This section assesses the potential air quality impacts associated with the construction and operation of West Kowloon Reclamation Remaining Roadworks Stage 4 Link Roads G & L. Dust generation during the construction phase, and vehicle emissions from Link Roads G & L during the operational phase are the major sources of the air pollution. The representative Air Sensitive Receivers (ASR's) within 500m of the study area have been identified and worst case impacts on these receivers have been modelled. The findings are presented in this Section. Suitable mitigation measures, where necessary, are recommended to protect the ASRs and to ensure that the legislative criteria and guidelines will be satisfied.
3.2.1 Environmental Impact Assessment Ordinance
The criteria for evaluating air quality impacts are laid out in Annexes 4 and 12 of the Technical Memorandum on Environmental Impact Assessment (TMEIA). The relevant criteria are given below.
The principal legislation for the management of air quality is the Air Pollution Control Ordinance (APCO) (Cap 311). The whole of the Hong Kong Special Administrative Region (HKSAR) is covered by the Hong Kong Air Quality Objectives (AQOs) which stipulate the statutory limits of some typical air pollutants and the maximum allowable numbers of exceedance over specific periods. The AQOs are shown in Table 3.1below.
Table 3.1 Hong Kong Air Quality Objectives (µg m-3) (i)
|
Pollutant |
Average Time |
|||
|
|
1 Hour (ii) |
8 Hour (iii) |
24 Hour (iii) |
1 Year (iv) |
|
Total Suspended Particulates (TSP) |
- |
- |
260 |
80 |
|
Respirable Suspended Particulates (RSP)(v) |
- |
- |
180 |
55 |
|
Nitrogen Dioxide (NO2) |
300 |
- |
150 |
80 |
|
Carbon Monoxide(CO) |
30,000 |
10,000 |
- |
- |
|
Photochemical Oxidants (as Ozone, O3)(vi) |
240 |
- |
- |
- |
|
Note: i. Measured at 298K (250C) and 101.325 kPa (one atmosphere). ii. Not to be exceeded more than three time per year. iii. Not to be exceeded more than once per year. iv. Arithmetic means. v. Respirable Suspended Particulates means suspended particles in air with a nominal aerodynamic diameter of 10 micrometers and smaller. vi. Photochemical oxidants are determined by measurement of ozone only. |
||||
The TMEIA also states that the hourly Total Suspended Particulate (TSP) level should not exceed 500mgm-3 (measured at 25oC and one atmosphere) for construction dust impact assessment. Mitigation measures from construction sites have been specified in the Air Pollution Control (Construction Dust) Regulations.
The existing environment of the proposed Remaining Roadworks Stage 4 Link Roads G & L is primarily affected by the traffic on West Kowloon Expressway, Route 3, Lai Wan Interchange, Hing Wah Street West, Sham Mong Road and D3. No industrial uses have been identified within the study area. As such, the local traffic is considered to be the dominant source affecting the ambient air quality.
There is currently one fixed air quality monitoring station which is located in Sham Shui Po operated by Environmental Protection Department (EPD). The background concentration of pollutants reported for the year 1998 at this station is included in Table 3.2 below. Dust levels recorded at this station are high (86 mgm-3 for TSP) and exceed the annual AQO for TSP. The annual average concentration levels of 86 mgm-3, 55 mgm-3 and 67 mgm-3 have been used as background levels of TSP, RSP and NO2 in the subsequent assessments.
Table 3.2 Background Air Quality
|
Pollutants |
Concentration in (µgm-3) |
||
|
Average Time |
|||
|
1 Hour (max.) |
24 Hour (max.) |
Annual |
|
|
TSP RSP NO2 O3 SO2 |
- 302 252 183 207 |
208 146 157 70 78 |
86 55 67 18 18 |
|
Note: 1. Bold figure exceeds AQO criteria |
|||
3.4 Air Sensitive Receivers
Representative Air Sensitive Receivers (ASRs) within 500m of the project limit have been identified according to the criteria set out in the TMEIA and through site inspections and a review of land use plans. ASRs and their horizontal distance from the proposed Link Roads G & L have been identified and are summarized in Table 3.3. Locations of the ASRs are shown in Figures 3.1.
Table 3.3 Representative Air Sensitive Receivers
|
ASRs |
|
Location |
Usage |
Distance from the link roads (m) |
Relative Height from the link roads (m) |
|
ASR1 |
Site 10 (Planned) |
Block 3 |
Residential |
85 |
-1.9 |
|
ASR2 |
Block 4 |
Residential |
115 |
-3.1 |
|
|
ASR3 |
Block 5 |
Residential |
185 |
-3.1 |
|
|
ASR4 |
Block 6 |
Residential |
240 |
-3.1 |
|
|
ASR5 |
Block 7 |
Residential |
290 |
-3.1 |
|
|
ASR6 |
School |
Recreation |
200 |
-3.1 |
|
|
ASR7 |
Playground |
Recreation |
120 |
-1.3 |
|
|
ASR8 |
Mei Foo Sun Chuen |
Phase 3 Block 90 |
Residential |
260 |
-1.9 |
|
ASR9 |
Phase 8 Block 104 |
Residential |
185 |
-3.1 |
|
|
ASR10 |
Phase 8 Block 112 |
Residential |
130 |
-3.1 |
|
|
ASR11 |
Phase 8 Block 132 |
Residential |
180 |
-3.1 |
Table 3.3 Representative Air Sensitive Receivers (Cont’d)
|
ASRs |
|
Location |
Usage |
Distance from the link roads (m) |
Relative Height from the link roads (m) |
|
ASR12 |
|
Phase 8 Block 128 |
Residential |
210 |
-3.1 |
|
ASR13 |
|
Lai Chi Kok Park |
Residential |
125 |
-1.3 |
|
ASR14 |
KMB (Planned) |
Bus Depot Block 1 |
Residential |
90 |
-1.9 |
|
ASR15 |
Bus Depot Block 2 |
Residential |
140 |
-1.6 |
|
|
ASR16 |
Bus Depot Block 3 |
Institutional |
195 |
-1.4 |
3.5 Construction Phase
3.5.1 Potential Sources of Impact
It is anticipated that extensive earthworks will be required for the construction of Link Roads G & L. An estimated 40,000m3 of fill will be required for the embankment construction although little spoil will be generated within the work site.
Dust will be generated from excavation, filling, bulldozing, material handling and vehicular movements on unpaved work sites during earthworks construction. During roadwork construction, only a small volume of concrete will be required which will be imported to site in ready-mix form. This means that there will be no need for a concrete batching plant to be established on-site. Therefore, the major fugitive dust sources will be material handling, bulldozing, and truck movements on unpaved roads and roadwork construction.
The extent of impacts depend on the distances between the work sites and the identified ASRs, the construction methods employed and the number of plant used and vehicle movements. Construction works for Link Roads G & L will primarily be earthworks and roadwork construction. Since only a small number of items of construction equipment will be used, the overall exhaust emissions of SO2 and NO2 from the diesel-powered mechanical equipment of these plants are expected to be minimal.
3.5.2 Construction Dust Assessment Methodology
Dispersion Model
The extent of dust impacts arising from the construction of Link Roads G & L have been predicted using the USEPA approved model Fugitive Dust Model (FDM) in conjunction with the construction programme. Samples of FDM modelling input and output files illustrating the details are contained in Annex C. The Compilation of Air Pollutant Emission Factors, 5th Edition, US Environmental Protection Agency, 1996, (AP-42) was used to determine the various fugitive dust sources.
Meteorological Data Input
Sequential meteorological data for 1999 from Cheung Sha Wan and King’s Park weather station, operated by Hong Kong Observatory, were used as input to the model to obtain 1-hour and 24-hour average TSP concentration at the identified ASRs. Data obtained from Cheung Sha Wan and King’s Park stations used as input to the model includes, wind direction and speed together with atmospheric Pasquill stability class, and mixing heights together with air temperature.
Emission Factors
Emission factors, for various fugitive dust sources have been determined based on the USPEA Compilation of Air Pollution Emission Factors, 5th Edition (AP-42). Emission factor for typical construction operations given in the USPEA is 1.2 tons per acre of construction per month of activity (296.5 g/m2/month). The emission factors used for carrying out the modelling are summarised in Table 3.4. Dust emission factor of 3.2 x 10-4 g s-1m-2 was obtained by converting the above emission factor based on 26 working day per month and 10 operation hours per day.
The dust emission from road construction is associated with drilling, ground excavation, filling for embankment and vehicle movement on unpaved road. The density of the fill material is assumed to be 1800 kg m-3 which was used for the calculation of the emission factor for road construction.
Table 3.4 Emission Factors for Various Construction Activities
|
Activities |
Emission Factors |
Remarks |
|
Road Construction |
3.2 x 10-4 g s-1 m-2 |
· Based on USEPA AP-42 Vol. 1 5th Edition, Section 13.2.3 |
1-hour TSP Levels
It was assumed that construction would take place over ten hours per day. The corresponding meteorological data has thus been used as input to the FDM. The highest predicted TSP levels were obtained and compared with the recommended 1-hour limit of 500 mgm-3.
24-hour TSP Levels
As the time variation of dust emissions is not considered in the FDM, the daily TSP levels for daytime construction activities are therefore determined by simulating the model with the default option of an 8-hour averaging period. Meteorological data was used for the period 0900 – 1700 hours. The 24-hour TSP level was then estimated by multiplying the modelled results by a conversion factor (8 hours out of 24 hours = 1/3) to take account of the 8-hour construction period, i.e. one-third of the 8-hour TSP levels predicted from the model. The predicted 24-hour TSP levels from daytime activities and the background daily TSP level were added together and compared with the AQO of 260 mgm-3.
3.5.3 Evaluation of Impact
Construction dust impacts were modelled using the Fugitive Dust Model (FDM) with worst case assumptions as input data and at ground level. Since construction of Route 9 – Tsing Yi to Cheung Sha Wan will take place in parallel with this project, cumulative dust impacts have therefore been assessed. Predicted net and cumulative hourly and daily TSP levels at the identified ASRs are shown in Table 3.5 below. The background annual average TSP levels of 86 mgm-3 measured at Sham Shui Po monitoring station has been added to the predicted daily results to provide the cumulative impact.
Table 3.5 Predicted Hourly and Daily TSP Levels ( mgm-3) (1)
|
ASRs |
|
Location |
Net Dust Impacts |
Cumulative Dust Impacts |
|||
|
Maximum Hourly Average TSP Level |
Maximum Daily Average TSP Level |
Maximum Hourly Average TSP Level |
Maximum Daily Average TSP Level |
||||
|
ASR8 |
Mei Foo Sun Chuen |
Phase 3 Block 90 |
496 |
102 |
598 |
114 |
|
|
ASR9 |
Phase 8 Block 104 |
593 |
109 |
695 |
121 |
||
|
ASR10 |
Phase 8 Block 112 |
720 |
117 |
822 |
129 |
||
|
ASR11 |
Phase 8 Block 132 |
579 |
106 |
681 |
118 |
||
|
ASR12 |
Phase 8 Block 128 |
615 |
106 |
717 |
118 |
||
|
ASR13 |
|
Lai Chi Kok Park |
900 |
137 |
1002 |
149 |
|
|
|
|
Dust Criteria |
500 |
260 |
500 |
260 |
|
|
Notes: (1) Background TSP levels included in the results of daily average TSP (2) Bold figure exceeds dust criteria (3) ASRs 1-7 & 14-16 are planned receivers and no construction impacts expected |
|
||||||
The measured annual average TSP level at Sham Shui Po monitoring station is 86 mgm-3, indicating that the existing background dust level is high. From the results obtained the unmitigated construction activities are likely to contribute significantly to the cumulative dust impact at the identified ASRs. Construction is expected to be completed within 2 years.
As indicated in Table 3.5, all the predicted 24-hour TSP levels at the ASRs will comply with the AQO criteria of 260 mgm-3 during earthworks and roadwork construction. However, due to the close proximity of ASR 12, net impacts predicted at the Lai Chi Kok Park indicate maximum dust levels of 900 mgm-3 (hourly average), which would exceed the recommended hourly TSP guideline level of 500 mgm-3 by 80%. Also the predicted 1-hour TSP levels at Mei Foo Sun Chuen, ASRs 9, 10, 11 and 12 located ranges 130-210m from the worksite are 593 mgm-3, 720 mgm-3, 579 mgm-3 and 615 mgm-3 respectively which would exceed the dust criteria by (2%), (44%), (16%) and (23%). The predicted cumulative 1-hour TSP levels at all ASRs would exceed the dust criteria.
Dust suppression measures are therefore recommended to reduce emissions from the site to ensure the criteria would not be exceeded.
3.5.4 Recommended Mitigation Measures
At some ASRs along Link Roads G & L, in Mei Foo Sun Chuen and Lai Chi Kok Park, it is expected that dust levels would exceed the specified criteria and thus dust control measures are required to minimise the nuisance to acceptable levels. Dust control measures for construction activities associated with the earthworks for Link Roads G & L are outlined below.
Material Handling
· the height from which fill materials are dropped should be controlled to a minimum practical height to limit fugitive dust generation from unloading;
· any stockpiles of aggregate or spoil should be covered and water applied;
· water spray should be used during the handling of excavated and fill material where dust is likely to be created; and
· all dusty materials should be sprayed with water immediately prior to any loading, unloading or transfer operation so as to maintain moisture content of the dusty materials.
Vehicle Movements on Unpaved Haul Road
· every vehicle should be washed to remove any dusty materials from its body and wheels before leaving a construction site;
· the load on the vehicles should be covered entirely by clean impervious sheeting to ensure that the dusty materials do not leak from the vehicle; and
· the haul road should be located away from sensitive receivers with vehicle speed limited to 20 kph to reduce the traffic induced dust dispersion and re-suspension within the site.
Earthworks
· the amount of exposed soil should be kept in minimal by re-vegetation of completed earthworks.
Through the implementation of the above mitigation measures, dust levels can be reduced. Based on the AP42, the effectiveness of the mitigation measures has been evaluated. It is estimated that a 70% reduction in dust levels would be achieved for material handling, road construction and vehicle movements with the introduction of frequent surface watering by at least three times daily and compacting on active areas on the site. The predicted mitigated hourly and daily TSP levels at ground level are shown in Table 3.6.
Table 3.6 Mitigated Hourly and Daily TSP Levels ( mgm-3) (1)
|
ASRs |
|
Location
|
Net Dust Impacts |
Cumulative Dust Impacts |
|||
|
Maximum Hourly Average TSP Level |
Maximum Daily Average TSP Level |
Maximum Hourly Average TSP Level |
Maximum Daily Average TSP Level |
||||
|
ASR8 |
Mei Foo Sun Chuen |
Phase 3 Block 90 |
209 |
92 |
311 |
104 |
|
|
ASR9 |
Phase 8 Block 104 |
238 |
95 |
340 |
107 |
||
|
ASR10 |
Phase 8 Block 112 |
276 |
98 |
378 |
110 |
||
|
ASR11 |
Phase 8 Block 132 |
234 |
94 |
336 |
106 |
||
|
ASR12 |
Phase 8 Block 128 |
245 |
94 |
347 |
106 |
||
|
ASR13 |
|
Lai Chi Kok Park |
330 |
106 |
432 |
118 |
|
|
|
|
Dust Criteria |
500 |
260 |
500 |
260 |
|
|
Notes: (1) Background TSP levels included in the results of daily average TSP (2) Bold figure exceeds dust criteria (3) ASRs 1-7 & 14-16 are planned receivers and no construction impacts expected |
|
||||||
The predicted results show that with the inclusion of mitigation measures dust levels at all ASRs will comply with both the hourly and daily dust criteria.
3.5.5 Residual Impacts
No adverse residual impacts are predicted for the construction of Link Roads G & L.
3.5.6 EM&A Requirement
Full compliance with the dust criteria will be achieved at all ASRs with the implementation of mitigation measures. Dust monitoring is recommended to ensure that the dust levels do not exceed the criteria during the construction phase. EM&A requirements are discussed in Section 6 and the EM&A Manual.
3.5.7 Conclusions
The construction of Link Roads G & L will inevitably lead to dust generation. It is predicted that various construction activities associated with the establishment of the embankment would give rise to high hourly TSP levels. Mitigation measures are therefore necessary to suppress dust emissions from construction activities through good site practice. In order to ensure full compliance of the dust levels with the criteria, it is recommended that baseline dust monitoring and dust impact monitoring is carried out prior to and during the construction works.
3.6 Operational Phase
3.6.1 Potential Source of Impact
Vehicular exhaust emissions are the major air pollutant sources during the operation of Link Roads G & L. Both Nitrogen Dioxide (NO2) (1-hour) and Respirable Suspended Particulates (RSP) (24-hour) have been evaluated in accordance with the standard practice for assessing the vehicle traffic related air quality impacts.
3.6.2 Assessment Methodology
The USEPA approved air dispersion model, CALINE4 was used to predict the pollutant levels of NO2 and RSP from Link Roads G & L. In accordance with the requirements of the EIA Study Brief, all planned and existing roads, their associated slip roads, within a 500m radius of the Study Area have been considered in the model.
Peak AM hourly traffic flows within 15 years after the operation of Link Roads G & L (2003 & 2018) and the year for the commencement of the construction works (2001) have been predicted and details are contained within the Traffic Forecast (refer to Annex A) as prepared by MVA. The worst case hourly traffic flows are predicted to be during the AM peak hour in Year 2018.
Peak hour traffic will occur during the daytime and the worst case scenario of neutral meteorological conditions was assumed in the model run. Typical input parameters for the model are listed below:
Wind speed 1ms-1;
Wind direction worst case for each receivers;
Stability class D;
Mixing height 500 m;
Standard deviation of wind direction 24 degree;
Surface roughness 100 cm; and
Temperature 250C.
Fleet emission factors based on the EUROIII criteria have been adopted for this assessment. The most updated vehicle emission factors available from the EPD are for the Year 2011. The calculation of emission factors for all planned and existing roads including the slip roads are presented in Annex B. It is believed that more stringent controls will be put in place by the Government. For example the adoption of LPG taxis. Since the emission factors beyond 2011 are not available, 2011 fleet average emission factors for Oxides of Nitrogen (NOx) and Particulate Matter (PM) were therefore assumed for traffic beyond 2011. The predicted results are therefore believed to be an overestimate for the Year 2018.
3.6.3 Evaluation of Impacts
The worse case scenario has been modelled and the results are presented in Table 3.7. The samples of the CALINE4 input and output files are given in Annex C. Both the existing and planned road networks within 500m distance have been included in the model. In accordance with the requirements of the Study Brief, the portal emissions from the proposed noise enclosure for Route 9 has also been taken into consideration in the model.
As indicated in Table 3.7, no exceedances of either hourly NO2 concentration or daily RSP levels have been predicted for all the identified ASRs even assuming the worst case scenario. Therefore, the air quality impact resulting from the operation of Link Roads G & L should be acceptable.
In accordance with the requirements of the Study Brief, both NO2 and RSP concentration Isopleths (Refer to Figure 3.2a & b) have been prepared to illustrate the Year 2018 worst case traffic related air quality impacts within the boundary of 500m from the study area.
Table 3.7 Predicted Air Quality Impacts (µg/m3)
|
ASRs |
|
Location |
Elevated mPD |
Floor Level |
Predicted Hourly NO2(µg/m3) |
Predicted Daily RSP(µg/m3) |
|
ASR1 |
Site 10 (Planned) |
Blk 3 |
5.5 |
G/F |
275 |
159 |
|
ASR2 |
Blk 4 |
5.5 |
G/F |
250 |
162 |
|
|
ASR3 |
Blk 5 |
5.5 |
G/F |
167 |
158 |
|
|
ASR4 |
Blk 6 |
5.5 |
G/F |
172 |
154 |
|
|
ASR5 |
Blk 7 |
5.5 |
G/F |
181 |
153 |
|
|
ASR6 |
School |
5.5 |
G/F |
207 |
179 |
|
|
ASR7 |
Playground |
5.5 |
G/F |
181 |
175 |
|
|
ASR8 |
Mei Foo Sun Chuen |
Phase3, Blk 90 |
5.5 |
G/F |
138 |
111 |
|
ASR9 |
Phase3, Blk 104 |
5.5 |
G/F |
147 |
117 |
|
|
ASR10 |
Phase3, Blk 112 |
5.5 |
G/F |
155 |
122 |
|
|
ASR11 |
Phase3, Blk 132 |
5.5 |
G/F |
147 |
120 |
|
|
ASR12 |
Phase3, Blk 128 |
5.5 |
G/F |
143 |
121 |
|
|
ASR13 |
Open Space Recreation |
Lai Chi Kok Park |
5.5 |
G/F |
159 |
124 |
|
ASR14 |
KMB (Planned) |
Blk1 |
5.5 |
G/F |
177 |
133 |
|
ASR15 |
Blk2 |
5.5 |
G/F |
170 |
129 |
|
|
ASR16 |
Blk3 |
5.5 |
G/F |
161 |
130 |
|
|
|
|
|
AQO Criteria |
300 |
180 |
|
|
Notes: (1) Background NO2 and RSP levels included in the results (2) Bold figure exceeds dust criteria |
||||||
3.6.4 Environmental Implications
Link Roads G & L provides the connection between West Kowloon Highway and Route 9. The traffic forecasts indicate that the trunk roads in the Study Area will be saturated in the year of 2018 and without the provision of Link Roads G & L it is expected that there would be a significant reduction in vehicle speeds on the roads, which combined with the increase in number of vehicles will have an adverse effect on the ambient air quality. The increase in vehicle emissions through reduced speeds and idling of engines will cause significant deterioration in air quality. With the completion of the planned network through the provision of Link Roads G & L, congestion would be reduced, traffic is predicted to flow more smoothly thereby effecting a decrease the vehicle emissions.
3.6.5 Residual Impacts
There are no adverse residual impacts associated with the operation of this Project.
3.6.6 EM&A Requirement
Monitoring of the pollutants concentrations will be required to ensure compliance with the guidelines for dust during construction. Details of the monitoring requirements are given in Section 6.1 with an implementation programme given in the EM&A Manual.
3.6.7 Conclusions
The results of the air quality assessment for the operational phase of Link Roads G & L demonstrate that the predicted pollutant concentrations at ASRs comply with the criteria set by the Hong Kong Air Quality Objectives. Therefore, the air quality in the study area are acceptable during the operational phase of Link Roads G & L.