(1)    Case-by-case specification. If visibility in an area is identified as an important value of the area under section 169A of the federal clean air act, the department shall specify on a case-by-case basis the best available retrofit technology for any existing major source located in the area and identified under section 169A of the federal clean air act.

   (2)   Considerations. In specifying the best available retrofit technology, the department shall consider:

      (a)    The cost of compliance.

      (b)    The existing pollution control technology in use at the source.

      (c)    The remaining useful life of the source.

      (d)    The degree of improvement in visibility which may be anticipated to result from the use of various retrofit technologies.

      (e)    The energy and nonair quality environmental impacts of compliance.