The De Tilla Gulch Solar Energy Zone (SEZ) is located in Colorado in a high-elevation basin within the Rocky Mountains. The SEZ is located on BLM-administered land within the Saguache Field Office.
As of April 2015, BLM Colorado had received no expressions of interest for new solar projects in the SEZ. As of November 2018, there were no pending solar project applications within the SEZ, or within the state of Colorado.
The De Tilla Gulch SEZ is the smallest of the SEZs. In the Draft Solar PEIS the proposed total area of the SEZ was 1,522 acres (6.2 km2). In the Supplement to the Draft, 458 acres (1.9 km2) along the northwest edge of the SEZ were eliminated to reduce impacts on various resources. The remaining SEZ developable area is 1,064 acres (4.3 km2). No additional changes to the SEZ developable area were made in the Final Solar PEIS.
The De Tilla Gulch SEZ is located in Saguache County in south-central Colorado, in the northwestern portion of the San Luis Valley, part of the San Luis Basin, a large, high-elevation basin within the Rocky Mountains. The San Juan Mountains to the west and the Sangre de Cristo Range to the east form the rim of the basin. In 2008, the county population was 6,903, while the surrounding four-county region had a total population of 51,974. The largest nearby town of Alamosa is located about 50 mi (80 km) to the south.
The De Tilla Gulch SEZ is in a gently sloping treeless plain, and scrubland vegetation reflects the arid climate. Vegetation is primarily low shrubs and grasses, with many areas of bare, generally tan soil or gravel. The SEZ is intersected with dry streambeds. Annual rainfall averages about 8 in. (20 cm).
Unpaved roads cross the SEZ, and some cleared areas are located in the northeastern portion of the SEZ where sand and gravel have been removed. The SEZ contains a windmill, wire fences, and a transmission line that runs north to south along the road on the eastern side of the SEZ. Part of the SEZ is authorized by the BLM for grazing.
Little commercial or industrial activity exists in the surrounding area. A small landfill is located northeast of the SEZ, as are transmission lines and towers. Agricultural areas lie to the east and to the south.
U.S. 285 borders the northwest boundary of the SEZ. An existing 115‑kV transmission line is accessible to the SEZ.