What must be onsite and available when constructing an excavation protection system?

Having the manufacturer's data onsite and available during the construction of an excavation protection system is essential for several reasons. This data typically includes critical information about the materials and components used in the system, such as specifications for installation, load capacities, safety guidelines, and maintenance recommendations. This information ensures that the system is erected according to the manufacturer's standards, which is vital for safety and compliance with regulations.

Additionally, the manufacturer's data helps construction crews understand the limitations and proper usage of the protection system. With accurate information, workers can implement the system correctly, which reduces the risk of accidents and ensures that the excavation is safely protected against potential collapses or hazards.

In the context of the other choices, while construction plans provide an overview of the project and inspection reports are important for ensuring ongoing safety and compliance with regulations, the manufacturer's data is specifically tailored to the materials and systems being used, making it crucial for the immediate and correct execution of the excavation protection system. A materials list, on its own, does not provide the necessary guidelines or specifications needed for safe construction practices.