Guidance

Protect groundwater and prevent groundwater pollution

Published 14 March 2017

If you’re carrying out an activity which could affect the quality or quantity of groundwater you will need to understand:

• what groundwater is
• how your activity might affect it

The Environment Agency will consider the geological characteristics of your location when it assesses your permit or licence application. You should consider your location when you plan your activities.

This guidance will help you with your permit or licence application.

1. Permission to discharge to or abstract from groundwater

Any discharge of pollutants which enter groundwater directly, or may enter into the soil and reach groundwater, is a groundwater activity.

If you carry out a groundwater activity you must have an environmental permit or an exemption or know the activity has an exclusion.

The Environment Agency can serve a notice to either prohibit or to require a permit for an activity on or in the ground that may lead to a discharge of pollutants to groundwater.

If you want to abstract (take) more than 20 cubic metres of water per day from an underground source you will need an abstraction licence.

You should consider your local water availability, location and other users when you plan your activities. Your local abstraction licensing strategy will help you see how much water is available in your area and so understand how likely your application is to be successful.

The Environment Agency will consider the geological characteristics of your location and the principles in the Environment Agency’s groundwater protection position statements when assessing your permit or licence application.

2. Groundwater definition

Water stored below rocks or other geological strata below the water table is called groundwater. The geological strata that hold water are called aquifers. Groundwater may rise to the surface through naturally occurring springs, or be abstracted using boreholes and wells. Groundwater may also naturally flow into rivers (called base flow) and support wetlands, forming part of local ecosystems.

The legal definition of groundwater is: ‘All water which is below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil.’

Aquifers are: ‘A subsurface layer or layers of rock or other geological strata of sufficient porosity and permeability to allow either a significant flow of groundwater or the abstraction of significant quantities of groundwater.’

3. Prevent groundwater pollution

You must not cause groundwater pollution.

There are 2 main ways pollution reaches groundwater:

• point source pollution
• diffuse pollution

Point source pollution comes mostly from spills, leaks and discharges at a single point or over a small area. It’s often easy to identify because it results from mainly isolated events or activities with a clear link to groundwater pollution.

Diffuse pollution is the most widespread cause of groundwater pollution. It’s often the result of cumulative impacts of small, undefined pollution events and general environmental pollution spread over the catchment area.

You must prevent pollution of groundwater by following the conditions of any permits or exemptions you have.

If an activity may cause serious or irreversible damage, the Environment Agency will apply the precautionary principle and assess circumstances using a potential worst case result. This is because once polluted, groundwater may take years to clean up.

4. Prevent hazardous substances from entering groundwater

You must prevent hazardous substances from entering groundwater.

Hazardous substances include:

• some pesticides
• oils
• petrol and diesel
• solvents
• arsenic
• mercury
• chromium VI

Find the confirmed list of hazardous substances on the Water Framework Directive UK TAG website.

The legal definition of hazardous substances in the Water Framework Directive is: ‘Substances or groups of substances that are toxic, persistent and liable to bio-accumulate, and other substances or groups of substances that give rise to an equivalent level of concern’.

If you want to dispose of hazardous substances onto the ground you need one of the following:

• an environmental permit
• an exclusion
• the Environment Agency’s agreement that the discharge is trivial

In all cases, hazardous substances must not reach groundwater.

5. Limit non-hazardous pollutants from entering groundwater

You must limit non-hazardous pollutants from entering groundwater so that they do not cause pollution.

A non-hazardous pollutant is defined as ‘any pollutant other than a hazardous substance’.

Non-hazardous pollutants include ammonia (found in sewage) and nitrates.

If you want to discharge non-hazardous pollutants to the ground you will need an environmental permit or exemption. You must not cause pollution.

6. Consider the geological characteristics of your location

The type of aquifer at your location will affect how vulnerable it is to pollution and how much is available to abstract.

Aquifer types are defined by:

• geological characteristics
• how much groundwater it is possible to extract, and how easily
• how much they support river flows and habitats

There are 4 aquifer types and each can be confined or unconfined:

• principal aquifers
• secondary aquifers
• secondary undifferentiated
• unproductive strata

6.1 Principal and secondary aquifers

Principal and secondary aquifers provide significant quantities of drinking water, and water for business needs. They may also support rivers, lakes and wetlands.

6.2 Secondary aquifers

Secondary aquifers are split into 2 groups:

• secondary A aquifers comprise permeable layers that can support local water supplies, and may form an important source of base flow to rivers
• secondary B aquifers are mainly lower permeability layers that may store and yield limited amounts of groundwater through characteristics like thin cracks (called fissures) and openings or eroded layers

6.3 Secondary undifferentiated aquifers

Secondary undifferentiated are aquifers where it is not possible to apply either a Secondary A or B definition because of the variable characteristics of the rock type. These have only a minor value.

6.4 Unproductive strata

Unproductive strata are largely unable to provide usable water supplies and are unlikely to have surface water and wetland ecosystems dependent on them.

You can find aquifer designations using Magic map. Search a location, then select ‘Aquifer Designation Map (Bedrock) (England)’ or ‘Aquifer Designation Map (Superficial Drift) (England)’ under ‘Landscape’ and ‘Geology and Soils’ in the table of contents .

6.5 Unconfined and confined aquifers

Aquifers can be unconfined or confined, or a mix of both.

An unconfined aquifer is when the upper surface of the aquifer (and water table) is open to the atmosphere either directly or through permeable overlying material. Because of this it’s more vulnerable to pollution than a confined aquifer.

A confined aquifer is overlain by a low permeability material (for example clay) that does not transmit water in any appreciable amount. It’s less vulnerable to pollution than an unconfined aquifer because there is greater protection.

See an illustration showing the differences between confined and unconfined aquifers.

If you want to read more about groundwater you can do so on the UK Groundwater Forum.

7. Groundwater vulnerability

This describes the vulnerability of groundwater to pollution and what, if any, natural protection exists. The risks of groundwater pollution from any given activity depend in part on the:

• physical, chemical and biological properties of the underlying soil and rocks
• depth and quality of soil
• presence of glacial sediment and other materials – known as ‘drift’
• depth of the unsaturated zone

All may affect how groundwater is more or less vulnerable to pollution.

There are 2 types of vulnerability:

• intrinsic vulnerability – this relates to the physical characteristics, it includes soil type, presence of drift, or rock type
• specific vulnerability – this relates to the effect of the proposed activity including any contaminant and consequent risk to groundwater

Use the groundwater vulnerability maps to assess the:

• effect on groundwater of an activity with pollution potential
• degree of protection provided by characteristics other than the soil layer

The maps show whether groundwater has a high, medium or low risk of pollution. They also show where there are principal aquifers that provide drinking water or support rivers, lakes and wetlands.

Groundwater vulnerability maps are a guide only. They do not show information on local activities such as quarrying or depth to the water table. You must gather site-specific information to complete a detailed assessment of the potential effects of any planned activity.

See an illustration showing 2 examples of groundwater vulnerability.

8. Restrictions within groundwater sensitive locations

The geological characteristics of your location will determine how your activity affects groundwater. You need to understand these characteristics so you can assess and manage the effect of your activity. The Environment Agency will also consider this when it assesses permit or licence applications.

If you are located within a sensitive location the Environment Agency may not grant you a permit or licence for certain activities. You should consider your location when you plan your activities.

In some locations the Environment Agency will require you to put additional measures in place to protect water quality and quantity before issuing a permit or licence.

You will need to identify whether you are within a sensitive location as part of your permit or licence application.

9. Sensitive groundwater locations

There are a series of protection zones for areas where pollution on or below the land may present a risk to groundwater. They help to define groundwater supplies and prioritise protection.

Access data and information on all the zones using Magic Map.

9.1 Drinking water protected areas (DrWPAs)

All groundwater bodies in England are designated as drinking water protected areas (DrWPAs). This aims to protect groundwater from over-abstraction and to prevent deterioration in groundwater quality that could increase the treatment of drinking water.

A body of groundwater is defined in the Water Framework Directive as a distinct volume of groundwater within an aquifer or aquifers. DrWPAs are required to be identified under the Water Framework Directive (2000/60/EC).

9.2 Source protection zones (SPZs)

The Environment Agency applies a general level of protection for all drinking water sources through the use of source protection zones (SPZs).

SPZs are used to define areas close to drinking water sources where the risk associated with groundwater contamination is greatest. SPZs are not statutory but they do relate to distances and zones defined in legislation where certain activities are restricted.

There are over 2,600 SPZs in England surrounding major abstraction sources.

For more information on activities which are restricted in SPZs see section B of Groundwater protection: GP3 position statements.

9.3 Defining SPZs in unconfined aquifers

SPZ1 inner protection zone – defined by a 50-day travel time for pollution from any point below the water table to reach the abstraction source. This zone has a minimum radius of 50 metres.

SPZ2 outer protection zone – defined by a 400-day travel time from a point below the water table. This zone has a minimum radius of 250 or 500 metres around the abstraction source, depending on the size of the abstraction.

SPZ3 source catchment protection zone – defined as the area around an abstraction source within which all groundwater can potentially feed into the abstraction source.

9.4 Defining SPZs in confined aquifers

For confined aquifers, the default distance for an SPZ1 is 50 metres. This provides protection for the head works around the abstraction borehole.

An SPZ2 is not generally defined, while SPZ3 is used for the catchment area.

For any subsurface activity, like deep drilling, further protection zones may apply. They extend the travel times where the aquifer becomes confined below overlying impermeable geological layers:

• Zone 1c extends the 50-day travel time zone
• Zone 2c extends the 400-day travel time zone

9.5 Safeguard zones (SgZs)

Safeguard zones (SgZs) are used for areas around abstractions where water quality is poor. An SgZ means that there will be strict enforcement of existing measures for particular pollutants and activities, and possibly new voluntary measures.

SgZs are based on existing SPZ1 and SPZ2. SgZs are not statutory designated areas but are where additional measures are needed to improve water quality. The Environment Agency establish SgZs under the Water Framework Directive.

There are over 200 groundwater SgZs in England.

9.6 Water protection zones (WPZs)

Water protection zones (WPZs) are a statutory designation of an area where measures can be specified to deal with sources identified as being at high risk. This allows the Environment Agency, once an order is made by government, to:

• apply measures in addition to other measures to manage
• stop activities that cause or could cause further damage or pollution to water

Currently there are no WPZs for groundwater.

9.7 Private water supplies

These may provide water to homes, businesses or services. It is more common to find private water supplies in rural areas. They’re independent of a water company and owners and users are responsible for them.

The source is often groundwater, through a well, borehole or spring, but the supply may also come from a stream, river, lake or pond.

The Private Water Supplies Regulations 2016 set out the legal standards and controls. Local authorities regulate private water supplies. The Drinking Water Inspectorate provides technical and scientific support to local authorities. Both hold details of private water supplies used for human consumption and food production purposes.

All private water supplies used for human consumption or food production purposes have an SPZ1 designation with a default radius of 50 metres. Note, food production purposes does not include routine irrigation of crops.

Details of private water supplies are not held on the interactive maps.

If you carry out a groundwater activity you must know if you are within 50 metres of a private water supply for human consumption or food production purposes.

Find out about private water supplies management on the Drinking Water Inspectorate website.

If you have a private water supply, tell your local authority to make sure you’re on the register.

10. Saline intrusion

Saline intrusion is the replacement of fresh groundwater by water that has a high salt content.

You will need to consider saline intrusion if you apply for a new, increased or changed abstraction regime in estuarial or coastal settings, or in inland areas where deep saline groundwater is present. Saline intrusion can be complex and difficult to predict so the Environment Agency will act with caution.

Saline intrusion is dealt with under the Water Framework Directive 2000/60/EC.

Saline water can occur naturally at the coast and is also present in deep aquifers and in natural spas. Due to the salt content, saline water is denser than fresh groundwater. Abstraction of overlying fresh groundwater can result in the intrusion of the deep saline water resulting in unusable drinking water.

In some cases, it is possible to use saline groundwater for industrial and manufacturing purposes.

More information on where and why saline intrusion from the sea occurs is available on the UK groundwater forum’s website.