1. #1
    Dalmatian90
    Firehouse.com Guest

    Cool ISO question...Needed Fire Flow by area.

    Larry (or anyone...) I have a question on the ISO rating I can't find specifically addressed in your guide or the FSRS itself...

    We're a Class 5 within the hydranted district which covers our central village and two years ago was extended which helped a lot, extending the 5 to what was the 2nd highest fire flow in the rural area off the ISO batch list...and at the same time the adjacent largest NFF was sprinklered dropping it from 5,000gpm to 500gpm (gotta love them sprinklers!).

    Our rural area is still a 9, mainly since we haven't gone for a formal re-grading yet.

    Now, in the rural "9" area we have the following Needed Fire Flows off the ISO Batch List:
    3500gpm
    3500gpm
    1750gpm
    1750gpm
    750gpm
    750gpm
    750gpm
    500gpm

    My understanding is that the "Community Fire Flow" they look for is the 5th highest NFF -- in the above, that would be 750gpm. Is that correct?

    If you achieve the 750gpm, does that give you maximum credit for water supply?

    Can the "rural" area which would be supplied by tanker shuttles off the hydrant system for purpose of ISO rating be graded seperately from the "hydrant" area? Alone, the hydranted area also has a 5th highest flow of 750gpm...but the two areas combined would see the 5th highest flow jump to 1,750gpm.

    Now the 1,750 isn't insurmountable either, but it would require two static water supplies in town be certified by an engineer to augment the hydrant system. With those two water holes added, we can achieve the flows for all our batch list properties under ISO rules except the two 3500gpm flows -- one we can do 2250gpm, the other only 750gpm. But if 750gpm as the Community Fire Flow for the rural area is all ISO would hold us too, we can do that off the hydrants without worrying about static supplies.

    Hope I was clear enough...ask questions if I wasn't!
    Matt

  2. #2
    LHS'
    Firehouse.com Guest

    Post



    .Now, in the rural "9" area we have the following Needed Fire Flows off the ISO
    Batch List:
    3500gpm
    3500gpm
    1750gpm
    1750gpm
    750gpm
    750gpm
    750gpm
    500gpm

    My understanding is that the "Community Fire Flow" they look for is the 5th
    highest NFF -- in the above, that would be 750gpm. Is that correct? .

    They probably will require a fire flow area wide of at least 1000 gpm.

    .. If you achieve the 750gpm, does that give you maximum credit for water supply?

    No, 750 gpm demonstrated would give only 15.8 points out of 35 points for water. That is because your needed fire flows equal 13,250 and you can only provide 7450 times 8 locations or 6000 gpm or 45%. If you can flow more at any given property you'll gain point, flow less you'll lose points. Scoring only 15 points leaves you in quite a divergence situation as well. It quite possible they will find building off the batch list to add to the list.

    .. Can the "rural" area which would be supplied by tanker shuttles off the hydrant
    system for purpose of ISO rating be graded seperately from the "hydrant" area?


    Not likely

    Alone, the hydranted area also has a 5th highest flow of 750gpm...but the two
    areas combined would see the 5th highest flow jump to 1,750gpm.

    That will be the area wide fire flow to determine the number of firefighters and apparatus.

  3. #3
    Dalmatian90
    Firehouse.com Guest

    Post

    Thanks...I knew that before on aggregating the flows...was just having the mother of all brain farts last night and forgot it.

    At least ISO has done a pretty good job identifying the properties outside of the hydrant district -- within the hydranted area, they are missing quite a few, but almost all would be 1500 or under flows the hydrants can do. Now why do all the high flow properties have to be pushing 3 miles out from the hydrant system

    Using that formula on our area, worst case (not using static supplies) is 49%...certifying those two static supplies will bring us up to 70%...and the great irony is 21% points of the gap is because of a single facility at the edge of our district and in an area with no good static water sources close by is owned by the person who has been our Fire Company chairman for most of the last decade.

    Actually those 21% points might be doable through a major rebuild of a fire pond that has silted in over the years...and the ISO value may be the arguement that can be used to twist Inland Wetlands into relenting and allowing it to be excavated back out to a proper size if an Engineer says it can be certified then...hmmmm.



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