runoff of firewater

It depends. NFPA 30 requires a means of containment and diking from a petroleum storage tank containing Class I, II or III liquid. The 2021 International Fire Code and NFPA 400, in certain cases, requires the design of an outdoor secondary containment to contain a specified volume liquid based on the largest container or tank + the rainfall from a 24 hour/25 year storm. My experience that a specific requirement for the containment of runoff from manual firefighting operations is not required.

If one was to evaluate the size of leaks or spills inside containment structures, one will find that the leak sources are not catastrophic failures, especially with aboveground storage tanks. For containers and portable tanks, yes, catastrophic failures occur under fire conditions. But, depending on the level of fire protection, I've never witnessed a containment overflow during firefighting operations. My experience is the model codes have a conservative design approach and combined with other regulatory requirements, the potential for overflow of a containment is low during firefighting operations.