In today's electric utility industry, new high-profile transmission line projects are often bogged down by public protests, permitting delays and cost overruns. In contrast, Nebraska Public Power District (NPPD), Columbus, Nebraska, U.S., was able to complete its 98-miles (158-km) Pauline-Moore 345-kV line from initial routing studies to energization in three years _ a period which for many major projects is often required for permitting alone. Completion was seven months ahead of schedule. NPPD accomplished this through a partnership with its engineering and construction subcontractors and the landowners along the route. This commitment was evident from the line's conceptual stage, through design and construction (which took only 13 months) and after energization.
NPPD's service territory includes 90 out of 93 Nebraska counties and extends from the eastern half of the state, where most of its load resides, to the western half, where a majority of the generation facilities are located. A transmission bottleneck in the eastern half of the system was restricting NPPD's ability to transfer power. NPPD's 345-kV and underlying 115-kV systems were potentially being overloaded causing reliability and safety concerns. Frequently, NPPD asked other utilities to curtail power transactions in order to reduce heavy loads.
A system-planning study was undertaken to evaluate a number of alternatives to relieve the transmission capacity limitation. Alternatives considered were several new line segments as well as upgrades to existing 115-kV lines.
After studying the alternatives, it was apparent to NPPD that a new 345-kV line from Pauline Substation south of Hastings, Nebraska, to Mark Moore Substation, not far from Lincoln, Nebraska, would be the most economic choice (Fig. 1).
Identify Public Concerns Once the project's technical requirements were finalized, NPPD began its commitment to meeting public concerns. In April 1993, NPPD contracted Power Engineers, Boise, Idaho, U.S., for engineering, environmental and construction management services. Power, in turn, teamed with environmental consultant Dames and Moore, Phoenix, Arizona, U.S., for the environmental siting and public involvement phase of the project.
The public was invited to meet with NPPD and its representatives to discuss the study area routing process and other concerns at "open-house" meetings. These meetings were held at several locations throughout the project study area. Rather than addressing the participants in one large (and often cumbersome) group presentation, NPPD organized several stations around the meeting hall so that experts could address specific concerns as each family entered the room.
A popular station at the open-house meetings was the large-scale photo mosaic of the entire 20-by-100-mile (32-by-161-km) study area. With this photo, landowners could identify their properties relative to the study area (Fig. 2).
During the June 1993 meetings, the public raised several concerns including: The benefit of the line did not outweigh the intrusion of placing it on private property.
The transmission line could adversely affect agricultural operations in some of the county's most productive crop land.
Electromagnetic fields (EMF) from the line were perceived as a possible link to cancer.
The line would have an unfavorable impact on the beauty of the area.
With this information, NPPD and the project team could develop routing alternatives and preliminary designs that would meet most of the public's concerns.
Line Routing to Minimize Impact The project team prepared initial study corridors identifying potential routing opportunities. At a second round of public open houses, the corridor alternatives were submitted for review and displayed on the photo mosaic.
With the corridor alternatives identified on the photo maps, public interest and comment increased substantially as landowners began to perceive potential impacts. Drawing on the additional public input received at the second set of meetings, the project team refined alternative corridors to the specific alternative routes. As this part of the route selection process moved forward, a third round of open houses was held in December 1993, resulting in the largest attendance _ approximately 550 people participated.
In conjunction with the public-information meetings, the NPPD/Power/Dames Moore project team met regularly with regulatory agencies, local governing bodies, public-interest groups and individual landowners. Numerous meetings were held throughout the project area in such venues as agency offices, movie theaters, farmers' machine shops and around kitchen tables.
By taking the time to understand the public's concerns and to develop a rapport with the affected parties, the project team was able to develop a final route that produced the least cumulative impact to the project area as a whole. The preferred route was announced at a series of public hearings in February and March of 1994 in accordance with Nebraska state law.
The project team's efforts with the public resulted in a route that literally went the extra mile to try and satisfy the landowners along the route. By placing most of the route on half-section lines or section lines, the Pauline-Moore line was located away from virtually all residential hous-ing. The closest home was more than 400 ft (122 m) from the line. Following the half-section lines prevented the line from affecting most of the numerous center-pivot irrigation systems encountered along the route. As a result, the affect on agricultural land was minimized.
Informing the Public To better inform the public on the need for the line, the project team developed an informational program emphasizing the benefits of the line among tenants, landowners and residents on and near the route.
The program included fact sheets, booklets that answered common questions and described the construction process, and a series of newsletters and news releases complete with photographs. Additionally, a toll-free telephone line was established for the public's use for specific comments or questions. This program supported the one-on-one communication that had already taken place among project representatives and farm tenants and owners.
By focusing on the public's concerns on routing and explaining the need for the line, NPPD was able to move through the permitting and right-of-way (R/W) acquisition phase in a timely fashion. R/W acquisition began after the public hearings and all easements were acquired by the fall of 1995. The dialogue with the landowners that had been initiated during the routing study phase continued during R/W acquisition. As a result, more than 80% of the easements were signed voluntarily.
Clarifying EMF Concerns Separate from the open houses on the line's route, the project team sponsored information meetings about EMF. Nationally recognized experts such as Enertech Consultants, Campbell, California, U.S., were called on to support the EMF information program. The meetings were held for public officials, the news media and the general public.
New Tower Design During the design phase, the project team took further measures to mitigate the issues raised during the routing phase. A new lattice-tower design was developed in response to the public's concern about EMF and agricultural land loss. A delta configuration was selected to reduce EMF. The triangular arrangement of the conductors results in a reduced magnetic field directly under the transmission line and at the edge of the R/W as compared to a horizontal-conductor configuration that had been NPPD's previous standard (Fig. 3) The new tower design also minimized the tower footprint and the resultant impact to the agricultural crop land. The narrow-base design resulted in a tangent tower that required only an 18 to 24 sq-ft (1.7 to 2.2 m2) area in the 200-ft (61 m) R/W, depending on the tower height. For the entire 98-mile (158 km) route, the total land requirement for structure place- ment was approximately 7 acres (28.3 km2).
Meets Improved Reliability Needs One of the primary needs for the new line was to increase NPPD's transmission reliability. The NPPD system is subject to severe winter icing conditions; catastrophic line cascades have been all-too-familiar occurrences. Conductor galloping has also been a common occurrence over the years. In the summer, tornadoes regularly wreak havoc to the transmission system.
Because of these extreme weather conditions, the design team emphasized defining project design criteria that would allow the line to survive the year round effects of nature with minimal economic impact. With this purpose in mind, strict failure-containment criteria were developed. Structure design loads were specified to allow for extreme heavy icing (1-1/2 inches or 38 mm), differential ice loading and high winds, including special tornado loads for the tower.
It was determined, however, that the cost of a tangent tower able to withstand a line cascade would be unrealistically high. Therefore, the project design team recommended that a special failure-containment structure be used at periodic intervals (5 miles or 8 km) along the route.
With this design philosophy in place, analysis showed that the 15-deg light-angle tower, which was already being developed as part of the structure family, could be used as the failure-containment tower. As a result, no additional tower designs were developed. Furthermore, as the transmission centerline was finalized to accommodate landowner requirements and terrain features, the placement of the light-angle towers coincided closely with the defined containment intervals, thus creating little additional cost to the project.
To address the impacts of galloping, T-2 conductor was specified for the line (Fig. 4). NPPD's previous standard for 345-kV construction was a two-conductor 954-kcmil (483 mm2) horizontal bundle. For this project a two-conductor 954-kcmil (483 mm2) T-2 (two 477-kcmil or 242 mm2) subconductor twisted together, vertical bundle configuration was chosen.
Ambitious Construction Schedule NPPD's objective was to have the line in place before the peak demands of the 1996 summer season. The project schedule called for line construction to begin in April 1995. This meant that the construction window would be approximately one year _ an ambitious effort for such a long line, especially when considering that final R/W acquisition and line engineering would still be underway at that point.
Tri-O Construction, Salt Lake City, Utah, U.S., provided the advance clearing services for the project and built the foundations for the structures. Irby Construction Co., Jackson, Mississippi, U.S., was selected to assemble the lattice towers, string the line and clean the sites.
Landowners' Teamwork Continues NPPD's efforts at maintaining positive relationships with the affected landowners was evident at the construction stage. To minimize agricultural land damage, NPPD used helicopter to erect the structures. Irby contracted with Erickson Air Crane Co., Central Point, Oregon, U.S., for helicopter services. NPPD leased assembly yards, each 5 acres (20.2 km2) from landowners at 5-mile (8 km) intervals along the 98-mile (158 km) line.
The helicopter lifted the towers from the fly yard where assembly had taken place and carried them to their foundations. By having multiple yards along the line route, the tower-carrying helicopter trips could be limited to approximately 2.5 miles (4 km), reducing the time the helicopter had to fly.
Helicopter Minimizes Impacts Using a helicopter provided several advantages for minimizing land impacts and optimizing the schedule (Fig. 5): Less activity was required in farm fields; less soil compaction occurred.
The mid-winter construction activity was supervised and sustained more effectively with larger work crews at fewer sites.
Assembly and erection were completed much more quickly.
Unless a protracted period of bad weather occurred, the cost of helicopter setting approximated the land-based method.
The helicopter made two visits to Nebraska; the first for eight days and the second for six days. During this time, Erickson set 383 lattice steel towers on the route. Nearly half the towers were put in place during each setting operation.
The weather was far from perfect for the workers on the helicopter's first visit in January 1996. Temperatures ranged from -200F to + 200F (-290C to -0.70C) and winds reached 30 mph (48.3 km/h). However, the setting process moved at a pace of approximately 30 towers a day. The helicopter returned for the second setting in February, when weather conditions were only marginally better.
The winter construction schedule actually helped minimize impact to the crop land. Although little of the actual construction occurred on farm fields, the portion that did occur took place on frozen ground. As a result, clean-up was relatively minor after construction.
To further minimize the impact on agriculture and to speed the construction process, Irby used helicopters to hang the stringing blocks and to string the pulling ropes (Fig. 6). Use of the helicopter allowed Irby to maintain a high rate of productivity during the stringing process.
Landowner Involvement Continues The line was energized April 11, 1996. Continuing with its commitment to addressing the public's concerns, NPPD involved landowners after line energization. In June 1996, NPPD sponsored field programs at three sites beneath the energized Pauline-Moore line to demonstrate to farm operators the line's minimal impact on radio and TV reception, irrigation piping and fencing. These programs were followed by "thank-you" barbecues, which were attended by more than 350 people. Landowners and tenants were provided mementos of the project.
Commitment to Public's Concerns Because of NPPD's level of public involvement throughout the project, the Pauline-Moore 345-kV line is considered to be a success. By making the public part of its project team, NPPD and its consultants enjoyed an effective level of cooperation and understanding that is unusual in today's utility environment. TDW Bob Oswald is the transmission engineering manager for Nebraska Public Power District. Columbus, Nebraska, which he joined more than 20 years ago. He was project manager for the new 345-kV line design and construction. He is a senior member of IEEE and a member of the T&D Committee. Oswald is a registered professional engineer.
Bill Eisinger is a senior project manager for Power Engineers, Boise, Idaho. He has the BSEE, MSEE and MBA degrees. During the last 22 years of his career, he has been involved in the planning, design and construction of transmission lines and substations ranging from 69 to 500 kV. Eisinger is a registered professional engineer in six U.S. states and two Canadian provinces.