Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/1006919
Databank www.wwtonline.co.uk | WWT | AUGUST 2018 | 29 GOAL 7 SEWER FLOODING Sewer ooding – and particu- larly internal sewer ood- ing incidents where sewage enters a customer property – can have a severe impact on customers' lives and so it is understandable that the number of such incidents is a key metric for the regulation of wastewater companies. For PR19, Ofwat will use the number of internal ooding incidents per year – includ- ing those brought about by severe weather – as one of the common performance commit- ments for wastewater utilities. Recent years have seen a reduction in sewer ooding, but 2016-7 reversed this trend. There were 5,690 properties in England and Wales a† ected by internal sewer ooding in 2016-17, a rise of almost a third on the previous year. United Utilities – which saw a huge increase in incidents from 1,111 to 2,110 aˆ er two major storm events – was responsi- ble for a signiŠ cant proportion of these. Thames Water was the second biggest contribu- tor with a rise from 1,029 to 1,429 incidents, which was also partly down to extreme weather. In total, six of the 10 wastewater companies in Eng- land and Wales saw the total number of internally ooded properties increase. With climate change bring- ing more extreme weather events and clustered popula- tions putting pressure on sew- er networks, companies are urged to take a more proactive approach to the problem – to use modelling techniques to predict and avert problems, and gain a better understand- ing of the catchment to imple- ment more e† ective drainage, including SuDS. Encouragingly, Northum- brian Water has seen a year-on- year decrease since topping the charts with 2,112 in 2012-13, with its 2016-17 total standing at just 124. There was also an improve- ment in external sewer ooding overall, with an 11 per cent annual reduction in 2016-17 and a 36 per cent reduction over a Š ve-year period. SEWER FLOODING United Utilities had 6.38 incidents of internal sewer fl ooding per 10,000 connections Industry average is 2.29 incidents of internal sewer fl ooding per 10,000 connections Wessex Water had 0.64 incidents of internal sewer fl ooding per 10,000 connections 5,690 Properties that were internally fl ooded by sewage in England and Wales from April 2016 to March 2017 33,481 Areas that were externally fl ooded by sewage in England and Wales from April 2016 to March 2017 United Utilities had 11% Reduction in areas fl ooded externally in 2016-17 36% Reduction in areas fl ooded externally 2012-17 2012-13 2013-14 2014-15 2015-16 2016-17 Anglian Water 2.2 1.41 1.66 1.5 1.55 Dwr Cymru Welsh Water 1.8 1.37 1.06 0.87 1.06 Northumbrian Water 16.92 4.07 1.9 1.39 0.98 Severn Trent Water 2.24 1.62 1.84 1.22 1.3 South West Water 3.71 2.06 1.62 1.55 1.18 Southern Water 3.23 2.43 1.63 1.91 1.7 Thames Water 2.29 1.95 1.98 1.78 2.46 United Utilities 5.49 3.09 2.5 3.39 6.38 Wessex Water 1.95 1.09 1.03 0.82 0.64 Yorkshire Water 2.7 1.69 1.98 1.83 1.83 2012-13 2013-14 2014-15 2015-16 2016-17 Anglian Water 25.83 20.74 21.92 19.53 18.33 Dwr Cymru Welsh Water 33.69 26.81 22.28 22.17 17.08 Northumbrian Water 20.39 12.67 9.37 9.27 6.02 Severn Trent Water 17.9 15.13 18.43 14.63 12.9 South West Water 27.65 24.89 21.97 19.73 16.39 Southern Water 40.94 40.26 31.05 24.64 22.61 Thames Water 13.39 12.5 11.72 10.98 8.7 United Utilities 17.87 12.07 11.55 12.07 12.82 Wessex Water 23.04 18.39 14.09 12.78 11.57 Yorkshire Water 21.62 15.78 16.44 16.35 15.62 source: CC Water Properties fl ooded internally per 10,000 connections Water & sewerage companies - England and Wales Areas fl ooded externally per 10,000 connections Water & sewerage companies Source: Water UK Number of properties aff ected by internal sewer fl ooding in England and Wales 2012-13 8,659 2013-14 4,959 2014-15 4,523 2015-16 4,344 2016-17 5,690 Source: CC Water