Environmental impacts over the seabed and benthic communities of submarine cable installation in the Biscay Marine Energy Platform (bimep)

Abstract

The Biscay Marine Energy Platform (bimep) is an offshore infrastructure for the demonstration and testing of wave energy harnessing devices promoted by the Basque Entity of Energy (Ente Vasco de la Energía - EVE). Bimep is located close to Arminza town (Basque Country, Northern Spain) and it consists on an 5.3 km2 sea area between 50 and 90 m depths where four static submarine cables will be placed, operating at 13kV and 5MW. On the first of June 2009, the General Council on Environmental Quality Assessment of the Ministry of Rural, Marine and Natural Environment of the Spanish Government, on the light of the Environmental Impact Study (EIS) of the bimep project undertaken by AZTI in 2008, decided not to submit the project to the whole Environmental Impact Assessment (EIA) process. Nevertheless, the Environmental Impact Statement (EISt) of the Ministry, taking into account the great uncertainties about some predicted environmental impacts, underlined the need to implement the proposed Environmental Monitoring Program (EMP) of the EIS. Among other environmental factors, substratum alteration was foreseen to occur during the commissioning stage of the submarine cables and consequently may affect related benthic habitats and species. Hence, on August 29 of 2013, the EVE entrusted to AZTI to carry out the EMP of the installation of the submarine cables in bimep, which consist on: (i) a seabed characterisation with a multi-beam echo sounder; (ii) a characterization of benthic communities and seabed disturbance by means of a visual inspection with a submarine camera attached to a Remote Operated Vehicle (ROV) all along the submarine cable route and the mooring areas. The results obtained were compared with those obtained during the preoperational phase of the EMP (carried on 2012), showing that the observed impacts were in the range of those predicted in the EIS of bimep.

Full text

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2449 m
898m
1538 m
1787m
1153m
ARMINZA
1700 m
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•On the first of june 2009, the General Council on Environmental Quality Assessment of the Ministry of
Rural, Marine and Natural Environment of the Spanish Government, on the light of the Environmental
Impact Study (EIS) of the BIMEP project (www.bimep.com) undertaken by AZTI, decided to not submit the
project to the whole Environmental Impact Assessment (EIA) process.
•Anyway, the Environmental Impact Statement (EISt) of the Ministry, taking into account the great
uncertainties about some predicted environmental impacts, underlined the need to implement the
proposed Environmental Monitoring Program (EMP) of the EIS. Among other environmental factors,
substratum alteration was foreseen to occur during the commissioning stage of the submarine cables and
consequently may affect related benthic habitats and species.
•Consequently, on August 29th of 2013, the Basque Entity of Energy (promotor of the BIMEP project)
entrusted to AZTI to carry out the environmental monitoring plan of the installation of the submarine
cables in bimep. The main objective was to monitor and check the environmental impacts over the seabed
and benthic communities.
•According to the EIS and EMP of the preoperational phase of bimep, seabed and benthic communities are
dominated by circalittoral coarse sediments and rock and other hard substrata (see image on the right)
with a singular structure named Seabass Island which is a sea mountain with high biodiversity values.
Environmental impacts over the seabed and benthic
communities of submarine cable installation in the
Biscay Marine Energy Platform (bimep)
1. INTRODUCTION
2. THE BIMEP PROJECT 3. METHODOLOGY
Acknowledgements
This work has been funded by bimep S.A.
Bilbao, 20-24 April 2015
Juan Bald1*, Carlos Hernández1, Ibon Galparsoro1, J. Germán Rodríguez1, Iñigo Muxika1, Igor Cruz2, Mikel Markiegui2, Julián
Martínez2, José María Ruiz2 Yago Torre Enciso3, Dorleta Marina3
1AZTI-Tecnalia. Marine Research Division. Pasaia (Gipuzkoa), Spain. *Corresponding author: jbald@azti.es
2Sociedad Cultural de Investigacón Submarina (INSUB). Av. de Navarra, 0. 20013 Donostia (Gipuzkoa), Spain
3Ente Vasco de la Energía (EVE). Alameda de Urquijo, 36 - 1º. Edificio Plaza Bizkaia. 48011 Bilbao (Bizkaia), Spain.
•Promoted by the Basque Entity of Energy (EVE), BIMEP represents an offshore test site for the
demonstration of wave energy converters (WEC). It consists of 5,3 km2 sea area between 50 and 90 m
depths where four static submarine cables will be placed, operating at 13kV and 5MW. Wave energy
generation devices will be connected to these cables through dynamic submarine cables.
4. RESULTS
5. CONCLUSION
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1
3
4
5
6
2449 m
898m
1538 m
1787m
1153m
1700 m
Spain
Basque
Country
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1
3
4
5
6
2449 m
898m
1538 m
1787m
1153m
ARMINZA
1700 m
Spain Basque
Country
a) Seabed characterisation: Using a high resolution
RESON SeaBat 7125 multibeam echosounder. As
result of that methodology, a 0,5m resolution
seafloor digital elevation model was produced
b) Visual inspection: With a underwater video
camera attached to a Seaeye Falcon Remote
Operated Vehicle (ROV) in 38 points distributed
all along the submarine cable route and the
mooring areas (yellow popints in the figure on
the left) and in 5 points by scuba-divers (red
points in the figure on the left)
A4. Circalittoral rock and other hard substrata (A4.121; A4.212; A4.22)
A3. Infralittoral rock and other hard substrata (Seabass Island)
2°52'W2°53'W2°54'W
43°29'N43°28'N43°27'N43°26'N
Depth (m)
High : -0,33
Low : -116,38
¯
1
A5.142: Circalittoral coarse sediment
•Consequently, two mitigating measures were suggested: (i) to plan de cable route over soft sediments; (ii) to maintain a security distance of 100 m of the cable route from the “Seabass Island”
Seabass Island
The installation of the
submarine cables began
on the 11th of September
2013 with the PLRG of the
cable route
And ended between the 20th and
27th of September 2013 with the
laying of the four submarine cables.
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2449 m
898m
1538 m
1787m
1153m
ARMINZA
1700 m
70 m
One of the most significant alterations can be
observed in the outcrop of the submarine cable
coming from the beach man hole through a
tunnelling and channelling technique known as
Horizontal Directional Drilling (HDD). As we can
see in the figure on the left, a trench of about
60 m long and 2-3 m at each side of the cable
was undertaken for each cable route.
Another alteration which can be observed is the
effect on the seafloor of the cable burial
attempts in some stretches of the cable route.
Hence it was observed a removal of sediments
and benthic communities in an area of 2-3 m at
each side of the cable.
20 m
70 m
Regarding the submarine mountain known as
“Seabass Island”, the distance between the cable
and the mountain is about 70 m, 30 m below the
minimum distance established in the EIS.
Nevertheless, no impacts where observed over the
benthic communities in this geological structure
which maintain the biological richness and value
observed in the EIS and in the preoperational EMP,
demonstrating the effectiveness of the protection
measures proposed in the EIS of bimep.
Funded by BIMEP S.A. and carried out by the Marine Research Division of AZTI-Tecnalia, the EMP of the submarine cables installation in bimep showed that the observed impacts are in the range and even below of
those predicted in the EIS of bimep (assessed as non-significant) and the effectiveness of the protection measures proposed in the EIS of bimep for the preservation of the biological values of the singular submarine
mountain known as “Seabass Island”
No significant alterations where observed in most part of the cable
route over the seafloor and benthic communities. The cable simply
remains lay down in the seafloor and even buried by the sediment
dynamics itself. In some stretches of the cable route, this has been lay-
down over rocky substratum but there have not seen impacts over the
benthic communities in this substrate.
The obtained results show three main impact
points in the cable route