Parts of the proposed NDAs (KTN and FLN) are located within the
A previous Hazard to Life Assessment was conducted on SSWTW in 1991 [9-1] and reassessed in
2001 [9-2] due to upgrade on
chlorine dosing facilities. This hazard assessment (HA) study follows the same
methodology as the previous Reassessment study [9-2].
This chapter aims to present the Hazard to Life Assessment for SSWTW and
to demonstrate the risk imposed by SSWTW to the proposed NDAs development
complies with the requirement of the Hong Kong Risk Guidelines in Annex 4 of
the EIAO-TM [9-3].
This HA aims to achieve the objectives specified in the Section 2.1 (iv)
and (vi) of the EIA Study Brief (No. ESB-176/2008) [9-4]. The Study Brief
has required assessment of risks from chlorine and explosives where necessary.
Technical requirements in the Study Brief are reproduced below:
|
|
Hazard to Life |
|
|
The Applicant
shall follow the criteria for evaluating hazard to life as stated in Annexes
4 and 22 of the TM. |
|
|
The Applicant
shall carry out hazard assessment to evaluate risks due to transport, storage
and use of chlorine associated with the operations at Sheung Shui Water
Treatment Works during the implementation of the Project. The hazard
assessment shall include the following: (i) Identify
hazardous scenarios associated with the transport, storage and use of
chlorine and then determine a set of relevant scenarios to be included in a
Quantitative Risk Assessment (QRA); (ii) Execute a QRA
of the set of hazardous scenarios determined in (i), expressing population
risks in both individual and societal terms; (iii) Compare
individual and societal risks with the criteria for evaluating hazard to life
stipulated in Annex 4 of the TM; and (iv) Identify and
assess practicable and cost-effective risk mitigation measures. The methodology of
hazard assessment shall be agreed and approved by the Director. |
|
|
If there is use of
explosives for construction activities and storage or blasting location is in
close proximity to populated areas and / or Potentially Hazardous
Installation site(s) (such as Sheung Shui Water Treatment Works), the
Applicant shall carry out hazard assessment as follows: (i) Identify
hazardous scenarios associated with the transport, storage and use of
explosives and then determine a set of relevant scenarios to be included in a
QRA; (ii) Execute a QRA
of the set of hazardous scenarios determined in (i), expressing population
risks in both individual and societal terms; (iii) Compare
individual and societal risks with the criteria for evaluating hazard to life
stipulated in Annex 4 of the TM; and (iv) Identify and
assess practicable and cost-effective risk mitigation measures. The methodology of
hazard assessment shall be agreed and approved by the Director. |
According to the latest engineering design, there is no need to use
explosives in the construction activities. Hence, this HA will only consider
the hazards posed by the storage, use and transport of chlorine at SSWTW.
This study is based on the results of the previous reassessment study of
SSWTW [9-2] and therefore
similar in scope. The input data for the risk modelling will be updated to
reflect the changes since then, especially the projected population in the
surrounding area of SSWTW.
The geographical scope is defined as the population areas within the CZ.
However, where the hazard range of certain chlorine release events (e.g.
collapse of the chlorine store caused by earthquake) reaches areas outside the
CZ, those areas will be included. It should be noted that only parts of the NDAs
(KTN and FLN) would be affected by the accidental chlorine release, which will
be considered in this assessment.
9.3.1 Overview
The overall approach of the assessment is illustrated in Figure
9.2.
As discussed in Section 9.2, the Reassessment Study [9-2] conducted in 2001 will
be adopted as the basis for the current HA, and its methodology will be closely
followed.
Other risk assessment studies of similar nature or facility in Hong Kong
will be reviewed [9-5][9-6], so as to maintain
consistency with similar studies in
Hazard scenarios adopted in the Reassessment Study will be confirmed
independently using review of historical incidents as instructed by the Court
of Final Appeal (CFA) in [9-7]. The Major Hazard
Incident Data Services (MHIDAS) accident database will be reviewed in this HA.
With regard to the assessment of impact of chlorine release on the
transient population (on road and railways), the approach as documented in the
HSE study “The implication of major hazard sites in close proximity to major
transport route” [9-8] will be adopted. As
for other populations, consideration is given for the possibility of escape
from the toxic cloud, protection of the buildings, and higher fatality rate of
sensitive groups. This methodology was also adopted in the 2001 Reassessment
Study.
The major steps of the HA are:
a) Hazard Identification: Identify hazard scenarios associated with
the transport, storage and use of chlorine and then determine a set of relevant
scenarios to be included in a QRA.
b) Consequence Analysis: Assess the consequences and impact to the
surrounding population.
c) Frequency Estimation: Estimate the likelihood of occurrence of the
identified hazard scenarios.
d) Risk Summation and Assessment: Evaluate the risk level, in terms of
individual risk and societal risk. The risk will be compared with the criteria
stipulated in Annex 4 of the TM to determine their acceptability, as described
in Section 9.3.2 below.
e) Identification of Mitigation Measures: If the overall risk exceeds
the “Acceptable” level and resides in the “ALARP” region, practicable and
cost-effective risk mitigation measures will be identified. The risk of
mitigated cases will then be reassessed to determine the level of risk
reduction.
This assessment makes use
of a risk summation model, RISKSUM, to assess the level of risk. The tool is
developed by BMT Asia Pacific Ltd. A calibration exercise has been conducted
and confirmed outputs from RISKSUM are consistent with previous results
generated by GISRisk model used in the 2001 Reassessment Study.
9.3.2 Risk Acceptability Criteria
As stipulated in Annex 4 of the EIAO-TM [9-3], the risk
guidelines comprise two criteria shown as follows:
Individual Risk: The
maximum level of off-site individual risk should not exceed 1 x 10-5
per year, i.e.
Societal Risk: It can
be presented graphically as in Figure 9.3. The Societal Risk
Guideline is expressed in terms of lines plotting the frequency (F) of N or
more fatalities in the population from accidents at the facility of concern. In
the figure, ALARP means As Low As Reasonably Practicable. Risk in this region
should be reduced to As Low As Reasonably Practicable by implementation of
practicable and cost-effective risk mitigation measures.
Population in the vicinity of SSWTW is expected to increase with the
NDAs development. Based on the NDAs implementation plan (Figure 9.4), site formation
and construction at KTN and FLN areas will commence at Year 2016, and the first
population intake is scheduled at Year 2023. Site
development will complete at Year 2030 (early finish) for KTN and FLN
areas near SSWTW, which may be delayed
to Year 2031 (late finish) considering potential project uncertainties. This
assessment conservatively considers late finish of the project implementation.
Therefore, it is anticipated that KTN/FLN areas and related roads near SSWTW
will be fully occupied at Year 2032 after completion of the new development. It
is therefore proposed to adopt Year 2032 as the assessment year for the
ultimate NDA development.
As shown in Figure 9.5, major construction work
within
A total of six cases are considered in this HA to demonstrate the
changes in risk level caused by the NDAs development:
9.4.1 Construction Stage (3 Cases)
· Case 1 (2023 no NDA): Surrounding population projected at 2023 (no NDAs development). It aims to obtain the background risk level without NDAs development. Population in the vicinity of SSWTW will be updated and projected to the future year.
· Case 2 (2023 NDA only): Forecast population at NDAs at 2023 only. The purpose is to investigate the additional risk caused by the NDAs development.
·
Case 3 (2023 NDA + Surrounding): Surrounding population projected at 2023
+ forecast population at NDAs at 2023. This case considers the overall risk
level in the future with the NDAs development.
9.4.2 Operation Stage (3 Cases)
·
Case 4 (2032 no NDA): Surrounding population projected at 2032 (no NDAs
development). It aims to obtain the background risk level without NDAs
development. Population in the vicinity of SSWTW will be updated and projected
to the future year.
·
Case 5 (2032 NDA only): Forecast population at NDAs at 2032 only. The
purpose is to investigate the additional risk caused by the NDAs development.
·
Case 6 (2032 NDA + Surrounding): Surrounding population projected at 2032
+ forecast population at NDAs at 2032. This case considers the overall risk
level in the future with the NDAs development.
9.5.1 Location
SSWTW is located at 10 mPD and
9.5.2 Operations
9.5.2.1 Delivery, Storage and Handling of Chlorine
Chlorine is delivered to SSWTW in batches of up to 6 x 1 tonne drums.
Unloading takes place inside the chlorine store with the doors closed in a
designated truck unloading bay. The movement of drums within the storage area
and unloading bay is carried out using an electrically-operated overhead
travelling crane with purpose-built lifting beam. Prior to usage, the drums are
stored on cradles within the chlorine storage area. Table 9.1 provides the basic plant
operating data for SSWTW.
Table
9.1 - Plant Operating Data for SSWTW
|
Items |
Units |
Quantity |
|
|
Type of container in use |
- |
1 tonne |
|
|
|
|
|
|
|
Situation
in |
2011 |
1996 |
|
|
Design capacity of plant |
Mld |
200 |
200 |
|
Plant throughput (average) |
Mld |
134 |
115 |
|
Chlorine usage (average) |
tonnes per year |
108 |
514 |
|
Chlorine stock level (average) |
tonnes |
41 |
35 |
|
Chlorine storage capacity (including duty and
standby containers) |
tonnes |
56 |
56 |
|
Number of draw-off units |
- |
2 |
2 |
|
|
|
|
|
|
Ultimate Loading of
Chlorine Plant |
|
|
|
|
Chlorine dosage (average) |
mg/l |
2.2 |
15 |
|
Estimated chlorine usage |
tonnes per year |
161 |
1095 |
|
Chlorine storage capacity (including duty and
standby containers) |
tonnes |
112 |
112 |
|
Number of draw-off units |
- |
2 |
2 |
|
|
|
|
|
|
General |
|
|
|
|
Chlorine container lifting device |
- |
EOTC(1) |
EOTC(1) |
|
Scrubber capacity |
tonnes chlorine |
1 |
1 |
|
Distance travelled by chlorine truck along site
access road |
km |
0.2 |
0.2 |
Notes:
(1) EOTC – Electrical Overhead Travelling
Crane.
9.5.2.2 Chlorination System
The draw-off units comprise pairs of drums, one drum on duty, the other
serving as standby. The number of drums on line is subject to the raw water
quality. Changeover panels automatically change the draw-off from duty to
standby when the draw-off pressure falls below a preset level. The changeover
is achieved by electrically actuated isolating valves provided for each drum.
Liquid chlorine is drawn from the 1 tonne drums and is passed to the
evaporators for conversion into the gaseous state. The gaseous chlorine passes
through the chlorinators and dissolves in water at ejectors to form a
chlorinated water solution for feeding into the bulk water stream during the
treatment process.
The chlorinators are of vacuum venturi type and thus the section of line
between the regulator and the chlorinator is at negative pressure. Double non
return valves are provided within the chlorinator units.
9.5.2.3 Ventilation System
The chlorine drum storage/evaporator area and chlorinator rooms are
normally ventilated via a supply of fresh air at high level and extracted at
low level. On detection of chlorine levels above 3 ppm there are visual and
audible alarms and the ventilation extract fans stop.
9.5.2.4 Chlorine Scrubbing System
An emergency chlorine scrubbing system is installed to remove any leaked
chlorine in the chlorine handling and storage areas. The system is a packed
tower utilising sodium hydroxide as the neutralising agent. The plant and
equipment are installed in a separate scrubber room.
On detection of a chlorine concentration of 3 ppm or above in the
chlorine handling or storage areas, the scrubbing system will be activated
automatically. The air/chlorine mixture in the affected areas is drawn into the
scrubber by the scrubber fan via ducting connected to the normal ventilation
system. An electrically-operated isolating damper is provided in the scrubber
intake which opens automatically when the scrubber fan starts up.
The scrubber system is normally set at auto control mode to recycle air
back to the drum storage area. However, the treated air may be discharged to
atmosphere at roof level when the chlorine concentration is below 3 ppm. The
control for recycling or discharging air to atmosphere is effected by means of
a pair of electrically operated change-over dampers which can also be manually
controlled from the local control panel. A continuous chlorine monitor is
installed at a point downstream of the packed tower and upstream of the
vent/recycle changeover dampers. It has a high level alarm which sounds at both
the local control panel and in the main control room when the chlorine
concentration exceeds a pre-set level.
The sodium hydroxide solution is of 10-12% concentration and is held in
a solution tank beneath the packed tower. When the system is in operation, the
sodium hydroxide is recirculated by a pump to the distributor at the top of the
packed tower to provide adequate irrigation to the packing. Sufficient solution
is provided to absorb 1 tonne of chlorine. A mist eliminator is provided at the
top of the packed tower to prevent entrainment of liquid into the treated air.
The scrubber is provided with the following additional features: a
sampling point, a top entry mixer (for in-situ preparation of the sodium
hydroxide solution), a direct reading transparent level gauge, an inspection
window and level indication with high and low level alarms, and a temperature
measurement device for monitoring the temperature of caustic solution during
the preparation process.
9.5.2.5 Emergency Repair/Stoppage Kit for Chlorine Spillage/Leakage
According to Fire Services Department's fire safety requirements, a set
of emergency repair/stoppage kit for chlorine spillage/leakage is provided and
maintained in good working condition at all times for use by the trained
persons and stowed adjacent to but outside the store/plant room. Regular drills
are conducted to train personnel on the proper use of the breathing apparatus
and protective clothing.
9.5.3 Surrounding Topography
The topography around the SSWTW is shown in Figure 9.7. To the immediate south and east of SSWTW, there are
small hills rising to between 35 and
The meteorological data used in this study is the data recorded at the
Ta Kwu Ling weather station in Year 2006 - 2011 by the Hong Kong Observatory. The
weather data have been rationalised into different combinations of wind
direction, speed and atmospheric stability class. The probabilities of
occurrence of each combination during day and night are presented in Table 9.2. The
Pasquill-Gifford stability classes range from A through F. Class A represents
extremely unstable conditions which typically occur under conditions of strong
daytime insolation. Class F on the other hand represents moderately stable
conditions which typically arise on clear nights with little wind. Turbulent
mixing, which will affect the dispersion of a chlorine cloud, increases through
the stability class range from F to A. Distribution of wind directions in 2006
- 2011, as plotted as a wind rose in Figure 9.1, shows the prevalent
wind direction is from the east.
Table 9.2 - Meteorological Data (2006 - 2011)
|
|
Probability |
||||||||
|
Day |
Night |
|
|||||||
|
Wind Speed (m/s) |
2.5 |
2 |
4.5 |
1 |
1.5 |
4.5 |
4.5 |
||
|
Atmospheric Stability |
B |
D |
D |
F |
D |
D |
F |
Total |
|
|
Direction |
N |
0.0366 |
0.0226 |
0.0287 |
0.0187 |
0.0104 |
0.0258 |
0.0451 |
0.1880 |
|
NE |
0.0099 |
0.0061 |
0.0043 |
0.0061 |
0.0017 |
0.0059 |
0.0187 |
0.0527 |
|
|
E |
0.0865 |
0.0469 |
0.0341 |
0.0221 |
0.0350 |
0.0316 |
0.0934 |
0.3496 |
|
|
SE |
0.0190 |
0.0171 |
0.0101 |
0.0130 |
0.0163 |
0.0142 |
0.0831 |
0.1729 |
|
|
S |
0.0150 |
0.0084 |
0.0019 |
0.0091 |
0.0018 |
0.0011 |
0.0569 |
0.0943 |
|
|
SW |
0.0246 |
0.0090 |
0.0022 |
0.0045 |
0.0023 |
0.0007 |
0.0248 |
0.0681 |
|
|
W |
0.0153 |
0.0034 |
0.0002 |
0.0039 |
0.0003 |
0.0001 |
0.0141 |
0.0373 |
|
|
NW |
0.0108 |
0.0036 |
0.0004 |
0.0056 |
0.0009 |
0.0004 |
0.0153 |
0.0370 |
|
|
Total |
0.2176 |
0.1172 |
0.0820 |
0.0832 |
0.0686 |
0.0799 |
0.3515 |
1 |
|
9.7.1 SSWTW Surrounding Population
Population data to be considered include the existing population around
SSWTW and future NDAs population, which may be affected by an accidental
release of chlorine from SSWTW. Details of population distribution and
population data are presented in Appendix 9.1.
Population considered in this assessment includes all population within
the
With the proposed NDAs development, projected
population at 2032 inside the Consultation Zone (CZ) of SSWTW is expected to
increase from 4,720 to 5,460 (by about 16%), most of which is planned far away to the east and south-east of
SSWTW, avoiding the impact of accidental chlorine release from the prevalent
wind direction (East, nearly one third of the time in a year). Furthermore, these
locations are shielded by small hills at immediate east and south boundary of SSWTW.
Estimation of future population is based on the following sources:
1) Planning parameters for the areas in the NDAs. The data include:
a. G/IC Provision
Assessment tables for NDAs;
b. Development
Schedules; and
c. Data from
other departments such as Correctional Services Department and Hong Kong Police
Force.
2) For other areas surrounding SSWTW, the figures are based on the 2006
Population Census from the Census and Statistics Department and other available
information sources. An average annual growth rate of 1.1%, as estimated by the
Planning Department [9-9], was adopted to
project the future population at surrounding areas of SSWTW with potential
further residential development such as villages. For well-established areas
with no further residential development such as Tsui Lai Garden (Estate), it is
conservatively assumed population will remain the same for the future years,
considering the decreasing trend of average domestic household size in North
District (3.2 in 2001, 3.1 in 2006 and 3.0 in 2011) according to the Census and
Statistics Department [9-10]. For areas with
approved future residential development such as public housing development site
at Choi Yuen Road, population will be considered in the assessment for projected
future years.
3) Population in Riverside Promenade areas (where cycle tracks and pedestrian
linkages will be provided) is estimated from a site survey at Sha Tin, where
similar facilities are provided in riverside/seafront areas. Details are
described in Appendix 9.2. For amenity areas
where recreation facilities will be provided, a population density of 0.01
person per m2 will be adopted, as reference to other approved EIA
study [9-11].
4) For schools, kindergartens and elderly homes, information will be
collected from the Education Department, Social Welfare Department and
corresponding websites.
5) Surveys undertaken by the consultants.
The population data are presented in five time periods including night,
working day, weekend day, peak hour and “jammed peak”, as adopted from the
Reassessment Study. A “jammed peak” period is considered for major roads
representing the probability of standstill, “bumper-to-bumper” conditions in
one traffic direction. The description of the time periods is provided in Annex
I of the Reassessment Study. A summary is given in Table 9.3.
Sensitive populations such as homes for the elderly, kindergartens and
hospitals (vulnerable population factor 3.3) are separately identified from
other populations (vulnerable population factor 1). The definition of the
vulnerable population factor and its use in the assessment are explained in Section 9.9.3.4.
Table
9.3 - Different Time Periods and Distributions
|
Time Period |
Mon. ~ Fri. |
Sat. |
Sun. |
% Distribution |
|
Peak |
18.75 hr |
3.75 hr |
0 hr |
13.39% |
|
Jammed Peak |
1.25 hr |
0.25 hr |
0 hr |
0.89% |
|
Working Day |
40 hr |
4 hr |
0 hr |
26.19% |
|
Weekend Day |
0 hr |
4 hr |
12 hr |
9.52% |
|
Night |
60 hr |
12 hr |
12 hr |
50.00% |
9.7.2 Transient Population
Modelling of the impact of chlorine releases on road and rail
populations follows the HSE approach [9-8], as described in
Annex F2 of the Reassessment Study. Traffic population considered in this study
includes population on those from the roads in the vicinity of SSWTW, and
railways to the west of SSWTW. The locations of these roads and railway are
indicated in Figure 9.8.
9.7.2.1 Road Traffic
Population associated with the road vehicles will be modelled as 100%
outdoor, which is consistent with the Reassessment Study.
Current average daily traffic is estimated from Annual Traffic Census
2011 [9-12]. Traffic forecast
from the NDA plan are adopted to estimate the peak hour traffic flow in the
future projected years for cases with and without NDAs development. Traffic
during daytime non-peak hours and night are taken as 87% (=5.65/6.53) and 37% (=2.44/6.53)
of peak hour traffic, as estimated from ATC 2011. Traffic variation is
estimated from several major traffic stations in New Territories (Table 9.4).
Table
9.4 - Traffic Variation during Different Time Periods at Major Traffic Stations
(ATC 2011)
|
Station |
Average Hourly Traffic / Daily Traffic(1), % |
||
|
|
|||
|
Peak |
Day |
Night |
|
|
|
6.33 |
5.56 |
2.55 |
|
|
6.63 |
5.73 |
2.35 |
|
|
7.05 |
5.60 |
2.18 |
|
S5008 Yuen Long |
6.05 |
5.39 |
2.69 |
|
|
6.10 |
5.43 |
2.75 |
|
|
6.80 |
5.91 |
2.29 |
|
|
6.70 |
5.92 |
2.28 |
|
S5025 Yuen Long Highway |
6.53 |
5.64 |
2.44 |
|
Average |
6.53 |
5.65 |
2.44 |
Note: (1) Estimated from the Figures “Traffic
flow variation and growth” of corresponding traffic stations.
Average vehicle occupancy is 1.7 persons per vehicle at Core Station
S5003 (a section of Fanling Highway near Sheung Shui Railway Station) as
estimated from Annual Traffic Census 2011 [9-12]. In this
assessment, average vehicle occupancy of 2 persons per vehicle is adopted for
roads near SSWTW, which is deemed as a conservative estimation. The average
traffic population is calculated from the following formula:
It is assumed vehicle speeds under normal traffic conditions are
9.7.2.2 Railway - East Rail and Lok Ma Chau Spur Line
MTR East Rail network traverses the
The Lok Ma Chau spur line is located outside of the CZ, at a distance of
more than
The approach employed in the Reassessment Study will be adopted in this
assessment to estimate the affected population on trains by chlorine releases.
The trains are much alike to the road vehicles, except that they are unlikely
to come to a halt within a chlorine cloud. This means that the exposure of rail
passengers to the released chlorine is limited to the duration for which the
train is within the cloud plus the time for the chlorine to disperse from the
carriages subsequently. Population is based on crush-loaded train but divided
by factors to account for limited exposure duration and length of train, and
multiplied by length of track within zone of interest.
Potential hazards associated with the storage, use and transport of chlorine in SSWTW were identified in the Reassessment Study. A total of 36 hazards were identified during the HAZOP study for SSWTW, which will be described in details below. A site visit confirms operation of SSWTW has not been changed since the Reassessment Study. These identified hazards were further examined by reviewing historical incident database, the Major Hazard Incidents Data Service (MHIDAS), which confirms the hazard scenarios identified in the Reassessment Study are acceptable for the current assessment.
9.8.1 Hazardous Characteristics of Chlorine
The following paragraphs summarise some of the key hazardous
characteristics of chlorine (ICI Chlorine Handbook [9-13]):
· Chlorine gas is heavier than air and as a result will tend to accumulate in low places when released to the atmosphere and flow downhill in still air. However, slight breezes or thermal turbulence will cause it to move upward, so people are not necessarily safe simply because they are above the point of release.
· Chlorine gas has a greenish-yellow colour which is only visible at concentrations (above approximately 500ppm) many times higher than the danger level (see Table 9.5 below).
· Chlorine gas is a respiratory irritant. Symptoms caused by inhalation of chlorine include: headaches, pain, difficult breathing, burning sensation of the chest, nausea and watering of the eyes.
The physiological effects of chlorine are summarised in Table 9.5.
Table
9.5 - Physiological Effects of Chlorine
|
Concentration (ppm) |
Effects |
|
0.2-3.5 |
Threshold of odour perception in most individuals |
|
3-5 |
Tolerated without undue ill effect for half to one
hour. |
|
5-8 |
Slight irritation of the mucous membranes of the
upper respiratory tract and of the eyes. |
|
15 |
Effects are immediate. Irritation of nose, throat
and eyes with cough and lachrymation. |
|
30 |
Immediate cough with a choking sensation,
retrosternal chest pain and a sense of constriction in the chest. |
|
40-60 |
Development of a chemical tracheo-bronchitis and
pulmonary oedema. |
|
1000 |
Concentration likely to be fatal after a few deep
breaths. |
9.8.2 HAZard and OPerability (HAZOP) Study and Characterisation of Chlorine Release Scenarios
In the Reassessment Study, a Hazard and Operability (HAZOP) study was
conducted for SSWTW to provide a full and systematic identification of the
hazards associated with the delivery, storage and handling of chlorine in the
previous Reassessment Study. The HAZOP technique provides a means of examining
deviations from the design intent, their causes, consequences and safeguards,
in a structured manner.
The primary focus of the HAZOP was on the hazards posed to people
off-site. “Internal” as well as “external” hazards were considered, i.e. those
within the control of the operating staff, such as the hazards arising during
drum connection/disconnection, as well as those outside their control such as
an external fire. The information provided for the HAZOP included the site
layout plan, Process and Instrumentation Diagram (P&ID), chlorine store
layout plan, as well as the Operations and Maintenance Manual.
The HAZOP considered the various operating modes of the plant
(auto/manual) as well as planned maintenance operations. Prior to the HAZOP
study, previous HAZOP studies of WTWs and chlorine leak incidents were reviewed
to provide additional input to the identification of the chlorine release
scenarios.
Chlorine hazards from the following operations were identified during
the HAZOP Study for SSWTW:
· Transport of chlorine containers along the site access road (including manoeuvring of the truck outside the entrance to the truck unloading bay);
· Handling of containers within the store;
· Containers in storage;
· Connection and disconnection of chlorine containers;
·
Chlorination system (including
the liquid chlorine pipework, evaporators, chlorinators and ejectors);
For releases occurring within the chlorine store a Contain and Absorb
system is provided to minimise the likelihood of the release escaping to
atmosphere. The principal failure modes of the Contain and Absorb system were
identified at the HAZOP:
· Failure of leak detection system
· Failure of contain system
· Failure of chlorine absorption system
Local chlorine leak incidents, which have occurred in Hong Kong, were
reviewed against the identified hazardous scenarios during the HAZOP.
The potential hazardous chlorine release scenarios identified by HAZOP
were characterized in terms of the release inventory (1 tonne to 14 tonnes),
release rate or quantity to atmosphere (57 kg to 10 tonnes for an instantaneous
release, 0.027 kg/s to 14.4 kg/s for a continuous release), hole size (3 mm to
18x6 mm) and phase of release (liquid / two-phase), following the approach
outlined in the methodology report of the Reassessment Study. Scenarios of
insignificant release, which poses negligible off-site risk, were screened out
for further risk assessment.
9.8.3 Review of MHIDAS Incident Database
A review on Major Hazard Incident Data Service (MHIDAS) database of the
relevant historical incidents of the same genus to SSWTW has been conducted to
confirm whether the hazardous scenarios identified in the Reassessment Study
are applicable.
16 records from the MHIDAS were identified as the same genus of Water
Treatment Plant of this assessment. Table 9.6
summarises these 16 incidents. Details of each incident are given in Appendix
9.3.
From the incidents records, causes of incidents can be classified into
three categories. These categories are pipework failure, tank/drum failure and
cylinder failure. The first 2 categories of hazard scenarios have been
identified and assessed in the Reassessment Study, while the third category is
not applicable to the current assessment as no cylinder of chlorine will be
used or stored at SSWTW. With respect to transportation hazard, no relevant
incident has been found.
Table
9.6 - Summary of Chlorine Incidents of Water Treatment
Plant from MHIDAS
|
Hazardous Scenario |
No. of Cases |
Country |
Related to SSWTW |
|
Pipework Failure |
7 |
France, Hong Kong, UK & USA |
Yes |
|
Tank/Drum |
6 |
Puerto Rico, UK, USA |
Yes |
|
Cylinder Failure |
3 |
France, UK & USA |
No (No cylinder installed in SSWTW) |
Upon completion of
the incident review, no new hazard has been identified. For other hazards
identified in the Reassessment Study, such as earthquake, truck fire, etc, no
historical incidents related to these hazards has been found from the MHIDAS
search.
The historical
incidents search indicates that the Reassessment Study had identified some
hazard scenarios that historically had not happened. However, to ensure that
potential hazard scenarios have been considered, all hazards identified in
Reassessment Study will be adopted for this assessment.
9.8.4 Review of Existing Chlorine Facilities
Information regarding the latest chlorine facilities installed in SSWTW
has been gathered during site visit to the water treatment works in July 2009.
During the visit, an interview has been conducted with operation staff to
confirm the latest operation and safety practice in place in the water
treatment works.
As advised by the water treatment works operators, the treatment
throughput and storage of chlorine drums have not been changed since the
Reassessment Study.
The mechanical ventilation system and the chlorine scrubbing system
installed provide controlled air circulation and treatment of air in case of
chlorine release. These systems are designed to prevent chlorine gas escape
from the storage area in case of leakage.
Regarding the safety provision, emergency repair and stoppage kit
manufactured to the specification of the Chlorine Institute is provided
according to Fire Services Department’s safety requirement.
In the previous Reassessment Study, two mitigation measures were
identified to effectively reduce the risk from ALARP to the acceptable level:
(1) Provision of a containment barrier at northwest corner of SSWTW, (2)
Improvements to access road (markings and signage) to SSWTW. WSD has committed
to implement these two mitigation measures scheduled for completion in 2015
prior to the implementation of the NDAs development. Therefore, these
mitigation measures will be taken into account in this hazard assessment to
examine the risk impacts from SSWTW.
9.8.5 Hazard Associated with Construction Works
The NDAs development involves construction activities near SSWTW site
such as sewage treatment works extension and police driving and traffic
training complex, which are at a minimum distance of 290 m and 280 m
respectively. These two facilities are separated from SSWTW by a small hill
covered with heavy vegetation, which forms a natural protective barrier for
SSWTW. It is considered that activities at these sites would not pose any
impacts to SSWTW.
Therefore, no adverse impact associated with construction activities to
the chlorine storage and dosing system of SSWTW is anticipated.
A comprehensive
consequence analysis (wind tunnel test, CFD modeling and DRIFT modeling) was
conducted in the Reassessment Study to assess chlorine gas dispersion from SSWTW.
For the NDAs development, medium-rise and high-rise residential/commercial
buildings are planned at distances of more than
The assessment of the consequences of a chlorine release essentially
involves three steps:
· Modelling the initial release of chlorine (whether inside or outside the chlorine building);
· Modelling the dispersion of chlorine in the atmosphere; and
· Assessing the toxic impact to people off-site (whether indoors or outdoors).
The methodology for the consequence analysis in this assessment follows
the Reassessment Study. A summary of the methodology is given below.
9.9.1 Initial Release of Chlorine
The initial release of chlorine or 'source term' is modelled using
standard discharge rate formulae as detailed in the Reassessment Study. Releases
direct from the chlorine container are the most significant and, in the case of
chlorine drums, these are modelled as liquid releases.
The rapid flashing of chlorine which occurs following a liquid leak from
a drum is conservatively assumed to result in 100% entrainment of the liquid as
aerosol with no rain-out. For catastrophic (instantaneous) liquid releases the
rapid boiling of the chlorine on contact with the ground is assumed to result
in entrainment of twice the initial flash fraction as aerosol, following Lees [9-15]. The remainder of
the liquid chlorine is modelled as a spreading, evaporating pool.
For releases of chlorine within the chlorine building, a simple 'perfect
mixing' model is used to account for the initial dilution of chlorine, based on
9.9.2 Dispersion of Chlorine in the Atmosphere
Advanced techniques had been used for prediction of the dispersion of
chlorine in the atmosphere. The effects of buildings and variable ground
terrain on the dispersion of chlorine were modelled. The modelling involved
three elements:
· Wind tunnel simulations;
· Computational Fluid Dynamics (CFD); and
· Flat terrain dispersion modelling.
The wind tunnel and CFD studies represent the 'state of the art' in
dense gas dispersion modelling and provide the only rigorous means of
accounting for the effects of buildings and complex terrain. Wind tunnel test
has been used in this study to investigate a range of release scenarios, wind
directions and wind speeds in near-neutral atmospheric conditions. CFD has been
used to determine the influence of atmospheric stability on the dispersion of
chlorine and provide a broad comparison against the wind tunnel results for
neutral stability.
The role of the flat terrain dispersion modelling had been to provide
the 'source term' for both the wind tunnel and CFD studies. The model used in
the study was DRIFT [9-19], an integral
dispersion model developed by AEA Technology under the sponsorship of the UK
Health and Safety Executive. DRIFT contains the necessary thermodynamics and
heat transfer sub-models to be able to simulate the dispersion of a cold,
aerosol-laden cloud typical of the early stage of a chlorine release. DRIFT
runs were used to simulate the full range of chlorine release rates and weather
conditions. In conjunction with the wind tunnel and CFD, this provided all the
data needed for input to the QRA.
9.9.3 Toxic Impact Assessment
9.9.3.1 Chlorine Probit Equation
The following probit equation has been used to estimate the likelihood
of fatality due to exposure to chlorine:
Pr = -14.3 + lnC2.3t
where
Pr = probit value
C = chlorine concentration (mg/m3)
t = exposure time (minutes)
This probit equation is recommended for use in QRA studies by the Dutch
Government [9-20] and incorporates
the findings of most recent investigations into chlorine toxicity.
Table
9.7 shows
the relationship between the chlorine concentration and the probability of
fatality for the TNO probit, assuming 10 minute exposure duration.
Table
9.7 - Chlorine Toxicity Relationship
|
Chlorine Concentration (ppm) |
Probit Value for 10 min Exposure |
Probability of Fatality (LD = Lethal Dose) |
|
251 |
3.17 |
0.03 (LD03) |
|
557 |
5.00 |
0.50 (LD50) |
|
971 |
6.28 |
0.90 (LD90) |
9.9.3.2 Modelling of Escape from the Chlorine Cloud
In risk assessments for toxic gas releases it is a common practice to
take into account the possibility of escape of exposed persons. This is because
at lower concentrations of the gas, people may be able to obtain protection by
moving indoors or directly out of the cloud.
Modelling of escape from the chlorine cloud is adopted from the
Reassessment Study. The methodology followed is similar to that developed by
the UK Health and Safety Executive [9-21]. It assumes that a
person out of doors will have a probability of escape dependent on the chlorine
cloud concentration, with escape occurring either directly out of the cloud or
to a nearby building. The methodology takes into account the dose received
during escape as well as the subsequent dose in the place of refuge. Suitable
conservative assumptions are made for the time of escape bearing in mind the
debilitating effect of the chlorine gas.
Incorporating all the above considerations it is possible to calculate
an 'effective' outdoor fatality probability, ie the fatality probability that
can be applied to the total outdoor population at any given location taking
into account the probability of escape.
The consequence analysis gives three fatality probability contours for
each release scenario, corresponding to 3%, 50% and 90% nominal outdoor
fatality probability. The effective outdoors fatality probabilities
corresponding to these levels of fatality are shown in Table 9.8
below.
However, escape from the chlorine cloud is not assumed for the outdoor
population in Lo Wu Correctional Institution (LWCI) due to the physical
boundary barriers. Therefore, in this assessment the ‘nominal’ probability of
fatality is considered for the outdoor population in LWCI.
Table
9.8 - Effective Outdoors Probability of Fatality
|
Nominal Outdoor Fatality Probability (for
a Person Remaining Outdoors)(1) |
% of Population Attempting Escape |
Effective Outdoor Fatality Probability (Taking
into Account the Probability of Escape)(2) |
|
90% |
0% |
90% |
|
50% |
80% |
31% |
|
3% |
80% |
0.7% |
Notes:
(1) Fatality applicable to outdoor population
in LWCI.
(2) Fatality applicable to outdoor population
other than LWCI.
9.9.3.3 Protection for Persons Indoors
Following similar previous studies undertaken in
Protection is also considered for people on the upper floors of high
rise buildings. This is based on data on the typical height of a chlorine cloud
provided by the dispersion modelling.
Certain groups of people, i.e. the young, the elderly and the infirm
will be more sensitive to the effects of chlorine than others. This is taken into account in the QRA by
increasing the fatality rate applied to certain sensitive receivers such as
nurseries, primary schools, old people homes and hospitals.
In line with data published by Withers and Lees [9-22] and risk criteria
applied to sensitive developments in the UK and Australia, the fatality rate
for these groups of people is set a factor of 3.3 higher than for the average
population.
9.9.3.5 Transient Population
The approach to modelling the effect of chlorine releases on transient
populations, in particular road vehicles and trains, essentially follows that
developed under research work undertaken on behalf of the UK HSE [9-8], as described in
Annex F2 of the Reassessment Study. The same approach is adopted in this
assessment.
9.10.1 Rationalization of Chlorine Release Scenarios
In the Reassessment Study, the consequence analysis from wind tunnel test
and CFD modelling shows that only certain, severe types of chlorine release
which could produce fatal off-site concentrations of chlorine. The release
cases which fall into this category are external continuous releases of
These results mean that many of the chlorine release scenarios identified
in the HAZOP study can be eliminated from further consideration in the QRA.
Based on the results of the consequence analysis, scenarios posing an off-site
hazard were further considered in the QRA. To simplify the assessment, these
scenarios were further grouped into ‘events’ having identical release characteristics
(i.e. the same release rate, duration and phase of release), as shown in Table 9.9 and Table 9.10.
Base
failure rates and event frequencies of occurrence are adopted from the
Reassessment Study. Table
9.11 summarises the
results of the frequency calculations of the release scenarios included in QRA.
Table 9.9 - Release Scenarios Included in QRA
|
Event Ref |
Component Scenarios |
Release Rate (or Quantity) to Atmosphere |
Type of Release |
Release Location |
|
IU1TSRU |
Spontaneous failure Dropped drum |
|
Instantaneous |
Chlorine store |
|
RU1TSML |
Rollover Loadshedding Spontaneous failure |
|
Continuous |
Access road |
|
RU1TMML |
Rollover Truck fire |
|
Continuous |
Access road |
|
RU1TSRU |
Truck impact Truck fire Spontaneous failure |
1 tonne |
Instantaneous |
Access road |
|
RU1TMRU |
Truck fire |
3 tonnes |
Instantaneous |
Access road |
|
EU1TMRU |
Earthquake: roof collapse, ground acceleration |
10 tonnes |
Instantaneous |
Chlorine store |
|
EU1TMRU |
Earthquake: roof collapse, ground acceleration |
10 tonnes |
Instantaneous |
Chlorine store |
Table 9.10 - Release Scenarios Categorised by Leak
Quantity
|
Leak Quantity (kg) |
Event Ref |
|
0-10 |
None |
|
10-100 |
IU1TSRU |
|
100-1000 |
RU1TSML, RU1TMML, RU1TSRU |
|
>1000 |
RU1TMRU, EU1TMRU, EU1TMRU |
Table 9.11 - Event Frequencies
|
Event Ref |
Component Scenarios |
Frequencies (per year) |
Time Periods during which Event could Occur |
|
IU1TSRU |
Dropped drum Spontaneous drum failure |
1.69E-6 4.54E-4 |
All except Night All |
|
|
Total |
4.56E-4 |
|
|
RU1TSML |
Rollover Loadshedding Spontaneous leak |
1.04E-6 2.54E-7 1.03E-7 |
All except Night All except Night All except Night |
|
|
Total |
1.40E-6 |
|
|
RU1TMML |
Rollover Truck fire |
7.65E-8 8.99E-8 |
All except Night All except Night |
|
|
Total |
1.66E-7 |
|
|
RU1TSRU |
Truck impact Truck fire Spontaneous drum failure Total |
2.49E-7 4.76E-8 5.08E-8 3.47E-7 |
All except Night All except Night All except Night |
|
RU1TMRU |
Truck fire |
8.89E-9 |
All except Night |
|
EU1TMRU |
Earthquake |
3.30E-7 |
All |
|
EU1TMRUH |
Earthquake |
7.00E-8 |
All |
9.10.2 Event Frequencies with Implementation of Previous Identified Risk Mitigation Measures
In the previous Reassessment Study, two mitigation measures were
identified: (1) Provision of a containment barrier at northwest corner of
SSWTW, which could eliminate the risk due to the event IU1TSRU. (2)
Improvements to access road (markings and signage) to SSWTW, which could result
in a reduction of 50% in frequency of truck-related accidents. Since WSD has
committed to implement these two mitigation measures scheduled for completion
in 2015 prior to the implementation of the NDAs development, these two mitigation
measures will be taken into account in this hazard assessment and the event
frequencies are listed in Table 9.12.
Table 9.12 - Event Frequencies with Implementation of
Previous Identified Risk Mitigation Measures
|
Event Ref |
Component Scenarios |
Frequencies (per year) |
Time Periods during which Event could Occur |
|
RU1TSML |
Rollover Loadshedding Spontaneous leak |
5.20E-7 1.27E-7 1.03E-7 |
All except Night All except Night All except Night |
|
|
Total |
7.50E-7 |
|
|
RU1TMML |
Rollover Truck fire |
3.83E-8 4.50E-8 |
All except Night All except Night |
|
|
Total |
8.33E-8 |
|
|
RU1TSRU |
Truck impact Truck fire Spontaneous drum failure Total |
1.25E-7 2.38E-8 5.08E-8 2.00E-7 |
All except Night All except Night All except Night |
|
RU1TMRU |
Truck fire |
4.45E-9 |
All except Night |
|
EU1TMRU |
Earthquake |
3.30E-7 |
All |
|
EU1TMRUH |
Earthquake |
7.00E-8 |
All |
9.11.1 Risk Assessment Methodology
Risk summation was conducted using RISKSUM, which is developed
specifically for the chlorine dispersion risk assessment. It combines input
information on the frequencies of hazardous chlorine release scenarios,
consequences of chlorine dispersion, population information to generate risk
results in terms of individual risk and societal risk.
RISKSUM is a risk assessment tool based on standard, commercial
softwares, i.e. Microsoft Excel and Access Database. Microsoft Excel stores all
the input information, performs the risk calculation and demonstrates the risk
results. It is associated with the Access Database, which saves the
intermediate results for data processing. The calibration exercise demonstrates
results generated by RISKSUM are consistent with the tool used in the previous
Reassessment Study.
The main outputs from RISKSUM are:
· Individual risk in the form iso-risk contours;
· Societal risk in the form of an FN curves and Potential Loss of Life (PLL)
9.11.2 Risk Results for Base Case
9.11.2.1 Societal Risk Results
The societal risk results for SSWTW are shown in Figure 9.9 and Figure
9.10 in the form of FN curves. Table 9.13 and Table 9.14 present the overall PLL values, with a
breakdown by release scenario and population area.
As can be seen from Figure 9.9 and Figure 9.10, FN curves
for SSWTW lie in the acceptable region for both cases with and without NDAs
development. With NDAs development, the overall potential
loss of life (PLL) is anticipated to increase by 18% for Year 2023 (2.36x10-5
per year to 2.78x10-5 per year) and 16% for Year 2032 (2.37x10-5 per year
to 2.76x10-5 per year).
From Table
9.13, it is clear that the dominant risk contributor is chlorine
release due to earthquake, which accounts for about 90% of PLL for the existing
population near SSWTW and the additional population within NDAs development,
respectively. As shown in Figure 9.11 (breakdown of FN
curves by Accident Type), occurrence of a large number of fatalities (more than
10) is largely caused by high-intensity earthquake, which could lead to rupture
of multiple chlorine drums in the chlorine store and impact to a much larger distance
than the chlorine release due to accident on the access road. Most of the
population within NDAs development is located far away from the SSWTW, outside
the 1-km CZ, which accounts for the higher PLL
contribution from earthquake. However, it is noted that in Hong Kong the probability
of highly intensive earthquake is very low (3.3x10-6 and 1.4x10-7
per year for ground acceleration of
As shown in Table
9.14, for existing populated areas, the major risk receptors are population
located to the west of SSWTW. The most significant population affected is
associated with existing MTR East Rail and Lo Wu Correctional Institution,
which account for about 50% of the
overall PLL, and are situated at a distance of 90 m and 500 m from SSWTW,
respectively. These two risk receptors are situated downwind of the SSWTW from
the prevalent wind direction (East, nearly one
third of the time in a year). The dominant risk
receptors within the NDAs development are areas in close proximity of the SSWTW,
such as Sewage Treatment Works Extension (construction site) and Riverside Promenade
areas near SSWTW. It is noted that the densely populated residential / commercial
areas planned at FLN and KTN are far away from SSWTW (about
9.11.2.2 Individual Risk Results
The individual risk results are shown in Figure 9.12. The
maximum individual risk level is in the range of 1x10-6 per year and 1x10-7
per year, which is lower than 1x10-5 per year thus meets the
individual risk criteria.
It should be noted that individual risk refers to the risk to a
hypothetical person spending 100% of his/her time outdoors in the vicinity of
the SSWTW, thus the upper-bound estimate of the risk to an actual individual. Individual
risk reflects the risk of a person at a specific location, and is not affected
by population around the hazardous sources, i.e. not affected by the NDAs
development.
Table 9.13 - Breakdown of PLL by Release Scenario
|
Release Scenario |
Case 1 (2023 no NDA) |
Case 2 (2023 NDA only) |
Case 3 (2023 NDA + Surrounding) |
Case 4 (2032 no NDA) |
Case 5 (2032 NDA only) |
Case 6 (2032 NDA + Surrounding) |
||||||
|
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
|
|
Spontaneous container failure |
3.68E-07 |
1.6 |
6.49E-08 |
1.5 |
4.23E-07 |
1.5 |
3.68E-07 |
1.6 |
5.32E-08 |
1.3 |
4.12E-07 |
1.5 |
|
Earthquake |
2.14E-05 |
90.6 |
4.01E-06 |
91.4 |
2.53E-05 |
91.0 |
2.15E-05 |
90.8 |
3.74E-06 |
92.4 |
2.51E-05 |
91.1 |
|
Dropped drum |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Truck – impact |
8.14E-07 |
3.4 |
1.50E-07 |
3.4 |
9.50E-07 |
3.4 |
8.15E-07 |
3.4 |
1.21E-07 |
3.0 |
9.23E-07 |
3.3 |
|
Truck – fire |
5.56E-07 |
2.4 |
9.98E-08 |
2.3 |
6.47E-07 |
2.3 |
5.56E-07 |
2.3 |
8.12E-08 |
2.0 |
6.28E-07 |
2.3 |
|
Truck – rollover |
4.15E-07 |
1.8 |
5.71E-08 |
1.3 |
4.49E-07 |
1.6 |
4.15E-07 |
1.7 |
5.05E-08 |
1.2 |
4.43E-07 |
1.6 |
|
Truck - loadshedding |
4.35E-08 |
0.2 |
4.82E-09 |
0.1 |
4.40E-08 |
0.2 |
4.35E-08 |
0.2 |
4.63E-09 |
0.1 |
4.38E-08 |
0.2 |
|
Total |
2.36E-05 |
100 |
4.39E-06 |
100 |
2.78E-05 |
100 |
2.37E-05 |
100 |
4.05E-06 |
100 |
2.76E-05 |
100 |
Table 9.14 - Breakdown of PLL by Population Area
|
Top Risk Receptors |
Case 1 (2023 no NDA) |
Case 2 (2023 NDA only) |
Case 3 (2023 NDA + Surrounding) |
Case 4 (2032 no NDA) |
Case 5 (2032 NDA only) |
Case 6 (2032 NDA + Surrounding) |
||||||
|
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
PLL |
% |
|
|
SS-R (MTR East Rail) |
7.57E-06 |
32.0 |
|
|
7.57E-06 |
27.2 |
7.57E-06 |
31.9 |
|
|
7.57E-06 |
27.4 |
|
SS-42 / KTN-G1-8 (Lo Wu Correctional
Institution) |
5.62E-06 |
23.8 |
|
|
5.62E-06 |
20.2 |
5.62E-06 |
23.7 |
|
|
5.62E-06 |
20.4 |
|
SS-22 (Lo_Wu_Station) |
1.41E-06 |
6.0 |
|
|
1.41E-06 |
5.1 |
1.41E-06 |
5.9 |
|
|
1.41E-06 |
5.1 |
|
FLN-A2-3 (Sewage Treatment Works
Extension, Construction Stage) |
|
|
9.91E-07 |
22.6 |
|
|
|
|
|
|
|
|
|
KTN-C2-1 (Open Space, Riverside Promenade
Area) |
|
|
8.01E-07 |
18.3 |
|
|
|
|
8.01E-07 |
19.8 |
|
|
|
FLN-A1-5 (Amenity, Riverside Promenade
Area) |
|
|
7.86E-07 |
17.9 |
|
|
|
|
7.86E-07 |
19.4 |
|
|
|
FLN-A2-2 (Amenity, Riverside Promenade Area) |
|
|
|
|
|
|
|
|
6.10E-07 |
15.1 |
|
|
|
Others |
9.04E-06 |
38.2 |
1.81E-06 |
41.2 |
1.32E-05 |
47.5 |
9.11E-06 |
38.5 |
1.85E-06 |
45.7 |
1.30E-05 |
47.1 |
|
Total |
2.36E-05 |
100 |
4.38E-06 |
100 |
2.78E-05 |
100 |
2.37E-05 |
100 |
4.05E-06 |
100 |
2.76E-05 |
100 |
The hazard to life assessment concludes individual risk and societal
risk of SSWTW are acceptable for the proposed NDAs development (both
construction stage and operation stage), The overall PLL is increased by about 18% by implementation of NDAs development. Nevertheless, the overall risk
(in terms of individual risk and societal risk) lies within the acceptable level.
[9-6]
Scott Wilson/Parsons Brinckerhoff, EIA Study Report
of Route 16 Investigation Assignments from
[9-7]
FACV No. 28 of 2005, Judgment on Final Appeal
between Shiu Wing Steel Limited and Director of Environmental Protection,
Airport Authority of
[9-9]
Planning Department, Projection of Population
Distribution 2010 - 2019.
[9-10]
2011 Hong Kong Population Census, Summary Results,
http://www.census2011.gov.hk/en/index.html
[9-12]
Transport Department, Annual Traffic Census 2011.
[9-13]
ICI Australia, "Chlorine Handbook", 1995.
[9-15]
Lees, F P, Loss prevention in the Process
Industries, 1996.
[9-16]
[9-17]
[9-24]
Webber, Brief Review of RWDI and DRIFT Results, 16
February 1998.