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Electric Transmission Visibility and Visual Contrast Threshold Distances

Argonne researchers conducted a field study of electric transmission facilities in western landscapes to assess maximum visibility and visual contrast thresholds.

As energy demand rises, both renewable and fossil energy plants are being sited in the western United States, leading to a concurrent need to add significantly to the electric transmission infrastructure that carries electric power to load centers. Land management agencies, in their attempts to minimize visual impacts to high-value scenic resources, face major challenges in siting these transmission facilities. The length and linear nature of transmission projects, combined with the large size and strong regular geometry of transmission towers, may cause strong visual contrasts that affect multiple sensitive visual resource areas along the right of way.

The visibility and potential visual contrasts associated with electric transmission facilities depend on complex interactions among a variety of factors, but so far, little systematic study of visibility in real landscape settings has been conducted in the open, unforested landscapes common to much of the western United States. There is uncertainty about the maximum distances at which transmission facilities of different types and sizes are visible, and the distances at which they cause major, moderate, and minor visual contrasts.

High-Voltage Monopole and Lattice Transmission Towers, California

Study Summary

In a study sponsored by the U.S. Department of the Interior Bureau of Land Management's Wyoming State Office, Argonne National Laboratory's Environmental Science Division conducted observations of electric transmission facilities in differing landscape settings in western states, under various lighting and weather conditions in different seasons. Study objectives included identifying the maximum distances at which the transmission facilities are visible and assessing the effects of distance on visual contrasts associated with the facilities.

Study Results

Project fieldwork was conducted in 2013. Observed facilities included 500 kV lattice tower and monopole facilities, and 230-kV H-frame and monopole facilities. A total of 232 observations from 123 study observation points were made in a variety of lighting and weather conditions. Skylined facilities with 500-kV lattice towers were visible to the unaided eye at a maximum distance of approximately 17 mi (27 km), and 500-kV lattice tower facilities were visible at or beyond 10 mi (16 km) in 16 observations. The 500-kV lattice tower facilities were judged to be noticeable to casual observers at distances of up to 10 mi (16 km). They also were judged to strongly attract visual attention at distances of up to 3 mi (5 km). The 500-kV monopole facilities were visible at distances up to 11 mi (18 km). The facilities were judged to be noticeable to casual observers at 5 mi (8 km), and a major attractant of visual attention at 2.5 mi (4.0 km). Skylined 230-kV H-frame tower facilities were observed at distances up to 8 mi (13 km), and were judged to be noticeable to casual observers at distances of up to 3.5 mi (5.6 km). They were judged to strongly attract visual attention at distances of up to 1.5 mi (2.4 km).

Project Status

The Electric Transmission Visibility and Visual Contrast Threshold Distances project was completed in 2014, and the study results (PDF, 3.1MB) are available online. The results of this study have important implications for determining appropriate distances from transmission facilities for visual impact assessments, and for the siting of transmission facilities to reduce visual impacts on visually sensitive lands.

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