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Rathdrum Prairie Project History (51 KB) (pdf)
General Description| Plan| Development| Benefits

General Description

The Rathdrum Prairie Project area extends about 12 miles north and 13 miles west of Coeur d'Alene in the panhandle of Idaho. The initial project consisted of the Post Falls, Hayden Lake, and East Greenacres Units, totaling about 10,200 acres of irrigable land. However, in 1991, the landowners within the Post Falls Unit petitioned for dissolution of the operating entity, the Post Falls Irrigation District. By 1995, with approval of the Bureau of Reclamation, dissolution activities were completed. Currently there are about 7,000 irrigable acres in the Rathdrum Prairie Project.

Major facilities of the Post Falls Unit consisted of a pumping plant, 3,000 feet of discharge pipe, 9 miles of canal, and 20 miles of laterals.

Hayden Lake facilities consisted of a pumping plant, 2 miles of 27-inch-diameter discharge pipe, a 10,026-cubic foot storage tank, and a pipe distribution system. However, the Hayden Lake Irrigation District has since converted to a groundwater supply.

Primary facilities of the East Greenacres Unit include 14 wells in 3 well complexes, a 43,446 cubic-foot regulating reservoir, and a pipe distribution system.

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The Post Falls Pumping Plant had two pumps, each with a capacity of 30 cubic feet per second. Water was pumped from the Spokane River through a 3,000-foot-long, 42- inch-diameter steel discharge line into the 9-mile-long Main Canal. The distribution system consisted of both open and piped laterals serving 3,200 irrigable acres.

In July 1973, inspection of the Post Falls facilities revealed that the original 3,000-foot wooden discharge line was in imminent danger of failure. Under emergency fund procedures, the line was replaced with steel pipe.

The major facilities and the appurtenant lands of the Post Falls Irrigation District were disposed of as part of the dissolution process.

The Hayden Lake Pumping Plant has two 350-horsepower pumps, each with a capacity of 10 cubic feet per second at 225-foot dynamic head. Water pumped from Hayden Lake at the shoreline plant is conveyed through a 27-inch mortar-linned steel pipe about 2 miles long to a 10,026-cubic-foot (74,000 gallon) regulating tank, elevated 160 feet above ground. Lateral pipe ranging from 4 to 24 inches in diameter distributes water throughout the some 1,600 irrigable acres within the unit. Smaller piping is asbestos cement and larger diameter pipe is steel with mortar lining.

In the early 1980's, the irrigation district initiated efforts to develop groundwater resources. In 1983, a deep well (Lacey Well Site) was developed equipped with a 300-horsepower motor and vertical turbine pump capable of providing 1,800 gallons per minute. This well is interconnected with the main distribution system.

Two additional wells (Dakota Well Site) were completed by the irrigation district in 1990. One well is 415 feet deep with a 300-horsepower motor and vertical turbine pump having the capability to produce 1,800 gallons per minute. The second well is 450 feet deep with a 600-horsepower motor and vertical turbine pump capable of providing 4,200 gallons per minute.

The pumping plant on Hayden Lake has been placed in a standby status with the development of these groundwater resources.

Irrigation and domestic water for the East Green Acres Unit is furnished by ground water from seven 20-inch diameter and seven 16-inch-diameter wells ranging from 230 to 330 feet deep. Pump capacities for 14 pumps at the three well sites range from 0.47 to 8.2 cubic feet per second, and horsepower ratings from 30 to 500 for each unit. Water is pumped to a 43,000-cubic-foot underground concrete regulating reservoir and carried from the reservoir through a buried pressure pipe ranging from 6 to 36 inches in diameter. The 6- to 24-inch-diameter pipe is asbestos-cement; all pipe over 24 inches is pretensioned concrete cylinder. This multipurpose pipeline system was constructed by the Bureau of Reclamation for year-round use. It was built to serve approximately 5,300 acres of irrigable land with 248 metered domestic turnouts 1-inch in diameter and 357 irrigation turnouts from 1 to 6 inches in diameter. There are now close to 1,000 domestic turnouts and the Bureau of Reclamation has approved the future installation of up to 6,500 domestic turnouts; an increase of 5,500 from the contract maximum. The system replaced a gravity system that originated at Twin Lakes and served 1,420 acres. Existing outlet works at Twin Lakes were modified by installation of two new gates, concrete headwalls, and electric gate actuators with semiautomatic flood controls.

Operating Agencies

The Post Falls Irrigation District assumed the obligation of operation and maintenance of the Post Falls Unit at the beginning of the 1949 irrigation season. The contractual obligation to the United States has been fully repaid. In 1991, faced with a substantial increase in operating costs and the need for rehabilitation or reconstruction of the distribution system, the majority of the landowners signed a petition on September 3, 1991, to dissolve the irrigation district, which was approved by the directors and the court. Land interests involving about 285 parcels were conveyed to the adjacent and underlying fee title owners, and the major facilities were disposed of through the General Services Administration. On August 11, 1995, the Bureau of Reclamation assented to the dissolution.

The Hayden Lake Irrigation District retained the operation and maintenance of the Hayden Lake Unit during construction and continues to operate the system.

Operation and maintenance of the East Green Acres Unit was assumed by the East Green Acres Irrigation District on December 31, 1976. Operation and maintenance of Twin Lakes was assumed by Kootenai County in January 1977.

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First efforts to irrigate the Rathdrum Prairie date back to 1889, when three filings for water were made as part of a plan to irrigate about 6,000 acres of the prairie from Hayden, Twin, and Hauser Lakes. The Spokane Valley Irrigation Company and the Valley Improvement Company were formed and surveys were made, but little in the way of construction was accomplished.

One of the first projects built was that of the Interstate Irrigation District, predecessor of the Hayden Lake Irrigation District, which undertook development of 2,000 acres in 1906. The Post Falls Irrigation District was organized about 1910, and four other small systems Avondale, Dalton Gardens, East Green acres, and East Farms were built about the same time. The East Farms area, straddling the Idaho and Washington boundary, is a private irrigation development related to the Spokane Valley Farms Canal Company. The other systems are operated by irrigation districts.


Originally, the Post Falls Irrigation District obtained its water supply from Hayden Lake. A canal 3,300 feet long conducted the water by gravity to a pumping plant, where it was lifted sufficiently to flow to the farms through a pipe distribution system. However, in 1921, the water level of the lake fell below the elevation of the outlet ditch, so that pumping from the lake into the canal was necessary to get water to the main pumping plant.

Financial and water supply difficulties were experienced for many years and the irrigated area shrank to less than 1,000 acres. In 1940, bonded debt and delinquent interest were retired through agreement with bondholders by a token payment. Nevertheless, continuing water supply difficulties and deterioration of the system finally forced abandonment of irrigation.

By 1946, deterioration of the 8,600-foot-long wooden discharge pipe in the Hayden Lake Irrigation District threatened to prevent further operation. The Bureau of Reclamation, after an investigation made at the request of local interests, recommended rehabilitation of this main supply line.

Because of the deteriorated condition of the pumping plant and the low-pressure pipe distribution system, Reclamation made an investigation in 1955-1956 to determine the best plan and estimated cost for complete rehabilitation of the project, which resulted in authorization of the work, to serve 1,425 irrigable acres.

East Greenacres Irrigation District was formally organized in about 1910 after its inception around 1905. The area originally planned was nearly 3,000 acres, but was later reduced to 1,500 acres. A changing economy, the inadequate water supply system originating at Twin Lakes, and costly maintenance of a water conveyance and distribution system with extremely high water losses were all instrumental in bringing about investigations to improve the project. Studies by the Bureau of Reclamation began in 1958, but were halted in 1960 by litigation between the Lakeshore Owners Association, interested in using the lake for recreation, and the Irrigation District regarding operating levels of Twin Lakes. Following settlement, project investigation was resumed in 1963. At a public meeting in February 1964, potential water users voted almost unanimously in favor of the project plan. Feasibility was documented in a report dated May 1966 that recommended a groundwater supply serving both domestic and irrigation requirements for some 5,300 acres through a closed pipe pressure system.


Finding of feasibility for the Post Falls Unit was made by the Secretary of the Interior on December 24, 1943, and approved by the President on January 29, 1944, under the terms of the Water Conservation and Utilization Act of August 11, 1939 (535 Stat. 1418, Public Law 76-398) as amended. Replacement of the wooden discharge line was authorized by the 1974 Public Works Appropriation Act 1974, dated August 16, 1973 (87 Stat. 318, Public Law 93-97).

For the Hayden Lake Unit, finding of feasibility and authorization was made by the Secretary on June 9, 1947, under the provisions of the Reclamation Project Act of August 4, 1939 (53 Stat. 1187, Public Law 76-260). Emergency rehabilitation was authorized under Interior Department Appropriation Act, 1948 (61 Stat. 473), by the First Deficiency Appropriation Act of May 10, 1948 (62 Stat. 221). Later, rehabilitation of the district works was authorized by Public Works Appropriation Act, 1957, approved July 2, 1956 (70 Stat. 474, Public Law 84-641). Further emergency pipe rehabilitation was authorized by the Act of September 22, 1961 (75 Stat. 588, Public Law 87-289).

East Greenacres Unit was authorized by the Act of June 23, 1970 (84 Stat. 319, Public Law 91-286).

The purpose of the Post Falls Unit was irrigation. The purpose of the Hayden Lake Unit is irrigation. The purposes of the East Greenacres Unit are irrigation, municipal and industrial water supply, conservation and development of fish and wildlife resources, and enhancement of recreation.


Instead of pumping water from Hayden Lake for the Post Falls Unit, a plant was installed to pump from the Spokane River at a point much closer to the project lands. This reconstruction, performed in 1945, made the Post Falls system the first unit of the Rathdrum Prairie Project. The 3,000-foot wooden discharge line was replaced with a steel pipeline. Construction work began in the fall of 1973 and was completed in the spring of 1974.

Emergency repairs were made to the main supply line of the Hayden Lake Unit by the Bureau of Reclamation from May 1948 to April 1949. Major rehabilitation of the project, authorized in 1956, was completed in 1958. Emergency pipe rehabilitation work began in 1962 and was completed in 1963.

Construction on the East Greenacres Unit began in 1972 and was completed in 1976.

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Although fruit production was the major enterprise during the early years of the Post Falls and Hayden Lake Units, major crops in all three units are grain, hay, pasture, and seed (grass and potatoes). Many of the farm units are operated on a part-time basis and are used to produce food for the family or as rural homesites.

Municipal and Industrial

Domestic water service on the East Greenacres Unit is available through the multipurpose pipeline system to the area within the boundaries of the irrigation district. The water supply is sufficient to provide additional domestic service.


Modification of the outlet works at Twin Lakes stabilized the water level, enhanced the recreation areas around the lake, and improved fish and wildlife habitat.

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Last updated: May 16, 2011