Charlton- on-Otmoor Drainage Strategy Stage 1 - Initialise/Prepare Introduction Why sewer flooding Britain’s first sewerage systems were challenges arising in our predominantly This document contains: constructed 150 years ago in the rural catchments in the Thames Valley, Victorian era, and have served us well for Surrey and Kent. • an Introduction to the work generations. The sewer network Thames we are undertaking to Water operates today has been much A number of factors including population alleviate sewer flooding in improved and vastly extended over the growth, less frequent but heavier rainfall, years; yet it remains under increasing the urbanisation of green spaces and our region pressure. changes in agricultural land practices, • a Feedback: Q&A section and utilised machinery, occasionally addressing key questions Everyday our network manages the overwhelm our sewer network. The result from customers and demands of one of the world’s busiest can be unwanted sewer flooding for stakeholders and most densely populated capital customers and our neighbouring natural • the Charlton-on-Otmoor cities, and its urbanised surrounding environments. areas; together with the equally complex Drainage Strategy technical document. What can be done and when? Sewer flooding is unacceptable. We have the water industry economic regulator, undertaken extensive customer research to produce a drainage strategy for our and initiated a programme of work to affected catchments. As outlined in Figure improve drainage and alleviate sewer 1, the strategies will develop throughout flooding issues across our region. the 4-stage framework to define how we intend to alleviate sewer flooding or to We are adopting the good practice address growth related issues in each area Drainage Strategy framework* developed sustainably, and economically, over the by the Environment Agency and Ofwat, next few years. Figure 1 High-level Drainage Strategy framework* and estimated delivery and intervention timeline** From 2018 2015 - 2017 onwards We are Stage 1 Stage 2 Stage 3 Stage 4 here Initialise/ Risk Options Intervention prepare assesment appraisal Implementation of Long-term capital 'quick-win' operational investment solutions as appropriate interventions * The detailed 4-stage Drainage Strategy framework can be found in the following Drainage Strategy document. ** The estimated delivery timeline is dependent on factors including weather conditions and is, therefore, open to change. The intervention timeline includes the implementation of ‘quick-win’ operational solutions throughout Stage 2 & 3, and long-term capital investment interventions in Stage 4. Charlton-on-Otmoor Drainage Strategy - Stage 1 1 Published version post stakeholder review v1.1 Who will resolve the sewer flooding? There are a number of stakeholders land and highways, utilising appropriate who, like us, have important drainage agricultural practices and maintaining responsibilities and therefore, play an private drains. essential role in resolving sewer flooding in our region. These stakeholders include We take full responsibility for resolving all customers, private land owners and the drainage and sewer flooding issues that Environment Agency; to name but a few. fall within our remit. If the causes of sewer We are seeking to work in partnership flooding sit outside of this, we will support with all stakeholders to ensure that the responsible stakeholder to resolve together, we implement and maintain the the issue and to reduce the impact on most effective and sustainable drainage customers. strategies. Figure 2 provides a high-level view of the Just as our responsibilities to improve stakeholders responsible for drainage drainage and alleviate sewer flooding in each catchment area, more detail focus on removing and treating regarding responsibilities can be found wastewater; other stakeholders’ in Section 1 of the following Drainage responsibilities include managing local Strategy document. flood risk on riverbanks, ground water, Figure 2 Partners with Drainage Responsibilities Thames Customers Water Land and Council/ Responsible Riparian Highways Drainage Owners England Partners Council/Lead Environment Local Flood Agency Authority Charlton-on-Otmoor Drainage Strategy - Stage 1 2 Published version post stakeholder review v1.1 Next steps Over the coming months we will undertake the following activities as this drainage strategy develops: We will regularly consult • Continue to consult with customers with customers and 2015 - 2017 during this stage and every stage, stakeholders, update and through meetings, communications republish this document and surveys. We have gained important customer feedback during this first throughout this 4-stage Customer stage, which we are using to shape our framework process. Focus Actions activities • Publish strategy documents for comment and contribution, throughout this framework process. Partnership • Continue to establish partnership Actions working with the regional drainage stakeholders, and agree ongoing consultation processes. • Define catchment flooding Other Key uncertainties Actions • Prepare flooding risk data • Undertake ongoing repair work to our sewer network, as the strategy develops and our investigations identify reparation work linked to drainage and flooding issues. Charlton-on-Otmoor Drainage Strategy - Stage 1 3 Published version post stakeholder review v1.1 Feedback: Q&A Your questions answered We are committed to listening to, consulting and collaborating with customers and stakeholders on our activities and plans. We have addressed key feedback and questions raised by customers and stakeholders in the Charlton-on-Otmoor catchment, and customers affected by flooding throughout the region, in this Feedback Q&A section. As far as possible, and as is relevant to Stage 1 in the framework process, we have incorporated feedback from customers and stakeholders into our network strategy development. More detail can be found throughout the following Drainage Strategy document. Q1 Will undertaking this Drainage Strategy framework We are committed to process defer essential work in our area? listening to, consulting and Answer collaborating with customers It is essential for us to complete this flooding. Our previous investigations have and stakeholders on our sewerage drainage strategy process, which has identified some sources of inflow, such as network activities and plans. been developed and recommended by the misconnection of surface water to foul the water industry economic regulator sewers. However, as stated in the following Ofwat, and the Environment Agency. This strategy, we are not yet able to say how will enable us to better understand the much this impacts on flooding and will root cause of the sewer flooding issues update this as our plan develops through affecting the catchment, before any major Stage 2 to Stage 3 – Option Appraisal. investment can be considered. However, Therefore, this more detailed approach is we may carry out some repair works as this required to ensure that the most effective strategy develops, in the event that our and sustainable drainage strategies are investigations identify faults or problems implemented in the Charlton-on-Otmoor with the sewerage network that are highly catchment. likely to have caused, or contributed to Q2 What drainage actions are you undertaking in our area, and when will they be happening? Answer As stated above, we are developing our Actions underway or planned include: plan for this area and will provide further (For more information please see Table 4) details as our plan develops through Stage 2 to Stage 3 – Option Appraisal. 1. Stakeholder engagement activities The following drainage actions have 2. Ongoing repair works to our already. The following drainage actions catchment sewer network have already been undertaken, or are 3. Monitoring of pumping stations underway, in the Charlton-on-Otmoor 4. CCTV survey catchment: 5. ‘Lift and Look’ surveys 6. Impermeable areas surveys Actions completed include: (For more 7. Customer survey information please see Table 2) 8. Innovative solution analysis. 1 Infiltration Investigation 2 CCTV survey 3 Temperature sensing trial Charlton-on-Otmoor Drainage Strategy - Stage 1 4 Published version post stakeholder review v1.1 Q3 Are you renovating the sewers in our area? Answer We will renovate sewers which have been target and repair localised sewer defects damaged, either as they have aged or identified through our investigations as through other streetworks activities. As the contributing to, or causing, drainage and Drainage Strategy work continues, we will flooding issues in the catchment. Q4 What are the improvement plans for Charlton-on- Otmoor’s sewage treatment works to manage capacity? Answer The Charlton-on-Otmoor sewage If this current position changes as our treatment works operates a fully- investigations through this 4-stage compliant permanent storm overflow framework progress, we will consult which permits us to discharge into local with customers and stakeholders on our watercourses during storm events. To proposals, and republish them within the meet changing performance requirements later stages of this Drainage Strategy and regulatory measures the works has document. undergone a number of upgrades and there are currently no plans to increase capacity further. Q5 Are you working with the Highway Authority to resolve blocked gulleys, sewers and ditches, and with landowners to reduce field run-off, as both affect drainage