Yes, vacuum excavation can potentially cause damage to structures if not correctly handled and executed. While it is generally considered a safer and more precise method than traditional excavation techniques, risks are still involved. For instance, if the hydro or vacuum excavator is misused or used without proper precautions, it could lead to damage to underground utilities and structures. Furthermore, the high-pressure water or air used in the process could lead to erosion or instability in the surrounding soil, indirectly affecting nearby structures. Therefore, operators must be well trained and follow strict safety guidelines when performing vacuum excavation. 

The speed at which a vacuum trailer can excavate depends on several factors, including the type of soil, depth of excavation and the specific capabilities of the vacuum. However, vacuum excavator trailers are highly efficient. For example, hydro-vac trucks can complete digging work in just a few hours that would otherwise take days with traditional methods. The actual speed can vary, but vacuum trucks offer a faster and more precise alternative to conventional digging techniques.

A septic vacuum truck can be used for vacuum excavation, though there are more common or ideal tools. Vacuum excavation usually requires equipment designed specifically for the task, such as a hydro excavator vacuum truck. These trucks use high-pressure water to break up the soil, which is then vacuumed into a debris tank. On the other hand, septic vacuum trucks are primarily used for pumping and transporting liquid waste from septic tanks. While they have powerful suction capabilities, they may not be as effective or efficient at breaking up and removing soil as dedicated vacuum excavation trucks.