SCDC correspondence with Hilary Stroude

5th October 2022

On 27th August we published the text of a number of questions sent to SCDC leader Bridget Smith by Hilary Stroude. These question were themselves a follow-up to earlier questions Hilary put to the council at a council meeting in late July.

After a lengthy delay, responses to the follow-up questions have been received from Stephen Kelly, SCDC’s Joint Director of Planning. Below, we share those answers, together with Hilary Stroude’s response. It seems that questions continue to beget more questions.

Get comfortable – it’s a long read! As usual, your comments are invited.

Responses to Hilary’s follow-up questions

Dear Hilary

Further to your email addressed to the Leader of the Council in response to the earlier reply to your questions, Cllr Smith has asked that as the Joint Director of Planning, I respond to your additional questions. Thank you for your patience. As I indicated in my earlier response to your email, I have received a response to your comments from Homes England and I reproduce their additional comments at the end of this letter for completeness. I deal with each of your questions in turn below.

Q1
How is it possible to know whether the groundworks have deviated in any way from the original planning application when most of the drainage infrastructure has been buried under houses and roadways? It is for this reason that it was vital that SCDC inspected the site in 2016, when groundwater issues across Longstanton were first reported. What investigations have the officers carried out which allows them to be certain that there has not been significant departure from the plans?

Answer: Officers have sought to compare the as built plans with the approved plans for phase 1 where it is possible to do so. You are right that buried drainage underneath the recent development is not able to be surveyed in detail by the Council. These subterranean drains are nevertheless planned as a closed part of the system – with pipework and formal connections. In terms of the main swales – which convey the water from the drains through the site, officers have sought to compare the levels of the swales based upon a site visit, with the approved plans, and the details provided by L&Q Estates to determine whether the proposals depart materially from those approved plans. To date, officers’ view is that there is no significant departure from the approved plans.

Q2
Why has an independent survey of the swales not been commissioned? The on-going survey worked organised by LPA is welcome but Longstanton residents would like to know who is carrying out this survey work – is it independent of the developer?

Answer: Given conclusions in respect of Q1, the Council has not determined that an independent survey is required. The survey of a particular spur of the surface water drainage system on plot H9 is being undertaken by the developer of that specific site, with details passed to the Local Planning Authority. The survey itself was undertaken by a contractor appointed by the developer – with the details provided to date indicating that some minor remedial works are required – but pointing to no evidence of a significant flow of water into the drainage spur.

Q3.
This is a main issue – I asked what mechanism the planning permission for filling the lakes was. As Leader of SCDC you should know this, it doesn’t need to rely on someone else making comments. We also wish to add an additional question here: “What mechanism is currently in place for filling the lakes”. These questions are simple and the answers should be known by SCDC – they will certainly be known by both L&Q Estates and Homes England. We would like answers to these questions as soon as possible.

Answer: The Council has shared your question with Homes England’s officers and L&Q Estates’ representatives, and Homes England have provided the comment below. The lakes form part of the formal drainage system and, unlike the Kingfisher pond, are designed to not be in hydraulic continuity with groundwater – they are clay lined. As a result, the lakes are designed to be filled from the surface water drainage network discharging into the lakes.

Q4
Why was no mitigation put in place immediately to safeguard Longstanton water features from the reported negative impacts of the Northstowe development?

Answer: To date the Council has not been able to identify a breach of the planning permission in respect of phase 1 that would enable it to take action under the Planning Acts. The LPA is not the body responsible for safeguarding groundwater, that statutory enforcement responsibility rests with the Environment Agency and not South Cambridgeshire District Council.

Q6
Longstanton residents want to know how was the Phase 2 lake refilled as we do not believe that it can be from rainfall alone? If it does rely on rainfall alone then it will not be possible to ensure that the lake remains full of water in the summer. If you look at all attenuation ponds you will see that they lose considerable quantities of water through evaporation. If the stored surface water (meant to be kept at a minimum of 2 metres) evaporates during hot weather how is it being recharged if there is no rain? If the Phase 2 lake is in hydraulic connectivity with the RTD deposits so this minimum water level can be maintained – we would like to know.

Answer: The lake is designed to attenuate surface water runoff and is filled through the surface water drainage system, deliberately retaining a residual level of water in it. Further detail is provided in Homes England’s response, appended to this letter.

Q7
Surely, it would have been expedient to have ensured that a new Environmental Impact Assessment was required for Phase 3 so that drainage of the site could have been designed to help rectify some of the damage that we are seeing?

Answer: The Phase 3 planning applications were considered against a comprehensive Environmental Assessment which incorporated details of the development’s relationship with and impact upon groundwater, noting the specific pathways for groundwater flows – which avoid phase 1. The specific characteristics of the land under phase 3a and 3b were considered, having regard to opportunities to recharge groundwater where required as a result of the monitoring of groundwater required by the associated planning conditions.

Q10
You state that ‘the Council does not consider the impact of reduced RTD water levels to be insignificant – and is focused on investigating the causes for it’ why then was planning permission for Phase 3A given when the planning document (NORTHSTOWE Phase 3A Outline Planning Application ES Volume 1 – Main Report April 2020 Chapter 10: Ground Conditions, Contamination and Hydrogeology) contains table 10.11 and 10.12 which clearly states the developments effect on existing buildings, surface water and hydrology will be “Not significant”. The mitigation section of this document also includes nothing about water levels or availability; it only mentions mitigation of pollution and contamination.

Answer: Noting your comments, the Council considers that the material submitted with the application and the environmental and planning assessments for the planning applications covering Northstowe phase 3 addresses all relevant matters appropriately.

Q12
And finally, consideration of H R Wallingford report and any recommendations as to whether the Kingfisher pond may require alternative engineering is simply not enough. Many of us who have been involved with the Longstanton groundwater issue did not agree with the narrow remit under which H R Wallingford was asked to work. However, H R Wallingford proved hydraulic connectivity across the RTD gravels and as a result Longstanton wishes to see the groundwater features across Longstanton given equal priority to the Kingfisher pond and mitigation measures put in place for all the private wells and ponds across this village. It is simply not acceptable for local residents to suffer damage to property and losses as a result of failures in the Northstowe planning process. Damage across Longstanton village needs to be repaired and residents compensated for any loss.

Answer: The scope of the H R Wallingford report was agreed by the Parish Council. The process for enforcing and safeguarding groundwater interests under the Water Act rests not with South Cambridgeshire District Council but with the Environment Agency.

You have invited the Leader, Cllr Handley and Cllr Hawkins to visit the site with local residents to see the circumstances in Northstowe for themselves. Cllr Hawkins has already agreed to meet with local residents and the recently formed group focusing on this matter. Due to key staff absence through the holiday period, we were unfortunately not able to accommodate that meeting earlier. With the recently announced by-election taking place, we are now targeting a date in November, following the Local Election, for such a meeting.

I hope that my response is helpful. In addition to my comments above, I have reproduced below the response from Homes England to your submission. As I have indicated, we will be arranging an appropriate meeting to allow further discussion on the matter following the local election in November and I will ensure that you are invited to this.

Yours sincerely
Stephen Kelly
Joint Director of Planning

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Appendix: Homes England response to Questions 3, 6, 7 and 10

Response to Q3
In relation to Phase 2, outline planning permission for the waterpark lakes was granted under reference S/2011/14/OL. Earthworks and strategic engineering reserved matters approvals (S/1002/18/RM and S/4208/18/RM) cover the details and the report submitted in relation to condition 18 of the outline planning permission (Site Wide Surface Water Drainage Strategy – approved under S/0871/18/DC) is relevant. The approved drainage strategy is also described in the above mentioned FAQ sheet. The lakes are designed to attenuate surface water run-off. As such, surface water runoff from a large catchment area (including various development parcels, the future sports hub and nearby hardstanding areas) has been running off into the waterpark for a number of years to start filling the lakes up and there is currently no pumped outfall from these lakes. The lakes sit in clay or have been lined and have been designed to retain water at a permanent minimum level. Water cannot currently escape other than by evaporation. This is allowing the lakes to fill up to the permanent water level agreed through planning. This is explained in more detail below.

Response to Q6
There is no evidence that the phase 2 lakes are in hydraulic connectivity with the RTD deposits. They have specifically been designed not to be.

I understand that SISK were managing water levels within and between the phase 2 lakes to enable works to be complete, but that this work is effectively complete now and did not involve water being pumped into the lakes from outside of the site.

Response to Q7

• Homes England is responsible for Phases 2, 3A and 3B, which have all been subject to an extensive Environmental Impact Assessment and Flood Risk Assessment.
• It can be confirmed that the Northstowe Phase 2 waterpark is constructed within Kimmeridge clay, or have been designed to be lined with clay to prevent ingress of ground water.
• Other water features around Longstanton are directly linked to groundwater and therefore are full when groundwater levels are high, and empty when groundwater levels are lower.
• This is not the case with the phase 2 waterpark. The lakes in the new water park have been designed to have a 2m permanent water depth and surface water attenuation will be provided on top of this to deal with the 1 in 200 year rainfall event (including an allowance for climate change) – which exceeds planning policy requirements. See indicative cross section below.
• Whilst the phase 2 waterpark lakes may appear ‘full’, this is because surface water runoff from a large catchment area (including various development parcels, the future sports hub and nearby hardstanding areas) has been running off into the waterpark for a number of years to start filling these up and there is currently no pumped outfall from these lakes, so water cannot escape into the ground. This is allowing the lakes to fill up to the permanent water level agreed through planning as shown below.
• There is no evidence that the permanent water contained within the phase 2 waterparks is related to local features in Longstanton drying out following a long dry summer where groundwater levels will no doubt be low.
• In simple terms, the lining of the phase 2 lakes has been designed to prevent both water escaping (below the outfall level) other than by evaporation and also water coming into the lake via the ground. The lakes cannot be compared with other ponds in the area because they are different in this respect.

Response to Q10
Homes England is responsible for Phases 2, 3A and 3B, which have all been subject to an extensive Environmental Impact Assessment and Flood Risk Assessment.
Northstowe phase 3 will include Sustainable Urban Drainage systems, including swales alongside roads and through greenways, and basins. These carry surface water from the centre of the site (which is the high point) towards the north east to large lakes in our new water park. A small section of the site falls to the south, and the basin proposed in this area (part of future Phase 3A). The system has been designed to be sealed to prevent interaction with groundwater.
The Flood Risk Assessment sets out how this impacts the surrounding areas (outside of the site) in a number of ways:
Minimising hardstanding onsite – over 55% of the Phase 3 site will remain green and will allow natural infiltration to continue in these areas as existing
During detailed design if some SUDS features can be designed to recharge groundwater this will be considered and incorporated
A groundwater assessment was undertaken to understand how groundwater would be impacted by the above change following development, and showed that whilst groundwater levels may become lower in the centre of the site itself (localised to the highpoint onsite), the groundwater levels outside of the site are not anticipated to change from existing. Monitoring is proposed going forward as an additional precautionary measure.

Therefore the Environmental Impact Assessment classified this as ‘not significant’.

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Hilary’s response to Stephen Kelly

Stephen

Thank you for coming back to me with the answers I have requested, I note that your answer to Q3 supplied by Homes England indicates that their lakes are independent of the groundwater unlike the Kingfisher pond. This would imply that the Phase 1 lake is not independent of the groundwater or the Kingfisher pond. As all of Longstanton’s ponds on the RTD gravels are in hydraulic connectivity with the Kingfisher pond it follows that even if we can believe Homes England’s assurances re the phase 2 lakes, the same cannot be said for the phase 1 lake. It would also appear that L&Q did not provide a response to this question nor have they provided any answers as far as I can tell.

With regards the comments that it is the Environment Agency’s responsibility to safeguard the groundwater, they do not appear to agree with you and have stated that this is a matter for the planning authority.

For Homes England to suggest that the drying out of Longstanton’s ponds are solely caused by the hot dry summer of 2022 is ludicrous as they were made aware of ponds drying out across Longstanton since my emails to SCDC, from December 2015 onwards. However, at least Homes England have taken the time and trouble to answer my questions and I appreciate that. I also thank you for coming back to me with this information. It can only be positive to establish direct communications on issues that impact local residents so profoundly.

As far as I am concerned these answers will be put in the public domain and I hope that Northstowe Town Council, Longstanton Parish Council, LEGG and other bodies will seek to independently verify the information provided. The groundwater collapse experienced by Longstanton since dewatering started out on Northstowe in 2015 is having a catastrophic impact on this village and it is not just being manifested by a few drying out ponds and wells. There are now reports of serious structural problems in buildings across Longstanton and these problems have only started since 2015.

We have had a hot dry summer this year but dewatering for Northstowe has collapsed the groundwater and it looks to be permanent. That is contrary to the planning permission and that is something SCDC has to step in to resolve. The decision to dewater in 2015/16 has caused a catastrophe which will mean that Longstanton is less able to withstand the impacts of hot weather going forward.

SCDC failed to take timely action in 2016 and that failure has caused the problem to worsen, with increasingly devastating impacts for Longstanton. The longer it takes for action to be put in place to restore the aquifer, the worse the problem could become. Pretending that Northstowe is not behind the groundwater collapse in Longstanton will not make the problem go away. Mitigation and more independent reports might cost something but it will be insignificant compared with the costs of saving Longstanton buildings from collapse.

Once again thank you for coming back to me, but I suspect this is not the end of the matter.

Kind Regards
Hilary