Antonito Southeast SEZ Analysis
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1 10 AFFECTED ENVIRONMENT AND IMPACT ASSESSMENT FOR 2 PROPOSED SOLAR ENERGY ZONES IN COLORADO 3 4 5 10.1 ANTONITO SOUTHEAST 6 7 8 10.1.1 Background and Summary of Impacts 9 10 11 10.1.1.1 General Information 12 13 The proposed Antonito Southeast solar energy zone (SEZ) has a total area of 9,729 acres 14 (39.4 km2). The SEZ is located in southeastern Conejos County, on the southern Colorado state 15 boundary with New Mexico (Figure 10.1.1.1-1). In 2008, the county population was 8,232, while 16 the surrounding six-county region in Colorado and New Mexico had a population of 116,511. 17 The largest nearby town of Alamosa (Alamosa County, Colorado), which had a 2008 population 18 of 8,745, is about 34 mi (55 km) to the north. Several small towns lie closer to the SEZ, with 19 Antonito, Colorado, a short distance to the northwest on U.S. 285. The area is served by the 20 San Luis & Rio Grande (SLRG) Railroad, while the San Luis Valley Regional Airport is in 21 Alamosa on U.S. 285. Santa Fe, New Mexico, is 110 mi (177 km) to the south. 22 23 An existing 69-kV transmission line is located about 4 mi (6 km) north of the SEZ. It is 24 assumed that a new transmission line would be needed to provide access from the SEZ to the 25 transmission grid (see Section 10.1.1.2). There were no pending solar project applications within 26 the SEZ as of February 2010. 27 28 The proposed Antonito Southeast SEZ is located in the south-central part of the San Luis 29 Valley, a high-elevation (approximately 8,000 ft [2,440 m]) basin between two large mountain 30 ranges. Other than a perlite processing plant approximately 0.75 mi (1.2 km) north-northwest of 31 the northwest corner of the proposed SEZ, there is little industrial development in the vicinity of 32 the SEZ. The area immediately to the north is used for agriculture, with irrigation water supplied 33 mainly from surface water sources. Land within the SEZ is undeveloped scrubland characteristic 34 of a high-elevation, semiarid, basin, which is currently used for grazing. Annual rainfall averages 35 about 8 in. (20 cm). 36 37 The proposed Antonito Southeast SEZ and other relevant information are shown in 38 Figure 10.1.1.1-1. The criteria used to identify the SEZ as an appropriate location for solar 39 energy development included proximity to existing transmission lines or designated corridors, 40 proximity to existing roads, a slope of generally less than 2%, and an area of more than 41 2,500 acres (10 km2). In addition, the area was identified as being relatively free of other types 42 of conflicts, such as U.S. Fish and Wildlife Service- (USFWS-) designated critical habitat for 43 threatened and endangered species, Areas of Critical Environmental Concern (ACECs), Special 44 Recreation Management Areas (SRMAs), and National Landscape Conservation System 45 (NLCS) lands (see Section 2.2.2.2 for the complete list of exclusions). Although these classes 46 of restricted lands were excluded from the proposed Antonito Southeast SEZ, other restrictions Draft Solar PEIS 10.1-1 December 2010 1 2 FIGURE 10.1.1.1-1 Proposed Antonito Southeast SEZ Draft Solar PEIS 10.1-2 December 2010 1 might be appropriate. The analyses in the following sections evaluate the affected environment 2 and potential impacts associated with utility-scale solar energy development in the proposed SEZ 3 for important environmental, cultural, and socioeconomic resources. 4 5 As initially announced in the Federal Register on June 30, 2009, the proposed Antonito 6 Southeast SEZ encompassed 9,598 acres (39 km2). Subsequent to the study area scoping period, 7 the boundaries were altered slightly to include some small higher slope areas internal to and at 8 the borders of the site. Although these higher slope areas would not be amenable to solar 9 development, inclusion in the SEZ would facilitate straightforward administration of the entire 10 area by the U.S. Department of the Interior (DOI) Bureau of Land Management (BLM). The 11 revised SEZ is approximately 131 acres (0.5 km2) larger than the original SEZ area as published 12 in June 2009. 13 14 15 10.1.1.2 Development Assumptions for the Impact Analysis 16 17 Maximum development of the proposed Antonito Southeast SEZ was assumed to be 18 80% of the total SEZ area over a period of 20 years, a maximum of 7,783 acres (31.5 km2). 19 These values are shown in Table 10.1.1.2-1, along with other development assumptions. Full 20 development of the Antonito Southeast SEZ would allow development of facilities with an 21 estimated total of 865 MW of electrical power capacity if power tower, dish engine, or 22 photovoltaic (PV) technologies were used, assuming 9 acres/MW (0.04 km2/MW) of land 23 required, and an estimated 1,557 MW of power if solar trough technologies were used, 24 assuming 5 acres/MW (0.02 km2/MW) of land required. 25 26 Availability of electric transmission facilities from SEZs to load centers will be an 27 important consideration for future development in SEZs. For the proposed Antonito Southeast 28 SEZ, the nearest existing transmission line is a 69-kV line 4 mi (6 km) north of the SEZ. It is 29 possible that a new transmission line could be constructed from the SEZ to this existing line, but 30 the 69-kV capacity of that line would be inadequate for 865 to 1,557 MW of new capacity (note 31 that a 500-kV line can approximately accommodate the load of one 700-MW facility). At full 32 build-out capacity, it is clear that substantial new transmission and/or upgrades of existing 33 transmission lines would be required to bring electricity from the proposed Antonito Southeast 34 SEZ to load centers; however, at this time the location and size of such new transmission 35 facilities are unknown. Generic impacts of transmission and associated infrastructure 36 construction and of line upgrades on various resources are discussed in Chapter 5. Project- 37 specific analyses would need to identify the specific impacts of new transmission construction 38 and line upgrades for any projects proposed within the SEZ. 39 40 For as complete an analysis of impacts of development in the SEZ as possible, it was 41 assumed that, at a minimum, a transmission line segment would be constructed from the 42 proposed Antonito Southeast SEZ to the nearest existing transmission line in order to connect the 43 SEZ to the transmission grid. This assumption was made without information on whether the 44 nearest existing transmission line would actually be available for connection of future solar 45 facilities and without assumptions about upgrades of the line. Establishing a connection to the Draft Solar PEIS 10.1-3 December 2010 TABLE 10.1.1.2-1 Proposed Antonito Southeast SEZ—Assumed Development Acreages, Maximum Solar MW Output, Access Roads, and Transmission Line ROWs Distance and Assumed Total Acreage Assumed Distance to Capacity of Area of and Assumed Maximum SEZ Nearest Nearest Transmission Distance to Nearest Developed Output for State, U.S., Existing Line ROW BLM-Designated Acreage Various Solar or Interstate Transmission and Road Transmission (80% of Total) Technologies Highway Line ROW Corridore 9,729 acres and 865 MWb Adjacent 4 mid and 121 acres and NAf 7,783 acresa 1,557 MWc (U.S. 285) 69 kV 0 acres a To convert acres to km2, multiply by 0.004047. b Maximum power output if the SEZ were fully developed using power tower, dish engine, or PV technologies, assuming 9 acres/MW (0.04 km2/MW) of land required. c Maximum power output the SEZ were fully developed using solar trough technologies, assuming 5 acres/MW (0.02 km2/MW) of land required. d To convert mi to km, multiply by 1.609. e BLM-designated corridors are developed for federal land use planning purposes only and are not applicable to state-owned or privately owned land. f NA = no BLM-designated corridor is near the proposed Antonito Southeast SEZ. 1 2 3 line closest to the Antonito Southeast SEZ would involve the construction of about 4 mi (6 km) 4 of new transmission line outside of the SEZ. The right-of-way (ROW) for this transmission line 5 would occupy approximately 121 acres (0.5 km2) of land, assuming a 250-ft (76-m) wide ROW, 6 a typical width for such a ROW. 7 8 Existing road access to the proposed Antonito Southeast SEZ should be adequate to 9 support construction and operation of solar facilities, because U.S. 285 runs along the western 10 boundary of the SEZ. Thus, no additional road construction outside of the SEZ was assumed to 11 be required to support solar development of the SEZ, as summarized in Table 10.1.1.2-1. 12 13 14 10.1.1.3 Summary of Major Impacts and Proposed SEZ-Specific Design Features 15 16 In this section, the impacts and proposed SEZ-specific design features assessed in 17 Sections 10.1.2 through 10.1.21 for the proposed Antonito Southeast SEZ are summarized in 18 tabular form. Table 10.1.1.3-1 is a comprehensive list of impacts discussed in these sections; the 19 reader may reference the applicable sections for detailed support of the impact assessment. 20 Section 10.1.22 discusses potential cumulative impacts from solar energy development in the 21 proposed SEZ.