2.1.1 Dust impacts would be the major air quality impacts during the construction phase of the project. The following sections detailed the approaches, criteria and guidelines on monitoring and managing dust impacts.
2.1.2 Dust would be the key environmental issue during construction. It is necessary to monitor the dust generates from the construction activities after timely implementation of the mitigation measures listed in Section 2.9 in this Manual. The purpose of monitoring is to ascertain that the dust levels would comply with the 1- hour average and 24-hour average Total Suspended Particulate (TSP) criteria at the sensitive receivers, and that the recommended mitigation measures are effective in suppressing dust levels.
2.1.3 The objectives of the monitoring are:
(a) To identify the extent of construction dust impacts on
nearby sensitive receivers;
(b) To determine the effectiveness of the recommended dust mitigation measures
to control dust from construction activities;
(c) To recommend further mitigation measures where necessary; and
(d) To ascertain that the dust levels would comply with the 1-hour average and
24-hour average Total Suspended Particulates (TSP) criteria at nearby sensitive
receivers as defined in this EM&A Manual.
2.2.1 Monitoring and audit of the TSP levels should be carried out by the ET Leader to ensure that any deteriorating air quality could be readily detected and timely and appropriate action undertaken to rectify the situation.
2.2.2 1-hour and 24-hour TSP levels should be measured to indicate the impacts of dust on air quality. The TSP levels should 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.
2.2.3 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, other local atmospheric factors affecting or affected by site conditions and work progress of the concerned site etc. should be recorded down in details. A sample data record sheet is shown in Appendix B-1 for reference.
2.3.1 High volume sampler (HVS) in compliance with the
following specifications should be used for carrying out the 1-hour and 24-hour
TSP monitoring:
(a) 0.6-1.7m3/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 406cm2 (63in2);
(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; and
(m) capable of operating continuously for 24-hour period.
2.3.2 The ET Leader should be responsible for provision of the monitoring equipment. He/she should 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 should 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. should be clearly labelled.
2.3.3 Initial calibration of dust monitoring equipment should be conducted by the ET upon installation and thereafter at bi-monthly intervals. The transfer standard should be traceable to the internationally recognised primary standard and be calibrated annually. The calibration data should be properly documented for future reference by the concerned parties such as the IEC. 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 should be verified to be constant and be recorded down in the data sheet (see Appendix B-1A).
2.3.5 If the ET Leader proposes to use a direct reading dust meter to measure 1-hour TSP levels, he/she should submit sufficient information to the IEC to prove that the instrument is capable of achieving a comparable result as that of the HVS and may be used for the 1-hour sampling. The instrument should also be calibrated regularly, and the 1-hour sampling should be determined periodically by HVS to check the validity and accuracy of the results measured by direct reading method.
2.3.6 Wind data monitoring equipment should 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 should 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 should be observed:
(a) the wind sensors should be installed on masts at an
elevated level 10m above ground so that they are clear of obstructions or
turbulence caused by the buildings;
(b) the wind data should be captured by a data logger. The data recorded in the
data logger should be downloaded periodically for analysis at least once a
month;
(c) the wind data monitoring equipment should be re-calibrated at least once
every six months; and
(d) wind direction should be divided into 16 sectors of 22.5 degrees each.
2.3.7 In exceptional situations, the ET Leader may propose alternative methods to obtain representative wind data upon approval from the ER and agreement from the IEC.
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, should be available for sample analysis, and equipment calibration and maintenance. The laboratory should be HOKLAS accredited or other internationally accredited laboratory.
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 in consultation with the IEC. Measurement performed by the laboratory should be demonstrated to the satisfaction of the ER and the IEC.
2.4.3 The IEC should conduct regular audit to the measurement performed by the laboratory so as to ensure the accuracy of measurement results. The ET Leader should provide the ER with one copy of the Title 40 of the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B for his/her reference.
2.4.4 Filter paper of size 8"x10" should be labelled before sampling. It should be a clean filter paper with no pinholes, and should be conditioned in a humidity-controlled chamber for over 24-hour and be pre-weighed before use for the sampling.
2.4.5 After sampling, the filter paper loaded with dust should be kept in a clean and tightly sealed plastic bag. The filter paper is then returned to the laboratory for reconditioning in the humidity-controlled chamber followed by accurate weighing by an electronic balance with a readout down to 0.1mg. The balance should be regularly calibrated against a traceable standard.
2.4.6 All the collected samples should be kept in a good condition for 6 months before disposal.
2.5.1 Impact monitoring of dust shall be carried out at representative Air Sensitive Receivers (ASRs) whenever there is ongoing construction work during construction phase of SWC. Two dust monitoring stations are proposed to set up at SWC-AN1 (AP 8109) and SWC-AN2 (AP 8125) which are the village houses at Ngau Hom Shek during construction phase. Figure EM2.1 shows the locations of the proposed dust monitoring locations.
2.5.2 Exact monitoring point for sensitive receivers shall be selected as close as is practical to the construction work boundary. The status and locations of dust sensitive receivers may change after issuing this Manual. If such cases exist, the ET Leader should propose updated monitoring locations and seek approval from ER and agreement from the IEC.
2.5.3 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 air sensitive receivers;
(c) proper position/siting and orientation of the monitoring equipment; and
(d) take into account the prevailing meteorological conditions.
2.5.4 The ET Leader should agree with the ER in consultation with the IEC the position of the HVS for installation of the monitoring equipment. When positioning the samplers, the following points should 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 meter 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 of separation from walls, parapets and penthouses is
required for rooftop samplers;
(e) a minimum of 2 metre 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.
2.6.1 The ET Leader should carry out baseline monitoring at all of the designated monitoring locations for at least 14 consecutive days prior to the commissioning of the construction works to obtain daily 24-hour TSP samples. 1-hour sampling should also be done at least 3 times per day while the highest dust impact is expected. 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.
2.6.2 During the baseline monitoring, there should not be any construction or dust generation activities in the vicinity of the monitoring stations.
2.6.3 In case the baseline monitoring cannot be carried out at the designated monitoring locations during the baseline monitoring period, the ET Leader should carry out the monitoring at alternative locations which can effectively represent the baseline conditions at the impact monitoring locations. The alternative baseline monitoring locations should be approved by the ER and agreed with IEC.
2.6.4 In exceptional case, when insufficient baseline monitoring data or questionable results are obtained, the ET Leader should 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.
2.6.5 Ambient conditions may vary seasonally and should 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. Should 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.
2.7.1 The ET Leader should carry out impact monitoring during construction phase of SWC. For regular impact monitoring, the sampling frequency of at least once in every six-days, should be strictly observed at all the monitoring stations for 24-hour TSP monitoring. For 1-hour 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 the impact monitoring, the ET Leader should 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.
2.7.2 The specific time to start and stop the 24-hour TSP monitoring should be clearly defined for each location and be strictly followed by the field operator.
2.7.3 In case of non-compliance with the air quality criteria, more frequent monitoring exercise, as specified in the Action Plan in Section 2.8, should be conducted within 24 hours after the result is obtained. This additional monitoring should 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 Leader should compare the impact monitoring results with air quality criteria set up for 24-hour TSP and 1-hour TSP. Table 2.1 shows the air quality criteria, namely Action and Limit levels to be used. Should non-compliance of the air quality criteria occurs, the ET Leader, ER, and Contractor should undertake relevant actions in accordance with the Action Plan as stated Table 2.2.
Table 2.1 Action and Limit Levels for Air Quality (Dust)
|
Parameters |
Action |
Limit |
|
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 2.2 Event/Action Plan for Air Quality (Dust)
|
EVENT |
ACTION |
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ET |
IEC |
ER |
CONTRACTOR |
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ACTION LEVEL |
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1. Exceedance for one sample
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2. Exceedance for two or more consecutive samples |
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LIMIT LEVEL |
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1. Exceedance for one sample
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2. Exceedance for two or more consecutive samples |
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ET : Environmental Team
IEC : Independent Environmental Checker
ER : Engineer or Engineer's Representative
2.9.1 The EIA Report has recommended dust control mitigation measures to minimise the impacts. The Contractor should be responsible for the design and implementation of these measures. If the recommended mitigation measures are not sufficient to restore the air quality to acceptable levels upon the advice of ET, the Contractor should liaise with the ET on some other mitigation measures, propose to ER for approval, and implement the mitigation measures.
2.9.2 The construction contractors are required to adopt dust reduction measures when carrying out construction works. In particular, the mitigation measures listed below should be adopted where applicable and area detailed in the following:
Construction Phase Measures
2.9.3 In order to ensure that dust emission is minimised during the construction phase of the road works, relevant dust control requirements set out in Parts I, III and IV of Schedule 1 of the Air Pollution Control (Construction Dust) Regulation should be met. The site agent is required to adopt dust reduction measures while carrying out construction works. In particular, dust suppression by twice daily watering with complete coverage of all active construction areas should be undertaken. The construction vehicle travel speed on unpaved site areas should also be limited to not more than 10km per hour. Besides, the mitigation measures listed below should be adopted where applicable. With the implementation of effective dust control measures, adverse dust impacts from the construction works of the project is not expected.
2.9.4 If the above measures are not sufficient to restore the air quality to acceptable levels upon the advise of ET Leader, the Contractor should liaise with the ET Leader on some other mitigation measures, propose to ER for approval, and implement the mitigation measures.
Site clearance and demolition of existing structures
2.9.5 The working area for the uprooting of trees, shrubs, or vegetation or for the removal of boulders, poles, pillars or temporary or permanent structures should be sprayed with water or a dust suppression chemical immediately before, during and immediately after the operation so as to maintain the entire surface wet.
2.9.6 All demolished items (including trees, shrubs, vegetation, boulders, poles, pillars, structures, debris, rubbish and other items arising from site clearance) that may dislodge dust particles should be covered entirely by impervious sheeting or placed in an area sheltered on the top and the 3 sides within a day of demolition.
Site boundary and entrance
2.9.7 Vehicle washing facilities including a high-pressure water jet should be provided at every discernible or designated vehicle exit point.
2.9.8 The area where vehicle washing takes place and the section of the road between the washing facilities and the exit point should be paved with concrete, bituminous materials or hardcores.
2.9.9 Where a site boundary adjoins a road, street, service and or other area accessible to the public, hoarding of not less than 2.4m from ground level should be provided along the entire length of that portion of the site boundary except for a site entrance or exit.
Access road
2.9.10 Every main haul road (i.e. any course inside a construction site having a vehicle passing rate of higher than 4 in any 30 minutes) should be paved with concrete, bituminous materials, hardcores or metal plates, and kept clear of dusty materials; or sprayed with water or a dust suppression chemical so as to maintain the entire road surface wet.
2.9.11 The portion of any road leading only to a construction site that is within 30m of a discernible or designated vehicle entrance or exit should be kept clear of dusty materials.
Use of vehicle
2.9.12 Immediately before leaving a construction site, every vehicle should be washed to remove any dusty materials from its body and wheels.
2.9.13 Where a vehicle leaving a construction site is carrying a load of dusty materials, the load should be covered entirely by clean impervious sheeting to ensure that the dusty materials do not leak from the vehicle.
Concrete production
2.9.14 The concrete batching plant should be located away from any air sensitive receiver as far as practicable.
2.9.15 If the total silo capacity of the concrete batching plant exceed 50 tonnes, the project proponent is required to obtain a Specified Process licence to ensure that any potential dust emission would be properly controlled.
2.9.16 Cement 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 such that, in the event of the silo approaching an overfilling condition, an audible alarm is triggered and the material filling stops within one minute.
2.9.17 Silo used for the storage of cement should not be overfilled.
2.9.18 The loading, unloading, transfer, handling or storage of any cement 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 or equipment.
2.9.19 Cement collected by fabric filters or other pollution control system or equipment should be disposed of in a totally enclosed containers.
Excavation and earth moving
2.9.20 The working area of any excavation or earth moving operation should be sprayed with water or a dusty suppression chemical immediately before, during and immediately after the operation so as to maintain the entire surface wet.
2.9.21 Exposed earth should be properly treated by compaction, turfing, hydroseeding, vegetation planting or sealing with latex, vinyl, bitumen, shotcrete or other suitable surface stabilizer within 6 months after the last construction activity on the construction site or part of the construction site where the exposed earth lies.
Stockpiling of dusty materials
2.9.22 Any stockpile of dusty material should be either covered entirely by impervious sheeting; placed in an area sheltered on the top and the 3 sides; or sprayed with water or a dust suppression chemical so as to maintain the entire surface wet.
Site cleanliness and tidiness
2.9.23 The requirements stipulated in the Works Bureau Technical Circular No. 6/2002 "Enhanced Specification for Site Cleanliness and Tidiness" should be followed to enhance cleanliness and tidiness on construction sites.