One-Line Diagram & Schematics Help

Hi, Im a Mechanical Designer that was recently thrust into the Civil world (not sure why i accepted this since i despise civil and even Autocad at this point lol) and I'm having issues with the electrical portion, especially the One-Line Diagram and im looking for any advice i can get.

The project is a fairly simple Power Distribution Upgrade for a small area; demo of existing over-head and installation of underground power.

They have requested i show the existing elements for removal one the one-line diagram with the new elements. is this typical for a one-line or schematic? if so, what is the normal way to show it?

NOTE: I have NEVER done a one-line diagram nor have i ever had to really work with them so im completely "green" in this area.

Thanks for any help and if you need more information just let me know.

BIM (Building Information Modeling) assists MEP Design Firms in the design development stage. BIM experts interact with engineers for comprehending design-intent and providing value-added support from the phase of conceptual design to construction. The BIM specialists translate the designer’s thoughts into constructible information in the form of 2D drawings and 3D models.

Conceptual or Schematic Design is a primary design scheme, which defines the general scope of the project, including the scale and relationship among building modules. At this stage, the proposed system is described in terms of integrated ideas & concepts, corresponding to the LOD 200 Revit Models.

The next stage is the detailed design which follows a conceptual or schematic design stage. Here the design decisions are worked out in a comprehensive way. The details get reflected in the BIM Model, corresponding to LOD 300 Revit model. It is from this stage that the 3D BIM Modelers provide the drafted to-scale drawings, demonstrating the project.