Air Quality

2. AIR QUALITY

2.1 Introduction

2.1.1 The EIA concluded dust impacts during the construction phase can be readily mitigated through implementation of standard mitigation measures and good housekeeping practices. However, if the proposed construction dust mitigation measures are not fully implemented, it is likely that some nearest air sensitive receivers would suffer unacceptable impact. It is therefore recommended that an EM&A programme in respect of dust issue be carried out at representative Air Sensitive Receivers (ASRs) to monitor the effectiveness and efficiency of the dust suppression measures.

2.1.2 This section describe the requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of air quality impacts during the construction phase of the Project.

2.1.3 No adverse air quality impact is expected during operation phase, hence air quality monitoring during operation phase is considered not necessary.

2.2 Air Quality Parameters

2.2.1 1-hour and 24-hour Total Suspended Particulates (TSP) levels shall be measured to indicate the impacts of construction dust on air quality. The 24-hour TSP levels shall be measured by following the standard high volume sampling method as set out in the Title 40 of the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B. Upon approval of the ER, 1-hour TSP levels, that indicate short event impacts, can be measured by direct reading methods which are capable of producing comparable results to that taken by the high volume sampling method.

2.2.2 All relevant data including temperature, pressure, weather conditions, elapsed-time meter reading for the start and stop of the sampler, identification and weight of the filter paper, and other special phenomena and work progress of the concerned site etc. shall be recorded in detail. A sample data sheet is shown in Appendix B.

2.3 Monitoring Equipment

2.3.1 High volume samplers (HVS) in compliance with the following specifications shall be used for carrying out the TSP monitoring:

(a) 0.6 – 1.7 m³/min (20-60 SCFM) adjustable flow range;

(b) equipped with a timing/control device with ± 5 minutes accuracy for 24 hours operation;

(d) capable of providing a minimum exposed area of 406 cm² (63 in²);

(e) flow control accuracy: ± 2.5% deviation over 24-hr sampling period;

(f) equipped with a shelter to protect the filter and sampler;

(g) incorporated with an electronic mass flow rate controller or other equivalent devices;

(h) equipped with a flow recorder for continuous monitoring;

(i) provided with a peaked roof inlet;

(j) incorporated with a manometer;

(k) able to hold and seal the filter paper to the sampler housing at horizontal position;

(l) easy to change the filter; and

(m) capable of operating continuously for 24-hr period.

2.3.2 The ET is responsible for provision of the monitoring equipment. They shall ensure that sufficient numbers of HVSs with an appropriate calibration kit are available for carrying out the baseline monitoring, regular impact monitoring and ad hoc monitoring. The HVSs shall be equipped with an electronic mass flow controller and be calibrated against a traceable standard at regular intervals. All the equipment, calibration kit, filter papers, etc. shall be clearly labelled.

2.3.3 Initial calibration of dust monitoring equipment shall be conducted upon installation and thereafter at bi-monthly intervals. The transfer standard shall be traceable to the internationally recognised primary standard and be calibrated annually. The calibration data shall be properly documented for future reference. All the data should be converted into standard temperature and pressure condition.

2.3.4 The flow-rate of the sampler before and after the sampling exercise with the filter in position shall be verified to be constant and be recorded down in a data sheet as shown in Appendix B.

2.3.5 If the ET Leader proposes to use a direct reading dust meter to measure 1-hour TSP levels, he shall submit sufficient information to the ER and IEC to prove that the instrument is capable of achieving a comparable result to the HVS. The instrument shall also be calibrated regularly, and the 1-hour sampling shall be determined periodically by HVS to check the validity and accuracy of the results measured by direct reading method.

2.4 Laboratory Measurement/Analysis

2.4.1 A clean laboratory with constant temperature and humidity control, and equipped with necessary measuring and conditioning instruments, to handle the dust samples collected, shall be available for sample analysis, and equipment calibration and maintenance. The laboratory should be HOKLAS accredited.

2.4.2 If a site laboratory is set up or a non-HOKLAS accredited laboratory is hired for carrying out the laboratory analysis, the laboratory equipment shall be approved by the ER and in consultation with the IEC. Measurement performed by the laboratory shall be demonstrated to the satisfaction of the ER and the IEC. The IEC shall conduct regular audit to the measurement performed by the laboratory to ensure the accuracy of measurement results. The ET Leader shall provide the ER with one copy of the Title 40 of the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B for his reference.

2.4.3 Filter paper of size 8"x10" shall be labelled before sampling. It shall be a clean filter paper with no pin holes, and shall be conditioned in a humidity controlled chamber for over 24-hr and be pre-weighed before use for the sampling.

2.4.4 After sampling, the filter paper loaded with dust shall be kept in a clean and tightly sealed plastic bag. The filter paper shall then be returned to the laboratory for reconditioning in the humidity controlled chamber followed by accurate weighing by an electronic balance with a readout down to 0.1 mg. The balance shall be regularly calibrated against a traceable standard.

2.4.5 All the collected samples shall be kept in a good condition for 6 months before disposal.

2.5 Monitoring Locations

2.5.1 The air quality monitoring locations are shown in Table 2.1 and Figure 2.1. The status and locations of air sensitive receivers may change after issuing this manual. If such cases exist, the ET Leader shall propose updated monitoring locations and seek approval from ER and agreement from the IEC.

Table 2.1

Air Quality Monitoring Stations

Air Quality Monitoring Station	ASR ID	Description
A1	ASR 1	Wing Jan Camp
A2	ASR 2	Village house at No.57 Hang Hau Tsuen

Notes:

All monitoring stations shall be proposed by the Environmental Team Leader and verified by the Independent Environmental Checker before submitting to EPD prior to commencement of any monitoring.

2.5.2 When alternative monitoring locations are proposed, the following criteria, as far as practicable, should be followed:

(a) at the site boundary or such locations close to the major dust emission source;

(b) close to the sensitive receptors; and

2.5.3 The ET Leader shall agree with the ER in consultation with the IEC on the position of the HVS for installation of the monitoring equipment. When positioning the samplers, the following points shall be noted:

(a) a horizontal platform with appropriate support to secure the samplers against gusty wind should be provided;

(b) no two samplers should be placed less than 2 metres apart;

(c) the distance between the sampler and an obstacle, such as buildings, must be at least twice the height that the obstacle protrudes above the sampler;

(d) a minimum of 2 metres separation from walls, parapets and penthouses is required for rooftop samplers;

(e) a minimum of 2 metres separation from any supporting structure, measured horizontally is required;

(f) no furnace or incinerator flue is nearby;

(g) airflow around the sampler is unrestricted;

(h) the sampler is more than 20 metres from the dripline;

(i) any wire fence and gate, to protect the sampler, should not cause any obstruction during monitoring;

(j) permission must be obtained to set up the samplers and to obtain access to the monitoring stations; and

(k) a secured supply of electricity is needed to operate the samplers.

2.6 Baseline Monitoring

2.6.1 Baseline monitoring shall be carried out at all of the designated monitoring locations (Table 2.1) for at least 14 consecutive days prior to the commissioning of the construction works to obtain daily 24-hour TSP samples. 1-hour sampling shall also be done at least 3 times per day while the highest dust impact is expected.

2.6.2 Before commencing the baseline monitoring, the ET Leader shall inform the IEC of the baseline monitoring programme such that the IEC can conduct an on-site audit to ensure accuracy of the baseline monitoring results. Table 2.2 summarises the parameters, frequency and duration for baseline monitoring.

Table 2.2

Air Quality Monitoring Locations, Parameters, Frequency and Duration for Baseline

Location	Parameters	Frequency	Duration
A1	24‑hour TSP	Daily	Two consecutive week (total 14 days)
A2	(All Locations)	Daily
	1-hour TSP	Three times daily during time of peak dust levels
	(All Locations)	Three times daily during time of peak dust levels

2.6.3 During the baseline monitoring, there should not be any construction or dust generation activities in the vicinity of the monitoring stations.

2.6.4 In case the baseline monitoring cannot be carried out at the designated monitoring locations during the baseline monitoring period, the ET Leader shall carry out the monitoring at alternative locations that can effectively represent the baseline conditions at the impact monitoring locations. The alternative baseline monitoring locations shall be approved by the ER and with the IEC.

2.6.5 In exceptional cases, when insufficient baseline monitoring data or questionable results are obtained, the ET shall liaise with the IEC and EPD to agree on an appropriate set of data to be used as a baseline reference and submit to ER for approval.

2.6.6 Ambient conditions may vary seasonally and shall be reviewed at three monthly intervals. When the ambient conditions have changed and a repeat of the baseline monitoring is required to be carried out for obtaining updated baseline levels, the monitoring should be conducted at times when the contractor's activities are not generating dust, at least in the proximity of the monitoring stations. Should a change in ambient conditions be determined, the baseline levels and, in turn, the air quality criteria, should be revised. The revised baseline levels and air quality criteria should be agreed with the IEC and EPD.

2.7 Impact Monitoring

2.7.1 The ET Leader shall carry out impact monitoring during the course of the works. For regular impact monitoring, the sampling frequency of once in every six-days shall be performed at all designated monitoring stations for 24-hour TSP monitoring. For 1-hour TSP monitoring, the sampling frequency of three times in every six-days should be undertaken when the highest dust impact occurs. Before commencing the impact monitoring, the ET Leader shall inform the IEC of the impact monitoring programme such that the IEC can conduct on-site audit to ensure accuracy of the impact monitoring results. All the locations listed in Table 2.1 shall be monitored.

2.7.2 The specific time to start and stop the 24-hour TSP monitoring shall be clearly defined for each location and be strictly followed by the operator.

2.7.3 In case of non-compliance with the air quality criteria, additional monitoring, as specified in the Action Plan in the following section, shall be conducted within 24 hours after the result is obtained. This additional monitoring shall be continued until the excessive dust emission or the deterioration in air quality is rectified.

2.8 Event and Action Plan for Air Quality

2.8.1 The baseline monitoring results form the basis for determining the air quality criteria for the impact monitoring. The ET shall compare the impact monitoring results with air quality criteria set up for 24-hour TSP and 1-hour TSP. Table 2.3 shows the air quality criteria and Action and Limit levels to be used. Should non-compliance of the air quality criteria occurs, the ET, the ER and the Contractor shall undertake the relevant action in accordance with the Action Plan in Table 2.4.

Table 2.3

Action and Limit Levels for Air Quality

Parameters	Action	Limit
24-Hour TSP Level in μg/m³	For baseline level ≤ 200 μg/m³, Acton level = (Baseline level * 1.3 + Limit level)/2; For baseline level > 200 μg/m³, Action level = Limit level	260
1-Hour TSP Level in μg/m³	For baseline level ≤ 384 μg/m³, Acton level = (Baseline level * 1.3 + Limit level)/2; For baseline level > 384 μg/m³, Action level = Limit level	500

Parameters

Action

Limit

24-Hour TSP Level in μg/m³

For baseline level ≤ 200 μg/m³, Acton level = (Baseline level * 1.3 + Limit level)/2;

For baseline level > 200 μg/m³, Action level = Limit level

260

1-Hour TSP Level in μg/m³

For baseline level ≤ 384 μg/m³, Acton level = (Baseline level * 1.3 + Limit level)/2;

For baseline level > 384 μg/m³, Action level = Limit level

500

Table 2.4

Event/Action Plan for Air Quality

EVENT	ACTION
EVENT	ET Leader	IEC	ER	Contractor
ACTION LEVEL
1. Exceedance for one sample	1. Identify source 2. Inform IEC, ER and Contractor 3. Repeat measurement to confirm findings 4. Increase monitoring frequency to daily	1. Check monitoring data submitted by ET Leader 2. Check Contractor’s working method	1. Notify Contractor	1. Rectify any unacceptable practice 2. Amend working methods if appropriate
2. Exceedance for two or more consecutive samples	1. Identify source 2. Inform IEC, ER and Contractor 3. Repeat measurement to confirm findings 4. Increase monitoring frequency to daily 5. Discuss with IEC, Contractor and ER on remedial actions required 6. If exceedance continue, arrange meeting with IEC, ER and Contractor 7. If exceedance stops, cease additional monitoring	1. Checking monitoring data submitted by ET Leader. 2. Check Contractor’s working method 3. Discuss with ET Leader and Contractor on possible remedial measures 4. Advise the ER on the effectiveness of the proposed remedial measures 5. Supervise implementation of remedial measures	1. Confirm receipt of notification of failure in writing 2. Notify Contractor 3. Ensure remedial measures properly implemented	1. Submit proposals for remedial actions to IEC and ER within 3 working days of notification 2. Implement the agreed proposals 3. Amend proposal if appropriate
LIMIT LEVEL
1. Exceedance for one sample	1. Identify source 2. Inform IEC, ER, EPD and Contractor 3. Repeat measurement to confirm findings 4. Increase monitoring frequency to daily 5. Assess effectiveness of Contractor’s remedial actions and kept IEC, EPD and ER informed of the results	1. Check monitoring data submitted by ET Leader 2. Check Contractor’s working method 3. Discuss with ET Leader and Contractor on possible remedial measures 4. Advise the ER on the effectiveness of the proposed remedial measures 5. Audit implementation of remedial measures	1. Confirm receipt of notification of failure in writing 2. Notify Contractor 3. Ensure remedial measures properly implemented	1. Take immediate action to avoid for the exceedance 2. Submit proposals for remedial actions to IEC and ER within 3 working days of notification 3. Implement the agreed proposals 4. Amend proposal if appropriate
2. Exceedance for two or more consecutive samples	1. Notify IEC, ER, Contractor and EPD 2. Identify source 3. Repeat measurement to confirm findings 4. Increase monitoring frequency to daily 5. Carry out analysis of Contractor’s working procedures to determine possible mitigation to be implemented 6. Arrange meeting with IEC, Contractor and ER to discuss the remedial actions to be taken 7. Assess effectiveness of Contractor’s remedial actions and keep IEC, EPD and ER informed of the results 8. If exceedance stops, cease additional monitoring	1. Discuss amongst ER, ET leader and Contractor on the potential remedial actions 2. Review Contractor’s remedial actions whenever necessary to assure their effectiveness and advise the ER accordingly 3. Audit the implementation of remedial measures	1. Confirm receipt of notification of failure in writing 2. Notify Contractor 3. In consultation with IEC, agree with the Contractor on the remedial measures to be implemented 4. Ensure remedial measures properly implemented 5. If exceedance continues, consider what portion of the work is responsible and instruct the Contractor to stop that portion of work until the exceedance is abated.	1. Take immediate action to avoid for the exceedance 2. Submit proposals for remedial actions to IEC and ER within 3 working days of notification 3. Implement the agreed proposals 4. Resubmit proposals if problem still not under control 5. Stop the relevant portion of works as determined by the ER until the exceedance is abate.

2.9 Mitigation Measures

Construction Phase

Construction Dust

2.9.1 In order to comply with Air Pollution Control Ordinance (APCO), the Contractor should undertake at all times measures to prevent dust nuisance as a results of his activities. The Contractors are required to follow all the requirements for dust control stipulated in the Air Pollution Control (Construction Dust) Regulation. Dust suppression measures should be installed as part of good construction practice, and they should be incorporated in the Contract Specification and implemented to minimize dust nuisance to within acceptable levels arising from the works. The followings are examples of the dust suppression measures.

(i) The area in which excavation takes place shall be sprayed with water immediately prior to, during and immediately after the excavation to minimise dust generation.

(ii) The Contractor shall frequently clean and water the site to minimize fugitive dust emissions.

(iii) Effective water sprays shall be used during the delivery and handling of aggregate, and other similar materials, when dust is likely to be created and to dampen all stored materials during dry and windy weather.

(iv) Watering of exposed surfaces shall be conducted at least 2 times per day especially during dry and windy weather.

(v) Areas within the site where there is a regular movement of vehicles must be regularly watered as often as necessary for effective suppression of dust or as often as directed by the Engineer.

(vi) Where dusty material are being discharged to vehicle from a conveying system at a fixed transfer point, a three-sided roofed enclosure with a flexible curtain across the entry shall be provided. Exhaust fans shall be provided for this enclosure and vented to a suitable fabric filter system.

(vii) The Contractor shall restrict all motorised vehicles within the site, excluding those on public roads, to a maximum speed of 15 km per hour and confine haulage and delivery vehicles to designated roadways inside the site.

(viii) Wheel washing facilities shall be installed and used by all vehicles leaving the site. No earth, mud, debris, dust and the like shall be deposited on public roads. Water in the wheel cleaning facility shall be changed at frequent intervals and sediments shall be removed regularly. The Contractor shall submit details of proposals for the wheel cleaning facility. Such wheel washing facilities shall be usable prior to any earthworks excavating activity on the site. The Contractor shall also provide a hard-surfaced road between any washing facility and the public road.

(ix) All vehicle exhausts shall be directly vertically upwards or directed away from the ground.

(x) Any materials dropped on paved roads shall be cleaned up immediately to prevent dust nuisance.

Odour

2.9.2 In the event that excavated materials are found to be odourous, the following measures should be implemented by the Contractor.

(i) Place odorous excavated material as far away (say, at least 20m) from air sensitive receivers as possible.

(ii) Temporary stockpiles of odorous excavated material should be properly covered with tarpaulin and should be removed off-site as soon as practically possible within 2 days to avoid any odour nuisance arising.

Operational Phase

2.9.3 No adverse air quality impact is identified during operational phase. In the event that sediment excavated during maintenance are found to be odourous, the following measures should be implemented by DSD (or DSD’s maintenance contractor).

(i) Place odorous excavated material as far away (say, at least 20m) from air sensitive receivers as possible.

(ii) Odorous excavated material should be properly covered with tarpaulin or packed in plastic bags or stored in enclosed skips and should be removed off-site as soon as practically possible within 2 days to avoid any odour nuisance arising.

2.9.4 If the above construction phase mitigation measures are not sufficient to restore the impacts to acceptable levels upon the advice of ET Leader, the Contractor shall liaise with the ET Leader on some other mitigation measures, endorsed by IEC and propose to ER for approval, and implement the mitigation measures.

2.9.5 The implementation schedule for the recommended mitigation measures is presented in Appendix A.