6.1
Introduction
This Section
presents the assessment of potential air quality impact arising from the
construction and operation of the Project.
Dust generated from the construction activities and gaseous emissions from
construction plant are potential concerns during the construction phase. Representative Air Sensitive Receivers (ASRs)
have been identified and control measures have been recommended to minimise the
potential impacts.
6.2
Legislation Requirement and Evaluation Criteria
6.2.1
Air
Pollution Control Ordinance (APCO) and Air Quality Objectives (AQOs)
The principal legislation for the management of air
quality in
Table 6.1
|
Air Pollutant |
Averaging Time |
||||
|
|
1
Hour (b) |
8
Hour (c) |
24
Hour (c) |
3
Months (d) |
1
Year (d) |
|
Total Suspended Particulates (TSP) |
- |
- |
260 |
- |
80 |
|
Respirable Suspended Particulates (RSP) (e) |
- |
- |
180 |
- |
55 |
|
|
800 |
- |
350 |
- |
80 |
|
Nitrogen Dioxide (NO2) |
300 |
- |
150 |
- |
80 |
|
Carbon Monoxide (CO) |
30,000 |
10,000 |
- |
- |
- |
|
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 |
|||||
6.2.2
Other
Relevant Requirements under the Environmental Impact Assessment Ordinance
A maximum hourly TSP level of
500 mg m-3 at Air Sensitive Receivers (ASR) is also stipulated in the EIAO-TM to assess potential construction
dust impacts. The measures stipulated in
the Air Pollution Control (Construction
Dust) Regulation should also be
followed to ensure that any dust impacts are reduced.
6.3
Baseline Condition and Background Air Quality
The Project Site is located in a densely populated
area in Central dominated by residential and commercial buildings. It is bounded by
The nearest EPD’s Air
Quality Monitoring Station (AQMS) is located at the Central/Western
District. The last 5 years annual
average concentrations (2005-2009) of air pollutants measured at this AQMS have
been adopted as the background air quality (see Table 6.2).
Table 6.2 Background Air Quality (a)
|
Air Pollutant |
Background Concentration (μg m-3) |
|
Total Suspended Particulates (TSP) (a) |
77 |
|
Respirable Suspended Particulates (RSP) |
52 |
|
Nitrogen Dioxide (NO2) |
54 |
|
|
22 |
|
Notes: (a)
5 years
annual average concentrations (2005-2009) of air pollutants measured at EPD’s AQMS in the Central/Western District
(http://www.epd-asg.gov.hk/english/report/aqr.php) |
|
6.4
Identification of air Sensitive Receivers
In accordance with the EIA Study Brief Section 3.4.4.1 of the
Project, the Study Area for the air quality impact assessment is defined by a
distance of 500m from the boundary of the Project Site. ASRs including domestic premises, offices,
commercial uses, hotels, schools and places of public worship were identified
in accordance to Annex 12 of EIAO-TM.
Future or committed ASRs according to the latest Outline Zoning Plans
(OZP), Outline Development Plan (ODP) and relevant land use plans published by
Lands Department were also reviewed. The
first layer of ASRs around the Project Site is selected as representative ASRs
for the impact assessment. They are summarised in Table 6.3 and shown in Figure 6.1.
Table 6.3 Identified Representative Air Sensitive
Receivers
|
ASR |
Description |
Type of Use |
Maximum
Height (m above ground) |
Separation
Distance from the Nearest Site Boundary (m) |
|
A1 |
Au’s Building |
Commercial |
20 |
14 |
|
A2 |
Chinachem Hollywood Centre |
Commercial |
90 |
14 |
|
A3 |
|
Commercial |
70 |
17 |
|
A4 |
Vimark House |
Residential / Commercial |
60 |
24 |
|
A5 |
Yu |
Commercial |
40 |
32 |
|
A6 |
The Centrium |
Commercial |
110 |
13 |
|
A7 |
Chancery Mansions |
Residential |
70 |
8 |
|
A8 |
Chancery House |
Residential |
35 |
8 |
|
A9 |
|
Residential |
40 |
10 |
|
A10 |
|
Residential |
20 |
13 |
|
A11 |
Old |
Residential |
90 |
10 |
|
A12 |
Ho Fook Building |
Residential/ Commercial |
35 |
13 |
|
A13 |
Winning House |
Commercial |
20 |
11 |
6.5
Evaluation of Impacts during Construction
Phase
The
construction and modification works with the operation of diesel-driven
construction plant have the potential cause dust
nuisance and adverse air quality impact to the identified ASRs if not properly
managed. The key construction activities
for the Project are as follows:
·
Foundation works for the new buildings, construction of the basements at
the lower courtyard, and construction of tunnels under A Hall and B Hall and
M&E trenches;
·
Construction of new buildings, including the Old Bailey Wing and the Arbuthnot
Wing adjacent to the upper courtyard and footbridge;
·
Modification/refurbishment works of existing buildings; and
·
Small-scale demolition of sub-standard ancillary structures and walls.
Soil
excavation, materials handling, truck movements within the Project Site and
wind erosion of temporary open stockpiles of dusty materials are identified to
be the major dust generating activities.
The
construction works will last for about 30 months tentatively from January 2012
to June 2014 (see construction programme in Figure 2.8). Details of each type of construction works
are discussed in the following sections.
6.5.1
Site
Formation Works
Excavated materials
will be generated from the excavation works for construction of the building
foundations, basements, underground tunnels and M&E trenches. The excavation works will be carried out for
about 17 months from January 2012 to May 2013.
A total of 12,900 m3 of soil
will be excavated, including 4,000 m3 from the construction of
basement for the plant rooms in the Lower Courtyard, 600 m3 from the
construction of the underground tunnels, 7,500 m3 from the
construction of the basements and foundations of new buildings (ie Old Bailey Wing and Arbuthnot Wing) and 800 m3
from other miscellaneous works. Only a
small amount of the excavated materials will be re-used for backfilling. As stockpiling of excavated materials within
the Project Site is not practical given the limited space available, the
excavated soil will be disposed to the government
public filling reception facilities by trucks. With reference to Section 8.3.1, about 6 truck trips will be generated per day for
the disposal of surplus excavated soil off-site during the period for
excavation works.
In view of the small quantity of excavated
material to be generated and disposed off-site over the 17 months construction
period and with the implementation of dust control measures recommended
in Section 6.7, the potential dust
emission from the Project Site will be limited.
No adverse dust impacts on the identified representative ASRs are
anticipated.
6.5.2
Construction
of New Buildings and Refurbishment Works of Existing Buildings
The construction of the new
buildings in the upper courtyard is anticipated to start upon completion of
site clearance works. The bottom to top
approach will be adopted for the concreting works of the basement, including
works such as propping erection, formwork shuttering, rebar fixing, concreting
and striking formwork. The
superstructure with steelwork will then be erected with temporary support. The building construction works will be
carried out for about 15 months from April 2013 to June 2014.
The existing buildings in the CPS
will be modified and refurbished. Floors
will be strengthened to accommodate the anticipated larger floor loading. Fitting of modern services and improvements
of the fire compartment and fire escape provisions will also be necessary. The building refurbishment works will be
divided into four phases as described in Section
2.6.2 and illustrated in Figure 2.8, and be
carried out for about 30 months from January 2012 to June 2014.
The
concreting works are the
major works for construction of new buildings and renovation of existing
buildings. No fugitive dust emission is
expected from this activity. No adverse
dust impact is therefore anticipated during construction of new buildings and
refurbishment works of existing building.
However, dust control measures recommended in Section 6.7 will be implemented during the works to further
minimise dust generation.
6.5.3
Demolition
of Building Structures
Demolition
of existing sub-standard structures and walls will be carried out for about a month in January
2012. 28 trucks per
month are required for disposing demolition materials, averaging to less than 1
truck trip per day. Given the short duration and small scale
of the demolition works and with the implementation of dust control measures
recommended in Section 6.7, no
adverse dust impact is anticipated.
6.5.4
Gaseous
Emissions from Diesel-powered Construction Equipment
The potential air quality impacts associated with the
gaseous emissions from diesel-powered construction equipment are expected to be
relatively small as only a small numbers of such plant are expected to be
operated within the limited works area at any one time, as indicated in the
construction plant list in Appendix 5B. In addition, all construction plant on public
works sites is required to use ultra-low-sulphur diesel (ULSD) (defined as
diesel fuel containing not more than 0.005% sulphur by weight) as stipulated in
Environment, Transport and Works Bureau
Technical Circular (ETWB-TC(W)) No 19/2005 on Environmental Management on Construction Sites, no air quality
impacts are expected.
6.6
Evaluation of Impacts during Operation Phase
6.6.1
Emissions
from the Project
Gaseous emissions from kitchens are identified as
potential sources of air pollutants.
Electric stoves will be installed in the kitchens within the Project,
and therefore no gaseous or liquid fuels will be used for cooking
operations. Electrostatic precipitators
(ESPs) will also be installed at the exhausts of the
kitchens to capture potential particulate emissions and the location of the
exhaust will be sited vertically upward and away from the nearby air sensitive
uses as far as practicable. As such, potential
air quality impacts associated with gaseous emissions from kitchen operations
to the surroundings are not anticipated.
6.6.2
Stack
Emissions in Surrounding Areas
Three stacks were
identified during a site visit conducted in September 2010 and the locations of identified stacks are
illustrated in Figure 6.2. These identified stacks belong to restaurants
and they were observed to be in use. The
nearest stack is located at about 70m from the Site boundary and all the stacks
were identified to be at
least 30m above ground with high-rise buildings located in between. Through the interview with
the stack owners, one of the restaurants indicated that Towngas
was used for the cooking stoves. However, the owners of the other two stacks
refused to provide stack emissions information.
Nonetheless, it is anticipated that both premises are using ultra
low sulphur diesel (ULSD), gaseous fuel or alternative fuel types in
which emissions
must comply with
the requirements in the Air Pollution Control (Fuel Restriction)
Regulation and its
amendment of 2008.
Nitrogen dioxide (NO2)
and sulfur dioxide (SO2) are the key air pollutants from the stack
emissions. The five-year average of NO2 (54mgm-3) and SO2 (22mgm-3) data from 2005
to 2009 recorded at the Central/Western AQMS (refer to Table 6.2) demonstrated that the ambient
concentrations of the respective pollutants are low. As a result, no adverse air quality impacts
are anticipated for the Project.
6.6.3
Traffic
Emissions from Project
The design
of the Project encourages visitors to get to the Site via footbridge and
pedestrian crossings. Traffic flow
induced by operations of the Project (eg tourist buses and private
cars) is therefore expected to be very small as compared to the existing
traffic flow on nearby roads, especially
6.7
Cumulative Impacts
One potential concurrent
construction work is identified within the Study
Area. The former Police Married Quarters
on
Since the electric stoves will be used for kitchens at
the Site and the recent 5-year average NO2 and SO2
monitoring data obtained from EPD AQMS show the compliance of AQOs in the area, no adverse cumulative stack emissions are anticipated during operation phase of
the Project.
As the design of the Project encourages
visitors to get to the Site via footbridge and pedestrian crossings, traffic
flow induced by operations of the Project (eg tourist
bus and private cars) is anticipated to be small. As discussed in Section 6.6.3, no adverse cumulative traffic emission impact during
the operation phase of the Project is therefore expected.
6.8
Mitigation Measures
6.8.1
Construction Phase
The following dust control measures stipulated in the Air Pollution Control (Construction Dust)
Regulations and good site practices will be incorporated into the Contract
Specification and implemented throughout the construction period:
·
The area at which demolition work takes place will be sprayed
with water or dust suppression chemical immediately prior to, during and
immediately after the demolition activity;
·
Impervious dust screen or sheeting will be implemented for
demolition of structures and renovation of outer surfaces of structures that
abuts or fronts open area accessible to the public to no less than 1m higher
than the highest level of the structure being demolished;
·
An effective dust screen will be provided to enclose
scaffolding, if required, from the ground floor level of building for
construction of superstructure of the new buildings;
·
Impervious sheet will be provided for skip hoist for
material transport;
·
Vehicle washing facilities will be provided at the
designated vehicle exit points;
·
Every vehicle will be washed to remove any dusty materials
from its chassis and wheels immediately before leaving the worksite;
·
Road sections between vehicle-wash areas and vehicular
entrances will be paved;
·
The load carried by the trucks will be covered entirely to
ensure no dust emission from the vehicles;
·
Hoarding of not less than 2.4m high from ground level will
be provided along the length of the Project Site boundary adjoining a road
where the new buildings (Old Bailey Wing and Arbuthnot Wing) will be located;
·
The main haul road will be kept clear of dusty materials and
will be sprayed with water so as to maintain the entire road surface wet at all
the time;
·
Temporary stockpiles of dusty materials will be either
covered entirely by impervious sheets; place in an area sheltered on the top
and three sides; or sprayed with water to maintain the entire surface wet at
all the time;
·
Stockpiles of more than 20 bags of cement, dry pulverised
fuel ash and dusty construction materials will be covered entirely by
impervious sheeting sheltered on top and 3-sides;
·
All exposed areas will be kept wet always to minimise dust
emission;
·
ULSD will be used for all construction plant on-site;
·
The engine of the construction equipment or trucks
during idling will be switched off; and
·
Regular maintenance of construction equipment deployed
on-site will be conducted to prevent black smoke emission.
6.8.2
Operational Phase
The following measures will be implemented for kitchens
to minimize the potential kitchen fumes or stack emissions:
·
Electric stoves will be used;
·
Electrostatic precipitators (ESP) will be installed to control the oily
fume and cooking odour;
·
Siting the kitchen exhausts away from the nearby air sensitive
uses as far as practicable;;
·
Direct the kitchen exhausts vertically upwards; and
·
Provide sufficient separation distance from the nearby air sensitive
uses.
6.9
Residual Impacts
No residual impact is anticipated from the
construction of the Project with the implementation of the recommended
mitigation measures and good construction site practices.
No residual impact is anticipated from the
operation phase of the Project with the implementation fo the recommended mitigation measures.
6.10
Environmental Monitoring and Audit
Adverse fugitive dust impact is not anticipated
during the construction period, dust monitoring is considered not
necessary. However, monthly
environmental site audits are recommended to ensure that appropriate dust
control measures are properly implemented and good construction site practices
are adopted throughout the construction period.
6.11
Conclusions
6.11.1
Construction
Phase
Dust generating activities and gaseous emissions from
construction plants for the Project have the potential to cause adverse air
quality impacts to the identified ASRs if not properly managed. The construction of the Project involves
small-scale site formation/foundation works, new building construction, refurbishment
works for the existing buildings, and minor-scale demolition of existing
structures. Excavation, truck movements,
materials handling and wind erosion of open stockpiles of dusty materials were
identified as the major dust generating activities. In view of the small size of the worksite and
small quantity of excavated materials to be generated, limited excavated soil
will be stockpiled on-site. No adverse
fugitive dust impact is envisaged with the implementation of dust control
measures and adoption of good construction site practices.
Minor air quality impacts associated with gaseous
emissions of diesel-powered construction plant and equipment are anticipated as
only a small number of construction vehicles and plant will be operated in the
limited works areas at any one time.
To ensure compliance with the relevant dust criterion
at the identified ASRs and implementation of proposed control measures during
the construction phase, regular environmental site audits (at a frequency of
not less than once per week) are recommended.
6.11.2
Operation Phase
During operation phase, it is confirmed that electric
stoves will be used for the kitchens and electrostatic precipitators (ESPs) will also be installed at the exhausts of the kitchens
to capture potential particulate emissions.
Proper siting of kitchen exhaust will be
considered during the detailed design stage.
As such, potential air quality impacts associated with gaseous emissions
from kitchen exhausts are not anticipated.
Three stacks were identified to be in operation within
the study area and were all operated by restaurants. They are all located at
least 30m above ground. It was anticipated that these
operating stacks
were operating with towngas or ULSD or alternative
fuel types in which emissions are low and comply with the
requirements in the Air Pollution Control (Fuel Restriction)
Regulation and its
amendment of 2008. With respect to the
height of emission points,
the presence of high-rise buildings located between the Project site boundary
and the operating stacks and the recent 5 year NO2 and SO2
monitoring data obtained from the nearby EPD AQMS, no adverse air quality impacts are anticipated for
the Project.
The design
of the Project encourages visitors to get to the Site via footbridge and
pedestrian crossings, therefore, traffic flow induced
by operations of the Project (eg tourist buses and private
cars) is anticipated to be small as compared to the existing traffic flow on
nearby roads. No adverse traffic emission
impact during the operation phase of the Project is therefore expected.