No construction permits shall be required for the sources listed in Regulation 61-62.1, Section II (B)(1)(a) through (c) (pdf) which burn virgin fuel and which were constructed prior to February 11, 1971 and which are not located at a facility that meets the definition of a major source as defined in Regulation 61-62.70.2(r) (pdf); however, modifications at these facilities may trigger the requirement to obtain a construction permit.