Say, there's a thought! How about a part of the Panama Canal RR? Either the Colon or Balboa end would be doable. You could model it ca 1855, when it opened, or, even better, during the construction of the canal, which saw the RR move men, equipment, supplies, and hundreds of millions of cubic meters of earth and rocks from the canal to dump sites. The method of loading and unloading the earth is fascinating, and would make a great model. Most of the cars carrying the dirt spoils were wooden flat cars lined with steel floors that used the Lidgerwood system for unloading. (I'm a student of Lidgerwood, which is how I know about this.) The flatcars had one side, and steel aprons between them, so they were one long car. The rock and dirt were blasted loose. Two sets of tracks were moved to the site. Steam shovels, on one set of tracks, picked up the loosened dirt and piled it on the flat cars on a parallel set of tracks. The train moved forward until all cars were filled. When the train got to one of the dumping grounds, a car carrying a steel plow was attached at the end and a winch with a cable stretching the length of the train attached the plow to the engine. The winch, powered by the engine, pulled the plow the length of the train by winching up the cable, unloading the train in ten minutes. The plow and winch were detached for use on the next train. What a great model!