United Downs Deep Geothermal Project

Challenge

The United Downs Deep Geothermal Power Project is the first deep geothermal energy project in the UK, located near Redruth in Cornwall. It aims to generate renewable electricity (and heat) by extracting hot water from deep underground and using it to drive turbines.

SLR was initially commissioned by Geothermal Engineering Ltd (GEL) in 2009 to help secure planning and permitting for the first deep geothermal power plant in the UK.

Cornwall was selected by GEL for its large geothermal resource. GEL has a specialist staff base with in-depth knowledge of geothermal projects, based on experience gained during the original Hot Dry Rock project carried out in Cornwall in the early 1980s. The United Downs project is the first of its kind in the UK, using an enhanced geothermal system for power production. Whilst GEL had specialist technical skills, SLR supported the various environmental studies, planning consents and environmental permitting required for the project to receive the appropriate approvals.

Solution

SLR was selected for this project due to our proven ability to navigate complex planning and environmental consenting for energy schemes. With the United Downs project breaking new ground as the UK’s first deep enhanced geothermal system, GEL required a partner with multidisciplinary strength, robust technical capability, and the ability to engage confidently with regulators and stakeholders across all project phases.

Our team led the full suite of environmental and planning services needed to secure the project’s approvals. This included comprehensive environmental impact reporting, covering hydrology, ecology, landscape and visual impacts, archaeology, transport, noise, and air quality, as well as a detailed seismic hazard assessment, which was essential for addressing public and regulator concerns around potential micro‑seismic activity associated with deep geothermal injection. We worked closely with the Environment Agency and the local planning authority to ensure all technical evidence met or exceeded regulatory expectations, smoothing the path for the UK’s first deep geothermal drilling permissions.

Beyond initial planning and permitting, SLR continued to support GEL through subsequent development phases. We assisted in discharging planning conditions, securing abstraction and discharge licences, and providing environmental inputs as the design evolved. As the project expanded, we also delivered planning support for GEL’s lithium processing pilot plant, enabling the project to integrate emerging opportunities associated with Cornwall’s geothermal brines. Our responsiveness, technical depth and long‑term partnership approach helped the client overcome challenges at each stage, ultimately enabling the geothermal plant to progress from concept to construction and into operation successfully.

Impact

SLR’s work enabled the project to secure planning consent in 2010, with drilling commencing in 2018 and completing in 2019. Our environmental assessments, permitting support and condition‑discharge work helped the client progress from exploration to construction with confidence. The production and injection wells - drilled to 5,275 m and 2,393 m respectively - confirmed higher‑than‑expected geothermal temperatures, allowing the development of the UK’s first deep geothermal power station.

The plant was successfully switched on in February 2026 and will now generate renewable electricity for 10,000 homes, demonstrating the viability of deep geothermal energy in the UK.

Wardell Armstrong (now part of SLR) and SLR have been instrumental in helping GEL achieve multiple UK firsts over the last 18 years. Their blend of local professionals and global expertise has been invaluable in successfully driving forwards numerous complex planning applications and environmental permits.