Facts About the Project

Rocky Reach Spillway The Rocky Reach Hydro Project is located in north central Washington state on the Columbia River, about seven miles upstream from the city of Wenatchee. By river, the dam is 215 miles below the Canadian border, and 473 miles above the mouth of the Columbia at Astoria, Ore.

More than 7 million people throughout the Northwest benefit from clean, renewable energy produced at Rocky Reach. The project is also nationally recognized for efforts to protect the environment. A first-of-its-kind juvenile fish bypass system was completed in 2003 to help young salmon and steelhead on their way to the ocean. A major powerhouse upgrade started in 1995 includes new turbines that are more fish friendly. Improvements to turbines and generators are also designed to improve efficiency and reliability.


An innovative juvenile fish bypass system helps move young salmon and steelhead
quickly and safely past the Rocky Reach Hydro Project.

The bypass includes two main parts. The first is a collector system which relies on 29 large pumps to create a strong current, appealing to the natural instincts of the young fish to attract them to a collector in the damís forebay.

The bypass pipe traverses the dam.
Once the fish are in the collector, water moves them into the second part of the system -- a steel tube up to 9 feet in diameter. The tube passes through the dam and extends 4,600 feet around the back side of the powerhouse, across the face of the spillway and about one-third mile down the east side of the Columbia River before the fish are returned to the river. The entire trip will take young fish about six to eight minutes.


Construction of the pipe continued on the east bank of the river.

Construction of the permanent system was carefully planned so that all work in the river would be done between fish migrations. Some of the large components of the collector system, including the pump house, were built at a peninsula upriver from the dam during the summer, and then floated into place once salmon migrations were finished.

Original CAD diagram provides an overview of the Rocky Reach fish bypass system including pump station (left, in forebay) and fish return pipe (lower, right). 

In addition to making the down-river trip easier for juvenile salmon and steelhead, the bypass system will also reduce the need to spill water over the dam. That water can then be used to generate electricity more than offsetting the $112 million cost of the bypass. During a 15-year life span, the project is expected to save spill worth about $400 million.

Since 1985, the PUD has developed laboratory models and tested prototype fish bypass systems for intercepting and moving juvenile fish around Rocky Reach as they travel downriver to the ocean. Screens were designed to steer young salmon and steelhead away from the turbines and into a bypass channel. None of the prototype screening systems tested achieved the results experienced at other Columbia River hydro projects. So a new approach was taken in 1995 -- a surface bypass and collection system that appeals to the young fish's natural instinct to migrate downriver near the surface, following the water flow. This differs from conventional turbine intake screens, which require fish to dive into the turbine intakes before they are intercepted by the screens. Also, after the surface collector was added in 1995, the fish guidance effectiveness improved for the screen systems left in two units to enhance interim protection. Because of the improvement in the screens' performance, they have been incorporated into the final design of the fish bypass system.

Sonar studies determined that fish generally travel in the upper 60 feet of the river. The prototype was designed to use natural and turbine-induced surface currents in the upper 60 feet of the flow to give fish an alternative to diving into the turbine intakes -- entering the bypass system instead. Attractive features of this concept include the minimal volume of flow that's lost, minimizing power losses, as well as the relatively low installation cost.

Flows through the bypass pipe were occasionally diverted to an evaluation facility, where the juvenile fish were examined to identify species and condition. A 24-hour videotaping system counted the number of fish using the bypass system.

To measure the collector's effectiveness in moving fish, a few of the young salmon and steelhead were implanted with electronic tags and released upstream of the hydro project during the spring and summer testing period. The movements of other test fish outfitted with acoustic tags were monitored as they moved through the forebay to determine how they reacted to the surface collector. These studies allowed biologists to view 3-dimensional movement of fish in the forebay as they approached the fish bypass system and dam. This technique was used for this reason first at Rocky Reach.

The prototype surface collection system was modified each year, based upon test results from the previous year. Increased flows into and through the collector, plus improvements to the diversion screen/gatewell collection system in certain units, provided very encouraging study results in 1997. A second entrance was added to the surface collector in 1998, but results in attracting fish were not as good as anticipated. So in 1999, the second entrance to the surface collector was modified to allow biologists to vary the entrance width from a minimum of 22 feet to a maximum of 44 feet. This allowed biologists to analyze how water flows affected, and which water flows were better at attracting fish.

Since 1998, the PUD has been involved in studies that attempt to estimate the survival rates of juvenile salmon and steelhead as they migrate past our hydroelectric projects. It is important that biologists get these estimates to ensure the PUD is meeting its obligations under the Habitat Conservation Plan. The PUD has been in the forefront in developing new technologies to estimate survival.

Studies designed to estimate the survival of downstream migrating juvenile chinook salmon have been conducted at the Rock Island Hydro Project each spring since 1998. These studies, using PIT-tag technology, entailed tagging and releasing hatchery chinook salmon in the tailraces of both Rocky Reach and Rock Island dams.

Since 2002,the District has also conducted studies to evaluate the use of acoustic tag technology in estimating fish survival. These studies involved surgically tagging and releasing hatchery chinook salmon in the tailrace of Rocky Reach Dam. The results of this study were encouraging; detection rates were high, and the operational life of the tags was sufficient to estimate survival using acoustic tags in future years.

A fish ladder was placed at the Rocky Reach Hydro Project when the dam was built in 1962. The ladder consists of a series of 100 pools of falling water, each one foot above the other. Adult fish heading upstream are attracted to the ladder by a collection system with entrances located at the base of the spillway, the center dam, and along the downstream face of the powerhouse. Fish ladders at both hydro projects are well used by adult salmon and steelhead migrating upriver. Studies of upriver migration confirm that our hydro projects do not delay the return trip of adult salmon to their spawning grounds.

The District is in the midst of a major upgrade of the powerhouse. Starting in 1995, the District installed new adjustable-blade turbine runners on all 11 generating units. The District is also rehabilitating generators on all the units. The work will improve the efficiency and reliability of the hydro plant. The end result will be more power generation, higher revenues and lower maintenance costs. In addition, the new turbine runners are "fish friendly," designed to reduce juvenile salmon and steelhead mortality.

The Rocky Reach site has long been recognized for its hydroelectric potential. The U.S. Army Corps of Engineers first considered the site in its 1934 "308 Report." In the 1950s, the site became the focus of extensive studies by the PUD. Geological contour maps were studied, construction costs were estimated, and lengthy computations on such things as the forces and stresses a dam would have on the surrounding area were made.

The original site selected for the Rocky Reach Project by the U.S. Army Corps of Engineers was about one mile upriver from where the dam is today. The present site was found to have superior rock for anchoring the dam, and the river channel is narrower at that location.

Rocky Reach Dam is constructed on metamorphic bedrock formed millions of years ago through compaction of sedimentary materials under extreme pressures and temperatures. The rock provides a very stable foundation for the structure, which meets or exceeds all Federal Energy Regulatory Commission engineering safety and stability criteria. Examples of the bedrock are displayed at the Project's Visitor Center.

The watershed lies east of the Cascade Mountains and west of the Rocky Mountains, consisting of parts of Washington, Idaho, Montana, and British Columbia. The watershed encompasses about 90,000 square miles.

The regulated flow of the Columbia River at the Rocky Reach Project varies on an average annual basis between 40,000 cubic feet per second (cfs) and 220,000 cfs The average annual flow over the past 30 years has been 115,000 cfs That's enough flow to cover a standard-size football field with water 144 feet deep in just one minute. The maximum and minimum recorded natural flows are 530,000 cfs on June 10, 1961, and 25,000 cfs on November 11, 1974. The largest known flood happened on June 7, 1894, with an estimated peak streamflow of 800,000 cfs in the Wenatchee reach of the Columbia River.

Lake Entiat, the Rocky Reach Project reservoir, extends upriver about 43 miles and has a surface area of some 98,000 acres. The reservoir contains 35,000 acre feet of usable storage with a 4-foot drawdown. The average annual minimum water temperature of 37 degrees Fahrenheit normally occurs in February. The average annual maximum water temperature of 65 degrees Fahrenheit usually occurs in August and September.

The Rocky Reach Project was developed over a period of about 15 years. Construction of the dam and original powerhouse with seven generating units began in 1956 for the purpose of power production and flood control. The addition of four more units began in 1969 after ratification of the Columbia River Treaty between the United States and Canada. The additional units were installed primarily to make use of stored water released from reservoirs in Canada and the Libby Dam reservoir in Montana.

The District received a preliminary permit for the Project from the Federal Power Commission (FPC) on August 10, 1954. An application to construct and operate the dam was filed with the same agency on January 13, 1956. The Federal Power Commission issued a license to build the Project six months later, on July 12, 1956. Construction of the dam and original powerhouse began on October 2, 1956 under the supervision of the District's engineering design firm, Stone and Webster Engineering Corporation. The immediate task was the installation of cofferdams to seal off the area designated for the spillway from the river flow during low water.

Following spillway construction, the powerhouse was built. A total of 3.3 million cubic yards of dirt and rock were moved during the five-year initial construction. Employment peaked at 2,184 in July 1959. The initial seven generating units were placed in commercial operation on November 1, 1961, six months ahead of schedule. On September 1, 1966, the District filed an application with the Federal Power Commission to amend the Project License to add four generating units. The FPC issued the license amendment May 23, 1968. The second phase of construction began April 22, 1969, and was completed December 1, 1971. The expansion work increased the power plant's generating capability by 60%, from 815,000 kilowatts to 1.287 million kilowatts.

The Project was financed through the sale of revenue bonds. A revenue bond is a pledge of future revenues generated by the project to repay debt. No tax money was used. The original project, which cost $273.1 million, was financed with a $23.1 million bond issue completed in November 1956 to allow for an early construction start. It was followed by a completion bond issue of $250 million in January 1958.

Included in the Project costs were the relocation of a rail line, highways, land acquisition, relocation of the Town of Entiat, and financing. The subsequent powerhouse expansion and addition of four generating units completed in 1971 were financed by a revenue bond issue of $40 million, sold in July 1968.

Repayment of the revenue bonds is guaranteed through power sales contracts between the Chelan County Public Utility District and the purchasers of Rocky Reach power: PacifiCorp, Portland General Electric Company, Puget Sound Energy, Avista Corp., the Aluminum Company of America (ALCOA) which has a plant just south of Wenatchee, and the District's Electric Distribution System. Each of the contracts covers a period extending 50 years after the November 1961 starting date of commercial operation for the initial seven generating units, or until final payment is made on the $273 million in bonds sold for the initial phase of the Project, whichever is longer. The contracts expire in November 2011.

The original Project License was issued July 11, 1957 by the Federal Power Commission. The license expires in 2006. Prior to that, the District will be required to submit an application for renewal.

The generator is the part of the unit where electricity is produced. As water flow turns the turbine blades, hydraulic energy in the form of the weight and pressure (head) of the moving water is converted to mechanical energy. A huge steel shaft connects the turbine to the generator, where the mechanical energy is converted to electrical energy.

The hydraulic turbines consist of huge water wheels that resemble ship propellers. They are turned by the water flow and connected to the electricity-producing generators by large steel shafts. All 11 units at the Rocky Reach Project are equipped with adjustable blade turbines. Their design allows the turbines to maintain maximum operating capacity and efficiency despite variations in the river flow and generator output.


The crest of the reservoir can be regulated by 12 spillway gates, which open individually and allow water to pass through separate spillway bays. The gates pass water seasonally that is surplus to power generation needs, or as required for assisting fish in their downstream migration.

Power from the Rocky Reach Project is delivered to the District's Distribution System at 115,000 volts. Other 230,000-volt transmission lines deliver energy to the Project's power purchasers. Power also flows into the regional grid of the Bonneville Power Administration.