California ICC UST Inspector Practice Exam 2025 – Your All-In-One Guide to Exam Success!

The requirement stating that the interstitial space shall be maintained at ambient pressure is not applicable for new underground storage tank systems installed after July 1, 2004. Instead, industry standards and regulations typically allow for the interstitial space to be managed differently depending on the specific design and monitoring systems in place.

In the context of underground storage tanks (USTs), the interstitial space is the area between the primary containment (the tank itself) and the secondary containment (such as a double-walled tank). For new systems, the regulations focus on ensuring that both primary and secondary containment measures are robust to prevent leaks and spills, but they do not mandate that the interstitial space must always be maintained at ambient pressure.

Instead, the other options focus on critical safety and environmental protection measures that are essential in ensuring that new UST systems do not pose a risk of leakages or spills, which is a major concern given the potential environmental impact of fuel and hazardous materials stored in underground tanks. These include requirements for product tight primary containment, secondary containment that prevents water intrusion, and spill prevention equipment—all of which are necessary to protect groundwater and soil from contamination.