CHAPTER 3 AFFECTED ENVIRONMENT Chapter 3 describes the physical, biological and human resources which may be affected by implementation of any of the proposed alternative programs for oil and gas leasing. The study area encompasses portions of the Uinta and Ashley NFs, rated as having a high to medium potential for oil and gas resources. Approximately 203,670 acres are within the Ashley NF and 197,270 acres are within the Uinta NF for a total of approximately 400,940 acres in the study area. Included within this study area are the south unit of the Duchesne Ranger District (Ashley NF) and an area to the west and south of Strawberry Reservoir on the Uinta NF. Information presented in this chapter describes the existing conditions and is used to determine and compare the anticipated effects of various alternatives. Twelve separate sections are presented to address key issues identified during public scoping and by Forest Service resource specialists. Each section gives (1) a general description of the resource, (2) information on Forest Service management direction as given in the Ashley and Uinta NF Land and Resource Management Plans (Forest Plans), (3) identification of the issue(s) associated with the resource, and 4) if needed, a further discussion on specific sensitive components of the resource which were identified as of special concern. 3.1 GEOLOGY/MINERALS This section provides a description of the existing condition of and the issues related to geology and minerals that could be affected by oil and gas leasing in the Western Uinta Basin. Geology as it relates to groundwater is discussed in Section 3.2, Watershed Resources. The reader is referred to the glossary (Chapter 8) for an explanation of geologic terms used in this section. 3.1.1 General Description The study area is located in portions of the Tavaputs Plateau of the Colorado Plateau province and the adjacent Wasatch Hinterlands sub-section of the Middle Rocky Mountains province (Stokes 1986). Most of the Ashley NF portion of the study area lies within the 3-1 Book Cliffs-Roan Plateau sub-section and most of the Uinta NF portion of the study area lies within the southern end of the Wasatch Hinterlands sub-section (Stokes 1986). The dividing line between the two physiographic sub-sections is roughly defined by the southwest-northeast trending Willow Creek Ridge and the eastern drainage divide for Tie Fork Creek. Cenozoic and Mesozoic rock formations are exposed at the surface within the study area (State of Utah Geologic and Mineral Survey 1980). The predominate Cenozoic units in descending order are the Uinta Formation, Green River Formation, Wasatch/Colton Formation, and North Horn Formation. The Uinta and Green River formations form the upland plateaus surfaces and canyon walls which comprise much of the study area. Exposed Wasatch/Colton, North Horn, Price River, Flagstaff, and the mesozoic rocks (including in descending order the Mesaverde, Morrison, Curtiss, Entrada sandstone, Carmel, Nugget sandstone, and Chinle shale-Garten sandstone) are present only below Strawberry Ridge in the incised canyons of Diamond Fork Creek and its tributaries and Spanish Fork Canyon. Strata in the study area range in age from Precambrian to Tertiary (Eocene). Stratigraphic units from the Ordovician, Devonian, Silurian, and later Tertiary periods are missing from the record (State of Utah Geologic and Mineral Survey 1980). The stratigraphic column is characterized by Precambrian metasedimentary and siliciclastic rocks, Cambrian sandstone, shale, and carbonate rocks, Late Paleozoic carbonates and sandstones, Mesozoic sandstones and shales, and Cenozoic sandstones, shales, and conglomerates. Paleozoic and Precambrian rocks are present in the subsurface only. The structural features east of Strawberry Ridge are associated with Laramide phase deformation of paleocene and eocene age. The study area is located on the south flank of the asymmetrical synclinal Uinta Basin downwarp which is linked to the uplift of the Uinta Mountains north of the study area. Beds dip northeastward at approximately 10 degrees. Northeast trending anticlinal noses and faults are present in the Strawberry Ridge area. The Strawberry Thrust is the main structural feature that controls stratigraphy in the western end of the study area. Much of the Wasatch Range Fault block is located on the upper plate of the west dipping Strawberry Thrust sheet. The Strawberry Thrust is part of the Sevier orogenic belt and is mid-Jurassic to Eocene in age. Displacement along the fault 3-2 is often more than 5 miles. Displacement of the thrust sheet in the study area has created folds within the strata of the sheet. Two folds, the Thistle Dome Anticline and the Diamond Fork Anticline exist within the study area (Walton 1954). Several oil and gas exploration wells have been drilled on these anticlinal features. 3.1.2 Forest Plan Management Direction For geologic resources, both the Ashley and Uinta Forest Plans address only the minerals and energy component. The Ashley Forest Plan defines the following goals for the management of the resources: • Provide orderly exploration, development, and production of mineral and energy resources consistent with the use and protection of the other resource values. The Uinta Forest Plan defines the following goals for the management of their mineral/energy resources: • Manage activities related to energy minerals including oil and gas in conformance with objectives of the Forest Plan and in accordance with mineral laws, regulations, and policies. • Based on a valid "purpose and need" for energy production and transmission, cooperate with energy companies, private individuals, and other government agencies to provide space for facilities consistent with laws, regulations, and policies established for the protection and management of National Forest resources and uses. 3.1.3 Issues The public scoping process produced three issues related to geology/minerals (see Section 1.8): Issue 6: The effects of restrictive stipulations and mitigation measures on oil and gas exploration and development 3-3 Issue 7: The effects of oil and gas leasing and subsequent activities on soils and geologic formations Issue 13: The effects of oil and gas exploration and development on other mineral resources and production Specific areas of concern summarized in Issue 6 are the possible development and application of stipulations/mitigations that would be restrictive to oil and gas development. This issue is addressed as part of the overall analysis presented in this EIS. Issue 7 summarizes concerns regarding effects of oil and gas activities on the stability of soil and geologic materials, and in turn, the hazards posed by unstable soils and/or geologic materials to potential oil and gas development activities/facilities. These concerns are addressed in the subsequent Section 3.2 Watershed Resources of this EIS. Issue 13 summarizes concerns raised over the potential effects of oil and gas development on other mineral development and exploration. In response to the above scoping issues for this leasing analysis, the presence of minerals (includes oil and gas) and accessibility to mineral resources from both the regulatory and technical capability aspects were identified as sensitive resource components related to geology/minerals and are described in the following section. 3.1.4 Sensitive Resource Component(s) Mineral Resources Federally owned mineral resources are separated by laws and regulations into categories of locatable, saleable, and leasable. Within the Western Uinta Basin study area, no specific mineral development proposals for locatable minerals (i.e., precious metals, copper, and molybdenum) or saleable minerals (i.e., sand, gravel, and stone) have been identified. Several sites within the study area have likely provided gravel for FS road and facilities construction and maintenance. The principal minerals of interest within the study area are oil and gas deposits. 3-4 The existence of geologic formations and structures that are important to the formation and storage of hydrocarbons, particularly natural gas, make the study area potentially attractive for exploration and development by the petroleum industry. The Uinta Basin play is the principal prospective oil and gas play in the study area. This play comprises approximately 380,000 acres of high potential areas within the approximately 400,940-acre study area. An area of moderate potential is located along the western edge of the study area on the Uinta NF (Figure 3-1). Detailed geologic and petroleum information are provided in the project files (Kaldenback 1991a and b). Slipsheet for Figure 3-1 3-5 Historic Activity. Oil and gas production in or near the study area is found in two producing fields and one shut-in field. Production from the Gulf #1 Chokecherry in 1959 started the first flurry of drilling activity in the study area which lasted until 1966. Two of the oil wells produced a cumulative total of 9,700 barrels of oil before they were abandoned. Subsequently, starting in 1976, five additional wells were drilled which showed proven gas production potential from the Green River Formation. These wells, known collectively as the Sowers Canyon field are currently shut-in (see Figure 1-2). This field is awaiting the construction of a gathering system and sales pipeline before production becomes viable. Other production near the study area includes the Altamont-Bluefield field in the center of the Uinta Basin. Production is from naturally fractured reservoirs in the Tertiary Wasatch and Green River Formations at depths down to 17,000 feet. Two miles north of the study area, the Brundage Canyon Field has produced over one million barrels of oil and 1.6 million cubic feet (Mmcf) of gas from Green River Formation sandstones. The Duchesne field is located approximately 10 miles north of the Sowers Canyon area, southwest of the city of Duchesne. Production is from the Uinta, Green River, and Wasatch Formations. Fluids. Hydrocarbon accumulations in the eastern portion of the study area, including the Sowers Canyon area, are usually controlled by stratigraphic traps.