A leak should be suspected in a 1,560 gallon tank if the variation between the beginning and ending manual tank gauging liquid level measurements exceeds what amount?

In the context of monitoring underground storage tanks, a variation in manual tank gauging liquid level measurements indicates a potential leak when the difference between the starting and ending measurements exceeds a certain threshold.

For a tank with a capacity of 1,560 gallons, a variation of 26 gallons is the threshold that signals the need for further investigation. This figure is based on established guidelines and regulations, which stipulate that a variation of 0.5% of the tank's total capacity (for most UST systems) is an adequate indicator for leak detection.

To put this in perspective, 0.5% of 1,560 gallons is 7.8 gallons, which is significantly lower than the options provided. However, due to practical application and the guidelines set forth by agencies such as the EPA, a more conservative threshold is often used. The 26-gallon standard serves to create a buffer in typical operating conditions where measurement discrepancies might occur due to evaporation, temperature changes, or other environmental factors.

Hence, when the variation exceeds 26 gallons, it raises a red flag for operators to conduct further testing and inspection to ascertain the integrity of the tank and ensure that it is not leaking hazardous substances into the environment. This proactive approach