHK / PM;

· Identify reasons for non-compliance and source(s) of impact;

· Check monitoring data, all plant, equipment and Contractor's working methods;

· Discuss mitigation measures with IEC, AAHK / PM and Contractor;

· Ensure mitigation measures are implemented;

· Increase the monitoring frequency to daily until no exceedance of Limit level for two consecutive days.

· Discuss with ET, Contractor and AAHK/PM on the implemented mitigation measures.

· Review the proposed mitigation measures submitted by Contractor and advise AAHK/PM accordingly.

· Review and advise ET and AAHK/PM on the effectiveness of implemented mitigation measures.

· Discuss with IEC, ET and Contractor on the implemented mitigation measures.

· Request Contractor to critically review the working methods.

· Make agreement on the mitigation measures to be implemented.

· Discuss with ET and IEC on the effectiveness of the implemented mitigation measures.

· Consider and instruct, if necessary, the Contractor to slow down or to stop all or part of the construction activities until no exceedance of Limit level.

· Identify source(s) of impact.

· Inform AAHK/PM and confirm notification of non- compliance in writing.

· Rectify unacceptable practices.

· Check all plant and equipment.

· Consider changes of working method.

· Discuss with ET, IEC and AAHK/PM and submit proposal of additional mitigation measures to IEC and AAHK/PM within 3 working days of notification

· Implement the agreed mitigation measures;

· As directed by the AAHK/PM, to slow down or to stop all or part of the construction activities.

Note: ET - Environmental Team; PM - Project Manager; IEC - Independent Environmental Checker; AAHK - Airport Authority Hong Kong

5 Conclusion

This Baseline Monitoring Report is prepared in accordance with Condition 3.3 of the ATCL Project EP and Section 12.2 of the ATCL Project EM&A Manual, to present the baseline monitoring results of air quality, noise and water quality prior to the commencement of construction works of the ATCL Project.

5.1 Revisions for Inclusion in the EM&A Manual

The following revision for inclusion in the ATCL Project EM&A Manual would be recommended:

Air Quality

· An alternative monitoring location AM1a is proposed to replace the original station AM1. As advised by the Leisure and Cultural Services Department, Tung Chung Community Garden (original monitoring station ID: AM1; ASR ID: A20) as stipulated in Table 3.1 of the ATCL Project EM&A Manual has been decommissioned and hence not accessible. Therefore, Tat Tung Road Garden which located next to the Tung Chung Community Garden is proposed to be the alternative air quality monitoring station. The proposed alternative location was agreed by the IEC and AAHK on 3 April 2025 and approved by EPD on 2 June 2025.

5.2 Baseline Air Quality Monitoring

Overall, the baseline air quality results are considered representative to the ambient air quality of the ATCL Project and were used to establish the Action and Limit Levels for air quality.

5.3 Baseline Noise Monitoring

Baseline noise monitoring was carried out at the five designated monitoring locations (namely NM1, NM2, NM3, NM4 and NM5). Summary of noise monitoring period as shown below:

· NM1: from 31 March 2025 to 11 April 2025; and from 13 to 16 April 2025.

· NM2: from 31 March 2025 to 4 April 2025; from 7 to 11 April 2025; and from 14 to 20 April 2025.

· NM3: from 2 to 11 April to 2025; and from 13 to 18 April 2025.

· NM4: from 26 May 2025 to 9 June 2025.

· NM5: from 31 March 2025 to 11 April 2025; and from 13 to 16 April 2025

Due to battery failure and restricted access on public holidays, baseline noise monitoring at NM2 was temporarily suspended since 4 April 2025 at 19:00 and resumed on 7 April 2025 at 19:00.

Due to adverse weather and safety concern, baseline noise monitoring at NM1, NM2, NM3 and NM5 were suspended since 11 April 2025 at 19:00; with the baseline noise monitoring at NM1, NM3 and NM5 resumed on 13 April 2025 at 19:00; and NM2 resumed on 14 April 2025 at 19:00.

During the baseline noise monitoring period, the major noise sources identified were:

· NM1: traffic noise along North Lantau Highway

· NM2: traffic noise along North Lantau Highway

· NM3: traffic noise along Tat Tung Road, North Lantau Highway

· NM4: traffic noise along Tat Tung Road, North Lantau Highway

· NM5: traffic noise along North Lantau Highway, pedestrian noise

5.4 Baseline Water Quality Monitoring

The baseline water quality monitoring was conducted three days per week for four weeks from 26 February to 24 March 2025 (dry season), and from 2 June to 2 July 2025 (wet season), at mid-flood and mid-ebb tides, at 5 water quality monitoring stations. Monitoring of dissolved oxygen (DO), dissolved oxygen saturation (DO%), pH, temperature, turbidity, salinity and suspended solids (SS) were undertaken at all monitoring stations. As no pertinent activities were observed in the vicinity of the monitoring stations during the baseline monitoring that would affect the monitoring results, the water quality monitoring results obtained are considered to be appropriate for adoption as the baseline water quality dataset for the ATCL Project.

The Action and Limit levels for water quality impact monitoring at impact stations were derived based on the baseline water quality monitoring conducted in February, March, June and July 2025.