Kyle, we use CymeCap software to make these calculations. You'll need to consider the cable type, temp. rating, concrete encasement, soil resistivity, depth, number of cables, load, load factor, DB or duct, etc.
Check out ICEA documents P-53-426 and S-66.524
In case you're still working on this --
We use a "rule of thumb" of 5cfm per kVA of transformer, which is conservative, but helps account for issues that hinder the performance of the blower. This would give you a value of 5000 cfm forced air ventilation. You should place the intake and exhaust...