Firewater Risk Assessments explained

Firewater Risks Assessments explained

A Firewater Risk Assessment (FWRA) is an evaluation of the predicted volume and composition of firewater generated in the event of a fire occurring on-site.

Firewater, in this context, is defined as the liquid which arises from water, foam, rainwater or other substances that have been used for fire-fighting purposes. Firewater is likely to contain polluting matter having come into contact with the products of combustion. It typically contains high concentrations of substances which are harmful and in some cases toxic to the aquatic environment.

The Environmental Protection Agency (EPA) recently published an updated guidance note on Retention Requirements for Firewater Run-off, ( replacing the previous guidance note from 1995.

What type of facilities require Firewater Retention?

Many industrial facilities exhibit a heightened potential to cause adverse environmental impacts due to the storage of chemicals and other polluting substances on-site. In the event of a fire, the loss of containment of such harmful substances can lead to contamination. An adequate firewater retention system is therefore required to prevent uncontrolled releases of runoff into the surrounding environment. Sites which operate under an EPA Industrial Emissions Licence or Waste Licence typically require firewater runoff retention. Examples include:

  • Chemical processing
  • Fuel distillation and refinement
  • Pharmaceuticals
  • Waste transfer stations
  • Energy production
  • Food and drink production
What are the key changes made from the previous guidelines?

Firewater Retention Qualifying Criteria now focus on the following:

  • Environmentally Hazardous Substance Storage Thresholds – Any substance bearing the ‘Dangerous for the Environment’ Hazard symbol as shown, is taken into consideration in the formulation of the storage thresholds. These thresholds vary according to the potency of a substance.
  • Environmental Receptor Criteria – sites with a direct storm water discharge to sensitive water bodies.

Consequence rather than likelihood. The requirements under the new guidance culminate in a risk matrix which positions the Significance of a Fire Event (S) against the Environmental Hazard Potential (H) to calculate the Overall Firewater Runoff Risk (R). If any level of environmental risk is determined, the operator is obliged to implement minimum firewater retention measures.

Calculation of firewater retention capacity can now be completed according to the characteristics of different areas of the site. For example, there is a capacity calculation specific to warehouse space and a calculation specific to tank farms. If sufficient fire mitigation measures are put in place and it can be proven that fire hazard areas of the site pose no danger of fire spreading to other areas, calculations can be made for these areas in isolation.  This results in a reduction in the amount of firewater retention capacity required at the site. The EPA has also provided a Firewater Risk Assessment (FWRA) tool to be completed during the risk assessment.

Bunds* cannot be used exclusively to provide firewater retention unless the contents of the bunds are directly involved in the fire event.

Firewater Retention Containment

All firewater retention infrastructure MUST be automatically activated in conjunction with the site’s fire alarm and must be rendered impermeable with appropriate lining material. The types of retention infrastructure generally consist of:

  • Dedicated Firewater Retention Ponds
  • Lagoons or Storm Water Attenuation Ponds
  • Tanks
  • Bunds*
  • Drainage System
Why ORS?

ORS is a multi-disciplinary building consultancy firm.  The Environmental Team has a proven track record in the management of EPA licence requirements. Our dedicated Fire, Health and Safety Management and Environmental Teams have extensive experience in the following areas:

  • Comprehensive Desktop Studies.
  • Emergency response to fire incidents.
  • Site drainage management and design of retention infrastructure.
  • Best practice containment.
  • Fire, dangerous substances, and environmental risk assessments.
  • Integrity testing of tanks and bunds.
  • Environmental Liability Risk Assessments (ELRA).

If you require a Firewater Risk Assessment at your facility contact Alan Kiernan today at

Block A, Marlinstown
Business Park, Mullingar,
Co.Westmeath, Ireland.
N91 W5NN

Pembr, 127 Baggot Street Lower, Baggotrath Dublin, D02 F634

Eyre Square,
H91 HY51

Office 4, Spencer House,
High Road, Letterkenny,
Co. Donegal,
Ireland. F92 PX8N

Republic of Work,
12 S Mall,
Centre, Cork,
T12 RD43

ORS has satellite offices in Newry and Maynooth.

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