Southgate Effluent Outfall Repair

August 2025

Client: Dŵr Cymru/Welsh Water
Location: Southgate, South Wales

Background

The Southgate Final Effluent Outfall pipe, located on the rugged Gower Peninsula near Swansea, plays a vital role in safely discharging treated wastewater into the sea from Dŵr Cymru Welsh Water’s infrastructure. Over time, the 230-metre-long outfall section had become partially obstructed, damaged and structurally compromised, with several sections exhibiting significant wear, leaking and damage due to exposure to harsh coastal conditions.

The outfall is situated in a remote, environmentally sensitive location, accessible only via steep coastal footpaths or by sea. Regular exposure to tidal flows and large swells had further complicated the maintenance of the asset. Due to its proximity to popular walking and rock-climbing areas, the works needed to be delivered with minimal disruption to the public and the surrounding environment.

In 2025, Kaymac Marine & Civil Engineering Ltd. was commissioned to deliver a comprehensive repair and rehabilitation project that would extend the service life of the outfall, ensuring its continued performance and compliance with environmental standards.

Key Challenges

Logistical Constraints:
The remote site offered no road access for heavy plant or material deliveries. All materials, equipment, and personnel had to be transported either by foot down steep coastal terrain or by sea using a landing craft and small workboats.
Tidal and Weather Dependency:
Due to large swell and tidal restrictions, operations had to be planned meticulously around suitable tidal windows to maximise safe working conditions.
Multi-phase Rehabilitation:
The 230m-long outfall section required sectional repair in six distinct areas, each with varying levels of structural degradation. Access to these sections was often restricted, requiring bespoke solutions for lining, concrete placement, and structural support.
Environmental Sensitivity:
The presence of asbestos cement pipework demanded specialist handling and removal in strict accordance with environmental and health and safety regulations.
Public Interface:
The site is located near a popular clifftop walk and rock-climbing destination. Safe segregation of work areas and ongoing communication with the public was essential to minimise impact on recreational users.
Subcontractor Coordination:
Specialist subcontractors were required for asbestos removal, CCTV surveying and installation of lining system. Effective collaboration and scheduling was critical to programme success.

The Solution

In May 2025, Kaymac successfully completed the Southgate Final Effluent Outfall repair project, overcoming the site’s logistical, environmental, and technical complexities through detailed planning, innovative working methods, and strong collaboration.

The project was delivered under an NEC3 ECC Option E contract and split into two phases:

Phase 1: Investigation and Survey
Initial activities included high-pressure jetting and CCTV inspection of the outfall. This revealed several blockages, collapsed pipe sections and damaged joints.

Phase 2: Repair and Rehabilitation
Following inspection, a comprehensive programme of structural repairs was implemented.

Works included:

Breakout and preparation of pipe at locations identified by the subcontractor and at corners;
High pressure jetting and CCTV of each section prior to lining;
Installation of SAERTEX-LINER® MULTI Type S+ for long-term structural integrity;
- CCTV following completion of the lining.
Patching of all broken out section and corners;
Placement of SoluForm bagwork and hand-laid 40N concrete to support and protect exposed pipework.

Due to logistical constraints, Kaymac utilised the MV Toplander landing craft and Dory workboats to deliver materials via the sea.

The presence of asbestos-containing materials required careful coordination with PAR, the licensed asbestos removal specialist. All materials were safely removed and disposed of in full compliance with statutory requirements.

Final reinstatement works included:

Installation of a 150mm WaStop non-return valve to prevent sand ingress;
Replacement of gaskets at all inspection hatches.

Outcome

The project exemplified Kaymac’s ability to:

Deliver critical infrastructure repairs in remote coastal environments;
Coordinate multi-agency teams and specialist subcontractors;
Adapt rapidly to environmental challenges and operational constraints.

Kaymac’s successful delivery of the Southgate Outfall project reaffirms its standing as a trusted provider of marine civil engineering solutions and demonstrates its commitment to infrastructure resilience, environmental responsibility and safe working practices in even the most complex of conditions.

📷 Image 1: MV Toplander
Landing Craft beached successfully with all plant, equipment and materials to undertake the works.

📷 Image 2: Outfall exposed and prepared for lining
The Outfall pipe was exposed in readiness for jetting and lining.

📷 Image 3: Pipework exposed and prepared for lining
Sections of AC Pipework was removed at suitable locations in readiness for jetting and lining.

📷 Image 4: Pipework exposed and prepared for lining
Change in direction between sections 1 & 2 exposed and broken out in readiness for jetting and lining.

📷 Image 5: Corner pipe section broken out by hand
Corner between section 2 & 3 broken out in readiness for jetting and lining.

📷 Image 6: Section 3 lining completed
Section 3 lined.

📷 Image 7: Concreting around newly installed liner
Concrete placed as protection of the new corner between sections 1 & 2.

📷 Image 8: WaStop valve installed at outfall
150mm Dia. WaStop fitted to the Outfall to prevent ingress from sand.

📷 Image 9: Kaymac’s Dory boats transporting materials to beach
Materials for the final works transported by Kaymac workboats.