Montana Snowbowl Expansion FEIS

CHAPTER 3 AFFECTED ENVIRONMENT 3.1 INTRODUCTION This chapter describes the existing environment that may be affected by Alternative A (No Action) and Alternative B (Proposed Action). The affected environment is described according to two broad categories: physical/biological environment and the human environment. The physical/biological environment includes natural resources such as geology and soils, water, vegetation, wildlife, fisheries, and air quality. The human environment includes human- influenced resources such as facilities and transportation, cultural resources, recreation, visual resources, and economics. The standards, methods, and analysis areas specific to each resource are described in the introductions to each resource. 3.2 GEOLOGY AND SOIL RESOURCES 3.2.1 Standards Applicable to Geology and Soil Resources The Forest Plan (USDA 1986) provides guidance for all land managed by the LNF and specific guidance for individual MAs affected by the Proposed Action. General geology and soil resource standards are identified for the LNF. The geology and soil standard that applies to the proposed project states that “All management practices will be designed or modified as necessary to maintain land productivity.” Regional Soil Quality Standards “apply to lands where vegetation and water resource management are the principal objectives…” The standards do not apply to intensively developed sites such as mines, developed recreation sites, administrative sites, or rock quarries (R1 Supplement 2500-99-1, Section 2554.1:3). Management direction for geologic resources related to mineral development is in MAs 8, 16, and 25 of the Forest Plan. The Forest Plan states that mineral materials permits will not be issued for MA 8 (page III-24). MA 16 and MA 25 standards state that mineral resource permits will be issued on a case-by-case basis. Applicable oil and gas prescriptions recommended for inclusion as oil and gas stipulations are identified for each MA. No soil standards are listed for MA 8. In 1996, Section 701(j), Title VII, Division I of the Omnibus Parks and Public Lands Management Act (Omnibus Parks and Public Lands Management Act of 1996) withdrew all NFS lands in permitted ski area boundaries from mineral entry, subject to valid existing rights. All NFS lands within the boundaries of ski area permits are withdrawn from all forms of appropriation under the mining laws and from disposition under all laws pertaining to mineral and geothermal leasing (Drake 1997). The withdrawal continues for the full-term of the permit, including any modification, reissuance, or renewal of such permit. Unless otherwise requested by the Secretary, the withdrawal is automatically cancelled upon expiration or other termination of the permit. The MDEQ regulates the discharge of stormwater into state waters. The Proposed Action would require an NPDES stormwater discharge permit because more than 5 acres (total) would be Final EIS 3-1 Montana Snowbowl Chapter 3 Affected Environment disturbed for utility installation, construction of lift infrastructure, and grading of ski trail/road intersections and bike trails. Additional standards and regulations related to sediment and water quality are in Section 3.3, Water Resources. 3.2.2 Geology and Soil Resources Methods This section was compiled using published information, site visits to the project area, and contacts with LNF and MSB personnel. Information about the proposed project was obtained from the MSB MDP (2004) and from conversations with the MSB general manager and owner. Similar projects at Bridger Bowl, 49 Degrees North, Lookout Pass, and Discovery ski areas were reviewed. Guidance was obtained from the Forest Plan (MA descriptions), from applicable laws and regulations, and from direct communication with LNF soil specialists. Specific literature was reviewed and incorporated to document mitigation measures and their effectiveness. 3.2.3 Geology and Soil Resources Analysis Area The area of analysis for direct, indirect, and cumulative effects on geology and soil resources is the proposed expansion SUP area on TV Mountain. 3.2.4 Geology and Soil Resources Affected Environment 3.2.4.1 Geology Affected Environment The MSB is located in the Rocky Mountain physiographic province. TV Mountain is composed of Precambrian-age argillite, siltite, and quartzite that underlies much of northwestern Montana. Drainages below the mountain and south of the proposed expansion area are filled with Tertiary and Quaternary-age sediments. Mineral Potential No economic mineralization has been discovered in the proposed expansion area, and no active mining claims are present. Geologic Hazards The MSB and the proposed expansion area on TV Mountain are located in a region with low seismicity levels. The U.S. Geological Survey national hazard map (USGS 2006) shows that MSB and proposed expansion area are in a relatively low seismic hazard area. 3.2.4.2 Soil Resources Affected Environment Soil features in the proposed expansion area are closely related to the geology described above. Weathering, erosion, and stream activity have modified these rock materials into the current soils. Loess (wind-deposited dust) especially has been added to the surface soil. Most of this loess fell as volcanic ash, mainly from the eruption of Mt. Mazama (approximately 7,000 years ago). Soil resources in the proposed expansion area were mapped by the U.S. Department of Agriculture (USDA) Natural Resources Conservation Service as part of the Missoula County Final EIS 3-2 Montana Snowbowl Chapter 3 Affected Environment Soil Survey (NRCS 1990) and by the LNF as part of the Land Systems Inventory (Sasich and Lamote-Hagen 1989). Table 3-1 lists the land-type mapping units that comprise the proposed expansion area. Table 3-1. Land-type Mapping Units in the Proposed Expansion Area Map Map Unit Management Limitations Unit Components Soils Setting Related to this Project Skidtrails and firelines have a Moderate relief 30QE Andic Cryochrepts moderate erosion hazard. Native mountain slopes road surfaces can be dusty. Andic Dystric Eutrochrepts- Moderate relief 30QG Native road surfaces can be dusty. Dystric Eutrochrepts Complex mountain slopes Skidtrails and firelines have a 32QA Andic Cryochrepts Broadly convex ridges moderate erosion hazard. Native road surfaces can be dusty. Skidtrails and firelines have a 64QE Andic Cryochrepts Steep mountain slopes moderately low erosion hazard. Native road surfaces can be dusty. Andic Dystric Eutrochrepts- Skidtrails and firelines have a 64QG Steep mountain slopes Dystric Eutrochrepts Complex moderately low erosion hazard. Soils in the proposed expansion area are covered with a surface layer of partially decomposed organic matter including conifer needles and other plant parts. This layer is approximately 1 to 2 inches thick and protects the surface from raindrop impact and surface flow erosion. Soils are formed predominantly from bedrock that has weathered in place (residuum) or moved slowly downhill under the force of gravity (colluvium). The silt loam surface soil is volcanic ash- influenced loess that is 2 to 13 inches thick. This ash-influenced layer is thickest at the highest elevations, on northerly aspects, and in concave areas. The ash-influenced surface layer has a high moisture and nutrient retention capacity. The subsoil usually has a sandy loam or loam texture with a rock content ranging from about 25 percent in the upper subsoil to 70 percent in the lower subsoil. Soil depth is mostly very deep but is shallow to moderately deep near rock outcrops. Current soil issues within the proposed expansion area and existing SUP area are associated with erosion from roads and MSB facilities. Ratings discussed in this section are taken from the LNF Land Systems Inventory (Sasich and Lamote-Hagen 1989) unless otherwise noted. Landslide potential is rated low for all of these soils. Erodibility is rated moderate in the surface soil and low in the subsoil for all these soils. Revegetation potential is rated as good. A logging road on the hillslope above La Valle Creek (identified as FR 19080) serves as the boundary of the proposed SUP area (Figure 2-1). The distance between the road and the edge of the stream ranges from approximately 150 feet slope distance (at the switchback in the middle of Section 28) to over 2,000 feet in Section 5 (Figure 2-1). The switchback location was the site of a landing for a Forest Service timber sale in the late 1990s. During this activity, fill material was pushed over the side of the hill toward La Valle Creek to within approximately 50 feet of the creek edge. The fillslope now appears to be revegetating, and no ongoing erosion or mass movement can be observed. The surface on this Final EIS 3-3 Montana Snowbowl Chapter 3 Affected Environment road is stable due to vegetation and native gravel. No locations were observed where sediment was migrating from roads or timber harvest units either chronically or in the past. Erosion of a forest road surface depends on numerous factors (see Sugden and Woods 2007 for a review of the studies documenting these factors) including: Soil and parent material characteristics Road age Presence or absence (and depth) of aggregate surfacing Quality of surfacing Frequency and type of vehicle traffic Rainfall characteristics Amount of vegetative cover Roadbed slope Presence of vehicle ruts on the road surface Road maintenance regimen. On western Montana road slopes, the amount of time since last grading, roadbed gravel content, and precipitation were the main predictive variables in sediment yield from forest roads (Sugden and Woods 2007). La Valle Creek has a low slope (less than 2 percent for most of the segment nearest La Valle Creek) and moderately high native gravel content, and it appears from the grass growth on the road tread that it has been several years since the last grading. All of these characteristics offer evidence that the sediment yield from this road is low. Sediment travel distances below roads have been studied extensively in landscapes with granitic parent materials (Ketcheson and Megahan 1996) and in areas of high precipitation (Brake et al.

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