Alternative A does not designate the area as an ACEC; the BLM manages the area in accordance with multiple use principles consistent with other resource objectives.
The McCullough Peaks South Paleontological area would be open to locatable mineral entry on 6,882 acres, open to mineral leasing (with primarily moderate constraints on 4,876 acres and major constraints on the remaining 2,105 acres), and primarily open to mineral materials disposal (6,567 acres). Mineral development is one of the threats to the paleontological and geological values of the area, and allowing this type of development with minimal restrictions would result in surface disturbance that would cause adverse impacts to the values of concern. Except for a small area of high-potential for sand and gravel, the low potential for bentonite and gypsum and very low development potential for oil and gas may minimize these adverse impacts.
The McCullough Peaks South Paleontological Area is primarily managed as open to ROW authorizations (5,709 acres), with the remainder managed as a ROW avoidance/mitigation area (1,250 acres). Allowing ROW authorizations in the area would result in beneficial impacts to these authorizations. Managing this area as primarily open to ROW authorizations would result in adverse impacts to the values of concern by increasing the potential for surface disturbance and associated with ROW development.
Motorized vehicle use is limited to designated roads and trails in the area; thereby limiting access and use of certain roads in the area and limiting disturbance or degradation to the values of concern.
The McCullough Peaks South Paleontological Area is open to livestock grazing under Alternative A, which may result in adverse impacts to the paleontological values of concern in the area. However, impacts from concentrated livestock use, which can damage exposed paleontological resources, can be mitigated through proper livestock management that improves livestock distribution.
Applicable laws and regulations and the management described in Section 4.5.2 Paleontological Resources control the collection of fossils under Alternative A. These decisions include protective management, such as surveying and monitoring surface-disturbing activities for PFYC 5 and, on a case-by-case basis, PFYC 4 formations that would provide some protection to the paleontological values.
Management for the McCullough Peaks South Paleontological Area ACEC under Alternative B reduces adverse impacts from surface disturbance and development to the paleontological and geological values of concern in the area. Alternative B requires avoiding or prohibiting surface-disturbing activities in the McCullough Peaks South Paleontological Area ACEC, and prohibiting the use, occupation, construction, or maintenance of facilities that are inconsistent with the management direction and objectives for the area. Allowing minor surface-disturbing activities in the ACEC if they are preceded by a paleontological sensitivity survey and, if necessary, monitored during construction, would help to protect paleontological resources in the area. Restricting surface-disturbing activities may increase project costs and timeframes, but would continue to allow some activities while also protecting the integrity of fossil-bearing material in the area.
Withdrawing the McCullough Peaks South Paleontological Area ACEC from appropriation under the mining laws, managing the area as administratively unavailable to mineral leasing, and closing it to mineral materials disposal and geophysical exploration would result in greater adverse impacts to mineral development than Alternative A. Restricting mineral development would result in greater beneficial impacts to the paleontological and geologic values in the area than Alternative A. As described for Alternative A, the low potential for mineral resources in the area may minimize these impacts.
Alternative B is more restrictive than Alternative A regarding ROW management, motorized vehicle use, and livestock grazing; therefore, adverse impacts to these resource uses would be greater than under Alternative A. Alternative B manages the McCullough Peaks South Paleontological Area ACEC as a renewable energy and ROW avoidance/mitigation area, limits motorized vehicle use to designated roads and trails, and allows livestock grazing under existing regulations provided it does not disturb the natural, educational, and scientific research values of the ACEC. This management would reduce the potential for surface disturbance and would provide increased flexibility to further restrict activities (such as livestock grazing and resource-degrading travel routes) determined to be adverse to the values of concern. Conversely, any restrictions on grazing could reduce the currently available 722 AUMs in the ACEC and adversely affect livestock grazing. Requiring paleontological sensitivity surveys prior to approval of minor ROW authorizations may have long-term impacts by increasing processing times of authorizations and potentially requiring mitigation, relocation, or modification of facilities if paleontological resources are found.
Alternative B allows fossil collection, excavation, or removal in the McCullough Peaks South Paleontological Area ACEC only under a permit issued by the Wyoming BLM State Director and only by institutions and individuals engaged in BLM-approved research and museum or educational projects that provide for detailed recordation, reporting, care of specimens, and availability of specimens to other scientists and museums. Such requirements would, however, result in beneficial impacts by protecting the integrity of the resources and enabling the advancement of scientific knowledge in the area.
Alternative C does not designate the area as an ACEC; the BLM manages the area in accordance with multiple use principles consistent with other resource objectives.
Management of and impacts associated with mineral development under Alternative C would be similar to those under Alternative A. The area is open to mineral leasing (with primarily moderate constraints on 4,405 acres, standard restrictions on 2,161 acres, and major constraints on the remainder), and open to mineral materials disposal on 6,772 acres.
ROW management in the McCullough Peaks South Paleontological Area under Alternative C is more restrictive than under Alternative A, but less than under Alternative B. The area is primarily an avoidance/mitigation area for ROW authorizations (3,776 acres) and open for ROW authorizations (3,218 acres) on the remainder. Management of ROWs under Alternative C would result in greater beneficial impacts to the values of concern in the ACEC than Alternative A, but less than Alternative B.
Management of and impacts associated with motorized vehicle use under Alternative C would be the same as under Alternative A.
Applicable laws and regulations and management described in Section 4.5.2 Paleontological Resources control the collection of fossils under Alternative C. This management would be less restrictive to surface disturbance than Alternative A, because it does not require on‐the‐ground surveys for PFYC 4 formations on a case‐by‐case basis.
Alternative D does not designate this area an ACEC. Part of the McCullough Peaks South Paleontological Area (4,958 acres) is within the proposed PETM ACEC. See the Paleocene-Eocene Thermal Maximum section for an analysis of the effects of management of this area.
Alternative B would designate the Rainbow Canyon area as an ACEC (1,443 acres); the other alternatives would not. The values of concern in the proposed Rainbow Canyon ACEC are paleontological resources in the form of dinosaurian and paleobotanical fossils, and weathered and eroded geologic and scenic features. Threats to this proposed ACEC include surface disturbance from mineral and ROW development.