Report to: 
	
South Cambridgeshire District Council Planning Committee 	9 Sept 2020	
Lead Officer:
	
Joint Director of Planning and Economic Development  	

S/3215/19/DC – Longstanton (The Retreat, Fews Lane, Longstanton, CB24 3DP)

Proposal: Discharge of condition 4 (foul water drainage) and 5 (surface water drainage) of planning permission S/2937/16/FL

Applicant: Mr Gerry Caddoo, Landbrook Homes Ltd

Key material considerations: Foul Water Drainage, Surface Water Drainage and Flood Risk

Date of Member site visit: None

Is it a Departure Application?: No

Decision due by: 11 December 2019

Application brought to Committee because: This application has been referred to the Committee on the basis of a Parish Council objection, third party objections and the public interest in this application.

Presenting officer: Emma Ousbey

Executive summary

1.	Planning permission S/2937/16/FL was previously allowed on appeal for the erection of a 3no. bedroomed dwelling with parking on 27 September 2018. This current application seeks the discharge of condition 4 of S/2937/16/FL, which requires the submission of full details of the foul water drainage strategy for written approval by the local planning authority. The application also seeks discharge of condition 5 of S/2937/16/FL, which requires the submission of full details of the proposed surface water drainage, both from the building itself and from the proposed driveway area for written approval by the local planning authority. Both conditions were imposed by the Planning Inspector on the decision notice in order ‘to prevent flooding’.

2.	The submitted details, as amended, have been reviewed and assessed by officers and a drainage consultant appointed to review the submission on behalf of the local planning authority. A detailed report prepared by this consultant has been appended to this report for Members to consider as part of their review of this application. 

3.	Longstanton Parish Council objects to the discharge of condition 5. Third party representations have been received objecting to the discharge of both condition 4 and condition 5. Numerous concerns have been raised, as summarised, in respect of technical details relating to the proposed foul water and surface water drainage; accordance of the proposals with the surface water drainage hierarchy; accordance of the proposals with adopted Local Plan policies CC/7, CC/8 and CC9, as well as national policy and guidance; lack of information; that the proposals will increase water runoff into Longstanton Brook increasing flood risk; that the proposed surface water runoff will be greater than the existing runoff rate for this site (as undeveloped); and that the proposed outfall into the existing watercourse is outside of the red line application boundary. 

4.	Both officers and the appointed drainage consultant are satisfied that the proposed submission details are in accordance with adopted national and local policy and guidance. It is considered that it has been satisfactorily demonstrated that the scheme provides a viable and fully justified foul and surface water drainage strategy that will not increase flood risk elsewhere. In officers’ judgment, the extension (if any) of the development beyond the red line boundary would be de minimis, and in any event into an area within the same ownership as the site. Even if the development could be said to extend beyond the red line boundary, it would not be appropriate or proportionate, nor in the public interest, to require a planning application to extend the red line in those circumstances. 

5.	Members are therefore requested to support the application. 
Relevant planning history

6.	Applications relating to the application site:

S/2439/18/FL – The erection of a 3 bedroom bungalow with parking - Approved
S/2937/16/FL – Proposed erection of a 3-bedroomed bungalow and parking – Allowed on appeal
S/0999/14/FL – Extension and alteration to existing bungalow to provide a house with ground, first and second floors (second floor attic rooms) – Approved
S/2561/12/FL – Erection of two bungalows - Approved

7.	Applications adjacent to the application site:

20/02453/S73 – Variation of condition 7 (traffic management plan) pursuant to planning permission S/0277/19/FL to reflect the proposals in the traffic management plan to substitute the current wording with ‘the development hereby permitted shall be carried out in accordance with the traffic management plan prepared by SLR consulting, version Final 1 and dated December 2019’. – pending consideration
S/0277/19/COND9 – Condition 9 – foul and surface water drainage – pending consideration
S/0277/19/CONDA – Submission of details required by condition 11 (scheme that demonstrates a minimum of 10% carbon emissions) and 12 (water conservation strategy) of planning permission S/0277/19/FL – pending consideration 
S/4471/19/DC – Discharge of condition 7 (traffic management plan) pursuant to planning permission S/0277/19/FL – pending consideration 
S/3875/19/DC – Discharge of conditions 4 (hard and soft landscaping), 6 (boundary treatment), 9 (foul and surface water drainage), 11 (renewable energy) and 12 (water conservation) pursuant to planning permission S/0277/19/FL - Refused
S/2508/19/DC – Discharge of condition 7 (traffic management plan) pursuant to planning permission S/0277/19/FL - Refused
S/0277/19/FL – Demolition of the existing bungalow and construction of two dwellings including car parking and landscaping - Approved
S/1059/16/DC – Discharge of condition 3 (materials), 4 (boundary treatment), 5 (hard and soft landscaping), 7 (surface water drainage), 8 (finished floor levels), 13 (traffic management plan) and 14 (archaeology) of S/1498/15/FL - Approved
S/1498/15/FL – Erection of two dwellings – Approved
Planning policies

8.	National Planning Policy Framework (2019) (NPPF)
National Planning Practice Guidance (PPG)

9.	South Cambridgeshire Local Plan 2018
S/1 Vision
S/2 Objectives of the Local Plan
S/3 Presumption in Favour of Sustainable Development 
HQ/1 Design Principles
CC/7 Water Quality
CC/8 Sustainable Drainage Systems
CC/9 Managing Flood Risk

10.	Greater Cambridge Sustainable Design and Construction Supplementary Planning Document (SPD) 2020
Cambridgeshire Flood and Water SPD 2016
Consultation

11.	Longstanton Parish Council:
Comments received 11 August 2020: Continue to object to this application as it continues to propose discharge of the surface water drainage directly into the village watercourse which is in contravention of policies CC8 and CC9 of the South Cambridgeshire Local Plan.

Comments received 15 October 2019: recommend this application for objection as it proposed to discharge the surface water drainage directly into the village watercourse which is in contravention of planning condition 5 requiring surface water drainage to be filtered through soil. Longstanton Parish Council support the comments made to the planning authority by neighbours in the letter dated 8 October 2019. 

12.	SCDC Sustainable Drainage Engineer: comments dated 26 October 2019 – the condition can be discharged in full. 

13.	Anglian Water: comments dated 26 June 2020 and 1 July 2020 - the foul water drainage strategy is acceptable to Anglian Water, we can therefore recommend the discharge of condition 4. The surface water drainage strategy does not involve discharge to Anglian Water owned assets, we therefore have no comments to make regarding the discharge of condition 5. 

14.	Stantec consultants, appointed on behalf of Greater Cambridge Shared Planning Service to provide further specialist drainage advice: full report of 20 August 2020 has been attached and is provided at Appendix A. Their report concludes that:

-	Based on the information submitted we find that it has been satisfactorily demonstrated that the scheme can provide a viable drainage strategy that will not increase flood risk elsewhere.
-	We conclude that the application would accord with policy CC/7, for foul drainage.
-	We conclude the application would accord with policies CC/7, CC/8, CC/9 for surface water drainage.
-	We recommend the applicant undertakes ordinary watercourse consent prior to the installation of the outfall arrangement. 
-	The future owner will need to be informed on the location of the underground storage tank, the maintenance responsibilities for the tank and covenant to ensure the driveway remains permeable in the future. 
-	The submission is considered consistent with the Cambridgeshire Flood and Water SPD for design of surface water drainage and paragraph 163 of the NPPF, which requires local planning authorities, when determining any planning applications, to ensure that flood risk is not increased elsewhere.
-	We recommend the discharge of conditions 4 and 5 for the site. 
Representations from members of the public

15.	Representations have been received from The Elms, Fews Lane dated 18 October 2019 and The Fews Lane Consortium dated 8 October 2019; 2 June 2020; 13 July 2020; 16 July 2020 and 13 August 2020 in relation to the application. The following concerns have been raised (as summarised):

-	Object to the discharge of any part of condition 5 (surface water drainage) 
-	Details provided with this application are insufficient to assess whether the surface water scheme proposed complies with relevant local and national policies.
-	Reconsultation should be undertaken to allow consultees to make representations on the application as amended.
-	Condition 4 proposes discharge of foul water into the public sewerage system, but no evidence has been provided to demonstrate that the existing public sewerage system has capacity for the additional flows from the proposed development or that discharge into the public sewerage system has been agreed with the relevant sewerage undertaker. 
-	Surface water drainage arrangements fail to comply with policies CC/7, CC/8 and CC/9 of the Local Plan.  
-	No surface water drainage arrangements for the proposed driveway are shown on the submitted plans. Unclear if it is intended that permeable paving should be used to discharge the driveway surface water by infiltration. Minimum information required typically includes infiltration testing conducted in accordance to BRE Digest 365, including plan showing locations of tests. If infiltration is suitable for the driveway area of the site, no explanation has been submitted as to why it is not being used to discharge the surface water from the building. 
-	Council’s drainage consultation response fails to consider the relevant particulars of the development proposed, the applicable local and national policies and basic principles of sustainable urban drainage system design. 
-	Drainage consultation comments for S/3875/19/DC comment on the arrangements under this application, stating ‘the dwelling towards the north appears too close to the watercourse to enable soakaways to be positioned 5m from the dwelling without impacting on the hedge and bank of the watercourse’. There are numerous locations within the application site greater than 5m from the building foundations. The 5m rule is a rough rule of thumb that can be assumed safe for any building on any type of soil. Without proper geotechnical assessment it may be possible in many soils to install infiltration features and traditional soakaways much closer to the foundations. 
-	The following three material considerations preclude the discharge of condition 5:
1)	The scheme proposes an increase in surface water discharge from the site into Longstanton Brook from the pre-development discharge volume, thereby increase the flood risk of nearby properties. Contrary to the stated reason for the condition ‘to prevent flooding’. 
2)	Scheme positions the outfall for surface water drainage system outside of the red line boundary of the site. An application to discharge a planning condition cannot extend the boundaries of land to which planning permission relates.
3)	The relevant polices of the development plan are a material consideration and policies CC/8 and CC/9 of the Local Plan militate against approval of the application. 
-	Planning conditions are to be interpreted in a common sense way, having regards to the underlying purpose for the condition as is demonstrated by the reasons stated for the imposition of the condition or conditions in question (R (Sevenoaks District Council) v Secretary of State [2004] EWHC 771 (Admin)).
-	The Appeal Decision granting permission in regards to application reference S/2937/16/FL states that, “in particular, conditions relating to foul and surface water drainage are necessary, to prevent flooding”.
-	However, under the scheme submitted by the applicant, the risk of flooding to nearby properties would actually be increased because the runoff volume from the development to the nearby surface watercourse for nearly all rainfall events would exceed the runoff volume for the same event prior to redevelopment.
-	The increase in surface water proposed to be discharged from the site would flow into Longstanton Brook, which has an extensive history of flooding.
-	The relevant local and national planning policies indicate that development of brownfield sites should seek to reinstate greenfield runoff rates wherever possible and, in any case, that the post-development discharge rate should never exceed the rate of discharge from the development prior to redevelopment.
-	The land proposed to be used for the outflow of the surface water drainage system falls outside the red line boundary on the location plan identifying the land to which the planning permission relates. No planning permission has been granted for any development to take place in, on, over, or under land outside of the boundaries of the application site.
-	If the applicant wishes to extend the red line boundaries of the application site to include the land proposed for the surface water outflow, an application must be submitted under section 73 of the 1990 Act. The Council cannot use an application to discharge a planning condition to effect the same result that would properly be effected through an application submitted under section 73 of the 1990 Act.
-	Policy CC/8 of the Local Plan 2018 states that: “Development proposals will be required to demonstrate that […] surface water drainage schemes comply with Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems and the Cambridgeshire Flood and Water Supplementary Planning Document or successor documents.”
-	Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems states in paragraph S3 that: “For developments which were previously developed, the peak runoff rate from the development to any drain, sewer or surface water body for the 1 in 1 year rainfall event and the 1 in 100 year rainfall event must be as close as reasonably practicable to the greenfield runoff rate from the development for the same rainfall event, but should never exceed the rate of discharge from the development prior to redevelopment for that event.”
-	Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems states in paragraph S5 that: “Where reasonably practicable, for developments which have been previously developed, the runoff volume from the development to any highway drain, sewer or surface water body in the 1 in 100 year, 6 hour rainfall event must be constrained to a value as close as is reasonably practicable to the greenfield runoff volume for the same event, but should never exceed the runoff volume from the development site prior to redevelopment for that event.”
-	The Cambridgeshire Flood and Water Supplementary Policy Document states in paragraph 6.3.8 that: “Brownfield (previously developed land) sites must reduce the existing runoff from the site as part of the redevelopment. Where possible, in order to provide betterment, redevelopments should look to reinstate greenfield runoff rates.”
-	Under the scheme submitted by the applicant, the peak runoff rate of discharge from the development to the nearby surface watercourse would exceed the peak runoff rate of discharge of the site prior to redevelopment, which is contrary to policy CC/8 of the Local Plan 2018, contrary to paragraph S3 of Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems, and contrary to paragraph 6.3.8 of the Cambridgeshire Flood and Water Supplementary Policy Document.
-	Under the scheme submitted by the applicant, the runoff volume from the development to the nearby surface watercourse for the 1 in 100 year, 6 hour rainfall would exceed the runoff volume for the same event prior to redevelopment, which is contrary to policy CC/8 of the Local Plan 2018 and contrary to paragraph S5 of Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems.
-	Policy CC/9 of the Local Plan 2018 states that: “In order to minimise flood risk, development will only be permitted where: […] The destination of the discharge obeys the following priority order: i. Firstly to the ground via infiltration ii. Then, to a water body; iii. Then, to a surface water sewer; iv. Discharge to a foul water or combined sewer is unacceptable.”
-	The information submitted by the applicant indicates that opportunities to use infiltration to discharge the surface water collected from the impermeable areas of the proposed development have not been adequately explored.
-	It is a material consideration that the applicant owns other land immediately adjoining the application site that could be used to discharge the collected surface water through infiltration. (See Section 72(1) of the Town and Country Planning Act 1990.)
-	Policy CC/9 of the Local Plan 2018 states that, “In order to minimise flood risk, development will only be permitted where: […] there would be no increase to flood risk elsewhere”. The increase in surface water proposed to be discharged from the site would flow in Longstanton Brook, which has an extensive history of flooding. This would be contrary to policy CC/9 of the Local Plan 2018.
-	Policies CC/8 and CC/9 of the Local Plan 2018 clearly militate against the approval of the details submitted with this application. Pursuant to section 38(6) of the Planning and Compulsory Purchase Act 2004, “If regard is to be had to the development plan for the purpose of any determination to be made under the planning Acts the determination must be made in accordance with the plan unless material considerations indicate otherwise.”
-	The Fews Lane Consortium Ltd has received legal advice that residential gardens within built-up areas are classified as greenfield land for planning purposes, not brownfield land, as was implied in the Consortium’s letter dated 13 July 2020.
-	Whilst this does not change the substance of the Consortium’s objections to the proposed development, it does mean that different paragraphs of Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems and the Cambridgeshire Flood and Water Supplementary Policy Document should have been quoted in the Consortium’s representations.
-	Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems states in paragraph S2 that: “For greenfield developments, the peak runoff rate from the development to any highway drain, sewer or surface water body for the 1 in 1 year rainfall event and the 1 in 100 year rainfall event should never exceed the peak greenfield runoff rate for the same event.”
-	Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems states in paragraph S4 that: “Where reasonably practicable, for greenfield development, the runoff volume from the development to any highway drain, sewer or surface water body in the 1 in 100 year, 6 hour rainfall event should never exceed the greenfield runoff volume for the same event. “
-	The Cambridgeshire Flood and Water Supplementary Policy Document states in paragraph 6.3.6 that: “All new developments on greenfield land are required to discharge the runoff from the impermeable areas at the same greenfield runoff rate, or less than, if locally agreed with an appropriate authority or as detailed within the local planning policies of District and City Councils.”
-	Under the scheme submitted by the applicant, the peak runoff rate of discharge from the development to the nearby surface watercourse would exceed the greenfield runoff rate for the 1 in 1 year and 1 in 100 year rainfall events, which is contrary to policy CC/8 of the Local Plan 2018, contrary to paragraph S2 of Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems, and contrary to paragraph 6.3.6 of the Cambridgeshire Flood and Water Supplementary Policy Document.
-	Under the scheme submitted by the applicant, the runoff volume from the development for the 1 in 100 year, 6 hour rainfall event would exceed the greenfield runoff volume for that event, which is contrary to policy CC/8 of the Local Plan 2018 and contrary to paragraph S4 of Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems.
-	The use of Sustainable Drainage Systems (“SuDS”) and the ability to integrate appropriate SuDS features into any development should be considered from the earliest phases of site selection and design. When considered at the appropriate time early in the design process, even the smallest sites can effectively integrate SuDS features, which can provide benefits in terms of reduced flood risks and provide positive contributions in terms of landscaping, residential amenity, and opportunities to enhance biodiversity.
-	In the case of this development, no consideration was given to the issues of surface water drainage at the design phase, and as a result, the applicant has proposed to discharge the collected surface water into the village’s watercourses.
-	The proposed rate of attenuation of discharge is insufficient and would result in an increased volume and rate of surface water discharge from the site, which would increase the risk of flooding elsewhere. This outcome is contrary to the inspector’s stated reason for imposing the surface water condition, which was to prevent flooding.
-	The applicant has failed to consider any of the numerous options to discharge the collected surface water through infiltration. The details submitted by the applicant are also, by objective measures, contrary to policies CC/8 and CC/9 of the development plan.
-	Having failed to consider appropriate SuDS solutions at the design phase, the applicant cannot now reasonably expect the Council to approve details that are contrary to the relevant policies of the development plan and that would increase the risk of flooding. This application should therefore be refused by the Council.

16.	 Full copies of all representations can be viewed on the public file available online. 
The site and its surroundings

17.	The application site is within the development framework boundary of Longstanton village. It lies outside of the conservation area and sits to the rear of ‘The Retreat’, an existing bungalow of late 1960s masonry and tile construction. Extant planning permission exists for the demolition of ‘The Retreat’ and replacement with 2no. dwellings (S/0277/19/FL). To the west of the application site are 2no. recently constructed dwellings (S/1498/15/FL). The application site is currently residential garden associated with ‘The Retreat’ and benefits from planning consent for the erection of a 3-bedroom bungalow with parking (S/2937/16/FL). 

18.	The application site is accessed off the High Street via Fews Lane, an unadopted access drive and public right of way. Immediately to the north of the garden lies an existing watercourse (ditch) which outfalls into the Longstanton Brook.  The site lies within Flood Zone 1 and therefore has a low probability of flooding from rivers and sea. The Environment Agency Surface Flood Water Map shows that this site is in an area of Low to Very Low Surface Water Flood Risk. Longstanton Brook is shown nearby to be at medium to high risk of surface water flooding. 
The proposal

19.	Planning permission S/2937/16/FL was allowed on appeal at this site for the erection of a 3-bedroomed bungalow with parking. This permission was granted subject to the following pre-commencement conditions which are now sought to be discharged under this current application:

Condition 4 – no construction work shall be commenced until full details of the proposed arrangements for foul water drainage have been submitted to the local planning authority and approved in writing. The new dwelling shall not be occupied or brought into use until the foul water drainage system has been installed and made operational, in accordance with these approved details. 

Condition 5 – no construction work shall be commenced until full details of the proposed surface water drainage, both from the building itself and from the proposed driveway area, have been submitted to the local planning authority and approved in writing. The new dwelling shall not be occupied or brought into use until the surface water drainage system has been installed and made operational, in accordance with these approved details. 

20.	In imposing these conditions the Planning Inspector states, ‘conditions relating to foul and surface water drainage are necessary, to prevent flooding, and these need to take effect prior to commencement, to ensure an orderly sequence of works…However, a specific condition controlling run-off from the new dwelling’s driveway is unnecessary, as this can be controlled by the condition that I have imposed relating to surface water drainage’. 

21.	During the course of the application additional and revised information and details have been submitted and some of the information initially issued to discharge the relevant planning conditions has been superseded. 

22.	The proposed foul water drainage system details discharge of foul drainage into an existing foul sewer in Fews Lane.

23.	The proposed surface water drainage system details discharge of surface water to an attenuation tank located within the rear garden of the dwelling. The proposed tank is 1.5m x 7.0m x 0.4m and is stated to be capable of storing to up to the 1 in 100 year plus 40% climate change event. A hydrobrake flow control chamber is shown at the outfall to the proposed storage attenuation tank, which discharges to the existing watercourse (ditch) to the north. The flow control is proposed to limit flow to a rate of approximately 1 litre per second.

24.	The submitted information shows the existing watercourse to be at an approximate depth of 1.39m. The width has been measured as approximately 5.3m wide, at the top of the bank, and 2m wide at the base of the watercourse. 

25.	The driveway serving the dwelling is proposed as a gravel driveway, operating as an infiltration feature.  
Background

26.	This application was submitted to and validated by the Council on 16 September 2019. A delegated decision was issued on 28 October 2019 confirming discharge of conditions 4 and 5 attached to S/2937/16/FL (allowed on appeal), subject to installation of the foul water and surface water drainage systems in accordance with the approved details. 

27.	This decision was subject to judicial review from an interested third party who wished to submit comments on the proposed foul and surface water drainage scheme prior to the local planning authority’s determination of the application. A consent order was issued on 12 May 2020 quashing the Council’s delegated decision to discharge conditions 4 and 5 dated 28 October 2019. The application has subsequently been passed back to the local planning authority for re-consideration and to allow for third party comments to be submitted. These third party comments have since been received and are summarised within this report. Officers can confirm that this application has been subject to re-consultation, including further re-consultation following receipt of additional submissions from the applicant. 

28.	This application for discharge of conditions is now brought to the planning committee for their consideration of the officers’ recommendation in respect of the discharge of conditions 4 and 5 attached to planning permission S/2937/16/FL relating to foul and surface water drainage respectively. 

29.	The Greater Cambridge Shared Planning Service has appointed expert advice on drainage matters to allow the local planning authority to fully consider the submission details provided by the applicant, to consider any third party comments and to assess the proposed scheme for foul and surface water drainage at this site having full regard to adopted national and local planning policy, as well as published and acknowledged approaches and best practice. A full copy of the report prepared by the appointed consultant, Stantec, is provided at Appendix A, which also includes details of the qualifications and expertise of the consultant providing the advice to the local planning authority.  
Planning assessment

30.	The National Planning Policy Framework (NPPF) aims to ensure that flood risk is considered at all stages of the planning process to avoid inappropriate development in areas at risk of flooding and to direct development away from areas of highest risk. In exceptional circumstances, where new development is necessary in flood risk areas the policy also aims to ensure it is safe, without increasing flood risk elsewhere, and where possible reducing flood risk overall. For sites less than 1ha in size, such as the application site subject to this discharge of conditions request, and not at risk of flooding, a Flood Risk Assessment is not required, but nevertheless, the principles of ensuring the appropriate and sustainable management of drainage, to mitigate or prevent future flooding, should still form the basis for a sustainable drainage strategy and be used in support for the promotion of sustainable development. The proposed submission details have been assessed taking into account the requirements of the NPPF, in particular paragraph 163.  

31.	Third party representations refer to the Sustainable Drainage Systems Non-Statutory Technical Standards for Sustainable Drainage Systems (March 2015) and state that the discharge of condition request should be refused on the basis of the contents of these Technical Standards. A statement from the Secretary of State for Communities and Local Government dated 18 December 2014 makes clear that these Technical Standards only apply to developments of 10 homes or more or major commercial development. On this basis, these Technical Standards are accordingly not relevant in the assessment of this application. 

32.	The Cambridgeshire Flood and Water SPD provides guidance on the approach taken to the design of new development to manage and mitigate flood risk, including sustainable drainage systems. The SPD promotes the surface water hierarchy as follows:
1.	To ground in an adequate soakaway or some other adequate infiltration system; or where that is not reasonably practical
2.	A watercourse; or where that is not reasonably practical
3.	A surface water sewer; or where that is not reasonably practical
4.	A combined sewer. 

33.	The Flood and Water SPD provides further guidance on drainage strategies, including suitability of infiltration measures on a site, encouraging opportunities to integrate SuDs being maximised and where obstacles to their use persist, requiring this to be fully justified by an applicant. The SPD also advises that where discharge into a third party asset (such as a watercourse or public sewer) is proposed, then appropriate permissions and consents should have been discussed with the asset owner. The SPD additionally outlines the information required to be submitted as part of any surface water drainage strategy, noting that the level of information provided should be proportionate to the size and complexity of the site. Officers are satisfied that the level of information provided as part of this submission is appropriate, proportionate and in accordance with the adopted SPD. 

34.	Policies CC/7, CC/8 and CC/9 of the adopted South Cambridgeshire Local Plan 2018 are pertinent to the assessment of the details submitted. Policy CC/7 Water Quality requires all development proposals to demonstrate that there is adequate water supply, sewerage and land drainage systems to serve the whole development. It also expects that foul drainage to a public sewer should be provided wherever possible. 

35.	Policy CC/8 Sustainable Drainage Systems requires development proposals to incorporate surface water drainage systems (SuDs) appropriate to the nature of the site. Development proposals are required to demonstrate that:
a)	Surface water drainage schemes comply with the Sustainable Drainage Systems: Non-statutory technical standards for sustainable drainage systems and the Cambridgeshire Flood and Water Supplementary Planning Document or successor documents;
b)	Opportunities have been taken to integrate sustainable drainage with the
development, create amenity, enhance biodiversity, and contribute to a network of green (and blue) open space;
c)	Surface water is managed close to its source and on the surface where it practicable to do so;
d)	Maximum use has been made of low land take drainage measures, such as rainwater recycling, green roofs, permeable surfaces and water butts;
e)	Appropriate pollution control measures have been incorporated, including multiple component treatment trains; and
f)	Arrangements have been established for the whole life management and maintenance of surface water drainage systems. 

36.	Policy CC/9 Managing Flood Risk states that in order to minimise flood risk, development will only be permitted where:
a)	The sequential test and exception tests established by the National Planning Policy Framework demonstrate the development is acceptable (where required).
b)	Floor levels are 300mm above the 1 in 100 year flood level plus an allowance for climate change where appropriate and where appropriate and practicable also 300mm above adjacent highway levels.
c)	Suitable flood protection / mitigation measures are incorporated as appropriate to the level and nature of flood risk, which can be satisfactorily implemented to ensure safe occupation, access and egress. Management and maintenance plans will be required, including arrangements for adoption by any public authority or statutory undertaker and any other arrangements to secure the operation of the scheme throughout its lifetime;
d)	There would be no increase to flood risk elsewhere, and opportunities to reduce flood risk elsewhere have been explored and taken (where appropriate), including limiting discharge of surface water (post development volume and peak rate) to natural greenfield rates or lower, and
e)	The destination of the discharge obeys the following priority order:
i. Firstly, to the ground via infiltration;
ii. Then, to a water body;
iii. Then, to a surface water sewer;
iv. Discharge to a foul water or combined sewer is unacceptable.

Policy CC/9 continues further, setting out the requirements for site specific flood risk assessments. 

37.	In January 2020, the Greater Cambridge Sustainable Design and Construction SPD was adopted. This update is an addendum to the wider Cambridgeshire Flood and Water SPD (2016), and specifically incorporates updates following the publication of the adopted Local Plan in 2018. Whilst it is acknowledged that the adoption of the Sustainable Design and Construction SPD was post the approval of the development under application S/2937/16/FL and therefore the imposition of the conditions currently under consideration, it is a material consideration in the assessment of this application and therefore must be afforded some weight in the decision-making process. In addition, policy CC/8, criteria a) makes reference to ‘…the Cambridgeshire Flood and Water Supplementary Planning Document or successor documents.’ Paragraph 3.7.2 of the Sustainable Design and Construction SPD states ‘this section of the SPD focuses on guidance for the implementation of SuDs policy in the Cambridge Local Plan (2018). This guidance supplements the wider guidance on flooding and drainage provided for in the Cambridgeshire Flood and Water SPD. For applications in South Cambridgeshire, further guidance on policy implementation, alongside drainage checklists, is provided in the Cambridgeshire Flood and Water SPD.’ On this basis, Officers are satisfied that no further assessment of the submission details is required against the recently adopted Sustainable Design and Construction SPD in this instance, and that the guidance within the Cambridgeshire Flood and Water SPD remains relevant to the decision-making for this application. 
Condition 4 – Foul Water Drainage 

38.	Condition 4 relates to discharge of the foul water drainage strategy for the approved 1no. dwelling within the application site. The submitted proposals detail discharge of foul water from the dwelling into an existing public sewer within Fews Lane. This arrangement is considered acceptable in principle, in accordance with policy CC/7 of the South Cambridgeshire Local Plan 2018. 

39.	A third-party representation raises concern that there has been no evidence provided to demonstrate that the existing public sewerage system has capacity to accommodation additional flows from the development or that discharge into the public sewerage system has been agreed with the relevant sewerage undertaker. 

40.	As part of the consultation process for this application, a response has been received from Anglian Water, the relevant public sewerage undertaker for this site, who has reviewed the submitted foul water drainage strategy. Anglian Water has confirmed within its written response to the local planning authority that it recommends the discharge of condition 4. 

41.	On the above basis, and in accordance with the recommendation of our appointed drainage consultant, officers consider that the details provided by the applicant seeking discharge of condition 4 of planning permission S/2937/16/FL are in full accordance with both national and local planning policy and guidance, including Policy CC7 of the South Cambridgeshire Local Plan 2018 and the Cambridgeshire Flood and Water SPD. 
Condition 5 – Surface Water Drainage

42.	This application also seeks to discharge condition 5, relating to the proposed surface water drainage strategy for the application site, including surface water arising from both the dwelling itself and the associated driveway area. As set out above, the surface water drainage strategy, in summary, seeks to discharge surface water from the dwelling to an attenuation tank located within the rear garden. Surface water from that attenuation tank is then controlled via a hydrobrake flow control chamber into an outfall that falls into the existing watercourse (ditch) to the north. The attenuation tank has been designed to accommodate a 1 in 100 year plus 40% climate change event, and to discharge at a control rate of 1l/s to the adjacent watercourse. 

43.	The driveway is proposed to be laid to gravel and operate as an infiltration feature. 

44.	Geotechnical investigation and infiltration tests, in accordance with industry standards, have been undertaken by the applicant, the results of which have been submitted and used to inform the proposed design of the drainage strategy for the application site. 

45.	The use of permeable surfacing for the driveway is in full accordance with the SuDs hierarchy set out within both policy CC/8 and the Cambridgeshire Flood and Water SPD, which directs discharge, as a first priority, to the ground via infiltration. Infiltration tests supplied by the applicant demonstrate suitable ground conditions for use of infiltration in this location. 

46.	Surface water run-off from the roof of the dwelling via infiltration, in accordance with the first priority of the SuDs hierarchy set out within Local Plan policy and the Flood and Water SPD, has been discounted by the applicant. Officers and our appointed drainage consultant (Stantec) consider that this has been sufficiently evidenced and justified due to the constricted space within the site for conventional soakaways or an alternative means of infiltration and due to the geological conditions of the site. 

47.	Third party representations have been received, stating that the proposed surface water drainage strategy does not accord within the SuDs hierarchy set out within the Local Plan. 

48.	Officers agree with the third-party objector that the submitted surface water drainage strategy is required to fully accord with the SuDs hierarchy. The SuDs hierarchy sets out a priority order, however it does also allow for discharge not via infiltration, where it can be fully justified as being inappropriate due to site specific reasons or conditions. Accordingly, where fully justified, a surface water strategy that discharges into a water body, such as that proposed, remains in full accordance with adopted national and local planning policy and guidance, being the next suitable option in the SuDs hierarchy priority order. 

49.	Use of a soakaway results in a concentrated point source of water within the ground. It is advised by the appointed drainage consultant that the risk of water affecting the soils under shallow foundations can be quite high if a soakaway is located close to a building. The Building Regulations, part H, advises against soakaways within 5m of building and roads.

50.	In addition, geotechnical information supplied by the applicant evidences clay rich soil of a high plasticity index is present at the site. Again, our appointed drainage consultant has advised that the soil characteristics at this site, are therefore more likely to be at risk of failure through the introduction of soakaways, due to the swelling and shrinkage characteristics of this soil type. Therefore, soakaways or another infiltration feature accepting concentrated run-off, are not recommended within 5m of the building foundations or in proximity to the banks of the existing watercourse. Application of a 5m offset from the building footprint would leave an area of c. 2.5m from the bank of the existing watercourse. Locating soakaways adjacent to a watercourse is also not recommended.

51.	Whilst it is agreed with the third-party comments that the 5m rule is not conclusive, given the site characteristics, geology, and proximity of the watercourse, sufficient evidence and justification exists to discount discharge via solutions which concentrate infiltration at this site. Subsequently, in accordance with the priority order of the SuDs hierarchy, discharge to the local watercourse is the next suitable option to deal with the roof run-off for this site, as proposed. 

52.	Third party representations further state that there are numerous locations for soakaways within the application site greater than 5m from the foundations of the buildings. This has been assessed by the appointed drainage consultant and it is advised that all possible locations within the site have been reviewed and ruled out. Locations outside of the application boundary have not been considered, as this is not deemed to be appropriate. 

53.	The appointed drainage consultants and officers are subsequently satisfied that the priority SuDs hierarchy order of policy CC/9 is fully accorded with, in respect of discharge to the local watercourse for roof run-off for this site. 

54.	Greenfield discharge rates have been provided by the applicant for this site. These being:
0.1l/s for the 1 year
0.2 l/s for Qbar (mean annual flood)
0.4l/s for 30 years
0.6 l/s for 100 years

55.	The proposed discharge rate for the site is 1l/s using a hydrobrake; this being a mechanism used to control the flow of water from the attenuation tank into the outfall and existing watercourse. 

56.	It is acknowledged that the proposed development runoff rate will exceed the existing greenfield runoff rate for this site. The third party has raised an objection to this application on that basis, stating that as ‘the scheme proposes an increase of surface water discharged from the site into Longstanton Brook from the pre-development discharge volume, thereby increasing the flood risk of nearby properties, this is contrary to the stated reason for the condition, which is to prevent flooding’. A similar objection is raised by Longstanton Parish Council. 

57.	The appointed drainage consultant has advised that the development is for a single dwelling, therefore the equivalent greenfield runoff rates for such a scheme will always be minimal. Therefore, to provide attenuation at the greenfield rate, then this would require the use of a water flow control feature of such a small size that it would be at a high risk of blockages, which itself would then be considered a flood risk. This position is supported by the ‘Rainfall Runoff Management for Developments’ national guidance, as advised by our appointed drainage consultant.

58.	In addition, the Cambridgeshire Flood and Water SPD states that hydrobrakes should be used where rates are between 2l/s – 5l/s and that pipes below 2l/s are prone to blockage, but that this can be overcome with product selection and design. The appointed drainage consultant advises that since the publication of the SPD (2016) manufacturers have now developed hydrobrakes that can operate at 1l’s, as proposed, and that this is the minimum viable runoff flow rate for sustainable control without high risk of blockage (which would cause a greater risk of flooding). 

59.	Our appointed drainage consultants’ report, attached, provides further assessment of the 1l/s flow rate and assesses it having regard to the potential flood risk associated with this. This work concludes that, modelled on a worst-case scenario, the discharge rate of 1l/s will amount to 0.05% capacity of the existing watercourse for the proposed site. Therefore, runoff from this development site would amount to a negligible impact on level and flows associated with the existing watercourse. 

60.	In addition, the applicant has submitted calculations for the operation of the proposed attenuation during a 10 year 60-minute winter storm plus 40% climate change, with a fully submerged outfall scenario. The submitted information demonstrates that even in this worst-case scenario, the proposed site will not flood, nor will it cause off-site flooding. 

61.	It is acknowledged that SPD guidance is to ensure that proposed development does not exceed existing greenfield runoff rates, however such a requirement would likely hinder any small-scale development such as this and the implementation of controls to reduce runoff rates to greenfield below the proposed 1l/s is considered a higher potential flood risk, due to the potential for blockages. The approach set out within the proposed surface water drainage strategy is therefore recommended by the appointed drainage consultant, acting on behalf of the local planning authority, and officers agree that it is overall in accordance with the NPPF, Local Plan policies and the Cambridgeshire Flood and water SPD. 

62.	The site is not deemed to be at risk of flooding and is below 1ha in size, therefore the requirements for a Flood Risk Assessment are not relevant for this application. Similarly, the site is not subject to the Sequential tests. This is in full accordance with policies CC/8 and CC/9 of the Local Plan. 

63.	As required by policy CC/9, a below ground operation and maintenance strategy report has been submitted by the applicant, and this will form part of the Health & Safety file for the site. The responsibility for future management and maintenance is secured by this strategy and will be the responsibility of any future owner. These details been reviewed by our appointment drainage consultant and confirmed as being acceptable. 

64.	In summary, given the above details, and in accordance with the recommendation of our appointed drainage consultant, officers consider that the details provided by the applicant seeking discharge of condition 5 of planning permission S/2937/16/FL are overall  in  accordance with both national and local planning policy and guidance, including policies CC/7, CC/8 and CC/9 of the South Cambridgeshire Local Plan 2018 and the Cambridgeshire Flood and Water SPD. 

Other matters

65.	Third party representations have been made on the basis that condition 5 should not be discharged as the position of the final outfall for the proposed surface water drainage system is located outside of the red line boundary of the site and that an application to discharge a planning condition cannot extend the boundaries of land to which planning permission relates. The third party recommends that a planning application is made to extend the red line boundary of the application site to include the land proposed for the surface water outflow into the existing watercourse. 

66.	Officers have considered the red line application boundary against the extent of the development proposed. In officers’ judgment, whilst it is arguably the case that the pipe outlet does not extend beyond the red line boundary, if it does, the development beyond that boundary is considered to be so minor that it is de minimis. The query raised by the third party relates to a relatively small part of a pipe outlet, which is underground, and which will not protrude past the profile of the existing ditch. In any event, given that the watercourse immediately adjoins the northern boundary of the site, the area up to the mid-point of the ditch would be presumed to be within the same land ownership as the application site, and the pipe outlet falls well short of that mid-point.

67.	In summary, discharging condition 5 either, does not require an extension of the red line boundary, or, in the event that it does, any extension of development beyond that boundary is considered to be de minimis. It is officers’ view that, in the circumstances, it would not be necessary, appropriate, or proportionate to require an application to extend the red line boundary in the public interest. As such, officers recommend that the application to discharge conditions 4 and 5 can be determined in accordance with the recommendation provide below. 

Conclusion

68.	The submitted details to discharge condition 4, foul water drainage, and condition 5, surface water drainage, are acceptable and in accordance with national and local planning policy and guidance. 
Recommendation

69.	Officers recommend that the Planning Committee approve this application to discharge conditions 4 and 5 attached to planning permission S/2937/16/FL as follows:

Condition 4 (Foul Water Drainage)
	
The following details are acceptable to the local planning authority and therefore approved:

Site Plan, Drawing Reference FLL-345-Site 01 
Drainage Layout, Drawing Reference 19/0321/100 Rev P9
Below Ground Construction Details, Drawing Reference 19/0321/110 Rev P2

Condition 4 shall be fully discharged once the foul water drainage system has been installed and made operational in accordance with the approved details. 

Condition 5 (Surface Water Drainage)

The following details are acceptable to the local planning authority and therefore approved:

Site Plan, Drawing Reference FLL-345-Site 01 
Drainage Layout, Drawing Reference 19/0321/100 Rev P9
Ditch Plan and Section 1, Drawing Reference 19/0321/101 Rev P3
Below Ground Construction Details, Drawing Reference 19/0321/110 Rev P2
Document titled Below Ground Drainage Operation and Maintenance Strategy Report, prepared by Andrew Firebrace Partnership Limited

Condition 5 shall be fully discharged once the surface water drainage system has been installed and made operational in accordance with the approved details. 

Background Papers

Fews Lane, Longstanton: Drainage Review, Project Ref. 49304, Revision A, dated 20 August 2020. Prepared by Stantec UK Limited. 

Appendices

Appendix A: Fews Lane, Longstanton: Drainage Review, Project Ref. 49304, Rev A

Report Author: 

Emma Ousbey – Principal Planning Officer
Telephone: 07394 572822