10
Hazard to life
10.1 Introduction
10.1.1 A portion of the Project is located within the about 1 km-radius consultation zone of a Potentially Hazardous Installation (PHI), i.e. Siu Ho Wan Water Treatment Works (SHWWTW), as shown in Figure No. NEX1062/S/SHD/ACM/Z10/260.
10.1.2 A Hazard Assessment (HA) was conducted to evaluate the risk to the additional population arising from the construction and operation of the Project and SHD Topside Development due to storage of chlorine associated with the operations at SHWWTW.
10.2
Scope and Objectives
10.2.1
The HA
is carried out following the criteria for evaluating hazard to life as stated
in Annexes 4 of the Technical Memorandum on Environmental Impact Assessment Process
(TM-EIAO).
10.2.2
In accordance with EIA Study Brief ESB-296/2016, the
objectives of the HA are as follows:
i.
Identify hazardous scenarios
associated with the on-site transport, storage and use of chlorine at the
SHWWTW with a view to 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-EIAO; and
iv.
Identify and assess practicable and
cost-effective risk mitigation measures.
10.2.3
The methodology to be used in the hazard assessments
shall be consistent with previous studies having similar issues.
10.2.4 The general components of the HA include:
ˇ¤
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.
ˇ¤
Frequency Assessment: Assess the likelihood of occurrence of the
identified hazard scenarios.
ˇ¤
Consequence Assessment:
Assess the consequences and impact to the surrounding population.
ˇ¤
Risk Assessment: Evaluate the risk level, in
terms of individual risk and societal risk. The cumulative risks will be
compared with the criteria stipulated in TM-EIAO to determine their
acceptability. Subject to the assessment, practicable and cost-effective risk
mitigation measures will be identified and assessed.
10.3 Relevant Legislation and Guidelines
10.3.1 As set out in Annex 4 of the TM-EIAO, the risk guidelines comprise two components as follows:
ˇ¤ Individual Risk Guideline: the maximum level of off-site individual risk should not exceed 1 in 100,000 per year, i.e. 1 x 10-5 / year
ˇ¤
Societal Risk Guidelines are presented graphically as in Drawing 10.1. The Societal Risk Guideline is
expressed in terms of lines plotting the frequency (F) of N or more deaths in
the population from accidents at the facility of concern.
o Acceptable where risks are
so low that no action is necessary;
o Unacceptable where
risks are so high that they should usually be reduced regardless of the cost or
else the hazardous activity should not proceed;
o ALARP (As Low
As Reasonably Practicable) where the risks associated with the hazardous
activity should be reduced to a level ˇ°as low as reasonably practicableˇ±, in
which the priority of measures is established on the basis of practicability
and cost to implement versus risk reduction achieved.
Drawing
10.1 Societal Risk Guidelines
10.4
Assessment Methodology and Assumptions
10.4.1
With reference to Appendix 10.1, SHWWTW and Sham Shui Kok Chlorine Transhipment
Dock (SSK Dock) were identified as potential hazardous facilities.
10.4.2 The SHWWTW is the Potentially Hazardous Installation (PHI) with its consultation zone (CZ) encroached into the Scheme Boundary, while the potential risk due to the operation of SSK Dock is negligible.
10.4.3 For the SHWWTW, QRA has to be conducted to account for the cumulative risk posed to the Project and SHD Topside Development. Details of the assessment methodology and assumptions are stated in Appendix 10.1.
10.5
Summary of
Quantitative Risk Assessment Results
Overview
10.5.1 According to Appendix 10.1, by summing up all hazardous events, Individual Risk and Societal Risk associated with the identified hazardous scenarios are obtained and compared with the criteria set out in Annex 4 of the TM-EIAO to determine their acceptability.
Individual Risk Results
10.5.2 The individual risk contours for SHWWTW are presented in Figure 12.5 of Appendix 10.1. As shown in Figure 12.5, the 1x10-5/ year contour does not reach the boundary of the Project and hence the individual risk level comply with the individual risk criteria.
Societal Risk Results