This section presents the
assessment of potential air quality impact arising from the construction of the
Proposed Beach Development at Lung Mei in Tai Po. 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 impact.
4.2.1
Air Pollution
Control Ordinance (APCO)
and Air Quality Objectives (AQOs)
The principal legislation
for the management of air quality in
Table 4.1: Hong
Kong Air Quality Objectives (mg m-3)
(a)
|
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 |
|
Sulphur Dioxide (SO2) |
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 |
|||||
4.2.2
Other
Relevant Requirements under the Environmental Impact Assessment Ordinance
Annex 4 of the EIAO-TM also requires that a maximum hourly level of TSP of
500 mg m-3 at
ASRs be met for the purpose of assessing potential construction dust impacts.
4.3.1
Baseline
Conditions
The Proposed Beach
Development is located at Lung Mei in Tai Po.
The area around Lung Mei is served by
There is currently no Air
Quality Monitoring Station (AQMS) operated by the Environmental Protection
Department (EPD) in the immediate vicinity of Lung Mei. The nearest EPD AQMS is located at Tai Po
Town Centre. The annual average
concentrations of air pollutants measured at EPD’s AQMS at Tai Po Town Centre
in 2005 have been adopted as the background air quality (Table 4.2).
Table 4.2: Background
Air Quality in Tai
|
Air Pollutant |
Background Concentration (mg m-3) |
|
Total Suspended Particulates (TSP) |
61 |
|
Respirable Suspended Particulates (RSP) |
51 |
|
Nitrogen Dioxide (NO2) |
49 |
|
Sulphur Dioxide (SO2) |
19 |
|
Carbon Monoxide (CO) |
759 (a) |
|
Note: (a) Carbon monoxide was not measured at Tai Po EPD AQMS, and carbon monoxide concentration measured at Tap Mun, which is the next nearest EPD AQMS to the Project Site, is referenced instead. |
|
4.3.2
Identification
of Representative Air Sensitive Receivers (ASRs)
In accordance with the EIA Study Brief Section 3.4.1.3, the
Study Area for the air quality assessment is defined by a distance of 500 m
from the boundary of the Project Site.
Within 500 m of the Project Site boundary, ASRs were identified through
a site visit following the definition of ASRs in Annex 12 of the EIAO-TM. Future or committed ASRs were also identified
according to the latest Outline Zoning Plan (OZP), Outline Development Plan
(ODP) and relevant published land use plans published by Lands Department. The identified representative ASRs are
summarised in Table 4.3 and shown in Figure 4.1.
Table 4.3: Identified
Representative Air Sensitive Receivers
|
ASR |
Description |
Type of
Uses |
Approximate
Separation Distance from the Nearest Site Boundary (m) |
|
A1 |
|
Recreational |
360 |
|
A2 |
Proposed Temporary Depositing of
Two Containers for Selling of Refreshment, Hiring of Fishing related
Accessories and Storage |
Commercial |
380 |
|
A3 |
No. 16A Wong Chuk Tsuen |
Residential |
185 |
|
A4 |
No. 101 Lung Mei Tsuen |
Residential |
23 |
|
A5 |
No. 69 Lo
Tsz Tin Tsuen |
Residential |
50 |
|
A6 |
No. 79 Lo
Tsz Tin Tsuen |
Residential |
50 |
|
A7 |
Hong Kong Eco-Farm |
Recreational |
50 |
|
A8 |
Public Barbecue Area |
Recreational |
135 |
Nuisance from
dust generating activities and gaseous emission from diesel-driven construction
plant may potentially arise from the construction works. The key construction activities for the
Proposed Beach Development are as follows:
·
construction works on land including site formation, localised
widening of Ting Kok Road, construction of vertical seawall/retaining
walls, construction of drainage and sewerage,
and building works;
·
construction of the groynes;
·
construction of western drainage channel and eastern box culvert; and
· sand filling to form the beach.
Excavation and filling,
dredging, materials handling, truck and barge movements and wind erosion of
temporary stockpiles of dusty materials are identified to be the major dust
generating activities.
The construction works
will last for about 2 years tentatively from December 2008 to November 2010
(see construction programme in
Figure 3.2).
Details of each type of
construction works are discussed in the following sections.
4.4.1 Construction
Works on Land
The land-based
construction works include site formation, localised widening of
Excavation
A total of
6,600 m3 of soft materials (mainly
soil) will
be generated from levelling of the existing land (4,000
m3), construction of
vertical seawall/retaining wall (2,000
m3), and localised widening of
During the buildings and landscaping works, about 800
m3 of
excavated
spoil and 10
m3 of
demolition waste such as wasted concrete are expected to be generated during in
the first three months between March and November 2010. About 60% of the total
excavated soil (480
m3) will be temporarily stockpiled on-site for subsequent
backfilling and the remaining portion of excavated soil (320
m3) will be
disposed of offsite by trucks. Within the three-month period, the daily soft
materials generation rate is estimated to be about 11
m3
per day([3])
and about 1 trucks ([4])
Filling
Soil and rock filling are
required to form land to accommodate future beach facilities/road/buildings.
The filling works for for the construction of future beach facilities/road are expected to last for about three months from December 2008 to July 2009. A total of 21,500 m3 of public fill are envisaged to be required for backfilling of construction of retaining wall and utilities (please refer to Section 2.5.2 for breakdown of public fill required for each fill work). A total of 2,400 m3 of aggregate are required to be used as sub-base of carpark and road. The soil and aggregate filling rates are 299 m3 day -1and 33 m3 day -1, respectively. About 3,960 m3 of excavated materials generated from the preceding excavation works will be reused at this stage and the shortfall of 17,540 m3 of public fill will need to be imported. All the imported fill and aggregates will be delivered by trucks. Assuming a capacity of 6 m3 per truck, a total of about 47 truckloads of imported fill materials (including 41 truckloads for imported soil and 6 truckloads for imported aggregates) will be required per day.
Backfilling of building construction will last for about 2.5 months tentatively from August to October 2009. It requires 100 m3 of soil/public fill for backfilling. The excavated soil generated from the preceding excavation works will be reused and hence no public fill is required to be imported.
A summary of the volumes
of excavated and fill materials is provided in Table 4.4.
Table 4.4: Summary of Excavated Spoil and Fill Materials
during Construction
|
|
Soil/Public Fill for Construction of Land |
Building and Landscaping Works |
Aggregate for Sub-base of Carpark and Road |
||||
|
|
Excavation |
Filling |
Excavation |
Filling |
Filling |
||
|
Duration of Activity (days) |
72 (ie 3 months) |
72 (ie 3 months) |
72 (ie 3 months) |
72 (ie 2.5 months) |
72 (ie 3 months) |
||
|
Total Quantity Generated or Required (m3) |
6,600 |
21,500 |
800 |
100 |
2,400 |
||
|
Reuse |
Disposal offsite |
Reuse |
Disposal offsite |
|
|
||
|
3,960 |
2,640 |
480 |
320 |
|
|
||
|
Materials to be Disposed of (+) / Imported (-)(m3) |
-17,540 |
+320 |
-100 |
||||
|
Daily Generation / Filling Rate (m3 / day) |
92 |
299 |
11 |
2 |
33 |
||
|
No. of Daily Truck Trips Required (b) |
7 (c) |
41 (d) |
1 (c) |
- |
6 |
||
|
Notes: (a) Taking into account the reuse of 3,960 of excavated soil from the Project for backfilling, about 17,540m3 (21,500m3 – 3,960 m3) of soil are required to be im[orted. (b) Assuming a capacity of 6 m3 per truck. (c) Truckloads per day are required for offsite disposal of excavated soil. (d) Truckloads per day are required for importing fill materials. |
|||||||
Dust will be generated from excavation and filling, truck movements and wind erosion of open stockpiles of loose soil within the Project Site.
The excavation works for
road widening will be carried out in sections.
As a result, the quantity of excavated soil to be generated from each
section of the road works is expected to be small. In view of the small quantity of excavated
materials generated, the potential for dust generation is considered to be very
low. No adverse construction dust
impacts to the nearby ASRs A4, A5 and A6, despite their proximity to the
Project Site, are expected to arise from the localised road widening works
given the implementation of appropriate dust control measures recommended in Section 4.5.
During the site formation
works, dust control measures recommended in Section
4.5 should be implemented to reduce the fugitive dust emissions. In particular, 60% of excavated soil suitable
for backfilling will be filled immediately after excavation to minimise the
quantity of soil to be stockpiled on site.
All the temporarily stockpiled dusty materials will be covered entirely
or watered to keep wet all the time. The
materials to be delivered offsite will be properly covered and wheel washing
facility will be provided at the exit of the worksite to remove dusty materials
from the body and wheels of site vehicles before they leave the construction
site.
All ASRs except A4 are located at about or more than 50m away from the nearest boundary of excavation or filling works in which the separation distances between these ASRs and the site boundary satisfy the recommendation on minimum buffer distance in the Hong Kong Planning Standards and Guidelines (HKPSG) and hence the dust impact is expected to be acceptable. Although the separation distance between ASR A4 and site boundary is less than 50m (please refer to Table 4.3), the dust impact is anticipated to be low and within the relevant criteria (in view of the small quantity of excavated materials and with the implementation of recommended dust control measures in Section 4.5.1).
In view of small scale of construction works, sufficient separation distances between ASRs and the construction works area and the implementation of dust control measures recommended in Section 4.5.1, no fugitive dust emission is expected at the ASRs.
4.4.2 Construction of Western Drainage Channel and Eastern Box Culvert
A total of 6,400m3 of soft materials and 10m3 of demolition waste such as wasted concrete will be excavated for the construction of western drainage channel and eastern box culvert in the first six months from March 2009 to July 2010. About 60% of the total excavated soil (3,840 m3) will be reused onsite and the remaining portion of excavated soil (2,560 m3) will be disposed of offsite by trucks. Within the six-month period, assuming 24 working days a month and a capacity of 6 m3 per truck, the daily soft materials generation rate is estimated to be about 45 m3 per day ([5]) and about 3 trucks ([6]) are expected to be required per day to dispose of offsite.
The construction of western drainage channel and eastern box culvert will be carried out over eight months (ie 192 days) and two months (ie 48 days) immediately after the excavation works, respectively. A total volume of about 1,980 m3 or an average of 11 m3 per day of rock is required to be imported for western drainage channel. A total of 1,900 m3 of soil/fill are required for construction of western box culvert. By reusing of the soil excavated (ie 3,840 m3) from preceding excavation, no import soil/public fill is deemed necessary.
About 800m3 of rock and 900m3 of aggregates will be required to be imported for the construction of eastern box culvert. About 1,200m3 of soil/public fill is required for backfilling. By reusing of the soil excavated (ie 3,840 m3) from preceding excavation, no import soil/ public fill is deemed necessary.
Dust will be generated from excavation and filling, truck movements and wind erosion of open stockpiles of loose soil within the Project Site. In view of the large particle sizes of rock fill and aggregates, sufficient separations between nearby ASRs and the construction site and the implementation of dust control measure recommended in Section 4.5.1, fugitive dust emission is expected to be minor and no adverse dust impact is anticipated.
4.4.3 Construction
of Groynes
Dredging and rock filling
are required for the construction of the groynes. Taking into account the high moisture content
of the dredged materials, no fugitive dust emission is anticipated.
About 1,600 m3
of rock and 3,000 m3 of armour rocks are required for the
construction of the groynes. The placing
of rock fill is expected to last for 90 days from February to April 2010. Fugitive dust emission is not anticipated
from rock filling owing to the large particle size of the materials to be used.
4.4.4 Sand Filling for the Beach
A
total of 37,500 m3 of sand is required to be filled for the
formation of the beach between April and July 2010. The grain size for the sand to be used is
expected to be between 0.2 and 0.5 mm.
The sand filling will be carried out continuously for three hours per
day, with the filling rate limited to 1,000 m3 per day to minimise
potential water quality impacts. The
sand will be filled using a conveyor belt system installed on barges and it is
expected that only one barge will operate at any one time. The height of the conveyor belt will be adjusted
to minimise the dropping height for the sand fill and to avoid fugitive dust
emission, especially during windy times.
In addition, any sand fill above water mark will be compacted
immediately. Taking into consideration
the relatively large grain size of sand and the implementation of dust control
measures during the filling operations, fugitive dust emission is expected to
be minimal.
4.4.5 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
equipment are expected to be operated within the limited works area at any one
time, as indicated in the construction plant inventory in Appendix D3. 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) No 19/2005 on Environmental
Management on Construction Sites, the potential air quality impacts are
expected to be further reduced.
4.5.1 Mitigation Measures
The following dust
control measures stipulated in the Air
Pollution Control (Construction Dust) Regulations and good site practices
should be incorporated into the Contract Specification and implemented
throughout the construction period:
· Vehicle washing facilities should be
provided at the designated vehicle exit point;
· Every vehicle should be washed to remove
any dusty materials from its body and wheels immediately before leaving the
worksite;
· The load carried by the trucks should be
covered entirely to ensure no leakage from the vehicles;
· Hoarding of not less than 2.4 m high from
ground level should be provided along the entire length of that portion of the
site boundary adjoining a road or other area accessible to the public except
for a site entrance or exit;
· The main haul road should be kept clear of
dusty materials and should be sprayed with water so as to maintain the entire
road surface wet at all the time;
· The stockpile of dusty materials should 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;
· Belt conveyor system should be enclosed on the top and two sides;
· The height of the belt conveyor should be kept as low as possible to avoid delivery at height; and
· All the exposed area should be kept wet
always to minimise dust emission.
Environmental management measures relating to air quality control as recommended in ETWC TC No 19/2005 should also be implemented. Measures of particular relevance to the construction of the Project, other than those recommended above, are as follows:
· All dump trucks entering or leaving the Project Site should be provided with mechanical covers in good service condition; and
·
ULSD should be used for all construction
plant on site.
4.5.2
Residual Impacts
No
residual impact is anticipated from the construction of the Project with the
implementation of the recommended mitigation measures and good site practices.
Sewerage improvement
works from Ting Kok village to Lung Mei village (Agreement no. CE 18/94) will
be carried out tentatively from late 2008 to late 2010 and therefore cumulative
dust impact is likely occurred in the vicinity.
The sewerage improvement works typically involve excavation, laying
sewerage systems and backfilling. It is
anticipated that the construction works will be carried out section by section
and therefore, the excavation area of each section of work will be small and
hence the fugitive dust impact arising from construction of sewerage
improvement works will be minor. With
the small scale of works area of the sewerage improvement works and
implementation of the dust control measures, the cumulative dust impacts
arising from all concurrent projects in the vicinity will be minor.
Whilst fugitive dust
impacts are not anticipated, a construction dust monitoring programme is still
recommended to ensure compliance with the relevant criterion during the
construction works. Monitoring of dust
levels, in terms of Total Suspended Particulates (TSP), should be conducted
every six days throughout the construction period at ASRs A4 (No. 101 Lung Mei
Tsuen) and A6 (No. 79 Lo Tsz Tin Tsuen).
Details of the dust monitoring requirement are summarised in Section 12.2.
In addition, regular site
audits (at a frequency of not less than once every two weeks) are recommended
to ensure that appropriate dust control measures are implemented and good site
practices are adopted throughout the construction period.
Dust generating
activities and gaseous emissions from construction plant for the Proposed Beach
Development may potentially cause air quality impacts to adjacent ASRs. The construction of the Proposed Beach
Development involves site formation, localised widening of
Potential air quality
impacts associated with gaseous emissions of diesel-powered construction
vehicles and equipment are expected to be relatively small as only a small
number of diesel construction vehicles and plant will be operated in the
limited works areas at any one time. The
requirement for all construction plant to use ULSD will further reduce the
potential air quality impacts.
Sewerage improvement
works from Ting Kok village to Lung Mei village is identified to be constructed
concurrently with this Project and cumulative dust impact is likely in the
vicinity. The sewerage improvement works
will be carried out section by section and the construction works area will be
small and therefore the dust impact arising from the sewerage improvement works
will be minor. With the small scale of
works area of the sewerage improvement works and implementation of the dust
control measures, the cumulative dust impacts arising from all concurrent
projects in the vicinity will be minor.
To ensure compliance with
the relevant dust criterion at the ASRs and implementation of appropriate
control measures during the construction phase, a programme for dust monitoring
and site audit has also been recommended.
