Meeting documents

  • Meeting of Services Overview Committee, Thursday, 13th June, 2019 6.30 pm (Item 100.)

To receive an update from Thames Water and other relevant representatives on flood prevention/matters and future challenges within the District.


Thames Water


Members received a presentation from Thames Water representatives, Mr Huw Thomas, Local and Regional Government Liaison Officer and Ms Dagmara Weatherall, Infrastructure Planning Manager on the waste network arrangements and infrastructure in the Chiltern District. The presentation covered the following and can be viewed appended to these minutes:


  • An overview of the Thames Valley sewerage network responsibilities.
  • Drainage Strategies which had included detailed investigations that helped with the understanding of drainage problems in Chalfont St Peter (Maple Lodge) and Chesham and how they may be improved.
  • An overview of the Maple Lodge sewer treatment works which served a population of 495,000 and had a typical daily treated flow of 100,000 cubed metres, this could rise to in excess of 250,000 cubed metres during wet periods.
  • Proposed improvements including sewer repairs with watertight lining; new monitors at some local sewage pumping stations to identify when pumps are operating more than expected; groundwater levels being monitored in the control centre with response teams informed if thresholds passed; and to investigate if roof drainage can be separated from our sewer network.
  • How proposed local plan growth and other key growth challenges in the region would be dealt with. Developers were being encouraged to contact Thames Water in advance of submission of planning applications. Customer relationship managers were proactively seeking out site developers and working to meet developers, promoters and agents for large development sites at an early stage of the planning process.
  • Once a site identified as a risk to the wastewater network had been approved for planning, an impact assessment would be undertaken to identify if there was detriment to the network. Where certainty of growth from other sites was also known then a strategic scheme would be developed.
  • Drainage and Wastewater Management Plans - these were the most extensive, collaborative and forward-looking plans developed within the UK wastewater industry to date. A framework was published in September 2018, this consisted of Water and wastewater companies; Defra; Environment Agency; Ofwat; Consumer Council for Water and; the National Infrastructure Commission.
  • Sustainable Drainage Systems (SuDS) which were an opportunity to remove local impermeable area that would normally contribute to surface water run-off. £150,000 would be made available to all boroughs in the region for the installation of surface water management.


The Committee recorded its thanks to Mr Thomas and Ms Weatherall for the presentation. Questions from Members were welcomed, and the following key points were made:


It was affirmed to the Committee that developers were being encouraged to make use of the free pre-planning enquiry process, following which they would receive a letter outlining whether there was sufficient capacity in the existing network or whether investment was needed. Thames Water was consulted on and made recommendations to the local Planning authority on all significant developments.


Impact assessments would be completed once planning approval for developments had been completed. When these had concluded it would be known how large the solution would need to be and whether existing networks could handle the additional flow.


A statement of common ground agreement was formalised as part of the Chiltern and South Bucks Local Plan, this was signed by Thames Water, Chiltern and South Bucks District Councils and the Environment Agency.


Following a Member comment, it was confirmed that installations which assisted collection of rainwater, avoiding heavy flow into the sewer network such as water butts could often result in a refund to the consumer. This rebate was due to less surface water being dealt with from individual properties. Members suggested that this could be marketed further to make consumers aware.


In relation to the £150,000 investment to local authorities to deal with surface water run-off, it was clarified that this had been set aside for authorities as they were now, meaning that each of the five existing Councils in Buckinghamshire would be entitled to a separate fund of £150,000 with the transition to a unitary authority not having an impact on this.


A Member raised a concern that the sewer which ran through the Misbourne valley from Amersham to Chalfont St Giles appeared to have leakage and asked whether this had been addressed. It was confirmed that the sewer had been investigated and the findings would be reported back to Members. It was understood that the pipes were relatively old and were not sealed the same way as water mains would be.


There were 14 mobile pumping station units strategically placed across the Thames Valley and these were not fixed to individual locations. The units would be moved as and where needed.


Affinity Water


Members received a presentation from Dr Di Hammond on revitalising chalk rivers in the district. The presentation included the following and can be viewed appended to these minutes:


·       The reasons behind the Revitalising Chalk Rivers initiative, these included being more visible and working together to promote the great river restoration work being completed.

·       River habitats and functional feeding groups as well as the effect of restoration on LIFE scores.

·       Catchment changes which may affect the river including dredging and straightening of the river channel; land drainage and loss of wetlands and; urbanisation.

·       Potential benefits of river restoration such as improved fish passage; increased aquatic plant diversity; natural flood risk management; water quality improvement; health and wellbeing and mitigation for climate change.

·       Examples of river restoration work completed in recent years and potential projects at River Misbourne sites including Barn Meadow, the Community Orchard site and Amersham to Quarrendon Mill. An outline design was displayed for the Amersham to Quarrendon Mill river path.

·       The “#whynotwater” campaign which called for government to act on mandatory water efficiency labelling so consumers could make informed choices on appliances purchased; rights for tenants to request landlords install water saving measures; ensure fixtures and fittings met minimum standards to avoid wasting water and every Local Plan in a severely water stressed area should include the target of 110 litres per person per day.


The Committee recorded its thanks to Dr Hammond for the comprehensive presentation. Questions from Members were welcomed, and the following was clarified to the Committee:


It was confirmed that the plan was for work to commence on the River Misbourne toward the end of 2019.  A Member highlighted the importance of being mindful when dredging not to destroy the lining of a river as this could prevent the river from filling. It was confirmed that Affinity would plan to dig any new channels close to groundwater, maintaining inflow. The aim was to make the river more natural and resilient to river droughts.


Buckinghamshire County Council


Mr Alex Back, Senior Strategic Flood Management Officer, Buckinghamshire County Council clarified the responsibilities of each agency and reported an update on an ongoing project to increase flood resistance measures for properties in surrounding areas of culverts. This included measures such as electrics being wired high up, appliances being kept above flood level and solid wood floors. These resilience measures would reduce the time people need to spend out of their properties. Businesses were also an area of focus to ensure that the impact from flooding would not keep them closed for a significant period. The County Council was a statutory consultee on all major planning applications and the lead local flood authority who had a statutory duty to investigate any kind of flooding.


Environment Agency


Members received a presentation from Ms Natasha Gibbs, Technical Advisor on the two main rivers running through the district, the Chess and the Misbourne and the flood alerts and warnings which were in place.


The flood warnings were established based on full modelling being completed following the wider flooding of the River Misbourne in 2013/14. The Environment Agency was working closely with Affinity on the restoration of chalk streams and was also working on ensuring that the HS2 project did not have a significant impact on the Misbourne.


All options for improving the Misbourne had been deemed economically unviable at present as the Environment Agency had been unable to secure funding. It was hoped that the programme would be explored again post 2021 when grant aid and the flood risk settlement had been agreed.


Further work was being undertaken to engage riparian landowners to ensure assets and river banks were adequately maintained to reduce flood risks and meetings were being held with partners to address maintenance. Should any Member wish to know the grade of a culvert at any given time there was an asset mapping online service (link included below) which they could use.


The Environment Agency continued to monitor ground water levels to predict implications on the Misbourne network. Culvert inspection took place every 5 years as per T98 inspection. It was said that a Grade 4 culvert was deemed ‘poor’ and would likely see an increased number of inspections. Grade 5 culverts required immediate attention.


A Member asked what needed to be done where severe water loss could be seen and was advised that there was an incident hotline (noted below) and members were encouraged to report all expected issues, whether these were on private land or not so that these could be inspected.


Members raised the Culvert at the Maltings, Amersham as a concern, this culvert was graded as a 5 and it was advised that this would be checked by the Environment Agency prior to any expected heavy rainfall. Members were encouraged to forward any concerns to the EA.


The useful links and contact information are as follows:


The online asset map which detailed all assets the Environment Agency holds information.


The May 2019 water situation report which contained information around the Chilterns Chalk levels was also available online at - e-mail address to be used for information around certain assets or watercourses. - e-mail address to be used to provide information around works near a river. The webpage to visit beforehand for further information was


The incident hotline: Telephone 0800 80 70 60


The Chairman thanked Ms Gibbs for her detailed presentation.