Tank vehicle and tank car loading and unloading facilities must be separated from warehouses, other plant buildings or the nearest line of adjoining property that can be built upon by a distance of at least 25 feet (25', or 7.6 m) for Class I liquids and at least 15 feet (15', or 4.6 m) for Class II and Class III liquids, measured from the nearest fill spout or transfer connection.
Okla. Admin. Code § 165:25-14-13