London’s 150-year-old sewerage system was designed to meet the sewer needs of four million people. However, as the city’s population nears nine million, it is unable to cater to the rising sewage flow from the city. This has subsequently led to the overflowing of the sewer systems into the river Thames, thus necessitating the creation of a new alternate tunnel to accommodate and divert the increasing sewage.
In 2015, the Water Services Regulation Authority sanctioned the Thames Tideway Tunnel project, the new alternate sewerage system to tackle the overflows from London’s sewers to the Thames river. The new tunnel is being designed and constructed to solve the problem of sewage for at least the next 100 years. The objective of the tunnel is to reduce the combined sewer outflows (CSO) and plastic/litter sewage in the Thames river. The new system is also expected to improve the quality of water of the river. The work on the Thames Tideway Tunnel is spread across 24 construction sites and split into three work zones (East, West, and Central)
The Thames Tideway Tunnel project is a 25-km long and 65-metres below ground super sewer system. It is the largest water infrastructure project ever undertaken in the United Kingdom. The GBP 3.8 billion (USD 5.05 billion) tunnel is being built beneath the Thames to prevent millions of tons of waste being poured into the river. It is being undertaken by Bazalgette Tunnel Limited on the finance, build, maintain, and operate business model, and is stipulated for completion by 2024. For completing the preparatory works, an additional amount of GBP 1.1 billion (USD 1.46 billion) has been spent by the client, the Water Services Regulation Authority, on the project. With most of the tunnel length under the Thames river, the project runs from the Acton Storm Tanks (West London) to the Lee Tunnel at Abbey Mills (East London).
Since the beginning of the project, the stakeholders faced many geological and geophysical engineering challenges, some of which are listed below:
Geophysical survey: One of the key challenges faced by the stakeholder in planning and designing the tunnel was to accurately locate World War II bomb shells that were lodged in the Thames riverbed. To locate the bomb shells, Vision Survey, the utility surveying company, conducted geophysical surveys using Ground Penetrating Radar (GPR) and Electromagnetic Locator (EML) tools and technologies to locate all metal objects on the riverbed.
Sustainable approach through ‘More by River’: Bazalgette Tunnel Limited, the main contractor of the Thames Tideway Tunnel project, made an investment of nearly GBP 54 million (USD 71.7 million) under the transport scheme ‘More by River’, to transport the construction materials and machinery by water. The aim of the scheme was to minimize the burden on roads and lessen the disturbance to the urban environment; thus, around 4 million tons of the construction material was transported via barges. This use of the river as a mode of transport saved time and improved energy efficiency by leading to reduction in carbon dioxide and nitrogen oxide emissions.
The Water Services Regulation Authority, or Ofwat
Bazalgette Tunnel Limited
West Contract BMB Joint Venture
Central Contract FLO Joint Venture
East Contract CVB Joint Venture
Program Manager: Jacobs
In the initial phase of the project, Vision Survey Ltd., the utility surveying company for the project, conducted PAS128 utility surveys using GPR and EML tools to map and locate the sub-surface utility networks. By locating the sub-surface utility networks, the contractor could easily plan and manage the excavation operations beneath the Thames river in the West and Central zones of the project. Adhering to the PAS128 specification for completing the utility surveys, the processed GPR data was incorporated with the EML data to a compliant utility service drawing on the AutoCAD software. These generated reports were then used by the excavation teams to define the ‘Permit to Dig’ locations.
For the East section of the Thames Tideway Tunnel project, a number of digital initiatives have been taken up by the CVB Joint Venture (Costain, VINCI Construction Grands Projects, and Bachy Soletanche Joint Venture). To streamline workflows, optimize decision-making, and improve understanding between stakeholders, a connected data environment with 4D construction modeling was implemented for the project. The use of 4D in construction planning reduced the overall construction time by 90 days in the plan and design timeframe, saving GBP 1 million (USD 1.2 million) in indirect cost and GBP 300,000 (USD 399, 098) in direct costs. The use of 4D modelling is expected to reduce up to 50% of the manual work in the future.
The CVB-JV also used the Azure Cloud platform to provide access to accurate data, ensuring improved coordination and collaboration in real-time. The exchange of BIM models between the owner and operator was done using iModels, saving the contractor approximately 22.5 man-hours per week. Using the digital approach increased collaboration and cooperation among the supply chain stakeholders and ensured a 32% savings on the developed design.
On the West section of the project, the contractors used 3D design models while also utilizing virtual reality (VR) Fulmax cubes on site. This enabled the site personnel to walk through the digital models of the site in real time and provide inputs to improve the site activities. Along with using VR the on-site maintenance work by the mechanical and electrical team was done fully digitally using Field 360 software on iPads.
Similarly, on the Central section, 3D models were used for sequencing, live progress reporting, planning, efficient progress monitoring and to communicate in a collaborative environment. In a collaborative and connected data environment, the project delivery partners were able to share the access to the design file with each stakeholder (client, suppliers and subcontractors). A 4D construction model was duly created and shared to communicate and compare the planned progress with the actual progress of the project. The use of 360-degree cameras on project sites enabled the team to quickly address possible hazards using the in-house reality capture platform (RCP). Daily inspections on the project sites were carried out using Virtual Reality (VR) platforms to capture any anomalies and signs of failure.
In 2018, through an independent Social Return on Investment (SROI) assessment commissioned by Bazalgette Tunnel Limited, it was estimated that for every pound spent, an estimated return of GBP 3.39 is expected on the delivery of the project in 2024
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