07 Gasco Chapter 3. Affected Environment
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CHAPTER 3.0 AFFECTED ENVIRONMENT Gasco Final EIS Chapter 3. Affected Environment 3.1 Introduction 3.0 AFFECTED ENVIRONMENT 3.1 INTRODUCTION This chapter presents the potentially affected existing environment (i.e., the physical, biological, social, and economic values and resources) of the impact area as identified in the Interdisciplinary Team Analysis Record Checklist (Appendix A) and presented in Chapter 1 of this assessment. This chapter provides the baseline for comparison of impacts/consequences described in Chapter 4. Because of small discrepancies in geographic information system (GIS) layers used to describe various project area components of the environment, some acreages and lengths may not always add to exactly the total described. These discrepancies are normal when working with data from a variety of sources and do not affect the overall accuracy of the data and analyses presented. 3.1.1 GENERAL SETTING The project area is located in the Uinta Basin—part of the Colorado Plateau Province in northeastern Utah. The Uinta Basin is bordered to the north by the Uinta Mountain Range, which is the only major east/west-oriented mountain range in the United States. The eastern and southern boundary of the basin is formed by the Tavaputs Plateau of the Book Cliffs, and the western boundary is formed by the Wasatch Mountains. The center of the basin lies at an elevation between 5,000 and 5,500 feet. The vegetation within the Uinta Basin is primarily shrub/scrub, with some areas of evergreen forest, grasslands, and barren land. The average annual precipitation for the Uinta Basin is less than 8.5 inches. However, the basin contains a number of rivers and streams. The southern slopes of the Uintas are drained by Current Creek, the Duchesne River, Lake Creek, the Uinta River, Ashley Creek, and Big and Little Brush creeks. The southern portion of the basin contains fewer streams that are much smaller in volume than those in the northern region. The Green River flows through the Uintas at Split Mountain and across the Uinta Basin in a southwesterly direction. 3.1.2 RESOURCES OF CONCERN AND OTHER RESOURCES BROUGHT FORWARD FOR ANALYSIS A total of 31 resources of concern identified in the Interdisciplinary Team Analysis Record Checklist (Appendix A) are brought forward for analysis in Chapter 4: air quality; existing areas of critical environmental concern (ACECs); potential ACECs; cultural resources; environmental justice; Native American religious concerns; threatened, endangered or candidate animal species; threatened, endangered or candidate plant species; wastes (hazardous or solid); county transportation plan; floodplains; lands/access; rangeland health; invasive and non-native species; vegetation, including species status plants; water quality; wetlands/riparian zones; proposed Wild and Scenic Rivers (WSRs); livestock grazing; woodlands/forestry; vegetation; fish and wildlife, including special status species; soils; recreation; visual resources; geology/minerals/energy production; paleontology; fuels/fire management; socioeconomics; wilderness characteristics; and waters of the United States. Some of the resources of concern described in the checklist have been combined into single sections for purposes of analysis, so a total of 16 resource sections is presented below. Each of the identified resources of concern is described in the following sections. 3-1 Gasco Final EIS Chapter 3. Affected Environment 3.2 Air Quality 3.2 AIR QUALITY 3.2.1 INTRODUCTION Regional air quality is influenced by a combination of factors including climate, meteorology, the magnitude and spatial distribution of local and regional air pollution sources, and the chemical properties of emitted pollutants. Within the lower atmosphere, regional and local scale air masses interact with regional topography to influence atmospheric dispersion and transport of pollutants. The following sections summarize the climatic conditions and existing air quality within the project area and surrounding region. 3.2.2 CLIMATE The project area is located on the West Tavaputs Plateau in the southern foothills of the Uinta Basin; a semiarid mid-continental climate regime typified by dry windy conditions and limited precipitation. The Uinta Basin is bordered by the Wasatch Range to the west, which extends north and south through the middle of the State, and the High Uinta Mountains to the north, which extend east and west through the northeast portion of the State. Elevation of the project area ranges from 4,600 feet above mean sea-level (famsl) in the eastern portion to over 8,000 famsl in the western portion. 3.2.2.1 TEMPERATURE AND PRECIPITATION The closest climate measurements to the project area were recorded at Nutters Ranch and at Sunnyside, Utah (1963–1986). The Nutters Ranch station is located one mile south of the southwest corner of the project area at an elevation of 5,790 famsl (WRCC 2007). The Sunnyside station is located 18 miles southwest of the southwest corner of the project area at an elevation of 6,670 famsl (WRCC 2007). Table 3-1 and Table 3-2 summarize the mean temperature range, mean total precipitation, and mean total snowfall by month. Table 3-1. Temperature, Precipitation, and Snowfall at Nutters Ranch, Utah (1963–1986) Average Temperature Average Total Average Total Season Month Range Precipitation Snowfall (in degrees Fahrenheit) (inches) (inches) March 22.4–51.6 1.2 6.1 April 29.8–61.4 1.0 4.1 Spring May 38.5–71.9 1.1 0.6 Total Spring Average 30.3–61.6 3.3 10.8 June 46.4–81.3 0.9 0.0 July 53.6–87.7 1.2 0.0 Summer August 51.3–85.4 1.4 0.0 Total Summer Average 50.4–84.8 3.4 0.0 September 42.2–77.1 1.1 0.5 October 31.2–65.3 1.2 1.3 Fall November 20.1–49.4 0.7 5.4 Total Fall Average 31.2–63.9 3.0 7.2 3-2 Gasco Final EIS Chapter 3. Affected Environment 3.2 Air Quality Table 3-1. Temperature, Precipitation, and Snowfall at Nutters Ranch, Utah (1963–1986) Average Temperature Average Total Average Total Season Month Range Precipitation Snowfall (in degrees Fahrenheit) (inches) (inches) December 9.2–36.6 0.9 12.4 January 6.4–35.3 0.6 6.1 Winter February 11.5–42.0 0.5 9.0 Total Winter Average 9.0–38.0 1.9 27.6 Total Annual Average 30.2–62.1 11.6 45.6 Source: Western Regional Climate Center (WRCC) 2007. Data collected at Nutters Ranch, Utah from 1963 to 1986. Table 3-2. Temperature, Precipitation, and Snowfall at Sunnyside, Utah (1963–1986) Average Temperature Average Total Average Total Season Month Range Precipitation Snowfall (in degrees Fahrenheit) (inches) (inches) March 22.4–44.9 1.3 6.8 April 30.0–54.8 1.0 2.6 Spring May 39.3–64.8 1.2 0.3 Total Spring Average 30.5–54.8 3.6 9.8 June 48.3–77.2 0.8 0.0 July 55.3–84.4 1.2 0.0 Summer August 53.5–82.2 1.5 0.0 Total Summer Average 52.4–81.3 3.5 0.0 September 45.2–72.5 1.7 0.0 October 34.9–59.7 1.4 0.5 Fall November 24.3–45.9 0.9 2.8 Total Fall Average 34.8–59.4 4.1 3.3 December 15.7–35.9 0.7 6.8 January 13.8–33.9 0.8 9.2 Winter February 18.7–40.0 1.0 7.4 Total Winter Average 16.0–36.6 2.6 23.4 Total Annual Average 30.2–62.1 11.6 45.6 Source: WRCC 2007. Data collected at Sunnyside, Utah from 1963 to 1986. 3-3 Gasco Final EIS Chapter 3. Affected Environment 3.2 Air Quality Prevailing large-scale westerly air masses originating from the Pacific Ocean are typically interrupted by the western mountain ranges before reaching the Uinta Basin. As a result, the lower elevations of the Uinta Basin receive relatively slight amounts of precipitation. The higher elevations of the area generally receive more favorable amounts of precipitation. The annual mean precipitation at Nutters Ranch is 11.6 inches, and ranges from a minimum of 6.4 inches recorded in 1974, to a maximum of 24.8 inches recorded in 1965. On average, February is the driest month with a monthly mean precipitation of 0.5 inches, and August is the wettest month with a monthly mean precipitation of 1.4 inches. The annual average snowfall is 45.6 inches. December, January, February, and March are the snowiest months. A maximum annual snowfall of 102 inches was recorded in 1965. The surrounding area has an annual mean temperature of 46°F. However, abundant sunshine and rapid nighttime cooling result in a wide daily range in temperature. Wide seasonal temperature variations typical of a mid-continental climate regime are also common. Average winter temperatures range from 9°F to 38°F, while average summer temperatures range from 50°F to 85°F. Recorded daily extreme temperatures are minus 25°F in 1971 and 100°F in 1976. 3.2.2.2 WINDS AND ATMOSPHERIC STABILITY The transportation and dilution of air pollutants are primarily a function of wind speed and direction. Winds dictate the direction in which pollutants are transported. As wind speed increases, the dispersion of emitted pollutants also increases, thereby reducing pollutant concentrations. Wind data within the project area have not been directly measured. Local terrain effects will influence the wind profiles specific to the project area. However, representative wind speed and direction data for the area are available at the Canyonlands National Park for the years 1995, 1996, 1997, 1998, and 1999 as part of the Clean Air Status and Trends Network (CASTNET) operated by the U.S.