I have attached a word document showing an image and some typed out simple calculations. I am working on an oil containment system for a new building my employer is going to be building soon. Its pretty simple in the middle of the floor we put a catch basin with a 24"x24" grate. This catch basin is to be 4" below the floor so the perimeter of the oil containment area will be 4" above the catch basin (obviously). Am I correct in assuming that frustum pyramid volume formula is the correct way to calculate the volume of oil or water the sloped floors could hold assuming the catch basin is all ready full to the top of the grate? Does a frustum pyramid have to have the same shape for its base and top or could it be a hexagon on the bottom and a square on top like in this case? I would appreciate some feedback on my math in the word document the formula is just a basic frustum pyramid volume formula I remember from college. My answer seems quite large to me though. Feel free to move this to the Math section if you wish, I was thinking of putting it there but it is a design questions as well. Thanks.