2.         AIR QUALITY

Monitoring Requirements

 

2.1              Measurement of 1-hour and 24-hours TSP were conducted to monitor the air quality.  Appendix A shows the established Action/Limit Levels for the captioned environmental monitoring works.

Monitoring Locations

 

2.2              Three designated monitoring stations, A2, A3 and A4 were selected for impact dust monitoring.  Table 2.1 describes the air quality monitoring locations, which are also depicted in Figures 2a and 2b.

 

Table 2.1     Locations for Air Quality Monitoring

 

Monitoring Stations

Description

A2

Lau Pak Lok Secondary School

A3

Shatin Heights

A4

Slope no. 07SW-D/FR4 beside Garden Villa

 

Monitoring Equipments

 

2.3              Table 2.2 summarizes the equipments used in the impact air monitoring programme.  Copies of calibration certificates are attached in Appendix B.

 

Table 2.2     Air Quality Monitoring Equipment

 

Equipments

Models and Makes

Quantity

Calibrator

G25A; S/N: 1536

1

1-hour TSP Dust Meter

Laser Dust Monitor – Model LD3

3

HVS Sampler

GMWS 2310 c/w of TSP sampling inlet

3

 

Monitoring Parameters, Frequency and Duration

 

2.4              Table 2.3 summarizes the monitoring parameters and frequencies of impact dust monitoring for the whole construction period.  The air quality monitoring schedule for the reporting month is shown in Appendix C.

Table 2.3 Impact Dust Monitoring Parameters, Frequency and Duration

 

Parameters

Frequency

1-hour TSP

Three times / 6 days

24-hour TSP

Once / 6 days

 

Monitoring Methodology and QA/QC Procedure

 

1-hour TSP Monitoring

 

Measuring Procedures

 

2.5              The measuring procedures of the 1-hour dust meters were in accordance with the Manufacturer’s Instruction Manual as follow:

 

·          Pull up the air sampling inlet cover

·          Change the Mode 0 to BG with once

·          Push Start/Stop switch once

·          Turn the knob to SENSI.ADJ and press it

·          Push Start/Stop switch once

·          Return the knob to the position MEASURE slowly

·          Push the timer set switch to set measuring time

·          Remove the cap and make a measurement

 

Maintenance/Calibration

 

2.6              The following maintenance/calibration was required for the direct dust meters:

 

·          Check the meter at 3-month intervals and calibrate the meter at 1-year intervals throughout all stages of the air quality monitoring.

 

24-hour TSP Monitoring

       

Instrumentation

 

2.7              High volume (HVS) samplers (Model GMWS-2310 Accu-Vol) completed with appropriate sampling inlets were employed for 24-hour TSP monitoring.  The sampler was composed of a motor, a filter holder, a flow controller and a sampling inlet and its performance specification complied with that required by USEPA Standard Title 40, Code of Federation Regulations Chapter 1 (Part 50).  Moreover, the HVS also met all the requirements in section 2.3 of the EM&A Manuals.

 

Operating/Analytical Procedures

 

2.8              Operating/analytical procedures for the operation of HVS were as follows:

 

·          A horizontal platform was provided with appropriate support to secure the samplers against gusty wind.

·          No two samplers were placed less than 2 meters apart.

·          The distance between the sampler and an obstacle, such as buildings, was at least twice the height that the obstacle protrudes above the sampler.

·          A minimum of 2 meters of separation from walls, parapets and penthouses was required for rooftop samples.

·          A minimum of 2 meters separation from any supporting structure, measured horizontally was required.

·          No furnaces or incineration flues were nearby.

·          Airflow around the sampler was unrestricted.

·          The sampler was more than 20 meters from the drip line.

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

 

2.9              Prior to the commencement of the dust sampling, the flow rate of the high volume sampler was properly set (between 1.1 m3/min. and 1.4 m3/min.) in accordance with the manufacturer's instruction to within the range recommended in USEPA Standard Title 40, CFR Part 50.

 

2.10          For TSP sampling, fiberglass filters (G810) were used [Note: these filters have a collection efficiency of > 99% for particles of 0.3 mm diameter].

 

2.11          The power supply was checked to ensure the sampler worked properly.

 

2.12          On sampling, the sampler was operated for 5 minutes to establish thermal equilibrium before placing any filter media at the designated air monitoring station.

 

2.13          The filter holding frame was then removed by loosening the four nuts and carefully a weighted and conditioned filter was centered with the stamped number upwards, on a supporting screen.

 

2.14          The filter was aligned on the screen so that the gasket formed an airtight seal on the outer edges of the filter.  Then the filter holding frame was tightened to the filter holder with swing bolts.  The applied pressure should be sufficient to avoid air leakage at the edges.

 

2.15          The shelter lid was closed and secured with the aluminum strip.

 

2.16          The timer was then programmed.  Information was recorded on the record sheet, which included the starting time, the weather condition and the filter number (the initial weight of the filter paper can be found out by using the filter number).

 

2.17          After sampling, the filter was removed and sent to the laboratory for weighing.  The elapsed time was also recorded.

2.18          Before weighing, all filters were equilibrated in a conditioning environment for 24 hours. The conditioning environment temperature should be between 25°C and 30°C and not vary by more than ±3°C; the relative humidity (RH) should be < 50% and not vary by more than ±5%.  A convenient working RH is 40%.

 

Maintenance/Calibration

 

2.19          The following maintenance/calibration was required for the HVS:

 

·          The high volume motors and their accessories were properly maintained. Appropriate maintenance such as routine motor brushes replacement and electrical wiring checking were made to ensure that the equipment and necessary power supply are in good working condition.

·          High volume samplers were calibrated at bi-monthly intervals using GMW-25 Calibration Kit throughout all stages of the air quality monitoring.

Results and Observations

 

2.20          All 24-hour TSP monitoring was conducted as scheduled during the reporting month except the monitoring at station A3 was cancelled on 12 September 2006 due to power failure.

 

2.21          All 1-hour TSP monitoring was conducted as scheduled during the reporting month except the monitoring at stations A2 and A3 was cancelled on 7 and 13 September 2006 due to adverse weather.

 

2.22          No Action/Limit Level exceedance for both 1-hours TSP and 24-hours TSP monitoring was recorded during the reporting month.

 

2.23          The monitoring data and graphical presentations of 1-hour and 24-hour TSP monitoring results are shown in Appendices D and E, respectively.

 

2.24          Wind data monitoring equipment has been installed in monitoring Station A3 for logging wind speed and wind direction.  Wind data for the reporting month is summarized in Appendix F.