Client / Site: Utility Provider – South-East Wastewater Network, UK

The Challenge

A 450mm sluice valve had seized completely in a submerged pipe chamber at a live foul water pumping station, requiring immediate removal and replacement.

This contaminated water diving operation presented multiple complex challenges:

• Zero visibility conditions – divers working completely blind in contaminated water
• High biological contamination – exposure to pathogens and industrial chemicals
• Live sewage inflow – continuous flow from domestic and industrial sources during the operation
• Limited access – restricted working space in a confined underground chamber
• Environmental protection – requirement for zero discharge of contaminants
• Operational continuity – minimum downtime essential for network operations

The client required the seized valve removed with full water containment and zero discharge of contaminants during the work.

Our Response

Dagger Diving Services deployed our specialist contaminated water diving team, who operated in full surface-supplied air with positive-pressure drysuits, creating a sealed barrier against contamination. Every team member was medically cleared, vaccinated, and briefed under our confined-space plus biological hazard protocol, ensuring full compliance with HSE Diving at Work Regulations and COSHH controls.

Contaminated Environment Equipment

• Positive-pressure drysuits with sealed communications – preventing any contamination ingress
• Full decontamination unit with two-stage disinfection process
• Environmental isolation using double-gate valve lockout systems
• Hydraulic tools and burn-safe impact wrenches – preventing sparks in potentially explosive atmospheres
• Suction and isolation barriers – ensuring zero downstream discharge

Zero-Visibility Operations Working in complete darkness with zero visibility, our team relied on tactile expertise and intrinsically safe inspection cameras for live video verification. Every movement was carefully coordinated through sealed communication systems.

Comprehensive Safety Protocols A secondary diver maintained standby throughout the operation with independent gas supply and egress tether. Our environmental isolation systems prevented any contamination from escaping the designated containment zone.

Precision Engineering The operation involved removing heavily corroded fasteners, rigging the seized valve for hoist extraction, and installing a replacement blanking flange – all performed underwater in a live sewage environment.

The Outcome

Mission Critical Success – Zero Environmental Impact

Our contaminated water diving operation delivered exactly what the client needed: complete valve removal with perfect environmental protection and zero downtime impact.

Environmental Excellence:

• Zero fluid release outside the designated containment zone
• 100% environmental protection compliance certified by client
• Full biological decontamination certification issued
• No contamination incidents throughout the operation

Operational Success:

• 450mm sluice valve successfully removed and replaced with blanking flange
• Site cleared for normal operation within 12 hours
• Zero exposure events – perfect safety record maintained
• Zero asset damage – infrastructure protected throughout

Safety Achievement:

• 4 dives completed in high-risk contaminated environment
• 0 injuries or incidents – flawless safety execution
• Full decontamination protocol implemented for all equipment
• Equipment quarantine procedures executed to prevent cross-contamination

Regulatory Compliance: All contaminated water diving work was delivered under strict compliance with HSE Diving at Work Regulations, COSHH, ISO 45001, and our internal Contaminated Environment Protocol. Full biological hazard planning, vaccination compliance, environmental protection, and equipment quarantine procedures were implemented and certified.

Client Impact: The utility provider achieved successful valve replacement while maintaining continuous service. Our precision contaminated water diving operation delivered the required environmental protection standards and operational continuity.

Facing a contaminated environment diving challenge? Dagger Diving Services specializes in contaminated water diving operations with uncompromising environmental protection and safety standards. Contact us today to discuss your contaminated environment diving requirements.