The Marianas Trench

The Marianas Trench is the deepest part of the planet, at over 36,000ft (or 12,000m) and the PPC-1 cable system crosses it to reach Sydney from Guam.

The cable finally reached the seabed at 0625 this morning on 2nd May, some six hours after it left the ship. It reached a final depth of 9440m. At the point that the cable touched down, the ship was a further 26km south in ‘only’ 7000m of water.

This photograph shows two graphs of the seabed; the top one is a side profile and the bottom one charts the slopes and dips in percentage terms.

The Trench is about 175km south of Guam and leaves the Tyco Decisive with another 2100km of cable to lay.

8 comments – Latest by:
  • Matt Whitlock
    Chris, OK. I understand where you're coming from. The cable is designed to land on the seabed at all times. ...
  • Matt Whitlock
    David, Thanks for your comment. The speed of the ship is changed depending on the seabed we're going across. The ...

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Environmental Review at the HDD Site

As the HDD project approaches the finishing line and we prepare for the punch out day, it’s good time to review the overall quality and environmental management aspects of the works that started early September. Brett and John conducted an onsite review with our drilling contractor, Coe Drilling. This involves reviewing the site daily logs and incident reports to ensure the requirements of the site environmental plan have been met, not been met, just met or exceeded. We also took the opportunity to commence the planning for the punch out which we hope will occur before the end of the month.

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Shore End Survey Completion

View of the coral ledge where the cable will land in Madang

From the beaches to each of the Cable Landing Stations in Madang, Guam and Sydney, the shore end surveys scrutinize the beach environments where PIPE’s cable will land.

Engineers have been performing periodic inspections at each of the landing sites to assess changes in environmental conditions such as beach erosion and other external hazards.  The inspections form part of local government permitting requirements.

Where possible, shore end engineers perform their inspections following earthquakes or wild weather to determine any impacts to the integrity of the cable system or changes in the seabed.

Our engineers have been comparing the as-built records against actual inspection data to identify any discrepancies and update changes in shore end cables. Common changes needed to the original drawings are new cable crossings, changes in burial depth due to sand migration, and new cables in shared manholes.

The following are extracts from each of the survey reports.

Extract from the Madang Report:

There are no charted obstructions to the landfall except coral reefs and beach rocks in the vicinity of the area. The area immediately in front of the landfall point is shown on the Admiralty charts as “UNSURVEYED” (approximately up to the 100 meter contour, which is approximately 300 metres offshore).

Extract from the Guam Report:

Minor beach deposits, reef limestone, and alluvium of Holocene age occur along the coastline. These deposits cover a small percentage of the surface of Guam, and may be as much as 70m thick at the mouths of some rivers. The beach deposits are composed of poorly consolidated sediments, mostly calcareous sand and gravel thrown onto beaches by waves but some deposits of volcanic sand can be found where streams drain volcanic uplands. Reef limestone up to 4m thick also occurs locally. Deposits of alluvial clay fill stream valleys and cover the inner parts of coastal lowlands.

Extract from the Sydney Report:

The proposed landfall is situated on a high energy ocean beach in a wide east facing bay. The seabed slopes away relatively sharply to approximately 18 m, approximately 0. 5 nm from shore. The seabed up to this contour is mostly fine to medium grained golden colored sand with 10% to 60% shell. Some reef rock is exposed close to shore towards the northern end of the bay. Due east of the bay, between the 20 and 40 m contour (0.5-1.5 nm from shore) is an expanse of exposed reef rock. There are at least three sandy (medium to coarse grained orange sand with 40% shell) channels. The rocky promontory of Long Reef continues underwater eastwards beyond 3 nm from the coast. The gradient of the seabed beyond the band of exposed reef rock becomes gentler, obtaining a water depth of 50 m at 3 nm from the shore. The seabed composition is coarse sand continuing eastward, gradually blending into fine grained grey colored sand with 5% to 20% mud and 30% to 40% shell.

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  • PIPE International
    Jesse The PIPE team take loads of photos throughout the progress of the project. Visit the Photo Gallery for pics ...
  • Nick Koopalethes
    How will you secure the cable to the coral in Madang? I assume it will be double armoured close to ...

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Core Sampling and Cable Laying

Seabed Sampling

Picture Coutesy of EGS

During the survey EGS took a number of seabed samples for analysis.

The samples are taken by various tools called grabs, gravity corers and vibrocorers.  The samples are analysed and used to establish the soil density, porosity, and calibrate geophysical and geotechnical survey methods for the route.

This analysis is especially important when 1) determining the PPC-1 cable route and 2) for the burial points of the cable.

The burial points are usually in the areas of ships anchoring zones and those where fishing activities take place. Cable laying and cable burying are done one after the other using a plough device. In areas where simultaneous operation is impossible, a submersible robot is used for burying the cable.

More on both of these closer to each of the events…..

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Seabed Sampling

Picture courtesy of EGS 

Seabed Sampling provides the researchers with soil analysis and data which will assist with the rollout of the cable.  The analysis will identify, amongst other properties, the soil density which is useful in areas where the cable is to be buried.

Sampling by Divers

The divers will collect samples of seabed sediment, at intervals of 25m along the survey centreline, at the same locations as the steel bar probes.

Sampling by Inshore Vessel

A Stainless Steel Grab Sampler tool will be used the ‘grab’ samples of seabed sediment and will be collected at intervals of 500m from the safe inshore working limit to the 20m water depth contour. There is less than 5 kilometres between the 20m depth contour and the shallowest sample of the offshore vessel planned at 50m water depth

Sampling by Offshore Vessel

The shallowest sample of the offshore survey vessel will be at the 50m water depth contour, both a gravity core and a CPT. From there, there will be CPTs at intervals of 5km and gravity cores at intervals of 10km to the end of burial.

The vessel will use two (2) x 3m gravity corers, two (2) Grab Samplers and a Full Tool kit to perform the sampling

10 comments – Latest by:
  • Tim
    Tim, We use optical repeaters at regular intervals along the cable to amplify the signal.
  • Tim
    Considering the long distances, how do you overcome signal degradation and the need for repeating it?

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Diver Swim Surveys

Photo courtesy of

As part of the Sydney inshore survey, the dive team will swim five ”traverses” of the survey area to visually inspect the seabed in detail.  The dive team does this to ensure that the marine limit of the landfall topographic survey and the inshore limit of the inshore survey vessel overlap.

The centre traverse will be conducted along the middle of the survey corridor.  The divers will also traverse each side of the corridor at approximately 100 metres from the middle and also approximately 200 metres from the middle.  Each traverse will be marked with a diver’s rope annotated at intervals of 25m.

In addition, the divers will investigate, photograph and identify any obstructions along the route that is within safe diving limits.

2 comments – Latest by:
  • Matt Whitlock
    Stuart, Thank you for your comment. At the moment we are not planning to release the data in this fashion.
  • Stuart
    Are you guys able to publish a lat/long position listing of the proposed route for your cable. Would be cool ...

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Weather update for the Gelendzhik and the Megaforce

Over the weekend both the Gelendzhik and the Megaforce were on standby due to bad weather. Both vessels are anchored within 30kms of the Sydney region. The above satellite image from the Australian Bureau of Meterology was taken on Sunday.

The Gelendzhik was experiencing gale force Beaufort 9 conditions up to 45 knots with a heavy, south-westerly swell.  The winds have caused minor damage to the on board antennae, and communications have been limited to satellite phone.  The crew had a weekend forecast of 50-55 knot winds with  rough to high seas.  We are waiting for the reports from yesterday’s activities.

The Megaforce is also anchored, riding out the poor weather conditions, with 30-40 knot winds in a 2-3 metre swell.  Our survey representative, Martin Blakely, reports that conditions are clearing and they hope to resume survey activities tomorrow.

The schedule for the survey takes into account delays due to poor weather conditions, and as such the survey is still considered to be running on schedule.

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Survey Weather Update

Last week the survey was delayed due to a large storm front 600kms south of the survey ship.  In the picture, taken from the Australian Bureau of Meterology website, the storm front is visible as the green and blue mass on the east coast of the Australian State of Queensland.  The ship is currently just off Mackay (on the east coast of Queensland) and is due into Sydney in the next couple of weeks.

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Permits in Guam

In order to land the cable from the sea into Guam, we are required to apply for particular permits.  To date we have applied for and been granted the following permits:

  • Guam Coastal Zone Management Plan – this is an environmental permit to ensure we are compliant with the Coastal Zone Management Act.
  • Section 106 concurrence with the State Historic Preservation Office – this is an archaeological permit to ensure we are not presenting any risk to heritage items.
  • NOAA (National Oceanic and Atmospheric Association) concurrence – This is to ensure we are compliant with the US coastguard on navigation and sea use.
  • Guam EPA concurrence – this is a subset of the Coastal Management Plan application.

We have also applied to the US Army Corps of Engineers for a permit to allow us to install our cable through the existing duct from the sea to the Beach Man Hole.  This permit is currently out for public consultation.

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When a project of this nature is launched there are always environmental concerns over the installation of such a system.

PPC-1 has had to go through rigorous scrutiny to ensure that any potential environmental impacts are avoided or minimised. To this end, as a part of the ACMA permitting regime, PI embarked on a 6-month Environmental Impact Assessment.

The results of the assessment were submitted to the Federal Department of the Environment, Water, Heritage and the Artsfor approval under the Environmental Protection and Bidiversity Conservation Act.

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