Hi Bill - sorry, I missed this one earlier.
All depth data is stored within the workspace database file. The only thing that is retrieved from the original sonar log files is the sonar data, which is too large to be stored practically in the DB. If you are not using the sonar viewer or sidescan mosaic, then the original files are not required. If the data was imported from "non sonar log" sources (e.g. GPX, CSV), then the original files are never required by RM after import.