De Tilla Gulch SEZ Analysis
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1 10.2 DE TILLA GULCH 2 3 4 10.2.1 Background and Summary of Impacts 5 6 7 10.2.1.1 General Information 8 9 The proposed De Tilla Gulch SEZ has a total area of 1,522 acres (6.2 km2) and is 10 located in Saguache County in south-central Colorado (Figure 10.2.1.1-1). In 2008, the county 11 population was 6,903, while the four-county region surrounding the SEZ—Alamosa, Chafee, 12 Saguache, and Rio Grande Counties—had a total population of 51,974. The largest nearby town, 13 which is located about 50 mi (80 km) to the south, is Alamosa with a 2008 population of 8,745. 14 The village of Saguache is located about 8 mi (12 km) west of the SEZ on U.S. 285, which runs 15 along the northwest side of the SEZ. The SLRG Railroad serves the area. The nearest public 16 airport is the Saguache Municipal Airport near the town of Saguache. Santa Fe, New Mexico, 17 lies about 160 mi (257 km) to the south, and Denver, Colorado, is located about 130 mi (209 km) 18 to the northeast. 19 20 An existing 115-kV transmission line is accessible to the SEZ. It is assumed that an 21 existing transmission line could potentially provide access from the SEZ to the transmission grid 22 (see Section 10.2.1.2). There were no pending solar project applications within the SEZ as of 23 February 2010. 24 25 The proposed De Tilla Gulch SEZ lies in the northwestern portion of the San Luis Valley, 26 part of the San Luis Basin, a large, high-elevation, basin within the Rocky Mountains. The 27 San Juan Mountains to the west and the Sangre de Cristo Range to the east form the rim of the 28 basin. The land within the proposed SEZ is flat and intersected with dry streambeds that run to 29 the southeast. No developments exist on the land, which is currently used for grazing, nor is 30 there any standing surface water. Scrubland vegetation reflects the arid climate, which produces 31 an annual average rainfall of about 8 in. (20 cm). Large groundwater reserves underlie the area in 32 several aquifers. Little commercial or industrial activity exists in the surrounding area, while 33 agricultural areas lie to the east and to the south. 34 35 The proposed De Tilla Gulch SEZ and other relevant information are shown in 36 Figure 10.2.1.1-1. The criteria used to identify the SEZ as an appropriate location for solar 37 energy development included proximity to existing transmission lines or designated corridors, 38 proximity to existing roads, a slope of generally less than 2%, and an area of more than 39 2,500 acres (10 km2). In addition, the area was identified as being relatively free of other types 40 of conflicts, such as USFWS-designated critical habitat for threatened and endangered species, 41 ACECs, SRMAs, and NLCS lands (see Section 2.2.2.2 for the complete list of exclusions). 42 Although these classes of restricted lands were excluded from the proposed De Tilla Gulch SEZ, 43 other restrictions might be appropriate. The analyses in the following sections evaluate the 44 affected environment and potential impacts associated with utility-scale solar energy 45 development in the proposed SEZ for important environmental, cultural, and socioeconomic 46 resources. Draft Solar PEIS 10.2-1 December 2010 1 2 FIGURE 10.2.1.1-1 Proposed De Tilla Gulch SEZ Draft Solar PEIS 10.2-2 December 2010 1 10.2.1.2 Development Assumptions for the Impact Analysis 2 3 Maximum development of the De Tilla Gulch SEZ is assumed to be 80% of the total 4 SEZ area over a period of 20 years, a maximum of 1,217 acres (5 km2). These values are 5 shown in Table 10.2.1.2-1, along with other development assumptions. Full development 6 of the De Tilla Gulch SEZ would allow development of facilities with an estimated 135 MW 7 of electrical power if power tower, dish engine, or PV technologies were used, assuming 8 9 acres/MW (0.04 km2/MW) of land required, and an estimated total of 243 MW of power 9 capacity if solar trough technologies were used, assuming 5 acres/MW (0.09 km2/MW) of 10 land required. 11 12 Availability of transmission from SEZs to load centers will be an important consideration 13 for future development in SEZs. A 115-kV transmission line crosses the SEZ. It is possible that 14 this existing line could be used to provide access from the SEZ to the transmission grid, but the 15 115-kV capacity of that line may not be adequate for 135 to 243 MW of new capacity (note: a 16 500-kV line can approximately accommodate the load of one 700-MW facility). At full build-out 17 capacity, new transmission and or upgrades of existing transmission lines may be required to 18 bring electricity from the proposed De Tilla Gulch SEZ to load centers; however, at this time the 19 location and size of such new transmission facilities is unknown. Generic impacts of 20 transmission and associated infrastructure construction and of line upgrades for various resources 21 are discussed in Chapter 5. Project-specific analyses would need to identify the specific impacts 22 of new transmission construction and line upgrades for any projects proposed within the SEZ. 23 24 TABLE 10.2.1.2-1 Proposed De Tilla Gulch SEZAssumed Development Acreages, Maximum Solar MW Output, Access Roads, and Transmission Line ROWs Assumed Distance and Assumed Total Acreage and Maximum Distance to Capacity of Area of Assumed SEZ Output Nearest Nearest Transmission Development for Various State, U.S. or Existing Line ROW Distance to Nearest Acreage (80% of Solar Interstate Transmission and Road BLM-Designated Total) Technologies Highway Line ROW Corridord 1,522 acres and 135 MWb Adjacent Adjacent and 0 acres and Adjacent/Throughe 1,217 acresa 243 MWc (U.S. 285) 115 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 if the SEZ were fully developed using solar trough technologies, assuming 5 acres/MW (0.02 km2/MW) of land required. d BLM-designated corridors are developed for federal land use planning purposes only and are not applicable to state-owned or privately owned land. e A BLM locally designated corridor covers about two-thirds of the proposed De Tilla Gulch SEZ. Draft Solar PEIS 10.2-3 December 2010 1 For purposes of analysis in this PEIS, it was assumed that no additional acreage would be 2 disturbed for transmission line access, because an existing 115-kV transmission line crosses the 3 SEZ. A BLM locally designated corridor also runs through the SEZ, as shown in 4 Table 10.2.1.2-1. Access to an existing transmission line was assumed, without additional 5 information on whether this line would be available for connection of future solar facilities. If a 6 transmission line were constructed in the future to connect facilities within the SEZ to a different 7 off-site grid location from the one assumed here, site developers would need to determine the 8 impacts from construction and operation of that line. In addition, developers would need to 9 determine the impacts of line upgrades if they were needed. 10 11 Existing road access to the proposed De Tilla Gulch SEZ should be adequate to support 12 construction and operation of solar facilities, because U.S. 285 runs along the northwestern 13 boundary of the SEZ. Thus, no additional road construction outside of the SEZ is assumed to be 14 required to support solar development of the SEZ, as summarized in Table 10.2.1.2-1. 15 16 17 10.2.1.3 Summary of Major Impacts and Proposed SEZ-Specific Design Features 18 19 In this section, the impacts and proposed SEZ-specific design features assessed in 20 Sections 10.2.2 through 10.2.21 for the proposed De Tilla Gulch SEZ are summarized in 21 tabular form. Table 10.2.1.3-1 is a comprehensive list of impacts discussed in these sections; 22 the reader may reference the applicable sections for detailed support of the impact assessment. 23 Section 10.2.22 discusses potential cumulative impacts from solar energy development in the 24 proposed SEZ. 25 26 Only those design features specific to the De Tilla Gulch SEZ are included in 27 Sections 10.2.2 through 10.2.21 and in the summary table. The detailed programmatic design 28 features for each resource area to be required under BLM’s Solar Energy Program are presented 29 in Appendix A, Section A.2.2. These programmatic design features would be required for 30 development in this and other SEZs. Draft Solar PEIS 10.2-4 December 2010 D raft Solar PEIS raft SolarPEIS TABLE 10.2.1.3-1 Summary of Impacts of Solar Energy Development within the Proposed De Tilla Gulch SEZ and Proposed SEZ- Specific Design Featuresa Resource Area Environmental Impacts—Proposed De Tilla Gulch SEZ SEZ-Specific Design Features Lands and Realty Full development of the SEZ could disturb up to 1,217 acres (5 km2); None. utility-scale solar energy development would be a new and discordant land use to the area.