6.1.1
One of the objectives of this EIA
study is to evaluate the degree of risk of the landfill gas (LFG) associated
with the proposed project (Tai Po Sewage Treatment Works, Stage V) and to
propose measures to mitigate the impacts during the construction and
operational phase of the proposed project.
As the Project Site falls within the 250m Consultation Zone of Shuen Wan
Landfill, a detailed qualitative landfill gas hazard assessment is required in
accordance to the EIA Study Brief No.ESB-076/2001 issued in June 2001. Figure
6.1 shows the location plan of the project site, Shuen Wan Landfill and its
250m Consultation Zone.
6.1.2
Infiltration of water into a landfill
will cause gases to be generated as biochemical decomposition of organic
materials occurs. Once biodegradation
has started the oxygen is soon exhausted, and as no replenishment of the free
oxygen is available, the tip becomes anaerobic.
6.1.3
Anaerobic decomposition of the organic
waste can be simplified into two basic stages.
In the first stage, the complex organic materials in the tipped waste
are biodegraded into simpler organic materials which are typified by salts of
acetic acid, propionic acid, pyruvic acid or other simple organic acids and
alcohols. The second stage of anaerobic
decomposition is methane formation or methanogenesis. Methanogenic bacteria
utilise the end products from the first stage and yield methane and carbon
dioxide. These two gases are the most
abundant of LFG which may also include gases such as hydrogen sulphide,
hydrogen and nitrogen.
6.1.4
The generation of LFG is dependent on
some factors related to environmental conditions and waste characteristics. These factors include temperature, pH,
substrate availability, moisture content, and oxygen content. These factors are influenced by the
configuration of the landfill site, the characteristics of the waste and the
way in which the waste are placed, the restoration of the landfill, and the
provision of landfill gas and leachate management systems.
6.1.5
A typical composition of LFG is about
60% volume of methane and 40% volume of carbon dioxide, although these
percentages can vary widely depending on the site conditions. Also present are trace quantities of
hydrogen sulphide, nitrogen and gaseous hydrocarbons such as hexane, octane and
heptane.
6.1.6
Methane has a low solubility in water,
is colourless and odourless, and generally of little influence in groundwater
quality. It occurs in gaseous form in
the unsaturated zone. The gas, which is
also an asphyxiant, is highly flammable and can be explosive when all the
following conditions exist at the same time:
i)
its concentration in air is between 5%
of the Lower Explosive Limit (LEL) and 15% of the Upper Explosive Limit (UEL);
ii)
the gas is in a confined space; and
iii)
a source of ignition exists.
6.1.7
Control limits are usually set at
levels which provide a margin of safety 10 - 20% of the LEL (i.e. 0.5 - 1%
volume of methane).
6.1.8
Carbon dioxide is colourless,
odourless, and non-combustible. This
gas is an asphyxiant. A concentration
of 3% by volume in air can cause headaches and difficulty in breathing to human
beings. Symptoms become severe at concentration above 5% by volume and
unconsciousness can result at 10% by volume. Concentrations above 15% volume
may be fatal. As for methane, control
limits are often set at levels that provide a margin of safety. For instance, occupational limits for carbon
dioxide in the UK are 0.5% volume 8-hour time-weighted average, and 1.5% volume
15-minute time-weighted average.
6.1.9
LFG migration can be a dangerous
hazard because of the combustible and in some cases explosive nature of the
methane; and the asphyxiant nature of the carbon dioxide.
6.1.10
The principal cause of LFG migration
is pressure gradients within the landfill which result in gas pressures within
the fill being relieved by escape of the gas along paths of least resistance
(i.e. greatest pressure loss). Diffusion is a minor mechanism of gas
movement. Since movement under pressure
is not dependent on concentration, gas concentrations do not necessarily fall
in proportion to distance from the landfill.
It is therefore possible for high concentrations of gas to be found
several hundred metres away from a landfill where pathways of low resistance
permit migration to occur.
6.1.11
Although methane is less dense than
air, carbon dioxide is denser. A gas
containing 54% methane and 46% carbon dioxide is nearly as dense as air. Therefore, LFG can be more or less buoyant
than air, depending on its composition.
Consequently, it is dangerous to assume that LFG will always rise. When
it is denser than air it can accumulate at low levels and persist unless forced
to move through air movements or pressure build-up.
6.1.12
LFG has the potential to cause fire,
explosion or asphyxiation if it migrates into and accumulates in confined space
such as building basements, underground car parks, lift shafts, pumping
stations, and maintenance chambers. For
the same reasons, temporary structures such as site huts and any other
unventilated enclosures erected during the construction stage are also exposed
to LFG hazards. Underground services,
such as sewer drains, storm drains and service ducts, may also be susceptible
to the potential hazards as they act as pathways for LFG. Besides, any faults present in geological
formation also act as pathways for LFG.
6.1.13
The potential hazards that may arise
during the construction phase of this project include fires and explosions,
asphyxiation of personnel and toxicity effects
6.2.1
The criteria for assessing landfill
gas hazard are outlined in Annex 7 and Annex 19 of the Technical Memorandum
on Environmental Impact Assessment Ordinance (EIAO-TM), respectively.
6.2.2
In addition, Environmental Protection
Department (EPD) has issued two guidance notes regarding LFG hazard assessment,
namely ProPECC PN 3/96 - Landfill Gas Hazard Assessment for Development
Adjacent to Landfill and EPD/TR8/97 Landfill Gas Hazard Assessment
Guidance Note. These two guidance
notes set out the conditions under which a LFG hazard assessment should be
carried out and provide guidance on undertaking LFG hazard assessment. The guidance notes recommend that in
general, assessment of LFG hazard is required for proposed developments that
lie within the 250m Consultation Zone around a landfill.
6.2.3
Since the Project Site of Tai Po
Sewage Treatment Works – Stage V is located within the 250m Consultation Zone
of Shuen Wan Landfill, a qualitative landfill hazard assessment is required to
be undertaken for the captioned project.
6.2.4
The mentioned criteria and guidance
notes recommend that at the planning stage of a development, the LFG hazard
assessment should be of detailed qualitative nature.
Proposed Project
·
Modify and expand the existing
secondary treatment process, including construction of additional sewage
treatment and sludge treatment process units;
·
Upgrade the sewage treatment process;
and
·
Demolish part of the existing
treatment units.
Shuen Wan Landfill
History
6.3.2
Shuen Wan Landfill was opened for the
reception of waste in 1973 and closed in August 1995. Landfilling was carried out under a series of contracts and the
waste received included municipal, construction and industrial and
commercial. The landfill site is located
to the east of Tai Po in the New Territories.
The Site has a total area of approximately 50 hectares. The site is
bounded to the north by Ting Kok Road and by the Fortune Garden residential
development to the east. North of Ting
Kok Road, the land rises to the ridgeline of Pat Sin Mountain Range. Tolo Harbour bounds the site to the south
and the east. To the west, Tai Po
Industrial Estate occupies the area of reclaimed land between the site and Tai
Po. At present, the landfill is used as
a temporary golf driving range. The
plant and operation for the site include the landfill gas management system and
the leachate management system.
Restoration Works
6.3.3
The restoration works for Shuen Wan
Landfill commenced in December 1996 and was completed in December 1997. Since then, environmental monitoring (e.g.
landfill gas, groundwater, leachate, surface water, etc.) and audit has been
conducted. The Defect Correction Period
commenced in January 1998 and ended in December 1998. The Aftercare Period is from January 1999 onwards.
6.3.4
The restoration works for the landfill
include landfill gas management, landfill gas utilisation, groundwater
management, surface water management, restoration infrastructure, restoration
capping system, landscape restoration and slope stability study.
6.3.5
The landfill gas management system
consists of active extraction wells, flaring system for LFG, passive vent
trenches/pipes, and monitoring of LFG both on site and off site. The LFG gas extraction system is integrated
with the leachate management system.
The site plans for landfill gas management system at Shuen Wan Landfill
are shown in Figures 6.2a-d.
6.3.6
Active gas extraction from the waste
is used to relieve the pressure build-up in the waste to prevent LFG from
migrating off-site laterally or vertically.
The extracted LFG is delivered to the Hong Kong and China Gas Company
through the landfill gas utilization treatment plant. The flaring system is not operating at present.
6.3.7
The leachate management system
consists of the active leachate extraction system, leachate collection chambers
and the leachate pre-treatment plant.
6.3.8
The existing active leachate
extraction system is used to pump the leachate from the platform to the
existing leachate collection chambers.
Three leachate collection chambers are located on the perimeter of the
site, which collect the leachate intercepted by both peripheral drains beneath
part of the 30m and 40m side slope capping systems and a series of horizontal
sub-drains. The leachate collected in
the chambers No. 1, No. 2 and No. 3 is pumped to the Leachate Pre-Treatment
Works and finally the leachate is discharged to the Tai Po Sewage Treatment
Works. Figure 6.3 shows the locations of the three leachate pumping
chambers.
Landfill Capping
6.3.9
The components of the landfill
restoration capping system include the following (from top to bottom):
i)
An 850 mm thick layer of
general cover, (hydrodseeded) to act as the growing medium;
ii)
A
drainage layer was provided on the +30 mPD and +40 mPD platform surfaces and
the slope between the two surfaces.
This layer serves to reinforce the system and to protect the underlying
geomembrane from puncture;
iii)
A
flexible membrane liner consisting of a 1.0 mm thick VFPE geomembrane or
equivalent which is joined by welding;
iv)
A geotextile which functions as a reinforcement layer and gas
venting layer for the system and provides protection against puncture of the geomembrane; and
v)
A thick layer of intermediate
cover soil.
Geological Assessment
6.3.10
According to the geological map Hong Kong Geological Survey, Sheet 7, Series
HGM20 Edition 1-1986 (scale 1:20,000) (published by Geotechnical Control
Office in 1986), the geological formation beneath Shuen Wan Landfill comprises
of sanitary fill (principal materials: natural earth and waste) and marine sand
(principal materials: shelly and sand).
The geological formation beneath
the Tai Po Sewage Treatment Works comprises of sanitary fill (principal
materials: natural earth and waste) and marine mud (principal materials: clay,
silt and shelly sand).
6.3.11
The geology map for Shuen Wan Landfill
and the project site (i.e. Tai Po Sewage Treatment Works) is provided in Figure
6.4a-b.
6.4.1
This qualitative LFG hazard assessment
was undertaken following the method recommended in EPD/TR8/97 Landfill Gas
Hazard Assessment Guidance Note.
This method is based on the “Source – Pathway – Target” model. The meaning of these three components are as follows:
a)
Source – location, nature and likely
quantities/ concentrations of LFG which have the potential to affect the
development;
b)
Pathway – the ground and groundwater
conditions, through which LFG must pass in order to reach the development; and
c)
Target – elements of the development
that are sensitive to the effects of LFG.
6.4.2
The LFG source, identified pathway(s),
and identified target(s) were then categorised in order to facilitate the
assessment process.
Landfill Gas
6.4.3
Landfill gas generation is dependent
upon a number of factors, including: temperature, pH, substrate availability,
moisture content and oxygen level.
According to Shuen Wan Landfill – Annual Environmental Audit Report
and Utilization Plant Operation and Maintenance
Report (prepared by the Hong Kong Landfill Restoration Group), the landfill
gas recovery rate was 1,500 m3/hr for 1996, which is predicted
decline according to a first order kinetic decay model to 900 m3/hr
by 2006 and 700 m3/hr by 2016.
The total LFG production volume from September 1999 to December 2000 was
around 14 million m3, from January 2001 to December 2001 was around
8.3 million m3, from January 2002 to December 2002 was around 6.1
million m3 and from January 2003 to December 2003 was around 5.8
million m3.
6.4.5
The data in Appendix 6.1 shows
that the concentration of methane at the gas probes located at the west of
Shuen Wan Landfill ranged from 0.0% to 21.4% with concentration higher than
1.0% recorded at GMP2 (during May and June 03), GMP3 (during May and June 03)
and GMP5 (during May and June 03). The
concentration of carbon dioxide at the gas probes located at the same locations
ranged from 0.0% to 23.7% with concentration higher than 5.0% recorded at
GMP2-GMP7(peak
at May and June 03), GMP9 (peak at June 03) and GMP14 (peak at May and June 03). With reference to Section 3.10 of Landfill
Gas Hazard Assessment Guidance Note (EPD/TR8/97), the source of LFG at
Shuen Wan Landfill is categorised as Major. The level of risk is likely to continue for
the coming one to two years. The
adoption of precautionary measures recommended in Section 6.6 should be
confirmed during the Construction Stage by reviewing the monitoring data.
Leachate
6.4.6
Leachate is unlikely to affect the proposed project site. This is because monitoring of the
groundwater quality at the perimeter wells performed on a quarterly basis can
show whether leachate is migrating to off-site areas. From the past year 2003, nitrogen concentration (e.g. TKN) and
COD concentration at the groundwater wells is in the range 0.1-3.4mg/l and 2.0-400.0mg/l
respectively. In addition, capping
layer and leachate extraction system was installed at Shuen Wan landfill during
the restoration period (i.e. in 1997) in order to control the flow direction
and leachate level. The leachate
collected in the chambers through the drain pipes is pumped to the Leachate
Pre-Treatment Works and finally the leachate is discharged to the Tai Po Sewage
Treatment Works and thus leachate affecting the construction and operation
phase of the proposed project site would be minimal.
Migration Pathways
Natural Pathways
6.4.7
For the natural pathways, the presence
of natural cavities is directly related to the prevailing local geology. The
key concern is the presence of fault lines that LFG may exploit as a
preferential migratory pathway. The
geological formation beneath the proposed project site mainly comprises of
natural earth overlying marine mud.
There are no significant fault lines persisting between Shuen Wan
Landfill and the project site directly.
However, the path length between the western boundary of Shuen Wan
Landfill and the project site is less than 50m, since most construction works
will be undertaken at the eastern side of the Tai Po STW site which is next to
the landfill site. Therefore, the
natural pathways are categorised as Very Short/Direct. A cross section between Shuen Wan Landfill
and the project site is illustrated in Figure 6.6.
Man-made Pathways (Utilities)
6.4.8
Based on the existing layout plans
from CLP Power, Town gas and Water Supplies Department regarding the services
and utilities (i.e. electricity cables, gas pipelines and water mains
installation) located in the vicinity of the project site and the western
boundary of Shuen Wan Landfill, there are no existing man-made services and
utilities linking directly between Shuen Wan Landfill and the project
site. The man-made pathways such as the
electricity cables and gas pipelines are mainly within the boundary of both
sites but not directly linking each other.
Therefore, the man-made pathways are categorised as Long/Indirect. Letters and layout plans regarding the above
man-made services and utilities are provided in Appendix 6.2. Migration of landfill gas through new
pathway, which may include new underground utilities, excavated trenches, etc.,
in particularly linking up Landfill Site and TPSTW will likely cause
fundamental change to the assessment.
6.4.9
Based on the key elements of the
expansion and modification works at the Tai Po Sewage Treatment Works Stage V,
there are some potential targets associated with this project:
·
Excavation for construction of
services, sewage clarifiers and treatment facilities/process during
construction phase;
·
Manholes, inspection chambers or voids
of services/utilities during operational phase.
6.4.10
It is anticipated that deep
excavations for the services, clarifier and treatment process would be involved
during the construction phase of the proposed project. According to Section 3.18 of Landfill Gas
Hazard Assessment Guidance Note, the level of risk for deep excavations is
categorised as Medium.
6.4.11
Some manholes, inspection chambers or
voids of services/utilities would be present within the project site during the
operational phase of the proposed project.
Since access to these confined spaces will be restricted to authoriszed
persons who have awareness of LFG hazard, the risk level for these targets is
also categorised as Medium.
Summary of Qualitative Source-Pathway-Target Analysis
6.4.12
Based upon the available information,
source-pathway-target analyses have been undertaken for the different
combinations of source, pathway and target discussed above, and are summarised
in Table 6.1.
6.5.1
According to Landfill Gas Hazard Assessment Guidance Note (EPD/TR8/97), for the purpose of categorising a subject
site, the category is based on the highest level of risk nominated for any of
the potential impacts identified. For
example, a subject site with four low risks and one medium risk will fall into
the category of medium level of risk; and a site with four low risks, two
medium risks, and one high risk will fall into the category of high level of
risk. However, if four or more
different impacts arise in a particular risk category, then the overall risk
classification may be considered to be one category higher. For instance, a site with three low risks
and four medium risks will fall into the category of high level of risk.
6.5.2
Referring to Table 6.1, the
overall hazard level for the proposed project associated with Shuen Wan
Landfill is High.
6.5.3
In accordance with the EPD’s guidance
note, some precautionary measures are required to protect a proposed
development of medium or high level of risk.
Some recommendations for protection measures for the proposed project
(during the construction phase and operation phase) are provided and are
presented in the following section.
Preventive Measures During
Construction Phase
6.6.1
Special precautions should be taken in
all aspects of Works against the possible presence of landfill gas due to the
nature of the Site adjacent to Shuen Wan Landfill.
6.6.2
Landfill gas is predominately methane
and carbon dioxide, and is a potential asphyxiant. When landfill gas is mixed with air it has explosive
potential. Dependent on its actual
composition, the density of landfill gas may be less than, equal to or greater
than that of air. Therefore the
potential hazards of landfill gas should be noted in implementing the
construction works.
6.6.3
All personnel who work on the Site and
all visitors to the Site should be made aware of the possibility of ignition of
gas in the vicinity of excavations.
Safety notices (in Chinese and English) should be posted at prominent
position around the Site warning of the potential hazards. Adequate fire
extinguishing equipment and fire resistant clothing should be made available on
site.
6.6.4
Service runs within the consultation
zone (i.e. 250 m around the boundary of Shuen Wan Landfill) should be
designated as “special routes” and utilities companies should be informed of
this and should implement precautionary measures. These should include ensuring that staffs are aware of the
potential hazards of working in confined spaces such as manholes and service
chambers, and that appropriate monitoring procedures are in place to prevent
hazards due to asphyxiating atmospheres in confined spaces. Detailed guidance on entry into confined
spaces is given in Code of Practice on Safety and Health at Work in Confined
Spaces (Labour Department, Hong Kong).
6.6.5
The hazards from landfill gas should
be minimized during excavation by suitable precautionary measures including the
following:
·
Permit no smoking or burning on site
in the working area. ‘No smoking’ and ‘No
naked flames’ notices should be posted prominently on the construction site
and, if necessary, special areas designated for smoking.
·
No worker shall work alone at any time
in the confined area or any excavation trenches within the Consultation Zone
area. At least one other worker should
be available to assist with rescue if needed.
·
Construction equipment should be
equipped with a vertical exhaust at least 0.6 m above ground level and/or with spark
arrestors.
·
Electrical motors and electrical
extension cords, if utilized in the excavation area, should be explosive-proof
or intrinsically safe.
·
Welding, flame-cutting or other hot
works should only be carried out in trenches or confined spaces when controlled
by a ‘permit to work’ procedure, properly authorized by the Safety
Officer. The ‘permit to work’ procedure
should set down clearly the requirements for monitoring for methane, carbon
dioxide and oxygen throughout the period during the hot works in progress. The procedure should also require the presence
of an appropriately qualified person, in attendance outside the confined area,
who shall be responsible for reviewing the gas measurements and who should have
executive responsibility for suspending the work in the event of unacceptable
or hazardous conditions. Only those
workers who are appropriately trained and fully aware of the potentially
hazardous conditions should be permitted to carry out hot works in confined
areas.
·
Forced ventilation should be required
for workers, if in a trench deeper than 1 m.
·
During piping assembly or conduiting
construction, all valves/seals should be closed immediately after
installation. As construction
progresses, all valves/seals shall be closed as installed to prevent the
migration of gases through the pipeline/conduit. For the large diameter pipes (say >600mm diameter), pipe end
should be capped on one side during construction stage in order to prevent
migration of gases through pipes to other areas. Force ventilation should be provided before operation of the pipeline. Forced ventilation and gas monitoring should
be performed before staff entering and working in such large diameter
pipe.
·
The monitoring frequency and areas
(within the excavation trenches) to be monitored should be set down prior to
commencement of construction works either by the Safety Officer or an approved
and appropriately qualified person.
·
Routine monitoring should be carried
out in all excavations.
·
All measurements in excavations should
be made with the extended monitoring tube located not more than 10 mm from the
exposed ground surface. Monitoring should be performed properly to make sure
that the area is free of landfill gas before any man enters the area.
·
For excavations deeper than 1 m,
measurements should be carried out:
-
immediately before any worker enters
the excavation;
-
at the beginning of each half working
day (i.e. morning and afternoon) for the entire period the excavation remains
open; and
-
periodically through the working day
whilst workers are in the excavation.
·
For excavations between 300 mm and 1 m
deep, measurements should be carried out:
-
directly after the excavation has been
completed; and
-
periodically whilst the excavation
remains open.
·
Depending on the results of the measurements,
actions required should vary and should be set down by the Safety Officer or
other approved and appropriately qualified person. As a minimum these shall encompass those actions specified in Table
6.2.
Table 6.2 Actions in the Event of Gas Being Detected
in Excavations
|
Parameter
|
Measurement
|
Action
|
|
|
< 19 %
|
|
|
|
< 18 %
|
-
Stop works
-
Evacuate personnel/prohibit entry
-
Increase ventilation to restore oxygen to > 19 %
|
|
Methane
|
> 10 % LEL (i.e. > 0.5 % by volume)
|
-
Prohibit hot works
-
Ventilate to restore methane to < 10% LEL
|
|
|
|
-
Stop works
-
Evacuate personnel/prohibit entry
-
Increase ventilation to restore methane to < 10 % LEL
|
|
Carbon Dioxide
|
> 0.5 %
|
- Ventilate to
restore carbon dioxide to < 0.5%
|
|
|
> 1.5 %
|
- Stop works
- Evacuate
personnel/prohibit entry
- Increase
ventilation to restore carbon dioxide to <0.5%
|
·
The landfill gas precautionary
measures involved with excavation and piping works should be included in the
Safety Plan in the Construction Phase of the Project. The suitability of the above precautionary measures should depend
on the real situation but however, the proposed precautionary measures should
comply in accordance the Landfill Gas
Hazard Assessment Guidance Note (EPD/TR8/97).
6.6.6
Periodically during ground-works
construction (e.g. works involved welding or flame-cutting or other hot works),
the cracks on the ground level at the working area should be monitored for
methane, carbon dioxide and oxygen using appropriately calibrated portable gas
detection equipment to prevent any risk happened on site.
6.6.7
Where there are any temporary site
offices, or any other buildings which have enclosed spaces with the capacity to
accumulate landfill gas, then they should either:
·
be located on an area which has been
proven to be free of landfill gas (by survey with portable gas detectors) and
monitored manually by the Safety Officer or an approved and appropriately
qualified person to ensure that hazardous concentration of landfill gas does
not occur; or
·
be raised clear of the ground. If buildings are raised clear of the ground,
a minimum, clear separation distance (as measured from the highest point on the
ground surface to the underside of lowest floor joist) should be 500mm.
6.6.8
Such offices or buildings should be
provided with some kinds of control of gas by mechanical means e.g. forced
ventilation using fans or blowers.
Precautionary Measures During Operational Phase
6.6.9
During the operational phase, when
service voids, manholes or inspection chambers within the proposed site are
entered for maintenance, monitoring and a checklist system of safety
requirements should be performed before entry in accordance with Code of
Practice on Safety and Health at Work in Confined Spaces (Labour
Department, Hong Kong).
6.6.10
If there are For any newly built& permanent
building structures (e.g. frequently use plant rooms at the
basement of the buildings into which operators frequently enter) within the 250m
Consultation Zone after construction phase, forced
ventilation should be installed in such rooms or buildings. Gas detection
systems with audio alarm should also be installed in such area of the
development in order to monitor internal spaces inside buildings. The gas detection systems should be calibrated
and maintained at regular basis in according to the recommendation of
manufacturer’s instruction. The
operators at the development should also make sure that the gas detection
systems are always in functions during the operational phase of the development.
6.6.11
Forced ventilation should be used if
methane of more than 0.5 % (by volume) in the internal atmosphere (e.g. in
service voids, manholes, inspection chambers or rooms as mentioned above) is
detected.
6.6.12
No person should enter or remain in
any confined spaces or trenches where the carbon dioxide concentration exceeds
1.5 % (by volume).
6.6.13
Oxygen concentration should be
monitored and no person shall enter or remain in any confined spaces or
trenches where the oxygen content of air has fallen below 18 % by volume.
6.6.14
All the access to these confined
spaces would be restricted only to authorised personnel who should be aware of
the LFG hazard. No member of general
public should be permitted or allowed to access these confined spaces, manholes
or inspection chambers.
6.7
Conclusions
6.7.1
The results of the qualitative risk
assessment of landfill gas hazard posed by Shuen Wan Landfill to the proposed
project site (i.e. Tai Po Sewage Treatment Works – Stage V) suggest that the
overall level of the landfill gas hazard is High.
6.7.2
Some appropriate protection measures
have been proposed to minimise the landfill gas hazard for the proposed project
site during the construction phase and operational phase. These measures should be implemented during
the construction phase and/or operation phase of the proposed project.
6.7.3
Provided that the recommended
protection measures are implemented properly, the health and safety of the site
workers/personnel working at the proposed project site would be safeguarded and
there would be no adverse impact on the feasibility of the proposed project.