This Part levies, in addition to other taxes and licenses levied in this state, a license tax on every person owning or operating or owning and operating a public utility, as herein defined, for the privilege of engaging in such business carried on wholly in this state, and not a part of interstate commerce.  This tax is not intended to be a tax for the privilege of engaging in interstate commerce, nor is it intended to be a tax on the business of interstate commerce nor is it intended to be a tax having any relation to interstate or foreign business or commerce in which any such person, firm, association or corporation may be engaged in addition to its business in this state.  

The provisions of this Part and the taxes collectible hereunder shall not apply to or be levied against gross receipts derived from any business or operations conducted on navigable waters of the United States.