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Firewater Retention and Uncontaminated Stormwater Runoff


The EPA’s Draft Guidance on firewater Retention Facilities dates back to 1995 and has never been finalised. Many IPPC and Waste licensed facilities have been forced to build excessively large firewater retention facilities, mainly due to the requirement in the guidance to retain vast amounts of stormwater. In many cases 90% of the capacity of firewater retention facilities is required for the retention of stormwater, as the Guidance wants a 24 h 20 year return period storm retained. So before you go building an Olympic sized swimming pool at your facility please take note of the points below;

- where possible separate stormwater runoff from large hard standing areas, such as car parks, from stormwater runoff associated with buildings. In that way you will substantially reduce the amount of stormwater to be retained in the event of a fire in the building.

- for a number of years the EPA has accepted calculations based on stormwater from a 1 h as opposed to a 24h 20 year return period.

- assuming you have an automatic sprinkler system, determine how long it will take to extinguish a fire and use that time period in your calculations.

- where potential fires can be compartmentalised, ensure that this is reflected in the firewater calculations.