How big is the plot and what shap is it in? If very big, depending on your soil type, I'm not sure if the trenching would help. Sounds like it is in a flat or bottom where the water won't drain away from the plot even with the trenching. To haul enough dirt to raise the plot level even a foot would take a LOT of dirt, depending on the size of the plot. I would instead hire a dozer and excavator and move the plot location higher on a natural rise. It will probably be worth the money in the long run.