This analysis focuses on the impacts to mineral materials as a whole in the Planning Area. However, because sand and gravel are the principal salable minerals found in commercial quantities in the Planning Area, wherever possible, this analysis describes specific impacts to the disposal of sand and gravel. Acreages of occurrence potential of other mineral materials were not available at the time of analysis.
The BLM based this analysis on occurrence potential (referred to as “potential” in this analysis) for minerals identified in the Solid Mineral Occurrence and Development Potential Report, Bighorn Basin Resource Management Plan Revision Project (BLM 2009c). “Potential” refers to the potential for or the presence (occurrence) of a concentration of one or more mineral resources. It does not refer to or imply potential for development and/or extraction of the mineral resource(s). It does not imply that the potential concentration is or may be economic (i.e., could be extracted profitably). The mineral potential classification system is based on the level of potential and the level of certainty of data supporting the possible existence of minerals. The system classifies level of potential as No (O), Low (L), Moderate (M), High (H), and Not Determined (ND). The system classifies level of certainty as A (lowest certainty), B, C, and D (highest certainty). See Glossary or the Solid Mineral Occurrence and Development Potential Report, Bighorn Basin Resource Management Plan Revision Project (BLM 2009c) for more information on the mineral potential classification system.
Methods and assumptions used in this impact analysis include the following:
Existing BLM-approved mineral material sites will remain open to mineral materials disposal.
The potential for occurrence of mineral materials exists across the Planning Area.
New mineral materials disposal sites in areas open to mineral materials disposal will be subject to site‐specific analysis prior to approval.
In most cases, demand for mineral materials during the planning period will be directly proportional to the rate of other resource development in a given area. New disposals could be requested to establish closer proximity to development areas, since generally, mineral materials are of low unit value compared to their cost to transport them from source to market.
The BLM has discretionary authority to permit mineral materials disposal. It may choose to approve or disapprove such sales or permits, on a case-by-case basis, within the Planning Area.
Common varieties of mineral materials are considered salable under the Materials Act of 1947. Uncommon varieties of such minerals may be locatable and subject to administration under the mining law, as amended.
Area closures and surface and timing restrictions could result in adverse impacts by reducing access to mineral materials.
Known sand and gravel deposits (Map 24), with a rating of high (H) and a certainty level of D, occur particularly along major drainages throughout the Planning Area and are depicted on Map 15 of the Solid Mineral Occurrence and Development Potential Report, Bighorn Basin Resource Management Plan Revision Project (BLM 2009c). There are about 882,618 acres of sand and gravel with known (high) occurrence potential in the Planning Area. Refer to the Solid Mineral Occurrence and Development Potential Report, Bighorn Basin Resource Management Plan Revision Project (BLM 2009c) for additional, detailed maps of mineral materials potential within the Planning Area.
Sand and gravel deposits with an occurrence potential rating of moderate and certainty level of C (M/C) exist in small quantities on the western portion of the Planning Area. There are about 6,230 acres of sand and gravel with moderate occurrence potential in the Planning Area. The remainder of the Planning Area has a rating of low (L) with a certainty level of C (L/C).
Sand and gravel deposits, which are likely to be developed, appear to be available in sufficient quantity and quality to sustain moderate to large increases in local and regional needs.
Scoria (clinker) may be found associated with coalbeds which occur in the Mesaverde, Meeteetse, and Fort Union formations. Potential for the occurrence of scoria in the vicinity of these formations was rated as high (H) in the Gebo, Grass Creek, and Meeteetse coal fields with a certainty level of C (H/C).
The potential for future commercial mining of scoria (clinker) from BLM-administered lands or mineral estate in the Planning Area is estimated to be moderate wherever these resources may be found and available.
Known common-variety limestone within the Madison Formation has an occurrence potential of high (H) with certainty of D (H/D). Such occurrences are located along parts of the perimeter of the Planning Area. In the remainder of the Planning Area, the potential for limestone occurrence (not including limestone fragments found in colluvium, terrace, or alluvial deposits), is rated as low (L) with a certainty level of C (L/C).
The development potential for continued and future commercial mining of common-variety limestone from federal mineral estate in the Planning Area is estimated to be moderate to high.
The potential for the occurrence of common clay is rated as moderate (M) with a certainty level of C (M/C).
The potential for future commercial mining of common clay from federal mineral estate in the Planning Area is estimated to be low to moderate.
Throughout the Planning Area, there exists weathered rocks of sandstone, siltstone, limestone, or granite covered in part with lichens. Sandstones and siltstone outcrops in the Morrison, Cloverly, Mesaverde, Lance, and Fort Union formations are commonly considered to be moss rock if they are partially adorned with colorful lichens. In these formations, there is a high (H) potential for moss rock with a certainty level of D or C (H/D or H/C). Potential for moss rock occurrence in other parts of the Planning Area is rated as low (L) to moderate (M) with a certainty level of B (L/B to M/B).
The potential for future commercial development of moss rock from federal mineral estate in the Planning Area is estimated to be high in areas where resources exist, and are available for disposal.
In the Planning Area, flagstone is a mineral material that is typically found in the Chugwater, Cloverly, Sundance, Mesaverde, and Fort Union formations. In outcrops of the lowermost Sundance Formation, occurrence potential for flagstone is high (H) with a certainty level of C (H/C). Elsewhere in the Planning Area, the potential for flagstone is rated as low (L) to moderate (M) with a certainty level of C (L/C to M/C).
The potential for future commercial development of flagstone from federal mineral estate in the Planning Area is estimated to be high in areas where flagstone resources exist, and are available for disposal.
Potential for petrified wood to be found mixed in with Quaternary terrace or alluvial deposits, after having been transported from the Absaroka Mountains, is moderate (M) to high (H) with a certainty level of C (M/C to H/C).
The potential for future commercial development of petrified wood from federal mineral estate in the Planning Area is estimated to be low.