Talking leakage with Thames Water
Thames Water loses more than a third of its water through leaks. WWT talks to leakage strategy manager Mark Simister about how the company is aiming to cut these lossesThames Water supplies 2,900Ml/d of water, of which 850Ml/d is currently lost through leakage. Although the company has undertaken work to reduce the levels of loss, Thames' leakage levels have remained stubbornly high. Ofwat has set the utility an economic level of leakage goal of 725Ml/d, to be achieved by March 2010.
MS Two primary factors affect leakage in London: the age of the network and the soil conditions. Half of our mains are more than 100 years old. One third are more than 150 years old. The soils are corrosive, 40% are highly or very highly corrosive to iron mains compared with a national average of 23%. London clay is very hostile to ductile iron.
The pipe laid in the 1950s has been particularly susceptible to the aggressive conditions in north London. The clay is also very susceptible to movement arising from changes in temperature and moisture levels. In the autumn, after drying out in summer, the clay gets wet and swells putting strain on the pipes.
WWT How does leakage reduction fit into Thames' overall demand/supply management strategy?
MS It is an important part of the overall strategy. We are looking at a range of solutions to tackle supply and demand issues in the Southeast. It is not seen as sustainable to continue to take more from existing resources, so part of our strategy is to reduce the volume of leakage. At the same time, we are seeking additional resources, such as our desal scheme.
We have discussions with the mayor as well as other bodies in London, such the GLA [Greater London Authority], about our overall philosophy for London and how we are going to deal with things such the city's growth and the 2012 Olympics. In the next ten years an additional 800,000 people will move to the capital. We need to supply them, and if we are unable to take additional resources from the environment, which is already stretched, we need to be working harder to resolve issues we have with the current state of the network.
WWT How is the leakage management programme structured?
MS We do not view the problem as being the domain of any single element of the business, it is a company-wide activity encompassing operations, asset management, regulation, R&D and engineering. There is something in the order of 30 different work streams within the business looking to tackle leakage. The Leakage Strategy Team is a central function within the business. Our primary role is to be the link between engineering, operations and asset management;
determining the most appropriate intervention methods.
There will be various work streams within engineering that we will link into. For the Victorian Mains Replacement [VMR] and Burst-Rate Driven programmes primary design is undertaken by in-house teams, with some consultancy support. Modelling is done by a mixture of in-house and outsourcing to Atkins. There also is the Network Improvement Team, using primarily in-house resources with contracting support from RPS, Mouchel Parkman and Biwater. On the operational side, leak detection in north London is broken up into three primary units with teams from Biwater, Mouchel Parkman and PM Daley. In south London, we have Morrison and PM Daley. PM Daley also handles the Thames Valley. The contractors for repair are Enterprise in north London, Morrison for south London and Morrison and McAlpine for the Thames Valley.
On the operations side, all the detection and repair is outsourced. We do have some of our own active leakage technicians but most detection activity is contractor led. We have around 400 contractor staff working purely on leak detection, and about the same on repair.
WWT How do you prioritise the work?
MS The network is broken up into 800 DMAs [district metered areas]. They are all on the telemetry network, so real-time data is fed into the corporate systems. Each zone has a dedicated engineer who, along with analysts, reviews information from the district meters, data on customer usage, population density information and other operational activity on the network. They also look at historical information on burst numbers and interventions. This is how zonal engineers initially establish where the issues are. This is followed up by teams on the ground using digital correlators, or more conventional leak detection methods such as step testing or dynamic partitioning. There are also set intervention levels that trigger work.
When we are making a decision about whether a problem should be tackled with pressure management or whether we should consider replacement, this is the approach we take.
WWT What approaches is Thames and its partners putting into action in the field?
MS From an operational viewpoint, as well as listening sticks and standard acoustic loggers, we are using digital correlating loggers and multi-point digital correlation.
WWT Is the digital kit significantly different?
MS The way we use it, yes. There are a couple of zones in north London we have worked thorough completely using multi-point digital correlation. Digital correlators are able to extend the range of sound we can detect at. It can function when background noise is greater than 50% of the sound you are listening for. Multi-point correlation will enable us to pinpoint leaks form even further away.
We are looking at mass deployment of them, doing a sweep of DMAs overnight, then downloading and interrogating data to pinpoint areas of interest and generating thematic maps to show the hot spots.
Then we undertake follow-up work. Instead of people doing standard checks across the whole DMA, they can be sent to look at specific areas where there is a lot of noise. Having addressed these, we do a secondary sweep to look at quieter areas which still represent a cause for concern. Through further phases, we start driving down the levels of noise. We have found this to be a very successful way of operating, especially in north London. It is a complex, busy environment, using this has reduced our volume of night working.
WWT What approaches, other than find-and-fix, are you adopting to remedy the leakage problem?
MS We are looking to get reductions from a variety of sources: metering policy, replacement, pressure management and reconfiguration.
WWT Can you elaborate on the reconfiguration programme?
MS Historically, some large supply zones in north London have been gravity fed. But now we have the London Ringmain, there are a lot of pumped sections of the network. This begs the question: do we need to have the zones in the same configuration? The absolute pressure levels you have towards the Thames are very, very high, which puts a lot of strain on the older sections of the network. We've reconfigured it, smoothed out network connectivity and pressure
levels along the southern end.
What we are looking to do is make a calm network. With the current configuration, quite a lot of the pumping regimes have to reflect changes in diurnal usage. What we are trying to do is see if you can minimise the variations in pumping to try and smooth the pumping impacts on the network - switching on and off pumps to try and maintain a stable profile.
WWT So the aim is not to reduce pressure throughout the network?
MS No, we want to have a more even pressure, to try and remove fluctuations. There is a belief that we want to reduce pressure across London, that is not the case.
The key is understanding how the zones are configured. The demands upon them and the way they are operated has changed massively since the networks were first designed. They have evolved, so we should be looking at how the zones can be reconfigured so they reflect current levels of demand.
WWT Does reconfiguration work require the installation of new pipework?
MS There are some additional network connections, but the majority of it is looking at how these things are functioning and trying to remodel how large-scale parts of London are going to operating.
WWT So it is not necessarily about putting in new assets, but looking at what's there and how it can be better managed.
WWT And when reconfiguration is unsuitable, replacement becomes an option?
MS Yes. This is a supply-and-demand-based decision. On the VMR programme, we found the condition of the network on some DMAs was such that it is economic to replace everything. The VMR began in Finsbury Park, replacing something in the region of 26km of network supplying 7,000 properties.
We completely remodelled the network within the area, looking at current demands and those projected for the next 25 years. This is a job for modelling, operations and engineering and something we do for every DMA in the VMR programme. We install new communications pipes and install a boundary box and meter on every exit from the network. I think is radically different from the way every other water company is undertaking mains replacement.
We are working very closely with the local authorities on the VMR. It is seen as a very positive thing to be future-proofing the network and presenting a planned wholesale programme of work rather than emergency interventions.
WWT And your choice of pipework?
MS All MDPE.
WWT Is rehabilitation an option?
MS For the VMR or burst-driven programmes, there is no rehabilitation, only replacement. We are swapping cast and ductile iron, and PVC mains. One area in which we are being very innovative is the amount of minimal-dig technologies we are using. We try and maximise that type of activity - technologies such as pipe bursting, slipline insertion and directional drilling. Two-thirds to three quarters of our programme is being undertaken using minimal-dig.
WWT Is that a requirement you place on the contractor or a decision the contractor will make?
MS The final decision will be the contractor's but we are pushing them in that direction. This is very much led by us. I think contractors would often prefer to be open cutting. But it is quicker to use no-dig technology, more environmentally friendly - there is less backfill - and the speed of the operation means less disruption to residents and traffic.
WWT You've talked about how long the network you are replacing on has served the city. How long do you expect the pipes you are putting in to last?
MS Manufacturers generally used to talked about a 60-year life span but they are now talking about 100 or more years. That is what we are basing our design parameters on. It is a long-term planning solution, it is not economic to continue looking for leaks and patching up an
WWT Despite this the company is still criticised for its leakage levels. Is there more you could do?
MS London can only stand a certain level of streetworks activity. We are looking to undertake 350km of mains replacement per annum. That is an awful lot of activity, centred mostly in north London and central south London. Couple that with the volume of leakage-related interventions we undertake, in the region of 80,000 per year including customer-side work. It has to be recognised we can't bring London to a standstill just to resolve leakage issues. You have to work in a pragmatic way.
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