These are the responses we received to the questions we put to SCDC. The response included answers from L&Q (the developer), Homes England (HE) and Greater Cambridge Shared Planning (GCSP). The answers received are reproduced verbatim below.
1. Is it correct that the primary mechanism for limiting the level of the water table in Northstowe is the swales and that this process is ongoing and intentional?
L&Q: This assumption is incorrect. The Swales collect development surface water run -off and drain this into the local watercourses via the Waterpark attenuation balancing lake.
HE: The Swales are designed as Sustainable Drainage systems to manage any increase in surface water runoff (ie rainfall that falls on impermeable areas created as part of the development proposals) in a sustainable way, to limit this to predevelopment runoff rates. This is in line with Best Practice and as approved through the planning process.
GCSP: The LPA has nothing to add to L&Q Estates’ and HE comments. There is no evidence to suggest this was the purpose of the swales.
2. What calculations were made as to the upper acceptable level of the water table (to obviate the risk of flooding) and how were these calculations implemented in the design and execution of the swales?
L&Q: The Swales are in no way associated with and do not govern the level of the water table and therefore no such calculations were required or produced.
HE: Ground Water has been monitored for some years and levels were set out within the Phase 3A Flood Risk Assessment, along with an assessment of how levels might change as a result of development of the site in line with the approved planning consent. As can be seen within the FRAFlood Risk Assessment Ground Water levels may be affected locally, within Phase 3A itself, as result of development (ie incorporation of hard surfaces and the management of surface water runoff from these areas through positive sustainable drainage measures). However due to the topography of the surrounding area this is not anticipated to affect groundwater levels outside of the Phase 3A site area. Groundwater monitoring will be continued (as required by the Phase 3A Outline Planning consent), and recharge of ground water through appropriately designed SuDS systemsSUDS are drainage systems that are considered to be environmentally beneficial, causing minimal or no long-term detrimental damage will be considered where appropriate as part of the Detailed Design process.
GCSP: Nothing to add to L&Q Estates’ and HE comments.
3. We understand that the east end of the northern swale end is at a height of 7m AOD whereas all the Longstanton ponds, including the Kingfisher Pond, are at 10m AOD. Is this a straightforward explanation for Longstanton’s total loss of groundwater?
L&Q: The two features are mutually exclusive. The eastern end of the Swale is situated above the Ampthill Clay Layers. The Kingfisher Pond and the Swales are not connected in any way. The Swales are constructed as part of the approved SUDS strategy.
HE: Wallingford undertook an independent review of the changes in groundwater around Phase 1 (L&Q) over the years and concluded that in part this was due to natural climatic changes and rainfall being below average over a number of years, in part due to drawdown as part of the development of phase 1. Homes England are undertaking baseline monitoring of groundwater to use this data to understand any changes throughout the development, something that was not in place for the previous L&Q development. This has been agreed through the planning process, as set out within the Groundwater Note previously circulated, and will be manged through formal permitting and approval processes legally required by both the Environment Agency and the Lead Local Flood Authority.
GCSP: Nothing to add to L&Q Estates’ and HE comments.
4. Are the swales currently draining only to the level necessary to avoid flooding in Northstowe, or are they currently constructed in such a way that they drain more water than necessary?
L&Q: They collect development run off as approved in the relevant planning permissions.
HE: The Sustainable Drainage systems have been designed to manage surface water runoff for the development proposals, in line with current best practice. These are surface level features were feasible, and the depths have been minimised to limit interaction with groundwater. The water parks are clay lined to ensure there is no accumulation of surface run off water and ground water in Phase 2.
GCSP: In the Council’s view, the swales are constructed in accordance with the planning permission. Their purpose was to do no more than collect development runoff in line with the approved drainage scheme. Whether the swales perform any other function – for example in respect of groundwater is not likely to be easy/possible to determine (based upon the advice from the EAEnvironmental Assessment that the LPALocal Planning Authority received during the course of its earlier discussions with them on this matter.
5. Why were we repeatedly told during the initial dewatering process that the effects would be only temporary and that the ponds would recover when it must have been clear to the developers that allowing the water table to return to its previous level would result in seasonal flooding in the lower-lying areas of the site?
L&Q: De-watering was undertaken to temporarily restrict water ingress to a limited number of drainage excavations. This was not done to permanently lower water table levels.
HE: This comment relates to Phase 1 L&Q development which is an area outside of Homes England Control. The outcome of the independent Wallingford reports was that groundwater levels within Longstanton and near to Kingfisher pond were close to levels seen prior to 2015.
GCSP: Nothing to add to L&Q Estates’ and HE comments. Dewatering was not an activity regulated by the planning permission, or within the Control of the Council.
6. With whom did the misinformation originate and which public bodies and agencies were privy to it?
L&Q: We are not aware of providing any misinformation.
HE: Homes England is unaware of misinformation and hasn’t been involved in these discussions.
GCSP: All of the material associated with the approved drainage scheme design is online. The LPA has no further comment on this matter.
7. What can be done to remedy the damage done to Longstanton’s ponds, restore water supply to e.g. Larksfield nursery and provide restitution in case of future damage to Longstanton’s buildings and infrastructure? Bearing in mind the answer to the previous question, who is responsible for this and who foots the bill?
L&Q: We reiterate our position that the Northstowe Phase 1 development has not contributed to the issues referenced above. It is our understanding that the East of England continues to experience issues related to drought and water resource availability. Ongoing below average annual rainfall is a regular issue being widely reported on throughout the region.
HE: As above Groundwater levels naturally fluctuate , and the outcome of the independent Wallingford reports was that groundwater levels within Longstanton and near to Kingfisher pond were close to levels seen prior to 2015. Homes England’s involvement on Northstowe started post 2015.
GCSP: GCSP/SCDC role in this matter is as the District Council planning Authority. No breach of planning permission has been identified and on that basis, there is no statutory role for the LPA/District Council. With regard to any impact arising from lawfully implemented development on specific third party interests, this is a private matter between the developer and the impacted party. The Environment Agency have responsibility for the protection of groundwater resources generally. We understand that they have declined to investigate or intervene in this matter.
8. Without reopening the discussion about the absence of an EIA for Phase 3A, which is expected to drop the water table by a further 2-3 metres, would it not be profoundly reckless to proceed with this phase until the problems with Phase 1 have been identified and remediated?
L&Q: See above responses in relation to Phase 1. We refer any further questions in relation to Phase 3A to the relevant authorities.
HE: As noted above phase 1 was a development undertaken by L&Q, not Homes England.
As set out within the Phase 3A FRAFlood Risk Assessment, and approved through the planning process, and with the Lead Local Flood Authority, Ground water levels are not anticipated to be altered outside of the Phase 3A site area, and groundwater monitoring is ongoing.
An EIA Scoping was undertaken as part of the Phase 3A outline planning application which establishes content of an Environmental Statement and FRA, which was consulted with relevant bodies. Issues have been explored through the planning process.
GCSP: An EIA was completed for the Phase 3A development, as documented in the Environmental Statement submitted with the application (Ref: 20/02171/OUT). A technical paper drawing upon the EIA was provided to the LPA indicating that the effect of ground works and the development on the water table was very localised. Conditions requiring monitoring of the effect of the development upon groundwater form part of the planning permission.
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