Whenever the owners of lots or lands abutting upon any street, avenue, or alley within the city, representing three-fourths of the front footage thereon, so that an improvement district when created will make up one continuous or extended thoroughfare or more, shall petition the mayor and city council to make improvement of such street, avenue, or alley without cost to the city, and to assess the entire cost of any such improvements in any such street, avenue, or alley, including intersections of streets or avenues and spaces opposite alleys, against the private property within such improvement district or districts, it shall be the duty of the mayor and city council to create the proper improvement district or districts, which shall be consecutively numbered, and to improve the same and to proceed in the same manner and form as provided for in other improvement districts. The mayor and city council shall have power to levy the entire cost of such improvements of any such street, avenue, or alley, including intersections of streets or avenues and spaces opposite alleys, against the private property within such district, and to issue Street Improvement Bonds of District No. ..... to pay for such improvements in the same manner and form as provided for in other improvement bonds. Such bonds shall be issued to cover the entire cost of so improving such streets or avenues, intersections of the same, and spaces opposite alleys. If the assessments provided for, or any part thereof, shall fail, or for any reason shall be invalid, the mayor and city council may make other and further assessments upon such lots or lands as may be required to collect from the same the cost of any improvements properly chargeable thereto, as provided in this section. The mayor and city council shall have the discretion to deny the formation of the proposed district when the area to be improved has not previously been improved with a water system, sewer system, and grading of streets. If the mayor and city council should deny a requested improvement district formation, they shall state their grounds for such denial in a written letter to interested parties.