Hello, I am Hezbullah, an expert civil engineer with lots of experience in Autocad, civil 3D, 3D Max, Revit, Python and more. I specialize in data extraction and manipulation so I am confident that I can help you extract drainage data from Civil3D and import them again into your property set as extended data.
I understand exactly what you're looking for in terms of the desired output format for the extracted data (a CSV file), the specific property set you want to use for importing the drainage data (pit, pipe, headwall, culvert) back into extended data tab in properties section), and finally creating 3D solids from the drainage parts that include the attached extended data.