BPA Midway-Ashe 230kV Transmission Line

CLIENT Bonneville Power Administration (BPA) & Department of Energy Richland (DOE-RL)

Location Benton County, WA

BPA and the DOE-RL intend to replace an aging 230 kV transmission line with a new double circuit line between the BPA Midway and Ashe substations.

The line is part of the Hanford Site 230 kV transmission system, which serves as a source of electrical power to area facilities. The project will replace conductors, hardware, and support structures, and will shorten the circuit length and increase long-term reliability of the Hanford Site system.

Performing field explorations for this site is particularly complex because of the nature of the site: Hanford contains potentially radioactive materials. The Shannon & Wilson team had to take into account stringent safety measures for those involved in the explorations, safe processes for the elimination of investigation-derived waste, and environmental concerns for native bird species, among other considerations. We carefully planned and performed a geotechnical investigation of the project area, which included a surface reconnaissance, 20 geotechnical borings, development of soil parameters for use in MFAD computer software, and development of construction considerations and recommendations.

In addition to the sensitive site conditions, our explorations found Dune Sand and Hanford Formation soils. Due to the properties of these soils (especially the susceptibility of Dune Sand collapsing when wetted or loaded), we concluded that they will not support open bore hole excavations for the drilled shaft and direct embedded poles. Instead, Shannon & Wilson recommended that transmission line structures should be constructed in cased excavations, and that contractors should avoid saturating the surface soils near the shaft excavations, completed towers, and heavy construction equipment.


Alia Hubbard
Environmental Staff

Jerry Jacksha
Senior Associate

Elliott Mecham
Senior Associate

Park Piao
Vice President

James Walters

Clinton Wilson
Senior Associate

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