Arrowhead to Weston 345 kV Transmission Line

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Client Name: American Transmission Company
Location:  Wisconsin

The 220-mile award-winning Arrowhead-Weston 345 kV transmission line project was designed to relieve transmission constraints and improve reliability in northwestern Wisconsin. At the time of its development, the line was one of the largest transmission lines built in the US in decades. The project began as a joint effort with Minnesota Power and Wisconsin Public Service Corporation. Shortly after POWER Engineers began its involvement in the project, American Transmission Company, a Wisconsin state-mandated transmission company, took control of the project. 

This noteworthy project was a winner of the 2009 Edison Award, which recognizes U.S. electric companies for outstanding leadership, innovation and advancement in the electric industry. The project also received the 2008 Wisconsin Engineering Achievement Award from the Wisconsin Chapter of ASCE.

Throughout a nearly decade-long involvement with the project, POWER provided a wide range of services, including preliminary and final design; right of way acquisition; and construction monitoring support. POWER also supported the project owners to facilitate the management of this massive project in many valuable ways.

Cost management needed to gain project approval

Early in the project, POWER began developing and tracking the project costs. It was clear that the original budget (prepared by others) was no longer accurate to meet the project requirements. A new budget would mean a new approval process before the Wisconsin Public Service Commission. POWER assisted ATC in developing overall project cost estimates and scheduling.

As part of the approval process, POWER prepared a written deposition to the Wisconsin PSC, describing how we prepared these cost estimates. POWER’s engineering manager then testified at a public hearing by the Wisconsin PSC to defend the cost estimates for ATC. The PSC granted approval for the $430+ million project.

Tightly managed scheduling effort brings project energization four months early

Requiring more than 1,500 structures across its 220 miles, the Arrowhead-Weston project needed to be broken down into smaller segments to facilitate management. While Wisconsin Public Service acted as the overall scheduler, POWER interfaced with the scheduler to create a meaningful and accurate schedule that would be cost effective and efficient. POWER developed flow charts to schedule the project into 12 manageable segments. Part of that scheduling included sequencing the procurement for each segment. Material was scheduled to be released as each segment progressed to construction. This scheduling approach proved to be effective – the line was energized four months ahead of schedule.

Throughout the project, POWER participated in bi-weekly meetings with the scheduling and management team to review the 30-day look-ahead schedule and determine if all tasks were on track. POWER provided input for the scheduler as needed. At the same time, POWER contributed to the project action-item list, which tracked the status of action items needed to keep the project on schedule.

Contract management

Related to scheduling support, POWER also facilitated contract management efforts throughout the project. POWER played a major role in selecting the construction contractor. POWER developed RFQ requirements and bid evaluation procedures. Once the bids were in, POWER worked with the project owners to select a short-list and hosted interviews with the contractors.

For major material items (structures, insulators, hardware, shield wire, OPGW and conductor), POWER solicited quotations and prepared the specifications. In this role, POWER evaluated the bids, made award recommendations and assisted in expediting delivery. As part of its role as design engineer, POWER also managed the work of several geotechnical and survey subcontractors.

POWER’s Wisconsin project office facilitates right of way management

A smooth right of way process was critical for a line of this length. Twelve miles were in northern Minnesota with the rest of the route extending into central Wisconsin. Early in the project, POWER established an office in Hayward, Wisconsin, to manage the right of way acquisition for the line and interface with Minnesota Power and Wisconsin Public Service (and later ATC). From this office, POWER was responsible for landowner contacts, obtaining right of entry, acquisition of limited title certificates, fair market value appraisals, survey descriptions and plats, permit and easement negotiations, and fee purchases.

Selected structure family met strength and flexibility needs

The 10-year project presented numerous design challenges. One of the earliest was to identify a basic structure design that would provide strength and durability, accommodate narrow rights of way and offer design flexibility for special situations. Single-pole, tubular-steel shafts on drilled pier foundations were selected for the majority of the 1,564 structures. As part of the quality control process, POWER reviewed vendor drawing development for conformance to these structure specifications.

Design challenges include Great Lake weather, river crossing and wetlands

Due to the critical importance of the new line, it was designed for a 400-year return period event for high reliability. This required two distinct loading criteria – one to accommodate the local weather conditions around Lake Superior and one to accommodate the more typical weather conditions of central Wisconsin. For the crossing of the Namekagon River, aesthetics were of extreme importance. To reduce visibility of the line, limitations were imposed on the number of wires allowed to cross over the river. This required a bore under the river to install an underground fiber system to preserve the fiber signal of the OPGW. Another challenge was the great number of wetlands encountered along the line’s route and the requirement to permit every structure before it was placed near a wetland.

Design services included preliminary engineering to develop criteria, specifications, and structure configurations, and to select major points of intersection in the line route. Electrical system studies services included insulation coordination, capacitor bank switching, shield wire analysis, and inductive interference evaluation. Final design included detailed structure and foundation design and optimal structure spotting along the 220-mile project.