Construction of Site Reclamation Works for the Black Point Location

B1 Construction of Site Reclamation Works

B1.1 General

In order to construct the proposed LNG Receiving Terminal facility it is necessary to form at least 20-25ha of land area. Where the available land area is insufficient it is necessary to undertake reclamation to make up the difference. A comparison of the reclamation requirements for the three different layout options at Black Point is given in the sections below in order to assess the relative merits and demerits in this regard.

At all locations the reclamation areas are expected to be underlain by a significant thickness of compressible marine deposits. Using the partially dredged method these clays will be largely left in place during the reclamation process.

B1.2 Assessment Parameters

In order to create a cost effective and sustainable site formation, a balance between cut and fill quantities is required. A combination of on-shore cutting and off-shore reclamation is typically adopted unless other considerations do not permit this. Generally, for each layout a level platform of +6mPD will be created to be sufficiently above the sea level to reduce environmental impacts from the sea. The formation of the reclamation will involve the filling of significant quantities of soil and rock material which will need to be sourced either from the on-land excavation works or from external sources, depending upon the balance achieved. In order to assess the engineering implications of the off-shore reclamation for each layout option the following assessment parameters have been considered:-

· Area of sea reclaimed;

· Volume of dredging material;

· Volume of filling material and how much is imported;

· Length of coastline affected;

· Length of seawall required;

· Time for dredging and filling and for consolidation; and,

· Ground improvement measures.

B2 Area of Sea Reclaimed

B2.1 Option 1 – Base Case

The Base Case layout is proposed to be constructed partially on land and partially on reclaimed land at the southern end of the Black Point peninsula as shown in Figure 2.1. The on-land site formation works have been considered separately in Annex 2-A-A. The total area to be reclaimed is estimated to be approximately 160 x 10³ m². Available drillholes indicate the Marine Deposits beneath the reclamation area to be approximately 7m in thickness.

B2.2 Option 2 – Full Reclamation

The site area will be provided complete by reclamation at the end of the Black Point peninsula as shown in Figure 2.2. The total area to be reclaimed is estimated to be approximately 190 x 10³ m².

B2.3 Option 3 – Full Excavation

There is no reclamation for this layout option as shown in Figure 2.3.

B3 Volume of Dredging and Filling Materials

B3.1 Option 1 – Base Case

The estimated total volume of dredging and subsequent reclamation fill required to form the terminal area including the seawall are as follows:-

Volume of dredging = 0.63 x 10⁶ m³

Volume of reclamation fill = 2.89 x 10⁶ m³

B3.2 Option 2 – Full Reclamation

The estimated total volume of dredging and subsequent reclamation fill required to form the terminal area including the seawall are as follows:-

Volume of dredging = 0.65 x 10⁶ m³

Volume of reclamation fill = 3.43 x 10⁶ m³

B3.3 Option 3 – Full Excavation

Since there is no reclamation for this layout option, the volume of dredging and reclamation fill required is zero.

B4 Reuse of Excavated Material

For the use of excavated materials within the reclamation refer to Annex 2-A-A.

The reclamation can be formed using the excavated material from the site formation works, which are expected to comprise largely moderately to slightly decomposed granite material. However, in order to achieve the required grading for reclamation standards it will be necessary for the material to undergo primary, secondary and possibly tertiary crushing with associated sorting and mixing off-site at an appropriate stockpile site.

B5 Length of Seawall and Natural Coastline Affected

B5.1 Option 1 – Base Case

The site formation will require a total seawall length of approximately 1,120m to form the boundary of the proposed terminal. A total of approximately 720m of existing coastline, of which approximately 120m are artificial coastline, will be affected by this construction.

B5.2 Option 2 – Full Reclamation

The site formation will require a total seawall length of approximately 1,160m to form the boundary of the proposed terminal. A total of approximately 580m of existing natural coastline will be affected by this construction.

B5.3 Option 3 – Full Excavation

Minimal.

B6 Time for Construction

B6.1 Option 1 – Base Case

It is estimated approximately 12 months will be required to complete the dredging and filling operation for the reclamation works.

B6.2 Option 2 – Full Reclamation

The dredging and filling operation is estimated to be completed in approximately 14 months.

B6.3 Option 3 – Full Excavation

None.

B7 Ground Improvement and Time for Consolidation

Since the marine deposits are largely left in place under the reclamation, ground improvement work will be required in the form of vertical drains plus surcharge pre-loading. This significantly reduces the ongoing creep settlement within the sand fill layer and speed up the consolidation process.

B7.1 Option 1 – Base Case

It is estimated approximately 17 months will be required to complete the surcharging and consolidation process for the reclamation works.

B7.2 Option 2 – Full Reclamation

The surcharging and consolidation process is estimated to be completed in approximately 20 months.

B7.3 Option 3 – Full Excavation

None.

B8 Summary for Site Reclamation Construction

A summary of the parameter values and relative scores derived from the engineering assessment for the site reclamation construction is given in Table B1 below.

Table B1 - Summary for Site Reclamation Construction

Parameter	Option 1 (Base Case)	Option 2 (Full Reclamation)	Option 3 (Full Excavation)
Area of reclamation (10^3m²)	RS = 3 (160)	RS = 2 (190)	RS = 5 (0)
Volume of dredging material (10^6m³)	RS = 3 (0.63)	RS = 2 (0.65)	RS = 5 (0)
Total volume of fill material required (10^6m³)	RS = 3 (2.89)	RS = 1 (3.43)	RS = 5 (0)
Volume of imported fill (sand + rock) (10^6m³)	RS = 3 (1.90)	RS = 1 (3.43)	RS = 5 (0)
Length of natural coastline affected (m)	RS = 3 (600)	RS = 3 (580)	RS = 5 (0)
Length of artificial coastline affected (m)	RS = 3 (120)	RS = 5 (0)	RS = 5 (0)
Length of seawall required (m)	RS = 3 (1120)	RS = 3 (1160)	RS = 5 (0)
Construction time for dredging and filling (months)	RS = 3 (12)	RS = 2 (14)	RS = 5 (0)
Time for consolidation after construction (months)	RS = 3 (17)	RS = 2 (20)	RS = 5 (0)
Need for ground improvement	RS = 3	RS = 2	RS = 5

RS = Relative Score

B9 Scoring for Site Reclamation Construction

Each of the parameters summarised above in Table B1 have been scored in accordance with the procedure described in Section 2.1. The results are shown below in Table B3 for each of the layout options. The table also shows the total score for each layout option derived using the weightings given in Table 2.4.

Table B3 – Scoring for Each Layout Option for Site Reclamation Construction

Parameter	Weight	Option 1 (Base Case)		Option 2 (Full Reclamation)		Option 3 (Full Excavation)
		Score	WS	Score	WS	Score	WS
Area of reclamation	0.10	3	0.30	2	0.20	5	0.50
Volume of dredging material	0.20	3	0.60	2	0.40	5	1.00
Total volume of fill material	0.05	3	0.15	1	0.05	5	0.25
Volume of imported fill	0.20	3	0.60	1	0.20	5	1.00
Length of natural coastline	0.15	3	0.45	3	0.45	5	0.75
Length of artificial coastline	0.05	3	0.15	5	0.25	5	0.25
Length of seawall required	0.10	3	0.30	3	0.30	5	0.50
Construction time for dredging & filling	0.05	3	0.15	2	0.10	5	0.25
Time for consolidation after construction	0.05	3	0.15	2	0.10	5	0.25
Need for ground improvement	0.05	3	0.15	2	0.10	5	0.25
Total Weighted Score			3.00		2.15		5.00
Normalised Score		3.00		2.15		5.00

From the result of the assessment of all parameters for site reclamation construction, Option 3 is the preferred layout.