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Tualatin Project History (58 KB) (pdf)
General Description| Plan| Development| Benefits
General Description

The Tualatin Project area lies primarily in Washington County in the northwest part of the Willamette Basin, west of and adjacent to the city of Portland, Oregon. Some 17,000 acres of land are furnished irrigation water. Several communities and an industrial corporation are furnished untreated water for municipal and industrial use, and for quality control purposes. Fish and wildlife enhancement, recreation, and flood control are also important project functions.

Principal features include Scoggins Dam, Henry Hagg Lake, Patton Valley Pumping Plant, Spring Hill Pumping Plant, booster pumping plants, and piped lateral distribution systems.

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Construction of Scoggins Dam on Scoggins Creek and the formation of Henry Hagg Lake provided storage for water to supplement the natural streamflow of the Tualatin River and help meet the increasing water requirements of the area.

The 17,000 acres of irrigable land are located in an area about 15 miles wide and 17 miles long, west of the metropolitan area of Portland. The communities that receive water service are also in the area immediately west of Portland. Water stored in Henry Hagg Lake is released for normal river flow and for all project functions by the outlet tunnel and spillway outlet channel into Scoggins Creek downstream from the dam.

Facility Descriptions

Scoggins Dam
Scoggins Dam is a 151-foot-high zoned earthfill structure that is 2,700 feet long at the crest and contains 4 million cubic yards of material. The upstream side of the dam is faced with rock riprap for protection against wave action; the downstream side is faced with topsoil and planted with grass. Total capacity of Henry Hagg Lake is 59,910 acre-feet (active 53,600 acre-feet).

As part of the operation and maintenance modification activities, a drain was installed on the left abutment in 1987.

Patton Valley Pumping Plant and Distribution System

Irrigation water released at the dam is pumped into the distribution system by two downstream pumping plants. Patton Valley Pumping Plant was constructed on the right bank of Scoggins Creek about 2.5 miles downstream from the dam. This is an outdoor plant with five vertical shaft turbine pumps having a combined capacity of 38.7 cubic feet per second. A traveling water screen is provided to prevent loss of fish into the pump sump. Water from the five pumping units is delivered a short distance to a 19,118 cubic-foot (140,000 gallons) capacity steel regulating tank by a 30-inch outside diameter steel discharge line. Some 3.5 miles of buried, gravity-fed pipeline serve about 1,900 acres of land.

The main pipeline consists of over 6,000 feet of 30-inch-diameter reinforced plastic mortar pipe. The remainder of the Patton Valley distribution system is asbestos-cement pipe ranging in size from 21 to 10 inches in diameter.

Spring Hill Pumping Plant and Distribution System

The Spring Hill Pumping Plant, a cooperative venture between the Bureau of Reclamation and the city of Hillsboro, is located on the right bank of the Tualatin River about 9 miles downstream from the dam and 3 miles south of Forest Grove, Oregon. Nine irrigation pumps with a combined capacity of 148.2 cubic feet per second deliver water through a 60 inch diameter prestressed concrete cylinder pipe discharge line to a 84,900 cubic foot (640,000 gallons) capacity buried concrete regulating tank. The 82.5 mile long buried pressure pipeline distribution system ranges in size from 54 to 6 inches in diameter and serves 10,300 acres at the rate of 0.014 cubic feet per second for each acre at a total dynamic head of 127 feet. About 65 miles are asbestos-cement pipe, and the remaining 17.5 miles are reinforced concrete pipe. In addition to the service provided by the Spring Hill and Patton Valley Pumping Plants, 4,800 acres are served by direct pumping of released storage water from Scoggins Creek and the Tualatin River.

The city of Hillsboro presently owns and operates three pumping units installed in the Spring Hill Pumping Plant, with a combined capacity of 32.2 cubic feet per second, that supplies water to itself and the cities of Beaverton and Forest Grove. There is space in the pumping plant for an additional unit to be installed as the requirement for more municipal water develops.

Operating Agencies

Scoggins Dam, Henry Hagg Lake, and related recreation facilities were initially operated and maintained by the Bureau of Reclamation. However, by agreement of August 16, 1983, between the Tualatin Valley Irrigation District and the Bureau of Reclamation, responsibility for the operation and maintenance of Scoggins Dam was transferred to the district effective September 15, 1983. Operation and maintenance of the recreation facilities at Henry Hagg Lake were transferred to Washington County effective November 15, 1973.

The Patton Valley and Spring Hill Pumping Plants and related irrigation facilities are operated and maintained by the Tualatin Valley Irrigation District.

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The project area was known as `Twality Plains` in the pioneer era and was one of the earliest farming settlements in Oregon. Agriculture developed quickly because there were numerous open areas that permitted cultivation without the expense and labor of clearing timber stands, and also because of the fertile soils in the Tualatin Valley. As the population increased, timbered tracts were cleared and more land came under cultivation. Hay, grain, and livestock production were the basis for the early agricultural economy and are still important in the economy of the area. From a small start in 1930, irrigation increased substantially; by the late 1950s, only about 6,000 acres in the Tualatin Basin were inadequately irrigated.


Flood and drainage problems have been a source of concern since early settlement. During 1935-1941, studies made by the Corps of Engineers centered around flood control storage and river channel improvement. Local interests were opposed to some features of the plan, such as straightening the river channel, and felt there was inadequate provision for irrigation storage in the proposed flood control reservoirs.

Studies of the Tualatin Project, as reported in the Bureau of Reclamation`s interim report of July 1948, considered a plan for providing irrigation and drainage to 46,000 acres of potentially irrigable lands, flood control for low-lying lands adjacent to the streams, and a municipal water supply for the towns of the project area. In 1951, local residents held a series of meetings to formulate an opinion on the type of irrigation development best suited to the needs of the area. Both the Corps of Engineers and the Bureau of Reclamation cooperated in a study to provide basic data on present and long-range coordinated development.

Storage at the Scoggins Reservoir site was analyzed in Reclamation`s report of November 1956, which gave consideration to irrigating 31,000 acres of potentially irrigable land and providing 4,500 acre-feet of supplemental municipal and industrial water for the local communities. Upon review of this report, it became apparent that there was a greater need for municipal and industrial water than originally anticipated and some of the owners of potentially irrigable lands were not sufficiently interested in the development plan to proceed further. In May 1963, a feasibility report was issued that proposed irrigation water for 17,000 acres of land, 14,000 acre-feet of municipal and industrial water, and water for fish and wildlife, recreation, quality control, and flood control benefits. On the basis of this plan, the project was authorized.


Construction of the Tualatin Project was authorized by the Congress by the Act of September 20, 1966 (80 Stat. 822, Public Law 89-596). Irrigation, municipal and industrial water supply, flood control, recreation, the conservation and development of fish and wildlife resources, and water quality are project purposes. The latter was approved for inclusion as a project purpose for dilution water for public health considerations (Commissioner of Reclamation on March 7, 1969).


Construction of project facilities began in 1972 and was completed in 1978.

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Increased agricultural production from 17,000 acres has been obtained by making a dependable water supply available throughout the growing season, especially during the late summer period. Production of a wide variety of crops such as grains, strawberries, blueberries, nursery stock, orchard crops, seed crops, pasture, hay, and special crops such as beans and crimson clover.

Municipal and Industrial

The project provides 14,000 acre-feet of water for supplemental municipal and industrial purposes for four communities and an industrial corporation in one of the fastest growing areas of Oregon. In addition, 16,900 acre-feet of water are made available under an agreement with Clean Water Services formerly known as Unified Sewerage Agency of Washington County to improve the water quality of the Tualatin River by scheduled releases of water in the summer when natural flows are low.

Recreation and Fish and Wildlife

The Scoggins Dam and Henry Hagg Lake area encompasses 2,581 acres and provides 1,132 acres of water surface with 11 miles of shoreline at full pool. Located in a forested setting only a short distance from Portland, the area is used both by local residents and visitors from the Willamette Valley. Boat launching and mooring facilities have been constructed and there are large day-use areas provided with picnic tables, shelters, and water and sanitary facilities.

Henry Hagg Lake is stocked annually with rainbow trout for excellent fishing. Minimum flows are provided in Scoggins Creek and a fish trap was built below Scoggins Dam to collect, for hatchery use, the anadromous fish blocked by the dam. Several dead trees were left in the reservoir to attract osprey, and portions of the reservoir area are managed to provide winter range for elk and black-tailed deer.

Flood Control

The gated spillway at Scoggins Dam permits effective use of the top 20,300 acre-feet of reservoir space for flood control. Henry Hagg Lake can completely regulate a flood of the size which occurs about once in 50 years at the damsite. This regulation also will provide some significant flood stage reduction at downstream points on the Tualatin River.

The Henry Hagg Lake has 30,000 acre feet of capacity assigned to flood control. The Tualatin Project has provided an accumulated $19,627,000 in flood control benefits from 1950 to 1998.

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Last updated: May 17, 2011