9.                   AIR QUALITY

 

Introduction

 

9.1               This section presents 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.

 

9.2               The objectives of the air quality monitoring shall be:

(i)      To identify the extent of construction dust impacts on sensitive receivers;

(ii)      To determine the effectiveness of mitigation measures to control fugitive dust emission from activities during construction phase;

(iii)     To audit the compliance of the Contractor with regard to dust control, contract conditions and the relevant dust impact criteria;

(iv)     To recommend further mitigation measures if found to be necessary; and

(v)      To comply with Action and Limit (A/L) Levels for air quality as defined in this Manual.

 

Air Quality Parameters

 

9.3               The criteria against which ambient air quality monitoring shall be assessed are:

(i)      The Hong Kong Air Quality Objectives (AQOs) for TSP, 24-hour TSP levels of 260 mg m-3; and

(ii)      The statutory 1-hour TSP limit of 500 mg m-3.

 

9.4               These levels are not to be exceeded at Air Sensitive Receivers (ASRs).

 

Monitoring Equipment

 

9.5               The TSP levels shall be measured by following the standard method as set out in High Volume Method for Total Suspended Particulates, Part 50 Chapter 1 Appendix B, Title 40 of the Code of Federal Regulations of the USEPA.

 

9.6               Dust laden with air shall be drawn through a high volume sampler (HVS) fitted with a conditioned, pre-weighed filter paper, at a controlled rate.  After sampling for 24-hours, the filter paper with retained particles is collected and returned to the laboratory for drying in a desiccator followed by accurate weighing.  24-hour average TSP levels are calculated from the ratio of the mass of particulates retained on the filter paper to the total volume of air sampled.

 

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

 

9.8               HVS in compliance with the following specifications shall be used for carrying out the 1-hour and 24-hour monitoring:

(i)             0.6 - 1.7 m3 per minute (20 - 60 standard cubic feet per minute) adjustable flow range;

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

(iii)          installed with elapsed-time meter with ± 2 minutes accuracy for 24 hours operation;

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

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

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

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

(viii)       provided with a peaked roof inlet;

(ix)         incorporated with a manometer;

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

(xi)         easy to change the filter;

(xii)        capable of operating continuously for 24-hour period.

 

9.9               The ET shall be responsible for the provision of the monitoring equipment. He shall ensure that sufficient number of HVSs with appropriate calibration kit is available for carrying out the baseline, regular impacts 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, in accordance with requirements stated in the manufacturers operating manual and as described below.  All the equipment, calibration kit, filter papers, etc, shall be clearly labelled.

 

9.10            The flow rate of each HVS with mass flow controller shall be calibrated using an orifice calibrator.  Calibration shall be carried out every six months.

 

9.11            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 on the data sheet as mentioned in Appendix C.

 

Air Quality Monitoring Station

 

9.12            The worst affected locations in the vicinity of construction sites have been identified for TSP dust monitoring as shown in Table 9.1 and illustrated in Figure 9.1 – 9.3. 

Table 9.1      Air Monitoring Stations during Construction Phase

Construction Work Site

Identification No.

Air Monitoring Location

Kennedy Town Station

AM1

ASR K5 - Pokfield Garden

AM2

ASR K15 - Victoria Public Mortuary

AM3

ASR K17 - Kennedy Town Police Quarters Block B

AM4

ASR K19 - School at Victoria Road

University Station

AM5

ASR U11- New Fortune House, Block A

AM6

ASR U3 - Yam Pak Building

AM7

ASR U5 - Jadeview Court

Sai Ying Pun Station

AM8

ASR S1 - Bon-Point

AM9

ASR S2 - No. 18-20 Eastern St

AM10

ASR S3 - Western Garden, Ivy Tower

 

9.13            When alternative monitoring locations are proposed, the monitoring locations shall be chosen based on the following criteria:

(i)             Monitoring at sensitive receivers close to the major site activities which are likely to have air quality impacts;

(ii)           Monitoring at the air sensitive receivers as defined in the Technical Memorandum;

(iii)          Assurance of minimal disturbance to the occupants during monitoring.

 

9.14            When positioning the HVSs, the following points shall be noted:

(i)             A horizontal platform with appropriate support to secure the samplers against gusty wind shall be provided;

(ii)           no two samplers shall be placed less than 2 m apart;

(iii)          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;

(iv)          a minimum of 2 m separation from walls, parapets and penthouses is required for rooftops samplers;

(v)            a minimum of 2 m separation from any supporting structure, measures horizontally is required;

(vi)          no furnace or incinerator flue is nearby;

(vii)         airflow around the sampler is unrestricted;

(viii)       the sampler is more than 20 m from the dripline;

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

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

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

 

Baseline Monitoring

 

9.15            Baseline monitoring shall be carried out to determine the ambient 1-hour and 24‑hour TSP levels at the monitoring locations prior to the commencement of the Project works.  During the baseline monitoring, there shall not be any construction or dust generating activities in the vicinity of the monitoring stations.

 

9.16            TSP baseline monitoring shall be carried out for a continuous period of at least two weeks under typical weather conditions with the 24-hour and three 1-hour ambient measurements taken daily at each monitoring location.  General meteorological conditions (wind speed, direction and precipitation) and notes regarding any significant adjacent dust producing sources shall also be recorded throughout the baseline monitoring period.

 

9.17            The baseline monitoring will provide data for the determination of the appropriate Action levels with the Limit levels set against statutory or otherwise agreed limits.

 

9.18            Baseline checking of ambient TSP levels shall be carried out every six months at each monitoring location, when no dusty works activities are in operation.  If the ET considers that significant changes in the ambient conditions have arisen, a repeat of the baseline monitoring may be carried out to update the baseline levels and air quality criteria, after consultation and agreement with the ER, the IEC and the EPD.

 

Impact Monitoring for Construction Air Quality Impact

 

9.19            The monthly schedule of the compliance and impact monitoring programme shall be drawn up by the ET one month prior to the commencement of the scheduled construction period.  For regular impact monitoring, a sampling frequency of at least once in every six days shall be strictly observed at all of the monitoring stations for 24-hour TSP monitoring.  In case of complaints, 1-hour TSP monitoring shall be conducted at least three times in every six days when the highest dust impacts are likely to occur.  The impact monitoring programme is summarised in Table 9.2.

Table 9.2      Dust Impact Monitoring Programme

Sampling duration

Frequency

1 hour

·       3 times every 6 days (as required in case of complaints)

24 hours

·       Once every 6 days

 

9.20            Before commencing the monitoring, the ET shall inform the IEC of the impact monitoring programme such that the IEC can conduct an on-site audit to ensure the accuracy of the impact monitoring results.

 

 

 

 

 

 

 

Compliance Assessment

 

9.21            Action and Limit levels that provide an appropriate framework for the interpretation of monitoring results have to be agreed between ET, IEC, EPD and the Engineer before commencement of the air monitoring.  The air quality monitoring data shall be checked against the agreed A/L levels.  Recommended A/L levels are listed in Table 9.3.

 

Table 9.3      Proposed Action and Limit Levels for Impact Monitoring

Parameter

Action Level (1)

Limit Level

TSP (24 hour average)

·         BL £ 200μg m-3, AL = (BL * 1.3 + LL)/2

·         BL > 200μg m-3, AL = LL

260 μg m-3

TSP (1 hour average)

·         BL £ 384μg m-3, AL = (BL * 1.3 + LL)/2

·        BL > 384μg m-3, AL = LL

500μg m-3

(1)        BL = Baseline level, AL = Action level, LL = Limit level.

 

Event and Action Plan (EAP)

 

9.22            The principle upon which the EAP is based on the prescription of procedures and actions associated with the measurement of certain defined levels of air pollution recorded by the environmental monitoring process and the agreed A/L levels.  In cases where exceedance of these A/L levels occurs, the ET, the IEC, the Engineer and the Contractor shall strictly observe the relevant actions of the respective EAP listed in Table 9.4.


Table 9.4      Event and Action Plan for Ambient Air Quality Monitoring (Construction)

EVENT

ACTION

ET

IEC

ER

CONTRACTOR

ACTION LEVEL

 

1.    Exceedance for one sample

 

1.      Identify source, investigate the causes of complaint and propose remedial measures;

2.      Inform IEC and ER;

3.      Repeat measurement to confirm finding;

4.      Increase monitoring frequency to daily.

 

1.        Check monitoring data submitted by ET;

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 and ER;

3.      Advise the ER on the effectiveness of the proposed remedial measures;

4.      Repeat measurements to confirm findings;

5.      Increase monitoring frequency to daily;

6.      Discuss with IEC and ER (together with the Contractor) on remedial actions required;

7.      If exceedance continues, arrange meeting with IEC and ER;

8.      If exceedance stops, cease additional monitoring.

 

1.      Check monitoring data submitted by ET;

2.      Check Contractor’s working method;

3.      Discuss with ET and ER (together with the Contractor) on possible remedial measures;

4.      Advise the ET/ER on the effectiveness of the proposed remedial measures;

5.      Supervise Implementation of remedial measures.

 

1.    Confirm receipt of notification of exceedance in writing;

2.       Notify Contractor;

3.       Ensure remedial measures properly implemented.

 

 

1.    Submit proposals for remedial to ER within three working days of notification;

2.    Implement the agreed proposals;

3.    Amend proposal if appropriate.

LIMIT LEVEL

 

1.    Exceedance for one sample

 

1.    Identify source, investigate the causes of exceedance and propose remedial measures;

2.    Inform IEC, ER, Contractor and EPD;

3.    Repeat measurement to confirm finding;

4.    Increase monitoring frequency to daily;

5.    Assess effectiveness of Contractor’s remedial actions and keep IEC, EPD and ER informed of the results.

 

1.      Check monitoring data submitted by ET;

2.      Check Contractor’s working method;

3.      Discuss with ET and ER (together with the 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 exceedance in writing;

2.      Notify Contractor;

3.      Ensure remedial measures properly implemented.

 

1.        Take immediate action to avoid further exceedance;

2.        Submit proposals for remedial actions to ER with a copy to IEC within three 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 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, 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.      Supervise the implementation of remedial measures.

 

1.       Confirm receipt of notification of exceedance in writing;

2.       Notify Contractor;

3.       In consultation with the 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 further exceedance;

2.    Submit proposals for remedial actions to ER with a copy to IEC within three working days of notification;

3.    Implement the agreed proposals;

4.    Revise and resubmit proposals if problem still not under control;

5.    Stop the relevant portion of works as determined by the ER until the exceedance is abated.

Mitigation Measures

 

9.23            The EIA Report recommended air quality control and mitigation measures during the construction phase of the Project.  The mitigation measures are summarised below.

 

9.24            Dust mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation should be incorporated to control dust emission from all construction work sites.  For the proposed two rock crushing plants at Kennedy Town Abattoir Site and Western PCWA, the requirements and mitigation measures stipulated in the Guidance Note on the Best Practicable Means for Mineral Works (Stone Crushing Plants) BPM 11/1 should be followed and implemented.  

 

9.25            According to the preliminary engineering information, the following design control measures have been incorporated into the design of the crushing plants, barging facilities and stockpile areas, as presented in Table 9.5, 9.6 and 9.7.

 

Table 9.5      Rock Crushing Plants – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Unloading of raw materials

Unloading of stone/rock at the receiving hopper

The unloading process would be undertaken within enclosed rock crushing facility.   Water spraying would be provided at the unloading point.

 

Crushing of raw materials

Crushing the stone/rock with rock crusher.

The crushing process is the secondary crushing.  The rock crushing plant is enclosed and water spraying system would be installed.  Dust extraction and collection system (80% dust removal efficiency) would be provided.

 

Screening process

Screening the crushed stone/rock

The crushed stone/rock would be screened by the screening and sorting facility before transporting to the temporary stockpile via enclosed conveyor.  Water spraying system would be installed.   Dust extraction and collection system (80% dust removal efficiency) would be provided.

 

 

Table 9.6      Temporary Stockpiles – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Kennedy Town Abattoir Site

Loading point

Loading of crushed materials from rock crushing facility onto stockpile

The transportation would be via an enclosed conveyor belt system and water spraying and flexible dust curtains would be provided at the loading point to suppress the dust impact.

 

Storage of materials

Active area for loading & unloading materials

The active area would be minimized to 20% of the total area of the stock piles.  The 80% inactive area would be well covered with impervious sheeting.  Water spraying system would be applied on the active area and watering with complete coverage of active area four times a day would be required.

 

Trucks

Transportation of materials to Barging Point 1

Wheel wash facilities provided at the site exit. The vehicles would be washed before leaving the stockpiles.  The spoils would also be well covered before leaving the site in order to minimise generation of dusty materials.

 

The haul roads within the site would be all paved and water spraying would be provided to keep the wet condition.

 

Western PCWA

Loading point

Loading of crushed materials from rock crushing facility onto stockpile

The transportation would be via an enclosed conveyor belt system and water spraying and flexible dust curtains would be provided at the loading point to suppress the dust impact.

 

Storage of materials

Active area for loading & unloading materials

Water spraying system would be applied on the active area and watering with complete coverage of active area four times a day would be required.

 

Trucks

Transportation of materials to Barging Point 2

The vehicles would be washed before leaving the stockpiles.  The spoils would also be well covered before leaving the site in order to minimise generation of dusty materials.

 

The haul road would all be paved and water spraying would be provided to keep the wet condition.

 

 

Table 9.7      Barging Facilities – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Kennedy Town Abattoir Site

Haul road within barging facilities

Transportation of spoils to Barging Point 1

All road surfaces within the barging facilities would be paved and water spraying would be provided to keep the wet condition.

 

unloading of materials

unloading of spoil materials

The unloading process would be undertaken within enclosed tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point for dust suppression.

 

Trucks

Vehicles leaving the barging facility

Vehicle wheel washing facilities provided at site exit.

 

Western PCWA

Haul road within barging facilities

Transportation of spoils to Barging Point 2

All road surfaces within the barging facilities would be paved and water spraying would be provided to keep the wet condition.

 

Unloading of materials

Unloading of spoil materials from trucks to Barging Point 2

The unloading process would be undertaken within the enclosed tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point for dust suppression.

 

Unloading of spoil materials from enclosed tipping hall to Barging Point 3

The tipping hall would be enclosed structure.  The conveyor from tipping hall to the Barging Point 3 would be enclosed.  Water spraying and flexible dust curtains would be provided at the receiving point of the tipping hall.  Flexible dust curtains and water spraying would be provided at the discharge point of barging facilities for dust suppression.

Trucks

Vehicles leaving the barging facility

Vehicle wheel washing facilities provided at site exit.

 

9.26            The crushing and screening facilities of Rock Crushing Plants at Kennedy Town Abattoir Site and Western PCWA should be enclosed and water spraying would be provided for dust suppression. In accordance with the preliminary design, dust extraction and collection system (80% dust removal efficiency) would be provided for both rock crushing facilities.  The discharge point of dust extraction and collection system installed at the rock crushing facility of Kennedy Town Abattoir Site, is located at least 39m away from the west boundary of the facility.

 

9.27            For the heavy construction works areas of KET Station construction site, 50% of active area and watering with complete coverage of active construction area four times a day are required.  Regarding the works areas of temporary magazine site, 50% of active area and watering with complete coverage of active construction area two times a day are required.

 

9.28            For both rock crushing plants, the requirements and mitigation measures stipulated in the Guidance Note on the Best Practicable Means for Mineral Works (Stone Crushing Plants) BPM 11/1 should be followed and implemented.  The following good site practices should be carried out to further minimize construction dust impact.

(i)             Use of regular watering, with complete coverage, to reduce dust emissions from exposed site surfaces and unpaved roads, particularly during dry weather;

(ii)           Use of frequent watering for particularly dusty construction areas and areas close to ASRs;

(iii)          Side enclosure and covering of any aggregate or dusty material storage piles to reduce emissions.  Where this is not practicable owing to frequent usage, watering shall be applied to aggregate fines;

(iv)          Open stockpiles shall be avoided or covered.  Where possible, prevent placing dusty material storage piles near ASRs;

(v)            Tarpaulin covering of all dusty vehicle loads transported to, from and between site locations;

(vi)          Establishment and use of vehicle wheel and body washing facilities at the exit points of the site;

(vii)         Provision of wind shield and dust extraction units or similar dust mitigation measures at the loading points, and use of water sprinklers at the loading area where dust generation is likely during the loading process of loose material, particularly in dry seasons/ periods;

(viii)       Imposition of speed controls for vehicles on unpaved site roads.  Ten kilometers per hour is the recommended limit;

(ix)         Where possible, routing of vehicles and positioning of construction plant should be at the maximum possible distance from ASRs;

(x)           Every stock of more than 20 bags of cement or dry pulverised fuel ash (PFA) should be covered entirely by impervious sheeting or placed in an area sheltered on the top and the 3 sides;

(xi)         Cement or dry PFA delivered in bulk should be stored in a closed silo fitted with an audible high level alarm which is interlocked with the material filling line and no overfilling is allowed;

(xii)        Loading, unloading, transfer, handling or storage of bulk cement or dry PFA should be carried out in a totally enclosed system or facility, and any vent or exhaust should be fitted with an effective fabric filter or equivalent air pollution control system;

 

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