The commission shall not approve any issue or assumption unless, after investigation of the purposes and uses of the proposed issue and the proceeds thereof, or of the proposed assumption of obligation or liability, the commission finds that the issue or assumption is for some lawful object within the corporate purposes of the public utility, and it is necessary or appropriate for or consistent with the performance by the public utility of its service to the public and will not impair its ability to perform that service.
La. R.S. § 45:1171