When, after March 23, 1906, authority is granted by Congress to any persons to construct and maintain a bridge across or over any of the navigable waters of the United States, such bridge shall not be built or commenced until the plans and specifications for its construction, together with such drawings of the proposed construction and such map of the proposed location as may be required for a full understanding of the subject, have been submitted to the Secretary of the department in which the Coast Guard is operating for the Secretary’s approval, nor until the Secretary shall have approved such plans and specifications and the location of such bridge and accessory works; and when the plans for any bridge to be constructed under the provisions of sections 491 to 494 and 495 to 498 of this title, have been approved by the Secretary it shall not be lawful to deviate from such plans, either before or after completion of the structure, unless the modification of such plans has previously been submitted to and received the approval of the Secretary. This section shall not apply to any bridge over waters which are not subject to the ebb and flow of the tide and which are not used and are not susceptible to use in their natural condition or by reasonable improvement as a means to transport interstate or foreign commerce.