Cable laying and Pile Drilling





I:			*Cable Laying and Pile Drilling for the Current Turbine Project*

In the weeks leading up to mid-November, several dives have been conducted to get some video of the substrate where the route of the cable will go and where the piling for the generator will be installed.


Archipelago marine has done a SIMS towed video. The route they took and the timing of the footage was done according to this Chart.	Pam and Jason from Archipelago Marine do their underwater survey of the location of the Piling Drilling for the Current Energy Project.	Chris Blondeau and Juan Carlos video the substrate at the site of the piling installation, and test the depth of the overburden.
This site was chosen after extensive testing of the current profiles in both channels with the Acoustic Doppler Current Profiler.	The location for the installation is in the current channel between North and Middle Rock, with the typical associations of organisms of the highly current swept areas of the island. Since the depth is 21 meters, there are few macroalgae present.	This area is well away from the locations normally used by members of the diving community.


The current swept area is covered with the typical Metridium senile, Balanaus nubilus, Strongylocentrotus franciscanis community.	The ADCP instrument was installed for a month in this location in the spring of 2005.

Date of work: The installation in November is timed after the nesting and seal pupping season and in the time of the year when the Sea Lions have returned but are concentrated in the area to the East of the docks, on South Rock and on Middle and West Island. The closest population that may be disturbed by the drilling is on North Rock, and part of Middle Rock. In the past that population frequently comes and goes probably because of the fall schedule of blasting by DND on Bentink Island .

Construction Method: A contract has been let by Clean Current for the drilling and installation of the piling to bear the generator to: Fraser River Pile & Dredge Ltd. (FRPD)of Vancouver. A 1 metre hole will be drilled to a depth of 8 metres, (weather permitting) in mid November.

The drilling operation is a closed system. All drill cuttings will be brought to the surface and then processed through a cyclone which will separate the cuttings from the water. The water and entrained air will then be returned to the ocean via a pipe at a depth of approx. 20 ft. All of the cuttings will be collected on a scow that is tied up along side the drilling barge.The cuttings will be taken ashore for disposal.

Equipment

Island Tug operates a large fleet of tugs and barges including one self-propelled cable layer. The principal method of cable handling utilizes one of two powered self-breaking drums. Reel number 1 has a capacity for 80,000 feet of 2-inch diameter cable with a break holding capacity of 200 tons. Reel number 2 has a capacity for 30,000 feet of 2-inch diameter cable with a break holding capacity of 100 tons.

Procedure of Cable Laying - General

Reel number 2 is mounted aboard the cable layer, Georgia Transporter. Cable is transferred from shore storage reels to the ship-mounted reel and transported to the site. Cable is taken ashore at the cable shore-end via a bow mounted adjustable ramp. A bow mounted cable chute is used to deploy the cable while the Georgia Transporter is towed astern. Two GPS systems monitor the surface position and provide feedback via digital charts. Track corrections are implemented through a variety of methods using the Ship’s power, directing the towing vessel or employing side boats. For shallow water lays, the cable tension is not monitored by equipment but by the angle off the bow, with lay and reel speeds corrected as necessary. For deep-water lays, the cable tension is monitored with on deck tension monitoring equipment such as linear tension devices or load cells. Cable weights and water depth information are pre plotted along a planned track in order to adjust for the intended tension at given positions.

Reel number 1 is mounted aboard one of Island’s flat deck barges and used in the same manner as the description above, with the exception that the barge will start and finish on four point moorings.

Chris Blondeau, operations manager, and Garry Fletcher, Ecological Reserve Warden will be available to oversee the environmental concerns. In addition, Pam Thuringer and staff of Archipelago Marine have been contracted to do an ongoing environmental monitoring for the duration of the construction phase of the project.

Copyright

Lester B.Pearson College

Link to the Tidal Current Power Project