GroundSourceHeatPump hydrogeology LowCarbonHeating SustainableInfrastructure

Lewisham hospital tests groundwater heat pump beneath protected park

*Test drilling works begin in Ladywell Fields to assess the viability of an open-loop ground source heat pump system for University Hospital Lewisham. Source: Salamander news (image by Mark Morris)*

A major ground-source heat pump project at University Hospital Lewisham has entered its initial test phase, with test borehole works beginning in Ladywell Fields, a designated Site of Importance for Nature Conservation. The project aims to replace the hospital’s 1970s gas-fired boiler system with a low-carbon heating network using groundwater from the chalk aquifer beneath the park.

The scheme forms part of the Public Sector Decarbonisation Scheme and is supported by £17,790,274 of government grant funding. The total investment is expected to reach around £25 million. Once operational, the system is projected to save approximately 4,000 tonnes of carbon emissions per year and improve local air quality by reducing reliance on gas heating.

The first phase involves drilling two deep boreholes to around 90 m depth, together with two shallow observation boreholes of around 10 m depth. These will be used for pumping tests, groundwater monitoring and sampling. The purpose is to confirm whether sufficient groundwater can be abstracted from the chalk aquifer, passed through heat exchangers and safely returned underground.

The planned open-loop system would extract groundwater from boreholes near Ladywell Fields, transfer heat to the hospital system, and then return the water to the aquifer. If testing confirms that the project is technically viable, a second phase could involve drilling up to six additional boreholes, subject to further approvals and engagement.

Open-loop ground-source systems require careful assessment of aquifer productivity, water chemistry, reinjection capacity and groundwater levels. The test phase is intended to establish whether the proposed system can operate reliably and safely before any full scheme proceeds.

The project also raises environmental and planning considerations because Ladywell Fields is a valued public park and a recognised nature conservation site, with ecological improvements linked to the Ravensbourne river corridor and local biodiversity.

The hospital trust has stated that groundwater, arboricultural and ecological surveys have been carried out, and that drilling locations were selected to minimise impact on tree root zones. Track matting, fenced work areas and controlled access routes are being used to reduce disturbance during the test phase. The park is expected to remain open while the works proceed.

As the project develops, transparent monitoring and clear public communication will be important. Issues requiring careful management include groundwater abstraction and reinjection, construction traffic, future buried infrastructure and the protection of the park, river environment and long-term ecological value.

This project illustrates the complexity of decarbonising public infrastructure in dense urban settings. Replacing fossil-fuel heating systems can significantly reduce emissions for large energy users such as hospitals. However, low-carbon infrastructure still requires robust hydrogeological assessment, environmental safeguards and community confidence. The success of the Lewisham scheme will depend on demonstrating that carbon reduction and protection of a sensitive urban landscape can be achieved together.

Sources: salamandernews.org, salixfinance.co.uk, lewishamandgreenwich.nhs.uk