Customers see looking after our assets – pipes, pumps, works and equipment – as one of our core responsibilities. They want to know that we are investing to maintain them effectively so they provide a good service, now and in the future. A number of ODIs have been put in place to ensure strong service in this area. Four of these ODIs sit under the heading of Serviceability, the key measure of how we invest in assets to keep service at an acceptable level.
Infrastructure refers to underground assets such as pipes, while non-infrastructure refers to above ground assets like treatment works and reservoirs. These ODIs are made up from 13 measures, with our performance against each assessed as green, amber or red. For each measure, we agree a normal or 'reference level', which is typically close to the best historical performance. There is also an 'upper control limit', which is the worst level of performance that can be accounted for by reasonable natural variation. If we perform worse than this upper control limit, the measure moves from green to amber. Perform worse than the control limit for a second year in a row, and it moves to red. If one or more of the measures under an ODI is red, or two or more are amber, then we incur a penalty.
The 2017 results were some of the best for compliance for the quality of water discharged from our water recycling centres. We sample the quality of the recycled water at 755 sites and the results are used as a measure by the Environment Agency to assess our performance. In 2017 we had eight failing works, which is higher than the exceptional performance of 2016, but still an improvement on where we were at the beginning of AMP6. Overall the year ended with all water recycling measures comfortably within control limits, both for water recycling centres and for our sewerage network.
Throughout the year, we have delivered good performance at our water treatment works and across our networks. This included just four works coliform failures, following improvements to our treated water tank inspections.Our performance on reducing pollutions caused by escapes from our water recycling network was very close to 2016 performance with 219 Category 3 incidents (an increase of just two), meaning we remain ahead of our ODI target to have no more than 298 incidents by the end of 2019/20. This number compares to 390 such incidents in 2014, and our priorities remain the same: a continued focus on predictive analytics, to use information on past pollutions to predict where we may have problems in the future, and on proactive mitigation to quickly and efficiently resolve any problems to avoid environmental impact.
This has been our best year to date for the number of internal and external flooding incidents from our sewer network. Our performance in this area is measured against two separate ODIs that look at the three-year average for incidents of internal and external flooding. Three years into the AMP, we are beating our target for both internal and external flooding. The current three-year rolling average for internal flooding events is 396, against a target of 448 for the end of 2019/20, while the figure for external flooding stands at 4,824, against a target of 6,159.
We have continued to spend money on measures such as non-return valves and flood doors, which reduce the risk of flooding to individual properties and which are more cost-effective than large-scale engineering schemes. These schemes might cost millions of pounds to protect a handful of properties, making them an inefficient use of money and limiting the number of customers we could help. To deliver the outcomes our customers want demands the closest possible collaboration between us, our suppliers and our contractors. The majority of our £2 billion investment programme for 2015-2020 will be carried out by our delivery alliances, which will help provide our services until 2020. These differ from alliances elsewhere in the water industry, with an unparalleled degree of integration and alignment.
Our alliances have been tasked with finding further efficiency savings, and we are constantly working to become ever-more efficient, challenging ourselves and setting stretching goals. The emphasis is on the low carbon, low whole-life cost and on-time delivery of schemes while ensuring we meet quality standards. Between now and 2020 we will continue to invest heavily to increase the resilience of our services and protect customers' supplies in the face of growth and climate change. This includes work to:
Since the start of 2008, we have used steam boilers, rather than thermal dryers, to treat sludge at our water recycling centres. The boilers are more sustainable, effective and cheaper to run.
This year we began to roll out a Boiler Operative Accreditation Scheme (BOAS), which allows our boiler attendants to train to become boiler operators. Four have already qualified, meaning they can perform a much wider range of tasks on site. This removes the need for trained operators to travel from site to site, increasing the efficiency and safety of our operation. We aim to have a boiler operator at every site and on every shift by 2020.