California ICC UST Inspector Practice Exam

Which of the following statements about vadose zone monitoring is incorrect?

1. Vadose zone monitoring cannot be used as the sole monitoring method if the groundwater is less than 10 feet below the tank.

2. Vadose zone monitoring shall be conducted continuously.

3. Background contamination shall not interfere with the method used to detect releases.

4. The monitoring points should be located outside of the backfill, if possible.

The correct answer is: The monitoring points should be located outside of the backfill, if possible.

The chosen answer, stating that "The monitoring points should be located outside of the backfill, if possible," is not accurate in the context of vadose zone monitoring practices. In fact, vadose zone monitoring often necessitates that monitoring points, such as access ports or wells, are strategically placed within the backfill to effectively detect the presence of contaminants as they migrate from the tank area through the backfill and into the unsaturated zone. When monitoring points are positioned within the backfill, it improves the chances of identifying leaks or releases before they reach the groundwater layer. Monitoring conducted from outside the backfill could reduce the monitoring effectiveness due to potential dilution or misinterpretation of contaminant concentrations. The other statements regarding vadose zone monitoring align with the standard practices and regulations in place. For instance, continuous monitoring is recommended to ensure prompt identification of any potential leaks, and considerations around background contamination underscore the importance of ensuring that any findings are specific to the tank under review, without influence from pre-existing conditions. Additionally, monitoring proximity to the tank influences the reliability and accuracy of the detection methods being employed.