New Construction / UK / 2014 / 09-Pollution /

Pol 03 - Surface water run-off

Information correct as of 2ndAugust 2021. Please see kb.breeam.com for the latest compliance information.

Adoption of road in the development - KBCN0331

Where a development includes roads, these are often adopted by a statutory authority (for example the Highways agency or the local authority in the UK). Where the authority will be taking responsibility for the roads, the following guidance should be followed to determine if the water run-off from the roads needs to be considered as part of the assessment: Where the authority will NOT be taking responsibility for the roads, the BREEAM criteria should be followed for all drainage on site.  

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. 
07/03/2018 Updated to include circumstances where an exception may apply.

Flood risk assessments to National Planning Policy Framework - KBCN0901

The National Planning Policy Framework (NPPF) is made up of a number of Planning Practice Guidance (PPG) documents.  This means that flood risk assessments that confirm they follow the NPPF can be accepted as being compliant to all relevant PPGs (for example PPG Flood Risk and Coastal Change).

GN15 Relating drainage reports to BREEAM - KBCN0629

this KBCN has been superseded. Please refer to KBCN1169.
Superseded 07/09/18

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.

No discharge for up to 5mm rainfall - KBCN0599

The criterion requires no run-off to leave the developed site into the local watercourse(s) for a storm event that results in rainfall depths up to 5mm.  It is not acceptable to collect the rainfall within an attenuation tank and allow the runoff to be released from the site at a restricted rate. This simply slows the rate at which it is released to the watercourse(s). The 5mm rainfall event is considered one of the most common rainfall events and, therefore, a system should be designed to prevent this run-off leaving the site thus protecting a receiving watercourse from pollution.

Relating drainage reports to BREEAM – GN15 and GN38 - KBCN1169

The purpose of these guidance notes is 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. 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. Note: Completing either template is optional. They are aids for demonstrating compliance and are not a requirement. View GN15 here and GN38 here. (licensed assessors only) View all Guidance Notes (licensed assessors only)

Surface water run-off – no change in impermeable area - KBCN1212

CN 3.9 states: "Where the man-made impermeable area draining to the watercourse (natural or municipal) has decreased or remains unchanged post-development, the peak and volume rate of run-off requirements for the surface water run-off credits will be met by default… In this instance a flood risk assessment must be carried out and any opportunities identified to reduce surface water run-off are implemented." Where the flood resilience credits are not being targeted, a flood risk assessment is not required. Instead, a separate study identifying opportunities to reduce surface water run-off may be carried out, and the measures implemented. Where there is no change in impermeable area, opportunities should be identified to reduce run-off. It is not necessary to carry out a flood risk assessment to fulfill the intent of this criteria.

Surface water run-off not flooding property - KBCN0565

Where parts of a site may flood in the event of local drainage system failure, it is still possible to demonstrate compliance if the building itself will not be at risk of flooding.  

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] ~ Flood risk – Environment Agency (EA) confirm the site is in ‘low flood risk’ area This KBCN has been withdrawn and is no longer valid. This is because its content was created on the basis of a very specific case and should not be applied generally. EA confirmation is no more robust or detailed than reference to flood maps, which are not in themselves compliant without a FRA.
KBCN withdrawn on 17/03/17:

If the EA have confirmed, in writing, that the site has a low flood risk and that a Flood Risk Assessment (FRA) is not required then this is acceptable and the two credits can be awarded. The EA's written confirmation is a sufficient indication that an appropriate level of flood risk assessment has been completed. Please note that the use of the EA flood maps without this additional confirmation is not acceptable.

Information correct as of 2ndAugust 2021. Please see kb.breeam.com for the latest compliance information.