Unconventional oil and gas policy: SEA

15 Mitigation

15.1 The 2005 Act requires that ‘the measures envisaged to prevent, reduce and as fully as possible offset any significant adverse effects on the environment of implementing the plan or programme’ are outlined within the Environmental Report. These measures are often referred to as mitigation measures.

15.2 The assessment has identified a range of potential environmental effects, and has concluded that the preferred policy position would not result in any potential significant negative effects in Scotland for all SEA topic areas. Therefore, no mitigation measures are identified in relation to this alternative.

15.3 However, the assessment has concluded that the other reasonable alternatives would result in potential significant negative effects in Scotland for certain SEA topic areas. Therefore, mitigation measures are identified in relation to the ‘business as usual’ and ‘pilot project’ alternatives.

15.4 The mitigation measures proposed are intended to be applied at the scale of individual unconventional oil and gas projects, rather than in relation to a policy. Furthermore, existing regulatory controls have been taken into account when considering potential, additional mitigation measures.

Air

15.5 Fugitive emissions – currently, there are technologies for limiting and monitoring fugitive methane emissions following shale gas extraction and CBM. Case studies from the US have demonstrated that these measures can be costly, lowering economic profitability. As a result, uptakes of measures for limiting emissions have been relatively low in the US due to the high costs of emission prevention and mitigation. Therefore, developments in the US unconventional oil and gas industry are currently focussed on reducing the cost of sensors and other related technologies^[311]. However, it is recognised that the regulatory situation relating to emission limitations is different in Scotland.

15.6 Vented emissions – gases that are being vented could be burnt rather than dispersed into the atmosphere. Combustion would partially reduce the environmental impacts, because the process serves to incinerate many of the volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) that would otherwise be released directly into the atmosphere. However, it is recognised that the combustion process would still result in adverse environmental impacts^[312].

15.7 Super emitters – a large proportion of the fugitive gas which is emitted has been found to come from a small group of ‘super emitters’. Although a complete avoidance of super-emitters may be unachievable, with suitable operational control and maintenance procedures these high emitters could largely be eliminated. The International Climate Fund (ICF) suggests that annual inspections and repair would reduce emissions by 40%, quarterly inspections by 60% and monthly inspections by 80%. If the super emitters could be brought in line with the average, then total supply chain emissions would be reduced by 65%-87%^[313].

15.8 Leakage from decommissioned wells – ensuring well integrity is highly dependent upon the application of best practice standards for well design and construction. The risk of gas leakage (including methane) from abandoned unconventional oil and gas wells is expected to be very low if constructed and abandoned to comply with international standards and industry best practice^. To further reduce potential impacts, monitoring technology can be used so that remedial measures can be taken at an early stage. Examples include fibre optic sensing techniques including Fibre Bragg gratings (FBGs), Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS). Recent evidence suggests that fibre optic sensing technology has existed for decades, but most techniques are not yet mature for commercial deployment in the unconventional oil and gas industry. DAS has matured most rapidly, as is currently deployed on a commercial basis for selected geophysical and flow applications following a recent trial^[314].

15.9 Emissions from traffic associated with unconventional oil and gas developments – there are a number of ways to reduce the air quality impacts of increased vehicle movements associated with unconventional oil and gas developments. Firstly, transport capacity can be optimally deployed using supply chain management systems and ICT resources. These measures have the potential to reduce the impacts on local air quality associated with vehicle movements. Secondly, emissions can be reduced or avoided through the use of pipelines or the re-use of wastewater^[315].

Water

15.10 Contamination caused by produced water and flowback water – there are a number of feasible ways to process flowback and produced (FP) water:

• Through the treatment of the wastewater so that it can be returned (back) to the environment. For instance, a crystallisation plant was recently commissioned in Pennsylvania (US) that is able to convert wastewater into water that meets current standards for water discharge in the US. The salt that is extracted during the process can also be used as road salt. The crystallisation plant in Pennsylvania is the first of its kind, and is more efficient economically and environmentally compared to more conventional wastewater treatment plants. Efforts are currently undertaken to further refine existing techniques or invent new approaches to fully or partially reuse wastewater.
• Injection of the wastewater into an empty gas field
• Reuse of wastewater in subsequent fracking activities.

15.11 In addition, there are various substitutes that can be used to (partially) replace water in hydraulic fracturing fluids – carbon dioxide, LPG and/or propane being the most commonly used substances in the US and Canada. However, it is recognised that alternative substances have their respective disadvantages. For instance, they are often harmful or hazardous by nature (e.g. LPG) and their effect and risk is insufficiently known as nearly all alternative substances are hardly used or at the experimental stage.^[316]

15.12 Gas and fluid leakage associated with poor well construction – ensuring well integrity is highly dependent upon the application of best practice standards for well design and construction. In addition, a significant reduction in risks can be achieved by using monitoring technology so that remedial measures can be taken at an early stage. Examples include fibre optic sensing techniques including Fibre Bragg gratings (FBGs), Distributed Temperature Sensing (DTS) and Distributed Acoustic Sensing (DAS). Recent evidence suggests that fibre optic sensing technology has existed for decades, but most techniques are not yet mature for commercial deployment in the unconventional oil and gas industry. DAS has matured most rapidly, as is currently deployed on a commercial basis for selected geophysical and flow applications following a recent trial^[317].

15.13 Aquifer cross contamination – further development of high resolution sensors for monitoring could be used to prevent or reduce methane migration to aquifers.

15.14 Accidental releases of hazardous materials – increased traffic safety measures could help to reduce the number of vehicles carrying hazardous substances getting involved in traffic accidents.

15.15 Surface spills – geotextiles and geo-synthetics can be used on surfaces to reduce the risk of surface water pollution. It is important to note that geotextiles and geo-synthetics are already available, but are not yet widely used.

15.16 Borehole leaks – there are other ways to mitigate or limit the effects caused by the contamination of fracking fluids; the advancement of alternative hydraulic fracturing and drilling techniques may increase the efficiency of the hydraulic fracturing process so that the use of hazardous chemicals can be reduced or avoided.

Soil

15.17 Ground contamination – many of the water mitigation measures could help to protect soils, and reduce or avoid ground contamination. These include the use of geotextiles and geo-synthetics, the use of biodegradable fracking fluids, the (optimised) treatment of flowback and produced water through mobile units or at central facilities, and the use of advanced monitoring technologies (e.g. DTS and DAS). Other mitigation measures include careful soil stripping, storage, and restoration in accordance with best practice. Furthermore, contingency planning to deal with accidental spillages and contamination of soil is likely to significantly reduce the potential impacts on soil quality and quantity associated with unconventional oil and gas developments.

15.18 Greenhouse gas emissions associated with land use change – avoiding development on high carbon soils is likely to have positive effects in terms of reducing greenhouse gas emissions associated with land use change.

15.19 Soil sealing resulting from construction of the well pad and access road – mitigating the effects of soil sealing can be achieved by using permeable materials that reduce water runoff and allow more rain water to infiltrate through the underlying soils. This could help to lower water treatment costs and reduces the risk of flooding and water erosion. Furthermore, impacts on soil quality could be reduced or potentially avoided if the works would be undertaken in suitable weather conditions to prevent soil damage i.e. avoiding periods of high rainfall.

Climatic factors

15.20 Direct greenhouse gas emissions – many of the air mitigation measures are relevant to mitigating greenhouse gas emissions, particularly direct greenhouse gas emissions including: controlled and uncontrolled releases of produced gas; and, the combustion of fossil fuels for on-site power and transportation. These include annual inspections and repair, the use of advanced monitoring technologies (e.g. DTS and DAS), the use of supply chain management and ICT resources, the use of pipelines to replace transport, and the re-use of wastewater.

15.21 Greenhouse gas emissions associated with land use change – avoiding development on high carbon soils is likely to have positive effects in terms of reducing greenhouse gas emissions associated with land use change.

15.22 Furthermore, greenhouse gas emissions could also be reduced through carbon offsetting. Carbon offsets are typically achieved through financial support for projects that aim to reduce the emission of greenhouse gases, which, in turn, compensate for emissions made elsewhere. Examples of such projects include forestry projects (e.g. wood planting), energy efficiency projects, and renewable energy projects such as wind farms, biomass energy, or hydroelectric dams. As such, carbon offsets could be achieved through investments in Scotland’s renewable energy sector or woodland planting in Scotland.

Biodiversity, flora and fauna

15.23 Loss of habitat, habitat fragmentation and impacts on hydro-ecological functioning – potential impacts could be reduced if site selection and the laying of pipes associated with that development would avoid sites of high biodiversity value, particularly areas characterised by sensitive hydro-ecological regimes. Surveys, such as bats and birds surveys, could help to identify potential ecological constraints and provide initial recommendations for avoidance of impacts and mitigation measures, as well as further ecological investigations where necessary.

15.24 Disturbance of species – disturbance to species is highly dependent on the timing of works. To minimise potential impacts on breeding birds, for instance, the construction works that effect nesting habitat should be carried out during winter to avoid the bird breeding season (March-August). Furthermore, disturbance to local fauna could be reduced if lighting would avoid illuminating habitats such as woodland and hedgerows. Other mitigation measures include covering up any excavated holes/trenches overnight to prevent mammals from becoming trapped.

15.25 Accidental release of hazardous material to air, soil, or water – many of the water, soil and air mitigation measures could help to protect or reduce potential impacts on local biodiversity. These include careful soil stripping and restoration, use of permeable materials during soil sealing, the use of geotextiles and geo-synthetics, the use of biodegradable fracking fluids, the (optimised) treatment of flowback and produced water through mobile units or at central facilities, the use of advanced monitoring technologies (e.g. DTS and DAS), annual inspections and repair, the use of supply chain management and ICT resources, and the re-use of wastewater.

15.26 Introduction of non-native species – contingency planning to deal with accidental releases and spread of invasive species is likely to reduce the potential impacts on biodiversity, flora and fauna.

Cultural and archaeological heritage

15.27 Loss and/or damage of known and unknown archaeology, and other designated and undesignated heritage assets – potential impacts could be reduced or avoided if the siting of development would avoids sites of cultural heritage significance. Site survey to identify previously unknown cultural heritage assets and monitoring during site construction and decommissioning phases will also help minimise impacts.

15.28 Direct and indirect impacts on the setting of cultural and archaeological heritage –screening (e.g. planting hedges) and landscape treatment could minimise potential impacts on the setting of cultural heritage sites.

Landscapes and geodiversity

15.29 Site selection to avoid sensitive, locally important sites and visually prominent locations.

15.30 Mitigation measures such as screening, landscape treatment and landscape restoration after decommissioning could further reduce landscape and visual impacts that may arise from unconventional oil and gas developments.

15.31 Sharing of infrastructure could reduce the number of traffic movements over the lifetime of an unconventional oil and gas site, with associated positive effects by reducing impacts on landscape quality and local amenity.

Material assets

15.32 Land use change – potential impacts in relation to land use change could be reduced if brownfield sites are promoted for re-development, rather than greenfield land. This would ensure the prudent use of resources.

15.33 Impacts on infrastructure – many of the water, soil and air mitigation measures could help to reduce impacts on infrastructure and the wider environment. These include careful soil stripping and restoration, the use of advanced monitoring technologies (e.g. DTS and DAS), annual inspections and repair, the use of supply chain management and ICT resources, and the re-use of wastewater.

Population and human health

15.34 Noise and light pollution– noise surveys could be carried out to establish whether noise exposure associated with unconventional oil and gas developments is likely to be hazardous. Noise impacts associated with traffic movements could be reduced if areas with a high density of sensitive receptors would be avoided, if possible. Furthermore, potential noise impacts could also be reduced through undertaking regular maintenance of equipment, the use of silencers or other noise attenuation equipment, the use of enclosures on noise generating equipment associated with drilling, minimising night-time vehicle movements, and minimising the use of audible vehicle reversing alarms at night. In addition, positioning and rotating the rig could help to mitigate drilling noise, as well as light nuisance.

15.35 Odour nuisance– nuisance caused by odour issues could be reduced through a number of mitigation measures. Examples include the disclosure and risk assessment of fracturing fluid chemicals and environmental monitoring (baseline and ongoing).

15.36 Health issues associated with induced seismic activity – contingency planning to deal with the impacts of induced seismic activity on human health could be used to reduce potential impacts.

15.37 Impacts on local amenity and mental well-being – screening of site activities through planting could help to reduce impacts on local amenity associated with unconventional oil and gas developments.

15.38 Physical health and safety risks – contingency planning to deal with the impacts of unexpected events and hazards could be used to reduce potential impacts.

15.39 Road accidents – the occurrence of road accidents associated with unconventional oil and gas development could be reduced if areas with a high density of sensitive receptors would be avoided, if possible. Additional safety measures are likely to further reduce the occurrence of road accidents. Examples of such measures include improving site access and junction design, signing, lining and providing anti-skid treatment^[318].

15.40 Health impacts associated with air and water pollution – many of the water, soil and air mitigation measures could help to protect public health. These include careful soil stripping and restoration, the use of geotextiles and geo-synthetics, the use of biodegradable fracking fluids, the (optimised) treatment of flowback and produced water through mobile units or at central facilities, the use of advanced monitoring technologies (e.g. DTS and DAS), annual inspections and repair, the use of supply chain management and ICT resources, and the re-use of wastewater.