Nice structure, looks like a hefty lumber bill. Did you price out roof trusses? Could have eliminated all the interior poles...
Crazy to see when you southerners just plop poles into holes right over the native dirt. Recipe for failure anywhere up north where the ground freezes, or at least a major headache to try to clean up after the fact. Even so, like jaxs says, you might have a mud pit in there eventually. I would dig a drainage trench around the outside to at least encourage the local ground water flow, and roof water run-off, to go around or away from the storage area.