Water neutrality

Sinking a borehole to provide a private fresh water supply to a development can be a way to overcome water neutrality requirements through the planning system. This is because a borehole can, in certain circumstances, provide fresh drinking water to a development without the need for that development to rely on mains water supplies, and without impacting on the sensitive Arun Valley designated sites.

What is a borehole?

Boreholes are sunk deep into the ground into water-bearing layers of rock (aquifers), which are naturally replenished from rainfall that falls on the surface above the aquifer. Aquifers can cover very extensive areas or can be very limited in their horizontal and vertical extent. Water companies, including Southern Water, also use boreholes to provide a substantial proportion of public water supplies, although these boreholes are on a much larger scale than private supply boreholes.

Several developments in Southern Water’s Sussex North Water Resource Zone (WRZ) have already sunk their own private water supply boreholes, are exploring options to do so, or are considering this option for their development. Any boreholes that are sunk for this purpose must be carried out by qualified, competent companies to ensure that all of the relevant legislation is followed, ensuring that any drinking water supplied by the borehole is safe for human consumption; does not introduce risks to the Arun Valley site, other protected sites, or the aquifer itself; and will provide any development with enough water for long enough to ensure that there is no reliance on mains water supply (i.e. certainty of supply).

Natural England’s water neutrality position statement sets out that new development cannot add to the abstraction pressures at Southern Water’s Pulborough abstraction boreholes. Therefore, as long as any proposed private borehole for a development can demonstrate that it is not going to add to the abstraction at Pulborough, or otherwise affect the Arun Valley designated sites and provides sufficient certainty of supply, it may be a suitable solution for some sites to demonstrate that new development is water neutral.

The Geology

The geology in Sussex North is complicated. It is possible that private boreholes sunk close to the Arun Valley sites may be acceptable because they are taking water from a different aquifer than those under the Arun Valley sites. Conversely, there can be situations where private boreholes sunk relatively far away from the Arun Valley sites may not be acceptable because there is a link between the aquifers, which could therefore impact on the protected sites. Environment Agency advice presumes against abstraction within the Hardham Basin (Folkstone Beds) and Chichester and Worthing Chalk, and where a borehole into the Lower Greensand Arun and Western Streams could reduce flows in the River Rother. This is why the Sussex North local planning authorities may accept boreholes in some locations close to Pulborough but reject others further away – distance to Pulborough is not necessarily a good indicator of acceptability.

Private supply boreholes can create other issues, including poor water quality and impacting on the availability of water in certain aquifers. For these reasons, the local planning authorities in the Sussex North WRZ will only accept boreholes as a means of supplying drinking water to a development if strict criteria are met.

The Environment Agency require that larger private boreholes – those seeking to provide more than 20 cubic metres (20,000 litres) of water per day – must obtain an Abstraction Licence from them, which will set specific requirements on the volume of water that can be abstracted, the aquifer the water is to be taken from and any other requirements such as monitoring and metering how much is abstracted.

Before an application for an Abstraction Licence is made, any developer must apply to the Environment Agency for a Groundwater Investigation Consent. It can take up to a year to go through the Groundwater Investigation Consent and Abstraction Licensing process. Evidence of an abstraction licence or a valid licence application will be required to be submitted with any planning application. Any boreholes seeking to provide less than 20m³ per day are exempt from Environment Agency licencing requirements, and the assessment of details sits with the local planning authority, in conjunction with local authority Environmental Health teams. The local planning authority is also responsible for considering whether certainty of supply is sufficiently demonstrated.

Ultimately, it is for a developer to provide sufficient information to the local planning authority to confirm that any proposed borehole is an acceptable form of mitigation. Please contact your local planning authority to obtain an understanding of what information is required. The requirements may change periodically depending on changes to environmental risk or evidence and/or planning policy.

Horsham District Council's Position

Our opinion is based on the information available to us at the time of the enquiry. When the formal planning application is submitted, our position may change if there have been changes to relevant policy or guidance.