Combined Foul and Storm Sewer Connection – Clapham, South London

As part of essential infrastructure upgrades in Clapham, South London, a combined foul and stormwater sewer connection was successfully completed. The project involved several complex civil engineering operations designed to connect new drainage systems to Thames Water’s existing network while maintaining site safety and minimising disruption.

Scope of Works:

• Excavation of Shaft:
  A vertical shaft measuring 4 metres in depth was excavated on-site to facilitate access to the existing sewer infrastructure. This shaft served as the primary entry point for subsequent tunneling and pipe installation activities.
• Timber Heading Construction:
  A timber heading approximately 10 metres in length was carefully driven from the shaft location into an existing Thames Water manhole. This traditional method of hand-mined tunneling was chosen due to its precision and suitability in confined urban environments where vibration and surface disruption needed to be minimised.
• Pipe Installation and Backfilling:
  New 150mm diameter sewer pipes were installed along the timber heading to form the new combined connection. Upon completion of pipe-laying, the heading was backfilled using dry lean concrete to provide structural stability and protection for the pipework.
• Installation of Backdrops:
  Three new backdrops were installed within the newly constructed manhole on-site. These backdrops are essential hydraulic features that manage the vertical transition of wastewater from higher to lower levels, reducing flow velocity and minimising the risk of turbulence or structural damage within the manhole.

This project required careful coordination with Thames Water, adherence to health and safety standards, and precise execution to ensure the successful integration of the new sewer infrastructure into the existing network.