The CEQ suggests cumulative impact analyses should focus on meaningful impacts, and not exhaustively analyze all possible cumulative impacts (CEQ 1997b). Therefore, the analysis in this RMP and EIS focuses on past, present, and future actions anticipated to have environmental impacts similar to the kinds of impacts identified for implementing the alternatives including but not limited to those resulting in meaningful impacts to historically important resources, those with a potential for violating legal standards or laws, or other identified projects or actions in the geographic area of analysis (i.e., the Cumulative Impact Assessment Area [CIAA]) that relate to the identified cumulative impact issues.
To address the effects of these actions, the analysis is structured around a series of cumulative issue statements (described later in this section) that capture the major cumulative impacts in the CIAA. The BLM developed these issue statements using:
Issues identified during scoping.
Internal scoping (i.e., the professional judgment of BLM resource specialists and Cooperating Agencies).
A review of other reasonably foreseeable future actions in the CIAA.
Consideration of context and intensity of potential impacts.
For the cumulative impacts analysis, the BLM paid particular attention to: impacts to public health and safety; controversial issues or those with a substantial public interest; the uniqueness of resources affected; potential for violation of legal standards or laws; and potential impacts to legally protected resources.
To focus the scope of cumulative impact analysis, cumulative issues were considered in the context of baseline conditions (Chapter 3 – Affected Environment), the incremental impacts on individual resources described in this chapter, the actions and decisions described in the reasonably foreseeable future projects (Table 4-27), and the following factors as modified from the CEQ’s Considering Cumulative Effects Under the National Environmental Policy Act (CEQ 1997b):
Does the affected resource have substantial value relative to legal protection and/or ecological, cultural, economic, or social importance?
Are reasonably foreseeable future actions anticipated to have environmental impacts similar to the kinds of impacts identified for RMP alternatives?
Have any recent or ongoing NEPA analyses of similar actions in the geographic area identified important adverse or beneficial cumulative impact issues?
Has the impact to the resource been historically important, such that the importance of the resource is defined by past loss, past gain, or investments to restore resources?
The cumulative impact analysis was further bound by considering the following factors:
• Timeframe – Timeframes are based on the duration of the direct and indirect effects of the proposed action and alternatives (the life of the RMP for most issues).
• Geographic area – The geographic area of analysis, or the CIAA, covers different geographic areas depending on the specific resource being evaluated. For the most part, the CIAA is the Bighorn Basin (including the portions in Montana) except for 1) issues involving air quality, for which the CIAA will be the affected air sheds and nearby Class I areas; 2) water quality, particularly surface water, which will include drainage areas flowing into and out of the Planning Area (e.g., Owl Creek, which turns into the Bighorn River); and, 3) social and economic conditions, for which the CIAA is the four counties that overlap the Planning Area.
• Analytical assumptions – see the Assumptions for Analysis below.