General

The Boise Project furnishes a full irrigation water supply to about 224,000 acres and a supplemental supply to some 173,000 acres under special and Warren Act contracts. The irrigable lands are in southwestern Idaho and eastern Oregon.

Principal facilities include five storage dams (excluding Lucky Peak Dam constructed by the Corps of Engineers and Hubbard Dam a reregulatory facility) which form reservoirs with a total capacity of 1,793,600 acre-feet (active 1,663,200 acre-feet), two diversion dams, three powerplants with a combined capacity of 50,200 kilowatts, seven pumping plants, canals, laterals, and drains.

To facilitate organization of the administrative and operating procedures, the irrigable project lands are divided into the Arrowrock and Payette Divisions. Some of the features serve only one division; other features serve both divisions as well as other nearby projects.

History

The first right to divert water from the Boise River for irrigation purposes was granted in 1864. The water irrigated the townsite of Boise and supplied Fort Boise. Agricultural activity in the Boise and Payette Valleys started in the early 1880`s when settlers began filing on desert lands under private irrigation enterprises. By 1900, about 148,000 acres had been placed under irrigation.

Since its first authorization in 1905, the Boise Project has expanded in accordance with an orderly program of development that has included the construction of five major reservoirs, two principal diversion dams, three sizable pumping plants, three powerplants, and related facilities. In addition, several structures that were constructed in the early stages of development have been rehabilitated or repaired to improve operations and extend the life of the facilities.

Investigations
Diversion from the river with simple ditches served to adequately irrigate lands in the vicinity of the river, but development of additional lands at higher elevations proved too difficult and costly to be undertaken by private capital. In response to petitions by local irrigators, the Boise Project was initiated by the Reclamation Service (now Bureau of Reclamation) shortly after the passage of the first Reclamation Act in 1902. Subsequent investigations have resulted in the completion of many structures as need arose.

Authorization
Authorization for construction of the original Boise Project (now the Arrowrock Division) was made on March 27, 1905; the Arrowrock Dam on January 6, 1911; and Black Canyon Diversion Dam on June 26, 1922, all by the Secretary of the Interior under provisions of the Reclamation Act of June 17, 1902 (32 Stat. 388). Deadwood Dam and Reservoir were approved on October 19, 1928, and Payette Division on December 19, 1935, by the President under section 4 of the Act of June 25, 1910 (36 Stat. 836), and subsection B, section 4 of the Act of December 5, 1924 (48 Stat. 701). Anderson Ranch Dam and Reservoir were found feasible and authorized on June 25, 1940, by the Secretary of the Interior under the Reclamation Project Act of 1939 (53 Stat. 1187).

The original authorized purpose of each storage facility of the Boise Project is shown below:

Lucky Peak Dam, constructed by the Corps of Engineers, was authorized for flood control and irrigation purposes.

Plan

The Arrowrock Division provides a full irrigation water supply to some 164,000 irrigable acres, and an additional 112,000 acres are furnished supplemental water. Water for the division is stored in Anderson Ranch Reservoir on the South Fork of the Boise River, in Arrowrock Reservoir on the Boise River, and in Lake Lowell, an offstream reservoir in a natural depression impounded by three low dams. Anderson Ranch Dam is 42 miles upstream of Arrowrock Dam. Boise River Diversion Dam, 16 miles downstream from Arrowrock and 7 miles southeast of the city of Boise, diverts water into the New York Canal, which delivers the water to Arrowrock Division lands.

During the non-irrigation season, the New York Canal carries a portion of the water released from Anderson Ranch and Arrowrock Dams to fill Lake Lowell for use in the division during the irrigation season. There are 5 irrigation districts within the Arrowrock Division receiving a full water supply from the project, and 11 districts receiving a supplemental water supply from the division. Power is produced at Anderson Ranch Dam and at the Boise River Diversion Dam.

Lucky Peak Dam, built by the Corps of Engineers, is about 1 mile upstream of Boise River Diversion Dam and backs water up to Arrowrock Dam. Lucky Peak Reservoir has a total storage capacity of 293,100 acre-feet (active 264,400 acre-feet) and was built for flood control and irrigation purposes. By agreement among the Corps of Engineers, the Boise Project Board of Control, and the Bureau of Reclamation, the Anderson Ranch, Arrowrock, and Lucky Peak storage reservoirs on the Boise River are operated jointly for the benefit of irrigation, power, and flood control. These three reservoirs have a total capacity of 1,058,500 acre-feet (active 959,800 acre-feet).

Lands in the Payette Division receive water from the Payette River and surplus drainage from the Arrowrock Division. There are 60,000 acres receiving a full water supply and 61,000 acres receiving a supplemental supply. Storage features are Deadwood Dam on Deadwood River, a tributary of the South Fork of the Payette River, and Cascade Dam on the North Fork of the Payette River. Water is diverted into the Black Canyon Main Canal (south side) and then into the distribution system. The main canal separates into two supply lines which serve 27,000 acres by gravity flow. About 20 miles below Black Canyon Diversion Dam, a pumping plant lifts water from the main canal into a lateral system serving 26,000 acres. The 7,000-acre Notus Unit of the Payette Division obtains water from two Arrowrock Division drains south of the Boise River near Caldwell. These three acreages are in the Black Canyon Irrigation District.

The 25,000-acre Emmett Irrigation District receives a supplemental water supply partially from the Black Canyon Main Canal but primarily from the North Side Canyon Canal. Both canals divert water from the Payette River at Black Canyon Diversion Dam. Power is produced at Black Canyon Diversion Dam.

Anderson Ranch Dam and Powerplant
Anderson Ranch Dam and Powerplant is a multiple purpose structure that provides benefits of irrigation, power, and flood and silt control. Situated on the South Fork of the Boise River 28 miles northeast of Mountain Home, the dam is 456 feet high, was the world`s highest earthfill dam at the time of its completion in 1950, and has a total storage capacity of 493,200 acre-feet (active 423,200 acre-feet). The power plant had a rated capacity of 27,000 kilowatts with two units installed. These units were uprated in 1986, increasing the capacity to 20,000 kilowatts each for a total of 40,000 kilowatts.

Arrowrock Dam
Arrowrock Dam, on the Boise River, 42 miles downstream of Anderson Ranch Dam and 22 miles upstream from Boise, is a concrete thick-arch structure 350 feet high. When constructed in 1915, the dam was recorded as being the tallest concrete dam in the world. The structure was repaired and raised 5 feet during 1935-1937, increasing its storage by 9,000 acre-feet; total storage capacity 286,600 acre-feet (active 286,600 acre-feet). The original construction involved the use of a rather high proportion of sand cement, and by 1935 the concrete on the downstream face of the structure showed deterioration due to climatic conditions. Repairs included refacing the downstream face and spillway channel. After 85 years of service, the Ensign valves had reached the end of their useful life. The lower set of ten Ensign valves were removed and replaced with clamshell gates between 2001 and 2004. A contract to permanently plug all five sluice gate outlet conduits was completed in January 2011.

A sedimentation survey completed in 1997 estimated the total capacity of Arrowrock Reservoir at 272,200 acre-feet (active 271,700 acre-feet).

The Boise Project Board of Control completed construction of a 15 MW powerplant at Arrowrock Dam in March 2010. The powerplant penstockes tie into two of the existing 66" outlet conduits. The project also updated the transmission line to the dam.

Boise River Diversion Dam and Powerplant
The Boise River Diversion Dam, on the Boise River about 7 miles southeast of Boise, Idaho, is a rubble-concrete, weir-type structure with a hydraulic height of 39 feet. The dam diverts water into the New York Canal which serves distribution laterals and feeds Lake Lowell. A small canal known as the Penitentiary Canal, also originating at the diversion dam, distributes water on the north side of the Boise River to a small area of land east of Boise. The powerplant consists of three 500-kilowatt units that began operation in 1912. Due to the deteriorated condition of the equipment and high operating costs resulting from full-attended operation, the powerplant was placed in ready reserve status in 1982. The plant was reconstructed from 2002 to 2004 and returned to service in June 2004. The nameplate rating for the plant was increased from the original 1500 kW to 3300 kW. The existing double turbine configuration was retained, but refurbished with new materials and technology. Modern generators were installed inside the original generator housings.

Lake Lowell
Lake Lowell, originally known as Deer Flat Reservoir, is an offstream reservoir formed by three earthfill dams enclosing a natural depression southwest of Nampa, Idaho. These three dams are the Upper, Middle (Forest Dam), and Lower Embankments. A fourth embankment, called the East (Roadway Dike) is to protect farmsteads on the eastern end of the reservoir when the reservoir is full. The reservoir is filled primarily during the non-irrigation season by diversions at the Boise River Diversion Dam and conveyance through the New York Canal which discharges into the eastern (upper) end of Lake Lowell.

The Upper Embankment on the north side of the reservoir is 74 feet high and has two outlets; near the right abutment the Deer Flat Nampa Canal (100 cubic feet per second) and near the left abutment the Deer Flat Caldwell Canal (70 cubic feet per second).

The Lower Embankment at the west end of the reservoir is 44 feet high. The Deer Flat Low Line Canal (1,200 cubic feet per second) outlets on the left abutment and the Deer Flat North Canal (70 cubic feet per second) outlets on the right abutment.

The Middle Embankment, which has no outlets, is 16 feet high and helps to close the reservoir near the Lower Embankment. It has been referred to as an emergency spillway; however, no slope protection is provided for this purpose.

Because of safety concerns at the Upper and Lower Embankments, the maximum water level was reduced by 5 feet in 1989 while plans were prepared to address remedial actions. Major modifications were made to the Upper and Lower Embankments from 1991 to 1993. Further, in 1996 an upstream seepage blanket was constructed at the right abutment of the Upper Embankment to address seepage in this area. These activities were accomplished under Reclamation's Safety of Dams Program. A Safety of Dams modification was also performed in 2008-2009. The modifications involved the complete replacement of the Caldwell Canal outlet works structure including the intake tower and access bridge, gate and operator, the entire length of the conduit, and the placement of a circumferential filter around the downstream section of new conduit. In addition, the downstream section of the Nampa Canal outlet works conduit was replaced with a new section of conduit incorporating a downstream circumferential filter.

The original total storage capacity of Lake Lowell was 190,000 acre-feet (active 169,000 acre-feet). A sedimentation survey conducted in 1994, estimated the reservoir's total storage capacity at 173,000 acre-feet (active 159,400 acre-feet).

Hubbard Dam
Hubbard Dam, located about 12 miles southwest of Boise, Idaho, was originally constructed in 1902 by private interests. The Bureau of Reclamation purchased the facility in 1911 as part of the Boise Project. This is an earthfill structure 23 feet high creating a reservoir area of 450 acres with an active capacity of about 4,000 acre-feet. Water is delivered to the reservoir by the New York Canal. The dam and reservoir are operated and maintained by the Boise Project Board of Control as a reregulating facility for irrigation water deliveries in the adjacent area. It also provides emergency short-term storage for dewatering the New York Canal should a failure in the canal occur downstream.

Arrowrock Diversion Canal System
The New York Canal is about 40 miles long and has a diversion capacity of 2,800 cubic feet per second. It consists of the enlarged old New York Canal, a section of new canal, and a part of the channel of Indian Creek. Diversions are made from the New York Canal into various canals such as the Mora Canal and the Deer Flat High Line Canal and into numerous distribution systems. Water delivered by the New York Canal to Lake Lowell is diverted into the four canals outletting the reservoir.

Deadwood Dam
Deadwood Dam is located in west-central Idaho on the Deadwood River about 25 miles above its confluence with the South Fork of the Payette River and about 90 miles above Black Canyon Diversion Dam. The damsite is located in a narrow canyon where the Deadwood River has cut into granite bedrock, approximately 53 miles northeast of Boise, Idaho. The dam lies on the western slope of the Sawtooth Mountains with elevations in the basin varying from 5311 feet by the dam to about 8,696 feet at Price Peak. Deadwood Reservoir is three and one half miles long and covers 3,180 acres. Deadwood Dam is a concrete-arch structure with a structural height of 165 feet and a total capacity of 162,000 acre-feet (active 161,900 acre-feet), providing a regulated flow for the powerplant at Black Canyon Diversion Dam and for irrigation in the Payette Division and Emmett Irrigation District.

Cascade Dam
Cascade Dam, near Cascade, Idaho, on the North Fork on the Payette River, is a zoned earthfill structure 785 across the crest. The initial total storage capacity was 703,200 acre-feet (active 653,200 acre-feet). The spillway is located on the right abutment of the dam. The invert is 45 feet wide at the crest under the radial gates and about 330 feet long excluding the open cut channel to the reservoir. The design capacity is 12,500 cubic feet per second with the water surface at elevation 4828.0 feet. Two 21-foot wide by 20-foot high radial gates are installed on the crest of the spillway to provide means for regulating the discharge of water over the spillway and to provide protection for the dam in the event of a sudden rise in reservoir water level. A sedimentation survey completed in 1995 at Lake Cascade estimated the total capacity at 693,100 acre-feet (active 646,500 acre-feet).

Black Canyon Diversion Dam
Black Canyon Diversion Dam, on the Payette River near Emmett, Idaho, is a concrete gravity type dam with an ogee overflow spillway. The dam has a structural height of 183 feet and serves to divert water to the Payette Division through Black Canyon Canal. The original capacity was 44,700 acre-feet but heavy siltation has reduced the capacity. At full pool there is now a volume of 29,600 acre-feet. Water is diverted at Black Canyon Diversion Dam by gravity into the Black Canyon Main Canal on the south side of the Payette River and by two direct connected turbine-driven pumps, located in the powerhouse, to serve the Emmett Irrigation District Canal on the north side of the river. The two unit powerplant had an initial total capacity of 8,000 kilowatts. The unit's electrical components were upgraded to 5,100 kilowatts each in 1995 to provide the capability of generating 10,200 kilowatts with further upgrade of the turbines. Present generating capacity is however limited to about 10,000 kilowatts. The plant supplies power to the Southern Idaho Federal Power System for Bureau of Reclamation project uses and for non-project purposes.

In 1988, a six-inch raise in Black Canyon Reservoir water surface was implemented by modifying the spillway drumgate and the radial gate at the Black Canyon Main Canal headworks. This was done to improve regulation of irrigation diversions from Black Canyon Reservoir to the Black Canyon Main Canal and to conserve the amount of stored water released from upstream reservoirs to meet fluctuating irrigation demands.

Pumping Plants
The pumping plants are: (1) Black Canyon at the Black Canyon Diversion Dam; (2) `C` Line Canal at station 1064 on the Black Canyon Main Canal; and (3) Willow Creek at station 1111 on `C` Line Canal East, about 4 miles northeast of Middleton, Idaho. There are also four small relift pumping plants.

The Black Canyon Pumping Plant contains two pumps directly connected to turbines; the `C` Line Canal plant has five pumps; and Willow Creek has two motor-driven pumps lifting water from the `C` Line Canal East.

Payette Diversion Canal System
The Black Canyon Main Canal is 29 miles long and extends from the Black Canyon Diversion Dam south and west along the Payette River. The canal has a diversion capacity of 1,300 cubic feet per second.

The `C` Line Canal East, with diversion capacity of 469 cubic feet per second, begins at `C` Line Canal Pumping Plant on the Black Canyon Main Canal and is 21 miles long. The `C` Line Canal West branches from the `C` Line Canal East, extends 24 miles, and has a diversion capacity of 60 cubic feet per second.

The `A` Line and `D` Line Canals begin near the terminus of the Black Canyon Main Canal. The `A` Line Canal is 33 miles long and has a diversion capacity of 226 cubic feet per second; the `D` Line Canal, 39 miles long, has a diversion capacity of 254 cubic feet per second.

Non Federal Powerplants
Idaho Power Company constructed a two unit 12,800 kilowatt powerplant at Cascade Dam in 1983 under a Federal Energy Regulatory Commission license. The hydraulic capacity of the powerplant is approximately 2,300 cfs at elevation 4828.0.

In 1988, four of the five irrigation districts of the Boise Project Board of Control, under a Federal Energy Regulatory Commission license, completed construction of a 3 unit powerplant at Lucky Peak Dam which includes one 11,250 kilowatt unit and two 45,000 kilowatt units for a total capacity of 101,250 kilowatts. Generation is under contract with the Seattle Light Company.

The Boise Project Board of Control completed construction of a two unit 15,000 kilowatt powerplant at Arrowrock Dam in 2010. The powerplant penstocks tie into two of the existing 66-inch outlet conduits. The project also updated the transmission line to the dam.

Operating Agencies
The operating organization for the Arrowrock Division of the project is the Boise Project Board of Control, which was formed in 1926 by contracts between the Bureau of Reclamation and the five irrigation districts representing the water users that make up the project. These irrigation districts are Big Bend, Boise-Kuna, Nampa & Meridian, New York, and Wilder. Each of the irrigation districts elect representatives in proportion to their acreage served by the district, and the Board of Control selects a manager to administer day-to-day operation and maintenance.

The Bureau of Reclamation operated the project until April 1, 1926, when operation was turned over to the newly organized irrigation districts under the Act of December 5, 1924, known as the Fact Finders` Law. However, Reclamation retained the operation and maintenance of certain parts of the system, referred to as the `reserved works.` In 1990, operation and maintenance of the first 1/2 mile of the New York Canal was transferred to the Board of Control. Operation and maintenance of the Boise River Diversion Dam and the headworks to the New York Canal were transferred to the Board of Control in 1992.

Arrowrock Dam and Reservoir, Anderson Ranch Dam, Reservoir, and Powerplant, and the Boise River Diversion Dam Powerplant continue to be `reserved works` operated and maintained by the Bureau of Reclamation. Lucky Peak Dam and Reservoir is operated by the Corps of Engineers.

In the Payette Division, the Bureau of Reclamation operates and maintains Deadwood and Cascade Reservoirs, and Black Canyon Diversion Dam and Powerplant. All irrigation carriage and distribution systems are operated by the water users.

Anderson Ranch Dam and Powerplant, Boise River Diversion Powerplant, Cascade Dam and Deadwood Dam can be remotely operated by the Bureau of Reclamation from its control center at Black Canyon Diversion Dam. Automation of Arrowrock Dam is underway.

Other

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Overview

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Construction

The 276,000-acre Arrowrock Division serves that portion of the Boise Project lands situated between the Boise and Snake Rivers. Lake Lowell was completed by June 1911; Arrowrock Dam and Reservoir commenced storing water in 1915; Boise River Diversion Dam was completed by October 10, 1908, and Anderson Ranch Dam was completed in 1950. The powerplant at Boise River Diversion Dam, built originally to supply power for construction of Arrowrock Dam, was placed in operation in 1912. As the reservoirs were built, a system of canals, laterals, and drains was constructed.

The 121,000-acre Payette Division includes lands between the Payette and Boise Rivers and lands north of the Payette River in the Emmett Irrigation District which are irrigated from the Payette River and from drains operated within the Arrowrock Division. Black Canyon Diversion Dam on the Payette River, which heads the gravity distribution system, was completed in 1924; Deadwood Dam and Reservoir on the Deadwood River in 1931; and Cascade Dam and Lake Cascade on the North Fork of the Payette River in 1948. The gravity distribution system was constructed during 1936-1940. Supplementing this system, a combination pump-gravity canal, designated the `C` Line, was completed in 1948.