4.3 Water

It is important that development at North East Cambridge responds to the climate emergency and local water resource issues through minimising water use as far as possible, ensuring that water and sewage infrastructure is adequate and maintains water quality in the area, and minimises flood risk now and in the future. The policies in this section set clear standards and expectations for development across all water related issues.

Water efficiency

  • You recognised that the scope to maximise the potential for water recycling, stormwater and rainwater harvesting measures as part of the design needs to be explored, although acknowledging that brown water recycling should be undertaken in an effective and sustainable manner. A site wide approach to water supply should be explored early on. The highest levels of water recycling in compliance with maximum BREEAM credits for water efficiency should be sought including an understanding of maintenance and carbon efficiency.
  • You raised the need for planning to take full consideration of climate change and water stress, with some respondents noting issues surrounding water abstraction and the impacts that this is having on the River Cam and other local watercourses.
  • The Environment Agency supported early consideration of integrated approaches to water management that considers not just flood risk but also water resource availability.
  • Cambridge Water were supportive of setting the highest possible standards for water efficiency with reference to 80 litres/person/day for residential development.

How your comments and options have been taken into account

  • In terms of water efficiency, due to the levels of water stress facing Cambridge, the policy requires the use of the national technical standard of 110 litres/person/day for all new residential development, and the specification of a set number of BREEAM credits for non-residential development (of between 3 and 5 credits under Wat 01). However, it is noted that these targets alone may not be sufficient to secure long term sustainability of water supply, and it is noted that in their response to the 2019 Issues and Options consultation, Cambridge Water reiterated their support for the setting of an 80 litre/person/day standard for all residential development at the site.
  • While national planning policy currently prevents the Councils from setting more ambitious targets for water efficiency in residential development, it is considered that the area could, due to a number of factors, represent an opportunity for an area-wide approach to water reuse as part of an integrated approach to water management. As such, policy in the Area Action Plan could promote this approach. We have not placed an obligation or provided a policy criterion for decentralised water supply as we do not have an evidence base to demonstrate this could work at an Area Action Plan scale. We would need assurances that the critical scale for a decentralized network to operate effectively would not undermine the strategic water supply function for the site.
  • The policies reflect the concerns made in relation to demand and water stress including climate change impact within the criteria and also stipulates the integration requirements between water management and green infrastructure.

Water quality and demand

  • You suggested that a full investigation is required to ensure any remedial work on water contamination is fully explored and considered and that this would be required as part of a planning condition.
  • Further commentary was received relating to integrating water management with sustainable urban drainage systems (SuDS), water use/recycling and green infrastructure for North East Cambridge with an innovative management strategy.

How your comments and options have been taken into account

  • In terms of site water contamination remediation, the policy places clear emphasis on the contamination impact associated with the First Public Drain. The policy states that an obligation will need to be secured by the developer to carry out a water quality assessment and propose a mitigation management and maintenance plan.

Flood risk and sustainable urban drainage

  • You raised concerns about the relocation of the Cambridge Waste Water Treatment Plant and its impact on flood risk, neighbouring communities, green belt and the environment. You also felt that the suitability of relocation options for the Waste Water Treatment Plant should be picked up in a Water Cycle Study.
  • You commented that opportunities should be made for provision of on-site water management integration with SuDS, green infrastructure and water use/re-use including management innovation and to ensure that this interaction is an integral element of any initial design stage.

How your comments and options have been taken into account

  • The policy and subsequent Sustainability Appraisal and Water Cycle Study will address the impacts of the relocation of the Waste Water Treatment Plant on development at North East Cambridge. However, it is not for either the policy or accompanying Sustainability Appraisal to assess the relocation: this will be subject to its own assessment as part of the consent process for the new facility. Sustainable urban drainage systems (SuDS) will be an integral part of North East Cambridge and there are measures in the policy to ensure SuDS are multi-functional and incorporated with green infrastructure and water management.
  • The policy stipulates that developers will need to put in place measures that will ensure high standards for drainage, water reuse, management and flood risk are secured and that an area-wide approach is taken, including in relation to management and maintenance.

Policy 4a: Water efficiency

All new residential developments must achieve, as a minimum, water efficiency equivalent to 110 litres/person/day. Substantial weight will be afforded to mains water consumption of 80 litres/person/day, giving consideration to rainwater harvesting and/or water recycling. Proposals for non-residential development must achieve 5 BREEAM credits for water use (Wat 01), unless it can be demonstrated that such provision is not technically or economically viable.

Policy 4b: Water quality and ensuring supply

A Water Quality Risk Assessment will be required and secured through a planning obligation to identify foul sewage, surface water and groundwater on surface and groundwater systems and consider appropriate avoidance measures before incorporating appropriate mitigation measures including works to the First Public Drain where necessary.

The Councils will expect developers to demonstrate that all proposed development will be served by an adequate supply of water, appropriate sewerage infrastructure and that there is sufficient sewage treatment capacity to ensure that there is no deterioration of water quality.

Prior to commencement of development the potential for contaminated land (both human health and controlled waters) shall be comprehensively characterised, investigated and risk assessed including the consideration of remediation as necessary having regard to the proposed end uses.

Policy 4c: Flood Risk and Sustainable Drainage

All development proposals will be permitted providing it is demonstrated that:

  1. the peak rate of run-off over the lifetime of the development achieves greenfield run-off rates. If this cannot be technically achieved, then the limiting discharge should be 2 litres per second per hectare for all events up to the 100-year return period event;
  2. the development is designed so that the flooding of property in and adjacent to the development would not occur for a 1 in 100-year event, plus an allowance for climate change and in the event of local drainage system failure;
  3. the discharge locations have the capacity to receive all foul and surface water flows from the development, including discharge by infiltration, into water bodies and sewers;
  4. there is a management and maintenance plan for the lifetime of the development, which shall include the arrangements for adoption by any public authority or statutory undertaker and any other arrangements to secure the operation of the scheme throughout its lifetime; and
  5. where reasonably practical, the destination of the discharge complies with the following priority order:
    1. Water reuse and brown water harvesting;
    2. To ground via infiltration (where reasonable and practical);
    3. To a water body; and lastly
    4. To a surface water sewer
  6. Discharge to a foul water or combined sewer will be unacceptable.

    Development proposals will be required to carry out a Strategic Flood Risk Assessment following the principles of the National Planning Policy Framework (2019).

    In addition, proposals will be supported for an undeveloped site:

  7. if it is not located within the Environment Agency's flood zone 3b, unless it is a water-compatible development and does not increase flood risk elsewhere by either displacement of flood water or interruption of flood flow routes and employs flood resilient and resistant construction, including appropriate boundary treatment and has a safe means of evacuation; and
  8. if it is not located within the Environment Agency's flood zone 3a, unless it is a water compatible development or minor development when the principles in a) and b) above apply; and
    1. it is located within the Environment Agency's flood zone 2 or a surface water wetspot and employs flood resilient and resistant construction as appropriate; and
    2. floor levels are 300mm above the 1-in-100-years flood level, plus an allowance for climate change where appropriate and/or 300mm above adjacent highway levels where appropriate.
  9. To minimise the risk of flooding in North East Cambridge all development will be required to implement a Sustainable Drainage System (SuDS) in accordance with the Cambridgeshire Flood and Water SPD. Development will be permitted provided that:

  10. surface water is managed close to its source and on the surface where reasonably practicable to do so;
  11. priority is given to the use of environmental improvements, with SuDS naturalised to enhance green and blue infrastructure;
  12. water is seen as a resource and is re-used where practicable, offsetting potable water demand, and that a water sensitive approach including impacts of climate change are considered in the design of the development;
  13. the features that manage surface water are commensurate with the design of the development in terms of size, form and materials and make an active contribution to placemaking;
  14. Surface water management features are multi-functional where possible;
  15. Any flat roof provides an element of green or brown roof;
  16. There is no discharge from the developed site for rainfall depths up to 5 mm of any rainfall event.

Adopted SuDS schemes will be discounted from formal open space calculations.

Relevant Objectives: 1, 4

Water efficiency

North East Cambridge is located in an area of severe water stress. The area has experienced lower than average rainfall over several years, leading to local concerns regarding impact on watercourses, in particular chalk streams. The policy sets out a number of measures to ensure that high levels of water efficiency are achieved in new developments in order to respond to the water stress facing Greater Cambridge.

Development at North East Cambridge is being considered as part of the wider Water Cycle Study undertaken for the emerging Greater Cambridge Local Plan. This study considers the River Cam catchment, within which North East Cambridge falls, as well as any supply/capacity constraints that are evident.

For new housing, national policy enables local planning authorities to set water efficiency standards for new development in line with the additional national technical requirements set out in Part G of Building Regulations, for areas where there is clear need. The need for setting the requirement of 110 litres/person/day has already been established through the examination of the adopted 2018 Local Plans. For non-residential development, it is recommended that policy for North East Cambridge follows that for the rest of Cambridge, where maximum BREEAM credits for water use is sought.

However, it is noted that these targets alone may not be enough to secure long term sustainability of water supply. At present, national policy limits the level of water efficiency that we can set for new housing, despite there being clear evidence that more stringent standards are required. The scale of development at North East Cambridge, along with the mix of uses, means that the site represents a significant opportunity for a site wide approach to water reuse as part of an integrated approach to water management, and as such the policy in the Area Action Plan promotes this approach. Such an approach, combined with water efficiency measures, could support the achievement of more ambitious levels of water efficiency for the scheme, taking inspiration from other developments in the Greater Cambridge area that benefit from water re-use such as the Eddington development at North West Cambridge.

Water quality

The maintenance and enhancement of water quality of both water courses and groundwater within North East Cambridge is imperative. Not only can these be an important source for water supply, but they can also provide a valuable general amenity, biodiversity and recreational resource. The majority of North East Cambridge falls within a medium category for groundwater vulnerability. This means that the area offers some groundwater protection.

The Environment Agency publication 'Policy and Practice for the Protection of Groundwater' provides useful information and guidance on the risks to groundwater quality. It also explains the concepts of source and resource protection.

Any site which may be contaminated to some degree by virtue of its previous usage forms a potential risk to water quality, especially if redevelopment takes place. The Environment Agency requests that any developers of sites which fall into this category contact the Environment Agency at their earliest opportunity to discuss the need for historical information and site investigations to determine the degree of contamination, if any, of both soil and groundwater.

Although the River Cam is not within the Area Action Plan boundary the river catchment does cover the Area Action Plan. There is over-abstraction from the aquifer within the catchment of the River Cam. Water is abstracted primarily to supply homes and businesses but also as part of an 'augmentation scheme' in which Cambridge Water abstracts from the aquifer, to pump into the rivers to ensure they 'run'. There is also seasonal abstraction for agricultural purposes. Much of the water extraction takes place up stream of the River Cam from the Area Action Plan area, in particular from the chalk streams which feed the river, and which have an impact on flow.

The River Cam is experiencing a very low flow rate, where the majority of the water volume is outflow from the Waste Water Treatment Plant. Water pollution from both point of source and diffused pollution continue at the same rate, but if the river volume is low and moving slowly, the impact in terms of nitrification, algal bloom, deoxygenation and siltation is greater. The previous and current uses of the site indicate that ground contamination is likely to be an issue. Although this is not a flood risk issue, it will have an impact on the type of surface water management regime that should be utilised by any development proposal.

Adequate site investigations will need to be undertaken to determine the level of contamination, locations and level of risk. This will define appropriate surface water management solutions. Sustainable drainage systems (SuDS) can be used effectively in areas of contaminated land as they are not limited to infiltration devices. Features such as ponds, swales and rain gardens can be lined to prevent the mobilisation of contaminants and purification can be attained through reed planting and other water-based planting.

Flood risk

The general principle of assessing all forms of flood risk at every stage of development is a principle that is established within the National Planning Policy Framework and the National Planning Practice Guidance. Local authorities are encouraged to have a proactive approach in managing flood risk.

Flood risk is generally assessed on the basis of the potential source of flooding, with fluvial (river), pluvial (surface water), groundwater, sewers and reservoirs being the main potential sources and the North East Cambridge Area Flood Risk Assessment 2019 has been used to determine this. Development may increase the flood risk downstream unless an adequately designed surface water management scheme is incorporated into the proposals.

The majority of existing office and industrial developments do not meet current drainage standards, which have been significantly improved since these buildings were developed, and are discharging greater flows than would have been, prior to the site being developed. These existing developments may represent a risk during extreme events and may cause localised flooding. They will also contribute to a greater catchment wide discharge than prior to development. Any redevelopment proposals should be designed in accordance with Policy 4C and SuDS best practice in order to minimise surface water runoff rates.

SuDS have long been promoted by local authorities as a sustainable way of reducing run-off to greenfield rates, where workable. The Councils' preferred approach is to manage run-off through surface water attenuation, such as open swales which give an opportunity for flood attenuation by storing and slowly conveying runoff flow to downstream discharge points or infiltrating it into the ground, depending on soil and groundwater conditions. Land used for SuDS will be discounted from formal open space calculations to ensure the functionally of the SuDS system does not reduce the amount of useable formal open space provided on-site.

  • An increase in the number of non-residential completions delivered with maximum BREEAM credits for water consumption;
  • All new residential completions will be designed to achieve water consumption levels of no more than 110 litres/person/day transitioning towards 80 litres/person/day

Cambridge Local Plan 2018

  • Policy 28: Carbon reduction, community energy networks, sustainable design and construction and water use
  • Policy 31: Integrated water management and the water cycle

South Cambridgeshire Local Plan 2018

  • Policy CC/4: Water efficiency
  • Policy CC/7: Water Quality
  • Policy CC/8: Sustainable Drainage Systems
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