Final answer:
The depth at which an excavation needs attention from a registered professional engineer is commonly considered to be 30 feet.
Step-by-step explanation:
The depth at which an excavation needs attention from a registered professional engineer can vary depending on the specific project and location. However, in general, a depth of 30 feet is commonly considered to be the threshold where the involvement of a professional engineer is necessary.
Excavations beyond this depth may present increased risks and require specialized knowledge and expertise to ensure safety. Professional engineers have the training and experience to assess the stability of the excavation, design support systems if required, and ensure compliance with applicable regulations and standards.
It's important to note that local regulations and project-specific requirements may dictate different thresholds, so it's always best to consult with a local authority or professional engineer in your area for specific guidance.