TMCnet - World's Largest Communications and Technology Community



Submarine Cable Decommissioning: Assessing the Environmental Risks
[March 03, 2006]

Submarine Cable Decommissioning: Assessing the Environmental Risks

TMCnet Special Guest

In-use submarine cables around Waters.

Early in 2004, Southampton-based Emu Ltd.—a marine environmental survey and consultancy company—was commissioned by a consortium of cable companies (including British Telecom and Cable & Wireless), to undertake a generic environmental risk assessment to be used during the decommissioning of redundant submarine telecommunications cables.

Eighteen months on, the generic risk assessment has been successfully applied in a number of different scenarios, and has also now been posted on the United Kingdom Cable Protection Committee (UKCPC) and International Cable Protection Committee (ICPC) websites as an example of “industry best practice.”  Copies of the report can be obtained by non-members from the respective secretary’s of the organizations.

This article affords an appropriate opportunity to briefly review this management tool and its application to the management of cable decommissioning.                                              

The Drivers

At the outset, it is helpful to identify the drivers which triggered the need for a generic risk assessment.

Exponential demand for global network expansion
The industry has been engaged in both the replacement of first generation fibre optic cables and the expansion of its networks which have to keep pace with a near doubling in global demand for non-voice communication every 12 months.

The pace of technological advance
Capacity in submarine cables has increased exponentially, and is now generally 10Gbit/second per wavelength, with a single fibre carrying up to 100 wavelengths.  This is an increase in capacity of approximately x2000 since the early systems were installed in the 1980s.

Increasing competition for spatial use of the seabed
Trawlers have had historic claims to the seabed, but recent expansion in the oil and gas industry, marine dredging and more significantly in the development of offshore renewable energy installations means deployment and decommissioning of submarine cables now takes place in an increasingly congested environment. 

Awareness about the marine environment
The public have a greater awareness about the marine environment today than earlier generations.  As a responsible sector, the submarine cable industry wishes to demonstrate that their activities are causing no harm to marine life.

Following a landmark court ruling in favor of Greenpeace in 1999, the Habitats Regulations 1994 which implemented the requirements of the Habitats Directive (92/43/EEC) and the Wild Birds Directive (79/409/EEC) have been demonstrated to apply out to 200 nautical miles, the limits of territorial waters. As a result, the first offshore candidate Special Area of Conservation (SAC) has been accepted by Defra and there are a range of seabed habitats and species which are under consideration for designation with potentially far reaching implications for the submarine cable industry and other marine based operators.

The Requirement

The industry was looking for a management screening tool which could be used generically to highlight potential environmental impacts when initiating applications for consent to decommission and potentially remove redundant submarine cables.  When submarine cable routes are initially planned, significant data is collected that includes a detailed interpretation of the seabed type, a depth of burial assessment, and other specific data relating to each section of cable.  Emu Ltd. was tasked with developing a risk matrix which could be used in conjunction with this routing data that would trigger further investigations, to either confirm or discount potential impacts.  Key features of the Risk Assessment are the requirements to:

  • Correspond to standard route survey seabed descriptions

  • Consider the worst case scenario because of the generic nature of the tool (precautionary principle)

  • Be easy to use.

The Approach

 A fundamental principle is that a tool of this nature can only identify potential sensitivity to a given impact. Emu Ltd. followed a similar approach to the model developed by Dave Carlin and Stuart Rogers of The Centre for Environment, Fisheries and Aquaculture Science (CEFAS) to assess dredging impacts upon fisheries, where the theoretical generic matrix of impacts has to be compared against site specific data to determine actual vulnerability.

 “To describe the actual vulnerability of the fisheries issues to potential impacts on a site specific basis…requires balancing the theoretical sensitivity of a resource to an impact, and the local features of the site and the distribution of the biological resource, to derive an actual site-specific vulnerability.” (Carlin & Rogers (2002))

The scope of significant issues associated with submarine cable decommissioning has been narrowed to those which potentially have a long-term or permanent effect.  The reasons for this are:

  • The scale of disturbance resulting from cable removal, in general terms, is very small.

  • The impacts associated with the installation of submarine cables are well documented.

  • Environmental factors will have been taken into consideration during the initial rigorous consenting process to which all cable routes are subject prior to installation.

  • The physical disturbance to the seabed associated with the removal of cables is significantly less than that caused by installation.

Furthermore, the benign chemical composition of submarine telecommunications cables, removes any risk of direct chemical contamination in the decommissioning process.

Table: Generic Risk Assessment for Potential Impacts Associated with Submarine Cable Recovery.

Notes for table:
1.  Prior consultation with appropriate regulatory authorities (EN / Countryside Council for Wales (CCW) for inshore/JNCC for offshore or equivalent bodies) should be undertaken when planning recovery.
2.  Prior consultation with English Heritage (EH) /Welsh Historic Buildings (CADW)/ Historic Scotland / Environment & Heritage Service NI (EHS) should be undertaken in relation to archaeological / historic issues when planning recovery.
3.  Prior consultation with DEFRA (England and Wales) / Scottish Environment Protection Agency SEPA / Department of the Environment and Department for Agriculture & Rural Development in Northern  Ireland in relation to potential impacts on the commercial fishing industry.
4.  Prior consultation with the EA / SEPA / Department of the Environment and Department for Agriculture & Rural Development in Northern should be undertaken in relation to shellfish production areas.
5.  Prior consultation with Maritime & Coastguard Agency (MCA),  Hydrographer of the Navy and local harbour authorities  should be undertaken in relation to navigational issues.

The Risk Matrix

The generic risk matrix is shown above. It evaluates the potential sensitivity for ten seabed categories to particular categories of risk related to cable removal, providing a tool for highlighting the significant issues for a given cable route. Accompanying text provides a more detailed explanation for each box of the matrix.  E.g. the text for box C6, Stiff Clay / impacts to commercial fishing reds as follows:

C 6      Commercial Fishing

Recovery of cables from the seabed will have a beneficial impact on the commercial fishing industry by eliminating a potential snagging hazard for fishing gear.  Both scallop dredgers and beam trawlers while not targeting working clay seabed may well pass over these areas and given the shallow burial depth (0.4m) there is a potentially significant risk of snagging for cables left in situ.  If the minimum burial depth is increased, e.g. to deeper than 0.8m, then there is a much reduced likelihood of snagging and the positive benefits of recovery are marginal.

The impact on the commercial fishing industry of recovery of cables from stiff clay is assessed as localized, permanent and positive.

 The matrix is colour coded for ease of reference; green boxes indicate a high potential for positive impact resulting from cable removal (for example by reducing the risk of snagging by fishing vessels in an area frequently trawled), and the Amber & Red boxes indicate their may be some negative impact of cable removal that will require further investigation. Qualifying sub-notes highlight appropriate consultation which should take place at the planning stage. The cable owners  uses this generic risk assessment at an early stage in the decommissioning process, so that any issues are known about early in a project, and can be addressed in a professional and timely manner.

 Case Studies

The following case studies demonstrate how the environmental risk matrix has been applied to aid decision making on a couple of cable decommissioning projects.

TAT9 – Poldu Cove

TAT9 was an international cable connecting the with the . During the initial investigation using the generic matrix, a number of issues were highlighted, including the fact that the beach was protected under SSSI (managed by English Nature) and was a popular tourist spot, and that the area was commercially fished from Falmouth.

These issues helped lead the cable owners to the conclusions that the cable was generally considered a marine hazard, as it was also predominantly surface laid on bedrock, the risks of conducting cable recovery operations were low, and it could potentially benefit the local fishing community if it were recovered. It was also clear that the timing of any recovery operation must suit both the local community and conservation organizations, so a subsequent recovery operation was conducted after the summer season, in consultation with the local conservation and fishing communities, which was successfully completed on time and on budget.

Ross Coral found growing on TAT9 during recovery

4 – Filey

Denmak4 was an international cable which connected the with . When this cable was installed, it was buried close into the shore where suitable sediments existed, but further offshore burial was impossible so many sections of the cable were ultimately surface laid. During the initial investigation using the generic matrix, a number of issues were highlighted, but most notably the requirement to liaise with the local fishing community, as they fished close into the shore.

During the investigation phase, it became clear that the removal of the inshore section of cable would cause not only considerable disruption to the local fishing community, but also could cause some negative impact on the local environment. Subsequently it was agreed with both the local community and the consenting bodies that the first 8km of cable where burial was good, would be left in situ, and that the remaining section of surface laid cable would be recovered.

In this instance, the real strength of the generic risk assessment was highlighted, where the decommissioning process really took into account the local conditions on the ground, ensuring the cable was recovered where the impact of the recovery was negligible, but leaving the cable in-situ where it was well buried in a stable seabed, and the environmental impacts of the recovery would be negative.

Beneficial Disposal of Obsolete Cables

When redundant cables have been recovered, every effort is made to recycle the constituent components, but this generally involves shipment abroad, and inevitably some portion of the cable ends up in Landfill. The submarine cable industry has been looking at innovative ways of recycling this cable, and one idea that is currently being investigated is as a construction material for Artificial reefs.

Projects in the have successfully shown that where cable has been deposited on the seabed to create artificial reefs,  the structures have provided a protected nursery and habitat for various species of fish, crabs and lobsters and promoted a pelagic fish attraction desirable for recreation fishing.  In view of the apparent success of this project, a grant application has been made by British Telecom to the Marine Stewardship Fund, administered by the Crown Estate to investigate the feasibility for using redundant submarine cables as a construction material for artificial reefs in waters.

Submarine cables provide a protected nursery for many species in an artificial reef in the USA .

Enhancement of the Industry’s GIS database

Environmental impact assessment in the marine environment necessarily encompasses a plethora of diverse topics including infrastructure / navigational considerations, commercial seabed developments, fishing activities, conservation designations, ecological sensitivity / biotope maps, geophysical maps, sites of cultural / historic interest, defence activities etc. 

The associated broad spectrum of data needed to support environmental impact assessment is held by disparate sources.  While all this data can be supplied in response to a site specific request, there may be merit in maintaining certain data sets in a permanent geographical information system (GIS) format, compatible with the current system used by the industry.  In particular, if not currently held, electronic maps on trawling activity and seabed characteristics may be particularly helpful in attributing causes for system failure.

About Emu Ltd.         

Emu Ltd provides worldwide survey and consultancy services relating to engineering development, prospecting and environmental issues in rivers, estuaries and seas.  The company has been operating for 15 years in a variety of sectors including aggregate dredging, telecommunications, offshore wind & renewables, oil and gas, the water industry and government. In 2000 Emu Ltd undertook the Environmental Impact Assessment for the telecommunications cable routeing from Isle of Man to .  The company currently operates to ISO 9000:2000. Our laboratories operate to UKAS standards.

Further Information

A copy of the report entitled Subsea Decommissioning:  A Limited Environmental Appraisal can be downloaded by UKCPC members from the UKCPC web site at: Non members can request a copy by contacting the secretary at:


Carlin, D and Rogers, S (2002) A Procedure to Assess the Effects of Dredging on Commercial Fisheries.  Prepared by CEFAS Lowestoft in support of CSG Contract A0253.

Emu Environmental Ltd. (2000) Isle of Man to Northern Ireland Cable Route Survey:  Environmental Assessment for the Isle of Man.

Heath, J (2001)  Benign use of the Seabed by Telecommunications Cables. (Memorandum to the Secretary of the ICPC.).

Pritchard, P (2000) Environmental Risk Management.  Earthscan.


Ray Drabble is Senior Environmental Consultant for Emu Ltd. He can be reached at

[ Back To's Homepage ]

Technology Marketing Corporation

35 Nutmeg Drive Suite 340, Trumbull, Connecticut 06611 USA
Ph: 800-243-6002, 203-852-6800
Fx: 203-866-3326

General comments:
Comments about this site:


© 2019 Technology Marketing Corporation. All rights reserved | Privacy Policy