Environmental Statement - Maersk Oil

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5.1.3. PHYSICAL PRESENCE 5‐ 6 Balloch Field Development Environmental Statement Section 5 Assessment of Potential Impacts and Controls This section discusses the potential environmental impacts associated with the physical presence of the drilling rig and associated vessels, as well as the drilling rig’s anchors and chains. Rig and associated vessels The presence of a drilling rig and the increase in associated vessel movements has potential implications for other sea users, notably those involved in commercial fishing and shipping. Once in position, the drilling rig will have a temporary 500 m exclusion zone around it meaning that there will be no fishing or unauthorised vessels within that area. While the drilling rig is on station the GPIII’s guard vessel will serve the standby requirements of the drilling rig, thus minimising vessel use. Total fishing effort within the area of the development is approximately 1 % of total UK effort (Scottish Government, 2012). Shipping activity in the area is also considered to be moderate (DECC, 2012). With mitigation measures in place, there are not expected to be any interactions between the rig and its associated support vessels and other vessels. Drilling rig anchors and chains The drilling rig will be held in place by an anchor mooring spread consisting of a maximum of 12 anchors. The precise arrangement of the anchors around the rig will be defined by a mooring analysis which will be undertaken prior to bringing the rig into the field. This will take account of the water depth, tidal and other currents, prevailing wind conditions and any seabed features at the well location. Each anchor weighs approximately 12 te and will produce a linear scar of approximately 50 m length during setting, before sinking into the seabed. The depth of penetration will be dependent on the shear strength and load bearing capacity of the seabed soils. Effects and their duration on the benthic community structure from disturbance caused by the anchors are related to individual species biology. As the majority of benthic species recorded on the European continental shelf have short life spans and relatively high reproduction rates, the effect of the anchors on the local benthic community is likely to be low. Proposed control measures for impacts associated with physical presence during the drilling phase Control measures in place to mitigate impacts from the physical presence of the drilling rig and associated vessels are presented below. In consideration of the control measures detailed above, the physical presence of the drilling rig and associated support vessels has been assessed as having a low/negligible impact. 5.1.4. NOISE: DRILLING The impacts from noise generated by the support vessels and drilling rig are discussed in Section 5.4. 5.2. INSTALLATION PHASE Proposed Control Measures An exclusion zone will be established around the drilling rig, enforced by a standby vessel. Mooring analysis will determine rig anchor position. This section discusses the impacts associated with the installation of the subsea infrastructure. Emissions produced during subsea installation are primarily associated with vessel use. Subsea installation activities will cause disturbance to the seabed and could potentially interfere with other users of the sea. Underwater noise associated with the installation vessels and piling of the cooling spools is assessed in Section 5.4. This section considers the emissions to air produced by the vessels, physical presence of the subsea infrastructure, discharges associated with hydrotesting and the noise associated with piling of the manifold.
Balloch Field Development Environmental Statement Section 5 Assessment of Potential Impacts and Controls 5.2.1. EMISSIONS TO AIR Details of the vessels required to complete the installation of the necessary infrastructure are given in Section 2.5.10, while the associated emissions are given in Table 5‐5. A worst case scenario whereby the development will include three production wells is assumed. To put these emissions into context, they are combined with those from the support vessels required during the drilling phase and are presented as a percentage of total UK domestic shipping emissions in 2009. Table 5‐5 Summary of emissions associated with subsea infrastructure installation vessels. Vessel type Fuel use (te) 1 Emissions (te) CO 2 NO x N 2O SO 2 CO CH 4 VOC Vessels associated with installation of subsea infrastructure (DSV) Emissions from drilling support vessels (Table 5‐3). Total emissions from drilling support vessels and installation DSV 2009 UK domestic shipping emissions 2 2,148 4,852 85 0.31 5.73 22.48 0.26 2.86 6,600 21,120 392 1.45 26.40 103.62 1.19 13.20 25,972 477 1.76 32.13 126.1 1.45 16.06 4,900,000 % of UK total 0.53 % 1 Fuel use assumes three production wells. 2 Source: Department for Transport, 2011. Note: Atmospheric emissions have been calculated using emission factors from the EEMS Atmospheric Calculations Issue 1.810a (EEMS, 2008). From Table 5‐5 it can be seen that, in the worst case scenario, emissions associated with the drilling support vessels and the installation DSV amount to 0.53 % of CO2 generated by UK domestic shipping emissions in 2009. Given that the development is approximately 225 km from the nearest coastline and that the prevailing winds will result in very high dispersion and dilution of emissions produced, it can be concluded that the vessel emissions produced will resulting in no significant local air quality impact. In addition, the overall additive effect on climate change can be considered negligible given the very small portion these emissions form in relation to overall UKCS emissions. Proposed control measures for impacts associated with emissions to air during the installation phase Control measures to mitigate impacts from atmospheric emissions associated with installation phase are presented below. Proposed Control Measures Vessel use will be optimised, e.g. the GPIII standby vessel and supply vessel will serve these requirements for the installation DSV. Impacts associated with atmospheric emissions during the installation phase are anticipated to be low. 5 ‐ 7
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Environmental Statement - Maersk Oil

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