ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

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Bardolino Development Environmental Statement 6.3.2 Impact on sensitive receptors and proposed or designated sites The biological communities in the area are generally typical of sandy sediments in the central North Sea; infauna are typically dominated by polychaete worms, whereas epibenthic species include the shrimp Crangon allmanni and the hermit crab Anapagurus laevis (Section 4.4.2). The dominant species found during the Nelson survey undertaken in 2005 and 2006 were the polychaetes Paramphiome jeffreysii, Myriochele sp. A., Exogone hebes and the brittle star Ophiura affinis (Hartley Anderson, 2007). Benthic samples retrieved during seabed surveys undertaken within Quadrants 22 showed that benthic communities were homogenous throughout the area and typical of fauna found in undisturbed sediments of the central North Sea (UK Benthos 2000). Macrofauna of the area are largely homogenous and typical of sandy sediments in the central North Sea. Infauna was dominated by the tube-dwelling polychaete Myriochele oculata which is a common member of central North Sea sandy associations (IOE, 1990a, b; ERT, 1994a, b). Other species commonly found during the environmental surveys were the crustacean Eudorellopsis deformis, the echinoderm Amphiura filiformis, the cnidarian Cerianthus llyodii, the bivalves Chaetoderma nitidulum and Mysella bidentata and the polychaete worm Phoronis muelleri (IOE, 1990a). No sensitive, rare or threatened benthic communities are known to exist in the vicinity of Bardolino. Discharging the cuttings from the top-hole sections of the well directly onto the seabed would smother the sediments and associated fauna in a very small area of seabed immediately around the discharge point, and release pollutants into the sediments and the water column. In the short term, this would cause the mortality of some benthic organisms, create an area of habitat that is different to the surroundings and result in the temporary covering of the sediments and loss of habitat required for the benthic fauna. In the medium term, however, the local habitat is likely to return to the natural conditions. Habitat recovery would be promoted by: • the dispersion, dilution and breakdown of chemicals within the cuttings, which would occur in the current regime that exists in this part of the North Sea; • the spreading and natural dispersion of the cuttings which would result from sediment movement in the area and the current regime; and • bioturbation effects caused by the action of burrowing benthic organisms such as polychaetes and crustaceans (e.g. Tsutsumi et al., 1990; Chareonpanich et al., 1993; Chareonpanich et al., 1994; Hansen et al., 1999). Observations of the accumulation of cuttings during the drilling of tophole sections have shown that re-colonisation of the surface of cuttings by benthic animals can begin within minutes or hours. WBM cuttings discharged onto the seabed would be quickly recolonised by benthic fauna typical of the area. In a series of field experiments, Bakke et al. (1985) prepared trays of natural seabed sediment that were devoid of flora and fauna, and covered them with a 10mm layer of WBM slurry. These were returned to the sea and sampled periodically. Recolonisation of the material in the trays by diatoms, meiofauna and macrofauna started immediately. During real time observations of the accumulation of WBM around a well west of Shetland, infauna were observed to burrow up through the deposited cuttings within a few minutes after drilling ceased (Bakke et al., 1985). Most cuttings would settle within the immediate vicinity of the discharge point, but there is a possibility that very fine cuttings particles that remain in suspension in the water column may travel further. Any remaining WBM will be washed away from the cuttings and rapidly diluted to such low concentrations that no significant impact would be anticipated. Particles that travel in the water column are unlikely to be distinguishable from natural suspended solids. Maximum tidal currents in the development area may range between 0.26 and 0.39 m/s (UKDMAP, 1998) and play a significant role in defining the seabed bottom features by mobilising and restoring the surface sediments and incorporating the cuttings particles from drilling. In comparison to discharges of LTOBM, discharges of WBM generally result in wide dispersion of discharged cuttings and little accumulation of contaminants in sediments and biota (Daan and Mulder, 1996). At the Bardolino site, the effects on sediment and water biology of the discharge of WBM drill cuttings from the proposed well are therefore expected to be insignificant. Page 6-6 April 2008
Bardolino Development Environmental Statement Harbour porpoise is the only Annex II species which has been sighted in the close vicinity to the Bardolino development (Quadrant 22) (Section 4.4.4; UKDMAP, 1998). These are highly mobile and wide-ranging species, and the discharge of WBM mud and cuttings from the proposed development is unlikely to have any effect on them. If fish were displaced from the local area, they will rapidly return once drilling operations have ceased, although there could be very localised disturbance to seabed-spawning species. Nephrops, mackerel, lemon sole and Norway pout are known to spawn in the proposed development area. Mackerel, lemon sole and Norway pout all release their eggs into the water column to be fertilised, whereas Nephrops lay their eggs on the seabed and therefore may be at risk from discharges of WBM mud and cuttings. The proposed drilling activities are scheduled to occur between March and May 2009 (Section 3.3.2), and would coincide with the spawning periods for all four species. As described in Section 6.3.1, however, the area of seabed that is likely to be physically impacted by the discharge of WBM from the top-hole sections will be very small in relation to the known extent of spawning areas in this part of the North Sea. Nephrops live in burrows and lay eggs on the seabed, and are therefore potentially susceptible to the effects of the discharge of WBM cuttings; spawning occurs throughout the year and, therefore the drilling operations cannot be timed to avoid spawning periods. Previous studies around single well sites in the North Sea have indicated that the area of seabed that would be covered with cuttings from the tophole section would be a circle of approximate radius of 5 m (BMT Cordah data). Although the Bardolino development lies within a large area in which Nephrops have been noted to spawn, the Bardolino site and pipeline route comprise sandy clay (Section 4.2.6), rather than the muddy sediments that Nephrops prefer. Consequently it is not thought likely that the Bardolino location is a significant Nephrops area. The area of seabed that could be affected by cuttings from the tophole sections at Bardolino is therefore likely to be very small in comparison to the area inhabited by or available to Nephrops. Mackerel, lemon sole and Norway pout are less susceptible to discharges of WBM and cuttings as they release their eggs into the water column, and have a widespread distribution over the North Sea (Section 4.4.3). The spawning populations of Nephrops, mackerel, lemon sole and Norway pout are not considered to be at risk from the top-hole discharges from the Bardolino well. 6.3.3 Contribution to transboundary, cumulative or global impacts It is not predicted that the initial discharge of WBM cuttings (Section 6.3.1) would result in the deposition of material in the Norwegian sector of the Continental Shelf, some 40 km away from Bardolino. The discharge of WBM and cuttings from the top-hole section of the well would cause a transient and localised smothering of the natural seabed sediments and associated benthic communities. Consequently, this would represent for a short time a very small additional cumulative impact on the quality of the benthic environment in this part of the central North Sea. This environment is impacted by a range of other activities, including other oil and gas operations and fishing (Section 4.5). The WBM and cuttings themselves would in time be dispersed and covered by natural sedimentation, allowing benthic communities similar to those that existed before drilling to be re-established at the sites. Within the 500 m safety exclusion zone around the well site these communities are likely to be afforded some protection from the effects of bottom-towed fishing gear. It is therefore suggested that over the lifetime of the project, the net cumulative effect of the drilling operations and presence of the well and pipeline on benthic ecology would be likely to be at least neutral. 6.3.4 Consultee concerns No concerns were raised through the informal consultation process (Section 1.6). April 2008 Page 6-7
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13 th March 2008 Dear Sir or Madam,
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To: Paul Wood Shell U.K Limited, Se
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What risks to marine mammals do pil
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Noise propagation modelling. Noise
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If, for any reason, piling operatio
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APPPENDIX 1 MARINE MAMMAL RECORDING
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ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

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