Benson Drainage Strategy Stage 1 - Initialise/Prepare Introduction
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Benson 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 Benson Drainage cities, and its urbanised surrounding environments. areas; together with the equally complex Strategy technical document. What can be done and when? Sewer flooding is unacceptable. We have to produce a drainage strategy for our undertaken extensive customer research affected catchments with a primary focus and initiated a programme of work to on our sewerage network. As outlined improve drainage and alleviate sewer in Figure 1, the strategies will develop flooding issues across our region. throughout the 4-stage framework to define how we intend to alleviate sewer We are adopting the good practice flooding or to address growth related Drainage Strategy framework* developed issues in each area sustainably, and by the Environment Agency and Ofwat, economically, over the next few years. the water industry economic regulator, 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. Benson 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 Benson 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. Benson 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 sewerage network activities and plans. We have addressed key feedback and questions raised by customers and stakeholders in the Benson 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 in Section 7 of the Drainage Strategy and stakeholders on our sewerage drainage strategy process, which has document. Our previous investigations network activities and plans. been developed and recommended by have identified some sources of inflow, the water industry economic regulator such as the misconnection of surface Ofwat, and the Environment Agency. This water to foul sewers. However, as stated in will enable us to better understand the the following strategy, we are not yet able root cause of the sewer flooding issues to say how much this impacts on flooding affecting the catchment, before any major and will update this as our plan develops investment can be considered. However, through Stage 2 to Stage 3 –Option we may carry out some repair works as this Appraisal. Therefore, this more detailed strategy develops, in the event that our approach is required to ensure that the investigations identify faults or problems most effective and sustainable drainage with the sewerage network that are highly strategies are implemented in the Benson likely to have caused flooding, as outlined catchment. Q2 What drainage actions are you undertaking in our area, and when will they be happening? Answer As stated above, we are developing our 6 Installation of flow monitors at the plan for this area and will provide further sewage treatment works details as our plan develops through Stage 7 Installation of depth monitors into the 2 to Stage 3 – Option Appraisal. The network following drainage actions have already 8 Installation of low-leak manhole been undertaken, or are underway, in the covers Benson catchment: 9 Flooding clean-up. Actions completed include: (For more Actions underway or planned include: information please see Table 2) (For more information please see Table 4) 1 Manhole surveys 1. Stakeholder engagement activities 2 CCTV survey of our sewer network 2. Connectivity surveys 3 Wet weather event survey 3. Ongoing sewer repair works 4 Sewer repairs – including lining and 4. Monitoring of pumping station sealing of sewer 5. Impact study 5 Installation of non-return valves 6. Innovative solution analysis. Benson 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 through leaking joints. We will continue to damaged, either as they have aged or target and repair localised sewer defects through other streetworks activities. identified through our investigations As outlined in Table 2, extensive sewer as contributing to, or causing, drainage repairs have been undertaken across the and flooding issues in the catchment network within the catchment to try and throughout this 4-stage framework limit the inflows. This action prevents the process. ingress of ground water into sewer pipes Q4 What are the improvement plans for Benson’s sewage treatment works to manage capacity? Answer The Benson sewage treatment works has in light of plans for RAF Benson. In undergone a number of upgrades over accordance with the consent for the the years to meet changing performance sewage treatment works it operates a criteria. The capacity of the works has fully-compliant permanent storm overflow been assessed to be adequate under which permits us to discharge into