For all federal undertakings that may affect cultural resources, the BLM complies with NHPA Section 106 before proceeding with the undertaking. Section 106 compliance typically includes inventory and evaluation, and consultation with the SHPO. Existing Planning Area plans considered the maintenance of a ¼-mile-wide buffer zone adequate protection in most site situations, and the occasional application of a 5-mile-wide buffer zone a generous allowance that would protect the viewshed of the resource. However, with the introduction of new technologies, particularly wind turbines that are often grouped into wind farms, these distances do not always protect the significant values of a resource. Because the historic preservation community has begun placing more emphasis on setting as the initial aspect of integrity for a NRHP-eligible cultural resource, management must approach the application of viewshed criteria with flexibility, and account for the distance from the resource and the type of intrusion when determining the impact. On a case-by-case basis, and as appropriate for some projects, project decisions account for the importance of viewshed in a resource’s eligibility and the distance necessary to protect its NRHP significance.
Methods and assumptions used in this impact analysis include the following:
Cultural resources will continue to be found throughout the Planning Area.
All surface-disturbing activities may damage, destroy, or otherwise impact cultural resources.
Natural and prescribed fire may damage rock art sites and sites composed of combustible materials.
Compliance with Section 106 before project initiation is required by law. All cultural resources will be protected in accordance with federal laws and BLM regulations and agreements, including the national programmatic agreement (BLM, Advisory Council on Historic Preservation, and National Conference of State Historic Preservation Officers 1997) and the Wyoming State Protocol (BLM and Wyoming SHPO 2006), regardless of whether the resources are specifically identified in the RMP.
Avoidance is the preferred mitigation measure. When avoidance is not a practicable solution, the BLM will develop measures to mitigate impacts in accordance with Section 106 and other applicable laws and guidance.
Adverse impacts to historic properties from surface-disturbing activities occur primarily at the time of initial surface disturbance. The BLM used the projected numbers for short-term surface disturbance to quantify impacts to cultural resources.
The intensity of surface disturbance by alternative, as identified in Appendix T, equates to levels of development and, in turn, increased access to public lands.
Increases in the number and extent of surface-disturbing activities and improved access may all result in increased impacts to cultural resources.
The BLM has not identified all tribally sensitive sites in the Planning Area.
Identifying tribally sensitive sites will benefit heritage resources.
Tribal consultations benefit heritage resources.