Mineral material contracts or permits may be issued within existing areas leased or under permit under the 1920 Mineral Leasing Act, as amended (30 U.S.C. §§ 181–187); section 402 of Reorganization Plan No. 3 of 1946 (5 U.S.C. Appendix); the 1947 Mineral Leasing Act for Acquired Lands, as amended (30 U.S.C. § 351 et seq.); and the 1970 Geothermal Steam Act (30 U.S.C. §§ 1001–1025), provided that it has been determined that removal will neither endanger nor unreasonably interfere with lease operations, and provided further that the lease terms do not prohibit disposal.