Frequently Asked Questions

Geothermal Development and the Environment

Some of the most common environmental questions raised during the planning and early stages of a new geothermal power project are answered below.

As a green energy company, it’s important to GEL that our impact on the environment is kept to a minimum throughout the duration of a project. GEL will do this in a number of ways:

  1. Undertaking a full suite of ecological surveys before a planning application has been submitted. This involves initial Extended Phase 1 habitat surveys, to establish what species are likely to be present, followed by a comprehensive monitoring campaign to identify and record evidence of individual protected species, in line with best practice guidance.
  2. Use existing access routes into a site, retaining hedgerows and trees as much as possible. If anything has to be removed it will be reinstated after drilling.
  3. The biodiversity will be increased by at least 10% after the power plant has been installed and is operational. Ecological & Environmental consultants will guide GEL in finding the best possible way to enhance the natural biodiversity at each site.

During drilling and testing, an area of approximately 2Hectares is needed to accommodate equipment and welfare units for the crew, but once the power plant is operational, this will reduce to approximately 1Ha. GEL can therefore utilise the additional space to provide green screening around the site as well as re-wilding the remaining area with native species.

To manage traffic associated with the development, GEL is required to have a detailed traffic management plan, which may include temporary road closures and parking restrictions whilst larger vehicles are entering and exiting the site. However, these must be planned in advance to minimise disruption. A traffic management plan for each site will be drawn up in discussion with Highways England and the emergency services; it is something that Highways will govern, and GEL will be responsible for the distribution of this information to all hauliers and site visitors.

 

Traffic increase around site will be highest at the start and end of the drilling phase when the drilling equipment is moved into/out of the site. During this time, the number of loads will be managed to ensure it is not significantly above the average traffic for the access road, and movements will only occur between 7am-7pm. There will be no queueing outside of the site. At all other times, including when the power plant is operational, there will be just a few cars visiting the site.

GEL must keep any noise on site below a certain decibel level mandated in the conditions of planning permission. Noise levels will be monitored both on site and at nearby receptors (often in the gardens of the nearest local houses) and if the nearby receptors show levels reaching close to the maximum noise levels for the time of day/night, GEL are alerted, the noise logs are assessed, and site management are contacted to ensure that work on site does not breach these levels. Work on site will be stopped if required.

For more information on GEL’s noise management, please refer to the noise FAQs below.

Yes, GEL can drill under people’s property at depths greater than 300m without permission, as stated in the Infrastructure Act 2015. GEL will drill vertically for approximately 3km before deviating under adjacent land, therefore drilling will not cause any damage to properties surrounding the development sites.

Drilling itself creates no discernible ground movement as the drill bit is formed of three cones that turn and grind away at the rock so slowly that you can’t feel the movement.

When drilling reaches the fault zone, drilling mud will be lost in the fractures and can cause some micro- seismicity. After drilling has been completed a ‘testing phase’ is carried out. It is common for small micro-seismic events to be felt during this period.  At United Downs seismicity was felt at a maximum ground velocity of 0.8mm/s. This is ten times less than the Cornwall Council regulations for daytime blasting at quarries and could never cause any damage to nearby buildings or infrastructure.

For more information on induced seismicity and how GEL manages the risk, please see the separate Seismicity FAQ and the animation on YouTube.

While there is a drilling rig on site (estimated 6 – 9 months), it is required to be lit at all times for the safety of the rig crew and potential low-flying aircraft from RNAS Culdrose, Search & Rescue operations or local airports. A lighting management plan will be developed for each site in conjunction with key stakeholders and will follow UK government guidance on reducing light pollution.

No, GEL does not hold the mineral rights for new sites because geothermal heat is not owned by anyone and is therefore not governed in the same way as minerals and metals in the UK. Once a site has confirmed planning permission for geothermal power development, GEL will open discussions with the appropriate mineral rights holders to ensure any relevant activity has been agreed.

Shallow water boreholes will not be impacted by  deep geothermal developments. Geothermal wells are targeting reservoirs hosted in natural fracture zones at more than 4km below the Earth’s surface, unlike water boreholes which target shallow groundwater at 50 - 80m below the surface. For more information, see the separate Borehole FAQ.

GEL will always strive to bring benefits to the local communities in both the short and long term. These include:

  • A Community Fund of at least £40,000 per site shared between sustainable, cohesive community projects in the local parishes.
  • More than £1.5million was spent with local businesses during the last project.
  • A dedicated community manager will keep the public informed about the project progress and report back on concerns or issues to the GEL team to ensure an open dialogue is maintained.
  • An education and careers Programme for schools across Cornwall provides engaging resources and talks as well as careers advice from primary school to university.
  • GEL will increase every site’s biodiversity by more than 10%
  • Direct and indirect green jobs will be created in Cornwall.

Cornwall has a long history of heavy industry and is proud of its visible mining heritage. Throughout Cornwall, derelict engine houses can be seen inland and on cliff tops from a great distance. The engine houses vary in size, but they tower above the ground with a stack or chimney up to 30m high. A geothermal power plant will be a fraction of this height, can be painted to camouflage the main structures and screened with native trees and shrubs. GEL are keen to ensure power plants do not detract from the existing vista that is peppered with the relics of past industry.

You can always contact the project team if you have any questions or concerns using one of the methods below:

Telephone: 01326 331920

Email: contact@geothermalengineering.co.uk

Postal Address: Community Relations Manager, Geothermal Engineering Ltd, Unit 3, Gate B, United Downs Industrial Estate, Redruth, Cornwall, TR16 5HY

Developing Geothermal in Cornwall

Some of the most common operational questions raised during the planning and early stages of a new geothermal power project are answered below.

Geothermal energy provides a source of low carbon, baseload electricity and heat, meaning it is generating 24/7, almost all year round no matter what the weather is like or the time of day. It also requires a much smaller land area per unit of power than almost any other type of energy generation.

 

Geothermal power production and heating is not new. The UK is a long way behind many other countries around the world who are using geothermal energy to help combat the serious issue of climate change. UK heating and hot water currently make up around 40% of the country’s energy consumption, and almost a third of greenhouse gas emissions, so we must find new sources of clean, renewable baseload power and heat to help meet climate targets. Adding a brand-new source of green electricity to the UK national grid also helps increase the country’s energy security.

Cornwall has the hottest rocks in the UK, making it a sustainable solution with the added benefit of a small footprint and green job opportunities.

Historically, Cornwall has exploited the rich resources that are abundant above and below ground, and as a Cornish company, GEL are excited to be able to build this brand-new industry. It will bring much-needed investment to the Duchy, both in pure capital expenditure as well as benefitting a variety of businesses which will be part of these exciting projects.

Ideally new sites would be located on brownfield or industrial land. However, the reality in Cornwall is that there are very few brownfield sites, and almost none that are large enough for a drilling rig and within reach of a suitable fault structure for geothermal fluid flow.

A list of brownfield sites can be found on the Council Register of Brownfield Land or shown on the Cornwall Interactive Map. During geothermal site selection, GEL must weigh up a huge number of factors and where a  brownfield site isn’t available, GEL will do its best to limit proximity to conservation areas and densely populated locations.

There are a huge number of criteria considered when looking for a suitable geothermal development site. Three of the major considerations are:

  • Suitable geology
  • Access from a main road to allow transport of equipment
  • Proximity to local power infrastructure.

However, ideally, we also require a site to have a good-sized level working area, low ecological and environmental sensitivity, and potential for renewable heat users.

Development of a new site has five key stages:

  • Planning the site and achieving the relevant permissions
  • Preparing the site for drilling
  • Drilling two deep wells
  • Testing each well
  • Power plant construction and commissioning

No, Geothermal is not the same as Fracking. The concept proven at United Downs relies on circulating water through natural fractures in the rock to generate low-carbon, renewable energy. This is not the same as fracking, where a large volume of fluid with a complex chemical composition is injected at extremely high pressures to create new fractures in intact rock, to drain the oil or gas from the reservoir.

Geothermal power projects simply circulate fresh water in pre-existing fractures and, once the heat has been used at the surface, the fluid is reinjected into the same formation to re-heat.

The drilling rig chosen will depend on availability when contracts are being issued, which will be after planning consent has been given. GEL anticipate using a rig with a maximum mast height of 48m. For comparison, the Main Spire of Truro Cathedral is 76m high and the Carn Brea Transmitter is 152m high, both are permanent structures unlike the rig.

Every geothermal binary power plant will look slightly different as they are designed for the unique geological parameters available at each site. In general, the key features will include:

  • A single-story insulated building which houses the generator and turbine for power generation.
  • A small set of 10m-high air cooled fans; used to recondense the working fluid after the vapour has been used to generate electricity. These fans do not produce any visual plumes of steam or any odour.
  • Pipework connecting the wellheads to the plant.
  • A water storage lagoon which is used during well testing and routine maintenance.
  • Low-level, small-scale substation and transformer for connecting the power station to the grid.

There will be no cooling towers, no electricity pylons, no steam, and no emissions of any kind.

GEL will use binary power plants which emit no steam, gases or smells. It can be difficult to find images of these when searching online as most conventional geothermal plants are associated with volcanic environments, where the water is so hot that a ‘Flash’ power plant is used. GEL will keep the geothermal fluid in a closed loop and reinject it, but many flash plants do not reinject the fluid, instead releasing it as steam from a large cooling tower. This steam may also contain volcanic gases, some of which smell like rotten eggs.

For a good example of a binary geothermal power plant, click on the link below and navigate to the second image to the left, titled “CENTRALE DE GEOTHERMIE PROFONDE DE SOULTZ-SOUS-FORETS”. Click on the target symbol below the title and you will see an operational binary power plant at Soultz-sous-Forêts in France.

https://www.ubi-light.com/pro/es/VISITE-ES-2/

The initial planning applications do not include lithium extraction, but the fluid at every geothermal site will be laboratory tested to identify any chemical and metal compounds present in the fluid. A high concentration of lithium was found at United Downs, so it is likely that other sites across Cornwall will have similar concentrations.

Lithium extraction from geothermal fluid offers an exciting opportunity for Cornwall. Lithium is a vital component of batteries, large and small, which we use in our everyday lives from mobile phones to electric vehicles. Britain is currently reliant on Lithium imports from China and the USA, so the UK needs a secure source of Lithium which Cornwall could provide.

However, extracting lithium from geothermal brines is in its infancy and so far, it has only been proven using small-scale Direct Lithium Extraction (DLE) plants similar in size to a shipping container. DLE plants do not need to be located on the same site as a geothermal power plant.

You can always contact the project team if you have any questions or concerns using one of the methods below:

Telephone: 01326 331920

Email: contact@geothermalengineering.co.uk

Postal Address: Community Relations Manager, Geothermal Engineering Ltd, Unit 3, Gate B, United Downs Industrial Estate, Redruth, Cornwall, TR16 5HY

Domestic Water Boreholes & Deep Geothermal Wells

Dwellings which cannot easily be connected to mains water will often choose to have a domestic water borehole installed. This section has been designed to answer the common questions from people with a domestic water borehole located near to a geothermal power project.

There are many differences between deep geothermal wells and domestic water boreholes. Deep geothermal wells are cased in steel and cement from the surface for approximately ¾ of their depth and bring geothermal fluid contained in fractures at 4,000-5,000m depth to the surface. After the hot fluid has been used to produce renewable electricity, the water is reinjected underground to approximately 2,500m depth. In comparison, domestic water boreholes are rarely more than 200m deep and are cased with either steel or plastic with either an open hole section or perforated cased section in the part of the rock which contains the fresh water. The water from domestic boreholes is not deposited back underground, therefore the water extracted from a borehole is not replenished by the borehole user.

*Farming is an important industry in Cornwall, and this has a potential impact on the quality of private borehole water supplies.  Use of pesticides can affect water quality, as can the presence of livestock.

*Cornwall Council: Private Water Supplies Webpage

The geology of Cornwall also impacts on the quality of the groundwater. High levels of manganese, iron and arsenic have all been recorded in water samples taken from private borehole water supplies due to the natural presence of these within the rock.

Geothermal developments must follow regulations and guidance from the Environment Agency to ensure that groundwater is not impacted by drilling or operations. At first, a pilot hole is drilled approximately 30” wide and 11m deep and cased with a steel cylinder, to stabilise the top of the well. Air is used to extract the debris, so no fluid is injected or extracted. The next section of the well is then drilled to approximately 900m. In this section, clean water is used to lubricate the drill bit and remove debris during drilling, and then it is cased with steel and cement. No water is extracted from the ground at these depths; therefore, borehole water supply is never depleted. As drilling continues, the well is cased with more steel and cement to around 3,000m, effectively sealing off the entire well from ground water and preventing any possible interaction of well fluid with groundwater.

*The majority of Cornwall’s private borehole water supplies are used for human consumption. Private water supplies can be used for purely domestic purposes such as cooking and washing, or for large scale commercial operations such as farming or breweries. Ensuring clean, safe drinking water is the biggest concern and this is achieved in several ways including protecting the source and secondary treatment, such as filtration and disinfection. Private water supplies are regulated by national legislation:

*Cornwall Council: Private Water Supplies Webpage

Cornwall Council provides a useful leaflet explaining the basics of the Private Water Supplies Regulations 2016.

If you think the water from your domestic borehole is contaminated, do not consume the water until you have received professional advice, either from your borehole supplier or Cornwall Council.

You can always contact the project team if you have any questions or concerns using one of the methods below:

Telephone: 01326 331920

Email: contact@geothermalengineering.co.uk

Postal Address: Community Relations Manager, Geothermal Engineering Ltd, Unit 3, Gate B, United Downs Industrial Estate, Redruth, Cornwall, TR16 5HY

Noise Management

Geothermal Engineering Ltd (GEL) takes its responsibility to the local community very seriously and will use its best endeavours to prevent noise disturbance. An important step in the management of noise is to select a drilling rig that is designed for use in urban environments and noise-sensitive areas. 

No, GEL must keep within set noise limits. Noise from the site will be controlled in accordance with conditions relating to noise emissions set out in the planning permission for each site. If GEL persistently exceeds maximum noise limits, the site could be closed while investigations take place, so it is important for the smooth running of a geothermal project that noise limits are adhered to.

During drilling and well testing operations, 24 hour working is permitted. Day time noise emissions must not exceed 65dB LAeq, 1 hour, as measured 1 metre from the façade of any receptor and night- time noise emissions must not exceed 45dB LAeq, 1 hour, as measured 1 metre from the façade of any receptor. Noise limits vary depending on the day of the week and the time of day.

During the drilling phase continuous noise monitoring will be carried out using a network of sound level monitors (SLMs) at several locations; one on the main site and at least three at remote locations called receptors.

 

The main site SLM will measure noise close to the drilling rig for source identification purposes. The remote locations are chosen to collect representative data for the surrounding area, paying particular attention to the closest sensitive receptors and population centres.

 

The system is configured so that GEL personnel are sent automated notifications should the noise levels at the site or any of the receptor locations approach or exceed prescribed levels.

During mobilisation and demobilisation of the drilling rig there will be a number of large vehicles arriving and leaving the site over a period of 10 to 14 days, these will be mostly during daylight hours unless the police require some movements to take place at night. 

 

Vehicles that are used on the site will have their reversing beep disabled and instead use a white noise when reversing for the safety of personnel.

Best Practicable Means (BPM) measures to be implemented at the drilling site will be consistent with the recommendations of BS5228-1:2009+A1:2014 (the British Standard on noise) and will include the following:

  1. Potentially noisy non-essential activities will be prohibited at night
  2. Traffic movements will be restricted at night as far as possible
  3. Site-based vehicles will be fitted with white noise reversing alarms
  4. Equipment will be operated in a mode that minimises noise
  5. Use of loudspeakers and outdoor radios will be prohibited except for safety and urgent communication
  6. The site induction, which all visitors, contactors and members of staff must complete will include instruction on measures to minimise noise including voices and manual labour
  7. Short-term activities which may induce temporary elevated noise levels will be undertaken during daylight hours wherever possible
  8. Both fixed and movable acoustic barriers will be deployed.

 

If noise disturbance does occur, GEL will implement a procedure to deal quickly and transparently with any complaints. All complaints will be logged, treated with the same genuine concern and an outcome delivered as soon as is practicably possible.

 

Four options will be available for members of the public to make a complaint:

  1. By phoning the site
  2. By email
  3. By letter
  4. Via parish councils or Cornwall Council.

 

Information you will need to provide:

  1. Your name
  2. Your address including your postcode.
  3. The best phone number to contact you on (landline or mobile).
  4. Your e-mail address if you have one.
  5. You will need to explain precisely and concisely why you are contacting GEL, with locations, times and the nature and duration of the noise disturbance.

 

Complaints will be dealt with in five steps, as follows:

  1. Capture - details of complaint recorded.
  2. Investigate - complaint will be investigated as soon as practically possible.
  3. Resolve - If the investigation demonstrates that site activity caused the noise disturbance the Drilling Manager and Supervisor will discuss with the drilling contractor available prevention and mitigation measures.
  4. Respond - GEL will respond to all complaints as quickly as practically possible.
  5. Closure - A complaint will only be closed once the complainant has been given a response and has confirmed that they are satisfied.

Natural & Induced Seismicity

Earthquakes happen constantly all over the world when rocks underground move suddenly because of a build-up in surrounding pressure. This generally happens along a natural break in the rock, such as a fault or fracture zone produced by tectonic movement in the past. If the movement is large, a large amount of energy is released, and the ground shaking can cause a lot of damage. However, these sorts of events only tend to happen along tectonic plate boundaries, where the Earth’s crust is moving at incredibly fast rates. At the other end of the scale, tiny movements along small, natural faults and fractures such as those in Cornwall release much less energy and generally go unnoticed.

Earthquakes can be detected and located using networks of seismometers. In the UK these are installed and managed by the British Geological Survey (BGS). The energy from an earthquake reaches seismometers at different times, depending on how far away they are from the event and the speed that the signal (vibration) travels through the rocks. If the same earthquake is detected at several seismometers, it is possible to calculate the location, magnitude and depth of the earthquake. There is limited coverage by the national network in Cornwall but Geothermal Engineering Ltd (GEL) has installed a more sensitive network to improve our detection limits and accuracy. The location of the seismometers within this network will be moved to suit new development sites.

Yes, seismic event is just another name for an earthquake. They are sometimes also called tremors.

A microseismic event is a very small seismic event. This usually means an event with a magnitude of less than 1.

There are various scales used to measure the size of earthquakes. Many people are familiar with the Richter Scale, which describes the amount of energy released at the source deep underground. Earth scientists now refer to this as the local magnitude (ML). When people talk about a magnitude 2 event, this is what they mean.

The magnitude scale is logarithmic, which means that each increase of 1 in the scale means a 10-fold increase in the amount of energy released. So, a magnitude 2 event is ten times bigger than a magnitude 1, and a magnitude 3 is ten times bigger than a magnitude 2, and so on.

Destructive earthquakes generally have magnitudes of 6 or above. The 2011 earthquake in Japan had a magnitude of about 9; ten million times stronger than a magnitude 2 event.

Induced events are exactly the same as natural ones, except that the trigger for the movement is human activity, rather than a gradual build-up of geological pressure over time. The seismic shock waves are still generated by movements of rock, but the cause may be blasting in a local quarry, a low-flying helicopter or the testing of a geothermal well. In the case of geothermal projects, ground movement can be caused by water pressure helping to unstick the rock along the faults or small fractures.

No, there is no need to worry. Although the testing and development of geothermal reservoirs in Cornwall is likely to cause some seismicity, most induced events will be incredibly small and release very little energy. Cornwall’s geology means that even minor movements may be felt across a small area close to the development. However, induced seismicity is regulated and carefully managed so it is not dangerous and will not cause any damage.

During the Hot Dry Rock project in Cornwall in the 1980s, about 10,000 microseismic events were recorded but only two were felt at the surface and neither caused any damage to infrastructure or any harm to the local community.

A detailed seismic hazard assessment was carried out by Ove Arup & Partners in 2017 for the United Downs project. The assessment concluded that the seismicity induced during the Hot Dry Rock research programme in the 1980s is probably the best indicator of the seismicity to expect at United Downs; those events never reached a magnitude greater than 2 (see “what does seismic magnitude mean?” section). This was proven at United Downs, where injection testing caused a maximum event magnitude of 1.7 ML. However, production testing caused no seismicity, so no events are expected once the powerplant is operational.

No it isn’t. The concept proven at United Downs relies on circulating water through natural fractures in the rock. This is not the same process as fracking, where a large volume of fluid with a complex chemical composition is injected at extremely high flow rates and pressures to create multiple new fractures in intact rock, to drain the oil or gas from the reservoir. Fracking brings concerns with waste disposal and contamination, whereas geothermal development simply circulates fresh water in pre-existing fractures and, once the heat is used at the surface, reinjects it into the same formation, as regulated by the Environment Agency.

GEL has installed a network of seismometers around the United Downs site, which will be relocated and expanded for future sites, as necessary. This network is continuously providing real-time data and can detect and accurately locate both large and small seismic events. If a seismic event is detected, GEL and seismic specialists will quickly be able to work out where it happened. Depending on how far it was from the site, and the type of work being carried out at the time, it will be possible to determine whether it was the result of GEL’s activities or not.

In fact, the seismic monitoring equipment can detect events that are hundreds of times too small to be felt at surface and this monitoring will be done on a continuous basis. GEL has a contract with a local seismic specialist who will provide accurate measurements of any seismic activity and will also pass the data to BGS for them to interpret. A seismic management procedure is in place so that GEL can work with the relevant authorities. The team will also post relevant information on their social media.

The project is regulated by Cornwall Council. Our seismicity management protocol uses existing British Standards and planning guidelines for blasting, quarrying and mining activity. Importantly, it is based on how much ground vibration is measured at the surface, referred to as Peak Ground Velocity, or PGV. This is believed to be a more accurate depiction of what will be felt by people in the local area compared to the magnitude (ML) of an event (see “What does seismic magnitude mean?” section).

The ‘unconventional’ oil & gas extraction industry (often referred to as the fracking industry) is regulated by the Oil and Gas Authority (OGA), who have set low limits on induced seismicity and require the developers to operate a ‘traffic light’ system to manage their activities.

They must halt activity if an event of magnitude 0.5 is detected, irrespective of its effect at the surface. Geothermal developers are not regulated by the OGA and are not required to adhere to their limits or their methodology. This does not mean that geothermal projects are unregulated; just that they are regulated in a different way.

The most important difference as far as GEL projects are concerned is that our seismicity management protocol is based on ground vibration at the surface, not on event magnitude at the source. We believe that this is a more appropriate methodology since it relates directly to the impact on people and property and it is consistent with planning regulations already in force in Cornwall for other industries that could cause ground vibrations, such as mining, quarrying and construction.

GEL operates at very conservative vibration limits. Cornwall Council set a maximum PGV of 8.5mm/s for a single event in their daytime blasting regulations, and previous research suggests that humans cannot generally feel movements with a PGV of less than 2mm/s. However, at United Downs a maximum PGV of 0.8 mm/s was felt by some individuals. Therefore, operations at all GEL sites will enter a 'caution' state if events with a PGV greater than 0.5mm/s are detected during the day. Above this, operations will be closely monitored and if further significant events are detected, operations will cease until the reservoir stabilises.

We have the normal public liability insurance but there is no specific cover for induced seismicity. It would be necessary to prove that the damage was caused by induced seismicity from the project.

You can always contact the project team if you have any questions or concerns using one of the methods below:

Telephone: 01326 331920

Email: contact@geothermalengineering.co.uk

Postal Address: Community Relations Manager, Geothermal Engineering Ltd, Unit 3, Gate B, United Downs Industrial Estate, Redruth, Cornwall, TR16 5HY

Check out our informative seismicity video