This chapter describes environmental consequences that may result from implementing the four alternatives described in Chapter 2. The purpose of this chapter is to determine the potential impacts of the federal action on the human environment. As defined by the Council on Environmental Quality (CEQ) the “human environment” shall be interpreted to include the natural and physical environment and the relationship of people with that environment (40 Code of Federal Regulations [CFR] 1508.14). The federal action is the Bureau of Land Management (BLM) selection of a resource management plan (RMP) on which to base future land use actions.
The analysis of environmental consequences focuses on key planning issues (see Chapter 1) raised during the scoping process rather than providing an encyclopedic discussion of all possible consequences. The organization of Chapter 4 follows the same order as Chapter 3 and allows the reader to compare existing resource conditions (Chapter 3) to potential impacts (Chapter 4) for the same resource. The following describes the organization of information for the analysis of each resource or resource use.
The discussion of environmental consequences for each resource program begins with a brief definition of an impact for the resource. When applicable, definitions of the following types of impacts also are included:
Adverse or Beneficial Impacts. When applicable, this chapter differentiates beneficial and adverse impacts. For example, an alternative that increases the number of water sources away from existing rivers and streams is expected to have a beneficial impact on livestock grazing and riparian/wetland areas; however, if this alternative also increases livestock concentration around new water sources, it may adversely impact grassland and shrubland communities by degrading vegetation and compacting soil in these areas. The purpose of presenting both beneficial and adverse impacts for key planning issues is to help the BLM decision maker and readers understand the multiple-use tradeoffs associated with each alternative. However, this chapter does not describe all possible impacts and, unless otherwise stated, assume that impacts described in this chapter would be adverse.
Direct or Indirect Impacts. In general, direct impacts result from BLM-authorized activities and generally occur at the same time and place as the management activity or action causing the impact. For example, for the action of building a road, a direct adverse impact is surface disturbance. Surface disturbance is the impact (the effect) of heavy equipment (the cause) removing existing vegetation as it grades the proposed road location. Indirect impacts often occur at some distance or time from the action. In the example above, an indirect impact could occur days after the surface is disturbed and some distance from the disturbance. Heavy precipitation following vegetation removal and ground disturbance could erode soil and transport sediment into streams. Therefore, the impact to stream water quality would be an indirect adverse impact.
Short- or Long-term Impacts. Where applicable, this chapter describes the short-term or long-term aspects of impacts. For purposes of this RMP, short-term impacts occur during or after the activity or action and may continue for up to 5 years. For example, for the action of a prescribed fire, a short‐term adverse impact is loss of vegetative cover. Long-term impacts occur beyond the first 5 years, an approximation of the time required to restore or reclaim an area following surface disturbance. Long-term beneficial impacts of prescribed fire include diversifying vegetation structure and restoring fire-adapted ecosystems to prevent larger, more damaging wildland fires.
This section describes the methods and assumptions used in the impact analysis for each resource or resource use. Due to the programmatic and strategic nature of the RMP alternatives, the timing and specific location of project-specific actions that could affect resource values are not defined. Moreover, the relationship between cause (future actions) and effect (impact on resources) is not always known or quantifiable. For these reasons, alternative analyses are both qualitative and quantitative, and based on a series of assumptions. The methods and assumptions listed for each section, and in the general assumptions presented below, provide a basis for the conclusions reached in this chapter.
The summary section for each resource program briefly discusses the overall impacts resulting from implementation of the alternatives and compares the alternatives in terms of their anticipated impact intensity (from greatest to least). The summary section compares impacts among the Action Alternatives (alternatives B, C, D) and the No Action Alternative (Alternative A). In some cases, there are no discernable differences in impacts among the alternatives.
The detailed analysis of alternatives describes how each alternative could affect baseline conditions of individual resources in the Bighorn Basin planning area (Planning Area). The alternatives analyses typically describe impacts grouped into broad topic areas and in the following order: surface disturbance, resource uses, special designations, resources, and proactive management actions. Proactive management actions include management actions included to protect or enhance the resource of interest. For example, proactive management actions for soils include requiring topsoil salvage and segregation for all surface-disturbing activities. If an impact analysis does not discuss the effect of a particular allowable use or management action on a given resource, it is because the BLM does not expect impacts or expects impacts to be minimal, or the anticipated impact is outside the scope of this analysis, as described in Chapter 1 of this document.
Cumulative impacts combine the past and present impacts encompassed in existing conditions described in Chapter 3 with the anticipated incremental impacts of alternatives described in the sections of this chapter and the impacts of reasonable foreseeable actions. The Cumulative Impacts section, which appears at the end of this chapter, also includes anticipated incremental impacts of non-BLM reasonable foreseeable actions.
The list below identifies assumptions common to all alternatives and all resources. Individual resource sections list assumptions unique to specific resources and resource uses.
Key planning issues identified in Chapter 1 provide the focus for the scope of impact analyses in this chapter.
In general, the BLM considers adverse impacts described in this chapter important if they result from or relate to the key planning issues described in Chapter 1 and their context or intensity (see Glossary ) indicate that they may result in impacts to public health and safety; a potential for violating legal standards, laws, or protective status of resources; or potential impacts to unique resources.
The analysis of impacts focuses on the anticipated incremental and meaningful impact of management actions and allowable uses proposed for each alternative. The description of existing conditions in Chapter 3 encompasses the impacts of past and present actions.
The purpose of the comparison of impacts among resources is to provide an impartial assessment to inform the decision maker and the public. The impact analysis does not imply or assign a value or numerical ranking to impacts. Actions resulting in adverse impacts to one resource may impart a beneficial impact to other resources.
When adverse impacts to other resources would occur, "on a case-by-case basis" means an action would only be allowed when impacts can be adequately mitigated consistent with other resource goals and objectives.
For impact analysis, short-term is generally defined as being less than 5 years and long-term as being greater than 5 years, unless otherwise noted for a specific resource; the life of the plan is assumed to be 15 to 20 years.
Existing state and federal environmental legislation and regulatory programs would remain relatively unchanged and in effect (i.e., analyses are based on current, rather than projected, future regulations).
To the extent possible and within legal and regulatory parameters, BLM management and planning decisions will be consistent with the planning and management decisions of other agencies, state and local governments, and Native American tribes with jurisdictions intermingled with the Planning Area.
Funding would be available to implement the alternatives described in Chapter 2.
The BLM would implement any of the alternatives in compliance with standard practices, best management practices (BMPs) (Appendix L), guidelines for surface-disturbing activities, and mitigation guidelines (Appendix H). The practices and guidelines included in Appendices H and L are a component of each alternative. Appendix H lists standard practices used in the Planning Area to mitigate adverse impacts caused by surface-disturbing activities (Wyoming BLM Mitigation Guidelines for Surface-disturbing and Disruptive Activities).
The Glossary (in Volume 3) defines surface-disturbing activities employed in the analyses. The BLM typically describes surface disturbance in terms of the total acres of short- or long-term disturbance from BLM actions, as shown in Table 4–1. Appendix T lists projected surface disturbance associated with individual reasonable foreseeable actions, including surface disturbance for new wells that are subsequently abandoned and reclaimed. For analysis purposes, the acreage of surface disturbance for new well pads and associated facilities varies with the fields, areas, structures, and formations developed, and assumes there will be one well pad per producing well. See Appendix H for the Wyoming BLM Mitigation Guidelines for Surface-disturbing and Disruptive Activities.
Concentrated livestock and native ungulate grazing, off-highway vehicle (OHV) use, and fire may remove vegetation and expose the soil surface leading to increased erosion.
Ongoing natural and human-caused changes to vegetation communities would continue in the absence of management intervention.
Vegetation treatments would be performed only in habitats that would benefit from such treatments.
The successful application of treatments to specific areas/watersheds would result in the maintenance or reestablishment of the desired range of conditions for the major vegetation communities in approximately the desired proportions.
Mitigation requirements would prevent or limit direct impacts associated with land use activities, including reclamation of land after completion of the activity.
For purposes of analysis, it is assumed that lands identified for withdrawal under each alternative would be withdrawn. Where not otherwise noted, discussions of areas withdrawn under the various alternatives are assumed to include existing withdrawals, existing withdrawals where the withdrawals would be extended, and areas that would be recommended for withdrawal. While an RMP can make recommendations, closing areas to operation of the mining laws (i.e., withdrawing) occurs outside of the RMP revision process. Table 4-13 identifies existing and proposed withdrawals under the alternatives.
An oil and gas lease grants the lessee the “right and privilege to drill for, mine, extract, remove and dispose of all oil and gas deposits” in the leased lands, subject to the terms and conditions incorporated in the lease (BLM Form 3100-11, Lease for Oil and Gas). Because the Secretary of the Interior has the authority and responsibility to protect the environment within federal oil and gas leases, the BLM imposes restrictions on the lease terms.
The United States (U.S.) Court of Appeals for the D.C. Circuit in Sierra Club v. Peterson, 717 F.2d. 1409 (D.C. Cir. 1983) found that “on land leased without an NSO stipulation, the DOI (U.S. Department of the Interior) cannot deny the permit to drill…once the land is leased the DOI no longer has the authority to preclude surface-disturbing activities even if the environmental impact of such activity is significant. The Department can only impose mitigation upon a lessee who pursues surface-disturbing exploration and/or drilling activities.” The court goes on to say “notwithstanding the assurance that a later site-specific environmental analysis will be made, in issuing these leases the DOI has made an irrevocable commitment to allow some surface-disturbing activities, including drilling and road building.”
Provisions in leases that expressly provide Secretarial authority to deny or restrict development in whole or in part depend on an opinion provided by the U.S. Fish and Wildlife Service (USFWS) regarding impacts to endangered or threatened species or habitats of plants and animals listed or proposed for listing. If the USFWS concludes that the development likely would jeopardize the continued existence of any endangered or threatened plant or animal species, then the development may be denied in whole or in part.
The BLM cannot predict the exact locations of future surface-disturbing activities at the RMP level. Unless a management action for a vegetation type specifies otherwise, surface-disturbing activities are assumed to occur in vegetation types in proportion to their availability within the Planning Area. Impact acreage for vegetation types are not absolute, but serve as a relative comparison among alternatives.
Table 4.1. Total Projected Surface Disturbance from BLM Reasonable Foreseeable Actions in the Bighorn Basin Planning Area
| Action | Alternative A | Alternative B | Alternative C | Alternative D (Agency Preferred) |
| Total Acres Short-Term Disturbance from BLM Actions | 136,415 | 73,919 | 245,783 | 140,508 |
| Total Acres Reclaimed from BLM Actions | 120,704 | 63,037 | 204,238 | 122,065 |
| Total Acres Long-Term Disturbance from BLM Actions | 15,710 | 10,882 | 41,545 | 18,443 |
Source: Appendix T
BLM Bureau of Land Management