SIPHON POWER PLANT

In October 1989, after ten years of work, the Central Oregon Irrigation District completed and commissioned its Siphon Power Project. Built in conjunction with its Central Oregon Canal, the $14 million dollar project is designed to produce an estimated average generation of 25 million kilowatt hours per year, enough to serve about 2,500 homes.

Water for the Central Oregon Canal is diverted from the Deschutes River about three miles upstream from Bend's Colorado Street Bridge. Near the diversion site, the river is in a steep, narrow canyon. About a mile and a quarter downstream from this diversion structure, COID has built an underground powerhouse containing two generators and turbines. At a point above the powerhouse, the canal is 135 feet above the river. Here the water is diverted into a buried pipe that brings it into the powerhouse.

One of two turbines producing power at the Siphon Power Project

At the powerhouse, the water enters one of the two turbines to produce electricity before being returned to the Deschutes River. The energy produced travels through an underground powerline to a transformer located near the canal and then into the existing power grid. Pacific Power & Light has agreed to buy all the power COID will generate during the next 35 years.

The Oregon Department of Energy provided the financing for the project in the form of revenue bonds, which will be repaid by the project. Profits will then be used to (1) control or reduce assessments levied upon its water users for District operation and maintenance, (2) to launch the first large water conservation program in Central Oregon and (3) to make capital improvements for the District.

Every effort has been made to minimize the impact of this development on the surrounding area and to limit the effects of the powerhouse upon the environment. COID improved an existing diversion structure on the Deschutes River, no new structure was constructed in the river; the powerhouse is primarily an underground facility; the site has been landscaped with native streamside plants and an ongoing landscaping program has been planned.

Environmental consequences are limited to the one stretch on the river between the diversion structure and the point where water re-enters the Deschutes River, a distance of approximately 6,300 feet. As required by State Law, COID has worked out a mitigation program to protect the fish resources in the project reach.

Noise impact from the project comes from three sources: the turbine generator, the tailrace (where water re-enters the Deschutes River after going through the generating facility) and the electric transformers. The turbine and generator sound is contained within the underground powerhouse structure. The tailrace sounds like a medium-sized waterfall. Standing next to the transformer, the sound is about as loud as the hum of a busy office. Standing 100 feet away from the transformer, the sound is nearly unnoticeable.

The quality of the river remains unchanged and there is no recreation impact as all water is returned to the river. Water is diverted for power production only when available. Irrigation water delivery remains the District's highest priority.