Which of the following is a sign that a UST may have a leak?

The presence of stains or odors around the tank area is a clear indication that a UST (Underground Storage Tank) may have a leak. Stains could appear on the ground or nearby surfaces as fuel or other substances escape from the tank, while odors can result from volatile organic compounds or other hazardous materials being released. Both of these signs suggest that the integrity of the tank is compromised, potentially leading to contamination of soil and groundwater.

In contrast, increased fuel efficiency is not related to the condition of the tank but rather pertains to how well the vehicle or equipment is operating. Lower than average maintenance costs do not directly indicate the status of the UST; they may suggest good practices or efficient operations without revealing any potential leaks. Regular inspections that show no issues would imply that there are no leaks at that time, but they do not account for leaks occurring after an inspection or those that may not be visible during routine checks. Thus, signs like stains or odors are critical red flags that demand immediate attention in the management of UST systems.