Technical Assistance FPP

[Maz]

Good afternoon,

Please can anyone in operations assist me with my fire prevention planning information please:

Our site is 8000 squared meters, it is a new modern building Metal construction meets all building and safety requirements. 

Our waste management permit requires a calculation of volume of water that would be required to extinguish a fire on site.

We decommission airbag inflators (class 9 UN3268) in bespoke chamber approx 16ft x 16ft square brick construction, fire board ceiling and meets the MOD standards for air displacement and containment. There is nothing flammable inside the chamber and recent tests demonstrate the control measures are effective fully containing the fire.

If a breach were to occur the maximum waste volumes are as follows: 

• 250kg none deployed airbags ( each airbag contains approx 0.004 grams of explosive) 
• x3 tonnes Nylon bags
• 20 tonnes mixed metal
• 5 tonnes copper wire
• 2 tonnes hard mixed plastic
• 1.5 tonnes bailed fibre board boxes
• The waste is stored nylon bags / metal / plastics/ copper wire / fibre board.

The waste is separated by 1 meter distances and separated by UN specified metal stillages (NON FLAMMABLE) 

The waste volumes never exceed these limits due to licencing restrictions & waste disposal processes, these volumes are based on maximum and worst case scenario information. 

There are no live fire sources and the chamber uses a 12 volt electrical system to deliver electrical charge which is live only for the deployment of two second intervals.

Can anyone please help me understand how we would calculate the time and volume of water (estimated) to extinguish a fire in the conditions and the volume of water required please?

Thank you for you in advance for any assistance

Best wishes Maz

[Steve]

HI Maz,

This is an unusual question and I am struggling to understand why you need this. I have been in command of many fires in waste recycling facilities and have used the on-site fire plan, but can't even recall wanting, seeing or using any pre-determined hydraulic calculations. The last one I attended in June 2017 had a considerable fire which we spent a couple of days attending. At the peak of the fire, due to the amount of waste burning we were using two ground monitors (1500lpm each) two hand held branches (500lpm each) and an aerial monitor on and off (2000lpm).

Just a quick look at that shows you we needed in the region of 6000lpm, which required us to get a water relay going from a nearby open water source. The volume required massively overwhelmed the on-site fire main and local water supply. (I handed the problem to a bulk media tac adviser to solve for me). So, without knowing or assuming how much could be on fire, which would depend on atmospheric conditions, speed of intervention by the fire service. What percentage of what waste product were alight (heat release rates vary for different materials). Trying to work out your calculation for me, from a practical (operational) perspective is like trying to herd kittens it’s so variable.

I am sure there are fire engineers who can ‘model’ what you require based on a number of calculations and assumptions, but I don’t think anyone can give you an answer based on the variables I’ve mentioned.

So, if for example just your 2 tonnes of mixed plastic were on fire, I’d suggest we’d use two hand held branches flowing between 450-700lpm. So a flow rate of 1500lpm would be great. I’d also say we’d most likely have control of that if it were contained within about 10 minutes, so I could estimate that 15000l of water were required.

But what of it were the plastic and the copper wire, or the whole building, or it was windy and very warm? On occasions at a very large fire burning throughout the night we may require 10,000lpm, which is 600,000lph or 7.2m litres if we were firefighting for 12 hours. You see my difficulty in answering your question?

[Maz]

Hi Steve,

I really cannot thank you enough for returning to me on this matter and in answer to your question the Environment Agency or permitting department would appear to be a law onto themselves and the variables of questions is astounding. However I believe the point of the questioning for them lies in there understanding of actually the waste water containment from a fire and the 'potential' pollutant qualities onto land or water source. In anticipating the volume of water potentially I can calculate the requirements of spill kits containment of this. However I am of a mind that the fire brigade might take a dim view of me trying to deploy spill kits in a burning building???

However the information you have given me at least gives me the feedback I need to at least make an attempt at satisfying their requests and I am sincerely grateful for the time you have taken to respond for my request for assistance.

Best wishes Maz

[Steve]

No worries, happy to assist. Actually, We have a duty to consider water run off and early on. (In LFB) we carry out an assessment of water run off that is documented and the EA are informed. (although they don't often attend quickly if at all). We deployed spill kits along with trying to work with EA and Thames water to protect a SSSI following last weeks paint factory fire in NW London.