13.1.1
This project comprises
construction of the following key structures:
-
an approximately 10.5km long drainage tunnel with portals at both ends;
-
35 intake
shafts;
-
adits connecting the main tunnel and the intake
shafts; and
-
an outfall structure
13.1.2
The
main drainage tunnel will be constructed by Tunnel Boring Machine (TBM).
Conventional excavation methods (e.g. raising boring method or reverse
circulation drilling method) will be adopted for construction of the intake
shafts. Drill and blast methods will
be used for excavation of most of the adits.
13.1.3
This section of the report
addresses the issues with regard to the Hazard Assessment as specified in the EIA Study Brief (ESB-070/2001).
13.2 Technical Requirement for Hazard
to Life Assessment
13.2.1
The EIA Study Brief for
this project requires an assessment to be carried out if there is overnight
storage of explosives on site, and the location of which is in close vicinity
of populated areas. The assessment must follow the criteria for evaluating hazard to life as stated in Annexes 4 and 22 of the TM to the EIAO. The hazard assessment needs to address
the following:
(i) Identification of
all hazardous scenarios associated with the transport, storage and use of
explosives for blasting operation;
(ii) Execution of a
Quantitative Risk Assessment expressing population risks in both individual and
societal terms;
(iii) Comparison
of individual risk and societal risks with the Criteria for Evaluating Hazard
to Life as stipulated
in Annex 4 of the TM to the EIAO; and
(iv) Identification and assessment of
practicable and cost-effective risk mitigation measures.
13.3.1
Potential hazards relate to
the storage and use of explosives for the construction of the
adits.
13.3.2
For the adits construction,
drill and blast method will
be adopted for the majority of the works. As the storage of
explosives relates to the extent of the drill and blast component of works, it
is important to review the rate of work, storage/delivery arrangements and the
duration of the works. The blasting works will require about 30 months to
complete. Based on the proposed
construction programme and the blasting frequencies, there will be no requirement for overnight storage of explosive
on site. The delivery of the
explosive will be once per day. The
delivery of explosives from Government Explosives Depots to the blasting site
is controlled by the Explosives Delivery Unit of the Mines Division. Explosives
are classified as Category 1 Dangerous Goods and use of explosives is
controlled under the Dangerous Goods
Ordinance (Chapter 295). Since there will be no
overnight storage of explosive on site, no Quantitative Risk Assessment is
required for this study.
13.4.1
There will be no overnight
storage of explosives for this project. Transportation of explosives to site
for the construction of adit will be undertaken on a daily basis. The contractor is required to destroy
any unused explosives before nightfall.