Colo. Rev. Stat. § 34-33-134
In order to encourage advances in coal mining and reclamation practices and to allow postmining land use for industrial, commercial, residential, or public use, including recreational facilities, the board, with the approval of the secretary, may authorize departures in individual cases on an experimental basis from the environmental protection performance standards promulgated under sections 34-33-120 and 34-33-121. Such departures may be authorized if: The experimental practices are potentially more or at least as environmentally protective, during and after coal mining operations, as those required by promulgated standards; the coal mining operations approved for particular land use or other purposes are not larger or more numerous than necessary to determine the effectiveness and economic feasibility of the experimental practices; and the experimental practices do not reduce the protection afforded the public health and safety below that provided by promulgated standards.
C.R.S. § 34-33-134