Which of the following is classified as an underground obstruction?

Old septic systems are classified as underground obstructions because they are typically buried beneath the surface and can interfere with excavation or construction activities. These systems are designed to hold and treat wastewater, and their presence needs to be properly accounted for to avoid damage or contamination during digging or site development. Not recognizing their location could pose safety risks, as well as environmental hazards.

In contrast, overhead power lines, while hazardous, are not underground and therefore do not fit the classification of an underground obstruction. Construction debris is commonly found above ground and is not necessarily an obstruction located below the surface. Weather-related hazards are transient conditions related to the environment, such as rain or high winds, and do not constitute a physical obstruction in the ground itself. Understanding these distinctions is crucial for ensuring safety and compliance during construction operations.