WET News

wwtonline.co.uk | FEBRUARY 2019 WET NEWS 13 Manufacture and Assembly (DfMA) process, which was used for over 80 per cent of the pro- ject's MEICA. "Offsite build was used extensively, and that was one of the benefits from the model," Jones says. "DfMA was a pretty new way of working for the Tul- lich team – none of us had really worked with offsite manufac- ture to the scale we did on this job. "We've found the 3D model very good for working with fun- damental things like clash detection, and the benefit of using 4D Synchro as a planning collaboration tool is that, when we come to move some of our quite complex offsite manufac- ture structures, we know exactly where we need to put The team was able to reuse 90 per cent of excavated materials TACKLING TREATMENT The original Tullich Water Treatment Works, which had been in operation since the 1970s, used an ozone system with granular activated carbon (GAC) filters. In recent years, though, its treatment processes had been struggling to cope with changes in raw water quality, reflected by trihalomethane (THM) failures in the distribution system, while its vulnerability to cryptosporidium was also cause for concern. "The original plant was ageing and it had become very labour-inten- sive to maintain, and very expensive," Barclay says. "Generating ozone gas was also a very high-risk activity, although it was under control at all times." "The technology was fine for its time, but it needed to be replaced," Burns adds. The new plant, which became operational at the end of last year, has brought marked improvements. It features dissolved air flotation (DAF) and rapid gravity filters (RGF) as well as a secondary filtration stage for the removal of manganese, in addition to a more user-friendly layout. "With this new plant, the water quality is fantastic, and it offers great reliability and ease of use – a very simple changeover from the old works to the new one has made it operator-friendly," Barclay says. NEED TO KNOW • Construction work began in early 2016 and completed in late 2018 • Tullich WTW serves around 12,000 residents, although numbers increase substantially in the summer due to tourism • The £29 million project represents one of Scottish Water's biggest ever investments in the Argyll and Bute region aggregate, cutting the need to transport and dispose of materials. "One of our efficiency levers is our carbon footprint," Jones says. Such initiatives helped reduce construction traffic through Oban and, with events having been held to talk through the plans with the local commu- nity, there has been little cause for concern among residents. The new works became oper- ational late last year and Bar- clay says: "Reaction from the community has been very positive. "Any customer that we've spoken to has been really delighted about what we're try- ing to achieve here. They under- stand we had to build it, and most importantly the water is equipment, almost on an hourly basis. It makes planning that activity much smoother." The DfMA strategy meant less plant equipment was required onsite, helping to over- come the challenge of working within a constrained location. They were also able to reuse 90 per cent of the excavated materi- als from the site. "That was one of our very early innovations," Jones says. "The treatment works is set 1km to the south of Oban and the nearest batching plant is in the town, and the next batching plant to that is on the other side of the town, and so are the quarries." Rock excavation was carried out using a Rock Hawg surface miner, which provided 50mm clearer and fresher. It's all been really positive." Collaborative digital engi- neering has undoubtedly played a major part in the project's suc- cess, and is set to remain a cor- nerstone of the team's modus operandi moving forward, with ESD now also making use of technologies such as augmented reality goggles and laser scanners. "For Tullich, it's helped us coordinate multiple contractors working on a relatively confined site and therefore minimise dis- ruption," Jones says. "Our col- laborative approach ensured buy-in from all stakeholders, including our supply chain, and it's without doubt reduced the potential for additional costs and delays." BIM was integral to the project

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