I have a similar unit, One mistake I made is that I didn't build it for a cover-all type shed to fit. Tarps will work but require frequent replacing and here having to have some salt added to prevent it from becoming just one big block it attracts deer, who walk on it and punch holes in the tarp which lets water in which in turn removes the salt. I also used coal ash along with salted sand, alas no more coal ash for me so just sand now. I used to get a tri-axle load every 2-3 years.
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something similar to this would be much nicer then a tarp;
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