2        AIR QUALITY

 

2.1              Air Quality Parameters

 

Monitoring and audit of the Total Suspended Particulates (TSP) levels shall be carried out by the ET to ensure that any deteriorating air quality is readily detected and timely action is taken to rectify the situation.

 

1-hour and 24-hour TSP levels should 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 can be measured by direct reading methods which are capable of producing comparable results as that by the high volume sampling method, to indicate short event impacts.

 

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 any other local atmospheric factors affecting or affected by site conditions etc. shall be recorded down in detail.  A sample data sheet is shown in Appendix A.

 

2.2       Monitoring Equipment

 

High volume samplers (HVSs) in compliance with the following specifications shall be used for carrying out the 1-hour and 24-hour 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.

c)      Installed with elapsed-time meter with +/- 2 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-hour 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.

m)    Capable of operating continuously for a 24-hour period.

 

The ET is responsible for providing the monitoring equipment.  They shall ensure that sufficient number 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 labeled.

 

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 recognized primary standard and be calibrated annually.  The calibration record shall be documented and included in the EM&A report for future reference by the concern parties such as ER.  All the data should be converted into standard temperature and pressure condition.

 

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 in the data sheet in Appendix A.

 

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 to prove that the instrument is capable of achieving a comparable result to the HVS.  The instrument should 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.

 

Wind data monitoring equipment shall also be provided and set up at conspicuous locations for logging wind speed and wind direction near to the dust monitoring locations.  The equipment installation location shall be proposed by the ET Leader and agreed with the ER in consultation with the IEC.  For installation and operation of wind data monitoring equipment, the following points shall be observed:

 

a)      The wind sensors shall be installed 10m above ground so that they are clear of obstructions or turbulence caused by buildings;

b)      The wind data shall be captured by a data logger. The data shall be down loaded for analysis at least once a month;

c)      The wind data monitoring equipment shall be re-calibrated at least once every six months; and

d)      Wind direction shall be divided into 16 sectors of 22.5 degrees each.

 

In exceptional situations, the ET Leader may propose alternative methods to obtain representative wind data upon approval from the ER and agreement from IEC.

 

2.3       Laboratory Measurement / Analysis

 

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 accredited by HOKLAS or other internationally recognized accreditation.

 

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 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 of 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.

 

Filter paper of size 8”x10” shall be labeled before sampling.  It shall be a clean filter paper with no pinholes, and shall be conditioned in a humidity-controlled chamber for over 24-hour and be pre-weighed before use for the sampling.

 

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 readout down to 0.1 mg.  The balance shall be regularly calibrated against a traceable standard.

 

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

 

2.4       Monitoring Location

 

The proposed 24-hour TSP monitoring station is listed in Table 2.1 and location is shown in Figure 2.1.  The location has been chosen based on the most likely affected sensitive receptor in the vicinity of the proposed site.  Tuen Mun Wu Hong Clinic was not identified as one of the air quality monitoring stations because the clinic does not rely on openable window for ventilation. 

 

Table 2.1         Proposed Air Quality Monitoring Station

Identification No.

Location

ASR1

Block 15, Yuet Wu Villa

 

If for whatever reasons it is necessary to establish alternative monitoring stations, the ET shall propose the alternative monitoring locations and seek approval from ER and agreement from EPD.

 

When selecting alternative monitoring locations, 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;

c)      Take into account the prevailing meteorological conditions.

 

The ET Leader shall agree with the ER in consultation with the IEC the position of the installation of the HVS.  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 meters 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 meters of separation from walls, parapets and penthouses is required for rooftop samplers;

e)      A minimum of 2 meters 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 meters from the drip line;

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 required to operate the samplers.

 

2.5       Baseline Monitoring

 

Baseline monitoring shall be carried out at the designated monitoring location for at least 14 consecutive days prior to the commissioning of the construction works to obtain daily 24-hour TSP samples.  The selected baseline monitoring stations should reflect baseline conditions at the impact stations.  1-hour sampling shall also be done at least 3 times per day whilste the highest dust impact is expected.  Before commencing baseline monitoring the ET shall inform the IEC of the baseline monitoring programme such thatso the IEC can conduct on-site audit to ensure accuracy of the baseline monitoring results.

 

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

 

In case the baseline monitoring cannot be carried out at the designated monitoring location during the baseline monitoring period, the ET Leader shall carry out the monitoring at alternative location which can effectively represent the baseline condition at the impact monitoring location.  The alternative baseline monitoring location shall be approved by the ER and agreed with IEC.

 

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

 

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

 

2.6       Impact Monitoring

 

The ET Leader shall carry out impact monitoring during the course of the Works.  For regular impact monitoring, the sampling frequency of at least once in every six-days, shall be strictly observed at the monitoring station for 24-hr TSP monitoring.  For 1-hr TSP monitoring, the sampling frequency of at least three times in every six-days should be undertaken when the highest dust impact occurs.  Before commencing baseline monitoring, the ET Leader shall inform the IEC of the impact monitoring programme such thatso the IEC can conduct on-site audit to ensure accuracy of the impact monitoring results.

 

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

 

In case of non-compliance with the air quality criteria, more frequent monitoring, as specified in the Action Plan in Table 2.2, 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.

 

2.7       Event and Action Plan for Air Quality

 

The baseline monitoring results form the basis for determining the air quality criteria for the impact monitoring.  The ET Leader shall compare the impact monitoring results with air quality criteria set up for 24-hour TSP and 1-hour TSP.  Table 2.2 shows the air quality criteria, namely Action and Limit levels to be used.  Should non-compliance of the air quality criteria occur, actions in accordance with the Action Plan in Table 2.3 should be carried out.

 

Table 2.2         Action / Limit Levels for Air Quality

Parameters

Action Level

Limit Level

24 Hour TSP Level in µg/m3

For baseline level £ 200 µg/m3, Action 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, Action level = (Baseline level*1.3 + Limit Level)/2;

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

500

 

Table 2.3         Event / Action Plan for Air Quality

EVENT

ACTION

ET

IEC

ER

CONTRACTOR

ACTION LEVEL

 

 

 

 

1.  Exceedance for one sample

1.   Identify source

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.   Repeat measurements to confirm findings

4.   Increase monitoring frequency to daily

5.   Discuss with IEC and Contractor on remedial actions required

6.   If exceedance continues, arrange meeting with IEC and ER

7.   If exceedance stops, cease additional monitoring;

1.    Check monitoring data submitted by ET

2.    Check Contractor’s working method

3.    Discuss with ET 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 are properly implemented

1.    Submit proposals for remedial actions to IEC 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 ER, EPD

3.   Repeat measurement to confirm finding

3.   Increase monitoring frequency to daily

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

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 failure in writing

2.   Notify Contractor

3.   Ensure remedial measures are properly implemented

1.   Take immediate action to avoid further exceedance

2.   Submit proposals for remedial actions to IEC within 3 working days of notification;

3.   Implement the agreed proposals;

4.  Amend proposal if appropriate.

 

Table 2.3         Event / Action Plan for Air Quality

EVENT

ACTION

ET

IEC

ER

CONTRACTOR

LIMIT LEVEL

 

 

 

 

2.  Exceedance for two or more consecutive samples

1.    Identify source

2.    Notify ER and  EPD the causes & actions taken for the exceedances

3.    Repeat measurement to confirm findings

4.    Increase monitoring frequency to daily

5.    Investigate the causes of exceedance

6.    Arrange meeting with EPD and ER to discuss the remedial actions to be taken

7.    Assess effectiveness of Contractor’s remedial actions and keep 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 failure 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 are 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 IEC 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 abated

 

2.8       Air Quality Mitigation Measures

 

The EIA report has discussed in general terms the appropriate dust control and

mitigation measures during the construction and operational phases, these are provided in more detail below. The Contractor shall implement dust suppression measures which shall include, but not be limited to, the following:

 

·        The area in which excavation takes place shall be sprayed with water immediately prior to, during and immediately after the excavation to minimisze dust generation.

·        Any debris from the construction of the WFM shall be covered entirely by impervious sheeting or stored in a sheltered debris collection area.

·        Any dusty material remaining after a stockpile of cement or other materials is removed shall be wetted and removed from the surface of roads.

·        Every stock of more than 20 bags of cement shall be covered entirely by imperious sheeting or placed in a sheltered area.pile of dusty material shall be either (a) covered entirely by impervious sheeting; (b) placed in an area sheltered on the top and the three sides; or (c) sprayed with water or a dust suppression chemical so as to maintain the entire surface wet.

·        Cement bags or any other dusty materials collected during the work shall be disposed of in totally enclosed containers.

·        All dusty materials shall be sprayed with water immediately prior to any loading, unloading or transfer operation so as to minimisze the dusty materials wet.

·        Conveyor belts shall be fitted with windboards, and conveyor transfer points and hopper discharge areas shall be enclosed to minimisze dust emission.  All conveyors carrying materials which have the potential to create dust shall be totally enclosed and fitted with belt cleaners.

·        Any skip hoist for the transport of construction wastes shall be properly enclosed.

·        Vehicle washing facilities, including a high-pressure water jet, shall be provided at the designated vehicle exit point.  Every vehicle shall be washed immediately before leaving the construction site to remove any dust materials from its wheels and body.

·        The area where vehicle washing takes place and the section of the road between the washing facilities and the exit point, as well as the main haul road to the construction site shall be paved with concrete, bituminous materials, hardcore or metal plates and kept clear of dusty materials.

·        The main haul road to the site shall be sprayed with water to keep the entire road surface wet and to minimisze dust generation.

·        Hoarding of not less than 2.4m high shall be provided along the site boundary section that adjoins a road, street, service land or other area accessible to the public.

 

If the above measures are not sufficient to restore the air quality to acceptable levels upon the advice of ET Leader, the Contractor shall liaise with the ET Leader on some other mitigation measures, propose to ER for approval, and implement the mitigation measures.