National Volcanic Monument Visitor Center, Washington

U.S. FOREST SERVICE,
GIFFORD PINCHOT NATIONAL FOREST
Philomath, Oregon

The U.S. Forest Service contracted with TriAxis to provide study, design, and construction services for power and communication systems to serve a visitor center complex just north of Mount St. Helens in southwest Washington. Preliminary design services investigated the cost and reliability of overhead versus underground electric power systems with various configurations and operating voltages. A schematic design document was developed for the selected 25-kV underground power system and the fiber-optic communication system.

The power delivery point includes metering, voltage regulation, system-protection equipment, and step-up transformers (7.2/12.47 to 14.4/24.9 kV). The 30-mile-long transmission line includes three cables and four 300-kVar fixed shunt reactors at specific locations to stabilize voltage swings and reduce system losses. The cable is designed with 345 mils of XLPE/TR insulation (35-kV rating). Splices, elbows, and tap transformers are also rated for 35-kV operation.

The communication system primarily consists of a 4-fiber, single-mode cable without any mid-route amplifiers. TriAxis was responsible for design coordination of the telephone company interconnection, a control building, and the visitor center’s local exchange equipment.

The three power cables and the single fiber-optic cable occupy a 4-conduit duct bank, including 77 underground vaults, located along the shoulder of the new SR 504 highway leading to the visitor center complex. The project includes the crossing of 12 bridges in mountainous terrain. TriAxis also provided preliminary design and geotechnical engineering for the new highway.

A three-year highway rebuild and straightening project for a 4.8-mile hilly terrain section of Highway 20 through Eddyville, Oregon, including the addition of 10 new bridges across Little Elk Creek.

Major coordination efforts between the Utility, Oregon Department of Transportation (ODOT) in Salem, Corvallis, and their field offices, the highway construction contractor, and the project surveyor.

Relocation and rebuild of approximately 3.2 miles total of 14.4/24.9-kV distribution line broken into 10 separate segments.

Relocated sections were staked with the aid of GPS surveying, and line construction was accomplished prior to road construction.

Highway crossings included areas adjacent to new bridges under construction and required special consideration for equipment clearances and guardrail installation. A single ODOT Highway Permit was prepared with 14 crossing sketches.

Future utility access to relocated facilities was a major design criterion for the new line sections.