9                     AIR QUALITY

 

Introduction

 

9.1                 Potential air quality impact arising from the construction works would mainly be related to construction dust from excavation, materials handling, spoil removal and wind erosion, as well as operation of concrete batching plant, temporary stockpiles and barging facilities.  Construction dust monitoring and site audit is recommended to confirm that the recommended mitigation measures are properly implemented.

 

9.2                 There would be no adverse air quality impact anticipated from the operation of the Project.  With the provision of mechanical air ventilation system fulfilling with EPD Public Transport Interchange (PTI) guideline, no adverse air quality impact would be expected.  Therefore, no specific environmental monitoring and audit requirements are required during operation phase.

 

Objectives of Dust Monitoring

 

9.3                 The objectives of the dust monitoring should 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.

 

Monitoring Parameters and Equipment

 

9.4                 The total suspended particulate (TSP) levels should 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 (hereinafter referred to as “HVS method”).

 

9.5                 Dust laden with air should 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.

 

9.6                 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, should be recorded down in detail.  A sample data sheet is shown in Appendix B.

 

9.7                 HVS in compliance with the following specifications should 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; and

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

 

9.8                 The ET should be responsible for the provision of the monitoring equipment. He should ensure that sufficient number of HVSs with appropriate calibration kit is available for carrying out the baseline monitoring, regular impacts monitoring and ad-hoc monitoring.  The HVSs should 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, should be clearly labelled.

 

9.9                 Initial calibration of HVSs with mass flow controller should be conducted upon installation and thereafter every six months. Calibration should be done using an orifice calibrator. The calibration data should be properly documented for future reference by the IEC.

 

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

 

9.11             If the ET Leader proposes alternative dust monitoring equipment / methodology (e.g. direct reading methods) after this manual is issued, the ET should seek agreement from the IEC on the alternative dust monitoring equipment / methodology.

 

Proposed Dust Monitoring Stations

 

9.12             The worst affected locations in the vicinity of the construction activities of the Project identified for dust monitoring are listed in Table 9.1 and shown in Figure Nos. NOL/ERL/300C/XRL/ENS/M62/600 to 612.

 

Table 9.1      Proposed Dust Monitoring Locations

Construction Work Site

Identification No.

Air Monitoring Location

Mai Po Ventilation Building (MPV)

AM1

House 5, Phase A, Royal Palms

Ngau Tam Mei Ventilation Building (NTV)

AM2

Yau Tam Mei Village House

Tai Kong Po Emergency Access Point (TPP)

AM3

Kong Tai Road Village House

Shek Kong Stabling Sidings (SSS) and Emergency Rescue Station (ERS)

AM4

DD110 LOT 482, Wang Toi Shan

 

AM5

Leung Uk Tsuen Squats

 

AM6

630 Sheung Tsuen

Tse Uk Tsuen Construction Shaft (TUW)

AM7

Tse Uk Tsuen

Pat Heung Ventilation Building (PHV)

AM8

No. 305, Sheung Tsuen San Tsuen Village House

Shing Mun Ventilation Building (SMV)

AM9

Sau Shan House, Cheung Shan Estate

Shek Yam Works Area (SYW)

AM10

No. 168, Yau Ma Hom Resite Village

Kwai Chung Ventilation Building (KCV)

AM11

Wah Wing Industrial Building

Mei Lai Road Construction Shaft (MLW)

AM12

Po Leung Kuk Tong Nai Kan College

Nam Cheong Ventilation Building (NCV)

AM13

St. Andrew Primary School

Mong Kok West Ventilation Building (MKV)

AM14

Yaumati Catholic Primary School (Hoi Wang Road)

West Kowloon Terminus (WKT)

AM15

Sorrento Tower 6

 

AM16

The Arch Moon Tower

 

AM17

Tsim Sha Tsui Fire Station

 

9.13             The status and locations of air quality sensitive receivers may change after this manual is issued. In such cases exist, the ET Leader should propose updated monitoring locations and seek approval from ER and agreement from the IEC and EPD.

 

9.14             When alternative monitoring locations are proposed, the monitoring locations should 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 EIAO-TM; and

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

 

9.15             When positioning the HVSs, the following points should be noted:

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

(ii)          no two samplers should be placed less than 2m 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 2m separation from walls, parapets and penthouses is required for rooftops samplers;

(v)          a minimum of 2m 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 20m from the dripline;

(ix)        any wire fence and gate to protect the sampler, should 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

 

9.16             Baseline monitoring should 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. Before commencing the baseline monitoring, the ET leader should inform the IEC of the baseline monitoring programme such that the IEC can conduct on-site audit to ensure accuracy of the baseline monitoring results.  

 

9.17             TSP baseline monitoring should be carried out for a continuous period of at least two weeks with the 24-hour and three sets of 1-hour ambient measurements taken daily at each monitoring location.  During the baseline monitoring, there should not be any construction or dust generating activities in the vicinity of the monitoring stations. General meteorological conditions (wind speed, direction and precipitation) and notes regarding any significant adjacent dust producing sources should also be recorded throughout the baseline monitoring period.   A summary of baseline monitoring is presented in Table 9.2.

 

9.18             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.

 

9.19             If the ET Leader 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

 

9.20             The monthly schedule of the compliance and impact monitoring programme should be drawn up by the ET one month prior to the commencement of the scheduled construction period. 

 

9.21             For regular 24-hour TSP impact monitoring, a sampling frequency of at least once in every six days should be strictly observed at the monitoring stations when there are Project related construction activities being undertaken within a radius of 300m from these monitoring stations. In case of complaints, 1-hour TSP monitoring should 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      Summary of Dust Monitoring Programme

Monitoring Period

Duration

Sampling Parameter

Frequency

Baseline Monitoring

Consecutive days of at least 2 weeks before commencement of construction works

1 hour TSP

·       3 times per day

Continuous 24-hour TSP

·       Daily

Impact Monitoring

Throughout the construction phase*

1 hour TSP

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

Continuous 24-hour TSP

·       Once every 6 days

* Impact monitoring should be conducted at the monitoring stations for 24-hour TSP monitoring when there are Project related construction activities being undertaken within a radius of 300m from these monitoring stations.

 

9.22             Before commencement of the monitoring, the ET should 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

 

9.23             Action and Limit (A/L) levels that provide an appropriate framework for the interpretation of monitoring results have to be agreed between ET, IEC, EPD and the ER before commencement of the air monitoring.  The air quality monitoring data should 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

 

9.24             The Event and Action Plan prescribes procedures and actions associated with the outcome of the comparison of air quality results recorded by the environmental monitoring process and the agreed A/L levels.  In the cases where exceedance of these A/L levels occurs, the ET, the IEC, the ER and the Contractor should strictly observe the relevant actions of the respective Event and Action Plan listed in Table 9.4.


Table 9.4       Event and Action Plan for Construction Dust Monitoring

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

 

9.25             Dust mitigation measures stipulated in the Air Pollution Control (Construction Dust) Regulation should be implemented to control dust emissions from all construction work sites. 

 

·         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 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.

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

·         Establishment and 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.  8 kilometers per hour is the recommended limit.

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

·         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.

·         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.

·         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.

 

9.26             Information on the preliminary engineering design indicates that a concrete batching plant will likely be required. The operation of the concrete batching plant is classified as a Specified Process (SP), for which a licence under Air Pollution Control Ordinance (APCO) is required.  The requirements and mitigation measures stipulated in the Guidance Note on the Best Practicable Means for Cement Works (Concrete Batch Plant) BPM 3/2(93) should be followed and implemented.  Dust control measures have been incorporated into the design of the concrete batching plant, stockpile areas and barging facilities (Figure Nos. NOL/ERL/300/C/XRL/ENS/M50/004 to 015), as presented in Tables 9.5, 9.6 and 9.7, respectively.  Details of the remaining recommended mitigation measures are presented in Appendix A.

 

Table 9.5      Concrete Batching Plant – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Unloading of raw materials

Unloading of aggregates from the tipper trucks to receiving hopper.

The receiving hopper would be equipped with enclosures on 3 sides and top cover, and water spraying system.

 

Unloading of cement and PFA from tankers into the silo.

The cement and PFA would be directly loaded into the silo via a flexible duct. Dust collectors should be installed at cement/PFA silos.

Transfer of raw materials

Storage of aggregates in overhead storage bins.

The aggregates would be stored in fully enclosed overhead storage bins.  The top of overhead storage bins would be covered with cladding.  Water spraying system would be installed at the top of storage bins for watering the aggregates, and aggregate storage bins would be fully enclosed. 

 

Batching of raw materials

Weighing and Batching of cementitious materials

The whole process of weighing and mixing would be performed in a fully enclosed environment.  The mixers would all equip with dust collectors.

 

Truck loading

Loading of concrete from  mixer into transit mixer of a truck

The concrete would be directly loaded from the mixer into the transit mixer of a truck in “wet” form.

 

Trucks

Tipper trucks and cement tankers within the site.

Haul road within the site is paved.  Wheel washing pit would be installed at the gate of the concrete batching plant. Water spraying system would be installed along the haul road.

 

 

Table 9.6      Cut and Cover Areas and Stockpiles – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Cut & Cover Areas and Stockpiles in the vicinity of adits/shafts

Heavy construction activities at Cut & Cover Areas,  Storage of materials at Stockpiles

Active areas for heavy construction activities,  loading & unloading materials at stockpiles

The specified requirements for cut & cover areas and stockpiles at Shek Kong, Nam Cheong and West Kowloon works areas are as follows:

(i) Shek Kong works area – active area minimized to 15% of total area, watering with complete coverage of active area ten times a day.

(ii) Nam Cheong works area – active area minimized to 30% of total area, watering with complete coverage of active stockpile area four times a day.

(iii) West Kowloon works area – active area minimized to 15% of total area, watering with complete coverage of active area eight times a day.

 

For other sites, the active area would be minimized to 30% of the total area, 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. 

 

The remaining inactive area would be well covered with impervious sheeting at all work sites. 

 

Trucks

Transportation of materials to Barging Point

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.

 

For the Shek Kong works area, watering paved haul roads once per hour would be provided.  

 

Temporary stockpiles in the vicinity of barging points

Loading point

Loading of spoils from  trucks onto stockpile

Water spraying would be provided at the loading points.

 

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.

 

 

 

Table 9.7      Barging Facilities – Dust Emission Design Control Measures

Process

Description

Dust Emission Design Control Measures

Haul road within barging facilities

Transportation of spoils to the Barging Point

All road surfaces within the barging facilities would be paved and water spraying would be provided to keep the wet condition.  For haul roads at West Kowloon and Nam Cheong works areas to the barging points, watering haul road once per hour would be provided.

 

Unloading of materials

Unloading of spoil materials to the barge

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

 

Trucks

Vehicles leaving the barging facility

Vehicle wheel washing facilities provided at site exit.

 

Transportation of spoils (only for one of Nam Cheong Barging Point)

Transportation of spoils to Nam Cheong Barging Point

Fully enclosed conveyor system would be adopted for transportation of spoils from shaft to the barging point.