Burghfield Drainage Strategy

Burghﬁeld drainage strategy.

Work so far.

2019 Contents.

Summary 2

Our drainage investigations so far 5

Findings so far 8

Our next steps 9

Appendix 10

1 Summary. We’re working on how to reduce the risk of sewer flooding, pollution, blockages and restricted use of toilets and bathrooms in the Burghfield area. For us, it’s a priority. We’ll continue to work with our customers and other stakeholders, such as West Berkshire Council and private land owners, to take action and make drainage improvements as quickly as possible.

Our drainage strategy work We began our drainage strategy work Since 2016, we’ve carried out some in 2015 by carrying out research and detailed investigations which have regularly meeting with customers who helped us to understand more had been affected by drainage issues, about the drainage problems in the as well as stakeholders in the area. Burghfield area, and how they might be improved in the future.

From 2018 ** 2015 - 2017 onwards The drainage strategy process Stage 1 Stage 2 Stage 3 Stage 4 We’ve followed the guidance from ‘Initialise/ ‘Risk ‘Options ‘Intervention’ our regulators, Ofwat and the prepare’ assessment’ appraisal’ Environment Agency, for our drainage strategy work. The good-practice We're process they recommend has four here stages*. We completed the first stage in 2016, which included a range of What this means background research into the drainage issues in the area. Initialise/ Risk Options Intervention prepare assessment appraisal Starting the Identifying Developing Implementing process the things that different selected drainage including could prevent options for improvements gathering drainage making based on their information improvements, drainage potential benefits and forming and how to improvements outweighing their relationships manage that work and costs and their with them are value for priority stakeholders money

* ofwat.gov.uk/publication/drainage-strategy-framework-for-water-and-sewerage-companies-to- prepare-drainage-strategies. ** The estimated delivery timeline is dependent on factors including weather conditions, risks and costs, and is, therefore, open to change. Drainage strategy framework stages and timescales 2 Annual rainfall from April 2016 to March 2017 compared to the yearly Work so far Cherwell average across our region

We’ve put together stages two and Cotswolds-East Lee-Chalk three of the drainage strategy process as their activities are closely linked. So Cotswolds-West Thame Roding Chilterns-East-Colne far in this combined stage we’ve: Lower Lee

Ock Upper Thames • Completed some detailed Chilterns-West North London investigations in the Burghfield Berkshire Downs Cut area and identified the others Ramsbury South London Burghﬁeld Enborne Lower Wey that need to happen Loddon Nth Downs- Sth London

Nth Downs-Hants Upper Mole Wey-Greensand • Started to assess the risks in the area and how we’ll manage them, such as its growing population and rising groundwater levels Annual rainfall from April 2017 to March 2018 compared to the yearly Cherwell average across our region • Achieved some immediate drainage improvements through Cotswolds-East Lee-Chalk delivering some interventions

Cotswolds-West Thame Roding ourselves, and by working with Chilterns-East-Colne

stakeholders to deliver others that Lower Lee Ock are outside of our control. Upper Thames Chilterns-West North London

Unfortunately, we haven’t been able Berkshire Downs Cut South London to complete this combined stage for Burghﬁeld Enborne Lower Wey the Burghfield area as we’d hoped Loddon Nth Downs- Sth London to do at this time. This is because Nth Downs-Hants Upper Mole Wey-Greensand of the unusually dry winter weather experienced across the majority of our region between 2016 and 2017, and throughout the following winter of Annual rainfall from October 2017 to 2017 and 2018. During these periods September 2018 compared to the yearly rainfall was mainly at, or below, the Cherwell average across our region yearly average for our region, as illustrated by the maps*. Cotswolds-East Lee-Chalk

Cotswolds-West Thame Roding Chilterns-East-Colne The dry winter weather stopped us from carrying out a number of the Lower Lee Ock Upper investigations that we needed to fully Thames Chilterns-West understand the root causes of the North London

Berkshire Downs Cut drainage issues. Therefore, we’ve been South London Burghﬁeld unable to finalise our proposals at this Enborne Lower Wey Loddon Nth Downs- Sth London time, to improve the drainage issues in Nth Downs-Hants the Burghfield area for the long term. Upper Mole Wey-Greensand Below average rainfall Average rainfall (approximate) Above average rainfall

Source: Thames Water, 2018, based on provisional and unverified data from the Environment Agency. * For more information on current rainfall and groundwater conditions across our region please use this link: 3 thameswater.co.uk/Help-and-Advice/Water-Quality/Where-our-water-comes-from/Reservoir-levels-and-rainfall-figures. Our ongoing work

We’re extending our drainage strategy We’ve joined together with more than Our DWMP will detail the current work in the Burghfield area. We’ll 40 organisations from across the water and emerging drainage risks continue to assess and respond to the industry to support this groundbreaking across our region, our customers’ drainage risks that we identify through programme. We all recognise the drainage issues and needs, the our ongoing monitoring of rainfall current and future challenges we face operational requirements we have and groundwater levels, together with from factors including climate change and the technological and innovative the flooding trigger levels that we’ve and population growth, and we’re advancements we’ll use. Overall, developed to manage the volume of committed to creating more resilient our DWMP will detail the long-term flows within our sewers. drainage systems to cope with them. interventions we propose to achieve safe and reliable drainage and If the weather is much wetter over The 21st Century Drainage Programme wastewater services within our region, the coming months, we’ll also be has also highlighted the need for water for many years to come. able to finalise our investigations companies to adopt a consistent and drainage strategy for improving approach to drainage and wastewater Therefore, the long-term drainage the drainage issues in the Burghfield planning. In response, by 2022, and interventions that we select for area for the long term. To develop this at regular intervals after that, each implementation in the Burghfield area our first activity will be to assess all water company in England and Wales within our drainage strategy, will also of our proposed long-term drainage will produce a new document called a feature in detail within our DWMP interventions. As well as looking at Drainage & Wastewater Management when it’s introduced. The new planning their potential customer benefits and Plan (DWMP)*. This will build on the process and DWMP documentation investment costs, we’ll also assess good-practice drainage strategy will then replace the existing drainage how they support the fundamental framework process we’ve been using, strategy process and documentation. aims of the 21st Century Drainage and the drainage work we’ve already Programme*. carried out.

* You can find out more about the 21st Century Drainage Programme and Drainage & Wastewater Management Plans, by using the following link: 4 water.org.uk/policy-topics/managing-sewage-and-drainage/drainage-and-wastewater-management-plans. Our drainage investigations so far. Since 2016, we’ve carried out a number of investigations in the Burghfield area. They’ve helped us to understand more about the root causes of the area’s drainage problems, and how they might be improved in the future.

So far our drainage investigations have included:

Customer and Flow and stakeholder asset surveys consultations We checked the performance of our We sent sewer-flooding sewer network and the main assets questionnaires to our customers in the we operate in the Burghfield area. Burghfield area. We wanted to hear We placed three rain gauges and their drainage views and experiences, five flow monitors within the sewers and to pinpoint problem locations. We across the area. We also installed a also met with West Berkshire Council sewer rising main monitor at our to discuss their drainage issues. Sulhamstead Crossroad sewage pumping station and carried out manhole inspections. This helped us to understand if our assets were contributing to the area’s drainage issues.

We’ve also planned an extensive CCTV survey of the sewer network in the Burghfield area. This is ready to be undertaken when groundwater levels are high enough for potential sewer defects to be identified.

5 x

Site Flooding walkovers 'trigger-levels' We investigated beyond our sewer analysis network to find the root causes of We analysed the groundwater levels other drainage issues in the area, and river levels that were recorded such as flood water from rivers and during periods when there was surface water runoff from flooding and other drainage issues agricultural land that may find its in the area. We wanted to use this way into our sewer manholes. information to help us to define groundwater thresholds or ‘trigger levels’.

If these levels are reached in future, it could trigger our local response teams to carry out specific work to help prevent the flooding and drainage issues, such as removing excess water from our sewers using lorries that carry large water tanks, (we call them tankers).

6 Immediate drainage improvements. In carrying out our investigations in the Burghfield area we identified some actions that could achieve immediate drainage improvements. We’ve put a number of these in place already, and supported drainage stakeholders to deliver others, including:

Fixing sewer defects Our asset surveys found minor defects in We repaired the sewer defects and installed network, and prevent flooding and loss some of the sewer pipes and manhole five low-leak manhole covers to prevent of service for our customers in the area, covers around the Burghfield area, which further groundwater from entering our particularly during wet weather conditions. could allow groundwater to enter our sewer sewers via this route. This work will help network. to increase the capacity within our sewer

Installation of sewage pumping station monitors

We’ve installed a sewer rising main monitor and supporting communication tools at our Sulhamstead Crossroad sewage pumping station (SPS), circled in red on the map. Burgh eld sewage treatmentBurgh eld works STW

This will help us to keep a close check on Sulhamstead Road (Burgh eld) SPS how our sewage pumping station is working Crossroad (Sulhamstead) SPS and alert us to any issues, so that we can reduce service disruptions for our customers.

Complete

Sewage pumping station monitor installation in the Burghfield area.

7 Findings so far. The drainage investigations that we’ve carried out so far have helped us to understand some of the root causes of the drainage issues in the Burghfield area. We propose to carry out further drainage activities (we call these interventions), to improve the drainage issues we’ve found so far, in both the short and long term.

Our findings from the drainage investigations we’ve completed so far include:

Maintaining Rising ground- our assets water levels We found We found Our assets such as sewers, manholes and pumps can be damaged Groundwater can enter our sewers when levels are high which in many ways, from age deterioration and blockages, to roadworks reduces their capacity and increases their risk of flooding. There’s and tree roots. Plan to identify a number of defects that are a strong link between the rising groundwater levels across the allowing groundwater to enter our sewers. We’ll continue to Burghfield area and the drainage issues some of our customers inspect our assets, and try to fix any problems we find that are have experienced, including sewer flooding and restricted use of causing significant drainage issues. their toilets and bathrooms.

Our proposed interventions Our proposed interventions • Reinforce sewer repairs with watertight lining. • Monitor groundwater levels in our control centre and inform our • Identify locations that require sewer repairs. response teams if thresholds are passed. The teams will carry out an action plan specifically designed for the area to reduce or remove the flooding issue, such as checking sewer water levels Benefits of proposed interventions and using tankers to take away excess flows from our sewers. • Increase the capacity of our sewers and reduce the risk of sewer • Monitor the new sewer rising main monitor at our Sulhamstead flooding through repairing damaged pipework, sealing manhole Crossroad sewage pumping station, to help us to identify when covers and monitoring the operation of our sewage pumping our pumps are operating more than we expect them to. This station flows. could mean that groundwater is entering our sewers which • Help us to maintain our wastewater services to customers in the shouldn’t be there. We’d investigate further to find out the root Burghfield area during wet weather. cause of the drainage issue affecting our sewage pumping station. Delivery timeframe Proposed for 2018- 2025. Benefits of proposed interventions • Give us the capability to predict and prevent some sewer flooding issues before they occur, through monitoring groundwater levels and sewage pumping station flows. • Increase the capacity of our sewers and reduce the risk of sewer flooding when tankering is used to remove excess flows from our sewers. • Help us to maintain our wastewater services to customers in the Burghfield area during wet weather.

Delivery timeframe Proposed for 2018- 2025. For more information on the flooding ‘trigger-level’ survey and analysis that we carried out as part of this work, please see the Appendix.

8 Our next steps. Our next steps are to extend our work in the Burghfield area. Over the coming months, if this is a much wetter period, we’ll be able to carry out further detailed investigations and finalise our proposals for improving the area’s drainage issues for the long term. This will be the core of our drainage in the Burghfield area within our reliable drainage and wastewater strategy, and an essential part of the drainage strategy, will feature in services within our region for many Drainage & Wastewater Management greater detail within our DWMP when years to come, will then replace the Plan (DWMP) that we’ll produce for it’s introduced. existing drainage strategy process and our whole region by 2022. documentation. The new planning process, and The long-term drainage interventions DWMP documentation outlining that we select for implementation our proposals for achieving safe and

Over the coming months our work in the Burghfield area will continue to be focused on:

Further drainage Stakeholder investigations engagement Carrying out further drainage Attending West Berkshire Council investigations including checking the meetings to regularly update on performance of our local sewage our findings and progress. We’ll pumping stations. We’ll make sure that also offer advice on how everyone they’re working at their best and not can help improve drainage in the more than they should be, which can area. often mean water is entering our sewers that shouldn’t be there. We’ll investigate further any issues we find to help us to improve drainage in the Burghfield area. Flooding Maintaining our ‘trigger-levels’ plan sewers Improving the accuracy of our Ongoing sewer inspections in the flooding warnings or ‘trigger levels’, x area and trying to fix any problems and planning how we can best we find that are causing significant respond if they’re triggered. This will drainage issues. help us to manage the flooding in the area and reduce other drainage issues. x

Our next steps

9 Appendix.

Flooding ‘trigger-levels’ analysis We analysed the groundwater levels and river levels that were recorded during periods when there was flooding and other drainage issues in the area. We wanted to use this information to set up groundwater warning signs or ‘trigger levels’ so that we could investigate the impact this groundwater has on our sewers.

We defined red and amber ‘trigger Figure 1 demonstrates the relationship Ongoing monitoring will increase levels’, with red being the most critical between sewer network issues and high our understanding of how our sewer warning sign. A red ‘trigger level’ tells groundwater levels, particularly when network copes with different weather us that sewer flooding is very likely and the red warning ‘trigger-level’ threshold patterns and groundwater conditions. that rapid action is needed to reduce has been reached. This will help us to plan how we can the drainage issues. An amber ‘trigger further reduce sewer flooding and level’ warns that sewer flooding is We propose to continually check and drainage issues for our customers in the possible. refine these flooding ‘trigger levels’ Burghfield area, now and in the future. to improve their accuracy, particularly If an amber level is reached our local when ‘trigger levels’ have been reached. team will check for unusually high activity at our sewage pumping Number of reported flooding incidents Vs Groundwater levels at Newbury sewage treatment works borehole stations. This could be a sign of 2.2 72.5 groundwater entering our sewer 72 network which shouldn’t be there. If 2 a red level is reached the team will lift manhole covers in areas known to 71.5 1.8 flood, to make sure that our sewers 71 have a safe level of water in them, and Red trigger level 1.6 we can reduce their risk of flooding. Amber trigger level 70.5 Groundwater level (mAOD)

Figure 1 is a graphical illustration of Number of flooding incidents 1.4 our flooding ‘trigger-level’ analysis for 70 Burghfield. In Figure 1 the blue line 1.2 illustrates the changing groundwater 69.5 level over time, and the red and orange 1 69 lines indicate our proposed red and 01/01/2013 20/07/2013 05/02/2014 24/08/2014 12/03/2015 28/09/2015 amber warning ‘trigger levels’. When Newbury sewage treatment works borehole Flooding the groundwater levels exceed these Figure 1 Flooding ‘trigger-level’ analysis for the Burghfield area. ‘trigger levels’ flooding incidents are likely to be reported, as indicated by the orange circles on the graph.