Sizing of storm building drains and sewers is primarily based on the surface area to be drained and what other critical factor?

Question: Sizing of storm building drains and sewers is primarily based on the surface area to be drained and what other critical factor?

Answer options:

• The anticipated number of extreme weather events per year ✅ The local 15-minute rainfall intensity value
• The total length of the storm sewer to the municipal connection
• The depth of the municipal storm sewer

Correct answer: The local 15-minute rainfall intensity value

Explanation: The National Plumbing Code and engineering standards use local meteorological data for sizing storm drainage systems. The critical value is the maximum rainfall intensity expected during a 15-minute period, which represents the highest short-term load the system must handle.