Certified Fire Protection Specialist (CFPS) — Question 40

While performing a fire hazard survey on a structure in a non-hydrant area you need to estimate the water supply capacity of a stream adjacent to the structure as a possible drafting site. The stream is 5' wide and the average depth is 12". You observe that a leaf floating on the surface travels 10 feet in 30 seconds from the current. What is the approximate flow rate in gallons per minute (GPM) of the stream?

Answer options

• A. 250 GPM (946 LPM)
• B. 500 GPM (1,892 LPM)
• C. 750 GPM (2,839 LPM)
• D. 1,000 GPM (3,785 LPM)

Correct answer: D

Explanation

To determine the flow rate, you can calculate the velocity of the stream and then use the cross-sectional area to find the GPM. The width of the stream is 5 feet and the depth is 1 foot (12 inches), giving an area of 5 square feet. The velocity is 10 feet in 30 seconds, or 0.33 feet per second. The flow rate is approximately 1,000 GPM, while the other options are lower estimates based on different calculations or assumptions.