What must be done to the service raceway entering a building from an underground distribution system?

When a service raceway is installed to enter a building from an underground distribution system, it is crucial that it be sealed properly. This sealing is necessary to prevent the ingress of moisture and potentially harmful gases, which can damage the electrical components inside the raceway or create safety hazards. Sealing the raceway helps to maintain the integrity of the electrical system by ensuring that any environmental factors, such as water or soil contaminants, do not compromise the safety and reliability of the electrical service within the building.

Other options like painting, adding warning signs, or adjusting the burial depth serve different purposes and are not specifically required for sealing the raceway. Painting might be used for identification or aesthetic purposes, warning signs may alert individuals of underground utilities, and deeper burial could be related to physical protection or local code requirements but does not address the sealing needs for moisture ingress. Thus, sealing stands out as the essential requirement in this context.