Supporting documents to proposed Main Modifications and Additional Modifications

RE: Norfolk Minerals and Waste Local Plan: Publication of proposed Main Modifications and Additional Modifications
Thank you for consulting the Water Management Alliance (WMA) on the Norfolk Minerals and Waste Local Plan: Publication of proposed Main Modifications and Additional Modifications.
Parts of Norfolk coincide with parts of the Internal Drainage Districts (IDD) of the Broads (2006) Internal Drainage Board (IDB), King’s Lynn IDB, Norfolk Rivers IDB and the Waveney, Lower Yare and Lothingland IDB, members of the WMA. Therefore, the Board’s Byelaws apply to any development within a Board’s area.
The principal function of the IDBs is to provide flood protection within the Board’s area. Certain watercourses within the IDD receive maintenance by the Board. The maintenance of a watercourse by the IDB is an acknowledgement by the Board that the watercourse is of arterial importance to the IDD. Main Rivers within the IDB are regulated by the Environment Agency. Therefore, I recommend that an applicant proposing a discharge or any other works affecting a main river to contact the Environment Agency.
The area outside the Boards’ IDDs falls within the Boards’ watershed catchments (meaning water from the site will eventually enter the IDD). The Board will comment on planning for all major developments (10 or more properties) within the IDD watershed that are likely to discharge surface water into a watercourse within the IDD. Under certain circumstances, some major developments outside the IDD boundary may also be regulated by the Board’s byelaws. We request that the Board is consulted as any planning application comes forward relating to any of the identified allocation sites. For any development site, we recommend that a drainage strategy is supplied which has been considered in line with the Planning Practice Guidance SuDS discharge location hierarchy [https://www.gov.uk/guidance/flood-risk-and-coastal-change].
Whilst the Board’s regulatory process (as set out under the Land Drainage Act 1991 and the Board’s Byelaws) is separate from planning, the ability to implement a planning permission may be dependent on the granting of any required Land Drainage Consents. As such I strongly recommend that the required consent is sought prior to determination of the planning application.
Please see the list overleaf of the proposed sites for development which we consider may impact a Board’s area. The Board would seek to comment on these should they come forward for planning permission, alongside an explanation of any potentially required consents should these sites be developed. Please note that this list is not exhaustive and the Board may or may not choose to comment on additional site allocations if and when more information is presented.

MIN 12 – near Norfolk Rivers IDD
MIN 08/51/13 – near Norfolk Rivers IDD
MIN 64 – near Norfolk Rivers IDD
MIN 37 – near Norfolk Rivers IDD
MIN 65 – near Norfolk Rivers IDD
MIN 96 – near Norfolk Rivers IDD
MIN 202 – near Norfolk Rivers IDD
MIN 06 – near King’s Lynn IDD
MIN 40 – adjacent to King’s Lynn IDD
SIL 01 – near King’s Lynn iDD
MIN 115 – near Norfolk Rivers IDD
MIN 25 – near Waveney, Lower Yare and Lothingland IDD
Minerals and waste works close to a Board’s boundary may impact the IDD either directly or indirectly, therefore the Board would comment to promote sustainable drainage. Consent may be required if a discharge is proposed to a Board’s IDD.
For developments outside a Board’s IDD but within its watershed catchment, where surface water discharges have the potential to indirectly affect the Board’s IDD, we would offer the following advice:
• If it is proposed that a site disposes of surface water via infiltration, we recommend that the viability of this proposal is evidenced. As such we would recommend that the proposed strategy is supported by ground investigation to determine the infiltration potential of the site and the depth to groundwater. If on-site material were to be considered favourable then we would advise infiltration testing in line with BRE Digest 365 (or equivalent) to be undertaken to determine its efficiency.
• If it is proposed to discharge surface water or product of dewatering to a watercourse within the watershed catchment of the Board’s IDD, we request that this discharge is facilitated in line with the Non-Statutory technical standards for sustainable drainage systems (SuDS) [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/415773/sustainable-drainage-technical-standards.pdf], specifically S2 and S4. Resultantly we recommend that the discharge from this site is attenuated to the Greenfield Runoff Rates wherever possible.
For your information and in case of any allocated site being altered to be (or new site being proposed) within a Board’s IDD, in order to avoid conflict between the planning process and the Board's regulatory regimes and consenting processes where developments may be proposed within or partially within a Board’s IDD, please be aware of the following:
Byelaw 3 - Discharge of Surface Water or Product of Dewatering into a Board’s District
• If a development proposes to dispose of surface water via infiltration, we would recommend that the proposed strategy is supported by ground investigation to determine the infiltration potential of the site and the depth to groundwater. If on-site material were to be considered favourable then we would advise infiltration testing in line with BRE Digest 365 (or equivalent) to be undertaken to determine its efficiency.
• If (following testing) a strategy wholly reliant on infiltration is not viable and/or a development proposes to discharge surface water to a watercourse, the proposed development will require consent in line with the Board’s byelaws (specifically byelaw 3). Any consent granted will likely be conditional, pending the payment of a Surface Water Development Contribution fee, calculated in line with the Board's charging policy (available at https://www.wlma.org.uk/uploads/WMA_Table_of_Charges_and_Fees.pdf ).
• If a development proposes to discharge surface water to a sewer, I recommend that you satisfy yourselves that this proposal is in line with the drainage hierarchy (as per best practice) and is viable in this location.
Byelaw 3 - Discharge of Treated Foul Water into a Board’s District
• If a development proposes to discharge treated foul water to a watercourse, this proposal will require land drainage consent in line with the Board’s byelaws (specifically byelaw 3).
Byelaw 10 - Works within 9m of Board Maintained Watercourse/s
• Should any development include works within 9 metres of a Board maintained watercourse, consent would be required to relax Byelaw 10 (no obstructions within 9 metres of the edge of drainage or flood risk management infrastructure).
Byelaw 10 & 17 - Works within 7m of Board Maintained Watercourse/s and Works within the banks of Board Maintained Watercourse/s (applicable only in Waveney, Lower Yare and Lothingland IDB)
• Should any development include works within 7 metres of a Board maintained watercourse, consent would be required to relax Byelaw 10 (no obstructions within 7 metres of the edge of drainage or flood risk management infrastructure).
• If the proposal includes works to install services within, make excavations within, or otherwise alter the banks of the aforementioned Board Maintained Watercourse, consent will be required as per Byelaw 17 of the Board’s Byelaws.
Section 23 of the Land Drainage Act (1991) and Byelaw 4 - Alterations to a Watercourse
• Should any development include works to alter a Board maintained or riparian owned and maintained watercourse, consent will be required under the Land Drainage Act 1991 (and byelaw 4).
The reason for our recommendation is to promote sustainable development within the Board’s Watershed Catchment therefore ensuring that flood risk is not increased within the Internal Drainage District (required as per paragraph 167 of the National Planning Policy Framework). For further information regarding the Board’s involvement in the planning process please see our Planning and Byelaw Strategy, available online.
If you require any further information or would like to discuss the Board’s regulation in more detail, please do not hesitate to contact us.