The fire code regulations for tanks in underground areas and connected piping systems were adopted by the California Building Standards Commission (CBSC) in August 2017 and became effective July 1, 2018.  The full definition of a tank in an underground area per APSA also became effective July 1, 2018.

You may access the fire code by visiting the California Building Standards Commission website.  Select Part 9 of the California Code of Regulations, Title 24.