Guidance

Mining and groundwater constraints for development

If you are developing a site within a coalfield area you may need to give additional consideration to the proposed drainage and infiltration.

If you are developing a site within a coalfield area you may need to give additional consideration to the proposed drainage and infiltration so that sustainable development and sustainable drainage systems (SuDS) may be appropriately designed and implemented.

The Coal Authority and Environment Agency have combined their data to create an online screening tool for Local Planning Authorities, developers and consultants to identify specific mining and groundwater related constraints.

After a specific constraint is identified using the NE Mining and Groundwater Constraints screening layer on the Coal Authority’s interactive map viewer, you’ll understand what action you need to take, have a better understanding of the drainage implications within the development proposals and when it would be beneficial to seek pre-consultation advice.

Currently the screening tool covers the majority North East England.

Mining and groundwater constraints categories

The following table provides a summary of the 5 categories used in the screening tool.

For each case the definition is followed by the implication.

A major development is defined in The Town and Country Planning (Development Management Procedure) (England) Order 2015

Category Criteria description Action summary
A Off the coalfield SuDS guidance and best practice for assessing pollution and flood risk should be followed. Groundwater should always be considered when designing drainage schemes
B On the coalfield area Specific requirements for major development and deep ground works or deep drainage boreholes
C 1 On the coalfield area with one, or both of: shallow mine workings, and nearby controlling outflow Major development and deep ground works or deep drainage boreholes require pre-application consultation with the Coal Authority
C 2 On the coalfield area with shallow mine water SuDS may not work, developer must suggest alternative methodologies or undertake detailed hydrogeological risk assessment or investigation, that require pre-application consultation with the Lead Local Flood Authority
D On the coalfield area with shallow mine water, and one, or both of: shallow mine workings, and nearby controlling outflow SuDS may not work, developer must suggest alternative methodologies or undertake detailed hydrogeological risk assessment or investigation, that will require pre-application consultation with the Coal Authority and the Lead Local Flood Authority

Check the constraint category of your development site

Use the Coal Authority’s interactive map viewer to see which category your site falls within, as well as which mine water block the site falls within.

Please activate the ‘NE Mining and Groundwater Constraints’ option to see this information.

Areas allocated as category A are considered to be off the coalfield and have not been mapped. Therefore, the interactive map only presents areas within categories B to D.

The specific constraints included on the screening tool are:

  • development site is on the coalfield
  • shallow mine water is present at the development site, or is predicted to be
  • shallow mine workings are present at the development site, or are predicted to be
  • controlled outflow nearby the development site

Action to take after checking constraint category

Actions may involve you liaising with:

  • Lead Local Flood Authority
  • Coal Authority licensing and permissions team
  • Environment Agency

Category A – off the coalfield

Follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater, to provide a fully justified risk assessment to support sustainable development.

Category B - no shallow mine workings, no nearby controlling outflow or shallow mine water present

Your project is not a major development

If your project is not a major development follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater, to provide a fully justified risk assessment to support sustainable development.

Your project is a major development but you are not proposing drainage boreholes deeper than 30 metres

If your site is a major development but you are not proposing drainage boreholes over 30 metres deep there is no specific consultation required. However, the impacts of the proposal and suitability of the subsurface coalfield environment should be considered. Follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater, to provide a fully justified risk assessment to support sustainable development.

Your project is a major development and you are proposing drainage boreholes deeper than 30 metres

Anthropogenic infiltration drainage schemes may result in flooding and pollution away from the proposed development, and may impact mine waters and assets operated by the Coal Authority.

Therefore infiltration rates of the development should be assessed and compared to greenfield or pre-development rates. Consider impacts of the development and suitability of the subsurface coalfield environment in terms of quantity, routing of water and the pollution risk.

Follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater.

Developers must undertake site specific flood and drainage assessment and the assessments need to consider current and future mine water and groundwater data.

Statutory consultation with the Lead Local Flood Authority regarding flood risk must also be undertaken.

Pre-application discussions with the Environment Agency are required regarding Environmental Permitting Regulations, where infiltration is directed to unsaturated coal measures strata.

If the proposals impact Coal Authority property or assets you are required to seek pre-application consultation with the Coal Authority.

Category C1 - shallow mining and/or controlling outflow present

Your project is not a major development and you are not proposing drainage boreholes deeper than 30 metres

If your project is not a major development and you are not proposing drainage boreholes deeper than 30 metres then follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater to provide a fully justified risk assessment to support sustainable development.

Your project is a major development or you are proposing drainage boreholes deeper than 30 metres

If your project is a major development or you are proposing drainage boreholes deeper than 30 metres SuDS that change the current infiltration rate, volume or location may impact on Coal Authority mine workings or other infrastructure.

Infiltration rates of the development should be assessed and compared to greenfield or pre-development rates. Consider the impacts of the development and suitability of the subsurface coalfield environment in terms of quantity, routing of water and the pollution risk.

Developers must undertake pre-application consultation with Coal Authority and site specific flood and drainage assessments. The assessments need to consider the current and future mine water and groundwater data, as rising mine waters may reduce the infiltration rate and efficiency of the infiltration SuDS over the design life of the drainage scheme.

Category C2 - shallow mine water present

If there is no hydraulic connection to the mine workings, for example a mine entry, pathway or borehole, including site investigation works, no specific consultation is required.

However, impacts of the proposal and suitability of the subsurface coalfield environment should be considered.

Follow CIRIA’s SuDS manual (C753) for assessing pollution and flood risk on controlled waters, including groundwater, to provide a fully justified risk assessment to support sustainable development.

If there is hydraulic connection to the mine workings, for example a mine entry, pathway or borehole, including site investigation works, infiltration SuDS may not work either now, or in the future. All SuDS could be impacted by mine water.

The developer should suggest alternative methodologies and must undertake pre-application consultation with the Coal Authority and pre-consultation with Lead Local Flood Authority for drainage proposals, other than drainage to the network.

Category D - meets the criteria for both C1 and C2

Infiltration SuDS may not work now, or in the future, as any SuDS could be impacted by mine water.

The developer should suggest alternative methodologies and must undertake pre-application consultation with the Coal Authority and pre-consultation with the Lead Local Flood Authority for drainage proposals other than drainage to the network.

When category modifications are required

It is important to utilise all available site specific information to determine the effective category for the development. In practice this means modifying the category shown on the map to take account of additional mining features. Such additional features, or constraints, may be identified either at a desk study phase or during ground investigations.

Some data sets provided by the Coal Authority on its interactive map viewer can be used to identify recorded mining features, which may act as pathways. Unrecorded mining features are not included in available data sets, and these cannot be identified through desk study alone.

Ground investigation is needed to identify the presence of any additional constraints such as formerly unrecorded mine entries and other mine workings and features. The table explains how you should modify the mapped categories depending which extra mining features are found on your site.

Mapped category Additional mining features found to be present on site Modified, effective category
A Within Coal Mining Reporting Area B
B Any potential pathway including unrecorded shallow coal mine workings, mine entry, coal seam outcrop, surface mining including opencast backfill or high wall, fissures and breaklines, geological fault C1
B Shallow mine water C2
B Minor discharge of mine water connected to workings underlying the site C1
C1 Shallow mine water D
C2 Any potential pathway including unrecorded shallow coal mine workings, mine entry, coal seam outcrop, surface mining including opencast backfill or high wall, fissures and breaklines, geological fault D
C2 Minor discharge of mine water connected to workings underlying the site D

It is possible for your site to be initially categorised as A or B, but ultimately be modified to Category D if you find both shallow mine water and one of the pathway features.

Mine water block factsheets

Each defined mine water block has an associated factsheet providing additional information which you should consider during your site specific assessment.

We recommend you read the relevant factsheet prior to liaising with other organisations.

Search mine water block factsheets

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Published 14 November 2018