This
section presents the air
quality impact assessment during and
after the proposed dredging works for
This section presents the findings of the assessment of potential air quality impacts of the proposed Project in the vicinity of sensitive receivers and is structured as follows:
Section 11.2: Provides discussions on existing environmental legislation, standards, guidelines and criteria;
Section 11.3: Provides a description on the existing environmental conditions;
Section 11.4: Identifies the air sensitive receivers for this Project;
Section 11.5: Identifies the potential air pollution emission sources of the Project;
Section 11.6: Evaluates the potential impacts on air quality;
Section 11.7: Proposes potential mitigation measures to address the identified impacts;
Section 11.8: Evaluates the residual impacts;
Section 11.9: Proposes appropriate environmental monitoring and auditing programme; and
Section 11.10: Summarises the key findings of this section.
Potential air quality impacts associated with the Project have been identified and assessed. As dredging activities of the Project are marine based and no dusty activity is anticipated, negligible dust impact on nearby ASRs is expected during both the construction of the Project as well as for the maintenance dredging activities. Appropriate mitigation measures are proposed to further minimise any adverse air quality impacts as necessary, details of which are further elaborated in the following subsections.
11.2 Relevant Legislation, Standards & Guidelines
11.2.1 Technical Memorandum on Environmental Impact Assessment Ordinance (EIAO-TM)
Assessment Criteria for aerial emission is based on the Hong Kong Air Quality Objectives (“AQO”) for air pollutants given in Chapter 9, "Environment", of the Hong Kong Planning Standards and Guidelines (HKPSG) for air pollution control and are listed in Table 11.1.
Table 11.1: Hong Kong Air Quality Objectives
|
Pollutant |
Concentration in micrograms per cubic metre |
||||
|
Average Time (i) |
|||||
|
1 hour (ii) |
8 hours
(iii) |
24 hours
(iii) |
3 months
(iv) |
1 year (iv) |
|
|
|
800 |
N.A. |
350 |
N.A. |
80 |
|
Total
Suspended Particulates (v) |
500* |
N.A. |
260 |
N.A. |
80 |
|
Respirable
Suspended Particulates |
N.A. |
N.A. |
180 |
N.A. |
55 |
|
Nitrogen
Dioxide |
300 |
N.A. |
150 |
N.A. |
80 |
|
Carbon
Dioxide |
30,000 |
10,000 |
N.A. |
N.A. |
N.A. |
|
Photochemical
Oxidants (as Ozone) (vi) |
240 |
N.A. |
N.A. |
N.A. |
N.A. |
|
Lead |
N.A. |
N.A. |
N.A. |
1.5 |
N.A. |
Note:
(i) Measured at 298K (25ºC) and 101.325 kPa (one atmosphere)
(ii) Not to be exceeded more than three times 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 micrometres and smaller.
(vi) Photochemical oxidants are determined by measurement of ozone only
(*) Acceptable criteria under the EIAO-TM for air quality impact assessment
During the construction
stage, fugitive dust emission shall comply with the standard of hourly average
Total Suspended Particulate (
In accordance with the EIAO-TM, odour impacts predicted at an air sensitive receiver should meet 5 odour units based on an averaging time of 5 seconds.
11.3 Description of the Environment
The Environmental Protection Department (EPD) operates a fixed air quality monitoring station in Kwai Chung. This is the air quality monitoring station which is situated nearest to the Project area. The latest 5-year (2005 to 2009) averaged concentration for Total Suspended Particulates (TSP) was calculated from the annual average pollutant concentrations as recorded at EPD’s Kwai Chung air quality monitoring station and is presented in Table 11.2.
Table 11.2: 5-Year Averaged Annual TSP Concentration in Kwai Chung
|
Pollutant |
Annual Average Concentration, μg/m3 |
|
|
HKAQO |
5-Year
Averaged |
|
|
Total Suspended Particulates (TSP) |
80 |
79 |
According to the data shown in Table 11.2, the Kwai Chung area has high background
11.4 Study Area and Air Sensitive Uses
The Study Area is defined as being within 500m of the dredging site boundary of the Project for the air quality impact assessment according to Section 3.4.4.2 of the EIA Study Brief ESB-198/2008. This assessment area is identified and shown in Figures 11.1a and 11.1b.
11.4.2 Air Sensitive Receivers
Within the 500m assessment area, 24 existing air sensitive receivers (ASRs) were identified according to Annex 12 of the EIAO-TM and Section 3.4.4.3 (ii)(a) of the EIA Study Brief ESB-198/2008 for carrying out the assessment of this Project. No planned / committed ASR including those earmarked on the relevant Outline Zoning Plans, Outline Development Plans and Layout Plans and other relevant published land use plans, including plans and drawings published by Lands Department and any land use and development application approved by the Town Planning Board have been identified within the Assessment Area. All the selected representative ASRs are listed in the following Table 11.3 and their locations shown in Figure 11.2.
Table 11.3: Representative Air Sensitive Receivers
|
No. |
ASR ID |
Description |
Use |
Shortest Distance to Site Boundary (m) |
|
1 |
HLC |
Hutchison Logistics Centre |
Office |
113 |
|
2 |
ATLA |
Asia Terminal Limited Logistics Centre Block A |
Office |
299 |
|
3 |
ATLB |
Asia Terminal Limited Logistics Centre Block B |
Office |
165 |
|
4 |
MC |
Mariners’ Club |
Recreational |
402 |
|
5 |
MTL |
|
Office |
314 |
|
6 |
ICB |
Tsing Yi Industrial Centre Phase 2 Building |
Industrial |
351 |
|
7 |
CPH |
Cheung Ching Estate - Ching Pak House |
Residential |
426 |
|
8 |
CCH |
Cheung Ching Estate - Ching Chung House |
Residential |
480 |
|
9 |
CTH |
Cheung Ching Estate - Ching Tao House |
Residential |
312 |
|
10 |
CKH |
Cheung Ching Estate - Ching Kwai House |
Residential |
317 |
|
11 |
CWH |
Cheung Ching Estate - Ching Wai House |
Residential |
443 |
|
12 |
CYH |
Cheung Ching Estate - Ching Yung House |
Residential |
447 |
|
13 |
CCSC |
Cheung Ching Shopping Centre |
Commercial |
374 |
|
14 |
HITO |
|
Office |
131 |
|
15 |
RGH |
Rambler Garden Hotel |
Hotel |
257 |
|
16 |
MHH |
Mexan Harbour Hotel |
Hotel |
320 |
|
17 |
ROH |
Rambler Oasis Hotel |
Hotel |
383 |
|
18 |
RCT1 |
|
Serviced- Apartments |
442 |
|
19 |
RCT2 |
|
Serviced- Apartments |
418 |
|
20 |
RCT3 |
|
Serviced- Apartments |
395 |
|
21 |
RCT5 |
|
Serviced- Apartments |
348 |
|
22 |
RCT6 |
|
Serviced- Apartments |
325 |
|
23 |
RCSA |
Rambler Crest
Shopping |
Commercial |
353 |
|
24 |
T9OB |
Terminal No. 9 Office Building |
Office |
452 |
11.5 Air Pollution Emission Source
This section covers the requirements stated in Condition 3.4.4.3 (ii)(b) of the EIA Study Brief. The major construction activity involved in the Project is the dredging of marine mud. All dredged mud will be placed on barges for transporting away the site area for disposal.
The construction site of the Project covers works areas of the KTCB, Northern Fairway and Western Fairway as shown in Figures 11.1a and Figure 11.1b. Based on the latest available information on engineering practicality, assumptions have been made on the plant inventory and daily material handling quantity. It has been assumed that a maximum of three dredgers (3 grab dredgers or 1 cutter suction dredger plus 2 grab dredgers) will be used in all the works areas per day, and the total volume of dredging material to be handled is 4000m3 (in-situ volume) per grab dredger per day and 700m3 per 30 minutes for the cutter suction dredger. The confirmation of activity magnitude has been obtained from CEDD and is documented in Appendix 10.3.
The
dredged mud is wet in nature with high water content. According to the latest available
information, no land based works within the Study Area will be involved. Hence no major dust emission activity is
anticipated during the construction of the Project. The
dredged sediment has also been
considered as an air pollution emission source for potential odour
impact.
11.6 Evaluation of Potential Impacts
11.6.1 Impacts from the Project
Most of the identified ASRs are located within 500m from the boundary of the works area in the KTCB. According to the construction schedule, there will be no more than two dredgers in operation at any time in this area.
The construction activities under the Project are dredging activities which are mostly marine based and are not dust generating. Marine sediment will be dredged and disposed of at designated marine disposal sites by barge. The dredged material will have a high moisture content, and fugitive dust emissions are therefore expected to be negligible during the construction period or during the infrequent maintenance dredging activities.
In order to assess the potential odour impact during dredging activities, the levels of acid volatile sulphide (AVS) were tested at selected sediment sampling locations in this Project. The selected sampling locations are within the proposed dredging areas. Most of the locations are adjacent to the Kwai Chung and Tsing Yi Submarine Sewage Outfalls. Sampling locations are shown in Figure 11.3. The detected AVS concentrations in the sediments indicate there is potential for odour to be generated during some of the dredging activities.
Reference
is made to the study report “Agreement
No. CE 4/2004 (TP) South East Kowloon Development Comprehensive Planning and
Engineering Review Stage 1: Planning Review, Situation Report on Odour Issue of
Kai Tak Development, November 2006”
quoted in the EIA Report for Dredging Works for Proposed Cruise Terminal at Kai
Tak[1]. The
report indicated that the measured AVS levels of the sediments collected at Sam
Ka Tsuen Typhoon Shelter and
Similar conclusions have been drawn for the
maintenance dredging in the KTCB which will involve much smaller volumes of
dredging and significantly smaller durations compared to the capital works
programme.
11.6.1 Cumulative Impact
As mentioned in Section 2.8, some projects may be undertaken concurrently with this Project. A summary of the potentially concurrent projects including details of timeframe and distance to this Project is contained within Section 2.8. Most of the identified concurrent projects with details available are far from the proposed works area of this Project (greater than 7km). CT10 is the closest potentially concurrent project with the identified ASR nearest to the site boundary of CT10 and is more than 500m away. However, it was noted that there is no programme for CT10, and no cumulative impacts are predicted. As the potential dust / odour emission is expected to be negligible during construction or any maintenance dredging for this Project, the potential contribution from this Project on any concurrent projects is considered to be insignificant.
11.7 Mitigation of Potential Impacts
Negligible dust impact dust is expected from the proposed dredging activities. To further ensure the minimization of potential air quality impact at the ASRs, requirements of the Air Pollution Control (Construction Dust) Regulation, where relevant, shall be adhered to during the construction and any maintenance dredging activities.
Adverse odour impact during dredging is not anticipated. However, in recognition of good site practice and in order to minimize any potential odour emissions, the dredged sediment placed on barge for more than one day shall be properly covered as far as practicable to minimise the exposed area and hence the potential odour emissions during the transportation of the dredged sediment. If dredged sediment is found to be malodorous it shall be removed from site as soon as possible.
11.8 Residual Environmental Impacts
It is noted that the 5-year average TSP background concentration is already close to the AQO criterion. However, considering the distance between the Project works areas and the nearest identified ASRs (shortest distances to the closest site boundaries from 113m to 480m as shown in Table 11.3) and the nature of the construction works, the dust impact generated contributed by this Project is expected to be insignificant. As discussed above, odour impact is also considered to be insignificant. Hence no residual air quality / odour impact is expected during construction of this Project with implementation of the proposed dust and odour mitigation measures.
11.9 Environmental Monitoring and Audit Requirements
Air quality monitoring is not required. A regular site audit (weekly audit) will be conducted to ensure compliance of the relevant requirements of the Air Pollution Control (Construction Dust) Regulation and the implementation of the proposed odour mitigation measures.
Dredging activities are marine based and no dusty activity is anticipated. Negligible dust impact on nearby ASRs is expected during both the construction of the Project as well as for the maintenance dredging activities. According to the marine site investigation results, the AVS levels of all the sediment samples collected ranged from below the detection limit to 791 mg/kg. As these AVS levels are in the same order of magnitude with the AVS levels of the odour remediated sediments collected from Shing Mun River and Sam Ka Tsuen Typhoon Shelter and the fact that sensitive receivers are located far away from the Project area, it is expected that the potential odour emissions from the sediments within the dredging area of the proposed Project is minimal. Hence, adverse odour impact from the dredging activities is not anticipated.
[1] Maunsell Consultants Asia Ltd.
(Oct 2007). Agreement No. CE 35/2006
(CE), Kai Tak Development Engineering Study cum Design and Construction of Advance Works –
Investigation, Design and Construction, Dredging Works for Proposed Cruise
Terminal at Kai Tak, Environmental Impact Assessment Report