7.                   AIR QUaLITY

Introduction

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

7.2               The objectives of the air quality monitoring shall be:

·         to identify the extent of construction dust impacts on sensitive receivers

·         to determine the effectiveness of mitigation measures to control fugitive dust emission from activities during construction phase

·         to audit the compliance of the Contractor with regard to dust control, contract conditions and the relevant dust impact criteria

·         to recommend further mitigation measures if found to be necessary

·         to comply with Action and Limit (A/L) Levels for air quality as defined in this Manual

 

Methodology and Criteria

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

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

·         The statutory 1-hour TSP limit of 500mg m-3

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

Monitoring Equipment

7.5               1-hour and 24-hour TSP levels shall be measured to indicate the impacts of construction dust. 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.

7.6               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.

7.7               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.

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

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

·         equipped with a timing / control device with ± 5 minutes accuracy for 24 hours operation.

·         installed with elapsed-time meter with ± 2 minutes accuracy for 24 hours operation.

·         capable of providing a minimum exposed area of 406 cm2 (63 in2).

·         flow control accuracy:  ± 2.5% deviation over 24-hour sampling period.

·         incorporated with an electronic mass flow rate controller or other equivalent devices.

·         equipped with a flow recorder for continuous monitoring.

·         provided with a peaked roof inlet.

·         incorporated with a manometer.

·         able to hold and seal the filter paper to the sampler housing at horizontal position.

·         easy to change the filter.

·         capable of operating continuously for 24-hour period.

7.9               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.

7.10            The flow rate of each HVS with mass flow controller shall be calibrated using an orifice calibrator.  Initial calibration of the dust monitoring equipment shall be conducted upon installation and prior to commissioning.  One point flow rate calibration shall be carried out every two months.  Five-point calibration shall be carried out every six months.

7.11            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.

Monitoring Locations

7.12            Three potentially worst affected locations have been identified for TSP dust monitoring as shown in Table 7.1 and illustrated in Figure 7.1.  Prior to the commencement of the EM&A programme, the proposed air quality monitoring stations shall be discussed and agreed with the Engineer, the ET and IEC.  EPD shall also be informed of the proposal.

Table 7.1          Air Monitoring Stations during Construction Phase

Identification No.

ASR ID in EIA Report

Air Quality Monitoring Location

AM1

AL16

Tennis Court adjacent to Wong Chuk Hang Road

AM2

AL5

The Hazelton

AM3

AL12

Open Area of Police Training School

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

·         monitoring at sensitive receivers close to the major site activities which are likely to have air quality impacts.

·         monitoring at the air sensitive receivers as defined in the Technical Memorandum.

·         assurance of minimal disturbance to the occupants during monitoring.

7.14            When positioning the HVS samplers, the following points shall be noted:

·         a horizontal platform with appropriate support to secure the samples against gusty wind shall be provided.

·         no two samplers shall be placed less than 2 m apart.

·         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.

·         a minimum of 2 m separation from walls, parapets and penthouses is required for rooftops samplers.

·         a minimum of 2 m separation from any supporting structure, measures horizontally is required.

·         no furnace or incinerator flue is nearby.

·         airflow around the sampler is unrestricted.

·         the sampler is more than 20 m from the dripline.

·         any wire fence and gate to protect the sampler, shall not cause any obstruction during monitoring.

·         permission must be obtained to set up the samplers and to obtain access to the monitoring stations.

·         a secured supply of electricity is needed to operate the samplers.

Baseline Monitoring

7.15            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.

7.16            TSP baseline monitoring shall be carried out for a continuous period of at least 14 days 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.

7.17            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.

7.18            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 and the IEC.  EPD shall also be informed of the proposed arrangement.

Impact Monitoring

7.19            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.  1-hour TSP monitoring shall also 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 7.2.

Table 7.2          Impact Monitoring Programme (TSP)

Sampling duration

Frequency

1 hour

3 times every 6 days

24 hours

Once every 6 days

7.20            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

7.21            Action and Limit levels that provide an appropriate framework for the interpretation of monitoring results have to be agreed between ET, IEC and the Engineer before commencement of the air monitoring.  EPD shall also be informed of the proposal.  The air quality monitoring data shall be checked against the agreed A/L levels.  Recommended A/L levels are listed in Table 7.3.

Table 7.3          Proposed Action and Limit Levels for Impact Monitoring

Parameter

Action Level (1)

Limit Level

TSP (24 hour average)

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

·         BL > 200 mg m-3, AL = LL

260 mg m-3

TSP (1 hour average)

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

·         BL > 384 mg m-3, AL = LL

500 mg m-3

            BL = Baseline level, AL = Action level, LL = Limit level.

 

Event and Action Plan

7.22            The principle upon which the Event and Action Plan 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 ER and the Contractor shall strictly observe the relevant actions listed in Table 7.4.

 

Table 7.4          Event / Action Plan for Air Quality

Event

Action

Action Level

ET

Contractor

ER

IEC

Exceedance for one sample

1.    Identify source

2.    Notify IEC, ER and Contractor

3.    Conduct additional monitoring to investigate the causes.

4.    Report the investigation results and if exceedance is due to contractor’s construction works to the IEC, ER and Contractor.

5.    Increase monitoring frequency to once per 2 days for 24-hour TSP and daily for 1-hour TSP until exceedance stops if exceedances are considered related to contractor’s construction works and report the results to IEC, ER and Contractor.

1.    Take immediate action to avoid further exceedance and rectify any unacceptable practice.

2.    Submit air mitigation proposal to IEC and ER for agreement if ET indicated that exceedance is related to the construction works

3.    Implement agreed proposal within a time scale agreed with ER and IEC.

1.    Confirm receipt of notification of failure in writing.

2.    Notify Contractor.

3.    Require Contractor to submit air mitigation proposal.

4.    Ensure remedial measures are properly implemented.

1.    Review monitoring data and investigation report submitted by ET.

2.    Review Contractor’s air mitigation proposal and advise the ER accordingly.

3.    Supervise and confirm in writing the implementation of remedial measures.

Exceedance for two or more consecutive samples

1.    Identify source

2.    Notify EPD, IEC, ER and Contractor

3.    Conduct additional monitoring to investigate the causes.

4.    Report the investigation results and if exceedances are due to contractor’s construction works to EPD, IEC, ER and Contractor within 3 working days after additional monitoring.

5.    Increase monitoring frequency to daily for 24-hour TSP and 1-hour TSP if exceedances are considered related to contractor’s construction works until exceedance stops, and report the results to EPD, IEC, ER and Contractor.

6.    If exceedances continue after 1-week monitoring events, request ER to arrange meeting with ER, IEC and contractor to discuss remedial actions.

1.    Take immediate action to avoid further exceedance and rectify any unacceptable practice

2.    In consultation with the IEC, submit air mitigation proposal to IEC and ER for agreement within 3 working days of notification if ET indicated that exceedances are related to construction works

3.    Implement agreed proposal within a time scale agreed with ER and IEC.

4.    Amend working methods if appropriate.

1.    Confirm receipt of notification of failure in writing.

2.    Notify Contractor.

3.    Require Contractor to submit air mitigation proposal.

4.    Ensure remedial measures are properly implemented.

1.    Review monitoring data and investigation report submitted by ET.

2.    Discuss amongst ER, ET and Contractor in order to formulate air mitigation proposal.

3.    Review Contractor’s air mitigation proposal and advise the ER accordingly.

4.    Supervise and confirm in writing the implementation of remedial measures.

Event

Action

Limit Level

ET

Contractor

ER

IEC

Exceedance for one sample

1.    Identify source

2.    Notify EPD, IEC, ER and Contractor

3.    Conduct additional monitoring to investigate the causes.

4.    Report the investigation results and if exceedances are due to contractor’s construction works to EPD, IEC, ER and Contractor within 3 working days after additional monitoring.

5.    Increase monitoring frequency to daily if exceedances are considered related to contractor’s construction works until exceedance stops, and report the results to EPD, IEC, ER and Contractor.

1.    Take immediate action to avoid further exceedance and rectify any unacceptable practice

2.    In consultation with the IEC, submit air mitigation proposal to IEC and ER for agreement within 3 working days of notification if ET indicated that exceedances are related to construction works

3.    Implement agreed proposal within a time scale agreed with ER and IEC.

4.    Amend working methods if appropriate.

1.    Confirm receipt of notification of failure in writing.

2.    Notify Contractor.

3.    Require Contractor to submit air mitigation proposal.

4.    Ensure remedial measures are properly implemented.

1.    Review monitoring data and investigation report submitted by ET.

2.    Discuss amongst ER, ET and Contractor in order to formulate air mitigation proposal.

3.    Review Contractor’s air mitigation proposal and advise the ER accordingly.

4.    Supervise and confirm in writing the implementation of remedial measures.

Exceedance for two or more consecutive samples

1.    Identify source

2.    Notify EPD, IEC, ER and Contractor

3.    Conduct additional monitoring to investigate the causes.

4.    Report the investigation results and if exceedances are due to contractor’s construction works to EPD, IEC, ER and Contractor within 3 working days after additional monitoring.

5.    Increase monitoring frequency to daily if exceedances are considered related to contractor’s construction works until exceedance stops, and report the results to EPD, IEC, ER and Contractor.

6.    If exceedances continue after 2 consecutive monitoring events, request ER to arrange meeting with IEC and contractor to discuss remedial actions.

1.    Take immediate action to avoid further exceedance and rectify any unacceptable practice

2.    In consultation with the IEC, submit air mitigation proposal to IEC and ER for agreement within 3 working days of notification if ET indicated that exceedances are related to construction works

3.    Implement agreed proposal within a time scale agreed with ER and IEC.

4.    Amend working methods and proposal if appropriate.

5.    Stop relevant portion(s) of works as required by ER, ET and IEC

1.    Confirm receipt of notification of failure in writing.

2.    Notify Contractor.

3.    Require Contractor to submit air mitigation proposal.

4.    Ensure remedial measures are properly implemented.

5.    If exceedances continue arrange meeting with Contractor, IEC and ET and to consider what portion(s) of works should be further mitigated or have to stop.

1.    Review monitoring data and investigation report submitted by ET.

2.    Discuss amongst ER, ET and Contractor in order to formulate air mitigation proposal.

3.    Review Contractor’s air mitigation proposal and advise the ER accordingly.

4.    Supervise and confirm in writing the implementation of remedial measures.

Mitigation Measures

Construction Phase

7.23            The EIA Report recommended air quality control and mitigation measures during the construction phase of the Project in accordance with the Air Pollution Control (Construction Dust) Regulation and good site practices are summarised below.

·         Use of regular watering, with complete coverage, to reduce dust emissions from exposed site surfaces and unpaved roads, particularly during dry weather.

·         Use of frequent watering for particularly dusty construction areas, temporary stockpiles and areas close to ASRs.

·         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.

·         Open stockpiles shall be avoided or covered.  Where possible, prevent placing dusty material storage piles near ASRs.

·         Restricting heights from which materials are dropped, as far as practicable to minimise the fugitive dust arising from unloading/ loading.

·         Tarpaulin covering of all dusty vehicle loads transported to, from and between site locations.

·         Use of vehicle wheel and body washing facilities at the exit points of the site.

·         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.

·         Imposition of speed controls for vehicles on unpaved site roads.  Ten kilometers per hour is the recommended limit.

·         Dusty activities should be re-scheduled if high-wind conditions are encountered.

·         Where possible, routing of vehicles and positioning of construction plant should be at the maximum possible distance from ASRs.

·         Suitable buffer zone should be provided and the works areas should be fenced off with hoarding.  The height of hoarding should not be less than 2.4m from ground level.

Drilling & Blasting

7.24            The following mitigation measures would be adopted for drilling & blasting activities:

§     Watering on the exposed area after blasting.

§     Use of vacuum extraction drilling methods.

§     Carefully sequenced blasting.

§     Firing of explosive would be carried out in the morning prior to opening of the Park.

Crushing Plant

7.25            The following mitigation measures would be adopted for temporary crusher:

§     Water sprays on the crusher.

§     Fabric filters installed for the crushing plant.

§     When transferring materials from crusher to the conveyors, chutes or dust curtains would be used for controlling dust.

 

Barging Point & Conveyor Belt System

7.26            To ensure negligible dust emission from the barging point and conveyor belt system, the following measures would be adopted:

§     The conveyors would be placed within a totally enclosed structure (see Figure 3.5 and 3.6).

§     Profiled steel cladding would be provided at two sides of loading point.

§     Dust suppression sprays would be installed and operated in strategic locations at the feeding inlet and outlet.

§     The barging point would be placed within a totally enclosed structure incorporating an enclosed chute for material transfer to the barge. Flexible curtain would be hanged on the enclosed chute prevent dust emission when excavated materials/rocks transported into the barge.

7.27            Some areas of the Park would remain open for visitors during the construction period.  Therefore, suitable buffer zones from major construction activities should be provided where practical and the works areas should be fenced off with hoarding during the construction phase.   It is recommended to erect hoarding of a height not less than 2.4m from ground level.

Operational Phase

7.28            No adverse air quality impact on the ASRs in the vicinity of the Park is expected during operational phase of the Project.  Environmental monitoring and audit is considered not necessary.

7.29            The implementation schedule for the recommended air quality impact mitigation measures is presented in Appendix B.