To generate a surface file on Civil 3D from contours, you will need to import the shapefile (SHP).
You can type MAPIMPORT in Civil 3D (Make sure to select ESRI Shapefile on the Files of type drop down) or open directly a DXF file (Make sure the design has a coordinate system CRS set up).
The next window will pop up after opening the Shapefile:
You can also access this menu by using the command ADESETCRDSYS.
Once it’s open you will click on: Select Coordinate System...
Once you click on the Select Coordinate System… button, you will see the following window were you can type the State plane, ESPG code, referenced to… It will start auto filling afterwards showing you the possible options to your keywords.
Make sure to select the correct CRS matching your design and GCPs used in Site Scan.
After Selecting the Coordinate System, finish importing the Shapefile into Civil 3D.
Click where it says Create surface, you will find this option in your tool space to the left.
Once you click Create Surface you will see this window, make sure that the type you choose is TIN Surface. Click OK to create the Surface file.
Changing values in this window will only modify visual results inside Civil 3D; the changes won't be reflected on the exported LandXML Surface.
Right click on contours and click Add... you will get this window, make sure to add the name where it says Description. Do not modify settings and click OK.
Once the OK button was pressed, you'll be requested to select all contour lines that you want to include in the surface. After all lines are highlighted, press enter to finish adding definitions.
Processing time may vary depending on the number of contour lines and area covered.
Once you have added the Contours, right click on the surface you created and click Export LandXML...
After you have created the Surface. Log into Site Scan, go to the desired project, click Files and upload the LandXML Surface.
Once you enter the Files tab you will click Upload Project File, and upload the LandXML.
After the LandXML. Is uploaded, you can now use it on the Cut and Fill / Volume tools and on the files tab on the 2D view.