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 area would be open to locatable mineral entry, open to mineral leasing (with primarily moderate constraints on 24,102 acres and major constraints on the remaining 3,200 acres), and open to mineral materials disposal. 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 values of concern. Except for a small area of high-potential for sand and gravel, low-potential for bentonite and gypsum and low to very low development potential for oil and gas may minimize adverse impacts to minerals development.
The Foster Gulch Paleontological Area is primarily open to ROW authorizations (24,541 acres), with the remainder managed as an ROW avoidance/mitigation area (2,761 acres). Managing this area as primarily open to ROW authorizations would result in adverse impacts to the values of concern associated with surface disturbance and ROW development. Managing most of the area as open to ROW authorizations would result in beneficial impacts to ROWs by allowing these authorizations in the area.
Alternative A limits motorized vehicle use to existing roads and trails in the area. Limiting motorized travel to existing roads and trails may benefit the values of concern in the ACEC by preventing open access that could degrade paleontological resources.
The Foster Gulch Paleontological Area is open to livestock grazing under Alternative A. Managing this area as open to livestock grazing could result in adverse impacts to paleontological resources that may be damaged by livestock trampling and wallowing in areas of concentrated livestock use. Proper management of livestock grazing can mitigate the impacts of grazing by improving the distribution of livestock.
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 formations and PFYC 4 formations (on a case‐by‐case basis), that would provide some protection to the paleontological values.
Management for the ACEC under Alternative B is designed to reduce adverse impacts to paleontological and geological values of concern from surface disturbance. Management under this alternative requires avoiding or prohibiting surface-disturbing activities in the Foster Gulch Paleontological Area ACEC, and prohibiting the use, occupation, construction, or maintenance of facilities in the Foster Gulch Paleontological Area ACEC that are inconsistent with the management direction and objectives for the area. Allowing minor surface-disturbing activities in the Foster Gulch Paleontological Area ACEC if they are preceded by a paleontological sensitivity survey and, if necessary, are monitored during construction, would help protect paleontological resources in the area. Restricting surface-disturbing activities could increase delay or expense, but would continue to allow some activities while also protecting the integrity of fossil-bearing material in the area.
Under Alternative B, withdrawing the Foster Gulch 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 under Alternative A. Restricting mineral development would result in greater beneficial impacts to the paleontological and geologic values in the area than Alternative A. The low potential for mineral resources in the area may minimize these impacts.
Alternative B is more restrictive than Alternative A in managing ROWs, motorized vehicle use, and livestock grazing; adverse impacts to these resource uses would be greater than under Alternative A. Alternative B manages the Foster Gulch Paleontological Area ACEC as an ROW and renewable energy 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 Foster Gulch Paleontological Area 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. Any restrictions on grazing could reduce the currently available 1,206 AUMs in the ACEC and adversely impact livestock grazing.
Alternative B allows fossil collection, excavation, or removal in the Foster Gulch 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, or museum and educational projects that provide for detailed recordation, reporting, care of specimens, and availability of specimens to other scientists and museums. Such requirements would result in beneficial impacts by protecting the integrity of the resources and enable the advancement of scientific knowledge.
Alternative C does not designate the area as an ACEC; the BLM would manage the area in accordance with multiple use principles consistent with other resource objectives.
The management of and impacts associated with mineral development under Alternative C would be the same as under Alternative A.
Similar to Alternative A, Alternative C manages the Foster Gulch Paleontological Area as primarily open to ROW authorizations (25,621 acres), and manages a smaller area as an ROW avoidance/mitigation area (1,681 acres). ROW management would result in impacts to the values of concern similar to Alternative A.
Alternative C is more restrictive to motorized vehicle use than Alternative A (travel is limited to designated roads and trails on 17,591 acres and existing roads and trails on 9,711 acres), but less restrictive than Alternative B. Therefore, Alternative C would result in greater beneficial impacts to the values of concern more than Alternative A, but less than Alternative B.
Applicable laws and regulations and the 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 under 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 Foster Gulch Paleontological area (4,974 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 designates the McCullough Peaks South Paleontological Area as an ACEC (6,994 acres); the other alternatives do not. The values of concern in the proposed McCullough Peaks South Paleontological Area ACEC are paleontological resources in the form of mammalian and paleobotanical fossils and geochemical data used in the study of a major Carbon Isotope Excursion recorded during an ancient period of global warming known as the PETM. Scenic and geologic features also are valuable in this ACEC. Threats to this proposed ACEC include surface disturbance from mineral (primarily oil and gas) and ROW development.