Horns Rev Offshore Wind Farm Environmental Impact Assessment of Sea Bottom and Marine Biology Prepared for: I/S ELSAM, Overgade 45, Fredericia, 7000 Denmark Carried out by: Bio/consult as, Johs. Ewalds Vej 42-44, Abyhej, 8230 Denmark Text: Editing: Translation: Simon B. Leonhard Gitte Spanggaard Word Design ApS 01.03.2000 Bio/consult A/S Page 3 Contents SUMMARY..................................................................................................................................................................... 4 SAMMENFATNING (IN DANISH).......................................................................................................................... 6 1. INTRODUCTION...................................................................................................................................................... 8 2. THE RESEARCH AREA......................................................................................................................................... 9 3. METHODS................................................................................................................................................................ 10 4. EXISTING SITUATION.........................................................................................................................................12 4.1. Sea bottom ................................................................................................................................................................12 4.2. V egetation .............................................................................................................................................................. 14 4.3. FAUNA..........................................................................................................................................................................14 5. IMPACTS.................................................................................................................................................................. 25 5.1. Production phase ...................................................................................................................................................25 5.2. CONSTRUCTION PHASE.............................................................................................................................................. 28 5.3. Proposed monitoring programme .....................................................................................................................29 5.3.1.Monitoring programme for the construction phase........................................................................................29 5.3.2.Monitoring programme during the production phase.................................................................................... 30 6. CONCLUSION..........................................................................................................................................................31 7. REFERENCES..........................................................................................................................................................33 ANNEXES...................................................................................................................................................................... 36 Homs Rev. Offshore Wind Farm Doc. No. 1680-1-02-03-003 rev. 1 Udarbejdet af: Kontrol: Godkendt: SBL RUF SBL Bio/consult A/S Page 4 Summary An Environmental Impact Assessment (EIA) of a planned 150 MW offshore wind farm at Homs Rev has been carried out for the marine biology and sea bottom in the area, and includes vegetation and benthic fauna. The study forms part of a total EIA of the planned offshore wind farm. This EIA study has been drawn up in accordance with the guidelines laid down by the Ministry of Environment and Energy in the publication, “Guidelines for preparation of EIA- studies for offshore wind farms.” Homs Rev is situated off Blavands Huk, which is Denmark’s most westerly point. It is a shallow reef with water depths between 2 and 9 metres and is primarily composed of sand, gravel and pebbles. The area designated for the wind farm lies directly south of Horns Rev and is dominated by sand with a median particle size of 0.3 mm. Along the edges, towards areas of greater depth, the particle size increases. There are areas of fine sand in the deepest area, and in isolated pockets within the proposed wind farm site. The sediment is characterised by a very low (<1%) organic matter content. Along the planned cable line, the sediment towards the shore and in deeper areas down to 25 metres consists of finer particles of silty sand and sandy clay-silt. The wind farm and cable line areas are completely devoid of vegetation. No larger stones, which could serve as a suitable substrate for attached vegetation, have been found in either the wind farm area or the cable area. The prevailing currents and the great degree of physical heterogeneity in the area result in the fauna being very heterogeneously distributed. No significant differences in species composition, numbers of individuals or total biomass have been registered in the faunal composition of the wind farm site and the reference area that extends 530 metres east and west of the area. The fauna in the wind farm area has similarities to fauna recorded on other sandbanks in the North Sea and is best characterised as an Ophelia borealis community, so-named after one of the characteristic and important marine bristle worms in the area. Such sand banks are characterised by a lower number of species and individuals, and a lower biomass than adjoining areas where the bottom is less unstable and has a higher content of fine sand and organic matter. The adjoining areas can be characterised as a true Venus and partial Abra community. The fauna here has a completely different composition than the fauna within the wind farm area and is characterised by the Venus-community bivalve Chaemelea gallina. In the deepest areas along the cable line, the fauna can be expected to be characteristic of the Abra community, which is related to finer sediment. There are also areas with finer sediments nearer the coast, where the fauna is characterised by a Lanice conchilega community, which is very common over large areas of the North Sea coast. ELSAM Homs Rev. Offshore Wind Farm Doc. No. 1680-1-02-03-003 rev. 1 Bio/consult A/S Page 5 Bivalves, which are an important food source for marine birds, such as the common scoter, are far less common in the area around Horn ’s Rev than immediately south of here and in other areas of the North Sea. Similarly the thick trough shell, Spisula solida, was not recorded during this study, although it was from 1993 to 1995 the target of commercial fishing trials in this area. The area of reclaimed sea bottom covered by establishing the wind farm, will be less than 0.1% of the total area of the site. It amounts to reclamation of an area with a potential biomass of benthic animals of approximately 600 kg. During the production phase only local and minor impacts on current, wave conditions and sediment transport are expected in the immediate area of the individual foundations, and changes in the overall benthic fauna are therefore not envisaged. An increased copper contamination of filter-feeding benthic animals can be expected as a result of the total annual discharge of 206 kg copper from the slip-rings in the wind turbines. The wind turbine foundations and scour-protecting revetments can be considered as a kind of artificial reef, which will increase heterogeneity in the area and create a substrate for colonisation by fouling organisms. Artificial substrates at Horns Rev will potentially be colonised by many species that to-day are on the Red List of threatened or vulnerable species in the Wadden Sea area. Observations have meanwhile demonstrated that colonies of fouling organisms on Homs Rev may be vulnerable to extreme weather conditions. Colonies of fouling organisms will probably produce a biomass that is many times greater than the present benthic community in the wind farm area on Horns Rev. Erection of the wind turbines and burying of the cable connections during the construction phase will only marginally affect the existing benthic fauna, directly through physical disturbance or indirectly through spill products from the construction work. This applies both to the wind farm area and along the cable line, which runs to the coast through a protected area for birds. The existing sampling design and baseline data for the benthic fauna are sufficient to be able to reveal any 50% changes in the biomass with a statistical certainty of 0.50 if future monitoring is undertaken. On the basis of the expected impact from the establishment of the wind farm, it is not deemed necessary to carry out special programmes during the construction phase for monitoring of the environmental-biological conditions. A monitoring and control programme is recommended during the production phase in order to follow the copper concentration in bivalves, or alternatively to initiate recovery or elimination of the copper-laden waste. A control programme is recommended during the production phase in order to follow the establishment and succession of the fouling community on the wind turbine foundations and scour-protecting revetments. ELSAM Homs Rev. Offshore Wind Farm Doc. No. 1680-1-02-03-003 rev. 1 Bio/consult A/S Page 6 Sammenfatning (in Danish) Som led i en samlet VVM-redeg 0relse