Groundwater Monitoring Services

The Thames Tideway Tunnel is a major infrastructure project, urgently needed to protect the tidal River Thames from increasing pollution. London’s sewerage system is no longer fit for purpose and spills tens of millions of tonnes of untreated sewage mixed with rainwater (combined sewage) into the tidal reaches of the River Thames every year. Bazalgette Tunnel Limited (BTL), is the licensed provider set up to finance, build, maintain and operate the Thames Tideway Tunnel. From Licence Award BTL trades and is known to the public as 'Tideway'. Tideway is upgrading London’s sewer system to comply with UK obligations under the wastewater directives and cope with its growing population. Our 25km tunnel will intercept, store and ultimately transfer storm sewage away from the River Thames. Construction of the Thames Tideway Tunnel is planned to be completed during 2024 followed by periods of system commissioning and system acceptance testing. During the project construction phase groundwater monitoring and dewatering activity has been undertaken by the main works contractors (MWCs) within their respective areas of the project. Following completion of construction works, operational monitoring is required for a period for assurance purposes. The operational groundwater monitoring has different requirements to that undertaken during the construction phase. During construction the requirements focused on monitoring and managing the effects of construction activity, during operation the requirements relate to monitoring and managing the effects of the operation of the tunnel by monitoring for sewage indicators. The responsibility for groundwater monitoring transfers from the MWCs to Tideway at completion of the works. Tideway is therefore seeking a Contractor to provide groundwater monitoring services across the specified sites for an initial period of 3 years and maximum term of 10 years. The duration of the requirement is currently estimated at 5 years however it will ultimately be determined by analysis of the groundwater monitoring and sufficient assurance that the tunnel is operating appropriately. The services will include, but not limited to : • Monitor groundwater quality by sampling existing boreholes along the tunnel route and have the samples analysed against a list of water quality tests (which will be specified by Tideway). • For clarity the services do not cover groundwater monitoring via boreholes for construction but will be for tunnel operational monitoring to ensure there is no pollution to the surrounding groundwater. • For reference, the tunnel will be transporting ‘storm sewage’ flows along it, not sewage. This is important as it will be diluted sewage. • The boreholes are pre-existing having been drilled around 5-10 years ago. Services or ability relating to maintaining the boreholes themselves may be required. • The monitoring sites are located mostly in the East area and the eastern half of the Central area of the project. • We would expect sampling to occur at regular periods. At the moment that is likely to be every 3 months, however this is subject to confirmation. • Services will include laboratory testing of extracted water samples for stated contaminands and provision of results to Tideway. • There may be liaison with landowners required to access some of the boreholes.