11.1.1 The EIA Study Brief requires that hazard assessment should be conducted if there is overnight storage of explosives on site due to the proposed SWC project and the location of which is in close vicinity of populated areas or PHI site.
11.1.2 This section gives a brief description of relevant legislation and guidelines, and potential hazard to life in relation to the use of explosives for construction purpose. Relevant precaution measures are addressed. This section concludes the need for hazard assessment for this Study.
11.2 Legislation, Standards, Guidelines and Criteria
General
11.2.1 The following legislation, standards, guidelines and
criteria are relevant to the evaluation of 'Hazard to Life'.
· Dangerous Goods Ordinance (Cap. 295);
· Dangerous Goods (Application and Exemption) Regulations;
· Environmental Impact Assessment Ordinance (Cap. 499.S16); and
· Technical Memorandum on Environmental Impact Assessment (EIAO TM).
Dangerous Goods Ordinance (Cap. 295)
11.2.2 The conveyance of explosives by public roads in HKSAR is governed by the Dangerous Goods Regulations. A removal permit is required for transport on public roads. Also, the road vehicle carrying explosives should be of an approved type. Storage of explosives is governed by the Dangerous Goods (General) Regulations. Under the regulation, a licence is required for storage.
EIAO TM
11.2.3 The requirements for hazard assessment of projects involving the storage, use or transport of dangerous goods are specified in Section 12 and Annex 22 of the EIAO TM. In addition, Annex 4 of the EIAO TM specifies the individual risk guidelines and societal risk guidelines.
Individual Risk
11.2.4 Individual risk is defined as the frequency of fatality per year to a specific individual due to the realisation of specified hazards, with account taken of temporal factors. The maximum level of off site individual risk should not exceed 1 in 100,000 per year, i.e. 1 x 10-5 per year.
Societal Risk
11.2.5 Societal risk is defined as the risk to a group of people due to all hazards arising from a hazardous operation. The simplest measure of societal risk is the Rate of Death or Potential Loss of Life (PLL), which is the predicted equivalent fatalities per year.
11.2.6 Societal risk is also expressed in the form of an F-N curve, which represents the cumulative frequency (F) of all event outcomes leading to N or more fatalities. This representation of societal risk highlights the potential for accidents involving large number of fatalities.
11.2.7 The societal risk guidelines expressed in the form of
F-N curve comprise of three regions:
· Unacceptable region;
· ALARP region where risk is tolerable providing it has been reduced to a level
As Low As Reasonably Practicable; and
· Acceptable region where risk is broadly acceptable.
11.3 Identification and Assessment of Hazard
General
11.3.1 The delivery of explosives from Government Explosives Depots to the blasting site is controlled by the Explosives Delivery Unit of the Mines and Quarries Division. Explosives are classified as Category 1 Dangerous Goods and use of explosives is controlled under the Dangerous Goods Ordinance (Chapter 295).
11.3.2 The types of explosives for blasting operation mainly include bulk explosives and cartridged explosives. Ammonium nitrate and fuel oil mixtures fall in the category of bulk explosives. Cartridged explosives are emulsions or watergel products. Currently, the types of explosives allowed to be used at construction sites are ammonium nitrate based explosives.
11.3.3 In general, the amount of explosives allowed to be stored on site is limited to that required for immediate use. Overnight storage of explosives needs to the approved through the application for licence to store blasting explosives.
11.3.4 When an explosion occurs, a blast wave and scattered fragment will be generated and may cause injury to persons. Transport of explosives may pose potential hazards to persons. Qualified personnel should be responsible for the use of explosives at the construction site. A blasting assessment report is required to detail the protection works. In addition, staff of the Mines and Quarries Division will supervise the blasting operation on site. All safety and security procedures should be implemented to ensure the potential hazards due to the use of explosives on site are minimal.
11.3.5 Minimisation of the amount of explosives to be stored overnight would reduce the potential hazards to persons. This in turns eliminates the hazard to life in terms of overnight storage of explosives on site. When the explosives arrive on site, immediate loading of explosives should be carried out. The storage area should be constructed in accordance with the requirements specified in the Dangerous Goods Regulations. Any requirements specified by the Commissioner of Mines and the Director of Fire Services should also be followed.
11.3.6 For overnight storage of explosives, an approved type of magazine should be erected in the explosive storage area and safety guards approved by police should be employed to ensure that no unauthorized persons could enter the storage area. No open fire and smoking are allowed near the explosive storage area.
11.3.7 With regard to the use of explosives, only qualified personnel should be responsible for the blasting operation on site. Precautions should be undertaken to ensure that the hazards to the nearby villages are minimal. This includes the erection of warning signals including the display of red flags at a radius of > 150 m from the blasting site and beating of gongs for > 5 minutes before the commencement of blast and until the completion of blast. Procedures for handling and disposal of unfired explosives need to be developed, if necessary.
The Need for Hazard Assessment
11.3.8 Under the requirement specified in the EIA Study Brief, hazard assessment is only required if there is overnight storage of explosives and the storage location is in close vicinity of populated areas or PHI site.
11.3.9 The proposed SWC alignments include both the bridge option and tunnel option. The bridge option consists of straight type and s-curve type whilst the tunnel option consists of immersed tube type and drill and blast type. Use of explosives would not be required for the bridge option. It is also likely that explosives would not be required for the immersed tube type tunnel option. Even if explosives are used, the required amount of explosives would be in a small quantity and explosives could be delivered to the site each day to avoid overnight storage on site. The key concern is the drill and blast type tunnel option.
11.3.10 Based on the alignment review results in Section 4, Options A and B (the bridge options) have similar high scores and there is a marked difference in the scores between the bridge options and the tunnel options (Options C and Option D). From the sensitivity test results, although the relative positions of Options A and B in the ranking alternates in the sensitivity tests, the bridge options (A and B) are always higher in ranking than the tunnel options. The s-curve bridge option has been selected as the preferable alignment option.
11.3.11 The engineering study of the s-curve bridge option has determined that explosives would not be required for the construction of the SWC bridge. Therefore, it is concluded that quantitative assessment on the potential risk due to storage, handling and on-site treatment of explosives is not required.
11.4.1 The different alignment options presented in Section 4 conclude the s-curve bridge alignment option is the preferable option. Under the requirement specified in the EIA Study Brief, hazard assessment is only required if there is overnight storage of explosives and the storage location is in close vicinity of populated areas or PHI site. The construction of the s-curve bridge would not involve the use of explosives. Therefore, quantitative assessment on the potential risk due to storage, handling and on-site treatment is not required and hazard to life due to overnight storage of explosives would not be an issue in this Study.