Which document is essential for ensuring safety compliance before excavation?

The essential document for ensuring safety compliance before excavation is the Texas One Call notification. This notification system is designed to protect underground utility lines, such as gas, water, and electricity, from accidental damage during excavation work. Before any digging or excavation activities commence, it is crucial for contractors and workers to notify Texas One Call, which will then notify the appropriate utility companies to mark the location of their lines. This helps prevent serious accidents that could result from striking these utilities, ensuring not only compliance with safety regulations but also safeguarding the workforce and surrounding environment.

The other options, while important in their contexts, do not directly address the critical need to prevent utility strikes during excavation. An excavation permit is necessary for legal excavation but does not inform about below-ground hazards. A safety manual reference provides guidelines but is not a proactive measure for identifying existing underground utilities. Project blueprints may show where structures are located but typically do not indicate the presence of underground utilities, making them insufficient for ensuring safety compliance in this scenario.