ag wilson civil engineering OBAN NETWORK IMPROVEMENTS

The overall scope for this Water Infrastructure project within the resort town of Oban required the replacement of an existing 12” AC trunk main with fusion welding and the installation of over 2.3km HighDensity Poly Ethylene (HDPE) pipe of varying sizes across challenging terrain. The works were undertaken by AG Wilson as the Main Contractor on behalf of Scottish Water delivery partner Caledonia Water Alliance and completed a £4.6 million network investment in Oban, Argyll & Bute The project was programmed over a duration of 16 months and encountered a range of difficult geological ground conditions. The first phase of programmed works commenced in November 2020 and was divided into five areas which involved the replacement of 1.8km of pipework between Colonsay Terrace and the junction of McCaig Road with the A816. The final phase required the installation of an additional 500 metres of new pipes, connecting into existing infrastructure at Tullich water treatment works. Many constraints had to be overcome on this complex project, from crossing a busy A road to tunnelling below the main railway track into the town. These vital transport links could not be closed, so innovative engineering solutions were required to overcome the constraints. This involved a delicate operation to tunnel 15m beneath an important railway line and also below a box culvert crossing the A816 road, which was surrounded by rock. This involved round-the-clock drilling, which was carried out by our approved subcontractors with no impact on the railway line or Scottish Water customers. A convoy traffic management system was utilised along the A816 road to protect the workforce and the public throughout the works. Within the project, the key focus was placed on lifetime operational use, by incorporating this into the design deliverables, all apparatus which needed to be operated was located off the carriageway. This has an added benefit that all ironwork and lids are offline and not within the pavement.

In the long term, this means that the road surface has not been damaged. AG Wilson was involved with this project from its outset with key influence on the design to ensure delivery. The company utilised technology and innovation to complete the tunnels below the railway with a Gyro tracking system to trace the direction and depths of pilot bores. Throughout the scheme, we managed to install the pipeline outside of the road network where possible to ensure minimum disruption to the locals. Where works have been completed on the carriageway a full-width reinstatement was completed to improve the road. Due to Oban’s remote location, the availability of materials and lead times during the Covid pandemic proved challenging. To manage this we adjusted the design to more standardised items with availability in the central belt and organised our own transport to ensure ‘just in time’ deliveries were achieved. This crucial planning exercise enabled AG Wilson to deliver the project on time and within budget.

Before work commencing and during the construction phase our team engaged with the local community (schools, businesses and residents) to build and maintain positive relationships. On completion of

Project Focus

Oban Network Improvements

Client: CWA / Scottish Water

Value: <5M the pipeline, AG Wilson installed a new polymetric long jump to the rear of the high school’s all-weather pitch to enhance the area. Sustainable initiatives also involved engagement with Oban High School to share project information with their STEM department and facilitating a site visit for the students to see the complex operations and gain an understanding of the engineering technicalities and H&S procedures on a project of this scale. Throughout the construction phase, our company demonstrated the necessary skills, knowledge, experience & organisational capability to undertake Contractor duties under Regulation 15 of the Construction (Design & Management) Regulations 2015. This was evident through our excellent safety record on site and zero reportable incidents. Through its completion, the new re-routed water main will help reduce the risk of flooding in the Soroba area of Oban, which has experienced significant bursts, causing flooding to Scottish Water customer properties for several years. A robust and reliable water supply was therefore essential, and our experienced team worked incredibly hard in often challenging circumstances and conditions to successfully deliver this project.