3.1.1
This Section presents an assessment of
the potential air quality impacts pertinent to the construction phase of the
Project, and recommends appropriate mitigation measures, where necessary.
3.1.2
Air quality impacts during the
construction phase would be mainly associated with dust and vehicle emissions
from various construction activities.
Appropriate mitigation measures have been recommended, where necessary,
to alleviate the potential construction dust impacts to acceptable levels.
3.2.1
The criteria for evaluating air
quality impacts and the guidelines for air quality assessment are laid down in
Annexes 4 and 12 of the Technical
Memorandum on Environmental Impact Assessment Process (EIAO-TM),
respectively.
3.2.2
The Air Pollution Control Ordinance
(APCO) provides the statutory authority for controlling air pollutants from a
variety of sources. The Ordinance
includes a number of Air Quality Objectives (AQOs) which stipulate maximum
concentrations for a range of pollutants, of which total suspended particulates
(TSP) are relevant to this study. The
relevant AQO is listed in Table 3.1.
Table 3.1 Hong Kong Air
Quality Objectives
|
Parameter
|
Maximum Average
Concentration (µgm-3)1
|
|
|
24-Hour2
|
Annual3
|
|
TSP
|
260
|
80
|
1. Measured at 298 K and 101.325 kPa.
2 Not to be exceeded more than once per
year.
3. Arithmetic mean.
3.2.3
The EIAO-TM also stipulates that the
hourly TSP level at sensitive receivers should not exceed 500 µgm-3
TSP (measured at 25°C and one
atmosphere) Mitigation measures for
construction sites have been specified in the Air Pollution Control
(Construction Dust) Regulations.
3.3.1
The sites of the drainage improvement
works are located in Mui Wo, Southern Lantau; an area rural in nature and
occupied with mainly village houses. No
major air pollutants source was found in the vicinity of the sites. In the absence of in-situ monitoring data,
reference is made to the annual average concentration of major air pollutants
measured at EPD’s nearest monitoring station (Tung Chung) for the last 4
years. The 4-year annual average TSP
level at Tung Chung is 70 mgm-3
according to Hong Kong Air Quality 1999 – 2002.
3.4.1
According to Annex 12 of the EIAO-TM,
domestic premises, hotel, hostel, hospital, clinic, nursery, temporary housing
accommodation, school, educational institution, office, factory, shop, shopping
centre, place of public worship, library, court of law, sports stadium or
performing arts centre are considered as air sensitive receivers (ASRs). Any other premises or places having similar
sensitivity (in terms of duration or number of people affected) to the air
pollutants may also be considered to be sensitive receivers.
3.4.2
Based on the criteria set out in the
EIAO-TM, representative ASRs have been identified close to the Project
site. A brief description of the
representative ASRs is summarized in Table 3.2 and the corresponding locations
are shown on Figure 3.1.
Table 3.2 Representative
Air Sensitive Receivers
|
NSR
|
Location
|
Use
|
Horizontal
Nearest Distance to Works Area (m)
|
|
Pak Ngan
Heung River
|
|
APNH1
|
No. 22 Village House, Tai
Tei Tong
|
Residential
|
54
|
|
APNH2
|
No. 1 Village House adjacent
to Pak Ngau Heung River
|
Residential
|
125
|
|
APNH3
|
No. 10 Village House
adjacent to Pak Ngau Heung River
|
Residential
|
54
|
|
APNH4
|
Village House, Ling Tsui Tau
Tsuen
|
Residential
|
54
|
|
APNH5
|
No. 6 Village House adjacent
to Pak Ngau Heung Outlet
|
Residential
|
86
|
|
APNH6
|
Village House, Ling Tsui Tau
Tsuen
|
Residential
|
62
|
|
ALT1
|
Village House, Ling Tsui Tau
Tsuen
|
Residential
|
2317
|
|
ALT2
|
No. 75 Village House, Ling
Tsui Tau Tsuen
|
Residential
|
51
|
|
Tai Tei Tong River
|
|
ATTT1
|
No. 256 Village House, Ma Po Tsuen
|
Residential
|
2735
|
|
ATTT2
|
No. 27 Village House, Ma Po
Tsuen
|
Residential
|
1458
|
|
ATTT3
|
No. 236 Village House adjacent to Tai Tei
Tong River
|
Residential
|
64
|
|
ATTT4
|
No. 103 Village House adjacent to Tai Tei
Tong River Outlet
|
Residential
|
55
|
|
ASCH
|
Mui Wo Shcool
|
Education
|
2117
|
|
Luk Tei Tong River and Luk Tei Tong
By-pass Channel
|
|
ALTT1
|
No. 1352 Village House,
Luk Tei Tong
|
Residential
|
168
|
|
ALTT2
|
No. 1924A Village
House, Luk Tei Tong
|
Residential
|
1512
|
|
ALTT3
|
No. 3620 Village
House, Luk Tei Tong
|
Residential
|
326
|
|
ALTT4
|
No. 4 Village House adjacent to Luk Tei Tong River
Outlet1B Village House, Luk Tei Tong
|
Residential
|
61
|
3.5.1
Potential air quality impacts arising
from the construction of the proposed drainage channels would include dust
nuisance and gaseous emissions from the construction plant and vehicles. It is anticipated that dust would be
generated from excavation, material handling and wind erosion from the site
during earthworks and backfilling for the box culvert, road and channel
construction. The potential dust
impacts arising from the drainage improvement works at Pak Ngan Heung River,
Tai Tei Tong River, Luk Tei Tong River and Luk Tei Tong By-pass Channel are
discussed in Section 3.6 below.
3.6.1
The sites of the proposed drainage
improvement works at the Pak Ngan Heung River, Tai Tei Tong River, Luk Tei Tong
River and Luk Tei Tong By-pass Channel would mainly lie on an area of inactive
wet agricultural land. The proposed alignments
would generally follow the existing river alignments. It is expected that the excavated materials would be mainly from
the rivers and their surrounding inactive wet agricultural land and would have
high moisture content. In addition, the
construction materials used for the works would be mainly gabion, grasscrete
and masonry, which are all non-dusty materials. As such, dust emission from materials handling would not be
significant.
3.6.2
In view of the limited scale of the
proposed works, construction dust emissions due to wind erosion and truck
movement on unpaved roads would also be considered minor. Given the high moisture content of spoils,
limited scale of works and implementation of appropriate mitigation measures
and good site practices (as described in Section 3.7), no adverse dust impact
would be expected.
3.6.3
As indicated in Section 2.10,
construction of the Project would likely interface with the projects including
“Outlying Sewerage Stage 2 – Mui Wo Village Sewerage (Package 1A)” (Late 05 to
Mid 07) and “Construction of Emergency Vehicular Access (EVA) and Sewerage
Works at Luk Tei Tong, Mui Wo” (late 04 to late 06). Although the
construction of EVA and sewerage works at Luk Tei Tong would likely coincide
with the proposed drainage improvement works under the Project during the
period of mid 2006 to
late 2006, it is expected that the major construction
works of the EVA and sewerage
works at Luk Tei Tong would have been finished
substantially prior to the start of the Project and only minor construction works would remain during the
coincidence period. As such, adverse cumulative dust impact from the
construction works of this concurrent project would not be anticipated.
3.6.4
For the proposed sewerage works under
the Mui Wo Village Sewerage, it would take place in the vicinity of the Pak
Ngan Heung River and is expected to be small-scale. There would be limited potential for adverse cumulative dust
impact from the minor construction activities of this concurrent project. Hence, adverse cumulative dust impact from
the construction works of this concurrent project would not be
anticipated.
3.7.1
To ensure compliance with the
guideline level and AQO at the ASRs, the Air
Pollution Control (Construction Dust) Regulation should be implemented and
good site practices should be incorporated in the contract clauses to minimize
construction dust impact. A number of
practical measures are listed below:
·
Use of regular watering to reduce dust
emissions from exposed site surfaces and unpaved road, with complete coverage,
particularly during dry weather;
·
Use of frequent watering for
particularly dusty static construction areas and areas close to ASRs;
·
Tarpaulin covering of all dusty
vehicle loads transported to, from and between site location;
·
Establishment and use of vehicle wheel
and body washing facilities at the exit points of the site; and
·
Routing of vehicles and positioning of
construction plant should be at the maximum possible distance from ASRs.
3.8.1
With the implementation of the
proposed dust suppression measures and good site practices, no adverse residual
impact would be expected.
3.9.1
With the
implementation of mitigation measures stipulated in the Air Pollution Control
(Construction Dust) Regulation, no adverse air quality impact
arising from construction works would be expected. Hence, no air quality monitoring
would be required during construction of the Project. It is recommended that regular site inspections during construction phase be carried out to ensure that the mitigation
measures are properly implemented.