Logan Simpson Surveys 11,000 Acres within Three Solar Energy Zones for the BLM

Tina Hart, M.A., RPALogan Simpson helped the Arizona Bureau of Land Management (BLM) facilitate environmentally responsible utility-scale solar energy development by surveying more than 11,000 acres in solar energy zones (SEZs) in compliance with Section 110 of the National Historic Preservation Act.

SEZs are priority development areas the BLM has identified as well-suited for utility-scale solar energy production. As part of the transmission infrastructure development, Logan Simpson’s cultural resources consultants surveyed parcels in SEZs located near the communities of Brenda, in La Paz County (Brenda SEZ); Gillespie, in Maricopa County (Gillespie SEZ); and Hyder, in Yuma County (Agua Caliente SEZ). The survey resulted in the documentation of 158 sites. This brief summary highlights a portion of the most interesting finds.

In the 3,348-acre Brenda SEZ project area, Logan Simpson encountered 77 sites. Thermal rock features, occurring singly or in groups and often containing only a few artifacts, are the dominant site type, but non-thermal rock features, artifact scatters, trails, and intaglios were also recorded.

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Possible shrine documented by Logan Simpson in the Brenda SEZ.

Archaeologists observed some unique feature types during the survey, including possible shrines and miniature rock rings containing artifacts. At one site, cultural resources consultants from Logan Simpson recorded two possible shrines, one intaglio, three rock concentrations, two trails, and 100 lithic artifacts. The two possible shrine features include a large (30–40-cm tall) black basalt boulder surrounded by 200–300 smaller fist-sized cobbles that radiate outward in a roughly circular pattern. One of these is visible from a trail. At both features it appears as if people tossed rocks at the central boulders. Historically, Yuman and O’odham groups tossed stones onto rock shrines at important nodes along the trail for luck, a custom that the O’odham continue to practice. This ethnographic analogy provides supporting evidence for the interpretation of these features as shrines. The site also hosts a cross-shaped intaglio that measures 16 m by 13 m.

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Example of a miniature rock ring containing artifacts.

Logan Simpson repeatedly observed small rock rings with and without artifacts placed in the center of the ring. It was initially thought that these features may represent modern activities associated with recreational use of the area; however, these feature types were encountered at sites located away from roads and contain no indication of modern visitation. These particular features consist of rocks in a circular arrangement, ranging from 20 to 60 cm in diameter, situated on the ground surface. The vast majority of these rings contain from one to 20 flaked-stone artifacts, frequently from a variety of material types. The contents generally do not appear to represent single flaking events, but rather a collection of various flakes, and sometimes tools. Logan Simpson recorded 38 such features at five separate sites. The rock rings are sometimes associated with thermal rock features.

The 5,104-acre Agua Caliente SEZ survey area contains 72 sites ranging from prehistoric thermal rock features, trails, non-thermal rock features, cleared areas, intaglios, ceramic scatters, camps, and seasonal habitation sites to historic roads, military-related sites, trash scatters and dumps, and a landing strip. A portion of the Palomas Plain within the project area contain a nearly continuous expanse of prehistoric Arizona cultural resources stretching for more than three miles.

Logan Simpson recorded hundreds of features at dozens of sites. Thermal rock features are the most common, and are dispersed along an eroded landform of exposed sediment and little vegetation. This landform also contains tens of thousands of ceramic, flaked, and ground artifacts, and one site exhibits staining and what appears to be burned adobe, suggesting that habitation structures may be present. The landform is bordered on the east and west by desert-pavement-capped terraces that contain circular cleared areas, intaglios, and rock rings. The quantity, variety, and good condition of these Arizona cultural resources make this portion of the Agua Caliente SEZ an ideal candidate for listing as a National Register of Historic Places archaeological district. Moreover, the BLM plans to use the data gathered by Logan Simpson to assist them with this important task.

Tina Hart has 16 years of experience as an archaeologist. She has worked extensively throughout southern Arizona and has broad survey, testing, and data recovery experience as a crew member and field director.

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