HomeMy WebLinkAboutMEMO Water Supply requirements 3501 Fall River RdMEMORANDUM
To:Jackie Halburnt,Asst.Town Administrator
CC:Will Birchfield,Chief Building Official
From:Fire Chief Scott Dorman
Date:August 1,2007
Subject:Water Supply requirements for Della Terra Development at 3501 Fall
River Rd.
The calculation to determine the required storage of water for fire protection is based on
Appendix B Section B103 of the International Fire Code and NFPA 1142.Appendix B
Table B 105.1 states that the minimum required fire flow for a Type V-B building that is
22,000 sq ft is 4,000 gallons per minute (GPM)for duration of 4 hours.Section B 105.2
has an exception allowing for a reduction of up to 75%of the required fire flow if the
building is provided with an automatic sprinkler system,but shall not be less than 1500
GPM.
4,000 x 75%=3,000 GPM reduction which is <the 1500 GPM minimum requirement.
Therefore,1,500 GPM would be required for 4 hours (the total water stored on site
required to suppress a fire).
1,500 GPM x 4 hours =360,000 gallons of water storage
Because the Estes Park Volunteer Fire Department has the capability to deliver
approximately *1,500 GPM of water through a tender shuttle system,this storage
requirement would be reduced to the time it would take to have the shuttle system
operational.The estimated time to set up an adequate shuttle system is 30 mm,
1,500 GPM x 30 mm =45,000 gallons of water storage
NFPA 1142 Standard on Water Supplies for Suburban and Rural Fire Fighting,has a
different method to determine required fire flow,it is based on the following formula:
Structures without Exposure Hazards
Minimum water supply total volume of structure/occupancy hazard classification
number x construction classification number
The minimum water supply cannot be less than 2,000 gallons.
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Structures with Exposure Hazards-
Minimum water supply =total volume of the structure/occupancy hazard classification
number x construction classification number x 1.5
The minimum water supply cannot be less than 3,000 gallons.
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For a 2-story building totaling 22,000 sq ft the calculation would be as follows:
22,000/2 =11,000 sq ft per floor
11,000 sq ft x 20 ft (vertical ht)=220,000 cubic ft of volume
=220,000/7 (occupancy hazard classification per NFPA 1142 section 5.2.5)
31,429 x 1.5 (construction classification per NFPA 1142 section 6.2.6)
=47,144 gallons of storage (without exposures)
47,144 x 1.5 70,716 gallons (with exposures)
NFPA 1142,Section 7.4.1 allows for the authority having jurisdiction to waive the water
supply required by the standard if the structure is protected by an approved automatic
sprinkler system.Due to the travel distance from the Dannels Fire Station and exposure
to the forest from a fire in this building,I would not be in favor of waiving the water
supply requirements.
Therefore,based on the above requirements for fire flow,a building of this size that is
equipped with an approved automatic sprinkler system installed to NFPA 13,would
require a minimum of 47,144 gallons of water,if there are no exposures within 100 ft.If
there are exposures within 100 ft.then the required amount of stored water would be
70,716 gallons.Additionally,if this building is not equipped with an approved automatic
sprinkler system,then the required water storage would be 360,000 gallons.
*Estimated amount only,a water shuttle calculation would be required to determine the
actual amount of water in GPM that could be delivered to this location within 30 mm.
In addition to the required storage a viable way of pressurizing and accessing the water
would be needed,in example,a fire pump and hydrant may be required.
Please let me know if you have any questions.
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