In this section, the requirements, methodology, equipment, monitoring locations, criteria and protocols for the monitoring and audit of air quality impacts during the construction of the Designated and Potentially Designated Projects are described below. The specific air quality EM&A requirements for each of the works packages are defined in Annexes A and B.
5.2.1 Introduction
The objectives of the air quality monitoring for Total Suspended Particulates (TSP) shall be:
· to identify the extent of construction dust impacts on sensitive receivers;
· to determine the effectiveness of mitigation measures to control dust from construction activities;
· auditing 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; and
· to comply with Action and Limit (AL) Levels for air quality as defined in this Manual.
5.2.2 Methodology and Criteria
Monitoring and audit of the Total Suspended Particulates (TSP) levels shall be carried out by the ET to ensure that any deterioration in air quality can be readily detected and timely actions taken to rectify the situation.
The criteria against which air quality (measured as TSP) monitoring shall be assessed are:
· The Hong Kong Air Quality Objectives (AQOs) for TSP, 24-hour TSP levels of 260 mg m-3; and
· The statutory 1-hour TSP limit of 500 mg m-3.
These levels are not to be exceeded at Air Sensitive Receivers (ASRs).
The 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 high volume sampling 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.
24-hour average TSP concentrations should be measured by drawing air 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. The analysis process normally takes about two days to complete.
1-hour average TSP concentrations can be measured preferably by using the same monitoring method as 24-hour average TSP or, with prior agreement from the Engineer, a real-time airborne particulate measurement can be undertaken using a direct reading meter such as the MIE Data-Ram Portable Real Time Aerosol Monitor (MIE). 1-hour average TSP concentrations measured by a hand held real-time aerosol monitor require no laboratory analysis and will give an instant reading of the dust levels. Air samples are drawn through the optically-sensitive area of the monitor for a continuous period of 1-hour and the monitor will calculate the time-average dust levels.
Despite the advantages of using a real time monitor to measure particulate concentrations such as in response to dust complaints, results are not comparable with 24-hour HVS data. Therefore, whichever method is to be used for 1-hour TSP monitoring, both baseline and ad hoc measurements must be carried out by the same method, upon approval from the Engineer.
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 Annex D (Record Sheet 1.1).
A high volume sampler (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 min-1 (20-60 SCFM) 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; and
· capable of operating continuously for 24-hr period.
The ET Leader shall be responsible for the provision of the monitoring equipment. He shall ensure that sufficient number of HVSs with an appropriate calibration kit are 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.
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 will be carried out every two months. Five point calibration will be carried out every six months.
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 a Annex D(Record Sheet 1.1).
Alternately, if the ET Leader proposes to use a direct reading dust meter to measure 1-hour TSP, sampling in the range of 0.1‑100 mg m-3, he shall submit sufficient information to the Engineer to prove that the instrument is capable of achieving a comparable result as that the HVS and may be used for the 1-hour sampling. The instrument shall 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 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 location of the equipment shall be determined by the ET Leader and agreed with the Engineer. For installation and operation of the wind data monitoring equipment, the following points shall be observed:
· the wind sensors should be installed on masts at an elevated level 10 metres above the ground, so that they are clear of obstructions or turbulence caused by building(s);
· the wind data should be captured by a data logger and to be downloaded for processing at least once a month;
· the wind data monitoring equipment should be re-calibrated at least once every six months; and
· wind direction should be divided into 16 sectors of 22.5 degrees.
In exceptional situations, the ET Leader may propose alternative methods to obtain representative wind data upon approval from the Engineer and agreed with EPD. The recommended types and quantities of TSP monitoring equipment required for each designated and potentially designated project are defined in Annex A and B.
5.2.4 Laboratory Measurement/Analysis
A clean laboratory with constant temperature and humidity control, and equipped with the necessary measuring and conditioning instruments to handle the dust samples, shall be available for sample analysis and equipment calibration and maintenance. The laboratory shall be either HOKLAS accredited or another internationally accredited laboratory.
If a site laboratory or a non-HOKLAS accredited laboratory is used, the laboratory equipment and measurements shall meet with the satisfaction of the Engineer in consultation with the IEC. The IEC shall conduct regular audits to determine the accuracy of the measurement results. The ET Leader shall provide the Engineer with one copy of the Title 40 of the Code of Federal Regulations, Chapter 1 (Part 50), Appendix B for reference.
The air quality monitoring locations for each of the Designated Projects are outlined in Annexe’s A and B, and the figures showing the location of the environmental sensitive receivers are included in Annex C.
Baseline monitoring shall be carried out at all designated monitoring stations, to be approved by the Engineer and IEC, to determine the ambient 24‑hour TSP and 1‑hour levels at the monitoring locations prior to the commencement of the construction works. During the baseline monitoring, there shall not be any construction or dust generating activities in the vicinity of the monitoring stations. Before commencing the baseline monitoring, the ET Leader 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.
Baseline monitoring shall be carried out 1 month before the commencement of the construction works. The monitoring should be conducted for a continuous period of at least two weeks (14 days) under typical weather conditions with the 24-hour and three 1-hour ambient measurements taken daily at each monitoring location. As noted above, monitoring results of HVS and direct reading methods are not directly comparable and the same instrument must therefore be used for both baseline and impact monitoring in the case of 1-hour TSP. 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.
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.
Baseline checking of ambient dust levels shall be carried out every six months at each monitoring location, when no dusty works activities are in operation. 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 Engineer, IEC and EPD.
24-hour TSP concentrations should be measured by the High Volume Method for Total Suspended Particulates, Part 50 Chapter 1 Appendix B, Title 40 of the Code of Federal Regulations of the USEPA. It is considered that this form of impact monitoring should be undertaken at the proposed monitoring locations once every 6 days.
Due to the lengthy delay between sampling time and result availability for 24-hour sampling, 1-hour TSP sampling should also be conducted in response to any complaints about construction dust. 1-hour TSP levels, while assessed under different criteria, are considered to be indicative of the 24-hour results conducted on the same day. In this way expedient remedial actions, should they be required, may be undertaken based on the 1-hour data, before the 24-hour results become available.
1-hour sampling, providing real time airborne particulate measurement, can be undertaken using a direct reading dust meter. Despite the advantages of using a real time monitor to measure particulate concentrations such as in response to dust complaints, results are not comparable with 24-hour HVS data. Therefore, if the use of a direct reading monitor is agreed for 1-hour TSP sampling both baseline and impact monitoring must be carried out by the direct reading method.
Specific dust control measures and the monitoring during construction phase should be included as part of the works contracts. Regular compliance checking by the Environmental Checker and the Engineer at site and as well as at the Sensitive Receivers should be conducted.
Action and Limit (A/L) levels provide an appropriate framework for the interpretation of monitoring results. The air quality monitoring data shall be checked against the agreed A/L levels as listed in Tables 5.2a and 5.2b.
Table 5.2a Derivation of Action and Limit Levels for 24-Hour TSP Monitoring
|
Level |
Total
Suspended Particulates (mg m-3) |
|
Baseline |
Numerical
average of physical measurements prior to construction commencement |
|
Action |
For baseline £200 mg m-3, Action
Level = (Baseline Level x 1.3 + Limit Level)/2 For baseline >200 mg m-3, Action Level
= Limit Level |
|
Limit |
AQO for 24-hour
TSP: 260 mg m-3 |
Table 5.2b Derivation of Action and Limit Levels for 1-Hour TSP Monitoring
|
Level |
Total
Suspended Particulates (mg m-3) |
|
Baseline |
Numerical average
of physical measurements prior to construction commencement |
|
Action |
For baseline £384 mg m-3, Action
Level = (Baseline Level x 1.3 + Limit Level)/2 For baseline > 384 mg m-3,
Action Level = Limit Level |
|
Limit |
EIAO Statutory
Limit: 500 mg m-3 |
The principle upon which the Event and Action Plan (EAP) is based is
the prescription of procedures and actions associated with the measurement of certain
defined levels of air pollution recorded by the environmental monitoring
process and defined in the tables above.
The ET Leader shall compare the impact monitoring results with the air
quality criteria (Tables 5.2a and 5.2b) set up for 24-hour TSP and 1-hour
TSP. In cases where exceedance of
these criteria occurs, the ET Leader, the Engineer and Contractor shall
strictly observe the relevant actions of the EAP shown in Table 5.2c below.
Table 5.2c Event and Action Plan for Construction Phase Air Quality
|
EVENT |
|
ACTION |
|
|
|
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|
|
ET Leader |
IEC |
Engineer |
Contractor |
|
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|
Action Level |
|
|
|
|
|
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|
Exceedance for
one sample |
1. Identify source (s)
of exceedance and inform IEC, Contractor and Engineer 2. Repeat dust
measurements to confirm findings 3. Increase
monitoring frequency to daily 4. Assess efficacy
of remedial measures and keep the Contractor, IEC, and Engineer informed |
1. Check monitoring
data submitted by ET 2. Check monitoring
data trends and Contractors working methods 3. Check and
confirm Contractors proposed remedial actions and working methods are
appropriate |
1. Confirm receipt
of notification of exceedance in writing 2. Remind the
Contractor of his contractual obligations and review the Contractor’s working
methods 3. Discuss remedial
actions with the Contractor and IEC 4. Inform
complainant of actions taken, if necessary |
1. Rectify any
unacceptable practice 2. Liaise with Engineer
and IEC to develop appropriate remedial measures to reduce dust impact 3. Amend working
methods and remedial proposals if required by the Engineer or IEC 4. Implement the
agreed remedial actions upon instruction from the Engineer and IEC |
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|
Exceedance for
two or more consecutive samples |
1. Identify source
(s) of exceedance and inform IEC, Contractor and Engineer 2. Repeat
measurements to confirm findings 3. Increase the monitoring
frequency to daily to assess the efficacy of remedial measures and keep the
Contractor informed 4. Discuss remedial
actions with IEC and Contractor 5. If exceedance
continues, arrange meeting with Engineer, IEC and Contractor to review
working practices and identify further remedial actions 6. If exceedance
stops, inform the Contractor and cease additional monitoring. |
1. Check monitoring
data submitted by ET 2. Check monitoring
data trends and Contractors working methods 3. Discuss with Contractor
and Engineer on possible remedial measures 4. Check and
confirm Contractors proposed remedial measures are appropriate 5. Determine the
efficacy of remedial actions and keep the Engineer informed |
1. Confirm receipt
of notification of exceedance in writing 2. Remind the
Contractor of his contractual obligations and review the Contractor’s working
methods 3. Discuss remedial
actions with the Contractor and IEC 4. Ensure remedial
measures are properly implemented 5. Inform
complainant of actions taken, if necessary. |
1. Rectify any
unacceptable practice, if possible 2. Submit proposals
for remedial actions to Engineer and IEC within three working days of
notification 3. Discuss and
amend remedial actions, if required, by the Engineer and IEC 4. Implement the remedial
action (s) immediately upon instruction from the Engineer Discuss with
Engineer and IEC, to optimise the effectiveness of the agreed remedial
actions |
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|
Limit Level |
|
|
|
|
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|
Exceedance for
one sample |
1. Identify source
(s) of exceedance and inform IEC, Contractor and Engineer 2. Repeat dust
measurements to confirm findings 3. Increase
monitoring frequency to daily 4. Assess efficacy
of remedial measures and keep the Contractor, IEC, Engineer and EPD informed |
1. Check monitoring
data submitted by ET 2. Check monitoring
data trends and Contractors working methods 3. Check and
confirm Contractors proposed remedial actions and working methods are
appropriate 4. Check and confirm
Contractors proposed remedial measures are appropriate 5. Determine the
efficacy of remedial actions and keep the Engineer informed |
1. Confirm receipt
of notification of exceedance in writing 2. Remind the
Contractor of his contractual obligations and review the Contractor’s working
methods 3. Discuss remedial
actions with the Contractor and IEC, 4. Ensure remedial
measures are properly implemented 5. Inform
complainant of actions taken, if necessary. |
1. Take immediate
action to avoid further exceedance 2. Submit proposals
for remedial actions to Engineer and IEC within three working days of
notification 3. Discuss and
amend remedial actions, if required, by the Engineer and IEC 4. Implement the
remedial action (s) immediately upon instruction from the Engineer 5. Discuss with
Engineer and IEC, to optimise the effectiveness of the agreed remedial
actions |
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|
|
|
|
|
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|
Exceedance for
two or more consecutive samples |
1. Identify source
(s) of exceedance and inform IEC, Contractor and Engineer 2. Repeat
measurements to confirm findings 3. Increase the
monitoring frequency to daily to assess the efficacy of remedial measures and
keep the Contractor informed 4. Discuss remedial
actions with IEC and Contractor 5. If exceedance
continues, arrange meeting with Engineer, IEC and Contractor to review
working practices and identify further remedial actions 6. If exceedance
stops, inform the Contractor and cease additional monitoring. |
1. Discuss with
Contractor and Engineer on possible remedial measures 2. Check and confirm
Contractors proposed remedial measures are appropriate 3. Determine the
efficacy of remedial actions and keep the Engineer informed |
1. Confirm receipt
of notification of exceedance in writing 2. Remind the
Contractor of his contractual obligations and review the Contractor’s working
methods 3. Discuss remedial
actions with the Contractor and IEC 4. Ensure remedial
measures are properly implemented 5. If exceedance
continues, instruct the Contractor to stop the relevant portion of work until
the exceedance is abated 6. Inform
complainant of actions taken, if necessary. |
1. Rectify any
unacceptable practice, if possible 2. Submit proposals
for remedial actions to Engineer and IEC within three working days of
notification 3. Discuss and amend
remedial actions, if required, by the Engineer and IEC 4. Implement the
remedial action (s) immediately upon instruction from the Engineer 5. Discuss with
Engineer and IEC, to optimise the effectiveness of the agreed remedial
actions |
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The EIA (DE) has recommended air quality control and mitigation measures during the construction phases of the Project. In the event of exceedances or complaints, the Contractor shall be responsible for reviewing the effectiveness of the following measures and for proposing, designing and implementing alternative measures as appropriate (a full list of measures are outlined in the Implementation Schedule detailed in Annex E:
· where a site boundary adjoins a road, street, service lane or other area accessible to the public, hoarding of not less than 2.4 m high from ground level should be provided along the boundaries of the seven pumping stations sites;
· the portion of any road leading only to a construction site that is within 30 m of a discernible or designated vehicle entrance or exit should be kept clear of dusty materials;
· any stockpile of dusty materials should be either covered entirely by impervious sheeting, placed in an area sheltered on the top and the 3 sides or sprayed with water so as to maintain the entire surface wet;
· all dusty materials should be sprayed with water immediately prior to any loading and unloading so as to maintain the dusty materials wet;
· every vehicle should be washed to remove any dusty materials from its body and wheels immediately before leaving a construction site;
· 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;
· water should be continuously sprayed on the surface where any mechanical breaking operation that causes dust emission is carried out, unless the process is accompanied by the operation of an effective dust extraction and filtering device;
· the working area of excavation should be sprayed with water immediately before, during and immediately after the operation so as to maintain the entire surface wet;
· where a scaffolding is erected around the perimeter of a building under construction, effective dust screens, sheeting or netting should be provided to enclose the scaffolding from the ground floor level of the SPS; and
· any skip hoist for material transport should be totally enclosed by the impervious sheeting.
With the implementation of appropriate mitigation measures in the pumping station design, as outlined below, the Project is not predicted to generate any adverse air quality impacts to the receivers. Operational EM&A is therefore not required.
· the main odour sources, such as wet well and screening house, should be enclosed;
· an odour removal system, such as activated carbon filters should be installed to reduce the odour emissions;
· proper design of the discharge point of the odour removal system should be adopted to direct emissions away from the adjacent sensitive uses;
· the transportation of screenings during maintenance should be managed so as to prevent odour impact; and
· effective and regular maintenance of the odour removal system should be performed to maintain a removal efficiency of about 90%.