Alternative A 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 area would be open to locatable mineral entry, open to mineral leasing (with primarily moderate constraints on 11,691 acres), and open to mineral materials disposal on 23,113 acres under Alternative A. A plan of operations would not be required for notice-level locatable minerals activities. The low potential for gypsum and bentonite, the low (23,320 acres) to very low (575 acres) development potential for oil and gas, and the low potential for sand and gravel in the area would result in fewer adverse impacts to minerals development activities.
Alternative A manages the Clarks Fork Basin/Polecat Bench West Paleontological Area as open to ROW authorizations (20,068 acres), and manages a smaller area as an ROW avoidance/mitigation area (3,271 acres). Standard guidelines related to surface disturbance would apply. ROW management would benefit this resource use in open areas, but may limit such development in avoidance/mitigation areas or require specific mitigation that may increase project costs and timeframes. Restrictions on ROW developments would generally benefit paleontological resources by reducing surface-disturbing activities and potential destruction of paleontological values.
Alternative A limits motorized vehicle use to existing roads and trails, which may result in adverse impacts to values of concern by allowing access to travel that may disturb and degrade paleontological values of concern in the area.
The Clarks Fork Basin/Polecat Bench West Paleontological Area is open to livestock grazing under Alternative A. Livestock trampling and wallowing in areas of concentrated livestock use can damage exposed paleontological resources. While in most instances, concentrated livestock use would result in adverse impacts to paleontological values, proper livestock grazing management can mitigate these impacts by improving the distribution of livestock.
Restricting surface disturbance solely through application of the standard guidelines for surface disturbance may lead to damage to the identified values of concern, soil erosion, spread of invasive species, and impacts to water quality. Management under this alternative would be the least restrictive of ROW authorizations and other surface-disturbing activities, and would result in the largest adverse impact to the identified values of concern.
Management of surface-disturbing activities in the ACEC emphasizes avoiding impairment of the management objectives and existing values, while protecting the integrity of fossil-bearing material. Under Alternative B, avoiding or prohibiting surface-disturbing activities and the use, occupation, construction, or maintenance of facilities in the Clarks Fork Basin/Polecat Bench West Paleontological ACEC that are inconsistent with the management direction and objectives for the area would restrict development and maintenance activities, but would benefit the protection of paleontological resources. Requiring that minor ROW authorizations and other minor surface-disturbing activities be preceded by paleontological sensitivity surveys and potential monitoring during construction, 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. These ROW and surface-disturbance stipulations would further protect paleontological resources in the area.
Under Alternative B, withdrawing the Clarks Fork Basin/Polecat Bench West Paleontological ACEC from appropriation under the mining laws and closing the area to geophysical exploration would result in greater adverse impacts to mineral development than Alternative A. Restricting mineral development would benefit the ACEC by reducing the potential for destruction or degradation of paleontological values and the other adverse impacts associated with surface disturbance (e.g., the potential spread of invasive species).
Under Alternative B, the Clarks Fork Basin/Polecat Bench West Paleontological ACEC is a renewable energy exclusion area and motorized vehicle use is limited to designated roads and trails. Excluding renewable energy would result in adverse impacts to the ability to develop renewable energy. Limiting motorized vehicle use to designated roads and trails would restrict access in the area by limiting the roads available for recreational and other motorized travel. Restrictions on renewable energy and motorized travel would reduce the possibility of damage to paleontological resources from surface disturbance and would allow the closure of routes that may result in damage to paleontological resources. Management of travel and renewable energy is more restrictive under Alternative B than under Alternative A and resulting beneficial impacts for the values of concern would be greater under Alternative B.
Management under Alternative B continues livestock grazing provided it does not disturb the natural, educational, and scientific research values of the ACEC. The flexibility to restrict livestock grazing if use becomes concentrated or adversely affects other resource values may result in beneficial impacts to the values of concern by reducing potential degradation by livestock. Conversely, any restrictions could adversely affect livestock grazing by reducing the number of AUMs available in the ACEC from its current level of 1,344.
Fossil collection, excavation, or removal in the Clarks Fork Basin/Polecat Bench West Paleontological ACEC would be allowed under a permit issued by the Wyoming BLM State Director and only to institutions and individuals engaged in BLM-approved research, museum, or educational projects. This management would protect the integrity of the resources and enable the advancement of scientific knowledge in the area, but also would restrict recreational collection of fossils.
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 area would be open to locatable mineral entry and open to mineral leasing (with primarily moderate constraints on 14,951 acres), and primarily open to mineral materials disposal (20,543 acres). Impacts would be similar to those under Alternative A.
Alternative C manages the Clarks Fork Basin/Polecat Bench West Paleontological area as an avoidance/mitigation area for ROW authorizations (21,058 acres), and manages a smaller area managed as open to ROW (12,796 acres). Standard guidelines related to surface disturbance would apply, but the additional restrictions under Alternative B would not. As under Alternative B, Alternative C limits motorized vehicle use to designated roads and trails. Management under Alternative C is more restrictive to ROW development and motorized travel than under Alternative A.
The standard guidelines related to surface disturbance would apply and may result in additional surface disturbance in the area compared to alternatives A or B, leading to potential soil erosion, spread of invasive species, impacts to water quality and damage to the identified values of concern. Management under Alternative C would be the least restrictive of ROW authorizations and other surface-disturbing activities and would result in the largest adverse impact on the identified values of concern.
Alternative D does not designate this area as an ACEC. Part of the Clarks Fork Basin/Polecat Bench West Paleontological area (4,972 acres) is within the proposed PETM ACEC. See the Paleocene-Eocene Thermal Maximum section for an analysis of the effects of management in this area.
The Clarks Fork Canyon area would be designated as an ACEC under alternatives B (12,259 acres) and D (2,724 acres); it would not be designated as an ACEC under alternatives A or C. The values of concern in the proposed Clarks Fork Canyon ACEC are geologic features, including the Canyon Mouth Anticline, and glacial features, open space, recreational opportunities, special status species plants and wildlife, and wildlife habitat. Threats to this proposed ACEC include surface disturbance from mineral and ROW development.