Teddington Direct River Abstraction (TDRA) Tunnelling Main Works Contract (MWC)

Description

Design, build, test and commission of the following two main components: i) A recycled water conveyance tunnel from Mogden Sewage Treatment Works (STW) to Teddington. A new approximately 4.2km long tunnelled conveyance route approximately 3.5m internal diameter (ID) would be driven using a Tunnel Boring Machine (TBM) and constructed to connect a new Tertiary Treatment Plant (provided by others) in Mogden STW to the proposed outfall on the riverbank of the River Thames upstream of Teddington Weir. The tunnel would have four shafts. ii) River abstraction and transfer to the existing Thames Lee Tunnel (TLT): The river abstraction would be located approximately 175m upstream of the proposed new outfall. The abstracted river flow would be conveyed to the TLT through a smaller diameter (up to 2.2m ID) pipe installed using a pipe jacking technique. The scope will include, but not be limited to: Construction Design activities Architectural Building M&E Civils and Structural engineering including earthworks Enabling works Drainage Geotechnical Ground movement impact Mechanical, Electrical, Instrumentation, Control and Automation (MEICA) including a SCADA (Supervisory Control and Data Acquisition) system Hydraulic Modelling Materials durability Renewables / Carbon mitigation Rivers and Watercourses Traffic & Highways Shafts & Tunnels Utilities Disposal of excavated material The NEC4 Engineering and Construction Contract comprise two stages, with a decision point as to whether to proceed to construction between Stages One and Two. If the decision point is passed, then a Notice to Proceed (NTP) will be issued. Stage One, also known as the Early Contractor Involvement stage, will provide construction related support to the Client during its planning process, which comprises an application for a Development Consent Order (DCO). Using the DCO reference design (provided by others) as a constraint to the scope, the TDRA Tunnelling MWC will develop the design for construction, which will be integrated with construction planning, into the subsequent Stage Two, being the delivery / construction phase. The decision gate to proceed to Stage Two will be dependent on a number of matters, including: 1) An accepted design that meets the requirements of the contract; 2) agreement on a target price; and 3) the granting of the DCO. The agreement of a target price for Stage Two will be constrained by the Client's budget and will be developed in accordance with a Pricing Information Schedule appended to the contract. The Pricing Information Schedule will include an exhaustive list of specific "Adjustment Events" which may adjust the target price for Stage Two. Subject to the Client issuing a NTP, Stage Two will commence with an initial period to comply with any secondary consenting issues, followed by mobilisation to commence construction. Following construction, a testing and commissioning phase will be required with a scheduled target date of Water Available for Use (WAFU) of 31 March 2033.