Pol 03 - Flood and surface water management

Brownfield sites – achieving the greenfield rate of run-off for the 1-year and 100-year return period events - KBCN1450

For a brownfield site that has achieved the greenfield rate of run-off for the 1-year and 100-year return period events, criterion 6 can be deemed to be met.

Calculation of greenfield run-off rates - KBCN1352

The calculation of greenfield run-off rates must be in accordance with IH Report 124, Flood estimation for small catchments. Reference to the Flood Estimation Handbook can be made, but only where this is considered appropriate. This is only applicable to v3.0 of the UK NC 2018 technical manual and will be clarified in the next re-issue.

Erratum – UK NC2018 Pol 03 – Peak rate of run-off for greenfield sites - KBCN1063

The 30% improvement on the peak rate of run-off, required under criterion 6, is only applicable to Brownfield sites. Post-development, Greenfield sites are only required to achieve a peak rate of run-off that is no greater than the pre-developed site. The 2014 UK NC scheme required both Greenfield and Brownfield sites to not increase the peak rate of run-off as a result of the development. A 30% improvement for brownfield sites is in keeping with BREEAM's aim to continue to drive improvements and mitigate the impacts of development.

10/08/18 - Technical manual updated. Only relevant to v1.0 of the manual

Erratum – UK NC2018 Pol 03 – Prerequisite for Simple buildings assessments - KBCN1067

The prerequisite requiring the appointment of an appropriate consultant is applicable to Simple buildings assessments for the Flood resilience and Minimising watercourse pollution credits. The prerequisite must also be met if the two credits and exemplary credit are awarded for Simple Buildings achieving compliance to the Surface Water Run-off criteria. Refer to the text under 'Up to two credits - Simple Buildings - Surface water run-off'. The prerequisite does not, however, apply to the 'Simple buildings only' criteria 24-25. Assessment scope for a Simple building:

Flood Resilience - KBCN1478

In order to award two credits

Flood risk must be determined by a compliant, site-specific Flood Risk Assessment and cannot be based solely on on EA Flood Maps
The credits for flood risk are awarded based on the pre-development site

Sites which have a medium or high flood risk from one or more sources (pre-development) can only achieve one credit, subject to mitigation measures being implemented as part of the development. The criteria seek to encourage the development of sites in areas of low flood risk from all sources.

01/11/2021 Clarified: 'Sites which have a medium or high flood risk from one or more sources...'

Flood resilience – appropriate consultant - KBCN1453

Where compliance is only sought for criteria 2-4a, if the assessor is satisfied and can justify that the person conducting a flood risk assessment for the development has the appropriate level of knowledge to undertake it, then they do not need to meet the full definition of the 'appropriate consultant'.

Flood resilience – Pre-existing flood defences - KBCN1021

In an area protected by existing flood defences, (designed to withstand a certain magnitude of flooding), the appropriate number of flood risk credits can be awarded where the defences reduce the risk to ‘low’ or ‘medium’ and the following conditions are met: 1. The development is not located in an area where new flood defences have to be, or have been, constructed to minimise the risk of flooding to the site and its locality purely for the purpose of the development or its wider master plan. 2.The development is located on previously occupied land (as defined by the criteria in BREEAM issue LE 01 Site selection). 3.The relevant agency confirms that, as a result of such defences, the risk of a flood event occurring is reduced to low or medium risk. If firm confirmation is not provided then the credit cannot be awarded. A statutory body’s local or regional office may be able to provide more information on existing defences in the area in which the assessed development is located.

Flood resilience – Third party feature acting as flood defences - KBCN1022

There are many landscape feature defences, owned by third parties, which due to their location act as a flood defence by default, e.g. motorway, railway embankments, walls etc. It can be assumed that such embankments will remain in place for the lifetime of the development, unless the assessor or project team have reason to believe otherwise. For walls, assurance must be sought that the wall is likely to remain for the design life of the building.

Flood risk – Site situated across numerous flood zones - KBCN0532

Where a site is situated across more than one flood zone, the flood zone with the highest probability of flooding, i.e. the worst case scenario, must be considered for the purpose of the BREEAM assessment. An exception to this would be where the areas in the higher probability zone include only soft landscaping and it can be demonstrated that access to the building will be maintained in a flooding event. This is to ensure that the site has adequately managed the worst case scenario level of flood risk associated with the site's location.

22/07/2022 Applicability to HQM One confirmed
07/03/2018 Updated to include circumstances where an exception may apply.

GN38 Relating drainage reports to BREEAM UK NC 2018 - KBCN1564

Latest version: v1.2, January 2023 Guidance Note 38 (GN38) has been produced to help assist BREEAM Assessors relate the contents of drainage reports to the ‘Surface water run-off’ and ‘Minimising watercourse pollution’ criteria in Pol 03 for BREEAM UK New Construction 2018 and BREEAM UK New Construction Version 6. The guidance note does not cover the criteria for ‘Flood resilience’. Completing the template is optional. It is an aid for demonstrating compliance and not a requirement. A separate guidance note exists for BREEAM UK New Construction 2014 (see GN15). Download Guidance Note 38 View all Guidance Notes on BREEAM Projects (licensed assessors only)

31-Jan-2023 – Release of GN38 1.2. Fixes issue with incorrectly linked inputs (8c and 10a).

Greenfield/Brownfield site – Definition - KBCN1259

For the purposes of this Issue, the following definitions apply: Greenfield site A site which has never been built on, includes minimal development or which has been substantially cleared of all buildings and associated fixed surface infrastructure* and has subsequently remained undisturbed for five years or more. * Typically, the site includes less than 5% residual development by area. This supersedes the definition of 'Greenfield' for this Issue in the technical manual. Brownfield site Any site which does not fall within the above definition of 'Greenfield site'

Minimising water course pollution – no water courses present - KBCN0550

The credit for 'minimising water course pollution' has to be assessed even in cases where no water courses are in close vicinity to the site under assessment. This is because the aim of this credit is to encourage developments to minimise water course pollution by restricting the discharge of potentially contaminated water from entering the public sewer. Minimising water course pollution does not focus on water directly entering water courses.

Minimising watercourse pollution – end of pipe solutions - KBCN1025

End-of-pipe solutions, such as ponds and basins, will only be deemed to comply with the 5mm criteria where the principal run-off control, to prevent discharge from the first 5mm of a rainfall event, is achieved using source control and site control methods.

Minimising watercourse pollution – Extensions and infill developments - KBCN1027

When assessing an individual building on an existing site, i.e. infill development, the criteria apply to areas within the construction zone that present a risk of pollution as well as any areas outside the construction zone affected by the new works, eg. drainage onto or from the proposed development.

Minimising watercourse pollution – First 5mm of rainfall requirement - KBCN1059

It may not be possible for the first 5mm of rainfall to be prevented from leaving a site completely. An appropriately qualified professional must explain comprehensively why this criterion cannot be fully met and design a system to meet the intent of this criterion as far as possible. Where this can be justified and all other relevant criteria have been achieved, the credit can still be awarded.

Minimising watercourse pollution – Green roofs - KBCN1026

Rain that falls onto the surface of green roofs can contribute to this requirement. Evidence,however, still needs to demonstrate that the 5mm rainfall from all impermeable surfaces on-site is being dealt with.

No change in impermeable area - KBCN1273

The Methodology includes a section titled 'No change in impermeable area'. Where this text is applied to a site, and the Surface Water Run-off - Rate credit is not targetted, criterion 5 is not applicable because no calculations or surface water design solutions are required. Note: the design for exceedance criterion (criterion 10) must still be demonstrated.

Pollution Prevention Guidance documents - KBCN1051

On 17 December 2015, the Pollution Prevention Guidance documents (PPGs) published by the Environment Agency were withdrawn. These can be found in the National Archives or on the Scottish Environment Protection Agency website where they are still current documents. Many BREEAM schemes and the Home Quality Mark refer to these PPG documents as they are still considered to be best practice even though they have been withdrawn. Projects should continue to use the PPGs referenced in the relevant manuals. BREEAM will continue to review this situation and provide an update as and when appropriate.

26 09 2018 Made applicable to Man 03 and Pol 03 in UK NC2018 and Man 03 in UK NC 2011, UK NC2014 and UKRFO 2014

Relating drainage reports to BREEAM – GN15 and GN38 - KBCN1169

Guidance Note 15 (GN15) and Guidance Note 38 (GN38) have been produced to help assist BREEAM Assessors relate the contents of drainage reports to the ‘Surface water run-off’ and ‘Minimising watercourse pollution’ criteria in Pol 03. They do not cover the criteria for the ‘Flood resilience’. We have published two separate Guidance Notes because there are small, but significant, differences between the criteria in the two schemes (UK NC 2014 and UK NC 2018). This means that the Guidance Notes are not interchangeable:

GN15 can only be used for the assessment of BREEAM UK New Construction 2014.
GN38 can only be used for the assessment of BREEAM UK New Construction 2018 and BREEAM UK New Construction Version 6.

Note: Completing either template is optional. They are aids for demonstrating compliance and are not a requirement.

Surface water run-off – Derelict sites - KBCN1024

If the site has been derelict for over five years, the appropriate consultant must assess the previous drainage network and make reasonable assumptions to establish probable flow rates and volumes. They should use best practice simulation modelling to determine the 1 year and 100 year peak flow rates at the relevant discharge points. A site visit prior to development will be required unless accurate data already exists from a previous survey. The resultant professional report can then be used to determine the pre-development volumes and rates of run-off. Without this professional input, the site must be deemed as greenfield pre-development, assuming Soil type 5 for the calculation of the pre-development site run-off.

Surface water run-off – discharge to a tidal estuary or the sea - KBCN1023

The peak rate of run-off and volume run-off criteria can be deemed to be met if the site discharges rainwater directly to a tidal estuary or the sea. The site run-off must discharge directly into the tidal estuary or the sea. Typically, drainage pipes would only carry run-off from the site and would not need to cross privately owned land outside the boundary of the development before reaching the sea. A definition of tidal estuary is in the technical manual.

Surface water run-off – Highways and impermeable areas - KBCN1035

Where new non-adoptable highways are built, all new impermeable surfaces must be included in the calculations to demonstrate compliance with the peak rate of run-off and volume of run-off criteria. Where buildings are built beside existing highways or where adoptable highways are built, the impermeable area of the highway does not need to be included in the calculations.

Watercourse pollution from indoor parking - KBCN0545

If the design team can demonstrate that there will be absolutely no run-off from the indoor parking then the intent of the credit will be met. However, such proof would also have to demonstrate that no hydrocarbon spillage from vehicles found its way into the watercourse/sewer. It is likely that there would be water ingress from outside or that internal parking areas would have drains fitted and be cleaned regularly. In such conditions, the criteria are still applicable. The intent of this criteria is to ensure no hydrocarbons run off to any watercourse.

[KBCN withdrawn] ~ Surface water run-off – Rainwater harvesting - KBCN1064

This KBCN has been withdrawn and is no longer valid. This is because the BS 8515 has been withdrawn and its replacement makes no reference to storm water control.

KBCN withdrawn on 26/09/18:

BS 8515 Rainwater harvesting systems: Code of Practice, Annex A (236) must be followed where rainwater harvesting systems are relied upon for storm water control. To ensure flood risk is not increased if the rainwater harvesting system is, for some reason, unavailable, the exceedance flow route capacity provided in accordance with CIRIA report C635 should ignore the beneficial effect of the rainwater harvesting system.

New Construction / UK / 2018 / 09 Pollution /