Construction of Facility Foundations for the Black Point Location
E1
Construction of Facility Foundations
The terminal structures such as pipe racks, terminal facilities and
buildings are considered to be piled foundation in view of the loadings and
constructability mainly over the reclamation area where they are overlying
thick marine sediments. The LNG
tanks are located within the cut slope areas for which ground bearing raft
foundations are anticipated depending on the suitability of the rock beneath
the formation level.
The jetty extends from the proposed seawalls to the approach channel
for berthing of LNG carriers. The berthing head, trestle, mooring and breasting
dolphins will be constructed on a series of pile caps supported on marine bored
and/or driven piles founded on rock.
The potential access for LNG carriers will be via the waterway entering
the approach channel and turning basin before berthing. Piling for the jetty will be constrained
by the construction limitations due to significant marine traffic in fairways
and restricted areas. These factors
are important in the site assessment and comparison process. Mitigation
measures will be considered to reduce the length of jetty and the noise and
vibrations associated with the pile installation works.
The receiving terminal requires the use of marine access for normal
terminal operation, construction plant, materials and labour during
construction. Sites with
alternative land access will have programme advantages in both construction and
operation stages.
In order to assess the
engineering implications of the marine and on-land installation works at each
of the sites the following assessment parameters have been considered:-
·
Terminal facility
structures piling works;
·
Jetty piling works;
and,
·
Water front access.
E2
Terminal Facility Structure
E2.1
Option 1 – Base Case
The pipe racks and terminal
infrastructures are located on areas of reclamation and these structures will
be piled. Two of the LNG tanks will
be located behind the cut slope and will be supported on a raft foundation on
rock.
E2.2
Option 2 – Full Reclamation
All the LNG tanks, the pipe
racks and terminal infrastructures are located on areas of reclamation and
these structures will be piled.
E2.3
Option 3 – Full Excavation
All the LNG tanks, the pipe
racks and terminal infrastructures are located behind the cut slope and these
structures will be founded directly on rock using pad or raft footings.
E3
Jetty Piling Works
E3.1
Option 1 – Base Case
The estimated length of the
jetty from the proposed seawall is approximately 100m long for berthing of LNG
carriers.
E3.2
Option 2 – Full Reclamation
The estimated length of the
jetty is approximately 100m long for berthing of LNG carriers.
E3.3
Option 3 – Full Excavation
The estimated length of the
jetty is approximately 180m long.
E4
Water Front Access
The
Black Point site has both waterfront and land access will be available for site
formation and piling works.
E5
Summary for Facility Foundation
Construction
A summary of the parameter values and relative scores derived from
the engineering assessment for the facility foundation construction is given in
Table F1 below.
Table E1 - Summary for Facility
Foundation Construction
|
Parameter |
Option 1 |
Option 2 |
Option 3 |
|
Terminal
facility structures piling works |
RS = 3 |
RS = 1 |
RS = 4 |
|
Jetty piling
works |
RS = 3 (100) |
RS = 3 (100) |
RS = 1 (180) |
|
Water front access |
RS = 3 |
RS = 3 |
RS = 3 |
RS = Relative
Score
E6
Scoring for Facility Foundation
Construction
Each of the parameters summarised above in Table E1 have been scored
in accordance with the procedure described in Section 2.1. The results are shown below in Table E2
for each layout option. The table
also shows the total score for each layout option derived using the weightings
given in Table 2.7.
Table E2 – Scoring for Each Layout
Option at Black Point for Facility Foundation Construction
|
Parameter |
Weight |
Option 1 |
Option 2 |
Option 3 |
|||
|
Score |
WS |
Score |
WS |
Score |
WS |
||
|
Terminal
facility structures piling works |
0.3 |
3 |
0.90 |
1 |
0.30 |
4 |
1.20 |
|
Jetty piling
works |
0.5 |
3 |
1.50 |
3 |
1.50 |
1 |
0.50 |
|
Water front access |
0.2 |
3 |
0.60 |
3 |
0.60 |
3 |
0.60 |
|
Total Weighted Score |
|
3.00 |
|
2.40 |
|
2.30 |
|
|
Normalised Score |
5.00 |
4.00 |
3.83 |
||||
From the result of the assessment of all parameters for the construction of the facility foundations, Option 1 is the preferred layout followed by the Option 2 and 3 layouts.