Constructing the Transmission Line

Construction of the proposed transmission line would begin after Idaho Power receives permits from BLM and USFS, and an Energy Facility Site Certificate from ODOE-EFSC. If the project is approved, Idaho Power could begin construction by 2013.

Constructing a transmission line is a big undertaking, which includes building access roads and towers, stringing lines and restoring disturbed lands. Idaho Power will oversee all transmission line and substation design and construction, and contract with construction companies to build the line.

Idaho Power will conform to all state and federal siting requirements when siting the line. Additionally, all applicable safety codes and standards will be followed to ensure our system operates safely and reliably.

The sequence for general transmission line construction is described below.

Building access roads and site preparation Access roads are built throughout the corridor to construct the transmission line and conduct maintenance during the life of the line. In order to accommodate large equipment and materials during construction, access roads are approximately 14 feet wide. Construction staging areas and substation sites are also constructed. Erosion, both during and after construction, is minimized with the installation of water bars, culverts and sediment basins. Installing tower foundations Foundations are installed at each tower site. Typical foundations are made of steel reinforced concrete piers and are generally four feet in diameter and 15 feet deep, though these numbers may vary depending on the soil and/or rock type at each site. Each foundation extends about two feet above the ground. Reinforced steel anchor bolt cages are installed after excavation and before concrete placement to strengthen the foundation’s structural integrity. Assembling the structure Components for each structure are delivered by flatbed trucks and assembled onsite by a truck-mounted crane. The structures are then lifted onto the foundation using a large crane specifically designed for tower construction. The crane moves along the right of way to set each structure in place. In some locations, it is necessary to set structures using a helicopter (see photo). Every three miles along the right of way, temporary five-acre work sites are set up for the equipment used to pull and tighten the wires or conductor. Stringing the line The initial stringing begins with a helicopter pulling a lighter weight sock line through sheaths attached to each tower. A specialized wire-stringing vehicle is attached to the line to pull it through, followed by tightening or tensioning the line to achieve the correct sagging of the line between support structures. Restoring and re-vegetating disturbed lands Disturbed areas around the structures are restored and re-vegetated, as required by the land management agency and per the property owner agreement. All practical means are used to return land to its original contour and natural drainage patterns along the right of way.

This Web site is the joint Boardman to Hemingway Transmission Line Project site. Information contained on this site is approved for posting by Idaho Power. Visit the Idaho Power Web site.