Local environmental impacts
Unconventional gas operations pose a number of possible risks to the environment and human health. The level of risk will depend on local factors. These include things like the geology of the area, location of water bodies, how close the project is to local communities, and the scale of the project.
A range of regulators will consider these risks when deciding whether to grant the different permits that operators need.
- Water pollution
- Fracking involves injecting large quantities of water, sand and other substances into underground shale rock formations at high pressure. This ‘frack fluid’ then flows back to the surface, mixed with naturally occurring water from the shale-gas rock formation. This is known as ‘produced water’. It can contain brine (salt), toxic metals, and naturally occurring radioactive materials (‘NORM’). The waste water that flows back to the surface will need to be treated before it can be discharged to the surface water environment, to avoid harmful water pollution.
- There is a risk that the ‘frack fluid’ that is injected could seep into groundwater, polluting it with chemicals. This could happen if there is a problem with the well casing, or (less likely) if the fluid seeps through the geology that separates the fracked formation from the aquifers. Fracking targets are usually separated from drinking water aquifers by some thickness of low permeability rocks. Further, concentrations of chemicals in the frack fluid are generally very low.
- Another risk is that groundwater could be polluted by substances such as arsenic, lead and radioactive substances that can occur naturally in rock and that could be mobilised when the rock is drilled and fracked.
- Many of the same risks arise with de-watering for coal bed methane, because of the drilling fluids used and potential leaks from wells into underground strata.
- Local air pollution
- Leaks of methane and other gases can result particularly at the completion stage, when the ‘frack fluid’ and 'produced water' is pumped back to the surface. Other significant sources of local air pollution include exhaust and dust from traffic coming and going from the site, and fumes from generators on the site.
- Noise, vibration and tremors
- Most stages of a project to extract unconventional gas will cause noise and vibration. This includes construction noise when preparing sites for drilling; noise and vibration when drilling the wells; noise from ‘flaring’ (burning waste gases); and noise from pumps when fracking or de-watering.
- There is a risk that fracking could cause tremors, or earthquakes. For example, in 2011 fracking operations at Presse Hall near Blackpool caused tremors measuring 2.3 and 1.5 on the Richter scale.
- Shale gas and CBM operations can generate considerable traffic. This includes trucks and machinery involved in preparing sites for drilling, and trucks delivering the sand and chemicals that are injected at the fracking stage. This can result in dust, vehicle emissions and noise disturbance to communities living nearby.