Extension of the Los Mármoles Dock (Arrecife, Lanzarote)
1. Description of the Construction
The Port Authority, after a study carried out in August 2013 ( Attachment number 4: Viability of the Solution Chosen) concluded that for Phase 1, a configuration of the port has been achieved that will guarantee the operational capacity of the current cruise ship dock, which is the extension of the main dock measuring a total length of 440 m, following the orientation and design of Alternative A2 (see Figure 1.1) and the building of a 110 m long dock exempt of any vertical features to the south of the existing Cruise Ship Dock, at 20 m distance, orientated perpendicular to said dock.
In this Project, the work corresponding to the extension of the existing Los Mármoles Dock will be carried out as the main achievement of Phase I. In a later Project, said Phase will be completed with the execution of the exempt dock.
Continuing with the work foreseen in the “Extension of the Los Mármoles Dock”, we hereby proceed to describe the work necessary to be carried out in the project called the “Extension of the Los Mármoles Dock”.
The construction comprises the extension of the current Los Mármoles Dock, following the alignment reflected on the plans according to the studies carried out. This new stretch of dock will be 430.40 metres long, with a draught of -20.00m and 15.50 metres manoeuvring space or turning basin.
The work will begin with the dredging of loose material on the seabed to an average thickness of 2.30 m. until solid seabed is reached, to dump the dredges of the embankment. Sufficient material will be removed to anchor the first caisson at -20.00, keeping the required safety distance. This material will be reused on the embankment of the extension.
The new berthing area will be made of 12 floating caissons in reinforced concrete with square cells filled with granular backfill and 17.50m beam, 33.90 metres length and 23.50 metres draught.
The transition between the current dock and the new extension has been projected with a starting caisson, trapeze- shaped to adapt to the existing dock and the new alignment of the Project. Said caisson will have foundations at the -10.00 level with a 19.75m. length and 24.80m. width and a 13.50m. draught.
The caissons are, as said, 4.40m diameter square cells with 0.25cm thick interior walls. The outer walls are 50 cm thick. The caisson has a 19.50m wide footing and is 90 cm thick.
A berm-ledge has been defined for the 6.00m rubble mound on the land side and 7.55m on the ocean side, starting at the footing and with a 1.50/1 slope. To protect the embankment on the sea side, a 2-ton layer of rubble with an average thickness of 1.82m. as well as a 3 m. wide and 1.80 m high guard block, topping at level -18.20. The berm on the land-side will be protected from the effect of ships’ propellers, by a layer of submerged concrete with an average thickness of 30 cm. The berm on the starting caisson, largest side, will be 12m long and the ocean-side section will be the same in the entire extension.
Before the caissons are anchored, the corresponding levelling of the embankment will be carried out with 40/70 gravel on an average width of 24.50 m. to include the support of the guard block and an average thickness of 50 cm.
Once the caissons have been anchored, the cells will be filled with granular material. To make the filling procedure easier, and since the emerging level of the caissons is +3.50, it has been projected that the filing of the caissons will be 50 cm above this level to protect it from the sea’s effects. This excess will later be removed to carry out the different structures projected.
To carry out the joint seals between the caissons, four tubes of 0.80 cm. diameter fibrocement filled with armoured concrete with rods measuring 12mm every 25 centimetres. The tubes will be placed between the caisson overhangs on both the east and the west side and the resulting gap will be fully filled with non-structural concrete. The rest of the joint gap in the middle of the caisson, will be topped off with rockfill.
The beginning of the construction of the dock wall will be carried out when the caisson is fully in service, in other words, that all cells are filled and the support embankment on the ocean side has been protected. The foundations of the First Phase of the Enlargement of the Los Mármoles Dock will be laid at +3.50 level with an approximate width of 5.15 m. until level +5.25. The second phase will run from level +5.25 with a width of 2.50 m. until level +7.60 where the width will be 1.20 m. The last section of the dock wall will begin at level +7.60 and a width of 2.50 m. and concludes at level +10.00 with a width of 1.20 m. Two batteries of 4 corrugated double-walled polyethylene tubes, two of them 160 mm. diameter and the other 110 mm. diameter, will be embedded into the dock wall with manholes every thirty metres to carry the telephone and lighting services.
Once the dock wall has been constructed, the superstructure may be built. This will comprise a 0.50 m. overhang on the inside face of the caisson, which starts at level +0.50 and widens until it reaches level +1.00 at a width of 0.50 m. The superstructure will be finished off at level +5.20 with a width of 4.725 with the placement of a vault on the edge of the dock. Embedded in the esplanade, two batteries with four tubes of double-walled corrugated polyethylene will be installed: one 160 mm in diameter with manholes every thirty metres. These tubes will be connected by means of interconnections with the ones on the dock wall. Several intersections along the complete length are projected for each utility.
A 250mm diameter cast-iron pipe will be included, installed at the first step to the dock wall following the existing section. Another supply pipe made of 150 mm. diameter PVC-O, which will run parallel to the line of the superstructure. This line will be connected to the main cast-iron line by means of several intersections and this pipe will supply the water outlets.
As future fuel pipes are to be continued following the current section, it will also be necessary to install intersections that will connect the gallery of the dock wall to the edge of the dock to enable the placement of the fuel inlets.
150-ton nominal pull bollards will be installed and cylindrical rubber fenders, as reflected in the plans. The transfer of the present beacon to the end of the new dock is also included as well as the existing current meter.
For lighting, 6 metre posts will be installed every 30 metres at level +7.60 on the dock wall. The section between the superstructure and the dock wall will be paved with a layer of selected paving, approximately 1.20m thick, a 0.25m layer of artificial aggregate and a top layer of 0.32m HP-40, as is explained in the corresponding surface attachment.