Fire Water Risk Assessments: When You Need One and What's Involved

FPS Environmental | May 2026

If a serious fire breaks out on your site, the water used to put it out has to go somewhere. On most industrial, commercial and waste sites that water will not stay clean. It carries diesel, oils, solvents, ash, melted plastics, suspended solids and whatever else was burning or stored nearby. Without a plan, it leaves your site through surface water drains, ditches or hardstanding and ends up in the nearest watercourse.

A fire water risk assessment is the work that tells you how much contaminated water you would need to hold back, where you would hold it, and what would happen if you could not. It is also the document that regulators and insurers want to see.

This piece sets out when you need one, what it includes, and what regulators are looking for. It also draws on three recent FPSE projects to show how the work looks in practice.

When you need a fire water risk assessment

There are five main triggers.

Environmental permits and permit variations – If your site holds, or is applying for, an Environment Agency permit under the Environmental Permitting Regulations, the EA expects you to demonstrate fire water containment as part of your Fire Prevention Plan (FPP). This applies to most waste, recycling, composting, and certain treatment and storage sites. Permit improvement conditions often require an updated FPP and supporting fire water assessment, particularly after a permit variation or consolidation.

Planning conditions on new developments – Local authorities increasingly attach planning conditions requiring fire water containment to be designed in, especially on industrial estates, logistics hubs, manufacturing plants and energy facilities. This is the cheapest stage at which to address it because the drainage layout can still be changed.

Insurer requirements – Industrial insurers have tightened their stance after several high profile pollution incidents. Many now ask for a fire water risk assessment before renewal, particularly on COMAH and upper tier sites.

Material change of use or expansion – Adding storage, changing what you process, or extending hardstanding can all change the volume of fire water you might generate and the routes it can take. Existing assessments need to be revisited.

Following an incident – If you have had a fire, near miss or pollution event, the regulator will expect a review of containment arrangements as part of the closeout.

What the work involves

A fire water risk assessment is not a paperwork exercise. It is a quantitative piece of engineering supported by a structured site walkover. The output should give an operator confidence that, if the worst happens, contaminated water will be held on site and managed safely.

A robust assessment usually includes the following stages.

1. Site and process review
2. Fire load and water demand calculation
3. Drainage and pathway mapping
4. Containment options appraisal
5. Residual risk and emergency planning
6. Reporting and regulatory liaison.

Three examples from recent FPSE projects

The detail of every site differs. These three examples show how the same framework applies to very different operations.

A waste and composting operator in the West Midlands

The site held an EA environmental permit that had been varied and consolidated. The regulator issued improvement conditions which required an updated Fire Prevention Plan. We reviewed the existing permit, mapped the drainage, updated the FPP and prepared revised plans showing containment arrangements. The work then went through assessment and a response letter from the EA confirming the improvements were accepted.

A large manufacturing facility

This was a multi building production site where the existing surface water drainage discharged directly to a sensitive receiving watercourse. The brief was a full Fire Water Management Strategy covering all process buildings, external storage and the fuel yard. The work combined fire load calculations with a complete drainage survey, then a phased proposal for isolation valves on the main outfalls and a contained holding area for the highest risk yard. The strategy is now informing the site’s capital investment plan.

A smaller industrial unit on a Staffordshire estate.

This was a single building lease with a tight footprint and no obvious space for containment. The assessment had to draw on Environment Agency Product 4 historical flood and hydrological data to understand background conditions, then propose a phased low-cost approach combining sealed yard drainage, a remote isolation valve and an emergency response procedure. It is a useful reminder that fire water work is not only for large sites.

What good looks like

A strong fire water risk assessment does four things. It is grounded in current guidance, particularly CIRIA C736 and the Environment Agency’s firewater position statement. It is supported by a real site walkover and verified drainage information rather than relying on out of date drawings. It presents containment options, including their cost and operational implications, rather than recommending the most expensive solution by default. And it is written so that operations staff, designers, regulators and insurers can all use it.

If your assessment does not include drainage plans, calculations, a clear containment strategy and an emergency response section, it is unlikely to be accepted by the regulator.

Next steps

If any of the triggers earlier in this article apply to your site, the right time to act is before a permit deadline, planning condition or insurer renewal forces it. Early scoping is usually quick and tells you whether you are in a position to comply with what you have, or whether design and capital expenditure are needed.