Northstowe groundwater investigations

We know that there are concerns about the groundwater levels in the Northstowe area. To help you understand the issue, we've published information on this page to answer ‘frequently asked questions’.

Before reading on, it may be helpful for you to note that, on behalf of Longstanton Parish Council, we commissioned an independent study into Northstowe groundwater levels by an organisation called Hydraulics Research (HR) Wallingford. The study produced 3 reports:

You can also view the contract documents, project brief and proposal [PDF, 7MB].

Following on from these reports, we devised an Action Plan [PDF, 97Kb].

The Council’s role in the investigation

South Cambridgeshire District Council is the local District Council and the Local Planning Authority. However, we are not responsible for enforcing legislation which manage matters to do with groundwater. This remains the responsibility of the Environment Agency.

We have therefore sought their advice and guidance in its investigation of this issue. The Environment Agency have, to date, not acted or advised us of the need to act following their consideration of matters to do with groundwater at Northstowe. We of course continue to be in dialogue with the Environment Agency about this topic.

Finding out where the groundwater gone and why

This is what we are working with partners to investigate.

As part of the planning application for phase one of Northstowe (submitted by developers Gallaghers – now called L&Q Estates) work was undertaken to remove some water from the ground on the phase one site. This type of procedure is common on new developments and is necessary to lay critical infrastructure (such as underground pipes – so the ground must be dry) before any new homes start to be constructed. At that time, the removal of water did not require consent from us or the Environment Agency. The position has subsequently changed, and consent would now be needed from the Environment Agency, to protect groundwater resources.

The submissions to the Council as part of the phase one planning permission did not propose the permanent reduction of groundwater levels on the site. That was not an objective of the development. At the time of the original Northstowe phase one application, local concerns meant that the primary focus of the drainage design team was focused on managing concerns around flood risk. A technical working group of water specialists and engineers was convened and considered ways in which flooding could be avoided. This was particularly important following flooding events in 2001 in Longstanton. The exploration of drainage options therefore focused in the main on this objective, noting the Environment Agency responses to the Northstowe phase one planning application at that time focused less on the management of groundwater resources.

We are the Local Planning Authority and determine planning applications, but on technical design matters which relate to planning applications, relies upon the advice and guidance of statutory bodies. This includes the Environment Agency and Lead Local Flood Agency. It also relies upon the advice and guidance of non-statutory specialists, such as internal drainage team officers. This expert advice and guidance is relied upon to assess the technical design solutions for development proposals across South Cambridgeshire - including at Northstowe.

As indicated above, given the emphasis of local partners and the community on mitigating flood risks, there appears to have been less of a focus by the Environment Agency and the other members of the technical advisory group on the scoping of groundwater issues into the Environmental Assessment of the Phase One planning application. This focus is carried through and reflected in the technical consultees’ advice in respect to approval of the drainage scheme details.

We have subsequently sought additional information from L&Q Estates about the completed surface water drainage system at Northstowe. The mapping information received suggests that the completed system does not interfere with groundwater levels.

We have compared the approved and completed details to determine whether the proposals are in breach of the drainage details approved for the site. To date, they have not found a significant departure from the scheme that was approved. More recent efforts have therefore centred upon exploring whether unintended movement of groundwater is taking place through the surface water drains.

Planning process and environmental protection to the area

The planning process for phases one, two and three of Northstowe has sought to identify and then assess the environmental effects of the development. In the early phases of the site’s consideration and development, the focus was on ensuring that surface water flooding risks were managed effectively. Consideration of groundwater by the technical drainage consultants involved in the development, assessment and approval of the initial drainage scheme focused in the main on flood mitigation and protection. In subsequent phases, and particularly as the groundwater changes around the site have arisen, groundwater impacts have been considered more fully, alongside the matters of flood risks and foul water management.

The Environmental Impact Assessments prepared for each phase of the development were scoped out with the input from the statutory agencies involved – including the Environment Agency – who are primarily responsible for managing groundwater. They were also consulted on the planning applications and their views were considered, alongside others such as the Lead Local Flood Authority, as part of the decision-making process. The purpose of the Environmental Impact Assessment Regulations is to capture the potential effects of a development upon the environment. As knowledge and understanding of the issues around groundwater have increased over the life of the development at Northstowe, the consideration of the effects of development upon groundwater has also increased. For example, there was extensive consideration given to the matter in the January 2022 and March 2022 Planning Committee meetings for the 2 parts of phase 3 of Northstowe.

Water levels reduced at Kingfisher Pond

On behalf of Longstanton Parish Council, we commissioned HR Wallingford to investigate the reasons for the Kingfisher Pond water levels being reduced. You can read their report here [PDF, 7MB]. Whilst they associate the construction of Northstowe with the reduced water levels in that pond and suggested that the pond and the groundwater were in hydraulic continuity, they did not make any further connection to specific infrastructure. We have sought clarification from developers L&Q Estates about the relationship of the drainage scheme with the groundwater. L&Q Estates have suggested that the development is not responsible for this change. There are ongoing investigations of potential routes for movement of groundwater from near to the Kingfisher Pond but there is no firm conclusion on this matter currently. We are continuing to work with the developer on this matter and is seeking further comment from L&Q Estates in response to recent comments.

Furthermore, the HR Wallingford report says that dry periods will have had an impact on groundwater levels. The report’s commentary on periods of below average rainfall and groundwater levels indicates some significance to climate conditions in local water levels but suggests it is not the primary cause for the decline. HR Wallingford also observe however that the below average level of regional rainfall has made it more difficult to understand the impacts on groundwater levels but recognise that it is nevertheless a contributory factor to the low levels observed.

Helping Kingfisher Pond to recover

The HR Wallingford report recommendations are split into 2 specific areas. Firstly, the following recommendations apply if the Kingfisher Pond recovers:

regular monitoring of the surface water levels in the pond and other ponds in the area
regular monitoring of the groundwater elevation
regular monitoring of groundwater levels adjacent to and flows in the greenways to ensure that they have bene constructed in accordance with the design principles and that they are not contributing to dewatering.

The following recommendations apply if the Kingfisher Pond does not fully recover:

supporting levels in the Kingfisher Pond
deepening the Pond
improving the greenways to ensure that they are in accordance with the design principles.

We are continuing to investigate whether the observed changes in levels in the Kingfisher Pond are likely to recover. Once we have been able to draw that conclusion, we will then consider further the HR Wallingford recommendations – and the actions arising. Variations in climatic conditions have made drawing such a conclusion more difficult.

Recovering groundwater levels in and around Northstowe

We have met with the developers, Parish Councils and with the Environment Agency to try and better understand how the matter might be investigated further. We have been, and continue to, explore how the matter can be resolved. In particular, we have sought information from L&Q Estates concerning the completion of the drainage scheme and continues to explore with Northstowe Town Council, their hypothesis concerning abnormal surface water drainage on phase one. With all of this in mind, we are attempting to determine whether any further form of investigation might lead to a definitive conclusion on this issue.

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