This section of the impact assessment presents a
summary of the analysis and findings of the Quantitative Risk Assessment (QRA)
study undertaken for the proposed natural gas subsea pipelines from the
Mainland to Black Point Power Station (BPPS) and two Gas Receiving Stations (GRSs) at BPPS.
This section is divided into three sub sections: Section 12.1 relates to the general
aspects of the QRA study, Section 12.2
relates to the subsea pipelines while Section
12.3 relates to the GRSs.
Further details of the analysis pertaining to each
facility are presented in the respective annexes; Annex 12A covers
the subsea pipelines, Annex 12B covers the new GRSs, while Annex 12C conducts an
assessment of the GRSs together with the existing
GRS.
An additional annex is provided to summarise all the
assumptions adopted in the QRA study (Annex 12D).
12.1
General
12.1.1
Legislation Requirement and Evaluation
Criteria
The key legislation and guidelines that are
considered relevant to the development of the proposed pipelines and GRS are as
follows:
·
Gas Safety Ordinance, Chapter 51
·
Hong Kong
Planning Standards and Guidelines (HKPSG), Chapter 12
·
Dangerous Goods Ordinance, Chapter 295
·
Environmental Impact Assessment Ordinance
(EIAO), Chapter 499
·
The
EIA Study Brief (ESB-208/2009), Section 3.4.9
There is some overlap in the requirements of the
various pieces of legislation and guidelines.
The requirement for a Quantitative Risk Assessment study is contained in
the EIAO and HKPSG. Such a study,
although not required explicitly in the Gas Safety Ordinance, is implied
in the regulations and has been an established practice for similar
installations in the SAR.
12.1.2
EIAO Technical Memorandum (EIAO-TM)
The requirement for a QRA of projects involving
storage, use and transport of dangerous goods where risk to life is a key issue
with respect to Hong Kong Government Risk Guidelines (HKRG) is specified in Section 12 of the EIAO-TM.
The relevant authority for a QRA study relating to a
natural gas pipeline and GRS is the Gas Standards Office (GSO) of the
Electrical and Mechanical Services Department (EMSD), as specified in Annex 22 of EIAO-TM.
Annex 4 of EIAO-TM specifies the
Individual Risk and Societal Risk Guidelines.
12.1.3
Risk Measures and Hong
Kong Government Risk Guidelines (HKRG)
Individual risk is the predicted increase in the
chance of fatality per year to a hypothetical individual who remains 100% of the time at a
given stationary point. The individual risk guidelines require that
the maximum level of off-site individual risk associated with a hazardous
installation should not exceed 1 in 100,000 per year i.e. 1´10-5 per year.
Societal risk expresses the risks to the whole
population. The HKRG is presented
graphically in Figure 12.1. It is expressed in terms of lines plotting the
frequency (F) of N or more deaths in the population from incidents at the
installation. Two FN risk lines are used
in the HKRG to demark “acceptable” or “unacceptable” societal risks. The intermediate region indicates the acceptability of societal risk is borderline
and should be reduced to a level which is “as low as reasonably practicable”
(ALARP). It seeks to ensure that all
practicable and cost-effective measures which can reduce risks will be
considered.
Figure 12.1 Hong Kong Government Risk Guidelines
12.1.4
Study Objectives & Methodology
The objective
of the QRA study is to assess the risk to life of the general public including
the workers of nearby plants from the proposed facilities during its
operational phase. The results of the
QRA are compared with the HKRG.
The detailed
objectives of the study are:
·
To identify all credible hazardous
scenarios associated with storage, handling and operation of the pipeline and
GRS facilities, which has potential to cause fatalities;
·
To carry out the QRA expressing
population risks in both individual and societal terms;
·
To compare the individual and societal
risks at the proposed development sites with the HKRG;
·
To identify and assess practical and
cost effective risk mitigation measures as appropriate; and
The elements of the QRA are shown schematically in Figure 12.2.
An overview of the methodology employed is provided here to briefly introduce the study approach,
while the details are included in the respective sections/ annexes.
Relevant data on the proposed facilities such as
their preliminary layout drawings and design basis as well as population data in the vicinity were collected and
reviewed.
A Hazard Identification (HAZID) Study was conducted to identify all hazards, both generic and site
specific. A review of literature and
accident databases was also undertaken (Annex
12A.4 and Annex 12B.4). These formed the basis for identifying all
hazardous scenarios for the QRA Study.
The frequencies, or the likelihood, of the various outcomes
resulting from a natural gas release
scenario were derived from historical databases and, where necessary, these
were modified to take into account local factors (Annex 12A.5 and Annex12B.5).
For all identified hazards assessed as having a
frequency of less than 10-9 per year, the frequency assessment will
be documented but no quantification of consequences will be performed.
For hazards with frequencies greater than 10-9
per year, the consequences of each
release were modelled.
Hydrocarbon releases have been modelled using the PHAST consequence modelling package developed by Det
Norske Veritas, Inc. (DNV)
The consequence and frequency data were subsequently
combined using ERM’s proprietary software RiskplotTM
to produce the required risk calculations.
Finally, the results from the risk assessment were
compared with the HKRG and found to be acceptable. No mitigation measures are therefore
proposed.
Figure 12.2 Schematic
of QRA Process
12.2
Pipeline
The proposed subsea
pipelines will transport compressed natural gas from the Mainland to CAPCO’s Black Point Power Station. Two pipelines are proposed and only 5 km of
the pipeline alignment lies within Hong Kong SAR waters. It is this 5 km section of the route which is
considered in this assessment. Details
of the pipeline are preliminary at the time of writing but will likely consist
of two pipes of between 32” and 42” diameter.
These may be located in two separate trenches constructed about 2 years
at different times and located 100 m apart.
This section of the report presents a summary of the QRA study for the
subsea pipelines while Annex 12A gives further
details.
Whilst the construction of the first pipeline is
expected to be in 2011, the construction of the second pipeline is expected to
be in 2014. The additional risks arising
from construction activities in 2014 (when the first pipeline is operational)
are assessed but not found to be significant.
Results are therefore presented for a single operational pipeline in 2011, and for 2 operational pipelines in the future year
2021. The assessment also takes into
account the variation of marine traffic between 2011 and 2021.
12.2.1
Pipeline and Marine Data
Pipeline Route
The proposed pipelines take a subsea route from the
Mainland China to Black Point Power Station (Figure 12.3). The pipelines
will cross the Urmston Road waterway (not a designated channel), and the Hong
Kong section is only 5 km in length and passes about 100 – 200 m north of the
existing Yacheng pipeline.
The pipelines will be buried to between 1.5 and about
5 m below the seabed with rock armour/ natural fill protection (Figure 12.4). Type 1 protection is used on the shore
approach to Black Point and provides 1.5 m of rock armour backfill. This provides protection for anchors up to 3
tonnes, essentially protecting against anchors from all ships below about
10,000 dwt. Trench type 2 is used in
shallow water areas away from the busy marine fairways. Trench type 2 consists of post-trenching with
about 5 m of armour rock and natural backfill.
This is designed for protection from 3 - 5 tonne anchors (i.e. from all
ships below about 10,000 dwt) and any future dredging work. The Urmston
Road waterway will have type 3 trenches consisting
of 3 m of rock armour backfill. Type 3
is designed to protect against 19 tonne anchors. This covers the full range of ships currently
operating in Hong Kong and also those expected
in future.
Marine Traffic
A marine traffic assessment [1] studied the marine traffic in the vicinity of the
pipeline using radar tracks. Based on
the vessel speed and apparent size from the radar returns, vessels are divided
into six categories (Table 12.1). The number of ships is also determined from
the density of radar tracks. Although
some interpretation of the data was required, the marine assessment provided
the necessary information to determine the marine traffic volume crossing
different sections of the pipeline.
Figure 12.3 Proposed
Pipeline Alignment
Figure 12.4 Pipeline
Trench Types
Table 12.1 Vessel
Classes Adopted for Assessment
It was
also necessary to make some assumptions regarding the population of each class
of vessel. These are given in Table 12.2.
Table 12.2 Vessel
Population
|
Class
|
Population
|
|
Fishing vessels
Rivertrade
coastal vessels
Ocean-going vessels
Fast launches
Fast ferries
Other
|
5
5
21
5
450/350/280/175/105/35*
5
|
|
* A distribution was assumed for the fast
ferry population to reflect the occupancy at different time periods. This distribution is conservative when
compared to the average load factor published by the Marine Department.
|
Segmentation of the Route
Based on considerations of the marine traffic data
and the level of rock armour protection proposed for the pipeline, the pipeline
route was divided into 4 sections for analysis (Table 12.3, Figure 12.3).
Table 12.3 Pipeline
Segmentation
|
|
Section
|
Kilometre Post
|
Section Length (km)
|
Typ. Water depth (m)
|
Trench type
|
|
From
|
To
|
|
4
|
Boundary Section
|
0
|
0.73
|
0.73
|
2-20
|
2
|
|
3
|
Urmston Road
|
0.73
|
2.52
|
1.79
|
20
|
3
|
|
2
|
Black Point West
|
2.52
|
4.78
|
2.26
|
5
|
2
|
|
1
|
Black Point Approach
|
4.78
|
4.89
|
0.11
|
2
|
1
|
The marine traffic used for this study, interpreted
from vessel radar tracks [1], is as summarised in Table 12.4. Similar traffic
tables were constructed for the future 2021 scenarios (Tables 12.5) by incorporating growth factors for the expected
increase in traffic [1] These data
take into account developments such as the Tonggu
Waterway, which tends to shift ocean-going vessels away from Urmston Road and
into Tonggu.
Table 12.4 Traffic
Volume Assumed for Base Case 2011
|
|
Traffic volume (ships per day)
|
|
|
Section
|
Fishing
|
River-trade
|
Ocean-going
|
Fast Launch
|
Fast ferry
|
Other
|
Total
|
|
4
|
Boundary Section
|
21
|
3
|
0
|
24
|
30
|
8
|
86
|
|
3
|
Urmston Road
|
250
|
265
|
81
|
118
|
150
|
5
|
869
|
|
2
|
Black Point West
|
12
|
16
|
0
|
5
|
8
|
2
|
43
|
|
1
|
Black Point Approach
|
1
|
0
|
0
|
0
|
0
|
0
|
1
|
|
|
Total
|
284
|
284
|
81
|
147
|
188
|
15
|
999
|
|
|
|
|
|
|
|
|
|
|
Table 12.5 Traffic
Volume Assumed for Future Year 2021
|
|
Traffic volume (ships per day)
|
|
|
Section
|
Fishing
|
River-trade
|
Ocean-going*
|
Fast Launch
|
Fast ferry
|
Other
|
Total
|
|
4
|
Boundary Section
|
22
|
5
|
0
|
26
|
35
|
9
|
97
|
|
3
|
Urmston Road
|
262
|
290
|
81
|
129
|
177
|
6
|
945
|
|
2
|
Black Point West
|
12
|
17
|
0
|
6
|
9
|
2
|
46
|
|
1
|
Black Point Approach
|
1
|
0
|
0
|
0
|
0
|
0
|
1
|
|
|
Total
|
297
|
312
|
81
|
161
|
221
|
17
|
1089
|
|
|
|
|
|
|
|
|
|
|
* The volume of ocean-going vessels through Urmston Road is
expected to decrease due to the development of the Tonggu
Waterway. However, as a conservative approach, the analysis assumes that
ocean-going vessel traffic for 2021 and 2011 remain constant at 2003 levels.
Pipeline Protection
Varying levels of rock armour protection are proposed
for each section of the pipeline based on earlier studies [2]. These levels
of rock armour protection are assumed in the base case analysis as well as
future traffic scenarios presented in this report.
12.2.2
Methodology
Key elements of the risk assessment methodology are
described in the following sections.
Hazard Identification
Hazards were identified by reviewing worldwide
databases [5], [6] and reports on incidents related to subsea pipelines [7], [8]. A HAZID
(Hazard Identification) workshop was also conducted for the proposed pipeline
to identify any route/site specific issues.
The details of the hazard identification process are presented in Annex
12A.
The main hazard associated with a subsea pipeline is
loss of containment resulting in gas release which could be ignited by a
passing marine vessel. A loss of
containment could occur from:
·
Failures
due to external impact (such as anchor drop/drag);
·
Spontaneous
failures from corrosion and material/weld defects; and
·
Natural
hazards (such as subsidence, seismic event).
Frequency Estimation
Frequency assessment is the estimation of the
likelihood of occurrence of each scenario based on the hazard identification
exercise. The approach adopted here for
estimating frequency of pipeline failure is to apply worldwide historical data,
with appropriate modifications for the specific pipeline environment.
The database that is most comprehensive and relevant
is PARLOC 2001 [3]. This covers
300,000 km-years of subsea pipeline experience dating from the 1960s to
2000. This database provides failure
frequencies for different causes such as corrosion, material defects, external
impact etc. It also provides a breakdown
by pipe diameter, location and contents of pipeline.
To validate this approach, particularly for
anchor/impact damage where the specific marine traffic environment is more
relevant, alternative calculations were performed for comparison. These were based on marine incident rates in Hong Kong waters, from which the likelihood of emergency
anchoring events were estimated. This
alternate approach was found to give similar failure frequencies to that
derived from the PARLOC data. The
frequencies used in the analysis are summarised in Table 12.6 while details are presented in Annex 12A.
The CAPCO pipelines will have rock armour protection
along its whole length. To allow for this,
protection factors are incorporated into the analysis. Trench types 1 and 2 are designed to protect
against 3 - 5 tonne anchors. They are
assumed to be 99% effective. They are
also assumed to provide some protection (50%) against larger anchors. Trench type 3 is designed to protect against
19 tonne anchors, covering all ships currently operating in Hong
Kong and those expected in the future. This trench type was assumed to be 99%
effective for large anchors and provide even greater protection (99.9%) against
smaller anchors, i.e. below 2 tonnes (see Table
12.6). Note that the rock armour
design will be finalised during the engineering stage based on these
performance considerations. The above
assumptions are therefore conservative.
The frequencies used in the analysis are summarised
in Table 12.6 while details are
presented in Annex 12A. The
probability of damage to the pipeline leading to a gas release is estimated as
0.0005 for the 5 km section during the lifetime of the facility, assumed as 25
years.
Table 12.6 Summary
of Pipeline Failure Frequencies used in this Study
|
Pipeline
section
|
Trench type
|
Corrosion /defects (/km/year)
|
Anchor/Impact
|
Others
/km/year
|
Total*
/km/year
|
|
Frequency (/km/year)
|
Protection factor (%)
|
|
anchor<2
|
Anchor>2
|
|
Boundary Section
|
2
|
1.18´10-6
|
1´10-4
|
99
|
50
|
1.34´10-6
|
3.5´10-6
|
|
Urmston
Road
|
3
|
1.18´10-6
|
8.6´10-4
|
99.9
|
99
|
1.34´10-6
|
4.1´10-6
|
|
Black Point West
|
2
|
1.18´10-6
|
1´10-4
|
99
|
50
|
1.34´10-6
|
3.5´10-6
|
|
Black Point Approach
|
1
|
1.18´10-6
|
1.37´10-5
|
99
|
50
|
1.34´10-6
|
2.7´10-6
|
* The calculation of total failure
frequency takes into account the size distribution of ships (based on 2011 marine
traffic) and the protection factors for anchors
Scenario Development
The outcome of a hazard is predicted using Event Tree
Analysis (ETA) to investigate the way initiating events could develop. This considers the cause of failure, the hole size distribution, the likelihood that a marine vessel
will be in the area and the probability that the gas will be ignited. Historical data is used where appropriate for
the hole size distribution and ignition
probability. The probability that a ship
will pass through the flammable plume is calculated based on the size of the
plume (obtained from dispersion modelling) and the marine traffic density.
Consequence Analysis
In the event of loss of containment in a subsea
pipeline, the gas will release as a jet but is expected to lose momentum and
bubble to the sea surface and disperse into the atmosphere as a buoyant
gas. The dispersing plume may encounter
an ignition source, say from a passing vessel, while within its flammable
limits, leading to a flash fire, which will propagate through the gas
cloud.
The flash fire could cause injury to personnel on
marine vessels. It may also cause
secondary fires on the vessel.
If a vessel passes close to the ‘release area’ (where
bubbles of gas break through the sea surface), the vessel may be caught in the
ensuing fire with more severe consequences.
100% fatality is assumed for this scenario. Once a fire has ignited, it is presumed that
no further ships will be involved because the fire will be visible and other
ships can take action to avoid the area.
In other words, it is assumed that at most, only one ship will be
affected.
12.2.3
Risk Results
Individual Risk
The individual risk (IR) is given in Table 12.7.
The highest risks come from
Urmston Road
where the marine traffic is the highest.
The individual risk for all sections, however, is less than 1´10-5 per year. Comparing the case of two operational
pipelines with just one pipeline, the risk is essentially the same along most
of the route since the 100m separation of the pipelines exceeds most of the
hazard distances, i.e. there is little overlap of the risk contours. However, on the shore approach to Black
Point, the pipeline alignments converge.
The worst case IR is therefore about double the risk from a single
pipeline, but this is still much below the 10-5 per year
criterion.
Table 12.7 Individual
Risk Results (per year)
|
Section
|
2011
1 pipeline
|
2021
2 pipelines
|
|
4
|
Boundary Section
|
9.2´10-8
|
1.9´10-7
|
|
3
|
Urmston
Road
|
2.1´10-7
|
4.3´10-7
|
|
2
|
Black Point West
|
6.6´10-8
|
1.3´10-7
|
|
1
|
Black Point Approach
|
9.9´10-9
|
2.0´10-8
|
Societal Risk Results
Societal risks are presented in terms of
per km to give a uniform basis for comparison between the various
sections. Again, the highest risks are
associated with Urmston Road
(Table 12.8). The total Potential
Loss of Life (PLL), or equivalent annual fatality, for the whole length of
pipeline ranges from 2.0´10-5 per year for a single
pipeline in 2011 to 4.2´10-5 per year for two pipelines
in operation in 2021. Marine population
differences between 2011 and 2021 are only marginal and hence the societal risk
from two pipelines is essentially double that from a single pipeline.
Table 12.8 Potential
Loss of Life Results (per km-year)
|
Section
|
2011
1 pipeline
|
2021
2 pipelines
|
|
4
|
Boundary Section
|
5.4´10-6
|
1.1´10-5
|
|
3
|
Urmston
Road
|
5.8´10-6
|
1.3´10-5
|
|
2
|
Black Point West
|
2.5´10-6
|
5.1´10-6
|
|
1
|
Black Point Approach
|
5.0´10-8
|
1.1´10-7
|
|
|
Total
|
2.0´10-5
|
4.2´10-5
|
The FN curves for each section are presented in Figures 12.5 and 12.6. These are also
expressed on a per km basis for comparison with the HKRG.
The FN curves also show that the highest
risks are associated with Urmston
Road.
Despite the high level of pipeline protection, the marine traffic volume
is very high along this section. The
approach to Black Point shows the lowest risks due to the very low marine
activity in this area.
The FN curves for all sections of the
pipeline lie within the Acceptable Region.
Figure 12.5 FN
Curve for Single Pipeline in 2011
Figure 12.6 FN
Curve for Two Pipelines in 2021
12.2.4
Conclusions of Pipeline QRA Study
A QRA study for the proposed CAPCO pipelines was conducted. The study considered the loss of containment
that may occur due to all possible events, of which corrosion, material defects
and third party damage from ship anchor drops/drags were identified as the major
risk contributors. Based on a review of
the hazards, the marine traffic density and pipeline rock armour protection,
the 5 km pipelines within Hong Kong SAR waters was divided into four sections
for assessment. Risks have been
presented for each section on a per-km basis to provide a uniform basis for
comparison.
The base case calculation used marine traffic data
for 2011 and levels of rock armour protection for each section as proposed in
the pipeline design. A future year 2021
was also assessed.
The calculated levels of risk were compared with the
HK EIAO and the following conclusions were drawn:
·
The
FN curves for all sections of the pipeline lie within the Acceptable Region.
·
The
highest risks are generally associated with Urmston Road where the marine traffic has
the highest density.
·
IR for
all sections are predicted to be less than the 1´10-5 per year as per HK EIAO
criterion.
It is concluded that for all sections, the risks are
acceptable per HK EIAO and no further
mitigation measures are warranted for the pipelines.
12.3
Gas Receiving Stations
(GRSs)
The proposed pipelines from the Mainland China will
terminate at two gas receiving stations (GRSs) at
BPPS. One will be located adjacent to
the existing GRS (co-located GRS), the second will be
located on reclaimed land to the north of the BPPS site (GRS on
reclamation). The two GRSs are not expected to be constructed concurrently. The co-located GRS will be constructed in
2011 (i.e. First Phase construction) while the construction of the GRS on
reclamation is expected to commence in 2014.
Therefore, the following 3 cases were considered in the QRA:
·
“Scenario
2011” considers the risks from the co-located GRS operating only;
·
“Scenario
2014” considers the risks from the co-located GRS operating during construction
of the GRS on reclamation; and
·
“Scenario
2021” considers the risks from both co-located GRS and GRS on reclamation
operating at the same time.
This section provides the QRA results for the GRSs.
12.3.1
Methodology
Details of the QRA analysis are provided in Annex
12B. A brief summary is provided
here.
Each GRS will contain a pig receiver, inlet
filter-separators, metering, pre-heaters and a pressure letdown station. An emergency isolation valve will be provided
at the inlet to the station and also for individual section isolation in the event
of any emergency. Process flow diagrams
are included in Annex 12B.
The methodology for the QRA includes the
identification of surrounding population, identification of hazards, frequency
analysis, consequence analysis and risk summation.
Site Details
The BPPS is located in a remote area with very low
levels of surrounding population. For
the purpose of this QRA, the site is considered to include the new GRS
facilities and the reclaimed land. There
is no land based population that may be impacted by any gas releases from the
GRS facilities. The main population that
may be impacted is the marine population.
The effects of gas releases from the facility depend
on weather conditions. Meteorological conditions from the most recent 5 years
of data from Sha Chau
Weather Station, obtained from the Hong Kong Observatory, were used in the
analysis.
Scenario Definition
The identification of hazards was based on a review
of past incidents at similar facilities worldwide and a HAZID workshop. The GRS facilities contain natural gas under
high pressure, the main hazards of which are associated with the flammable
properties of natural gas and the possibility of leaks followed by
ignition. This may result in jet fires,
fireball and flash fires.
Once the main hazards are understood, the facility is
divided into sub-sections for further analysis.
Nine sections were chosen for the current analysis, ranging from pig
receiving facilities to the downstream distribution headers. A range of leak
sizes, from small leaks to full ruptures, are considered in the analysis.
Frequency Analysis
The frequency of leaks and ruptures from each section
of the GRS was estimated from published generic failure rates [4]. Event Tree
Analysis is then used to model the development of releases into the final
outcomes such as jet fires and flash fires.
Special consideration was given to pigging operations which may lead to
releases caused by human error.
Consequence Analysis
The PHAST suite of models is used to determine the
hazard footprint for each leak scenario. This includes the modelling of
discharge rates, dispersion and thermal radiation for jet fires, flash fires
and fireballs.
12.3.2
Results
Individual Risk Results
The individual risk (IR) contours
associated with the co-located GRS with 2011 population are shown in Figure 12.7. The maximum risk is less than 1´10-5 per year at all locations and hence meets the HKRG
requirements. The IR for the
construction phase in 2014 is the same since both cases have only one GRS
operating and IR is independent of population.
IR for the future
year 2021 is shown in Figure 12.8. With two GRSs
operational, the IR has increased but remains below 10-5 per year at
the site boundary and hence meets the HKRG requirements.
Figure 12.7 Individual
Risk Contours (2011 and 2014)
Individual Risk Contour (2011)
Individual Risk Contour (2014)
|
10-6
per year
Figure 12.8 Individual
Risk Contours (2021)
10-6
per year
Societal Risk Results
The potential loss of life for the gas receiving
station is given in Tables 12.9 to 12.11.
Values are very low for 2011, 2014 and 2021 given the low offsite
population in the vicinity. The total
PLL, respectively, is 1.49´10-8 per year for year 2011,
1.49´10-8 per year for year 2014, and 1.52´10-7 per year for year 2021, or
equivalently, estimated one fatality every 10 million years.
It can be
observed that the risks are higher for 2021 compared to 2011. This is due to two GRSs
in operation instead of one. Also, the
second GRS on reclaimed land is closer to the only affected population, the marine
population.
Table 12.9 Potential
Loss of Life (Year 2011 and 2014)
|
Section
|
|
PLL (per year)
|
|
Piping from PRS to mixing
station
|
G08
|
4.27´10-9
|
28.5%
|
|
Heater Piping
|
G06
|
3.12´10-9
|
20.8%
|
|
Pig receiver
|
G09
|
3.03´10-9
|
20.3%
|
|
Piping from metering
station to heaters
|
G05
|
2.25´10-9
|
15.1%
|
|
Above ground gas piping
from offshore pipeline to pig receiver
|
G01
|
1.33´10-9
|
8.9%
|
|
Filter & inlet/outlet
piping
|
G03
|
9.51´10-10
|
6.4%
|
|
Total
|
|
1.49´10-8
|
|
Table 12.10 Potential
Loss of Life (Year 2021)
|
Section
|
|
PLL (per year)
|
|
Heater Piping
|
G06_B
|
3.94´10-8
|
25.9%
|
|
Piping from metering
station to heaters
|
G05_B
|
3.03´10-8
|
19.9%
|
|
Piping from PRS to mixing
station
|
G07_B
|
1.43´10-8
|
9.4%
|
|
Above ground gas piping
from offshore pipeline to pig receiver
|
G01_B
|
1.39´10-8
|
9.1%
|
|
Piping from PRS to mixing
station
|
G08_B
|
8.86´10-9
|
5.8%
|
|
Pig receiver
|
G09_B
|
8.47´10-9
|
5.6%
|
|
Filter & inlet/outlet
piping
|
G03_B
|
7.86´10-9
|
5.2%
|
|
Piping from PRS to mixing
station
|
G08_B
|
7.73´10-9
|
5.1%
|
|
Piping from PRS to mixing
station
|
G08_A
|
3.72´10-9
|
2.4%
|
|
Others
|
|
1.76´10-8
|
|
|
Total
|
|
1.52´10-7
|
|
Figure 12.9 shows the FN Curves for the GRS at the
BPPS. It can be seen that the societal risk
for the GRS is very low and within the Acceptable
Region as per HK EIA Ordinance. The
risk increases slightly during the construction phase due to increase in
surrounding population (marine only), but the risks are still low and in the
acceptable region.
Figure 12.9 FN
Curves for GRS
The FN curve presented in Figure 12.9 presents the results for the year 2014 when one GRS is
in operation and the other one in construction.
The analysis shows that risks to the offsite population will remain low
and within acceptable region.
Risks Associated with the Existing GRS
As per the requirements set out in the EIA Study
Brief (ESB-208/2009) the risks arising from the two new GRSs
were assessed and found acceptable as compared to the criteria (as depicted in Figure 12.9). In addition to this, a quantitative
assessment was conducted considering the hazards associated with the existing
GRS. A summary of this assessment is
provided in the following paragraphs while the detailed assessment is presented
in Annex 12C. It
should be noted that such an assessment is additional to the requirements by
the EIA Study brief of the project.
Individual risks associated with the facilities,
including the existing GRS and two new GRSs, meet the
HKRG.
Societal risks associated with the operational phases
of the project (including all 3 GRSs) are low and lie
in the acceptable region of the FN curves.
Societal risks increase slightly during the
construction phase due to slight increase in offsite population, which are at similar separation distances to the new GRSs.
Recommendations are made in accordance with best practice to mitigate
these construction phase risks:
·
The
most hazardous maintenance operations on the existing GRS will be avoided
during the construction of the GRS on reclamation.
·
Procedures
for evacuation of construction workers will be in place in case of particularly
hazardous operations on existing GRS and co-located GRS.
·
Specific
emergency procedures will be put into place for the evacuation of construction
workers.
·
Additional
gas detectors along the boundary or gas and fire alarms for the detection from
the GRSs in operation for escape and evacuation of
construction workers will be considered.
·
The
construction of a temporary steel wall or other appropriate barrier between the
existing GRS and the GRS on reclamation will be considered to prevent gas
spreading towards the construction site in case of a gas leak in the existing
GRS. This will also prevent the gas coming
in contact with the ignition sources at the construction site, limit exposure
of personnel to any direct flame from the existing GRS and provide time for
construction personnel to evacuate the site.
These same recommendations may also be considered for
the construction of the co-located GRS.
Even though the separation distance to the existing GRS is greater,
these recommendations would provide additional mitigation.
·
During
the construction of the co-located GRS and the GRS on reclamation, risks to the
existing gas pipeline and the existing GRS could increase due to inadvertent
damage caused by construction activity in the vicinity of existing
installation. These risks will be
managed by special procedures, for construction, and
monitoring/supervision. This will
include for example, a Job Safety Study conducted to assess the potential risk
and failure modes of such construction operations and special precautions will
be included in the procedures.
12.3.3
Conclusions of GRS QRA Study
A QRA study for the proposed CAPCO GRSs was conducted.
Risks associated with the operational and construction phases of the
facility are calculated to be low and within the HK EIAO criteria. No further mitigation measures are warranted
for the GRSs.
In addition to the requirements set out in the EIA
study Brief of the project, a quantitative assessment was performed in Annex
12C considering the aggregated risks from the new and the existing GRSs. The results
show that the risks are acceptable during both phases of construction. Mitigation measures, in accordance with best
practices, were proposed and detailed in Annex 12C.
12.4
References
[1]
BMT Asia Pacific Ltd, Marine Impact
Assessment for Black Point & Sokos islands LNG Receiving Terminal &
Associated Facilities, Pipeline Issues, Working Paper #3, Issue 5, Apr 2006.
[2]
ERM-Hong Kong Ltd., Liquefied Natural Gas (LNG) Receiving
Terminal and Associated Facilities EIA Report, October 2006.
[3]
PARLOC 2001: The Update of Loss of
Containment Data for Offshore Pipelines, 5th Edition, Health &
Safety Executive, 2003
[4]
Hawksley, J.L.,
Some Social, Technical and Economic Aspects of the Risks of Large Plants,
CHEMRAWN III, 1984
[5]
UK AEA, Major Hazard Incident Database
(MHIDAS) Silver Platter.
[6]
Institution of Chemical Engineers UK, The Accident Database, Version 2.01
[7]
National Transportation Safety Board,
Natural gas Pipeline Rupture and Fire During Dredging of Tiger Pass, Lousiana, October 23, 1998.
[8]
National Research Council, Improving Safety
of Marine Pipelines, 1994.
