Neyland Outfall Cleaning and Check Valve Installation
Client: Envolve Infrastructure
Asset Owner: Dŵr Cymru Welsh Water
Location: Neyland, Pembrokeshire
Programme: Approximately nine days
Services: Outfall cleaning, CCTV survey, marine access and valve installation
Project Overview
Kaymac Marine & Civil Engineering was appointed by Envolve Infrastructure to clean and inspect an existing Dŵr Cymru Welsh Water outfall at Neyland, Pembrokeshire, before installing a new CheckFlex duckbill check valve.
The project required a carefully coordinated approach involving simultaneous onshore and offshore operations, specialist jetting equipment, vessel-based access and tightly controlled tidal working windows.
Scope of Works
Kaymac’s works included:
- Establishing safe access to the onshore manhole chamber
- Mobilising personnel, plant and equipment by multicat vessel from Pembroke Dock
- Surveying the offshore outlet and existing concrete surround
- Creating a temporary sump at the outlet to manage sediment and debris
- Cleaning the pipeline from both the onshore and offshore ends using specialist high-pressure jetting equipment
- Flushing the pipeline with fresh water following each jetting operation
- Undertaking a CCTV survey from the onshore chamber through to the offshore outlet
- Preparing the existing outlet and concrete surround
- Installing a new CheckFlex duckbill check valve using resin-fixed M24 anchors
- Reinstating the access area and completing the final site clearance
Working Around the Tides
Access to the offshore outlet was one of the project’s principal challenges.
Kaymac coordinated the work around a low spring tidal period, using the Wiltango multicat vessel to transport personnel, equipment and materials from Pembroke Dock. The vessel was positioned alongside the outlet on the falling tide, reducing the distance that specialist equipment needed to be transferred across the foreshore.
Weather conditions, tidal levels and flows through the outfall were monitored throughout the works. The cleaning operation was completed progressively over several suitable tidal windows, with Kaymac’s onshore and offshore teams working together to clear the pipeline safely and efficiently.
Coordinated Pipeline Cleaning
Specialist jetting equipment was deployed at both ends of the outfall.
From the offshore side, Kaymac created a temporary sump and installed pumping equipment to control and remove loosened material. The pipeline was then jetted towards the onshore chamber.
At the same time, a second team worked from the onshore chamber towards the outlet. Close communication between both teams was essential to coordinate the operation and prevent the jetting equipment from becoming entangled within the pipe.
Once cleaning was complete, the line was flushed and inspected using CCTV equipment to verify its internal condition and confirm that remaining debris and obstructions had been removed.
Installing the New Check Valve
Following acceptance of the cleaned pipeline and CCTV survey, Kaymac prepared the offshore outlet for the new CheckFlex valve.
The end of the existing pipe was cut back flush with the surrounding concrete, and the fixing surface was thoroughly cleaned. The valve was then lifted into position and secured to the existing structure using resin-fixed anchors installed to the approved design depth.
The new duckbill valve provides a simple, robust means of allowing discharge through the outfall while helping to prevent seawater, debris and marine material from entering the pipeline.
Managing a Sensitive Marine Environment
- Using biodegradable hydraulic oil where practicable
- Cleaning plant before and after working within the marine environment
- Positioning pumps and small plant within suitable containment
- Carrying spill-response equipment aboard the vessel
- Refuelling only within the controlled dockside area
- Using fresh water for the final pipeline flush
Key Project Challenges
- Unknown internal condition of the buried outfall
- Suspected obstruction within the pipeline
- Restricted access to both ends of the asset
- Offshore operations governed by tides, weather and discharge flows
- Coordination of simultaneous onshore and offshore jetting
- Working around an operational wastewater asset
- Confined-space controls at the onshore chamber
- Installation of a new valve onto an existing marine structure
Specialist Marine Infrastructure Delivery
The Neyland project demonstrates Kaymac’s ability to combine specialist marine access, confined-space capability, pipeline cleaning, asset inspection and precision installation within one coordinated package.
