14 HAZARD TO LIFE

14.1 Introduction

14.1.1.1 In accordance with Section 3.4.13 of the EIA Study Brief (ESB-346/2021), a hazard to life assessment should be conducted to evaluate the risks associated with the existing Au Tau Water Treatment Works (AT WTW) and the use of explosives for the construction of the Project.

14.1.1.2 The Hazard to Life Assessment requirements are detailed in Appendix L of the EIA Study Brief.

14.1.1.3 The relevant legislation and associated guidance applicable to the Project for the hazard-to-life assessment include the following:

· Technical Memorandum on Environmental Impact Assessment Process (EIAO-TM); and

· Dangerous Goods Ordinance (Cap. 295).

Technical Memorandum on Environmental Impact Assessment Process

14.1.1.4 As set out in Annex 4 of the EIAO-TM, the criterion for hazard to human life is to meet the Hong Kong Risk Guidelines (HKRG). The risk guidelines are expressed in terms of individual and societal risks as shown below:

Individual Risk:

Maximum level of off-site individual risk should not exceed 1 in 100,000 per year i.e. 1x10^-5 per year.

Societal Risk:

With the population increases, the societal risk will be increased. The societal RG is presented graphically in below. It is expressed in terms of lines plotting the cumulative frequency (F) of N or more deaths in the population from incidents at the installation. Two F-N risk lines are used in the RG that 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 that can reduce risk will be considered.

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Diagram 14.1 Societal Risk Guidelines for Acceptable Risk Levels

Dangerous Goods Ordinance

14.1.1.5 The conveyance of explosives by public roads in HKSAR is governed by the Dangerous Goods Ordinance (Cap. 295). A removal permit is required for transport on public roads. Also, the road vehicle carrying explosives should be of an approved type.

14.1.1.6 Storage of explosives is governed by the Dangerous Goods (General) Regulations (Cap. 295B). Under the regulation, a license is required for the storage of explosives.

14.1.1.7 The QRA for the storage, transport and use of explosives related to the construction phase of the Project, in which blasting activities are required. There will be no explosives handled during the operational phase. Hence, this chapter presents the QRA for the following:

· Storage of explosives including handling of explosives within the proposed temporary magazine site;

· Transport of explosives to the delivery points; and

· Use of explosives including handling of explosives from the delivery points to the blast face.

14.2 Project Description

14.2.1 Project Overview

14.2.1.1 As discussed in Section 2, the Project alignment involves a railway linking a new KSR(NOL) Station adjacent to the existing KSR(TML) Station with the new KTU(NOL) Station, via three interchange/intermediate stations at Au Tau (AUT), Ngau Tam Mei (NTM) and San Tin (SAT) together with supporting facilities for stabling and maintenance, and ancillary buildings to support railway operation.

14.2.1.2 Majority of the alignment of the Project will be in tunnels, which will be primarily constructed by Tunnel Boring Machine (TBM) while a small section of the tunnel will be constructed under drill-&-blast, mined and cut-&-cover for crossover at the Ngau Tam Mei Depot (NTD) portal and connecting tracks between Pok Wai Ancillary Building (PWA) and Long Ha Tsuen Ancillary Building (LHA).

14.2.1.3 The construction works of the Project will be carried out between 2025 and 2034 tentatively, with the peak tunnel excavation year between 2027 and 2029. Assessment Year for construction stage is taken as 2029 which would be the year of maximum traffic flow within the construction period of the Project. As no explosive will be used during operation stage of the Project, hazard assessment for explosives related issue is not necessary for operation stage. The tentative construction programme of the blasting works is provided in Appendix 2.2.

14.2.2 Blasting Requirement

14.2.2.1 The following table shows the latest construction methodologies for various tunnel sections envisaged at this stage. The blasting locations and the connection adits are also shown in Figure No. C1603/C/NOL/ACM/M61/302.

Table 14.1 Summary of Construction Methodologies for Various Tunnel Sections

Tunnel Section Between		Construction Methodology	Remark
South of KSR(NOL) Station	KSR Station	Cut-&-Cover Tunnelling	KSR(NOL) overrun tunnel and Enabling Works of Future Southern Extension
KSR (NOL) Station	AUT Station	TBM Tunnelling	Main Alignment
AUT Station	NTM Station	TBM Tunnelling	Main Alignment
NTM Station	SAT Station	TBM Tunnelling	Main Alignment
SAT Station	KTU (NOL) Station	TBM Tunnelling	Main Alignment
Pok Wai and Long Ha Tsuen Ancillary Buildings	NTD	Drill-&-Blast and Mined Tunnelling (approx. 1.1km)	Crossover & Connecting Tracks

Note:

KSR – Kam Sheung Road	NTM – Ngau Tam Mei	KTU – Kwu Tung
AUT – Au Tau	SAT – San Tin	NTD – Ngau Tam Mei Depot

14.2.2.2 It can be seen from the above table that among the entire 10.7km long alignment, majority of the tunnel sections would be constructed either by cut-&-cover tunnelling or TBM tunnelling, except for a short section of 1.1km of crossover and connecting tracks between PWA and LHA, and NTD that would need to be constructed by drill-&-blast and mined tunnelling for the required excavation profiles of opening to suit local geological ground conditions.

14.2.2.3 Among all the tunnel sections and the construction works as described above, only the crossover and connecting tracks between PWA and LHA, and NTD would require the use of explosives for excavation of the Drill-&-Blast tunnel. The cross-sectional areas for this section of drill-&-blast tunnel vary between approximately 65m² and 430m². According to typical engineering design and geology, the first 50-150m section from tunnel portal at NTD would likely be constructed by cut-&-cover and mined tunnelling methods and hence the tunnel section requiring drill-&-blast would be in the order of about 0.9 – 1.0km. Hence, the blast locations would be confined within the tunnel section and behind the blast door instead of at the portal.

14.2.2.4 There is also an underground tunnel space with a cross-section area of about 355 – 430m² which would need to be excavated at the southern part of the drill-&-blast tunnel, and for the intersection between connection adits of Long Ha Tsuen Ancillary Building and TBM tunnels for main alignment. Considering that the impact from ground vibration, etc. the blast working face at this underground tunnel space would be divided to 2 – 3 sub-blast working faces and the charge rate would be controlled as similar to blasting for typical size of drill-&-blast tunnel.

14.2.2.5 According to the latest design, typical cross sections with areas of 50 to 185m² for underground tunnel that would be excavated by multiple headings and benches are used for the estimation of the required explosives quantity. The height and span of each blast are approximately 8 to 10m and 7.5 to 15m respectively. Therefore, the total volume of rock being blasted is roughly 250 to 900m³. The required quantity of packaged explosives per blast face would be 40 TNT eqv. kg based on a typical cross section of 150 m², but will increase up to 50 TNT eqv. kg for a large excavation face of 185 m². Assuming that the maximum rate of blasting would require six blasts per day, the daily explosives requirement would be approximately 160 to 240 TNT eqv. kg (including connection adits which will be discussed in follow section). This does not include the requirement for bulk emulsion.

Connection Adits

14.2.2.6 Blast works are also required at the connection adits (approximately 10 and 75m long) for PWA, and the connection adits (approximately 25m long) for LHA.

14.2.2.7 The initial section of the connection adits for PWA in soft and mixed ground would be constructed by mined tunnelling method. For the lower portion of shaft for LHA, excavation would be carried out by blasting if hard rock was encountered. All the construction workforces within the ancillary building will be evacuated and the blast cover will be closed during blasting operation.

14.2.2.8 The cross-sectional area of the connection adits for tunnel ventilation is approximately 30 to 120m². The daily explosives requirement would be approximately 40 TNT eqv. kg.

14.2.3 Explosive Types

Proposed Explosives

14.2.3.1 Standard explosives to be adopted consist of emulsion explosives, either as initiating explosives (pre-packaged cartridge) or as bulk emulsion sensitized by gassing to render it into an explosive as it is pumped into the blast hole at the time of charging the face.

14.2.3.2 Both cartridged emulsion and bulk emulsion mainly contain ammonium nitrate, water and a hydrocarbon such as fuel oil. The cartridged emulsion may also contain 2 to 3% aluminum powder to increase the explosive temperature and its explosion power.

14.2.3.3 Cartridged emulsion will be transported from the designated Explosive Magazine to the construction site by the appointed contractor using licensed trucks.

14.2.3.4 Bulk emulsion precursor will be delivered to the blasting site within the access tunnel by the appointed third party supplier. It will only be classified as an explosive after being sensitized at the blast location or working face and the addition of a gassing. It will then be pumped into the blastholes by the addition of a gassing agent.

14.2.3.5 Detonators, cartridged emulsion and detonating cords will be used to initiate the blast at work face depending on the blast requirement. Non-Electric type detonators which are initiated by shock tube are recommended for the Project, but electronic detonators may be used subject to the contractor’s proposal.

Explosives Properties

14.2.3.6 Properties of the two types of explosives to be used in this Project are shown in Table 14.2.

Table 14.2 Explosives Types

Type	Function	Use	Example
Initiating explosives	To initiate main blasting explosives	Initiation of secondary explosive	Cartridges emulsion, detonating cords and detonators
Blasting explosives	Used as main blasting explosives	General blasting, Shattering rock / structures	Bulk emulsion, ANFO^[^1]

Note:

[1] ANFO stands for Ammonium Nitrate-Fuel Oil.

Cartridged Emulsion

14.2.3.7 Cartridged emulsion explosives contain an oxidising agent which is a combination of ammonium nitrate (single salt), water, and a hydrocarbon such as fuel oil. It contains high quantity of water which is around 10 to 14%. The mixture is complete with small amounts of emulsifiers, normally less than 1% in order to keep the water and oil mixture homogeneous.

14.2.3.8 It is classified as a UN Class 1.1D explosive and DG Class 1 explosive under the Hong Kong classification system, and has a TNT equivalence of 0.96, i.e. 0.96 kg of TNT per 1 kg of emulsion.

14.2.3.9 It is packaged in a range of plastic films with the tips clipped at each end to form a cylindrical sausage or wrapped in waxed paper which can be used for both priming and full column applications such as mining, quarrying and general blasting work. Cartridged emulsion is detonator sensitive, so it does not require the use of booster to cause its detonation.

Bulk Emulsion Precursor

14.2.3.10 The composition of bulk emulsion is similar to that of cartridged emulsion but without the existence of aluminum. The bulk emulsion precursor has a density of 1.38 – 1.40 g/cc. It is not considered as an explosive due to its sensitization and it is classified as UN 5.1 oxidizing substance which yields oxygen readily to stimulate the combustion of other materials.

14.2.3.11 It is stable under normal conditions and there would not be major fire hazard. The major hazard of bulk emulsion precursor is due to its oxidizing properties which can cause irritation of eyes and skin. It may explode when under prolonged fire, supersonic shock or very high energy projectile impact.

14.2.3.12 Since it is stable under normal conditions, the storage and transport of bulk emulsion precursor will not be included with the scope of this study.

Bulk Emulsion

14.2.3.13 Bulk emulsion will be mainly used for excavation of rock by tunnel blasting. Bulk emulsion precursor is sensitized at the blast site with the addition of a gassing solution and then it is added to the charging hose downstream from delivery pump.

14.2.3.14 The gassing solution will reduce the density of the bulk emulsion precursor to 0.8 – 1.1 g/cc which will cause the production of nitrogen gas bubbles that aid the propagation of the detonation wave and sensitize the emulsion. Once the emulsion is sensitized and gassed, it can be detonated with the assistance of a small booster and a detonator.

14.2.3.15 Bulk emulsion explosives and site mixed Ammonium Nitrate-Fuel Oil (ANFO) would only be classified as UN 1.5D explosive and Class 1 DG (explosives) after being sensitized and gassed during blasting onsite. Hence, non-sensitized bulk emulsion explosives or site mixed ANFO at magazine site and during transportation are not classified as explosives.

14.2.3.16 Moreover, the bulk emulsion should be pumped into the blast hole and completely fill the hole once it is mixed onsite.

Detonating Devices

14.2.3.17 Detonators are small devices that are used to safely initiate blasting explosives in a controlled manner. Although non-electric detonators are recommended for this project, electric detonators may be used subject to Contractor’s proposal. Hence, both non-electric and electric detonators will be studied in this assessment. Since there are many different types of detonators such as safety use, both electric and non-electric detonators will be studied in this assessment.

14.2.3.18 Detonators can be classified as 1.1B, 1.4B and 1.4S under Dangerous Goods (Application and Exemption) regulation (Cap. 295E).

14.2.3.19 Detonators and detonating cords are used to initiate the blasting. Although detonator is a device that contains the most sensitive types of explosives in common use, it is packaged in a manner such that they may be handled and used with minimal risk.

14.2.3.20 Detonators are manufactured with built-in delays of various durations so that it can facilitate effective blasting and enable shots to be initiated once but to fire sequentially. Hence, it can enhance the practical effects of the blast. The detonator to be used in this Project will be millisecond delay period detonator.

14.2.3.21 The delay time of a detonator is based on the burning time of the delay element which is a pyrotechnic ignition mixture pressed into a 6.5mm diameter steel tube. It first causes the primary explosion of a small amount of lead azide and the primary explosion will then trigger secondary explosion which is usually Pentaerythritol tetranitrate (PETN). The delay time is affected by the length of steel tube and the compaction of the pyrotechnic mixture within it. When designing the blasting of a blast face, the general principle is to select the required detonators to ensure that each blasthole will detonate more than 8ms apart.

14.2.3.22 Thin and flexible tubes with explosive core are called detonating cord. It has the effect of a detonator along its entire length and is suitable for initiating other explosives that are detonator sensitive like boosters and cartidged emulsion. It can be used for synchronizing multiple charges to detonate different charges and to chain multiple explosive charges together. The detonating cord is usually compressed with powdered PETN and it is initiated by the use of a blasting cap.

Charges and Delays

14.2.3.23 According to the Blasting Engineer, for the blast faces, if the MIC is restricted to less than 1 TNT eqv. kg, then cartridge explosives will be adopted. On the other hand, if the MIC is greater than 1 TNT eqv. kg, then bulk emulsion will be adopted. Where bulk emulsion is used, a single 125g emulsion cartridge per blasthole is required to act as the booster to initiate the sensitized bulk emulsion. The adoption of either cartridge or bulk explosive is not considered to have a significant effect on the required total quantity of explosive per blast.

14.2.3.24 However, it is important to note that bulk emulsion is classified as Category 7 under the Dangerous Goods Ordinance and is considered to become an explosive (Category 1) only after sensitization by gassing as it is pumped into blast holes.

14.2.3.25 Therefore, it comes under the regulation of the Fire Services Department as a flammable substance, and the storage requirements are less stringent. A licence from the Commissioner of Mines is required for manufacture of an explosive at the blast face, where the emulsion is sensitized by gassing and becomes an explosive at that stage.

14.2.3.26 Therefore, the requirement for a Project magazine site is only to cater for the storage of items classified as Class 1 (explosives), which include cartridge explosive and detonators. In this way, by maximizing the use of bulk emulsion and minimizing the required use of the items categorized as explosive when delivered to site, the Project transport and storage requirement for explosives is minimized in the interest of safety.

14.2.3.27 In order to facilitate a smooth blasting, perimeter holes will be lightly charged, using either detonating cords or string loading of emulsion. Detonating cords must be delivered to site as Class 1 DG (explosives). The typical quantity used per perimeter blasthole is two strips of 40g per metre detonating cord.

14.2.3.28 Each blasthole will also require a detonator, and these are also delivered to site as Class 1 DG (explosives). Each detonator typically contains up to 1g of explosive as the base charge. A small quantity of detonators or light (5g per metre) detonating cord is also required to complete the hook-up of all the individual blasthole detonators.

14.2.3.29 The boosters, detonating cord and detonators would need to be delivered to site as Class 1 DG (explosives). These are commonly all called packaged explosive, to distinguish them from bulk emulsion, which is not a Class 1 DG (explosives) when stored or delivered to site.

14.2.3.30 The lower limit for the use of bulk emulsion is determined by the accuracy of the proposed bulk emulsion pump. According to the latest design, the lowest charge weight for the use of bulk emulsion is 1 TNT eqv. kg.

14.2.4 Magazine Requirement and Selection Process

Magazine Requirement

14.2.4.1 Due to the 24-hour blasting requirements, it is not possible for Mines Division to deliver the required explosive quantities directly to the work areas as this would limit the blasting to one blast per day. Therefore, an explosive magazine is required. Apart from construction phase, explosives are not expected to be used, stored or transported, particularly during operation and decommissioning.

Need for a Magazine Site

14.2.4.2 As discussed in Section 14.2.5, the daily explosives requirement would be 160 to 240 TNT eqv. kg, subject to detailed design development. This result has then been adjusted to provide a maximum of 3 days storage capacity to cater for any delays in daily magazine replenishment deliveries by Mines Division, to cover poor weather conditions, boat breakdown, etc.. Required magazine capacity would therefore be at least 480 to 720 TNT eqv. kg. However, for conservative approach, 800 TNT eqv. kg has been adopted for worst case scenario.

14.2.4.3 It should be noted that these quantities are based on the use of 125g emulsion cartridge as primers. They also do not account for other situations which might require additional explosives quantities, such as areas of low Maximum Instantaneous Charge (MIC), less than 1 TNT eqv. kg allowable MIC, or additional blasting for connecting passages, niches etc. which may be in addition to the regular blast faces for shaft, adits and tunnels.

External Separation Distances

14.2.4.4 Other than the requirements from CEDD, the criteria for separation distances to protected works and/or buildings for Hazard Type 1 explosives, as specified in The Explosive Regulation 2014, Statutory Instrument 2014 No.1638, United Kingdom (for a brick-built mounded store for 350 - 400 TNT eqv. kg storage)^{^[1]} as shown in Table 14.3.

Table 14.3 Buffer Distances between Magazine Site and Neighbouring Landuse

Protected Works / Buildings	Approx. Distance (m) from Magazine Site
Protected Works / Buildings	350 to 400 TNT eqv. kg Explosives
Building	183
Major Road	183
Minor Road / Railway	91

Other Factors

14.2.4.5 The magazine site selection has considered a total of 7 candidate sites and they are depicted in Appendix 14.1. Apart from separation distances, the following points had also considered:

· Access for Mines explosives delivery vehicles (road condition / width / gradient / public road networks to site / etc);

· Land availability (ownership / existing landuse /planned development); and

· Site constraints.

14.2.4.6 After considering the candidate sites with the factors mentioned above, most of the sites were found to have some constraints which made them impracticable for the project. The key constraints for each candidate site are summarized in Appendix 14.1.

Selected Temporary Magazine Site

14.2.4.7 Following the searches for potential magazine sites for previous Drill-&-Blast tunnel projects, a further review has been carried out for this Project. Seven potential magazine sites have been identified, including two sites previously used for the Hong Kong Section of Guangzhou – Shenzhen – Hong Kong Express Rail Link (XRL) and CEDD Liantang projects, the existing magazine site for the Drainage Services Department Shatin Cavern project, two potential sites re-visited, the proposed works area/ works site at NTD for this Project, and one new potential site. Appendix 14.1 shows the selection of site based on consideration of the requirements and constraints.

14.2.4.8 Tai Shu Ha (Yuen Long) has been selected for the location of the proposed temporary magazine site as it is a better option in terms of land availability, less public objection, remote location and established design standard. A further advantage of selecting this location is that it is close to the proposed blasting sites with less transportation time to deliver explosives to the construction site.

14.2.4.9 Temporary explosive magazine site at Tai Shu Ha (Yuen Long) could be constructed within two years including tree transplant or compensation which is the approximate period available before blasting would need to commence. It provides flexibility to the blasting works to be completed according to the anticipated overall construction programme.

14.2.4.10 The proposed temporary explosive magazine site at Tai Shu Ha (Yuen Long) in fact is the former Tai Lam magazine site of XRL Project and CEDD Liantang projects. The site is currently unoccupied and the magazine for XRL was demolished.

14.2.4.11 The explosives storage of the proposed magazine site is limited to 800 TNT eqv. kg (with two 400 TNT eqv. kg storages) and the explosives stored would include initiating explosives and blasting explosives.

14.2.4.12 The proposed magazine site is relatively remote. The nearest village house is located at about 300m away. The distance from the nearest building of the Hong Kong Model Engineering Club (HKMEC)[2] is around 250m which fulfill the criteria of separation distance. Although the boundary of HKMEC is located around 160m away from the proposed magazine site, the operator of HKMEC International Model Aviation Centre periodically flies model aircrafts at about 200m, i.e. the runway, away from the site which is far from the proposed magazine site.

14.2.5 Statutory/Licensing Requirements and Best Practice

Use of Explosives

14.2.5.1 Bulk emulsions and bulk ANFO are commonly manufactured at the blast sites and use immediately for rock blasting. Under Section 16 of the Dangerous Goods (Control) Regulation, Cap. 259G, a manufacture (blasting) license is required to manufacture nitrate mixture, i.e. Group 2 Schedule 1 Dangerous goods (S1DG), within a blasting site. The Commissioner of Mines is the Authority for issuing the license.

14.2.5.2 The owner of the Manufacturing Unit (MU) must apply to the Commissioner of Mines for a manufacture (blasting) license on specific blasting sites in writing with the completed application form which requires the following information:

· The operation manual and procedures for manufacturing explosives;

· Procedures for safe handling and use of the manufactured explosives;

· Procedures for disposal of any waste product;

· A risk assessment on overheating, build-up of excessive pressure within the pump, etc., and the associated control measures to prevent the hazards occurring during the manufacturing process;

· An emergency response plan to deal with incidents affecting the safe operation of the MU and the hazards during the transport of the bulk products used for the manufacture of explosives and an emergency contact list; and

· Technical and safety information set out in Annex A of the “Guidance Note No. GN1 Licensing an Explosives Manufacturing Unit (MU) at a Blasting Site”.

14.2.5.3 For surface or underground transport by vehicles, the transporting unit (TU) carrying an MU shall comply with the following requirements:

· It shall have a diesel-powered engine;

· It shall be roadworthy with a valid vehicle license issued by the Commissioner for Transport;

· The TU shall be equipped with an emergency stop at an easily accessible position;

· All cables to rear lights shall be fitted within fire resisting conduits;

· The TU shall be equipped with three 6kg or four 5kg dry chemical powder fire extinguishers;

· The TU shall be equipped with personal protective equipment, which shall be worn by all operators appropriate to the products being handled, in accordance with the MSDS;

· No explosives, detonators or other dangerous goods shall be carried on the TU;

· Where mechanical track haulage is used for underground transport, the electric locomotive shall pull the trailer carrying the MU as close as possible to the blast face. The locomotive shall be equipped with:

o effective headlights and rear lights, and

o adequate earthing provisions.

14.2.5.4 Ammonium nitrate (AN) is used for manufacturing bulk emulsion explosives and bulk ANFO at blast sites. AN is classified as Dangerous Goods Category 5 – Strong supporters of combustion under Regulation 3 of the Dangerous Goods (Application and Exemption) Regulations, Cap. 295E. A license is required for the storage of DG Category 7 is required according to “A Guide to Application for Dangerous Goods License and Approval” and it is issued by Fire Services Department.

Storage of Explosives

14.2.5.5 Explosives are classified as Class 1 Dangerous Goods, and the Commissioner of Mines shall have the control and management of every depot subjected to Section 13C of Dangerous Goods Ordinance (Cap. 295). The storage for explosives must be within a licensed Mode A Store and to obtain the license, certain safety and operational criteria must be met to the approval of Mines.

14.2.5.6 To obtain a licensed Mode A Store for the magazine site, it will need to meet the general requirements stated in the “Guidance Note No. GN 8 How to Apply for a Mode A License for Storage of Schedule 1 Dangerous Goods (Blasting Explosives)” from Mines, GEO CEDD.

14.2.5.7 The typical pre-licensing requirements for issuing of a Mode A License for an explosives magazine are listed below:

· For a public works project, a certificate for the completion of the proposed Mode A Store, signed by a Registered Professional Engineer (Civil and Structural) and the Engineer’s Representative for the Contract;

· Training records for all personnel involved in the transport, handling and storage of blasting explosives and supervising the safety and security of blasting explosives for the site;

· A certificate signed by a registered electrical worker and a registered electrical contractor certifying that the lightning conductors function properly and comply with BS EN 62305;

· If the vehicles are used for transport of the blasting explosives outside the project site boundary, the vehicles must meet the requirements in Mine Division’s Guidance Note GN No.2 “Approval of an Explosives Delivery Vehicle”;

· Confirmation that the warning sign(s), notice(s) and placard(s) have be erected/displayed in accordance with section 38 of the Dangerous Goods (Control) Regulation (Cap. 295G);

· Confirmation that the Shot Firer has been provided with a portable lightning detector for use during the handling and transport of blasting explosives;

· Confirmation that the Hong Kong Police Force has approved the security aspects of the Store, including the security company providing armed security guards and the standing instructions for management/administration of the store;

· Confirmation that the Fire Services Department has approved the firefighting aspects of the store;

· Confirmation that the Environmental Protection Department has issued the Environmental Permit for the Project, including the proposed Mode A Store; and

· Confirmation that no high-tension overhead cables carrying 440V are within 45 m of a surface store/portal area of an underground store and that no overhead cables of 1 kV or above are within 75 m of the store/portal area, and that all other types of electrical cables should, except for lighting and firefighting installation connections, be run underground from a point at least 15 m away from the store.

14.2.5.8 The typical construction for a Mode A Store is stated below:

· The store should consist of a single storey stand-alone structure made of substantial brickwork, masonry or concrete to a design approved by the Commissioner of Mines in each case;

· All hinges and locks must be made of non-ferrous metal;

· No ferrous metal must be left exposed in the interior of the Mode A store;

· The interior and exterior walls of the Mode A store must be painted white;

· The outer side of the steel door of the Mode A store must be painted red. No ferrous metal must be exposed on the inner face of the door forming part of an interior of the Mode A store;

· A warning sign legibly showing the English words “DANGER – EXPLOSIVES” and the Chinese characters “危險 – 爆炸品” in white against a background in red must be displayed outside or adjacent to every entrance to the Mode A store. The English words and Chinese characters must not be less than 100 mm in height;

· As far as practicable, the roof of the store should be made of lightweight materials to limit the potential for injury from debris in the event of an explosion;

· A security fence surrounding the Mode A store must be installed and set back a least 6 m from the store. The fence should be 2.5 m high, stoutly constructed of chain link fencing with a mesh size not exceeding 50 mm. The fence should be firmly fixed to metal or concrete posts and topped with a 0.7 m high outward overhang of razor wire. The base of the fence located between the posts should be secured with pegs to prevent intrusion;

· The area between the security fence and the Mode A store must be cleared of all vegetation. Vegetation clearance must also apply to a minimum distance of 1 m on the exterior of the fence. A uniform cross-fall of at least 1 in 100 away from the store to a drainage system must be constructed;

· The road leading to the Mode A store must have a concrete surface and it should be constructed and maintained so that 11 tonne trucks (about 8.9 m long and 2.5 m wide) can use it under all weather conditions. A suitable turning circle or other alternative means for these trucks to turn must be provided so that the trucks can be driven up to the gate of the security fence;

· A guardhouse should be provided. For surface Mode A store, security guards should be on duty outside the inner security fence adjacent to the gate when there is no receipt or issue of blasting explosives inside the Mode A store. A separate outer security fence should be installed to protect this guardhouse. For an underground Mode A store, the guardhouse should be positioned inside the security fence to guard the entrance gate and the portal to the underground magazine;

· Inside the guardhouse, an arms locker constructed as an integral part of the house and fitted with a lock is required;

· A telephone should be provided for use by the guard in the guardhouse. A watchdog should normally be provided for the store. In this regard, the Hong Kong Police Force may agree to alternative site-specific security provisions, e.g. CCTV;

· Firefighting installations consisting of at least four 6 litre foam and one 4.5 kg dry powder fire extinguishers to be positioned on two racks and four buckets of sand should be provided at the nearest convenient locations to the Mode A store doors; and

· Regular inspections of vegetation and trees surrounding the Mode A store shall be arranged to maintain security and to mitigate the risk of fire affecting the store.

Transport of Explosives

Supply of Detonators and Cartridged Emulsion Explosives

14.2.5.9 Detonators are imported into Hong Kong. Destructive tests are conducted by the manufacturer and the test result must fulfil the requirement of their quality control and quality assurance (QC/QA) system before shipping to the client. If the test sample does not fulfill the standards, the batch of the detonators will be destroyed. The inner packaging of the detonators will print the delay time, detonator shock tube length, batch number and the date of manufacture.

14.2.5.10 After imported to Hong Kong, the detonators will then be stored at the Mines Division Kau Shat Wan (KSW) explosives depot. Users will place orders from Mines Division for delivering the requested amount of detonators to their on-site explosives magazine or to their blasting site on a daily basis as appropriate.

Application for Approval of an Explosives Delivery Vehicle

14.2.5.11 The explosives delivery vehicle should comply with the regulations stated in the “Guidance Note No. GN2 Approval of an Explosives Delivery Vehicle” published by Mines Division, CEDD.

14.2.5.12 The safety requirements for approval of an explosives delivery vehicle and requirements for signage on vehicle are listed below:

· The vehicle must:

o be powered by a diesel engine;

o comply with the Road Traffic (Construction and Maintenance of Vehicles) Regulations, Chapter 374;

o be kept clean, in sound mechanical condition and roadworthy; and

o be licensed to carry the maximum number of persons required for the delivery convoy. Subject to the agreement obtained from mines Division and the Police, an armed security guard may not be required if an approves Global Positioning System (GPS) has been installed in the vehicle.

· Cargo compartment:

o The cargo compartment of the vehicle, including the floor, must be constructed from sheet metal, at least 3mm thick, and lined internally with plywood, at least 13mm thick, and there must be no exposed ferrous metal in the interior of the cargo compartment;

o The interior of cargo compartment, including doors, must be kept in good condition and free from defects or projections that could damage to the explosives or their packaging;

o Electric wiring or electrical devices must not be installed inside the cargo compartment;

o The doors of the cargo compartment must be capable of being securely locked using a padlock. The padlock must meet BS EN 12320 Security Grade 4 or above requirements, or equivalent;

o Proper means of stowage must be provided to secure the loads during transport; and

o If the vehicle is designed to carry both detonators and other types of blasting explosives at the same time, additional requirements, given in AEISG (2014), are required.

· Safety provision

o The driver’s cabin must be separated by not less than 150mm from the cargo compartment of the vehicle;

o The exhaust system must be located as far from the cargo compartment as possible, preferably at the front of the vehicle. The Transport Department must approve any modification to the exhaust system;

o An emergency fuel cut-off device must be located at an easily accessible position with a label, in Chinese and English, prominently and legibly stating: “EMERGENCY ENGINE STOP 緊急死火掣”;

o For a typical vehicle with a gross vehicle weight of 9 tonnes or above, four fire 5 extinguishers, comprising two 2.5kg dry powder and two 9-litre foam fire extinguishers of an approved type, with certificates, must be provided. They must be mounted in front and on both sides of the rear body, in easily accessible positions, using securely mounted brackets and quick release clamps;

o A fire suppression system must be fitted to the engine bay of vehicles, complying with the AS5062-2016;

o All electrical installations must be designed, constructed and protected so that they cannot cause any ignition or short-circuit under normal conditions of use, and to ensure that the risk of this occurring will be minimized in the event of a traffic accident. All electrical wiring and fittings must be shrouded in fire resisting conduits;

o The fuel tank must be located below the cargo compartment of the vehicle. It must be protected from accidental damage and designed to prevent accumulation of spilt fuel on any part of the vehicle;

o Fire resistant material must be fitted between the wheel arches and the cargo compartment;

o Detonators and other types of blasting explosives must not be loaded or transported within the same cargo compartment of the vehicle, unless the cargo compartment fulfils the additional requirements as specified in Annex B of the “Guidance Note No. GN2 Approval of an Explosives Delivery Vehicle”;

o A hand-held lightning detector must be provided in the vehicle to detect lightning before and during loading and unloading of explosives. Should lightning be detected within a distance of 16km from the loading/unloading point by the hand-held detector, loading or unloading of explosives must cease until the lightning signal has cleared; and

o For a typical vehicle with a gross vehicle weight of 9 tonnes or above, two strobe beacons approved by the Transport Department must be installed on top of the cargo compartment.

· Signage on vehicle:

o Whenever the vehicle is carrying explosives, it must display on both sides and on the rear door of the cargo compartment, placards (minimum 250mm x 250mm) showing the label of the highest Hazard Code of explosives;

o Placards showing “EMPTY 空車” or blank placards must be displayed when the vehicle is empty; and

o The vehicle must be painted white with a warning in Chinese and English, at least 150mm high, as follows: “DANGER-EXPLOSIVES” and “危險－爆炸品 ” The warning must be in red or black and displayed on both sides and rear face of the cargo compartment. If possible, the warning must also be displayed on the front face of the vehicle.

14.2.6 Construction Cycle and Programme

14.2.6.1 After commissioning of the magazine, the proposed delivery-storage-blasting cycle will consist of the following elements:

· Delivery of explosives and initiating systems to magazine by Mines Division as needed;

· Storage in the magazine site;

· Transfer from the explosive site to the main construction access shafts or portals of the excavation utilizing public roads via route indicated in Appendix 14.2;

· Transfer to the working faces of the excavation; and

· Load and fire the face(s) to be blasted. Blasts in a particular area will be initiated from a common firing point once all personnel are clear and entry routes to each blast site are secured. All blasts are to be carried out underground.

14.2.6.2 Construction programme of the Project is shown in Appendix 2.2.

14.2.7 Transport of Explosives and Initiation Systems

Explosives Transport Requirement

14.2.7.1 As a two blasts per route per day scenario is required to meet the construction programme, the consumption of explosives is estimated to be 400 equivalent TNT kg (TNT eqv. kg) in total per route per day. Daily frequency of explosives such as cartridge explosives and detonating cord will be 2 times a day with maximum loading of 200 TNT eqv. kg per truck. Detonators shall be separately transported in explosives carrying vehicles.

14.2.7.2 The time required to complete one full cycle will be largely dependent on the size of the tunnel and length of advance, as drilling the blastholes and mucking out the blasted rock often take up the majority of the time. Delivery times for the explosives may also influence the chosen cycle time. Since cycle times of 12 hours, 16 hours or 24 hours are adopted in this Project, by assuming the cycle time of 12 hours, 2 blasts are the maximum number of blasts that could carry out in one day for each portal and adopted as worst case scenario in this assessment.

14.2.7.3 Therefore, the worst case for QRA has been considered by assuming there would be 2 blasts per portal per day. It also indicates that there would only be 2 deliveries of explosives per route per day as the explosives are required to be consumed once delivered to the blasting sites.

Explosives Transport Strategy

14.2.7.4 It is noted that transport of explosives is needed to deliver the explosives from Government explosive depots to the proposed magazine site and from the proposed magazine site to the Project construction sites.

14.2.7.5 According to the latest arrangement, Mines Division of CEDD would deliver explosives and detonators to the temporary explosive magazine site at Tai Shu Ha (Yuen Long). The transportation of explosives by Mines Division either to the magazine site at Tai Shu Ha (Yuen Long) or, if any, directly to sites is under Mines Division’s responsibility and hence beyond the scope of this QRA.

14.2.7.6 The explosives in the magazine site at Tai Shu Ha (Yuen Long) will then be withdrawn by the appointed contractors as required and delivered to the three construction sites for blasting. The construction sites include 1) north portal at NTD; 2) south portal (connection adits for PWA); and 3) middle opening (lower portion of shaft and connection adits for LHA).

14.2.7.7 Subject to detail design stage and Mines Division’s approval, partial delivery is possible. It can be arranged different vehicles to different locations, as long as each vehicle carry less than 200 TNT eqv. kg in total. Moreover, it will reduce the number of transportations, thus reduce the risk induced.

14.2.7.8 This QRA has already considered the transportation of explosives of transferring the maximum demand of explosives to all portals and openings (i.e. worst-case scenario). Furthermore, the transportation routes for partial delivery are also already covered in this QRA. The time for transportation for partial delivery would also be lesser than the time assumed in this QRA as partial delivery would only pass through the same route once or twice while in this QRA, it has considered that the same route would be travelled by the delivery truck three times as the explosives for the portals would be transported separately.

Explosive Transportation Routes

14.2.7.9 The longest route (i.e. Route 1) would be from the temporary explosive magazine site at Tai Shu Ha (Yuen Long) to the north portal which is about 11km long. The second longest is the route to the middle opening (i.e. Route 2) which is about 10km long. The shortest route is to the south portal (i.e. Route 3) which is about 8km long. Alignments of these 3 transportation routes are shown in Appendix 14.2.

14.2.7.10 The appointed contractors responsible for the transport of explosives shall fulfil the requirements from Commissioner of Mines and shall follow all the requirements as stipulated in “Guidance Note No. GN 2 Approval of an Explosives Delivery Vehicle” (GN 2) and “Guidance Note No. GN 3 Application and Handling of a Removal Permit” (GN 3) and all other criteria as needed.

14.2.7.11 The vehicle carrying the explosives is prohibited from passing through any tunnel on a public road.

14.2.8 Review of Potential Hazardous Installations in the Vicinity

14.2.8.1 According to the EIA Study Brief of the Project (ESB-346/2021), hazard assessment regarding the risk induced from the Project to Au Tau Water Treatment Works (AT WTW) (see Figure C1603/C/NOL/ACM/M61/301) shall be carried out. In addition, apart from AT WTW, a review has been conducted to identify any Potentially Hazardous Installations (PHIs) that their Consultation Zones (CZs) would overlap with the Project, including NOL alignment (approximately 10.7km long), above-ground structures and the associated temporary work sites and works areas. From the results of the review, there is no PHIs other than AT WTW PHI with its CZ overlapping with the Project.

14.2.8.2 According to the reply from Water Supplies Department shown in Appendix 14.3, as AT WTW was no longer a PHI as it has been delisted and there is no PHI within its CZ overlapping with the Project, hazard assessment for AT WTW is no longer required.

14.2.9 Domino Effects of High Pressure (HP) Town Gas Transmission Pipelines

14.2.9.1 The Hong Kong and China Gas Company (HKCG) operates and supplies town gas to the majority of Hong Kong households, and also to commercial and industrial customers. The major components for town gas are hydrogen, methane, carbon dioxide and a small amount of carbon monoxide. Majority of town gas is supplied from Tai Po Production Plant with the Ma Tau Kok Plant making up the rest and it is supplied through a network of high pressure (HP) underground town gas transmission pipelines to various districts of Hong Kong.

14.2.9.2 The HP underground town gas transmission pipelines runs along San Tam Road and Castle Peak Road – Chau Tau. The transport route of explosives is in close vicinity of a section of the HP gas pipelines on San Tam Road. Failure of explosives may be triggered by the thermal outcomes from town gas release when the explosives carrying vehicle hit the point of pipelines failure. This assessment will study the domino effects of the failure of HP underground town gas transmission pipelines affecting the failure of the transport of explosives.

14.2.9.3 The pipelines failure due to ground vibration and the subsequent release consequences are the major hazards for the HP underground town gas transmission pipelines. The failure of pipelines will be treated as secondary and/or tertiary hazards as discussed in Section 14.6.

14.2.10 Concurrent Projects during Construction Phase

14.2.10.1 Explosives are not expected to be used, stored or transported, particularly during construction and decommissioning of magazine site. Since there are no other concurrent, planned or committed projects leading to any other hazardous events at the present stage, it is therefore can be assumed that there will be no potential cumulative impacts during the construction phase of the Project.

14.3 Hazard to Life Assessment Methodology

14.3.1 Study Approach

14.3.1.1 The assessment consisted of the following six main tasks:

a) Data / Information Collection and Update: relevant data / information essential including population for the hazard to life assessment were collected;

b) Hazard Identification: Identify hazardous scenarios associated with storage, transport and use of explosives;

c) Frequency Estimation: Estimate the frequencies of each hazardous event leading to fatalities with full justification by reviewing historical accident data and previous similar projects;

d) Consequence Analysis: Analyze the consequences of the identified hazardous scenarios;

e) Risk Assessment and Evaluation: Evaluate the risks associated with the identified hazardous scenarios. The evaluated risks will be compared with the HKRG to determine their acceptability. Where necessary, risk mitigation measures will be identified and assessed to comply with the “as low as reasonable practicable (ALARP) principle used in the HKRG; and

f) Identification of Mitigation Measures: Review the recommended risk mitigation measures from previous studies, practicable and cost-effective risk mitigation measures will be identified and assessed as necessary. Risk outcomes of the mitigated case will then be reassessed to determine the level of risk reduction.

A diagram of a data flow

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Diagram 14.2 Schematic Diagram of QRA Process

14.4 Estimation of Population

14.4.1 Assessment Area

14.4.1.1 Diagram 14.3 shows the location of the temporary explosive magazine site at Tai Shu Ha (Yuen Long). Given that the maximum influence distance of the hazardous scenarios (see Table 14.26) is less than 70m, an assessment area comprising a 100m influence zone along the portals and openings, magazine site and along the transportation routes is therefore considered.

Diagram 14.3 Aerial Photo of the Magazine Site

14.4.2 Population along Explosives Transportation Routes

14.4.2.1 Three types of population are considered along the transportation routes:

· Pedestrian population on footpaths and pavements next to the transportation routes;

· Road population; and

· Building population.

Land and Building Population

14.4.2.2 Buildings within a 200m corridor (i.e.100m on both sides of transport route) were included in the assessment. Population in each building along the transport route is analyzed individually.

14.4.2.3 The population data including residential, industrial and transient population would be updated based on the following information to determine the projected population for assessment. The assessment year, i.e. Year 2029, is the year of maximum traffic flow within the construction period of the Project.

· Planning Department’s 2019 - based Territorial Population and Employment Data Matrix (2019 TPEDM);

· Census and Statistics Department’s 2021 Population Census;

· Annual reports of relevant schools; and

· Traffic forecast for assessment year.

14.4.2.4 According to 2019 TPEDM, population of Yuen Long and Northwest New Territories (Other Area) in Yeas 2019 is 175,150 and 222,800 respectively, while in Year 2031 is 159,850 and 353,900 respectively. Considering that negative population growth is observed in Yuen Long, the population in Year 2029 are assumed to be the same as the base year. For Northwest New Territories (Other Area), population growth rate is about 3.9% per year. Hence, a growth rate of 3.9% has been adopted for the population projection within Northwest New Territories (Other Area) to the assessment year. Population data adopted is summarised in Appendix 14.4.

Road population

14.4.2.5 The traffic density information used in this study is based on the traffic forecast provided by the Traffic Consultant. A population density approach was adopted for estimating the population within vehicles on the road. The occupancy for different types of vehicles were conservatively estimated as indoor population.

Flowing Traffic Population

14.4.2.6 The traffic density information used in this study was based on the latest 2021 Annual Traffic Census (ATC, 2021) and the information provided by the Traffic Consultant. Road population density was calculated using the following relations:

Where	AADT	is The Annual Average Daily Traffic
	P	is the average number of persons per vehicle
	W	is the road width in meter, based on actual data
	V	is the vehicle speed in km/hr

Traffic Jam Condition

14.4.2.7 Traffic population considered in this QRA covers population on Tai Shu Ha Road West, Shap Pat Heung Road, Yuen Long Highway, New Territories Circular Road, San Tam Road, Chuk Yau Road and Ching Yau Road.

14.4.2.8 During the transportation of explosives, it is possible that the traffic flow might be disrupted when an explosion initiation occurs on the explosives carrying vehicle. If a traffic accident is severe enough to lead to a vehicle fire, a traffic jam could be developed before the fire spreads to the explosive load causing initiation. The road with traffic jam condition will have a higher population density in general when compared to free-flowing traffic because the separation distances between vehicles are reduced significantly.

14.4.2.9 The occupancies for each vehicle type and vehicle mix are taken from the Annual Traffic Census (ATC) for 2021. Two core stations (Table 14.4) are selected to represent the transport route from the magazine site to the construction site.

Table 14.4 Core Stations Considered

Core Station	Description
5016	San Tin Highway, Castle Peak Road & San Tam Road (From Kam Tin Road to Fairview Park Boulevard)
5025	Yuen Long Highway (From Tin Shui Wai West Int to Lam Tei Int)

Pedestrian Population

14.4.2.10 Pedestrian flow on the pavement is assessed along the explosives transportation routes through site survey. The pedestrian density is estimated by the following equation:

Where	P	is the number of pedestrians passing a given point
	W	is the road width (m)
	Q	is the pedestrian speed (km/hr)

14.4.3 Time Periods and Occupancy

14.4.3.1 Four time-modes would be adopted to consider the temporal changes in population within the assessment area. Detailed description and frequency per year for each time variation mode is presented in Table 14.5. Occupancy of population during each time mode is based on assumptions listed in Table 14.6.

Table 14.5 Definition of Time Variation Mode

Time Variation Mode (TM)	Description	Period	Weighting per week	Frequency per year ^[1]
TM 1	Weekday Day	Monday to Friday (09:00 to 18:00)	45 hours	0.268
TM 2 ^[2]	Peak Traffic Hours	Monday to Sunday (07:00 to 09:00 and 18:00 to 20:00)	28 hours	0.167
TM 3	Weekend Day	Saturday and Sunday (09:00 to 18:00)	18 hours	0.107
TM 4	Night	Monday to Sunday (20:00 to 07:00)	77 hours	0.458

Notes:

[1] The frequency per year for each time variation mode is calculated as follows:

For example TM1, assuming the week day represents a period from Monday to Friday (09:00 to 18:00), frequency per year = 45 / (24*7) = 0.268

[2] Excavation of a tunnel by drill and blast is a cyclic procedure and according to the latest blasting design, the typical cycle times of 12 hours, 16 hours or 24 hours are commonly adopting. By assuming the worst-case scenario, a cycle time of 12 hours is assumed for drill and blast. With this cycle time, the worst case for delivery at one peak traffic hours per day is adopted for analysis.

Table 14.6 Temporal Population Distribution Factor

Type	Weekday Day	Peak Traffic Hour	Weekend Day	Night
Residential	20%	50%	80%	100%
Educational	100%	10%	55%	0%
Road traffic population	60%	100%	60%	15%
Temple	50%	10%	100%	0%
Recreational / Open Space	70%	10%	100%	0%
Office (Administration) / Commercial	100%	10%	100%	10%
Industry	100%	10%	55%	10%
Open Storage	100%	1%	51%	0%
Car Park	70%	100%	70%	10%
Government Station	100%	10%	55%	10%
Petrol Station	50%	100%	50%	1%
Pedestrian	100%	100%	100%	100%

14.4.4 Features Considered in this QRA

14.4.4.1 The following sets of features were considered as sensitive receivers:

Man-made slope and Retaining walls

14.4.4.2 These features include cut slopes, fill slopes, retaining walls and a combination of these. The slopes are covered with all types of facing, including shotcrete, chunam, stone facing and vegetation.

14.4.4.3 A number of man-made slopes within 250m from the blast faces have been identified as shown in Table 14.7. These features are considered in this assessment and the location of these features are shown in Appendix 14.5.

Table 14.7 Slope identified

Slopes	Slope Height (m)	Slope Length (m)	Slope Angle (^o)	Shortest Distance from blast face (m)
2SE-C/C159	6.4	55	50	135
2SE-C/C156	3.5	38	40	175
2SE-C/C157	3	54	45	160
2SE-C/C263	4.8	42	35	200
2SE-C/F2	12	95	40	215
2SE-C/C162	14	100	60	180
2SE-C/C189	3.5	30	45	205
2SE-C/C264	4.8	58	30	205
2SE-C/F26	8	75	40	190
2SE-C/C88	82	240	35	190
2SE-C/C2	20	200	50	215
2SE-C/C176	3	16	70	235
2SE-C/CR175	2	23	65	230

Natural Terrain Hillside and Boulders

14.4.4.4 The proposed magazine site is surrounded by natural terrains, so natural terrain within 250m of the blasting site boundary is considered in this assessment.

Existing Buildings and Structures

14.4.4.5 All the buildings and structures within 250m from the Project are considered in this QRA.

Utilities

14.4.4.6 The nearest HP underground town gas transmission pipeline is at a distance of around 220m from the Project which does not fall within the 150m consultation zone of HP pipeline defined by EMSD ^{^[3]}. Hence, it is not further considered in this assessment .

14.5 Hazard Identification

14.5.1 Overview

14.5.1.1 Hazard identification consists of a review of the following:

· Properties of the explosives;

· Scenarios presented in previous relevant studies;

· Historic accidents; and

· Discussion with explosives and blasting specialists.

14.5.2 Accidental Initiation due to Hazard Properties of Explosives

Explosive Types and their Properties

14.5.2.1 The physical properties for the explosives to be stored and transported in this Project are shown in Table 14.8.

Table 14.8 Types and Properties of Explosives

Explosive Type	TNT equivalent	Melting Point (1 °C) @ 1 atm	Auto-ignition Point (1 °C) @ 1 atm	UN Hazard Division
Cartridged Emulsion	0.96	170	230 – 265	1.1D
Cast Booster	1.3	80	180 - 190	1.1D
PETN (provided for detonating cord)	1.4	135 – 145	190	1.1D
PETN (provided within detonators)	1.4	120	190	1.4B/1.4S

14.5.2.2 Explosives can be considered as ‘initiated’ when a self-sustaining exothermic reaction is induced. Initiated explosives can result in severe burning without progression to explode, a deflagration or a detonation. A deflagration may transit to detonation while the mechanism of transition from deflagration to detonation is still under research.

14.5.2.3 Deflagration-to-detonation transition is the general process by which a subsonic combustion wave becomes a supersonic combustion wave (Schultz, Wintenberger, & Shepherd, 1999). The difference between detonation and deflagration is their travelling speed which detonation is a shock reaction where the flames travel at supersonic speeds while deflagrations are where the flames are travelling at subsonic speeds (Nolan, 2014).

14.5.2.4 However, either kind of the explosion can cause significant damage to surroundings which may lead to substantial fatalities and injuries. Therefore, it should be considered in the QRA.

14.5.2.5 When the explosives are stored in the temporary magazine site, its chance to be initiated accidentally is low as the surrounding environment of the storage is unlikely to experience extreme heat, shock, impact or vibration with sufficient intensity to trigger a detonation.

14.5.2.6 Therefore, the most common situation of an accidental initiation is the introduction of fire. Other scenarios that may cause initiation include severe impact ad friction.

14.5.2.7 Overall, the level of explosion should at least consider as deflagration due to casualty concerns. To cause a deflagration, the explosives should be subject to a stimulus which some of the potential stimulus are listed below:

· Local stimulus: to generate a ‘hot spot’ such as sparks, friction, impact and electrostatic discharge;

· Shock stimulus: due to shock or high velocity impact such as bullet impact and detonation of other explosives; or

· Thermal stimulus: mass heating leading to exothermic reaction (intense heat or fire).

14.5.2.8 However, for the types of explosives used in this Project, not all of these causes are necessarily leading to deflagration or detonation.

14.5.2.9 In this study, accidental initiation of explosives has been categorized as either fire or non-fire induced.

Hazard Properties of Emulsion Type Explosives

14.5.2.10 ANFO emulsion explosives contain Ammonium Nitrate (AN), which is a powerful oxidizing agent. Although initiation of emulsion based explosives would not be triggered due to friction or impact found in normal handling, it can be triggered from heat and confinement or severe shock from other explosion. The sensitivity of AN based explosives to deflagration or detonation is increased with the increase of temperature.

14.5.2.11 There are two broad categories of emulsions:

· Packaged emulsion (sensitized); and

· Bulk emulsion precursor (void-free liquid).

14.5.2.12 Cartridged emulsion are sensitized by either adding gassing solution or plastic microspheres to fulfil their intended function during manufacturing process, so that they can be transported under an sensitized state. Bulk emulsions are sensitized at the point of use of sites. Therefore, the difference of chemical properties between these two emulsions is mainly due to the presence of sensitizer.

14.5.2.13 Matrix or bulk emulsion (no voids) is not shock-sensitive because there is no known mechanism for the shock front to propagate. Moreover, a very high pressure is required to heat a void-free liquid.

14.5.2.14 In normal atmosphere conditions, a local stimulus generating ‘hot spots’ including sparks, friction, impact, static electricity extreme ambient temperature does not cause packaged emulsions (sensitized) to readily deflagrate in normal atmosphere conditions. An additional pressure in excess of 5 bars above atmospheric pressure is required in the “deflagrating mass” in order to generate a deflagration which may subsequently transit to a detonation.

14.5.2.15 The behaviour of packaged emulsion following a shock or thermal stimulus is discussed in the following sections.

14.5.3 Accidental Packed Emulsion Initiation by Fire

14.5.3.1 Pools of molten AN may be formed in a fire and may explode if they are contaminated with other materials such as copper particularly. AN may also melt and decompose in a fire with the release of toxic fumes which mainly contains oxides of nitrogen. When the temperature of AN reaches beyond 140°C (AECOM, 2014) or under molten state, its sensitivity to local stimuli increases.

14.5.3.2 Several tests have demonstrated that the explosives may ignite and burn, deflagrate and in some cases even detonate when they are subjected to fire engulfment. The time for an explosive to ignite is dependent to its physical characteristics and chemical composition.

14.5.3.3 Due to its high water content, cartridged emulsions are often considered less sensitive to fire engulfment via initiation. On the other hand, the water content of cartridged emulsions will be evaporated when disclosed to heat or fire. If the cartridged emulsions are exposed to heat or fire with high enough energy levels for a long duration and the confinement pressure increases, it may lead to initiation of cartridged emulsions.

14.5.3.4 When there is a fire surrounding the explosive load, the temperature of any reactive media will clearly be raised and cause evaporation of components such as water. The rate of temperature increase and evaporation depends on the design of the cargo container wall and the fire extent. The outer wall of the cargo container would have direct contact with the flame and heat will be transferred to the explosive load in the course of time.

14.5.3.5 It is considered that emulsions are harder to be initiated than ANFO as its water content is higher than ANFO, so longer time is required as the water inside emulsions needed to be evaporated first before triggering the initiation of it.

14.5.3.6 The consequences of an accidental explosion due to thermal stimulus could be a thermal explosion (cook-off) or detonation or some combination of the two.

14.5.4 Accidental Packaged Emulsion Initiation by Means Other than Fire

14.5.4.1 Non-fire initiation mechanisms are separated into two common distinct groups: mechanical and electrical group. Mechanical group included both shock and friction initiation and it is difficult to distinguish them in most accidental situations. It has been stated in approved EIA reports for West Island Line (AEIAR-126/2008, WIL EIA) and EIA reports for South Island Line (East) (AEIAR-155/2010, SIL EIA) that some non-emulsion explosives can be initiated mechanically at an impact velocity as low as 15m/s with the absence of piercing. If the explosives are pierced, the required velocity will probably be far less than 15m/s due to localized heat generation subjected to frictional rubbing between layers of explosives, and it is known as ‘stab-initiation’.

14.5.4.2 On the other hand, cartridged emulsion is insensitive to initiation via impact which is demonstrated from the bullet impact test from a high velocity projectile. From the results of the bullet impact test which has also been stated in the approved EIA report for Sha Tin Cavern Sewage Treatment Works (AEIAR – 202/2016, STC STW EIA), the detonation of nitroglycerine (NG) based explosives requires at least 10 times the energy level used in the bullet impact test.

14.5.4.3 Initiation will occur if the ignition energy level is above its minimum level. The minimum ignition energy levels range between 0.015J and 1.26J in general.

14.5.4.4 The required ignition energy level for the vast majority of explosives, including cartridged emulsions is far exceeded by contact with mains electricity. Comparing the energy levels possible from batteries or alternators fitted to motor vehicles, or that due to static build-up on clothing with the required energy level to initiate most commercial explosives, it is typically much less than that required. Therefore, only very sensitive explosives are likely to ignite from these electrical energy sources. As a result, electrical energy is not a possible energy source for the types of explosives intended to be used in this project.

14.5.4.5 Possible causes of degradation of cartridged emulsion may be water loss and prolonged temperature cycling above and below 34°C. These causes would lead to potential caking or a change in ammonium nitrate crystalline state and increase in volume, but neither potential caking nor increase in volume would become the cause of detonation by means other than fire.

14.5.5 Hazard Properties of Detonating Devices

14.5.5.1 Detonating devices may be triggered and explode when exposed to heat or flame, or with friction, impact, heat, low-level electrical current or electrostatic energy. Detonation produces shrapnel. Hazardous gases or vapours produced in fire include lead fumes, nitrogen oxides and carbon monoxide and the type of gases produced depend on the material used in the detonators.

14.5.5.2 PETN is the main explosive component contained in detonating devices including detonating cord and detonators. Detonators also contain a primary explosive such as lead azide substance which is very sensitive to initiation.

14.5.5.3 The sensitivities of PETN inside the detonating cord is similar to that of NG based explosives but generally more sensitive than emulsions.

14.5.5.4 PETN has the potential to deflagrate at ambient pressure following a local stimulus. Local initiation can lead to deflagration under ambient pressure or higher and may lead to detonation afterwards. It has a comparatively small failure diameter for detonation as an explosive, i.e. having the smallest physical size of a cylindrical charge of high explosive which sustains a high order steady-state detonation.

14.5.5.5 By comparing PETN with emulsions, PETN can be initiated by shock instantly but at the same time, its shock sensitivity is lower than that of NG based explosives. The detonation of PETN requires at least 10 times the energy level used for NG based explosives based on the results of the bullet impact test.

14.5.6 Accidental Initiation Associated with Storage at Magazine

14.5.6.1 The possible means of accidental initiation of the explosives by fire for the proposed magazine are as follows:

· Inadequately controlled maintenance work (e.g. hot work);

· Poor housekeeping (e.g. ignition of combustible waste from smoking materials);

· Inappropriate methods of work;

· Electrical fault within the store, which ignites surrounding combustible material resulting in a fire; or

· Arson.

14.5.6.2 The possible means of accidental initiation of the explosives by means other than fire for the proposed magazine include the followings:

· Dropping of explosives during handling (for the detonators only); or

· Crushing of explosives under the wheels of vehicles during loading or offloading (for detonators and detonating cord only).

14.5.6.3 The detonators supplied are packaged within plastic separating strips, so that the initiation of a single detonator will not propagate to the adjacent detonator. The detonators Packaged in this manner are classified as Class 1.4B explosives and its total mass is negligible in terms of explosive mass.

14.5.7 Accidental Initiation Associated with Transportation from Magazine

14.5.7.1 The cartridged emulsion and detonating cord will be transported together within the same truck in the same compartment.

14.5.7.2 Since the vehicle cargo is designed based on the guidance note mentioned in Section 14.5, it is designed to minimize all sources for local stimulus, only a significant crash impact or a fire will cause a concern to the explosives. According to a study reported by the Advisory Committee on Dangerous Substances (1995), a low traffic speed is not likely to cause a concern to the explosives.

14.5.7.3 However, low speed traffic accident but with a low probability is considered possible in this assessment due to conservative approach. Based on the review with explosives professionals and bullet tests, the impact energy required to detonate PETN or emulsion based explosives is one order of magnitude higher than NG. As NG was considered as the basis for determining the probability of initiation under impact conditions in previous studies (assessed at 0.001), its probability can be reduced by one order of magnitude based on the impact energy consideration (AECOM, 2014).

14.5.7.4 The major leading causes for response of the explosives to an accidental fire are time (typically 5 – 10 minutes) and possibility to full fire development on the vehicle and the amount of heat transferred to the loads. For the case of emulsion explosion and based on the accident statistics, at least another 30 minutes are required for the explosives to reach critical conditions. This duration may be significantly reduced for the case of mixed loads of cartridged emulsions and detonating cords but exact time cannot be predicted based on the transport accident data for detonating cord (ERM, 2009).

14.5.7.5 The approach of explosives used in this project as transported was considered to be similar to the XRL Study. In the XRL Study, a review was conducted on the explosive properties with assistance from specialists in the explosives industry. The main findings for emulsion based explosives are as follows.

14.5.7.6 “The radical change in explosive properties at higher temperatures compared to the original emulsion must be taken into account. At high temperatures (> melting point), emulsion explosives would lose water content which may result in a refined explosive (small droplet/ crystal size AN). This could lead to a thermal explosion, deflagration or detonation and the probability of 0.1 may not therefore be applicable to emulsion. Also, some limited accident statistics have some bearing on this hazard scenario: these accidents may include a combination of both thermal and mechanical stimuli, which would likely have resulted in explosion or detonation. The consensus was that the probability of an explosion for the case of an emulsion was less than 0.5 but further refinement of this upper estimate would require additional data and more detailed analysis.” (ERM, 2009).

14.5.8 Incident Review

14.5.8.1 Reported safety incidents involving explosives for commercial and industrial applications have been reviewed in the following sections. The incident records are extracted from the UK Health and Safety Executive (UK HSE)’s Explosives Incidents Database Advisory Service (EIDAS), US Mine Safety and Health Administration (MHSA), Western Australia’s Department of Consumer and Employment Protection (DOCEP) and Hong Kong SAR Government’s Annual Controlling Officers Report.

14.5.8.2 To highlight the causative factors to the incidents, they were sorted into two main categories which are listed below:

· Incidents involving storage of explosives; and

· Explosive transport incidents.

Explosive Storage Incidents

14.5.8.3 According to a UK study written by Merrifield (1998), 79 major incidents associated with explosives manufacture and storage were identified from 1950 to 1997. A total of 16 major incidents were related to storage of explosives.

14.5.8.4 13 of them were due to the storage of gunpowder, ammunition, nitroglycerine and fireworks. One of the incidents was related to the storage of detonators and was caused by the corrosion of detonators, and the remaining two incidents were because of the storage of blasting explosives. Malicious activity is one of the reasons causing these incidents which involve blasting explosives.

14.5.8.5 From the above study, it can be seen that the protection of explosives from malicious human activity and the elimination of possible ignition sources are crucial for maintaining storage facilities.

14.5.8.6 Some identified initiating causes of accidents in storage facilities are listed below:

· Impact;

· Friction;

· Overheating;

· Electrical effects (lightning/static discharges);

· Sparks;

· Spontaneous reactions; and

· Malicious action/mishandling.

14.5.8.7 To avoid incidents happening in the storage area, the only actions we can do are maintaining good housekeeping practice, eliminating potential ignition sources and putting explosives into safe and secure storage space.

14.5.8.8 However, not all of these causes are applicable to the types of explosives used in this Project. These are further discussed in Section 14.6.

Explosive Transport Incidents

14.5.8.9 In Hong Kong, transport related incident records on vehicles carrying explosives have not been found. However, a minor incident happened at Queens Road West which involved a Mines Division truck in September 2010. Fortuitously, the crash impact was not significant, so that the integrity of the explosives was not affected.

14.5.8.10 The incident records from CEDD website and different news platform in Hong Kong have been reviewed up to Year 2022 and there were no incident records related to road transport of explosives.

14.5.8.11 The EIDAS (Explosives Incidents Database Advisory Service) database obtained most of the worldwide incidents related to the transport of commercial explosives reported from 1950 to 2017.

14.5.8.12 It has identified a transport incident related to emulsion in which a tyre fire on a truck has spread to the explosive load and detonated, producing a massive hole. This incident did not cause any fatality as the truck crew had time to leave the truck and maintain a safe distance before the tyre fire reached the emulsion load and exploded.

14.5.8.13 There were also some incidents involving mixed cargoes of emulsion or watergel carried with other types of explosives. The EIDAS database also found out 2 fire incidents associating explosives carrying vehicles in Australia in 1998 and 2007 respectively and all of these incidents did not cause any injuries or fatalities.

14.5.8.14 The incidents from 2007 to 2017 obtained from the EIDAS database has also been reviewed and there were 2 incidents caused by the use, transportation or storage of explosives. The first incident happened in 2008 which an explosion occurred during the pneumatic loading of an ANFO into underground holes. This incident has caused 13 fatalities and 5 injuries. The other incident occurred in 2012 and it has caused 1 fatality due to an explosion occurred in the powder feeder of the shock tube extrusion line which has communicated back to the magazine and detonated a few seconds later.

14.5.9 Scenarios for Hazard Assessment

14.5.9.1 The following hazardous scenario are identified for the hazard assessment.

Explosives Magazine

14.5.9.2 The temporary explosive magazine site at Tai Shu Ha (Yuen Long) will have 2 stores. Within each store, explosives and detonators are stored in separate compartments. The stores are designed with separation and enclosed walls so that initiation of the contents of one store will not affect other stores.

14.5.9.3 Therefore, the possible hazardous scenarios with the storage of explosives would be the detonation of the full contents of one store. The following scenarios are considered in this assessment:

· Detonation of a full load of explosives on a delivery truck within the magazine access road; and

· Detonation of the full quantity of explosives within a store.

14.5.9.4 The above scenarios are assessed for the proposed magazine site.

14.5.9.5 The explosives loads considered are listed in Table 14.9.

Table 14.9 Explosives Storage Quantities

Magazine

Mass of explosives per site (TNT eqv. kg)^[1,2]

No. of stores

TNT equivalent per store (TNT eqv. kg)

Explosive Types and its amount (TNT eqv. kg) ^[3,4]

Tai Shu Ha (Yuen Long)

800

400

· Cartridged Emulsion: <620

· Cast Booster: <40

· PETN (provided for detonating cord): <68

· Monoazidopentaerythritol mononitrate (MAPETN) (provided within detonators): <4

Notes:

[1] Assumed 40% detonating cord and 60% cartridged emulsion based on a typical pull length.

[2] Detonating cord are made of PETN

[3] Each detonator contains about 0.9g PETN.

[4] 1kg of cartridged emulsion equals 0.96kg of TNT, and 1kg of PETN equals 1.4kg of TNT.

Explosives Transport

14.5.9.6 The hazardous scenario considered for transport of explosives is accidents involving explosives delivered and transferred from magazine to each delivery point from the gate of each magazine to the gate of the construction face which cause the detonation of a full load of explosives on an explosives carrying vehicle.

14.5.9.7 Explosion of the detonator load during transport is not quantified for the following reasons:

· They are transported on a separated truck within the same convey.

· The detonator packages is classified as HD 1.4B or HD 1.4S (articles which present no significant hazard outside their package. This packaging can limit the consequences potentially leading to fatalities remain within the explosive truck boundaries. The UK CFRA has estimated the consequences for small quantities of explosives in workrooms. For a detonator load of less than 200g per trip to be transported in XRL, an accidental explosion will lead to approximately 1% chance of eardrum rupture at a distance of 3.5 metres; approximately 50% chance of eardrum rupture at 1.5 metres. If a person is very close to the explosion such as holding the explosives, he would have a high probability to be killed (CFRA, 2008).

Scenarios Considered in the Assessment

14.5.9.8 The assessed scenarios are summarized in the following table:

Table 14.10 Scenarios Considered in this Assessment

Tag	Scenario	Explosives load (TNT eqv. Kg)	No. of trips per year	Remarks
Storage of Explosives
01	Detonation of full load of explosives in one store in Tai Shu Ha (Yuen Long)	400	-	Total of 2 stores
Transport of Explosives
02	Detonation of full load of explosives in one contractor truck on public roads	200	2190	-

Use of Explosives

14.5.9.9 Possible hazardous scenarios regarding to the use of explosives are:

· Higher vibration generated by the blast face due to human errors and other reasons such as manufacturing defects causing deviation from the confirmed design;

· Higher vibration and air overpressure due to the detonation of a full load of explosives in one contractor truck from the delivery point to the tunnel portal at on-site transportation within the site boundary; and

· Higher vibration due to detonation of a full load of explosives in one contractor truck from the tunnel portal to blast face at on-site transportation within site boundary.

Hazards from the Blasting Process

14.5.9.10 The permitted vibration level of the sensitive receivers will determine the design of the blast face and is expected not to cause any damage to the sensitive receivers. However, vibration higher than expected may be induced by potential hazards arising in the event of deviations from the confirmed design occuring.

14.5.9.11 The relevant failure scenarios at the blast face which may lead to higher than expected ground vibration includes the manufacture of detonators and surface connectors, design of the blast, installation of detonators and surface connectors, and loading of explosives. The details are presented in Appendix 14.6.

14.5.9.12 The effects of overpressure and debris are not considered in this Project as a blast door is in place and closed during the blasting process.

Hazards from Transport of Explosives to Blast Faces

14.5.9.13 Cartridged emulsions, detonators and detonating cords are transported onsite from the delivery point to portal and then to the blast faces through the access tunnel by licensed diesel vehicle.

14.5.9.14 There are also manual transfer of cartridged emulsions, detonators and detonating cords from the magazine site to ventilation shaft. The cartridged cases and detonating cords delivered to the ventilation shaft will be conveyed to the ventilation shaft blast face using an appropriate and certified lifting system such as man-cage through shaft. The lifting system is provided with safety lock to prevent the fall of explosives in case of lifting mechanism failure.

14.5.9.15 The explosives are to be delivered from the explosives store to the ventilation shaft by manual transfer without the use of any tools which are susceptible to initiate the explosives.

Ground Vibration Associated with the Use of Explosives

14.5.9.16 Ground vibration is a potential hazard if the stress wave intensity is high enough to induce a high level vibration during rock excavation. Peak particle velocity (PPV) will be used as an indicator of damage to structures and it is assumed that reinforced concrete structures in good condition can encounter a PPV of 50mms without any risk of damage. Nonetheless, the PPV can be amplified by the peak ground motion and the PPV experienced by the structure. Hence, a PPV of the ground motion of 25mm/s is widely used to prevent damage to buildings.

14.5.9.17 Ground vibrations induced by this stress wave have a peak velocity that is related to the instantaneous charge weight (MIC) and the distance from the blast source. Diagram 14.4 presents the typical range of charge weights and predicted vibration levels using the MD vibration constants.

Diagram 14.4 Charge Weight per Delay (MIC) verses Distance and PPVc

14.5.9.18 It is considered that structures in vicinity to the blasting site are unlikely to be subjected to PPV levels greater than 5mm/s for normal blasting operations.

14.5.9.19 There can be different levels of damage considered for structures based upon previous records for ground vibrations and ground frequencies which has been identified by Guide to Cavern Engineering (Geoguide 4).

14.5.9.20 It identifies that blast ground vibration acceptance criteria depends on the type of structure, technical installations and occupancy, as well as the dominant frequency of the vibration. Blast ground vibrations normally have a frequency of 20 to 200 Hz which exceeds the natural frequency of most buildings. The dominant frequency depends on the medium transmitting the vibrations and can be some 40 Hz for soil, 40 to 70 Hz for sift or broken rock and 100 to 200 Hz for hard rock (Tamrock, 1989).

14.5.9.21 The natural frequency of tall buildings estimated can be expressed as the following equation:

14.5.9.22 If the ground motion frequency is similar to natural building frequency, it may lead to a larger motion of the building but this usually occurs when low frequency ground motion occurs over a long period of time (i.e. earthquakes last for 30 seconds to minutes) rather than the usual 4 to 9 seconds for a tunnel blast.

14.6 Frequency Analysis

14.6.1 Use of Explosives

14.6.1.1 The frequency assessment for the use of explosives consists of two parts which are the occurrence frequency of higher ground vibration due to errors in the blasting process and the occurrence frequency of higher vibration and air overpressure due to the transport of cartridges from the shaft to the blast site.

Frequency of Higher Vibration due to Errors in the Blasting Process

14.6.1.2 The main causes are due to human errors for all the failure scenarios identified in the high-level failure mode analysis during the blasting process which include errors in design manufacturing, installation, checking and recovery.

14.6.1.3 A fault tree analysis has been used to determine the failure rates or probabilities for the hazardous scenarios for Use of Explosives. Human Error Assessment and Reduction Technique (HEART) is carried out to determine the human error probabilities for the events.

14.6.1.4 HEART is a technique used in the field of Human Reliability Assessment (HRA), for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task. In this assessment, HEART is adopted to quantify human error probabilities by evaluating the relationships between humans, their specific tasks, performance shaping/human factors and error producing conditions.

14.6.1.5 Failure scenarios associated with the use of explosives include the following listed which is the same as the scenarios adopted in STC STW.

· Higher vibration due to 2 MIC detonated at the same time;

· Higher vibration due to 3 MIC detonated at the same time;

· Higher vibration due to 4 MIC detonated at the same time;

· Higher vibration due to 5 MIC detonated at the same time;

· Higher vibration due to 6 MIC detonated at the same time; and

· Higher vibration due to cut hole error.

14.6.1.6 For 2 MIC case, higher failure probability between bulk and cartridged emulsion was considered as an integral part of the models of overcharge of emulsion more than required as either one of the two emulsions will be used for a blast face in the fault tree. Thus, the overload was considered as one of the causes leading to a maximum of 2 MIC detonated simultaneously.

· More bulk emulsion explosives loaded into a production hole than required; and

· More cartridged sticks loaded into a production hole than required.

14.6.1.7 For 3 and 4 MIC case, the following failure cases have been considered:

· For 3 MIC case, charge overload with one error other than overload (i.e. design error in time delay, detonator put into a wrong sector, manufacture defect for a detonator, manufacture defect for a surface connector, incorrect connection of surface connector) will lead to 3 MIC detonated at the same time; and

· For 4 MIC case, charge overload with two errors other than overload will lead to 4 MIC detonated at the same time.

14.6.1.8 For cases more than 4 MIC, i.e. 5 and 6 MIC, each frequency increase in MIC is about 2 orders of magnitude lower. For a conservative approach, the cases of 5 MIC and 6 MIC detonation occurring simultaneously has been conservatively assumed to be the same as 4 MIC detonation.

14.6.1.9 The probability of the second human error of the same type was conservatively assumed as 0.01 to account for the potential dependency of human errors. This assumption has also been adopted in approved WIL and STC STW EIA.

14.6.1.10 Detailed fault tree analysis is shown in Appendix 14.6 and the modelled results are summarised as below.

Table 14.11 Occurrence Frequency Per Blast Face (North Portal)

Scenario ^[1]	Occurrence Frequency (/year)
Higher vibration due to 2 MIC detonated at the same time	7.21E-06
Higher vibration due to 3 MIC detonated at the same time	5.81E-08
Higher vibration due to 4 MIC detonated at the same time	5.89E-10
Higher vibration due to 5 MIC detonated at the same time ^[2]	5.89E-10
Higher vibration due to 6 MIC detonated at the same time ^[2]	5.89E-10
More cartridged sticks loaded into a production hole than required	1.05E-06
More bulk emulsion explosives loaded into a production hole than required	1.41E-06

Notes:

[1] Assume mischarge of explosives only occurs in one blast face.

[2] There is about 2 order of magnitude lower of each MIC. For a conservative approach, the frequency of 5 MIC and 6 MIC detonation occurring simultaneously has been conservatively assumed to be the same as 4 MIC detonation.

Table 14.12 Occurrence Frequency Per Blast Face (Middle Opening / South Portal)

Scenario^[1]	Occurrence Frequency (/year)
Higher vibration due to 2 MIC detonated at the same time	2.89E-05
Higher vibration due to 3 MIC detonated at the same time	2.48E-07
Higher vibration due to 4 MIC detonated at the same time	2.58E-09
Higher vibration due to 5 MIC detonated at the same time ^[2]	2.58E-09
Higher vibration due to 6 MIC detonated at the same time ^[2]	2.58E-09
More cartridged sticks loaded into a production hole than required	4.27E-06
More bulk emulsion explosives loaded into a production hole than required	1.41E-06

Note:

[1] Assume mischarge of explosives only occurs in one blast face.

14.6.1.11 As shown in Table 14.11, the probability of occurrence of overload of bulk emulsion into holes is higher than that for overload of cartridged sticks into holes. Hence, the probability of occurrence for overload of bulk emulsion were considered in the models for the failure scenarios of more than 1MIC detonated at the same time.

14.6.1.12 While in Table 14.12, the probability of occurrence of overload of cartridged sticks into holes is higher than that for overload of bulk emulsion into holes. Therefore, the probability of occurrence for overload of cartridged sticks were considered in the models for the failure scenarios of more than 1MIC detonated at the same time.

14.6.1.13 According to the latest design, there would be 6 blasts per day, i.e. 2 blasts per portal/opening per day. Overall frequencies of failure scenarios leading to higher vibration of the blasting are shown in Table 14.13 below.

Table 14.13 Overall Frequencies of Failure Scenarios Leading to Higher Vibration

Location	Occurrence Frequency for multiple MIC detonated at the same time (/ year)
Location	2 MIC	3 MIC	4 MIC	5 MIC	6 MIC
North Portal at NTD	5.27E-3	4.24E-5	4.30E-7	4.30E-7	4.30E-7
Middle Opening (Long Ha Tsuen Ancillary Buildings)	2.11E-2	1.81E-4	1.88E-6	1.88E-6	1.88E-6
South Portal at Pok Wai	2.11E-2	1.81E-4	1.88E-6	1.88E-6	1.88E-6

Frequency of Higher than Expected Vibration and Air Overpressure dure to Onsite Transport of Explosives

14.6.1.14 The overall frequency of accidental initiation during transportation is 7.90E-10 per truck-route-km per year as presented in Table 14.16. This value is considered as conservative as speed control will be implemented within the site during the onsite transport of explosives and the traffic within the site should not be heavy as only one truck will be allowed in the site at any given time. Hence, no reduction factors will be considered regarding the probability of fire following a vehicle crash and impact initiation in crash.

14.6.1.15 Since the transport length within the tunnel will vary due to different entry, the average transport length was assumed half the total length for all deliveries. This approach are also adopted in STC STW EIA. The calculated frequency for onsite transportation is shown in Table 14.14.

Table 14.14 Frequency of higher than expected vibration and air overpressure due to onsite transport of explosives

14.6.2 Overnight Storage of Explosives

14.6.2.1 A generic failure frequency of 1E-4 /year has been adopted for the QRA. This frequency had also been adopted in approved EIA reports for SIL, Hong Kong Section of Guangzhou – Shenzhen – Hong Kong Express Rail Link (AEIAR-143/2009, XRL EIA) and Shatin to Central Link – Tai Wai to Hung Hom Section (AEIAR-167/2012, SCL (TAW-HUH) EIA). Apart from the generic failure, external accidents that caused outside the magazine site but would also induce hazard accidents including the following:

· Explosion during manual transfer from store to contractor’s collection truck;

· Lightning;

· Aircraft crashing;

· Hill fire;

· Earthquake; and

· Escalation (explosion of one magazine storeroom triggers another)

Explosion During Manual Transfer from Overnight Storage to Contractor’s Collection Truck

14.6.2.2 Transfer of explosives from magazine site to contractor’s collection truck would be carried out by hand and no tools are involved. Thus there is no significant cause of explosives mishandling specific to the Project magazine site as compared to international practice and assumed to be covered in the generic failure frequency.

Table 14.15 Hill Fire Data for Hong Kong

	Area Affected (Ha)	% of Total Country Park Affected
2017-2018	106	0.24%
2018-2019	197	0.44%
2019-2020	425	0.96%
2020-2021	660	1.49%

14.6.2.6 However, considering that the explosive magazine site design, fire resistance materials such as bricks, cement rendering and steel doors and the ground surface is to be constructed of concrete or stone to prevent fire ingress to the explosives as well as the land within the compound will be cleared of vegetation to remove combustible materials, the chance of explosives being initiated due to hill / vegetation fire is considered to be negligible. Thus, the generic explosion frequency is considered to have included hill fire scenarios.

Earthquake

14.6.2.7 The generic failure frequency adopted is based on historical incidents that include earthquakes in their cause of failure. Since Hong Kong is not at disproportionate risk from earthquakes compared to similar explosives magazines worldwide (Hong Kong is approximate 600km away from the nearest Circum-Pacific Seismic Belt which runs through Japan, Taiwan and the Philippines), it is considered that it is not necessary to address the failure due to earthquake separately.

Escalation

14.6.2.8 It is not considered possible that an explosion within one magazine store will directly initiate an explosion within an adjacent store (i.e. leading to mass explosion). However, the ground vibration induced may damage the adjacent stores and leads to subsequent explosion. Ground vibration distance can be calculated as below^{^[4]}:

Where	A	is the vibration threshold (mm/s) = 229mm/s
	K	is rock constant = 1200
	Q	is the mass of explosive detonated of each storage = 400 TNT eqv. kg
	R	is the distance between the blast and measuring point (m)
	d	is charge exponent = 0.5
	b	attenuation exponent = 1.22

14.6.2.9 The distance of ground vibration threshold generated from the proposed magazine site is only about 11m while the separation distance between the two stores is 18m which is higher than the distance of ground vibration threshold generated. Hence the possibility of explosives within adjacent stores being initiated is negligible.

Other Site Specific Considerations

14.6.2.10 Since HKMEC is about 160m from the proposed magazine site, its operation may cause impact to the magazine. However, the model aircrafts operating from the HKMEC are too light, and carry too little fuel, to cause any consequence on impact. This conclusion was also drawn from the XRL EIA which has the same location of magazine site and operation of the club.

14.6.3 Transport of Explosives

14.6.3.1 Deflagration or detonation explosion may be induced during the transportation of explosives from the proposed magazine to the construction sites. The QRA study from WIL EIA has identified the causes of potential accidental explosion during transportation.

14.6.3.2 Spontaneous fire (non-crash fire), fire after a vehicle crash (crash fire) and impact initiation in crash (crash impact) can cause accidental explosion, while spontaneous explosion may happen if the cargo load contains ‘unsafe explosives’. The causes for initiating accidental explosions are summarized below:

· Non-crash fire:

This cause category includes any explosion instance where the explosive load has been subject to thermal stimulus which is not the result of a vehicle collision. Events in this category, not only include instances where the explosive load is directly engulfed in the fire but also events where thermal stimulus occurs by ways of heat conduction and convection;

· Crash fire:

This cause category is similar to the non-crash fire category but only concerns fires resulting from a vehicle collision; and

· Crash impact:

This cause category includes all instances of vehicle collisions with a sufficient energy to significantly affect the stability of the explosives and which could have the potential to cause an accidental explosion.

· Spontaneous explosion (‘Unsafe Explosive’):

This cause category includes explosions resulting from breach of regulations caused by badly packaged, manufactured and/or ‘out-of-specification’ explosives during normal transport conditions.

14.6.3.3 The transport of explosives relating to commercial and non-commercial activities in port has first been assessed in the study published by Advisory Committee on Dangerous Substances (ACDS, 1995). The basic event frequencies extracted from the study of ACDS was then adjusted in the DNV studies to address the risk induced by the transport of commercial explosives by Mines Division trucks. The adjusted frequencies from DNV study for transport of explosives in trucks operated from the magazine to construction sites had been widely used in different approved EIA studies such as WIL EIA, XRL EIA, SIL EIA and STC STW EIA. Some minor modifications for the frequencies were made based on the explosives’ properties, vehicle impact frequencies and the design features of the explosives carrying vehicles.

14.6.3.4 The fault trees and event trees are updated with the latest traffic in The Annual Traffic Census 2021. The fault trees are shown in Appendix 14.6 and summarized as below:

Table 14.16 Overall Frequencies of Transport of Explosives

Item	Expressway (/route/km/year)	Non-expressway (/route/km/year)
Explosive Load Initiation Due to Impact (incorporated at frequency of “Contractor Truck Explosion Frequency”)	1.46e-12	9.57e-12
Contractor Truck Explosion Frequency per Truck per km	6.76e-10	7.90e-10
Adopted frequency
Two deliveries per day^[^1]	4.94e-7	5.77e-7

Note:

[1] Excavation of a tunnel by drill and blast is a cyclic procedure and according to the latest blasting design, the typical cycle times of 12 hours, 16 hours or 24 hours are commonly adopting. By assuming the worst-case scenario, cycle time of 12 hours is assumed for drill and blast. With this cycle time, maximum of 2 blasts per day can be conducted.

14.6.4 Domino Effect of Town Gas Underground High Pressure Pipeline

14.6.4.1 As discussed in Section 14.3.2, there is a high pressure pipeline running along San Tin Highway and Yuen Long Highway. According to Electrical and Mechanical Services Department (EMSD)’s Guidance Note on Quantitative Risk Assessment Study for High Pressure Town Gas Installations in Hong Kong (HP Guidance), the failure frequency of underground high pressure pipeline is 1e-5 /km/year. The event outcome frequency of fireball and jet fire is 1.73e-6 /km/year (Appendix 14.8). These outcomes would trigger failure of explosives. The alignment of the pipeline which is overlapping with the transport route is shown in Diagram 14.5.

A map of a road

Description automatically generated

Diagram 14.5 Alignment of HP Pipeline overlapping with transport route (North)

14.6.4.2 The travel speed of explosive truck is about 50 km/hr and the interface section is about 9 km long. The explosives vehicles would only be present within the interface section with 11 minutes. Time fraction of an explosive truck within the interface section is about 2.05e-5 /year or 2.28e-6 /km/year. The domino effect of underground high pressure pipeline would be about 3.95e-12 /km/year which is about 2 orders lower than accidental explosion during transport as discussed above and therefore is not further considered in this assessment.

14.7 Consequence Analysis

14.7.1 Overview

14.7.1.1 The damage from bulk explosions are mostly contributed by the blast effects, while for small detonations, fragmentation is the most notable effect and only need to consider thermal radiation in low speed deflagrations.

14.7.1.2 When exposed to blast effects, people may result into three modes of injury which are primary, secondary and tertiary effects. The information related to different levels of effects are summarised in Table 14.17.

Table 14.17 Mechanisms of Blast Injury

Category	Characteristics	Body Part Affected	Types of Injuries
Primary Hazards	Unique to high-order explosives, results from the impact of the over-pressurization wave with body surfaces.	Gas filled structures are most susceptible i.e. lungs, gastrointestinal tract, and middle ear	- Blast lung (pulmonary barotrauma) - Tympanic membrane rupture and middle ear damage - Abdominal hemorrhage and perforation - Globe (eye) rupture - Concussion (Traumatic Brain Injury without physical signs of head injury)
Secondary Hazards	Results from flying debris and bomb fragments	Any body part may be affected	- Penetrating ballistic (fragmentation) or blunt injuries -Eye penetration (can be occult)
Tertiary Hazards	Results from individuals being thrown by the blast wind	Any body part may be affected	- Fracture and traumatic amputation - Closed and open brain injury

Note:

[1] Reference from Explosions and Blast Injuries: A Primer for Clinicians published by Centers for Disease Control and Prevention (U.S.).

14.7.2 Transport and Storage of Explosives

14.7.2.1 Hazardous events would induce impact to both property and people and they would be exhibited in the following ways:

· Blast and pressure wave;

· Flying fragments or missiles;

· Thermal radiation; and

· Ground shock.

Physical Effect Modelling

Blast and Pressure Wave for Explosion

14.7.2.2 Consequence analysis is based on the UK Explosive Storage and Transport Committee (ESTC) which considers all the effects associated with an above ground explosion including, fireball, overpressure, flying debris, broken glass, structure damage, etc. The probability of fatality of can be estimated by ^[1]:

Indoor:

Outdoor:

Where	P	is the probability of fatality. Distance to 1%, 3%, 10%, 50% and 90% of fatality would be adopted for QRA
	S	=R/Q^1/3
	R	is the impact distance (m), i.e. the consequence
	Q	is explosives charge rate (TNT eqv. kg)

Note:

[1] Reference from XRL EIA Study.

14.7.2.3 The indoor consequence model will apply to population in vehicles or buildings, while the outdoor consequence model will apply to pedestrians.

14.7.2.4 The distance to 1%, 3%, 10%, 50% and 90% fatality contours are used in the modelling.

Flying Fragments or Missiles

14.7.2.5 As discussed above, the ESTC model has already considered the impact from flying debris, so no separate model for debris is considered.

Thermal Radiation

14.7.2.6 As the explosives initiate, thermal radiation will be released from the fireball generated from the explosion. There are only a few published models in the literature related to high explosive fireballs or fireballs induced from cartidged emulsion detonation. Models that are available describe the fireball duration and its diameter based on TNT or similar explosives such as nitroglycerine and PETN. In this assessment, it is assumed that the fireball correlations are applicable to cartridged emulsion containing ANFO and aluminum powder.

14.7.2.7 The diameter and duration of a fireball of explosives can be determined as the equation below. As discussed, the maximum charge rate of transport is 200 TNT eqv. kg, i.e. influence zone/radius is 10.2m, and the duration is 1.8s.

^[1]

Where

is the diameter of fireball (m)

is explosives charge rate (TNT eqv. kg)

t_d

is the duration of the fireball (s)

Note:

[1] Reference from Process Industries: Hazard Identification (Lees, 1996).

14.7.2.8 For the largest explosive mass of 400 TNT eqv. kg (initiation of an entire store contents), the fireball radius is calculated to be 12.9m and duration is 2.2 seconds.

14.7.2.9 Surface emissive power (Ef) can be calculated by the equation below.

^[1]

Where

f_s

is the fraction of heat that is radiated, a conservative value of 0.4 is taken in accordance with XRL EIA

∆H_r

Is the heat released from the explosives (kJ/kg)

Note:

[1] Reference from WIL EIA Study.

14.7.2.10 The surface emissive power of fireball for 200 TNT eqv. kg explosives is about 140kW/m².

14.7.2.11 According to “Methods of approximation and determination of human vulnerability for offshore major accident hazard assessment” by HSE UK, thermal radiation dose of a certain time can be calculated by the following equation and the suggested thermal dose of 1%, 50% and 100% fatality are 1000, 2000 and 3200 thermal dose unit (tdu) respectively. Thermal radiation dose can be calculated as below:

^[1]

Where

is incident thermal flux (kW/m²)

Is time of exposure (s)

Note:

[1] Reference from Process Industries: Hazard Identification (Lees, 1996).

14.7.2.12 For the exposure duration of 1.8s, the incident thermal flux calculated are 117, 182 and 279 kW/m² for 1%, 50% and 100% fatality respectively. When compared with the surface emissive power of 140kW/m², these levels of thermal flux will only be realized when in very close proximity to the fireball. As the size of fireball radius is only 10.2m, it can be concluded that the fireball would not induce off-site impact.

14.7.2.13 The same method has been applied for storage of explosives, i.e. 400 TNT eqv. kg storage capacity per magazine, total 800 TNT eqv. kg capacity. For the exposure duration of 2.8s, the incident thermal flux calculated are 83, 128 and 198 kW/m² for 1%, 50% and 100% fatality respectively. As the size of fireball radius is only 16.2m and the nearest residential house is about 300m away, the fireball would not induce off-site impact. Therefore, hazards from fireball are not further considered in this assessment.

Ground Shock

14.7.2.14 Some slopes are identified along the transport route of explosives and there is a chance that an accidental detonation of the explosives can trigger a landslide or a boulder fall. This kind of incidents is identified as a secondary hazard.

14.7.2.15 The transportation and storage of explosives will be carried out above-ground while the use of explosives will be performed underground. The pressure wave induced from above-ground explosion will be lower than that of underground due to less confined space. Therefore, the consequence induced by above-ground explosion is considered less significant compared to the risk induced by the overpressure wave and the fragments produced by the explosion.

14.7.2.16 It can be calculated by the following equation:

^[1]

Where	A	Predicted particle velocity in mm/s
	K	A ‘rock constant’, assumed to be 200
	Q	Maximum charge weight per delay interval in kilograms
	R	Distance in meters between the blast and the measuring point
	d	Charge exponent, assumed to be 0.5
	b	Attenuation exponent, assumed to be 1.22

Note:

[1] Reference from Geoguide 4 – Guide to Cavern Engineering (CEDD, 2018).

Secondary Hazards

Impact on buildings

14.7.2.17 As mentioned before, the nearest building is around 250m away from the magazine and this separation distance is substantially exceeds the 1% fatality distance. Furthermore, the magazine site is not within the CZ of any PHIs and is not near to any other vulnerable risk receptors. Location of the nearest building structure is shown in Diagram 14.6.

Aerial view of a landscape

Description automatically generated

Diagram 14.6 Location of Hong Kong Model Engineering Club (HKMEC)

Impact on Slope and Boulders

14.7.2.18 There are some slopes identified along the transport route of explosives. A landslide or a boulder fall may be triggered by the explosion on an explosives carrying vehicle. The findings from WIL EIA suggested that any landslide or boulder fall would only impact the same area along that road that was already affected by the primary explosion consequences. Since no significant additionally fatality would occur, secondary hazards regarding slope and boulders are not further considered.

14.7.2.19 On the other hand, there are some natural terrains near to the proposed magazine site. It is possible that an explosion inside the storage of the magazine would trigger a landslide or a boulder fall, but the landslide or boulder fall event would only impact in the area that is close to the magazine site which was already affected by the primary explosion consequences. Therefore, no significant additional fatality would occur, so secondary hazard is not further considered.

Impact on High Pressure Underground Town Gas Transmission Pipelines

14.7.2.20 As mentioned in Section 14.2.9, there is a HP underground town gas transmission pipeline running along San Tin Highway and Yuen Long Highway.

14.7.2.21 Leakage or rupture of a gas pipeline can be induced by a higher than expected ground vibration from an accidental explosion or during the blasting process. The typical maximum allowable PPV for town gas pipelines is 25mm/s PPV and it is considered that this level of PPV would not cause significant damage to the pipeline.

14.7.2.22 Although around 9km of the pipeline is under the transport route of the explosives, it is located below ground so there is no hazardous from thermal or air blast pressure effects. Moreover, there would be no shockwave transmitted into the ground as the accidental detonation would occur above ground. Therefore, the gas transmission pipeline would be able to hold up a ground vibration up to 25mm/s safely without causing any hazards.

14.7.3 Use of Explosives

Primary Hazards

Ground Shock/ Vibrations Generated by Rock Excavation using Explosives

14.7.3.1 As discussed in Section 14.6.1, use of explosives is carried out underground which may induce the hazards posed by the overpressure wave and debris generated by the explosion.

14.7.3.2 Secondary hazards such as building failure and slope failure may be led by excessive ground shock, while tertiary hazards such as landslide and rupture of town gas high pressure pipelines may be further induced by secondary hazards.

14.7.3.3 Ground vibration induced by blasting generally occurs as a cyclic wave motion within the ground. This creates movement of the ground that can be measured as velocity, acceleration or displacement, and at different frequencies.

14.7.3.4 The effects of ground vibration due to blasting would be assessed based on the formula from the United States Bureau of Mines, and the recommended value of rock transmission constant and attenuation exponent from Mines Division of CEDD (Li and Ng, 1992). The local vibration attenuation constants K=644 and b=1.22 are used for an initial assessment when predicting vibrations and for producing vibration contours in blasting assessment reports. These constants are based on the upper 84% confidence level. However, for a more conservative approach, the rock constant K is considered as 1200 which is the upper limit selected from GEO Guide No.4.

14.7.3.5 The vibrations that result from a blast may be calculated using an equation of the form:

Where	PPV	Peak Particle Velocity (mm/s)
	K	is rock transmission constant which is 1200
	R	is distance between blasting point and measuring point (m)
	W	is maximum charge weight per delay (TNT eqv. kg)
	B	is attenuation exponent which is 1.22

Note:

[1] Reference from XRL EIA Study.

14.7.3.6 This formula allows a prediction of the effects of ground vibration due to blasting. When combined with an assessment of the safe vibration level for any affected sensitive receivers, it allows an estimate of the MIC that would not exceed the prescribed limits.

14.7.3.7 Peak Particle Velocity Criteria (PPVc) for different features (i.e. building, slopes, boulders) are discussed from Section 14.7.3.9 to Section 14.7.3.43.

Ground Shock/ Vibrations Generated during Transport of Explosives within the Access Tunnel

14.7.3.8 The methodology to evaluate the ground shock due to detonation of full load of explosives within the access tunnel is the same as Section 14.7.1.16 while the value of K is assumed to be 200 to represent the “decoupling” of explosives during transport in the underground tunnel.

Secondary Hazards

Effect on Building

14.7.3.9 According to Geoguide 4, the maximum vibration limits for buildings is 25mm/s to prevent cosmetic damage. Although the value for the peak velocity of 25mm/s has been used for many years, the PPV that induces significant structural damage and results in potential fatalities is also required for the purpose of this assessment.

14.7.3.10 Blasting Vibrations and Their Effects on Structures from the US Bureau of Mines Bulletin 656 has analyzed the blasting results obtained in Sweden and has concluded the damage level of a building with different PPVs. The results obtained from the report are summarized in the table below:

Table 14.18 Damage Level due to Ground Vibration

14.7.3.11 Apart from the report from the US Bureau of Mines Bulletin 656, Explosives Safety Standards (Nicholls, Johnson, & Duvall, 1971) has also reviewed the maximum particle velocity induced in the ground shall not exceed 229mm/s or 9.0 in/s in strong rock for the protection of residential buildings against significant structural damage by ground shock.

14.7.3.12 Criteria adopted for building risk assessment are summarized as below:

· PPV = 229mm/s – Building structural collapse threshold

· PPV = 100mm/s – Object fall threshold

14.7.3.13 The above criteria are considered as conservative as buildings will collapse only when a peak particle velocity is significantly larger than the assumed threshold limit which is 229mm/s.

14.7.3.14 When the PPV level reached 100mm/s which is the object fall threshold, it is assumed that the population within a building will have 1% of fatality level due to vibration causing falling objects which has also been adopted in STC STW EIA and WIL EIA.

14.7.3.15 Ground vibration may cause object fall or building structural collapse and cause fatality. Criteria of building are listed below and influence zone are summarized in Table 14.19.

Table 14.19 Influence Zones of Ground Vibration for Buildings

PPVc (mm/s)	Influence zone (m)
	At blast face						Transport from tunnel portal to blast face (200 TNT eqv. kg)
	1MIC (10 TNT eqv. kg)	2MIC (20 TNT eqv. kg)	3MIC (30 TNT eqv. kg)	4MIC (40 TNT eqv. kg)	5MIC (50 TNT eqv. kg)	6MIC (60 TNT eqv. kg)
229	12	17	21	25	27	30	13
100	24	34	42	48	54	59	25

Building Collapse Models for Explosion/ Earthquake

14.7.3.16 To estimate the number of fatalities due to falling objects, different assumptions are required such as the number of objects with the potential to fall, weight and size of those objects and the probability of fatality when a person is hit. However, the probability of objects falling due to ground vibration at a particularly low threshold value of 100mm/s is hard to predict as there are different uncertain factors such as the condition of building and presence of temporary or unauthorized structures.

14.7.3.17 The building vulnerability models for partial collapse would be adopted in this assessment which also has been used in WIL EIA and STC STW EIA. The fatalities caused by partial collapse are mainly because of the collapse of roofs, ceilings and walls which are considered as the most serious types of falling objects. These type of falling objects may cause more than 1 fatality.

14.7.3.18 A review of building damage vulnerability models for partial building collapse/damage has been carried and summarized by WIL EIA. It has concluded that the fatality rates vary from 0.01% to 1.5%, so 1% fatality rate resulting from falling objects is considered as conservative .

14.7.3.19 However, considering the types of building in this QRA, objects with the potential to fall are assumed to be 1m² large. Based on the maximum population density along the transport route of 0.015 person/m² found in this QRA, the resulting number of fatalities due to an object falling is taken as one for a conservative approach.

Effect on Slopes

14.7.3.20 Different registered geotechnical features have different vibration limits due to their individual features, so the following sections will discuss the methods of assessment to define the vibration limit for the different geotechnical features.

14.7.3.21 According to CEDD’s GEO Technical Guidance Note No. 28 New Control Framework for Soil Slopes Subjected to Blasting Vibrations (TGN 28), PPV limit of slopes that pose ineligible risk-to-life is 25mm/s of Consequence-to-life (CTL) Categories 1 and 2 slopes. For CTL Category 3, an allowable PPV of 25mm/s is normally adopted to any slopes with this category.

14.7.3.22 Although PPV of 25mm/s is the standard and prescribed allowable PPV for the existing slopes, the vibration limits for registered geotechnical features are different for each individual feature. Therefore, 90mm/s is adopted as the PPV limit for slopes.

14.7.3.23 For any slope for which it is proposed to adopt the use of the prescriptive PPV during the detailed stage, visual inspection will be carried out to confirm there are no signs of distress or instability, or any other stability concerns. Those guidance criteria have been used in this Report.

14.7.3.24 The analysis of the effects of vibration on the stability of slopes is based on the guidelines detailed in GEO Report No. 15 (GEO, 1992). The critical Peak Particle Velocity (PPVc) corresponding to the maximum vibration is calculated using the following equation as stipulated in GEO Guidance documents which is considered to be a conservative estimate of the actual expected strength:

Where	K_c	is the critical acceleration at which the slope has a factor of safety of 1.0 against failure
	g	is the acceleration due to gravity (m/s²)
	ω	is the circular frequency of the ground motion (2πf)
	K_a	is the magnification factor

14.7.3.25 The circular frequency of the ground motion(ω) is related to the frequency of vibration (f). Unlike earthquake ground motions, blasting vibration is characterized by short duration high frequency pulses, which according to Mines Division’s records have a frequency content ranging typically from 30 to 100 Hz (GEO, 1992). As suggestion from GEO Report No.15, an input vibration frequency of 30 Hz will result in the lowest PPV_c and hence the most critical situation. Therefore, the case of f equal to 30 Hz is adopted in the following analyses for simplicity.

14.7.3.26 The value of Kc is obtained from stability analysis of the slopes to achieve a minimum pseudo-static FOS as detailed in Table 14.20 and corresponding to different categories of CTL of the slopes, which is in line with the current GEO practice.

Table 14.20 Summary of Adopted Pseudo-Static FOS

Consequence-To-Life Category	Adopted Pseudo-Static FOS
Cat 1	1.1
Cat 2	1.0
Cat 3	1.0

14.7.3.27 To determine the vibration level required to lead to failure of slopes due to earthquakes in Hong Kong, a formula based on Sarma 1975 as referred in GEO Report No.15 is provided for calculating slope movement is as follow:

Where	X_m	is slope movement
	C	is function of the slope geometry and generally is a value near unity
	A_m	is peak acceleration
	T	is dominant period of the ground motion
	A_c	is critical acceleration required to cause sliding

14.7.3.28 For blast observations, the dominant period (T) is about 1/30 seconds with peak ground acceleration in mm/s^s is about 670 times the PPV in mm/s which means that the peak acceleration for a PPV of 60mm/s is about 4g or 40,000 mm/s^s. Therefore, the above formula can be rewritten as:

14.7.3.29 However, as the formula is obtained from earthquake data which mainly consisted of several low frequency pulses instead of a singular high frequency pulse due to detonation of explosives, a factor of 0.25 is applied into the above equation to calculate slope movement for explosives detonation as a typical earthquake consists of at least 4 separate peaks while explosives movement mainly contains one. The modified Sarma equation is as below:

14.7.3.30 STC STW EIA has also derived a formula for calculate the shear displacement of slope based on Sarma equation as below:

Where	Xm	is shear displacement (mm)
		20mm shear displacement has 0.01% chance of slope failure
		50mm shear displacement has 10% chance of slope failure
		100mm shear displacement has 50% chance of slope failure
		200mm shear displacement has 100% chance of slope failure

Table 14.21 Influence Zones of Ground Vibration for Slopes

PPVc (mm/s)	Influence zone (m)
	At blast face						Transport from tunnel portal to blast face (200 TNT eqv. kg)
	1MIC (10 TNT eqv. kg)	2MIC (20 TNT eqv. kg)	3MIC (30 TNT eqv. kg)	4MIC (40 TNT eqv. kg)	5MIC (50 TNT eqv. kg)	6MIC (60 TNT eqv. kg)
90	26	37	46	53	59	65	27

14.7.3.31 The criteria have been used to determine the criteria for the failure of slopes based on the amount of shear displacement or slope movement are:

· 20mm shear displacement or slope movement causes a 0.01% chance of slope failure

· 50 mm shear displacement leading to a 10% chance of slope failure

· 100mm shear displacement leading to a 50% chance of slope failure

· 200mm shear displacement leading to a 100% chance of slope failure

All slopes would receive a shear displacement are less than 20mm. For conservative approach, 0.01% chance has been adopted.

Effect on Nature Terrains and Boulders

14.7.3.32 Landslide of nature terrains and boulders fall may occur during blasting. The Critical Peak Particle Velocity (PPVc) of a boulder will be calculated to estimate the limit of PPV that a boulder can tolerate without falling.

14.7.3.33 According to GEO Report No.15, PPVc at which the block will be driven to a state whereby peak shear stress is developed at the rock joint, can be shown to be given by:

14.7.3.34 In terms of the initial static factor of safety :

Where	g	is acceleration due to gravity (9.8m/s²)
	δp	is joint displacement at peak stress
	β	is joint sip angle (30^o)
	Fs	is initial static factor of safety (2)

14.7.3.35 A sensitivity analysis approach is adopted to calculate the PPV limit of boulders that may be resting on the natural terrain as rock boulders can exist in various locations of the natural terrain. Conservative rock parameters and critical angle of natural terrain are assumed in the analysis and the calculate PPV limit of boulders is 90mm/s.

14.7.3.36 Rock boulders ranging from 1m to 5m in size are assessed for their critical vibration level to initiate movement. Based on the observed natural terrain slope angle, a global factor of safety of 2 is applied to the calculated vibration limit to assign the allowable PPV of rock boulder.

14.7.3.37 Boulder survey will be carried out and the assessment of specific boulder hazard will be undertaken for all areas of natural terrains within the 5mm/s vibration contour zone. For those areas where existing boulder survey is available, the risk of instability will be individually assessed if the boulders are resting on slope larger than 30°. After the individual assessment of the boulders, those boulders identified as having potential instability will be stabilized or protective measures will be installed before the commencement of blasting.

14.7.3.38 According to the GEO reported landslide inventory, there was no landslide incidents related to failure of natural terrain within the hillside catchments affected by the blasting works. The only reported landslide incident related to natural terrain was beyond the blasting influence zone.

14.7.3.39 The residual risk of natural terrain landslide due to blasting is usually low with the ground surface vibration due to the blasting limited to 25mm/s, provided that no blasting would be carried out during periods of high rainfall. In fact, no blasting will be permitted during the periods of Black / Red rainstorm warnings, or Typhoon Signal T3 or higher.

14.7.3.40 Conservative rock parameters and critical angle of natural terrain, boulder size is 5m are assumed which are also adopted in STC STW EIA. The calculated PPVc is 90mm/s. Boulders are assumed to have 1% chance to fall when it experiences a ground vibration greater than PPVc calculated. This potentially exists for the errors during transport from tunnel portal to blast face.

Table 14.22 Influence Zone of Ground Vibration for Natural Terrains and Boulders

PPVc (mm/s)	Influence zone (m)
	At blast face						Transport from tunnel portal to blast face (200 TNT eqv. kg)
	1MIC (10 TNT eqv. kg)	2MIC (20 TNT eqv. kg)	3MIC (30 TNT eqv. kg)	4MIC (40 TNT eqv. kg)	5MIC (50 TNT eqv. kg)	6MIC (60 TNT eqv. kg)
25	76	107	131	151	169	185	78
90	26	37	46	53	59	65	27

Effect on Town Gas Underground High Pressure Pipeline

14.7.3.41 A gas pipeline may experience leakage or rupture due to a higher than expected ground vibration from an accidental explosion or during the blasting process. In according with STC STW EIA, the PPVc of high pressure pipeline is 25 mm/s. It is also conservatively assumed that 25mm/s PPV leads to a 1% probability of significant damage to a pipe upon ignition and cause fatality.

14.7.3.42 Different probability of cause of fatality due to different levels of PPV are also listed as below:

· 25 mm/s PPV (i.e. damage threshold in blast design) leads to a 1% probability of significant damage to a pipe upon ignition and cause fatality

· 62.5 mm/s PPV (i.e. 2.5 times the 1% probability of damage) leads to a 10% probability of significant damage to a pipe upon ignition and cause fatality

· 125 mm/s PPV (i.e. 5 times the 1% probability of damage) leads to a 50% probability of significant damage to a pipe upon ignition and cause fatality

· 250 mm/s PPV (i.e. 10 times the 1% probability of damage) leads to a 100% probability of significant damage to a pipe upon ignition and cause fatality

Table 14.23 Influence Zone of Ground Vibration for High Pressure Pipeline

PPVc (mm/s)	Influence zone (m)
	At blast face						Transport from tunnel portal to blast face (200 TNT eqv. kg)
	1MIC (10 TNT eqv. kg)	2MIC (20 TNT eqv. kg)	3MIC (30 TNT eqv. kg)	4MIC (40 TNT eqv. kg)	5MIC (50 TNT eqv. kg)	6MIC (60 TNT eqv. kg)
25	76	107	131	151	169	185	78
62.5	36	50	62	71	80	87	37
125	20	29	35	40	45	49	21
250	11	16	20	23	26	28	12

14.7.3.43 The nearest blast face to the high pressure pipeline is about 180m and the influence zone of causing failure of high pressure pipeline is 203m. During the transportation of explosives from tunnel portal to blast face, about 50m of the transportation route is within the influence zone which might cause failure to the high pressure pipeline. As discussed in Table 14.15, the failure frequency of non-expressway is about 4.95e-7/route/km/year, thus the total failure frequency due to ground vibration during use of explosives is only 2.47e-10 /year. It is therefore not further considered in this assessment.

Tertiary Hazards

Landslide Consequence

14.7.3.44 Under the GEO Report No.81 Slope Failures along BRIL Roads: Quantitative Risk Assessment and Ranking, a landslide consequence classification system was published and it provides an equation for the estimation of the number of fatalities:

Where	W	is the width of the landslide plus an adjustment for effective stopping distance
	F	is the frequency of passing passenger, which may be taken as the project of the AADT and the average number of people in a vehicle
	P	is the probability of death due to being caught in the landslide
	E	is the extent of the landslide equivalent to the number of lanes affected
	A	is an adjustment factor for proportion of normal road usage at the time of the landslide; and
	V	is the speed of vehicles.

14.7.3.45 The following assumptions are made for the above equation:

· Based on the road conditions linking to the magazine and the Project site, the average vehicle speed is assumed to be 30 miles/hr (i.e. 48 km/hr). The vehicle speed is not particularly sensitive to the calculation of N as the effect will be largely compensated by the effective stopping distance.

· A stopping distance of around 23m is assumed based on UK Highway Code data for a vehicle speed of 30 miles/hr (i.e. 48 km/hr) and it has already included the reaction time.

· The probability of death due to landslides is given in Table 14.24 which is obtained from GEO Report No.81. It has developed a consequence model and has published papers on this subject. The statistics from the past has shown that the assumptions are reasonable and this model also has been applied to several studies regarding landslides in Hong Kong.

Table 14.24 Probability of Fatality due to Landslide

Proximity of Slope	Probability of Death
Lane nearest to slope	0.8
2^nd lane away from slope	0.6
3^rd lane away from slope	0.4

· For the failure of retaining wall that causes the collapse of a road, the probability of death is assumed to be 1 for the lanes affected.

· Parameter A can be 0.82 to account for the fact that landslides are most likely to occur during heavy rainfall, but in this project, the value of A is assumed to be 1 as the possible slope failure is caused by detonation of explosives.

· The value of N should be increased by 25% which is an adjustment factor applied to the calculation to account for the additional risk due to footpath adjacent to the road and it is recommended in the GEO Report No.81.

· At the same time, a lower factor than that recommended for major transportation routes is considered more appropriate as the footpath along the transportation route in this Project is comparatively remote. Therefore, the calculated N value is increased by 10% to account for pedestrians.

14.7.3.46 The travel distance of landslide debris is affected by the mechanism of its failure. For instance, a landslide induced by rainfall would be expected to travel further than the one caused by blasting because soil and rock under liquid manner tends to travel further away. Hence, the travel distance for rainfall induced landslides is based on the inclination of 15° to 30°. For the travel angle of a typical rain induced landslide involves a landslide volume less than 2000m³, it generally ranges from 30° to 40° which is stated in the GEO Report No.81.It is assumed that a landslide caused with detonation of explosives will result in a travel angle of 30° due to conservative approach.

14.7.3.47 The relationship of shadow/ travel angle and run out distance is illustrated by the following diagram.

Diagram 14.7 Run Out Distance

14.7.3.48 By assuming the slope is a triangular volume, the run out distance for the landslide can be approximated by the equation:

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Description automatically generated

Where	L	is the run out distance in m
	V	is the slip volume in m^3;and
	W	is the slip width in m

Boulder Fall Consequence

14.7.3.49 The consequence of boulder fall is according to the methodology introduced in the GEO Report No.81.The probability of a moving vehicle hit by a falling rock with a diameter greater than 150mm is based on the fraction of the road occupied by the vehicle which is defined as

Where	AADT is the annual average daily traffic
	Length of the vehicle is assumed to be 5m
	Average vehicle speed is assumed to be 30 miles/hr (i.e. 48 km/hr); and
	Conversion factors for unit is 24,000

14.7.3.50 The above equation is then modified to calculate the probability of a pedestrian getting hit by a falling rock with a diameter greater than 150mm as below:

A black text on a white background

Description automatically generated

Where	Number of pedestrians per day is obtained by site survey
	Width of a person is assumed to be 1m
	Average walking speed is assumed to be 5 km/hr; and
	Conversion factors for unit is 24,000

14.7.3.51 The probability that a rock hits a vehicle or a pedestrian is then given by:

^Nrf

Where

Nrf

is the frequency of rock fall per year

14.7.3.52 It is assumed that the probability of loss of life of an occupant given a vehicle is hit by a rock is 0.2. The probability may be affected by the size of the rock, the number of occupants within the vehicle and the construction of vehicle.

14.7.3.53 Moreover, the stopping distance of the vehicle can also affect the consequence of a vehicle hitting a falling boulder. The value of stopping distance can then be replaced as the average length of the vehicle and a probability of fatality to an occupant is assumed to be 0.1.

14.7.3.54 With reference to WIL EIA and STC STW EIA, it was suggested that the fatality of pedestrians hit by falling boulders is 100%.

14.7.3.55 Since several buildings were found near potential boulders, the affected population are calculated by the proportion of the area of a boulder to the floor area of the buildings as shown in the following equation:

14.7.3.56 It is assumed that the fatality of an occupant given a building is hit by a rock is 20% and it is referenced from the probability of loss of life of an occupant inside a New Territories house hit by a boulder given in “Territory Wide Quantitative Risk Assessment of Boulder Fall Hazards: Stage 2 Final Report.

14.7.4 R esults of Consequence Analysis

Use of Explosives

Ground Vibration Effect on Buildings due to Errors in Blast Face

14.7.4.1 Since both the building structural element collapse threshold (PPV = 229mm/s) and the falling threshold (PPV = 100mm/s) for accidental explosion up to 6MIC during the construction of access tunnels and underground tunnel are not received by any of the surrounding buildings. Therefore, no further assessment is required.

Ground Vibration Effect on Slopes due to Errors in Blast Face

14.7.4.2 Slopes are identified for further assessment based on the screening criteria of PPV=90mm/s during the construction of project.

14.7.4.3 None of the surrounding slope features was identified to receive a PPV level that would cause potential failure during construction.

Ground Vibration Effect due to Accidental Detonation of Explosives during Transport

14.7.4.4 For the accidental detonation of full load of explosives within the tunnel whilst transferring explosives to the appropriate blast site, neither the predicted ground vibrations of the surrounding buildings nor the slope features exceed their damage thresholds. Therefore, no further assessment is required.

Boulders fall due to Higher than Expected Ground Vibration

14.7.4.5 The type of boulders considered are:

· In-situ Boulders: In-situ boulders are those boulders which have not been displaced since their formation. In-situ boulders include rock outcrops and corestones; and

· Transported Boulders: Transported boulders comprise talus or colluvial boulders that have come to rest in the past at a particular location, and may or may not be unstable depending upon the circumstance of their locations, e.g. degree of embedment, local slope angle, etc.

14.7.4.6 It is assumed that boulders will have 1% chance to fall when it experiences a ground vibration greater than 90mm/s which has been adopted by WIL EIA and STC STW EIA. It may occur during the construction of the project or accidental detonation of explosives during transport within tunnels.

14.7.4.7 Boulder falls frequency and probability of the falling boulders hitting a vehicle or a person are calculated. The results and expected fatalities for boulder fall due to errors in blast faces during the construction of tunnel or accidental detonation of explosives during transport within tunnels are summarized in Table 14.25.

Table 14.25 Boulder Fall Frequencies for accidental initiation of explosives from 2MIC to 6MIC due to errors in Blast Faces

Scenario/Street Name	Scenario Frequency	Expected Fatality (N)
2MIC detonated at the same time
Pedestrian Pavements / Minor Roads near Wang Ping Shan South Road	2.54E-06	1
Pedestrian Pavements / Minor Roads near Wah Shing Tsuen	4.82E-07	1
3MIC detonated at the same time
Pedestrian Pavements / Minor Roads near Wang Ping Shan South Road	2.18E-08	1
Pedestrian Pavements / Minor Roads near Wah Shing Tsuen	4.13E-09	1
4MIC detonated at the same time
Pedestrian Pavements / Minor Roads near Wang Ping Shan South Road	2.26E-10	1
Pedestrian Pavements / Minor Roads near Wah Shing Tsuen	4.30E-11	1
5MIC detonated at the same time
Pedestrian Pavements / Minor Roads near Wang Ping Shan South Road	2.26E-10	1
Pedestrian Pavements / Minor Roads near Wah Shing Tsuen	4.30E-11	1
6MIC detonated at the same time
Pedestrian Pavements / Minor Roads near Wang Ping Shan South Road	2.26E-10	1
Pedestrian Pavements / Minor Roads near Wah Shing Tsuen	4.30E-11	1

Transport and Storage of Explosives

Impacts on Slopes and Boulders

14.7.4.8 There are some slopes along the transport route and near the temporary explosive magazine site at Tai Shu Ha (Yuen Long). There is a possibility that an explosion on road vehicle may trigger a landslide or a boulder fall. This is regarded as a secondary hazard.

14.7.4.9 The impact of this hazard in terms of potential consequences was evaluated using the approach adopted in the WIL study (ERM, 2008). It was found that any landslide and boulder fall event will impact the same area along the road that is already affected by the primary explosion consequences. Hence, no significant additional fatality is expected.

14.7.4.10 The consequence results for each transport and storage scenario are summarized in Table 14.26.

14.7.4.11 According to the latest design, the total amount of explosives stored at the magazine site is 800 TNT eqv. kg (400 TNT eqv. kg storage capacity per store); the quantity of explosives of each trip is about 100 – 160 TNT eqv. kg, and the explosives charge and will be increased to 200 TNT eqv. kg. for large blast face. It is therefore assumed as the maximum transportation rate is 200 TNT eqv. kg. This 200 TNT eqv. kg. is also the amount of full load of explosives in one contractor truck on access road from delivery point to tunnel portal of use of explosives.

14.7.4.12 The proposed explosives magazine is located around 240m away from the nearest building structure which has greatly exceed the 1% fatality distance. Therefore, no significant risk of fatality due to explosives storage is expected.

Table 14.26 Consequence of Use, Storage and Transport of Explosives

Scenario	Fatality probability for Explosives	Impact distance (m)
Scenario	Fatality probability for Explosives	Indoor	Outdoor
Storage of explosive (400 TNT eqv. kg)	90%	23	19
	50%	27	19
	10%	40	21
	3%	53	23
	1%	70	24
Transport of explosives/ Use of explosives (deliver point to tunnel portal) (200 TNT eqv. kg)	90%	18	15
	50%	21	15
	10%	31	17
	3%	42	18
	1%	55	19

Note:

[1] Distances are rounded up to the nearest integer

14.7.5 Consideration of Cumulative Impacts

14.7.5.1 As discussed previously, AT WTW was delisted from the PHI Registers prior to the construction commencement. Hence, there would not be any cumulative hazard-to-life impacts with the use of explosives inside the Drill-&-Blast tunnel sections.

14.7.5.2 It is noted that the Government is implementing a new town at Ngau Tam Mei. As all the drill-&-blast works would be completed prior to the population intake, there would not be any cumulative hazard-to-life impacts.

14.8 Risk Evaluation

14.8.1.1 Individual risk is the frequency of fatality per individual per year due to the realization of specified hazards and is evaluated by summing the contributions to that risk across a spectrum of incidents which could occur at a particular location.

14.8.1.2 Societal risk is defined as the risk to a group of people due to all hazards arising from a hazardous installation or activity. A cumulative graph of the spectrum of the possible consequences and their frequencies is presented as an FN curve and the acceptability of the results can be judged against the societal risk criterion under the risk guideline.

14.8.1.3 From the above analyses, consequences and their corresponding frequencies for each representative location are summed up for the Whole Project using the risk summation tools in the SAFETI 8.7 software package. By summing up all hazard events, Individual risk as well as Societal risk associated with the identified hazardous scenarios are obtained and compared with the criteria set out in Annex 4 of the EIAO-TM to determine their acceptability.

14.8.2 Individual Risk

14.8.2.1 The individual risk due to use, overnight storage and transport of explosives is shown in Appendix 14.9. For use and transportation of explosives, the maximum level of off-site individual risk does not exceed the criterion of 1e-5 per year. On comparing with the criteria in HKRG, the individual risk is acceptable.

14.8.2.2 For overnight storage of explosives, the 1e-5 per year contour line is beyond the boundary of magazine. However, the impact area is only on woodland areas where there is no continuous presence of people. As a result, there is no member of public will be exposed to an IR of 1e-5 per year, and the actual risk to any individual will be much smaller than 1e-5 per year and is deemed to be acceptable.

14.8.3 Societal Risk

14.8.3.1 Based on the frequency analysis and consequence modelling for different hazard scenarios as discussed in Section 14.7, the Societal Risk Plots, i.e. F-N Curves, (Cumulative Frequency F against number of fatalities N) have been derived and shown in Appendix 14.10.

14.8.3.2 For the use of explosives, the population in the vicinity of the blasting site, i.e. tunnel blasting site, would be mainly affected. Hence, the affected population would be limited as the population nearby are mainly pedestrian road with low-density. Due to the occurrence frequency of use of explosive (see Table 14.13), frequency of 1 fatality is still higher than overnight storge and transport of explosives.

14.8.3.3 For overnight storage and transportation of explosives, the most affected population would be along the transportation routes. Due to the long transportation route and higher population density within the 100m influence zone along the routes, higher fatalities were observed as the vehicles would travel across populated area such as Yuen Long Town Centre. Although transportation of explosives results in higher fatalities, the accumulative frequency is normally lower than the use of explosive. The risk results of lower frequency with higher fatalities slightly enter the “ALARP” region.

14.8.3.4 As seen from Appendix 14.10, cumulative impact is within the “ALARP”, ALARP assessment, i.e. cost-benefit analysis, is therefore conducted to demonstrate the risk as low as reasonably practicable and presented in following sections.

14.8.3.5 Moreover, the presented scenario has already considered the worst case, i.e. 2 blasts/route/day (24-hour working) and 7 working days a week (no holiday). Therefore, the risk under actual circumstances would be further lower.

14.8.4 Potential Loss of Life

14.8.4.1 The Potential Loss of Life (PLL) value is the summation of the product of each f-N pair. The PLL values and the breakdown by time mode are shown in Table 14.27. The higher PLL value of transport of explosives is due to the potential for accidents involving large numbers of fatalities as mentioned in societal risk section above.

Table 14.27 PLL Values

Scenario	PLL Value	PLL (%)
Use of explosives	3.64E-06	12.11%
Transport of Explosives	2.64E-05	87.87%
Overnight Storage of Explosives	7.23E-09	0.02%
Overall	3.00E-05	100%

14.8.5 Uncertainty Analysis

14.8.5.1 The hazard-to-life assessment is based on a number of assumptions as previously highlighted in various sections of this chapter. Uncertainties are discussed in following sections.

Transport of Explosives

Traffic Jam Condition

14.8.5.2 Explosive initiation following a vehicle fire could impact a queuing traffic (half jammed) which has assumed to occur on each lane on either side of the road conservatively. This traffic jam has been adopted in the assessment. This approach was also adopted in XRL EIA and STC STW EIA.

Explosion Consequence Model

14.8.5.3 The ESTC models adopted would be conservative of fatalities when compared to the fatalities in past incidents relating to explosives. In the past five years, i.e. 2017 - 2021, the maximum monthly fatalities of traffic accidents was 23 in Hong Kong^{^[5]}. On the other hand, research studies performed by the HSE indicated that the ESTC models may underpredict the fatalities caused by flying glass in highly built-up areas. However, ESTC models are still the best available model and are widely adopted in approved EIAs.

Intervention of the Explosives Truck Crew

14.8.5.4 As fire extinguishers are provided at the explosives truck, crew of the explosives truck is possible to control the fire developing on the truck before fully develop of the fire. However, given that a fire could fully develop and critical explosive temperature can be reached within a couple of minutes, no credit was given for people to escape as a conservative approach.

Intervention of the Fire Services Department

14.8.5.5 As a fire could fully develop and critical explosive temperature can be reached within a couple of minutes, the fire would be fully developed before the fire brigade arrive. The intervention of the fire brigade is therefore limited. Vehicle occupants and pedestrians near the accident would be easy to evacuate while people in the surrounding buildings would be relatively more difficult to escape. It is therefore that no credit has been given for the intervention of the fire brigade for evacuation of the scene as a conservative approach.

Escape and Evacuation

14.8.5.6 As mentioned in the above paragraph, people nearby would be possible to escape and evacuate from the event to certain extent of some event. However, modeling such escape scenario would only slightly reduce the consequence and the impact on risk would be minimum. As such, no credit was given for people to escape as a conservative approach.

Explosive Initiation under Thermal Stimulus

14.8.5.7 Even the consequences are calculated by the ESTC model, there are some uncertainties associated with the probability of explosion for an explosives load composed of a mix of cartridge emulsion and detonating cords in a fire during transportation. The probability used in this assessment has been based on accident statistics applicable to ANFO which is more sensitive than emulsion and transported in a different manner. In absence of test data, this assumption is on the conservative side.

Use of Explosives

Accident Frequency for Explosives Transfer within Tunnels/Ventilation Shaft and Underground Tunnel

14.8.5.8 During transport of explosives, they can be initiated due to crash fire, non-crash fire and crash impact. Their frequency is calculated based on the accident data on public roads. At the same time, the same frequency has been used for transport within access tunnel/ventilation shaft and underground tunnel to the blast faces, although the crash frequency is expected to be much lower due to speed restrictions inside the tunnel and the absence of other vehicle movements. Therefore, the adopted frequency is considered to be conservative.

Ground Vibration Model

14.8.5.9 It is assumed that when there is more than one blasthole charge being detonated at the same time, the vibration effect will be additive. Nonetheless, because of the delay scatter within the realms of the manufacturing tolerance, direct summation of charge weight would overestimate the predicted vibration, so the consequence assessment is considered as conservative as the vibration effects will be additive in this study.

Frequency of Blast involving more than one MIC

14.8.5.10 The frequency of blast involving more than one MIC has been estimated from failure mode analysis, fault tree analysis, expert judgement and human error analysis.

14.8.5.11 The frequency of 5MIC and 6MIC detonation occurring simultaneously has been conservatively assumed to be the same as 4MIC. Therefore, the FN curve for Use of Explosives does not extend below a frequency of 9E-8 per year.

Impact on Buildings and other Features due to Ground Vibration

14.8.5.12 It is considered as conservative that any building subject to vibration of more than 100 mm/s PPV will experience some damage to non-structural elements like brick walls or lead to objects falling off the building such as advertisement signboards which may cause the chance of fatality. A fatality level of about 1% of the total population inside the building has been assumed.

14.9 ALARP Assessment

14.9.1 Risk Results and Approach to ALARP

14.9.1.1 Once the FN curve falls within the ALARP zone, risk mitigations should be implemented to ensure the risk level is ‘as low as reasonably practicable’.

14.9.1.2 To identify whether the risk mitigations options are ‘practicable’, the components to be considered are the cost of the option and whether the mitigation can be implemented in the Project without affecting the construction programme and the consideration of the cost.

14.9.1.3 After identifying whether the mitigation options are ‘practicable’, the reasonability should also be considered and it is usually reviewing the proportion between the cost of implementing the option and the achieved safety benefits.

14.9.1.4 Risk mitigation measures can be engineered measures, controls in the zones which has the most impact after assessing different hazardous scenarios presented by this Project or operation and procedural controls.

14.9.1.5 The following section presents the approach and the outcome of the ALARP assessment.

14.9.2 Approach to ALARP Assessment

14.9.2.1 In order to select and justify the most suitable risk mitigation, ALARP assessment, i.e. a cost-benefit analysis (CBA), will be undertaken to consider a range of mitigation measures. CBA has been widely used in risk studies to evaluate the cost-effectiveness of various mitigation measures and demonstrate that all reasonably practicable measures have been taken to reduce risks.

14.9.2.2 In this Project, CBA, if needed, would be applied by calculating the implied cost of averting a fatality (ICAF) for various mitigation measures identified. The ICAF value is calculated as follows:

Where

PLL

Potential Loss of Life (PLL) value is the summation of the product of each f-N pair

14.9.2.3 ICAF is a measure of the cost per life saved over the lifetime of the project due to implementation of a particular mitigation measure. It may be compared with the value of life to determine whether a mitigation measure is reasonably practicable to implement, i.e. if ICAF is less than the value of life, then the mitigation measure should be implemented. In this study the value of life is taken as HK$33M, which is the same figure as used in previous risk assessment reports including QRA of STC STW EIA. An aversion factor is taken as 20, as the F-N curve, although in the lower ALARP region of the Risk Guidelines, runs close to the 1000 fatalities cut-off line. The adjusted value of life using the aversion factor of 20 is thus HK$660M. This is the value to measure how much the society is willing to invest to prevent a fatality, where there is potential for an event to cause multiple fatalities.

14.9.2.4 To identify whether the mitigation measures, the Maximum Justifiable Expenditure (MJE) is estimated for determining whether a mitigation measure is justifiable. The value of MJE will be calculated by assuming the risk is reduced to zero while justifiable mitigation measures will be examined by considering its actual reduction in PLL in the calculation of safety benefit. The equation of MJE is as follows:

14.9.2.5 The mitigation measures will be considered as justifiable if the cost is less than the value of MJE and the implementation cost for this option is not more than the calculated safety benefits.

14.9.2.6 The capital and operational costs should only be included as the implementation cost of mitigation measures. Any costs related to design or change of design should be excluded.

14.9.2.7 Some mitigation measures may not be able to quantify the cost-benefits, so a qualitative approach will be used in these cases.

Maximum Justifiable Expenditure

14.9.2.8 The MJE for this Project is calculated with a conservative aversion factor of 20.

MJE

14.9.2.9 Where the overall PLL, i.e. 3.00e-5, is adopted while the design life is 3 years, i.e. the duration of blasting. The MJE calculated is HK$0.06M. The mitigation measure should be potentially justifiable if its cost is less than MJE which is HK$0.06M.

14.9.3 Potential Justifiable Mitigation Measures

14.9.3.1 The approach considered the identification of options pertaining in the following broad categories:

· Options of using alternative methods of construction such as Tunnel Boring Machine (TBM);

· Options of using magazines closer to the construction sites;

· Options of using different explosive types;

· Options of reducing the quantities of explosives to be used;

· Options considering improved design of the explosives carrying vehicle; and

· Options considering better risk management systems and procedures.

Use of Alternative Methods of Construction

14.9.3.2 Using hard rock tunnel boring machines is an option for constructing hard rock tunnel. Since the TBM using in this project can only be used for soft rock and soil, if TBM is chosen to construct the whole tunnel, TBM specially for hard rock tunnel should be procured. However, this type of TBMs require several hundreds of millions of Hong Kong Dollars each which has exceed the MJE a lot.

14.9.3.3 Although the cost for design and change of design is not included, additional work and resources will be required for studying the tunnel profile. Moreover, explosives need to be used to enlarge the circular TBM driven tunnel as the diameter of TBM tunnel is fixed.

14.9.3.4 Apart from tunnelling, use of explosives will still be required for shafts and adits excavation. Moreover, the availability for such TBMs is relatively low in Hong Kong and additional blasting is needed for non-circular sector which may cause several months delay of construction programme.

14.9.3.5 Therefore, this option is not practicable and justifiable on a cost basis.

Use of Magazines Closer to the Construction Sites

14.9.3.6 Amongst the initial proposed list of Magazine sites, only 2 sites were retained as practicable, which is Tai Shu Ha (Yuen Long) and So Kwun Wat.

14.9.3.7 As compared to So Kwun Wat site, Tai Shu Ha (Yuen Long) site is within conservation area while the land availability of So Kwun Wat is unknown as the site may be scheduled for other reasons.

14.9.3.8 Moreover, the transportation route from So Kwun Wat (~24km) is much longer than that from Tai Shu Ha Road West (~11km). In addition, the transportation route from So Kwun Wat would pass through Tuen Mun Town center which involve lots of high-rise buildings, which would greatly increase the risk for transportation of explosives.

14.9.3.9 Therefore, Tai Shu Ha (Yuen Long) site is selected.

Use of Different Explosive Types

14.9.3.10 The type of explosives used in the Project is already considered as the safest type for blasting application, so no safety benefits will be obtained by selecting a different type of explosives.

14.9.3.11 In this project, PETN is used as the detonating cord with a melting point around 140°C. Although there are other detonating cord technologies available such as Research Department explosive (RDX) and High Melting Explosive (HMX), their melting points are slightly higher than that of PETN which may require more time before an explosion occurs following a fire event. However, the extra time required and risk reduction by implementing this mitigation measure would be neglected for the purpose of this assessment.

14.9.3.12 Hence, this option is not considered further.

Use of Smaller Explosives Quantities

14.9.3.13 This Project has already considered the minimum amount of explosives for transportation as it will transport initiating explosives only and the bulk emulsion explosives will be manufactured on site.

14.9.3.14 It is possible to use smaller explosive charges for initiating explosives such as cast boosters and the main component of cast boosters is PETN. Although use of cast boosters can reduce the amount of explosives transported, it has a higher TNT equivalency and it does not eliminate the need for detonating cord.

14.9.3.15 The minimum cost for maximizing the use of cast boosters is around HK$600,000 which is 4 times higher than MJE, the additional cost of utilizing cast boosters would further increase its cost which make this option not justifiable on a cost basis.

14.9.3.16 Apart from its cost, there are only limited suppliers who can provide this material, so the availability of cast boosters is also another limitation causing it not reasonably practicable.

Safer Design of the Explosives Carrying Vehicle

14.9.3.17 The design of the truck has been reviewed to identify potential improvements which can reduce the risk such as preventing the fire spreading to the explosive load. It is assumed that the explosives carrying vehicle has already followed the guideline provided by Mines. For example, an additional vertical fire screen with heat resistance equivalent to 3mm of steel should be installed between the vehicle cabin and the cargo compartment of contractor’s truck.

14.9.3.18 Besides assuring the contractor’s truck has fully complied the requirement of Guidance Note No. GN2 published by Mines. There are also some simple measures can be implemented. For instance, limiting the fuel tank capacity and reducing the combustible load on the explosives by using fire retardant materials wherever possible.

14.9.3.19 Since the safety benefits of these measures are difficult to evaluate quantitatively, they are included in the section regarding good practices (Section 14.9.6).

Reduction of Accident Involvement Frequency

14.9.3.20 The accident involvement frequency of the explosives carrying vehicle can be reduced through the training programme for both the driver and his attendants, regular “toolbox” briefing sessions, implementation of a defensive driving attitude, appropriate driver selection based on good safety record and regular medical checks.

14.9.3.21 The actual implementation of this option is provided in the recommendation section (Section 14.9.6).

Reduction of Fire Involvement Frequency

14.9.3.22 The fire involvement frequency can be reduced by putting better types of fire extinguishers with bigger capacity inside the explosive carrying trucks.

14.9.3.23 Moreover, it can be reduced by providing emergency plans and training to ensure that the suitable fire extinguishers are used and attempt is made to evacuate the area of the incident or securing the explosive load if possible.

14.9.3.24 The actual implementation of this option is provided in the recommendation section (Section 14.9.6).

Summary

14.9.3.25 In summary, most of the options considered for CBA are not practicable after comparing the implementation cost with the MJE, while the remaining options have been recommended as Good Practices Recommendation under Section 14.9.6.

14.9.4 ALARP Assessment Results

14.9.4.1 The evaluation of each option considered is concluded in Table 14.28.

Table 14.28 ALARP Assessment

Mitigation	Practicability	Implementation Cost	ALARP Assessment Result
Use of Alternative Methods of Construction (i.e. TBMs)	Not Practicable	>HK$ 400M	Neither practicable nor justified.
Use of Magazines Closer to the Construction Sites	Not Practicable	-	Closest practicable magazine site to the construction sites has been selected.
Use of Different Explosive Types (Different Types of Detonating Cord)	Pose some limitations	-	Bulk Emulsion explosive manufactured on site has been adopted as the main or `bulk’ blasting explosive to excavate rock by rock blasting to minimize the amount of explosives for transportation.
Use of Smaller Explosives Quantities	Not Practicable	>HK$0.6M	Use of cast boosters is not cost effective. However, due to the risk reduction achieved the use of cast boosters is to be maximized, which is to be encouraged. In the other hand, Project Proponent, i.e. MTRC, would review, on an ongoing basis during the detailed design, tender and construction phases, and implement the use of cast boosters during construction to the maximum extent possible.
Safer Design of the Explosives Carrying Vehicle	Practicable	-	Based on low implementation costs, this mitigation option has been directly incorporated in recommendations (under Section 14.9.6)
Reduction of Accident Involvement Frequency	Practicable	-	Based on low implementation costs, this mitigation option has been directly incorporated in recommendations (under Section 14.9.6)
Reduction of Fire Involvement	Practicable	-	Based on low implementation costs, this mitigation option has been directly incorporated in recommendations (under Section 14.9.6)

14.9.5 Recommendations

Recommendations for Meeting the ALARP Requirements

14.9.5.1 Recommendations are made for implementation in order to meet the EIAO-TM requirements:

· The truck should be designed and improved to reduce the amount of combustibles in the cabin. The fuel carried in the fuel tank should also be minimized to reduce the duration of any fire.

· The accident frequency of the explosive truck should be minimized through the implementation of a defensive driving attitude and a dedicated training programme for both driver and his attendants which includes regular briefing sessions. Moreover, drivers should be selected based on good safety record and providing regular medical checks for the driver.

· The required quantity of explosives should only be transported for a particular blast to avoid any unused explosives send back to the magazine.

· The contractor should combine the explosive deliveries for a given work area as far as practicable.

· A minimum headway between two consecutive truck convoys of 10 mins should be maintained whenever practicable.

· To reduce the explosive truck fire involvement frequency, a better emergency response and training should be implemented to ensure adequate fire extinguishers are used and attempt is made to evacuate the area of the incident or securing the explosive load if possible. All explosive vehicles should also be equipped with bigger capacity AFFF-type extinguishers.

General Recommendations

14.9.5.2 Each blasting activities including storage and transport of explosives should be supervised and audited by competent site staff to ensure strict compliance with the blasting permit conditions.

14.9.5.3 For the storage and transport of explosives, the recommendation listed below should also be considered:

· The security plan should address different alert security level to reduce opportunity for arson or deliberate initiation of explosives.

· Emergency plan like magazine operation manual should be developed to address uncontrolled ire in magazine area and during transport of explosives.

· Adverse weather working guideline should be developed to clearly define procedure for transport of explosives during thunderstorm.

14.9.6 Good Practices Recommended

Good Practices to be Implemented for Use of Explosives

14.9.6.1 While the risk levels associated with the use of explosives for this Project is minimized as much as practicable, it is prudent that the Contractor implements all the good practices to minimize the hazard-to-life even further and ensure that any blasting carried out will not adversely affect services, utilities, slopes, retaining walls, buildings and structures through ground vibrations or other effects. A summary of these good practices is given below for reference. The good practice could make reference to the latest guideline including, but not limited to, Practice Note for Authorized Persons and Registered Structural Engineers – Control of Blasting (APP-72) by Buildings Department (BD). Following are some Typical Items regarding Good Practices to Blasting Works extracted from the APP-72, for detail, please reference to the latest APP-72 by BD.

· Carry out checking of the registered contractor’s blasting method statement.

· Check (including both document and site checks) and satisfy, for each blast, that the registered contractor’s blast design and precautionary measures comply with the plans approved by the Building Authority and the blasting permit requirements.

· Verify on site that the ground conditions and geology are as stated or assumed in the blasting assessment, and that the provisions in the method statement and the preventive, protective and precautionary measures are adequate for the conditions as encountered on site.

· Ensure that the preventive measures, if required, have been properly carried out prior to commencement of the blasting works.

· Prepare regular reports with records of the condition of the site, sensitive receivers, adjacent grounds, structures and services etc. after each phase of blasting operation and completion of related works.

· Inspect the construction of preventive works, if required, for the sensitive receivers.

· Inspect the provision and installation of all necessary protective and precautionary measures prior to each blast, in accordance with the blast design.

· Monitor the site operations and working methods to ensure that they meet the safety requirements set out in the blasting permit.

· Inspect and monitor the conditions of all sensitive receivers regularly and carry out reviews of the quality of monitoring for the sensitive receivers before and after each blast.

Good Practices to be Implemented for Magazine Site

14.9.6.2 While the risk levels associated with the overnight storage of explosives for this Project is minimized as much as practicable that the Contractor implements all the good practices to minimize the hazard-to-life even further and ensure that overnight store of explosives will not adversely affect services, utilities, slopes, retaining walls, buildings and structures through ground vibrations or other effects. A summary of these good practices is given below for reference.

14.9.6.3 The good practice could be made reference to the latest guideline including, but not limited to, “Guidance Note No. GN 8 How to Apply for a Mode A Store Licence for Storage of Blasting Explosives” by CEDD which has mentioned in Section 14.2.5.

14.9.6.4 The design, operation and maintenance of the magazine should follow Mines Division guidelines and industry best practice. Some other good practices listed below can also be implemented:

· To ensure the undertaken work activities during the operation of the magazine are properly controlled, a suitable work control system such as an operational manual including Permit-to-Work system should be introduced.

· Good house-keeping should be maintained within the magazine to ensure that combustible materials are not allow to accumulate.

· The magazine store should not have any open drains, traps, pits or pocket which any molten ammonium nitrate could flow and be confined in the even of a fire.

· Regular checking of the magazine building should be conducted for water seepage through the roof, walls or floor.

· Caked explosives shall be disposed of in an appropriate manner.

· Permission to remain the secured fenced off magazine store area shall not be given to explosives delivery vehicles.

· Speed limit control should be implemented within the magazine area in order to reduce the risk of a vehicle impact or incident within the magazine area.

Good Practices to be Implemented for Transport of Explosives

14.9.6.5 Contractor should implement all good practices to minimize the hazard-to-life even further and ensure that transport of explosives will not result in adverse impact. A summary of these good practices is given below for reference. The good practice could be made reference to the latest guideline including, but not limited to “Guidance Note No. GN 2 Approval of an Explosives Delivery Vehicle” as mentioned in Section 14.2.5 and “Guidance Note No. GN 3 Application and Handling of a Removal Permit” by CEDD:

· Typical Removal Permit Conditions

o A placard as specified in the section 80 of Dangerous Goods (Control) Regulation must be displayed in a conspicuous place on the vehicle carrying explosives.

o No unnecessary waiting or parking of the vehicle is permitted at any place along the transportation route.

o The vehicle carrying the explosives is prohibited from passing through any tunnel on a public road.

o Except with the permission in writing of the Authority, the vehicle must not carry more than 200kg net explosives content of explosives at any one time. The vehicle for moving explosives shall be a licensed vehicle equipped with effective fire-extinguishers and maintained in good running conditions at all time.

o The vehicle shall use the intended route of transportation specified in the application for this conveyance permit.

o The vehicle with explosives on board is prohibited from refuelling at any fuel station.

o Conveyance of blasting explosives or entertainment fireworks shall only be undertaken by the vehicle/s and driver/s approved by the Authority and in the presence of a Resident Explosives Supervisor and a Shot Firer or a Fireworks Master/Assistant. When carrying explosives/fireworks, the approved vehicle/s shall display the correct dangerous goods placards and warning signs.

o Explosives and detonators must be conveyed on separate vehicles or in separate compartments on the vehicle. Electric detonators must be carried in an approved and properly labelled wooden container.

o The Permittee is required to input the actual date and time of the use of this Permit in Centralised Explosives Licensing and Management System (CELIMS) after the conveyance of the explosives as soon as reasonably practicable. If the Permit is unused before its expiry date, the Permittee is also required to provide reason(s) for not using the Permit in CELIMS.

· Safer Design of the Explosives Carrying Vehicle

o Fire screen could be installed between the cabin and the load of the vehicle to reduce the chance of fire escalating to the load and cause explosion.

· Reduction of Accident Involvement Frequency

o Different administrative measures can be implemented to reduce the accident involvement frequency and increase the situational awareness of the driver during the transportation of explosives.

o Administrative measures can include “Tool-box” talk training regarding the safety precautions when transporting explosives.

o Ensuring that the detonators and the cartridged emulsion are under good conditions and well-intact within their packaging before transporting.

o Recruiting experienced driver with good safety record and checking their health condition in a regular basis.

· Reduction of Fire Involvement

o Carrying fire extinguishers or other active fire protection devices with higher standard and higher capacity onboard of the Explosives Carrying Vehicle.

o Create a contingency plan with consideration of different scenarios that may occur, such as the action that the driver should take in case of fire near the Explosives Carrying Vehicle in the middle of traffic jam.

o Regulations for the drivers should be set, such as hot work should be prohibited when handling explosives to avoid any sources of ignition.

o Working Guidelines should be developed to provide clear instructions to the drivers when encountering different situations like extreme weather.

14.10 Conclusion

14.10.1.1 A QRA has been carried out to evaluate the risk induced from the storage, transport and use of explosives during construction of the Project.

14.10.1.2 A review regarding AT WTW is conducted and according to the latest information available, AT WTW has been delisted and will no longer classified as a Potentially Hazardous Installations. Therefore, the hazard assessment for it is no longer required as there would not be any hazard-to-life concerns.

14.10.1.3 Within the entire alignment of about 10.7km, only a 1.1km long section would be constructed using Drill-&-Blast and Mined tunnelling including approximately 35m and 170m long underground tunnels which would require the use of explosives. To ensure timely delivery to blasting site and maintain the construction process, a temporary explosive magazine site at Tai Shu Ha (Yuen Long) for overnight storage of explosives is required. As temporary explosive magazine is needed, transport of explosives is also required.

14.10.1.4 The magazine site at Tai Shu Ha (Yuen Long) would follow the relevant design requirements in terms of sufficient separation distances and the design of the storage facilities. Review suggests that the associated risk for the operation of the temporary magazine site would be insignificant.

14.10.1.5 For the use of explosives at the Drill-and-Blast tunnel sections at North Portal and the underground tunnel at Middle Opening and South Portal, given that the proper design and maintenance of the blasting face and provision of blast door or cover, together with the fact that the blasting would be connected inside the tunnel section and with the blast cover shut, the associated risk would be well within the acceptable region.

14.10.1.6 For the storage and transportation risk, a preliminary review found that there is mainly low-density population within the 100m influence zones. However, since the number of buildings is noticeable, QRA was conducted and the risks for Overnight Storage of Explosives and Transport of Explosives slightly enter the “ALARP” region.

14.10.1.7 The assessment results for cumulative risk from storage, transportation and use of explosives show that the criterion of Annex 4 of the EIAO-TM for Individual Risk are complied. For the societal risk, although the societal risk for use of explosives entered the “ACCEPTABLE” region, the result for storage and transportation of explosives slightly entered the “ALARP” region. Hence, the societal risk lies within the “ALARP” region.

14.10.1.8 It is noted that the cumulative risk level would slightly fall into the “ALARP” zone at around 7 to 9 fatalities. Since the cumulative risk is within the “ALARP” region, mitigation measures are required to reduce the level to ‘as low as reasonably practicable’. ALARP assessment, i.e. Cost-Benefit-Analysis (CBA), is conducted in this QRA to study the cost-effectiveness of different measures. Justified mitigation measures have been recommended.

14.10.1.9 Nevertheless, it is still recommended to implement all the best practices to minimize the risk even further.

14.11 References

Schultz, E., Wintenberger, E., & Shepherd, J. (1999, October). Investigation of deflagration to detonation transition for application to pulse detonation engine ignition systems. In Proceedings of the 16th JANNAF Propulsion Symposium (Vol. 1, pp. 175-202). Chemical Propulsion Information Agency.

Nolan, D. P. (2014). Handbook of fire and explosion protection engineering principles: for oil, gas, chemical and related facilities. William Andrew.

AECOM. (2014). Sha Tin Cavern Treatment Works: Hazard to Life Assessment for Storage and Transport of Explosives.

Merrifield, R., & Moreton, P. A. (1998). An examination of the major-accident record for explosives manufacturing and storage in the UK. Journal of hazardous materials, 63(2-3), 107-118.

Chief Fire and Rescue Adviser. (2008). Generic Risk Assessment 5.7: Incidents Involving Explosives. Retrieved from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/14910/gra-5-7-pt1.pdf.

Centers for Disease Control and Prevention (U.S.). (2003). Explosions and Blast Injuries: A Primer for Clinicians. Retrieved from https://stacks.cdc.gov/view/cdc/28987.

Nicholls, H. R., Johnson, C. F., & Duvall, W. I. (1971). Blasting vibrations and their effects on structures (p. 656). Washington: US Government Printers.

Ammunition, D. O. D. (2004). Explosives Safety Standards. DoD Directive.

Sarma, S. K. (1975). Seismic stability of earth dams and embankments. Geotechnique, 25(4), 743-761.

Geotechnical Engineering Office. (1992). Assessment of Stability of Slopes Subjected to Blasting Vibration. GEO Report No. 15. Retrieved from https://www.cedd.gov.hk/filemanager/eng/content_166/er15.pdf

Dangerous Goods Ordinance (Cap. 295). (1971).

CEDD. (2022). Guidance Note No.GN 8 How to Apply for a Mode A Licence for Storage of Schedule 1 Dangerous Goods (Blasting Explosives).

CEDD. (2022). Guidance Note No.GN 2 Approval of an Explosive Delivery Vehicle.

CEDD. (2022). Guidance Note No.GN 2 Application and Handling of a Removal Permit.

ERM-Hong Kong. (2001). EIA Study of West Island Line (WIL): Hazard to Life Assessment for the Transport, Storage and Use of Explosives.

Planning Department. (2019). 2019-based Territorial and Employment Data Matrix.

Census and Statistics Department. (2021). 2021 Population Census.

Transport Department. (2022). The Annual Traffic Census 2021.

ERM-Hong Kong. (2009). EIA Study of Hong Kong Section of Guangzhou – Shenzhen – Hong Kong Express Rail Link (XRL): Hazard to Life Assessment

Merrifield, R., & Moreton, P. A. (1998). An examination of the major-accident record for explosives manufacturing and storage in the UK. Journal of hazardous materials, 63(2-3), 107-118.

CEDD. (2018). Geoguide 4 – Guide to Cavern Engineering.

Puhakka T. & Tamrock (Firm). (1997). Underground drilling and loading handbook. Tamrock.

ERM-Hong Kong. (2010). EIA Study of South Island Line (East) (SIL): Hazard to Life Assessment for Explosives Storage and Transport.

ERM-Hong Kong. (2012). EIA Study of Shatin to Central link – Tai Wai to Hung Hom Section (SCL): Hazard to Life Assessment for the Transport, Storage and Use of Explosives.

AFCE. (2018). Department Annual Report 2017-2018.

AFCE. (2019). Department Annual Report 2018-2019.

AFCE. (2020). Department Annual Report 2019-2020.

AFCE. (2021). Department Annual Report 2020-2021.

HSE. (2013). Methods of approximation and determination of human vulnerability for offshore major accident hazard assessment.

Centers for Disease Control and Prevention (U.S.). (2003). Explosions and blast injuries : a primer for clinicians.

Li, U. K., & Ng, S. Y. (1992, April). Prediction of blast vibration and current practice of measurement in Hong Kong. In Proceedings of the Conference Asia Pacific—Quarrying the Rim, Hong Kong (pp. 119-135).

Nicholls, H. R., Johnson, C. F., & Duvall, W. I. (1971). Blasting vibrations and their effects on structures (p. 656). Washington: US Government Printers.

CEDD. (2010). New Control Framework for Soil Slopes Subjected to Blasting Vibrations.

Wong, H. N., & Pang, P. L. R. (1992). Assessment of stability of slopes subjected to blasting vibration. Geotechnical Engineering Office, Civil Engineering Department, Hong Kong.

ERM-Hong Kong. (1999). Slope Failures along BRIL Roads: Quantitative Risk Assessment and Ranking.

Lees, F. P. (1996). Loss prevention. Process Industries: Hazard Identification, Assessment, and Control, 2nd ed., Butterworth-Heinemann, Oxford, GB.

[1] According to UK HSE’s Explosives Regulations 2014, the external separation distances are considered based on the quantity of explosives for each individual store where store means a building, enclosed area or metal structure in which explosives are, or are to be, stored. The storage for the proposed magazine site used in this Project would be 400 kg per store.

^{^[2]}The distance of the entrance of HKMEC to the magazine is about 200m. The population on the site will generally be about 100 during weekday events, 200 at weekends and public holidays. HKMEC also occasionally hold 5 or 6 major events attracting a crowd of around 1,000 people. The populated area, however, being more than 200m from the magazine, is outside the area of interest, i.e. the separation distance for the magazine.

[3] Reference from Guidance Note on Quantitative Risk Assessment Study for High Pressure Town Gas Installations in Hong Kong published by EMSD.

[4] Reference from Geoguide 4 – Guide to Cavern Engineering published by GEO, CEDD.

[5] According to Table 3 – Monthly Figures for Traffic Accidents of “Traffic Report 2017” to “Traffic Report 2021” by Traffic Branch Headquarters, Hong Kong Police Force

Damage Level	Peak Particle Velocity, mm/s (in/s)
No noticeable damage	70 (2.8)
Fine cracking and fall of plaster	110 (4.3)
Cracking	160 (6.3)
Serious cracking	231 (9.1)

Figure No.	Title
C1603/C/NOL/ACM/M61/301	Location of Au Tau Water Treatment Works
C1603/C/NOL/ACM/M61/302	Blasting Locations and the Connection Adits

Appendix 14.1	Site Selection for Explosive Magazine Site
Appendix 14.2	Routes for Transportation of Explosives
Appendix 14.3	Information of Au Tau Water Treatment Works
Appendix 14.4	Population Data Adopted
Appendix 14.5	Geotechnical Features Considered
Appendix 14.6	Fault Tree Analysis
Appendix 14.7	Calculation of Failure Rates for Aircrafts Crashing
Appendix 14.8	Event Outcome Frequency of Fireball and Jet Fire
Appendix 14.9	Individual Risk Contours
Appendix 14.10	Societal Risk Results

Location	Initial Freq. (/km/year)	No. of Deliveries	Road Length (km)	Frequency (/year)
North Portal	7.90E-10	730	0.4	1.15E-7
Middle Opening	7.90E-10	730	0.4	1.15E-7
South Portal	7.90E-10	730	0.4	1.15E-7

14 HAZARD TO LIFE

a) Data / Information Collection and Update: relevant data / information essential including population for the hazard to life assessment were collected;

b) Hazard Identification: Identify hazardous scenarios associated with storage, transport and use of explosives;

c) Frequency Estimation: Estimate the frequencies of each hazardous event leading to fatalities with full justification by reviewing historical accident data and previous similar projects;

d) Consequence Analysis: Analyze the consequences of the identified hazardous scenarios;

Lightning

Aircrafts Crashing

Hill Fire

Earthquake

Escalation

Other Site Specific Considerations

Note:

Blast and Pressure Wave for Explosion

Thermal Radiation

Ground Shock/ Vibrations Generated by Rock Excavation using Explosives

Ground Shock/ Vibrations Generated during Transport of Explosives within the Access Tunnel

Effect on Building

[1] Distances are rounded up to the nearest integer

Explosion Consequence Model

Intervention of the Explosives Truck Crew

Intervention of the Fire Services Department

Escape and Evacuation

Explosive Initiation under Thermal Stimulus