10 AIR QUALITY ASSESSMENT
10.1 INTRODUCTION
This Section presents an assessment of the potential air quality impacts arising from the construction of the twin gas pipelines and the Gas Receiver Station (GRS) in the Tai Po gas production plant. As the majority of the length of the pipelines is to be constructed in the marine environment, dust emissions are expected to be small during the construction phase and limited to the onshore route within the Tai Po Industrial Estate/Tai Po Waterfront Park. The dust impacts from installation of the pipelines within this area are evaluated below.
During operation the Gas Receiver Station (GRS) will utilise heat from steam/hot water generated within the Tai Po gas production plant to warm up the incoming natural gas for pressure reduction if necessary. The heating system will be designed with the objective that the allowable location, quantity and quality of emissions of the existing production plant does not change. As a consequence of this, it is not necessary to examine operational air quality impacts.
The Study Area for air quality assessment is 500m from the worksite boundary for the land base works as defined by the EIA Study Brief. Potential air quality impact within 500m from the marine works was also taken into account for this assessment. Air Sensitive Receivers (ASRs) have been identified and the potential air quality impact on these receivers has been evaluated. Appropriate mitigation measures have been recommended, where necessary, to ensure that the relevant criterion is met.
10.2 LEGISLATIVE REQUIREMENTS AND EVALUATION CRITERIA
The principal legislation for the management of air quality in Hong Kong is the Air Pollution Control Ordinance (APCO) (Cap 311). The APCO lists a set of Air Quality Objectives, (AQOs) for seven air pollutants, stipulating statutory limits and permissible exceedances, as detailed in Error! Reference source not found..
A maximum hourly level of TSP of 500 (gm-3 at ASRs is also stipulated in the Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM) to control potential construction dust impacts.
The measures stipulated in the Air Pollution Control (Construction Dust) Regulation should be followed to ensure that any dust impacts are minimised.
Table 10.1 Hong Kong Air Quality
Objectives (mgm-3)(a)
|
Air Pollutant |
Averaging Time |
|||
|
|
1 Hour (b) |
24 Hour (c) |
3 Months (d) |
1 Year (d) |
|
Total Suspended Particulates
(TSP) |
- |
260 |
- |
80 |
|
Respirable Suspended
Particulates (RSP) (e) |
- |
180 |
- |
55 |
|
Sulphur Dioxide (SO2) |
800 |
350 |
- |
80 |
|
Nitrogen Dioxide (NO2) |
300 |
150 |
- |
80 |
|
Carbon Monoxide (CO) |
30,000 |
- |
- |
- |
|
Photochemical Oxidants (as ozone
(O3)) (f) |
240 |
- |
- |
- |
|
Lead (Pb) |
- |
- |
1.5 |
- |
|
Notes: (a)
Measured at 298K (25°C) and 101.325 kPa (one atmosphere) (b)
Not to be exceeded more
than three times per year (c)
Not to be exceeded more
than once per year (d)
Arithmetic means (e)
Suspended airborne
particulates with a nominal aerodynamic diameter of 10 micrometres or smaller. (f)
Photochemical oxidants are
determined by measurement of ozone only. |
||||
10.3 BASELINE CONDITIONS AND AIR QUALITY SENSITIVE
RECEIVERS
10.3.1 Baseline Conditions
The existing air quality within the vicinity of the Assessment Area (Figure 1.1a) is typical of the North East New Territories and is generally unaffected by local emissions from vehicles. The nearest EPD air quality monitoring station (AQMS) is located in Tai Po. The annual average air quality data monitored at this station for the year 2000 are presented in Error! Reference source not found..
Table 10.2 Background Air Quality in
2000
|
Air Pollutant |
Annual Average Concentration in mgm-3 (a) |
|
Total Suspended Particulates
(TSP) |
63 |
|
Respirable Suspended
Particulates (RSP) |
48 |
|
Sulphur Dioxide (SO2) |
12 |
|
Nitrogen Dioxide (NO2) |
47 |
|
Notes: (a)
Concentration monitored at
Tai Po AQMS in 2000 (Ref. Air Quality in Hong Kong 2000, EPD) |
|
The annual average concentrations presented in Error! Reference source not found. have been used as the background air quality data for the following assessment.
10.3.2 Sensitive Receivers
ASRs have been identified in accordance with the criteria set out in Annex 12 of the EIAO-TM by means of site inspections and reviews of land use plans.
Domestic premises, hotels, hostels, hospitals, clinics, nurseries, temporary housing accommodation, schools, educational institutions, offices, factories, shops, shopping centres, places of public worship, libraries, courts of law, sport stadiums and performing arts centres are considered as ASRs. ASRs within 500m of the pipeline alignment and their horizontal distances from the pipelines alignment are summarised in Table 10.3. The locations of ASRs are shown in Figure 10.3a.
Table 10.3 Air Sensitive Receivers
|
ASRs |
Location |
Type |
Distance from
Nearest Worksite Boundary (m) |
|
A1 |
Tai Po Industrial Estate |
Industrial |
10 |
|
A2 |
Tai Po Shuen Wan Temporary Golf
Driving Range |
Sport Ground |
330 |
|
A3 |
Village House at Pak Sha Tau |
Residential |
320 |
10.4 AIR QUALITY IMPACT ASSESSMENT
Construction Phase
The likely air quality impacts arising from the construction of the gas pipelines and the GRS are related to dust nuisance and gaseous emissions from construction plant, vehicles and barges.
It is expected that the following equipment will be involved in submarine pipeline installation:
* 1 laybarge (approximately 100m to 130m long);
* 1 anchor handling tug;
* 3 line pipe supply flat top barges;
* 1 safety vessel; and
* 1 dredger/1 jetter.
The pipelaying activities such as jetting and trench dredging are not dust generating and the gaseous emissions of NO2 and SO2 from the small number of barges required on site will be limited. Exceedance of AQOs from their operation is not anticipated.
The construction of the onshore pipelines section and the GRS is likely to involve dust generating activities such as site clearance, minimal ground excavation, material handling and vehicle movements on haul roads. The works will be conducted adjacent to and within the Tai Po Industrial Estate/Tai Po Waterfront Park. As the number of plant required on site will be limited, dust impact and NO2 and SO2 emissions from the machines and site vehicles will be minor. With the implementation of appropriate dust suppression measures in accordance with the Air Pollution Control (Construction Dust) Regulation, together with proper maintenance of equipment, adverse air quality impacts are not expected.
Operational Phase
There will be no emission of pollutants in Hong Kong during the operation of the pipelines and the GRS. The GRS will utilise heat from steam/hot water generated within the Tai Po gas production plant to warm up the natural gas for pressure reduction if required. The heating system will be designed to integrate with the existing production plant so that the allowable location, quantity and quality of emissions would not change. Small pockets of gas in the pipelines may be vented should maintenance and inspection be required at the GRS, however, as the venting will be carefully controlled and infrequent, air quality impacts are not expected to be a concern. In addition, flaring will only occur during emergency situation or maintenance at the launching station in Shenzhen. Therefore, air quality impacts from the operation of the pipelines and the GRS in Tai Po are not expected.
10.5 MITIGATION OF ADVERSE AIR QUALITY IMPACTS
Dust suppression measures in accordance with the Air Pollution Control (Construction Dust) Regulation should be implemented and incorporated into the Contract Specification to minimise potential dust nuisance arising from the works.
10.6 RESIDUAL ENVIRONMENTAL IMPACTS
There are no residual air quality impacts associated with the construction and operation of the project.
10.7 ENVIRONMENTAL MONITORING AND AUDIT
Adverse air quality impacts during construction and operation of the project are not expected, therefore, environmental monitoring and audit of air quality is not required.
10.8 CONCLUSIONS
Potential air quality impacts arising from the construction and operation of the gas pipelines and the Gas Receiver Station have been evaluated. As the number of barges required for the pipelaying operation will be limited, emissions of gaseous pollutants from these barges are not expected to exceed the AQOs.
Air quality impacts associated with dust generation and gaseous emissions from on site plant and vehicles during the construction of the onshore pipelines section and the Gas Receiver Station in Tai Po will be small. With the implementation of dust suppression measures in accordance with the Air Pollution Control (Construction Dust) Regulation, an adverse dust impact is not anticipated.
During operation, the GRS will utilise heat from steam/hot water generated within the existing Tai Po gas production plant and no flare will be required at the GRS. As such, air quality impacts from the operation of the pipelines and GRS at Tai Po are not expected.