Construction of Facility
Foundations for the South Soko
Location
E1 Construction of Facility Foundations
The terminal structures such as pipe racks, terminal facilities and buildings will be mostly supported on ground bearing structures as the area is expected to be underlain by good quality rock. However, where the rock is not present or where filling is undertaken piled foundations will likely be required to reach the rock material beneath, particularly for the heavier structures. 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. During construction, bubble jackets and/or bubble curtain may be considered for the marine piling works, in conjunction with low noise and vibration techniques to reduce the impacts on the surrounding area.
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 definitely 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
· Jetty piling works
· Water front access
E2 Terminal Facility Structure
E2.1 Option 1 – Base Case
The pipe racks and terminal infrastructures are mainly located on areas of cutting and it is likely that these structures will be founded directly on rock using either pad or piled foundations. All three 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
The pipe racks and many of the terminal infrastructures are located on reclaimed land to the west of the existing platform and will therefore be supported on piles. The rest of the terminal infrastructure will be located on areas of cutting and it is likely that these structures will be founded directly on rock using pad or pile foundations. All three LNG tanks will be located within the cut slope and will therefore likely be supported on a raft foundation bearing directly onto rock if the quality is found to be sufficient.
E2.3 Option 3 – SE Jetty
The pipe racks and terminal infrastructures are mainly located on areas of cutting and it is likely that these structures will be founded directly on rock using pile foundations. Two of the LNG tanks will be located behind the cut slope and will be supported on a raft foundation on rock. The third future tank is mainly located on reclamation and will be piled.
E3 Jetty Piling Works
E3.1 Option 1 – Base Case
In order to reduce amount of dredging for the approach channel and turning basin, the estimated length of jetty is about 200m. The structure will be supported on either bored or driven piles. The location of the jetty is close to known marine mammal areas and therefore mitigation measures will be required to reduce the noise impact during marine piling installation. This may significantly slow the rate of progress of the works and is therefore less preferable.
E3.2 Option 2 – Full Reclamation
The option 2 site layout has the same jetty as Option 1 and therefore the impact is the same.
E3.3 Option 3 – SE Jetty
In order to reduce the amount of dredging for the approach channel and turning basin, the estimated length of jetty is about 240m. The structure will be supported on either bored or driven piles. The surrounding waters have been identified as a potentially sensitive location for marine life and therefore mitigation measures will be required to reduce the noise impact during marine piling installation. This may significantly slow the rate of progress of the works and is therefore less preferable.
E4 Water Front Access
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 E1 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 = 3 |
|
Jetty piling
works |
RS = 3 (200) |
RS = 3 (200) |
RS = 2 (240) |
|
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 2.1.3. The results are shown below in Table E2 for each layout option. The table also shows the total score for each layout derived using the weightings given in Table 2.6.
Table E2 – Scoring for Each Layout
Option at
|
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 |
3 |
0.90 |
|
Jetty piling
works length |
0.5 |
3 |
1.50 |
3 |
1.50 |
2 |
1.00 |
|
Water front access |
0.2 |
3 |
0.60 |
3 |
0.60 |
3 |
0.60 |
|
Total Weighted Score |
|
3.00 |
|
2.40 |
|
2.50 |
|
|
Normalised Score |
5.00 |
4.00 |
4.17 |
||||
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 3 and Option 2 layout.