WET News

4 WET NEWS JUNE 2018 | wwtonline.co.uk NEWS+ Tunnelling team hand-dig 20-metre stretch of sewer beneath Edinburgh • Specialists used to avoid damaging utility infrastructure T wo tunnellers have helped Scottish Water progress a major new sewer beneath Edinburgh by hand-digging 90 tonnes of debris. The century-old sewer under Haymarket Terrace was built by Victorian water pioneers in the capital but is now being upgraded to meet the city's modern needs, and a challeng- ing section required a hands-on approach with the pair – Gerard Boyce and Thomas Peoples – using tools to dig their way through a 20-metre stretch. Working over a two-week period in a trench beneath Hay- market, one of the busiest trans- port hubs in the capital, the two men shovelled between 6 and 9 tonnes per day. The busy junction outside Haymarket Station was hand- tunnelled to avoid damaging a complex web of utility infra- structure such as electricity, gas, telephone lines and broadband. Scott Fraser, Scottish Water's corporate affairs regional man- ager, said: "The original sewer was built by Victorian engineers using old-fashioned methods. "Whilst we're using a range of high-tech solutions to help progress this vital work to upgrade the sewer at Haymar- ket, we've had to use those same basic tunnelling tech- niques as the Victorians to clear this particular section. "The £2.5 million work at Haymarket is one of our most high-profile projects due to its busy location and the small, challenging work site. "This unique environment means we are using traditional techniques combined with mod- ern technology to efficiently tunnel under a section of road with a large number of vital Scottish Water employed ASG Tunnelling & Civil Engineering Services to precisely hand-exca- vate sections of tunnel where tunnel-boring machines are not appropriate for the terrain conditions. John Doherty, managing director of ASG Tunnelling & Civil Engineering Services, said: "We are one of the few remain- ing family-run firms that have utilities, which if damaged could impact local residents and businesses. "The two tunnellers used modern equipment such as gas detectors, laser technology and hydraulic drills to cut the rock face whilst the earth was then shovelled by hand into a tradi- tional cart on rails, which was then li—ed by crane back onto the surface." the knowledge and experience to take on these hand-tunnel- ling projects. "I'm extremely proud of hand-tunnellers Gerard and Thomas, who have completed this work in challenging condi- tions due to the confined space underground and the sheer number of utilities we encoun- tered and had to work around to get the section completed." CONTRACT WINS Wessex Water is reported to have awarded J Murphy and Sons a £43 million contract to work on its North Bristol sewer improvement programme. Construction Enquirer said work is due to start in late 2019 for completion by 2023. Anglian Water has awarded the management of its third-party standpipes to Aquam, a provider of risk mitigation technologies for water and energy transmis- sion and distribution assets. The agreement began on 1 April 2018 and will initially operate for a three-year period. Scottish Water has announced a five-year 'digital partnership' with Capgemini and Atos. It says that the deal will place technology and innovation at the heart of Scotland's water supply and wastewa- ter management. Severn Trent's recent checks of its sewers in Cheltenham show there is no longer any fat build- up after the company joined forces with both national and local food chains such as YO! Sushi, JD Wetherspoon and The Mayflower to raise awareness of FOG and help prevent sewer blockages. South West Water was ordered to pay £71,800 in fines and costs after being prosecuted by the Environment Agency for failing to correct faults at its Dartmouth and Salcombe sewage treatment works, leading to both sites breaching their environmental permits. Both sites suffer from saline water infiltration. Good monthT- Bad month Wessex teams up with Sydney Water to extend sewer's life W essex Water has formed a partnership with Syd- ney Water that it believes will help to prolong the life of a Bournemouth sewer by 200 years. Built between 1964 and 1971, the coastal interceptor sewer (CIS) is 8km long and 1.8m in diameter and serves a population of around 34,500. Surveys showed the first 200 metres of the tunnel had suffered biogenic corrosion, meaning it needed to be re-lined to prevent collapse. The tunnel receives a maxi- mum flow rate of 650 litres per second from two rising mains – the Hengistbury Head (500mm diameter) and the Ilford (400mm diameter). Julian Britton, Wessex Water's trenchless technology programme manager, said: "The Ilford rising main is long and has a reduced number of starts, resulting in the sewage resting quiescent for long peri- ods of time. "Consequently, anaerobic con- ditions allow the formation of hydrogen sulphide, which con- verts to sulphuric acid via bacteria that feeds upon the nutrients readily available. This in turn corrodes the concrete." Wessex Water commissioned Dr Ian Bateman, a leading net- works consultant from Australia, to verify the effectiveness of cal- cium aluminate cement (CAC) and its ability to resist high levels of sulphuric acid. Little was known about CAC as a corrosion barrier in European sewerage systems, yet Sydney Water was known to have used the material for concrete protec- tion for more than 15 years. Nathan Hand, critical sewers engineer at Wessex Water, said: "CAC has the advantage of greater resistance to hydrogen sulphide attack, down to a pH of 3.5, and forms a gel layer on its surface. "We spent a lot of time researching it in collaboration with Sydney Water, and we're the first water company in the UK to use this product to line a sewer." The £1 million Bournemouth CIS project embraces both new concepts and historic solutions. "We used the latest 3D Building Information Modelling technol- ogy to locate the sewer under- ground and managed to sink a sha— within 50mm of the side of the sewer," Hand said. "We're looking to remove some of the energy from the sewage and reduce the turbulence, as this is what releases the hydrogen sul- phide gas and causes corrosion. "To do this we're using an energy dissipating vortex, using technology that was originally invented by the predecessors of Wessex Water, Bristol City Coun- cil, back in the 1950s. We've kept customers informed to minimise disruption to them, carrying out letter drops and sending text mes- sages at weekends. "This scheme will ultimately prolong the life of the asset by up to 200 years." Siege Breaker creates 3km Newark tunnel S evern Trent's 'Siege Breaker' tunnelling machine has completed its nine-month journey under the streets of Newark to create a 3-kilometre tunnel. Since launching in August, the machine has created a huge tunnel from Crankley Point to Millgate as part of the company's £60 million invest- ment in the town, where it is upgrading both the water and waste system. Nick Wallace from Severn Trent said: "It's really exciting that the 'Siege Breaker' has completed its journey. "This is such an important part of the project that will play a huge role in making sure the people of Newark won't have to worry when it rains anymore, as these bigger and better sewers will help protect their homes from flooding." The 'Siege Breaker' weighs 160 tonnes – one-and-a-half times as heavy as an average blue whale – and is 75 metres in length. The state-of-the-art machine had been travelling under- ground for nine months, creat- ing a tunnel that is big enough for a transit van to drive through. "It's amazing to think that this huge machine has trav- elled underground, all without anyone really knowing it's there," Wallace added. "By tunnelling, we've been able to massively reduce the disruption caused to the town by our scheme, as the majority of the work is taking place under the roads, rather than on them." When completed, more than 400 homes and busi- nesses will have extra protec- tion from sewer flooding, with 15 miles of new and improved water and waste pipes built for Newark. "We're making some real progress with our work in Newark," Wallace said. "We're really thankful for everyone's continued support and under- standing as we make these essential improvements." BNM Alliance is carrying out work on behalf of Severn Trent.

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