Charting A Course

Sept. 28, 2010

As rural electric cooperatives continue to grow, transmission planners from Tri-State Generation and Transmission Association (Tri-State) envision a new transmission network to provide more reliable electrical power to their member systems in eastern Colorado. As the concept developed, Western Area Power Administration (Western) saw benefits in the project and agreed in December 2005 to participate with Tri-State.

As rural electric cooperatives continue to grow, transmission planners from Tri-State Generation and Transmission Association (Tri-State) envision a new transmission network to provide more reliable electrical power to their member systems in eastern Colorado. As the concept developed, Western Area Power Administration (Western) saw benefits in the project and agreed in December 2005 to participate with Tri-State.

Since then, the project — known today as the Eastern Plains Transmission Project (EPTP) — has evolved from lines on maps to a series of markers, one every three miles, across parts of eastern Colorado and western Kansas. The markers are survey reference points located by Ayres Associates' surveyors that will help determine the eventual 1,000-mile transmission line route.

It's been a challenging journey.

Tri-State and Western must determine the optimal location for the lines across a vast landscape that includes open range with little development and even fewer highways as well as rapidly growing communities. At more than $1 million per mile, construction of each new line represents a substantial investment in the electrical power security of a large portion of the eastern plains.

The new high-voltage transmission lines and related facilities would improve reliability of the existing transmission grid and support increased demand for power in the service area in the next decade. The project would also put Tri-State, as the eventual owner of the lines, in a position to work more with producers of renewable energy resources such as wind power.

Western is responsible for preparing an environmental impact statement for the proposed project and for the design and construction of the new system. It's a complex planning process that requires input from private and public entities, extensive environmental analysis, public contact and coordination, and engineering evaluation.

"This schedule-driven endeavor requires our team and our consultants to move with speed and flexibility, even as the new options are identified almost daily," said Craig Knoell, Western's EPTP manager.

The lead engineering consultant on the project, Ayres Associates, has been performing ground and aerial surveys throughout the 1,000-mile corridor, gathering the information Western needs to help determine the proposed paths of the lines for the environmental impact statement. Ayres Associates is an engineering/architectural consulting firm with offices in Colorado and seven other states.

On the ground, Ayres Associates surveyors searched for "monuments" that would allow them to begin determining where the planned corridors are. The monuments are markers that were created or placed in the late 1800s, when portions of Colorado and Kansas were first surveyed. When surveyors determined a known location, they marked the spot. Some monuments were metal markers. Others were etched stones or even charred cedar stakes.

In more developed areas, modern-day surveyors can locate monuments at regular intervals. They rely on those monuments as an accurate starting point for whatever survey work they need to complete.

That wasn't the case in the Eastern Plains Transmission Project. Of all the points that needed to be established, surveyors were able to find only about 5 percent or 10 percent based on existing monuments, according to Fred Halfen, Ayres Associates' vice president for energy corridors. That made the task more challenging.

Using extremely accurate GPS equipment, survey crews established points one at a time. As a side benefit to Western's project, the surveyors established the Eastern Plains Reference Network. It's a system of high-accuracy survey points that surveyors from now on will be able to rely on when they do work in the region.

Logistics were also a challenge. Most of the work took place in rural areas, far from lodging, restaurants, good roads, or places to buy needed supplies, Halfen said. And before surveyors could enter privately owned property, Western had to secure permission from landowners — about 1,200 people.

That effort began with the process of determining who those landowners are. Much of the property information did not exist digitally, and property data management was a critical component of the real estate efforts.

Ayres Associates' real estate specialists went on location in county courthouses throughout eastern Colorado and western Kansas, sifting through documents and locating records for land parcels potentially affected by the project. Information obtained was digitally scanned and integrated into a database designed to provide a comprehensive inventory of all property research. The resulting project management system allowed field surveyors and others to have digital access to all property information — at any time and from any location with Internet access.

For about 18 months, Ayres Associates crews were either gathering information in the field or processing the data for all routes Western was considering for the transmission line routing.

At any one time, Ayres Associates had a crew in the field while another was analyzing the data and putting it in the form that Western and Tri-State needed. Survey crews worked seven days a week, three weeks on and one week off. Staff members worked an average of 70 to 75 hours per week.

That's the pace that was required to complete this portion of the project on schedule, and the pace at which crews are prepared to continue to work, if needed, Halfen said.

"What has impressed us with Ayres Associates is that they have kept on track with the schedule despite interruptions or limited data," said Frank Bradley, lead civil engineer for Western. "Delays happened almost daily, but they have handled it very professionally."

The corridor the surveyors marked on the ground is called the "control." Once a portion of that work was completed, the air crews were able to begin gathering information. Air reconnaissance requires accurate points of reference on the ground so technicians know which territory is being analyzed.

From the air, technicians used two forms of technology to gather information along the route. The first is aerial photography. Each inch on the photos represents 250 feet of land surface. The aerial photographs are digitally modified to account for the Earth's curvature. The resulting images so closely represent the actual land that they can be used to measure distances, like a map. They also show structures, roads and other features that could affect transmission line corridor planning.

The second technology is LiDAR, or light detection and ranging. A laser "reads" the contours of the land, recording every variation in elevation. In the Eastern Plains Transmission Project, LiDAR provided 2-foot contour images of the entire corridor.

The two types of "pictures" are combined to develop detailed images that show engineers every hill and valley, every roadway, every structure, every river, and all other land features, helping engineers to tentatively locate transmission tower sites and calculate the path of the proposed line. The approach worked well for this project, Bradley said.

"Aerial data gathering worked ideally for our purposes," he said.

To date, the EPTP survey effort is approximately 40 percent complete. Western is studying and developing alternative routes based on environmental considerations, landowner concerns, opportunities to take advantage of diverse energy sources, and cost.

"Study after study has identified the need for more transmission, nationally and, specifically, within this region," Knoell said. "The Eastern Plains Transmission Project is part of Western's continuing effort to provide economical, reliable, diverse, and flexible power delivery to our customers."

Story and photos courtesy of Ayres Associates.