Sewer flooding guidance and technical information.

Transcription

1 Sewer flooding guidance and technical information

2 Sewer flooding is a very serious issue and Northumbrian Water is committed to reducing the risk of it occurring in our region. Whilst we are able to identify the cause and resolve a great number of flooding problems quickly there are occasions when more detailed investigations are needed. To ensure that all customers receive the same high level of service, all incidents of sewer flooding are dealt with under our sewer flooding procedures. The information contained in this leaflet has been developed in consultation with the Consumer Council for Water, who independently represent the interests of our customers. It offers guidance, gives details of the process and an awareness of what actions may need to be taken before we are able to establish and resolve the cause of individual flooding problems.

3 What to do if you suffer sewer flooding It is essential, and in your best interest, to contact your household insurance company immediately to inform them of a flooding incident. If you have suffered any loss or damage your insurers will provide advice as to what action you need to take to ensure the terms of your policy are met. Turn off your gas and electricity supply if the inside of your property is flooded. Please also telephone our freephone flood line on Please provide as much information as you can so that we can accurately record details of the flooding event. Be aware that our customer advisors may ask additional questions to ensure we have all of the information needed to prioritise your call effectively. If the problem is thought to be with one of our sewers, arrangements will be made for one of our sewerage teams to make an initial visit. We will try to attend to all reported flooding problems within four hours. However, in the event of severe weather and widespread flooding it will take our representatives longer to attend. In this event, we will inform you of the problems being encountered due to the numbers of calls being received and if possible give you an indication of when we hope to attend. Customers who have suffered flooding to the inside of their home will receive priority assistance. If you or a member of your family have any special needs please let us know straight away. This will help us when prioritising a visit to your home. From Saturday 1 October 2011, Northumbrian Water is responsible for the ownership and maintenance of many private drains. If you believe the flooding was caused by one of our existing or newly transferred sewers, or you are not sure, please telephone our flood line where one of our advisors will be happy to help you. Type of flood water Flood water can originate from several sources: Surface water. Foul and combined sewers. Rivers flooding into the sewerage network. However, all flooding should be considered to contain contaminants, even if it looks clean. Also there may be hidden hazards under the water, eg dislodged or missing manhole covers. When an area is flooded: Supervise children closely and never let them play in the water. Contact Northumbrian Water on and arrange for the area to be inspected and if necessary, decontaminated. Does sewer flooding pose a health risk? Sewer flooding largely consists of water and domestic waste from bathrooms and kitchens. During wet weather it is likely to be highly diluted by rainwater. If you adopt normal basic hygiene precautions and follow the instructions provided, you are unlikely to be at any increased health risk. Wear rubber gloves when clearing up flood water damage and be careful of sharp objects. Use waterproof dressings to cover cuts and wounds. Always wash hands after exposure. Wash and treat footwear with a mild disinfectant. Keep children and pets out of the contaminated area. In the unlikely event of you feeling unwell, visit your GP as a precautionary measure and explain that your property has been flooded.

4 What causes sewer flooding? The main causes of sewer flooding are: Blockages. Defects (such as collapsed sewers, deformed pipes and open joints). Mechanical failure such as pumping failures. Overloaded sewers (flows are too great for the size of the sewer). Blockages Serious flooding can occur, especially in heavy rainfall, if the sewer becomes blocked. Common causes of blockage are: Fat and grease Pouring hot or cold fat, cooking oil and grease down your sink and drains can block sewers as the fat and grease harden in the cold underground pipes. Disposable products So called disposable products are frequently flushed down toilets, including sanitary products, cotton buds and nappies. These should be disposed of in the bin, never in the toilet, as they do not dissolve on the way to the sewage treatment works and either cause blockages in sewer pipes or have to be removed at the treatment works and sent to landfill. Building debris Household bricks and building debris can find their way into sewers and drains causing blockages. Tree roots Tree roots seek moisture. In sewers and private drains they will find a way through the smallest crack or joint and grow inside the pipes. The adjacent photograph, taken during a closed circuit television survey, shows tree roots blocking a sewer. Flooding from blockages can be largely prevented. For more detailed information and guidance leaflets about what can or cannot be flushed away, and how to dispose of fat and grease, please contact our customer centre on

5 Defects (Collapsed or deformed pipes and open joints) The collapse of a sewer can cause flooding by blocking the sewer and/or reducing the amount of sewage that it can deal with. A sewer collapse can occur for many reasons such as material failure, overloading, ground movement and third party interference. surfaces due to house extensions, conservatories, patios, decking, drives, etc, means that there is now less area for rainfall to soak into the ground. As such, there is more water entering the sewer which results in the sewer no longer being large enough to take the flows entering it during more intense rainfall. This can sometimes result in sewer flooding. A collapse may be suspected if there are persistent blockages, escape of sewage in an unusual place or evidence of ground disturbance near a sewer. Problems of this type are confirmed by Closed Circuit Television (CCTV) analysis and are usually dealt with quickly. Mechanical failure Rarely, failure of pumps and other mechanical equipment can cause flooding. Failure can be caused by: Power problems Emergency generators are held and routinely utilised for power failure problems. However, in extreme weather events when whole regions are without power we may have hundreds of pumping stations affected and will not be able to provide emergency power for all. Mechanical problems We usually prevent mechanical equipment failure by carrying out routine inspections and preventative maintenance. However, as with all mechanical equipment, failures can happen. If mechanical problems occur we will attend the problem and take appropriate action. Overloaded sewers Flooding problems can only be attributed to overloaded sewers after there has been a comprehensive investigation and may require very large investment projects to solve. Sewers are designed and built to deal with a predicted amount of flow. This prediction is based on the size of the area drained, the number of customers connected to the sewer, and the predicted rainfall run off from properties. The content of a public sewer is mainly dependent on the amount of roof area, highway and other hard surfaces that are present. Most sewerage systems were designed and built many decades ago. Gradual increases to hard Overloaded sewers (exceptional storm events) Sewers are designed to manage predicted flows from the area and also normal storm events. Exceptional storms can cause sewer flooding. If flooding occurs as a result of severe rainfall an initial site visit will be carried out once the flooding has subsided. This visit will allow us to identify and resolve any problems which may have contributed to the flooding, such as blockages or tree roots. If the site visit does not identify what caused the flooding, a CCTV survey of the inside of the public sewer may also be needed to further check the condition of the pipes. This will help us to ensure that any necessary repairs are made to the sewer. If the sewer is found to be operating normally and this is the first time flooding has occurred at the property, we will conclude that the exceptional rainfall event caused the flooding. If flooding has happened before or if you experience flooding again, further more detailed investigations may be necessary. We may also carry out a flooding assessment to help us build an accurate picture of what happened before, during and after the flooding. If it is established that flooding will only occur as a result of exceptional storms then investment projects are unlikely to be carried out.

6 Types of sewerage systems Sewerage systems are designed in different ways: Drainage responsibilities Combined sewer system surface water (from rainfall) and sewage (wastewater from buildings) are in one pipe; in this case the pipe is designed to take the high volume of water expected during low intensity rainfall. This mix of rain and sewage is delivered to a sewage treatment works where it is treated. The flows in this type of system may be controlled by combined sewer overflows (CSO) to provide protection against flooding during more intense storms. As most of the water in the sewer in intense storms is rainwater the CSOs are designed to overflow this rainwater into watercourses. Separate sewer system surface water (from rainfall) is in a separate pipe from the sewage. The surface water sewer is designed for the high volume of rain water and usually discharges directly to a stream or river with no treatment. In this case the foul pipe is only designed to take the low constant flow of sewage from buildings. River levels Sewers are designed to discharge into watercourses during rainfall events. These discharges can be from outfalls from surface water only systems or from overflows on combined sewer systems. Sometimes during long periods of wet weather or very heavy rainfall, these outfalls cannot discharge due to the raised level of the receiving river or watercourse. If this level is caused by a severe storm and this is the first time flooding has happened we will conclude that exceptional rainfall caused the flooding. If you experience flooding again, further more detailed investigations may be necessary. Where there are separate systems, surface water from rainfall must never be connected to the foul system as it may overload and cause flooding. Similarly, foul water systems must never be connected to the surface water as this may result in polluted streams and rivers. Flooding can only be attributed to incorrect drainage connections after there has been a comprehensive investigation and may require very large investment projects to solve. If you are extending your home, building a conservatory or are making any alterations to your property that require plumbing or drainage works, you must make sure that you connect to the correct private drainage system. For example, all bathroom and kitchen connections must be made to a foul drainage system. This may be a separate foul or a combined drain. Rainwater guttering should connect to the surface water drainage system if the systems are separate. The type of drainage system that exists can be confirmed by the local building control officers who will be able to give you advice about these matters. Further information is also available on the Connect Right web site at

7 Our sewer flooding procedures Following your initial telephone call to report sewer flooding, arrangements will be made for one of our sewerage teams to visually inspect the public sewer. If the team can determine what is causing the problem, for example a blockage, arrangements will be made to resolve the problem. Our team will also, where necessary, help you to clean up in accordance with our procedures (please refer to page 4 for more information) if your insurance company have not already attended. Whilst we are able to deal with the majority of sewer flooding incidents quickly, there are occasions when more detailed investigations are needed before we can identify and resolve the cause of the flooding. CCTV survey If a CCTV survey is needed to look at the inside of the public sewers, this is done by lowering a specially designed camera into an open manhole. Once in place, the camera will record images of the condition of the pipe as it moves along the sewer. A detailed report will be compiled highlighting any problems within the sewer. This information is monitored and a detailed report is compiled which highlights any problems in the sewer. Once we have assessed the report and CCTV footage, arrangements will be made for any necessary repairs or cleansing work to be completed within our works schedule. In the event that the sewer is found to be operating normally we will use the rainfall data collected through the Met Office North East Weather Radar Station to identify if the flooding occurred due to an exceptional rainfall event. Flooding assessments These assessments form an important part of our investigations as they help us to build an accurate picture of what happened before, during and after the flooding. Customers hold valuable information having experienced the flooding first hand and it is important that we capture this information as it will help us to target further investigations more accurately. The surveys will also ensure that we have an accurate record of your problems and are able to contact other customers who may also have suffered flooding. Your help is greatly appreciated and any information given will be dealt with in strict confidence and used to help us to target investigations more accurately. Investigating the cause of flooding If the results of the CCTV survey have not revealed the cause of the flooding, and you have not suffered flooding for the first time due to exceptional rainfall, we will need to carry out a much more detailed investigation and examine the possibility that the flooding may have occurred due to overloaded sewers or incorrect connections, etc (see section on page 5 Causes of flooding for more information). This investigation will examine the public sewerage system across a wider area and include any neighbouring properties which also suffered varying degrees of flooding to allow us to establish the likely cause and location of any problem within the public sewerage system. If it is confirmed that the flooding happened for the first time during exceptional rainfall, we will conclude that the rainfall event caused the flooding.

8 Flooding protection Where an initial investigation report identifies that a sewer is overloaded, it will clarify whether any temporary measures can be installed which may help to reduce the risk of internal flooding until a longer term solution is found. Flooding protection measures can include contouring, air brick modifications, raising doorways or providing flood proof doors, guards and non return valves. All protection measures will be considered, however each location must satisfy our flooding protection policy before they can be installed. Prioritising flooding problems If it is established that the flooding was caused by overloaded sewers, then problems will be prioritised for investment (all of the properties found to have suffered flooding by the same problem will be included). We use a strict prioritisation process to ensure that available funding is used to provide best value for our customers. This was developed after asking customers what they were willing to pay to resolve flooding issues and also which issues they considered to be the most important. Customers told us that the highest priority should be given to those customers suffering frequent flooding to the inside of their home that results in their home not being habitable for a period of time. They gave us a range of preferences from their highest to lowest priority and these are used to prioritise our investment. If a problem has been prioritised for investment a project will start and the first step is a detailed engineering study. This study may take many months to complete as detailed investigations of the sewerage network will need to be carried out. These will include the completion of a detailed computerised model of the sewerage network in the area to establish how the system operates during normal and exceptional storms and will identify a number of different solutions to reduce the risk of flooding. It is essential that we ensure that any proposed solutions will not create a flooding problem elsewhere in the sewerage system. On completion of the study, a preferred solution will be identified. This solution may include increasing the size of existing sewers, diverting flows to another sewerage system or constructing new storage tanks, overflows or pumping stations. A solution may include some or all of these options. We will also consider installing small cut and pump solutions. These comprise of the removal of the existing gravity connection to the public sewer and the provision of a privately owned and maintained, pumped connection to the public sewer. Once an option has been identified and approved, we will produce a detailed design in readiness for construction. When we have a date for starting construction, we will write to you with full details. We will also notify you on completion of the project to inform you that your property has been removed from our sewer flooding register. (See the sewer flooding registers section below). There are some circumstances when we are unable to carry out a solution to a flooding problem. In these instances we will contact you to discuss the reasons for our decision. Sewer flooding registers Northumbrian Water, along with the other water and sewerage companies, is required by Ofwat, the Water Industry Regulator, to maintain a register of properties which are currently under investigation or are confirmed as being at risk of flooding due to overloaded sewers. This is when the flows are too great for the size of the sewer. If our investigations conclude that your property is at risk of internal flooding due to overloaded sewers, we will write to you within ten working days of the investigation report being completed, providing detailed information on your property s position within our prioritisation process. We will continue to keep you informed on progress at least once a year. Properties will be removed from our sewer flooding register if investigations confirm the cause of the flooding is not due to overloaded sewers or on completion of a permanent flooding alleviation scheme. We will notify you in writing once your property is removed from our register.

9 Guaranteed standards of service sewer flooding If you suffer flooding to the inside or outside of your property due to a problem with the public sewerage system, you will receive a payment in accordance with our guaranteed standards of service. If the inside of your property is flooded from one of our sewers we will refund an amount equal to your full sewerage charge for the year, or pay you 150, which ever is more (up to a maximum of 1000) for each flooding incident that happens. If the outside of your property is flooded from one of our sewers we will refund an amount equal to 50% of your sewerage charge for the year, or pay you 75, whichever is more (up to a maximum of 500) for each flooding incident that happens. As long as we know that you have flooded, after carrying out any investigations which we feel are necessary, we will automatically make these payments, whether or not you are covered by insurance. If we do not make these refunds within 20 working days of being notified of the flooding event, we will pay you an additional 20 ( 50 if you are a business customer). Our standards of sewer flooding do not apply if the flooding is caused by: Something you have done. Any fault or blockage in your own private drains or sewers. Exceptional weather conditions. Industrial action by our employees. For further information on all of our guaranteed standards of service, please contact and ask for the Our promise leaflet. Alternatively, visit our website at Keeping you informed We take all reports of sewer flooding very seriously. Following the completion of our investigations into the cause of the flooding we will contact you to inform you of our findings and any actions we have take to resolve the problem. In addition, because we appreciate that internal flooding is very distressing and one of the worst problems that can occur at your property, we have a dedicated team of experienced sewer flooding customer advisors working within our customer centre. This team of advisors monitor the progress of all reported incidents of internal flooding. Following a reported flooding event affecting your property, one of our experienced advisors will become personally responsible for the management of your problems. Having familiarised themselves with the flooding history of your property they will contact you within five working days providing their full name and contact details for your future reference. During this initial call your dedicated advisor will go through our sewer flooding procedures and advise you of the steps we will be taking to resolve the problem. In addition, they will offer practical help and advice where needed and discuss any payments which you may be entitled to under our guaranteed standards of service. They will also answer any queries or concerns you may have regarding the flooding you have encountered. Throughout the investigation process, our advisors will ensure that you are kept fully informed of developments. Our dedicated advisors will be happy to discuss any queries or concerns you may have at any time during the investigation process so please feel free to contact them directly on the number provided if you require any additional information.

10 How to contact us We always recommend that you speak to your dedicated advisor on the direct number provided if you have any concerns or wish to make a complaint, as we can often resolve issues more quickly and accurately if we can discuss these in detail with you. Alternatively you can speak to one of our customer advisors at our customer centre by calling if you do not have a dedicated advisor. Where needed, our advisors will also be happy to provide more detailed information on our complaints procedure over the phone, or we can arrange to send you our complaints leaflet entitled Getting answers, which is also available on our website at This leaflet outlines our internal complaints procedure and also explains the role of our regulator, the Consumer Council for Water, should you wish to contact them directly having exhausted Northumbrian Water s complaints procedure.

11 Northumbrian Water Abbey Road Pity Me Durham DH1 5FJ September 2011