Deep Sewer Repair and Infrastructure Restoration – Kent

Background and Initial Investigation

The repair was initiated after a resident reported persistent flow issues, prompting a CCTV inspection of the line. The footage revealed multiple fractures along the pipe, with a complete collapse at one section. The sewer, constructed from 300mm vitrified clay pipework, showed deterioration typical of legacy infrastructure under variable loading and ground movement.

Due to the nature of the damage and the risks posed to service continuity and local ground stability, Cappagh Browne, working alongside our delivery partners, was instructed by Southern Water to carry out a full excavation to expose the affected area and facilitate both lining and pipe replacement where necessary.

Excavation and Access

The excavation measured approximately 3.1m by 3.1m in plan and was taken down to a final depth of 4 metres. The first 3 metres were excavated mechanically using an 8-tonne excavator. However, due to constraints imposed by overhead lines and utility infrastructure, the final metre of excavation was carried out manually using traditional hand-dig methods to maintain safe clearances and protect service routes.

Temporary works were implemented using a combination of four-metre trench sheets and manhole brace shoring systems, designed in accordance with current health and safety and temporary works standards. A davit arm and tripod system were installed at the access point, enabling safe personnel entry and egress, supported by ladder access and edge protection to prevent fall risks.

Damage Assessment and Pipe Rehabilitation

Once uncovered, it became evident that the damage extended both upstream and downstream of the original collapse. Cappagh Browne undertook the full removal and replacement of the collapsed pipe section. The new installation was a like-for-like replacement using 300mm vitrified clay pipework, bends, and fittings. Band seal flexible couplings were utilised to join the new sections to the existing infrastructure, accommodating any minor angular deflections and ensuring watertight integrity.

Health, Safety and Environmental Considerations

The site was operated under Cappagh Browne’s comprehensive health and safety protocols. These included:

• CAT and Genny scanning prior to excavation
• Trial holes to confirm and mark the location of three water and two gas service feeds
• A designated safety exclusion zone
• Full edge protection and barrier systems
• Working at height mitigation, including edge protection and access/egress using a davit arm and harness.
• Atmosphere testing, using our MSA Safety Altair io4 Multigas Detector

No service strikes occurred, and the excavation proceeded without environmental incidents.

Outcome

The project restored full operational capacity to a damaged section of the local sewer network while maintaining safety, service continuity, and environmental protection throughout. Effective coordination enabled the successful delivery of both traditional excavation works and modern trenchless rehabilitation techniques.

This case study highlights Cappagh Browne’s ability to manage technically demanding excavation and repair projects in urban environments with multiple service constraints, adhering to best practice and delivering reliable outcomes for essential infrastructure.