I'm confused. You originally stated that this was an urn bubbler, now you are talking about the lower tier of a fountain. Which is it?
If it is an urn, is that the empty weight? If so, you will need to allow for the additional weight of the water. At 8.33 lbs/gallon, you are talking considerable extra weight.
The base of most urns are 18' - 24 ", so you will need at least 40" basin so you will be able to access the pump. You will not need a pump vault. Basins can be pricey, but again, they are engineered to support this kind of weight. Check with EasyPro. They have a 40" basin that, if desired, can be reinforced with concrete for additional support capacity.
"Everybody is ignorant, only on different subjects." - Will Rogers