Section 746.18 - Mining plan modification(a) Mining plan modifications shall be approved by the Secretary.(b) The approval of mining plan modifications shall be in accordance with the procedures of this part for mining plan approval.(c) Surface coal mining and reclamation operations on lands containing leased Federal coal pursuant to a permit revision issued by the regulatory authority shall not commence until-(1) OSM determines that the permit revision does not constitute a mining plan modification under this section, or(2) If the permit revision constitutes a mining plan modification under this section, such modification has been approved by the Secretary.(d) Permit revisions constitute mining plan modifications if they meet any of the following criteria:(1) Any change in the mining plan which would affect the conditions of its approval pursuant to Federal law or regulation other than the Act;(2) Any change which would adversely affect the level of protection afforded any land, facility or place designated unsuitable for mining;(3) Any change in the location or amount of coal to be mined, except where such change is the result of:(i) A minor change in the amount of coal actually available for mining from the amount estimated; or(ii) An incidental boundary change;(4) Any change which would extend coal mining and reclamation operations onto leased Federal coal lands for the first time;(5) Any change which requires the preparation of an environmental impact statement under the National Environmental Policy Act or 1969, 42 U.S.C. 4321 et seq.;(6) Any change in the mining operations and reclamation plan that would result in a change in the postmining land use where the surface is federally-owned.